首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5791篇
  免费   133篇
各国政治   237篇
工人农民   228篇
世界政治   460篇
外交国际关系   208篇
法律   3635篇
中国政治   50篇
政治理论   1087篇
综合类   19篇
  2021年   42篇
  2020年   69篇
  2019年   106篇
  2018年   135篇
  2017年   118篇
  2016年   120篇
  2015年   70篇
  2014年   123篇
  2013年   597篇
  2012年   142篇
  2011年   152篇
  2010年   128篇
  2009年   143篇
  2008年   171篇
  2007年   158篇
  2006年   144篇
  2005年   130篇
  2004年   156篇
  2003年   125篇
  2002年   101篇
  2001年   310篇
  2000年   277篇
  1999年   193篇
  1998年   79篇
  1997年   80篇
  1996年   53篇
  1995年   56篇
  1994年   48篇
  1993年   38篇
  1992年   121篇
  1991年   139篇
  1990年   131篇
  1989年   127篇
  1988年   113篇
  1987年   125篇
  1986年   101篇
  1985年   96篇
  1984年   96篇
  1983年   83篇
  1982年   58篇
  1981年   73篇
  1980年   34篇
  1979年   74篇
  1978年   43篇
  1975年   37篇
  1974年   49篇
  1973年   54篇
  1972年   39篇
  1971年   34篇
  1970年   29篇
排序方式: 共有5924条查询结果,搜索用时 15 毫秒
901.
Abstract: This study provides forensic search teams with systematic geophysical monitoring data over simulated clandestine graves for comparison to active cases. Simulated “wrapped” and “naked” burials were created. Multigeophysical surveys were collected over a 3‐year monitoring period. Bulk ground resistivity, electrical resistivity imaging, multifrequency ground‐penetrating radar (GPR), and grave and background “soil‐water” conductivity data were collected. Resistivity surveys revealed the naked burial had consistently low‐resistivity anomalies, whereas the wrapped burial had small, varying high‐resistivity anomalies. GPR 110‐ to 900‐MHz frequency surveys showed the wrapped burial could be detected throughout, with the “naked” burial mostly resolved. Two hundred and twenty‐five megahertz frequency GPR data were optimal. “Soil‐water” analyses showed rapidly increasing (year 1), slowly increasing (year 2), and decreasing (year 3) conductivity values. Results suggest resistivity and GPR surveys should be collected if target “wrapping” is unknown, with winter to spring surveys optimal. Resistivity surveys should be collected in clay‐rich soils.  相似文献   
902.
Anomie is a highly prominent theoretical construct in macro-social, particularly cross-national, criminological inquiry. Yet despite its prominence, it has proven to be quite elusive with regard to its measurement and, hence, making it nearly impossible to test theoretical hypotheses regarding its predictive efficacy. Although the concept, whether derived from Merton's classic conceptualization or from its current incarnation in the form of institutional anomie as developed by Messner and Rosenfeld, is multidimensional and complex in its theoretical structure, most researchers have attempted to operationalize it through simple, single-item, often surrogate/proxy measures. The present research note attempts to develop a measure that is more consistent with its multidimensional and complex nature. This more complex operationalization is then examined with regard to its efficacy at predicting cross-national levels of both homicide and theft. Our results suggest that that this new operationalization has considerable predictive efficacy, accounting for approximately one third of the variation in the cross-national level of both homicide and theft.  相似文献   
903.
The easily available "legal highs", which are products containing psychoactive substances, such as cathinones, piperazines and synthetic cannabinoids, are abused by adolescents in Poland and in the world as alternatives to classic drugs, such as amphetamines or marijuana. The majority of these potentially dangerous substances are still legal and they are associated with a risk of severe poisoning or even death, and provide new challenges in clinical and forensic toxicological practice. Investigations in the field of "designer drugs" may be well illustrated by the case of a suicide of a 21-year old male who ingested a specified dose of a preparation called "Amphi-bi-a" that contains bk-MBDB, chemically 2-methylamino-1-(3,4-methylenedioxyphenyl) butan-1-one, which belongs to the cathinone group, as a synthetic euphoric empathogen and psychoactive stimulant that is chemically similar to MDMA. It is one of more common components of "legal highs" examined in Poland and other countries. The documentation of the case includes a clinical assessment of the patient's health status performed during his almost 4-h hospitalization before death, autopsy and histological examinations supported by toxicological findings revealing bk-MBDB at extremely high concentrations (at 20mg/l in the blood and 33mg/kg in the liver); hence, this body of evidence contributes to knowledge in the field of "designer drugs". Inventions of designers of new psychoactive xenobiotics, which are much in demand, especially in view of the dynamic Internet marketing, which drums up narcobusiness, must be balanced by a national strategy developed by medical, legal and educational circles in the modern civilized world in order to prevent the spreading of the phenomenon.  相似文献   
904.
Mephedrone is a synthetic derivative of cathinone which is becoming more common on the recreational drug market. Several intoxications following mephedrone abuse have been reported though published papers have focused essentially on analytical approaches for biological fluids and only one has involved a hair sample. After the development and validation of a new method, the first series of positive results for mephedrone in hair specimens is reported here. After decontamination of the hair strand in methylene chloride, hair segments were cut into small pieces with scissors, weighed and incubated overnight in Soerensen buffer pH 7.0 in the presence of deuterated 3,4-methylenedioxymethamphetamine (MDMA) at 40°C. The incubation medium was extracted using ethyl acetate after alkalinisation with 1N sodium hydroxide (NaOH). Before injection, the dry extract was derivatized using a mixture of heptafluorobutyric anhydride/ethyl acetate (100:50, v/v), evaporated and dissolved in ethyl acetate (25μl). After introduction of 1μl of the extract onto a splitless injector, chromatographic separation was achieved on a HP 6890 gas chromatograph equipped with a 5-MS capillary column. Detection was achieved in single ion monitoring mode (m/z 254-119-210 for mephedrone, m/z 258-213 for MDMA-d5) using a 5973 MSD operating in electron impact mode. Sixty-seven hair specimens were tested for mephedrone. Thirteen of them were found positive for mephedrone with concentrations ranging from 0.2 to 313.2ng/mg with a mean concentration of 26.8ng/mg. It was difficult to compare our findings due to a lack of reference data, nevertheless mephedrone seems well incorporated into hair (concentrations in the ng/mg range) like other stimulant drugs such as amphetamines or cocaine. The aim of this work was to develop a specific and accurate method for mephedrone analysis in hair specimens and its application to a large number of samples (n=67). The developed analytical method appears sensitive enough to reveal occasional to regular use of mephedrone.  相似文献   
905.
A 2010 UK police search for a clandestine burial highlighted the need for more information and quantitative data to aid coastal beach searches. This study aimed to address this by establishing relevant forensic search methodologies to aid the search for clandestine coastal burial sites, using the North West English coastline as a search area. A set of parameters were established, including criteria such as tidal range, proximity to vehicular access points and distance from inhabited areas, which may inform forensic searches by prioritising likely locations of clandestine burials. Three prioritised coastal locations were subsequently identified: (1) coastal dunes at Formby, (2) coastal dunes and (3) beach foreshore at Southport, all sites part of the Liverpool City Region in the United Kingdom. At all locations, simulated clandestine graves were hand-dug by spades into which a naked adult-sized, metal-jointed fiberglass mannequin was buried at 0.5 m below ground level. Trial geophysical surveys were then undertaken with the aim of identifying the optimal geophysical instrumentation and technique to deploy in such environments. GPR data showed 450 MHz frequency antennae to be optimal, with significantly poor data obtained from the foreshore area due to saline seawater. Electrical resistivity and magnetic susceptibility surveys were successful in coastal environments in target detection (albeit not in non-vegetated sand dunes), with resistivity fixed-offset configurations deemed optimal. The latter survey successes may be due to the recent disturbed 'grave' rather than the target, which itself is of interest in terms of identifying the most recent clandestine burials.  相似文献   
906.
Although proprietary medicines and decoction of processed aconite roots are the most widely used, tincture accounts for the great majority of aconite poisoning cases in China, indicating that it is much more toxic than other formulations. Aconite tincture is often self-prepared at home and raw aconite plants or roots are often used. Even if processed aconite roots were used to make the tincture, the amount of Aconitum alkaloids is highly variable, depending on the adequacy of processing and quality control. Aconitum alkaloids dissolve efficiently in alcohol. For these reasons, tincture contains very high concentrations of Aconitum alkaloids. Despite its high intrinsic toxicity, overdose of aconite tincture by the users has been common. Severe aconite poisoning can be complicated by fatal ventricular tachyarrhythmias and asystole. The public should be repeatedly warned of the danger of taking aconite tincture by mouth.  相似文献   
907.
A collaborative study on Raman spectroscopy and microspectrophotometry (MSP) was carried out by members of the ENFSI (European Network of Forensic Science Institutes) European Fibres Group (EFG) on different dyed cotton fabrics. The detection limits of the two methods were tested on two cotton sets with a dye concentration ranging from 0.5 to 0.005% (w/w). This survey shows that it is possible to detect the presence of dye in fibres with concentrations below that detectable by the traditional methods of light microscopy and microspectrophotometry (MSP). The MSP detection limit for the dyes used in this study was found to be a concentration of 0.5% (w/w). At this concentration, the fibres appear colourless with light microscopy. Raman spectroscopy clearly shows a higher potential to detect concentrations of dyes as low as 0.05% for the yellow dye RY145 and 0.005% for the blue dye RB221. This detection limit was found to depend both on the chemical composition of the dye itself and on the analytical conditions, particularly the laser wavelength. Furthermore, analysis of binary mixtures of dyes showed that while the minor dye was detected at 1.5% (w/w) (30% of the total dye concentration) using microspectrophotometry, it was detected at a level as low as 0.05% (w/w) (10% of the total dye concentration) using Raman spectroscopy. This work also highlights the importance of a flexible Raman instrument equipped with several lasers at different wavelengths for the analysis of dyed fibres. The operator and the set up of the analytical conditions are also of prime importance in order to obtain high quality spectra. Changing the laser wavelength is important to detect different dyes in a mixture.  相似文献   
908.
Serious head and neck injuries are a common finding in fatalities associated with rollover crashes. In some fatal rollover crashes, particularly when ejection occurs, the determination of which occupant was driving at the time of the crash may be uncertain. In the present investigation, we describe the analysis of rollover crash data from the National Automotive Sampling System-Crashworthiness Data System for the years 1997 through 2007 in which we examined the relationship between a serious head and neck injury in an occupant and a specified degree of roof deformation at the occupant's seating position. We found 960 occupants who qualified for the analysis, with 142 deaths among the subjects. Using a ranked composite head and neck injury score (the HNISS) we found a strong relationship between HNISS and the degree of roof crush. As a result of the analysis, we arrived at a predictive model, in which each additional unit increase in HNISS equated to an increased odds of roof crush as follows: for ≥8cm of roof crush compared with <8cm by 4%, for ≥15cm of roof crush compared to <8cm by 6% and for ≥30cm of roof crush compared to <8cm by 11%. We describe two hypothetical scenarios in which the model could be applied to the real world investigation of occupant position in a rollover crash-related fatality.  相似文献   
909.
In this study, we examine citizens?? perceptions of police?Ccommunity relationships in India. More specifically, in this exploratory study, we examine the extent to which factors such as general satisfaction with police services, police professionalism, feeling of safety, and perception of police integrity all explain the public confidence in police?Ccitizen relationships. Those who are generally satisfied with police like to work with police and view police?Ccommunity relationships positively. Further, we find that those who feel police are fair in dealing with citizens, irrespective of social status, and those who feel more safe in their communities are those who are most willing to work with police.  相似文献   
910.
New data show that between 1982 and 2007, in over 60 countries governments were linked to and cooperated with informal armed groups within their own borders. Given the prevalence of these linkages, we ask how such links between governments and informal armed groups influence the risk of repression. We draw on principal-agent arguments to explore how issues of monitoring and control help understanding of the impact of militias on human rights violations. We argue that such informal agents increase accountability problems for the governments, which is likely to worsen human rights conditions for two reasons. First, it is more difficult for governments to control and to train these militias, and they may have private interests in the use of violence. Second, informal armed groups allow governments to shift responsibility and use repression for strategic benefits while evading accountability. Using a global dataset from 1982 to 2007, we show that pro-government militias increase the risk of repression and that the presence of militias also affects the type of violations that we observe.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号