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   22957篇
  免费   1433篇
各国政治   1107篇
工人农民   1002篇
世界政治   1705篇
外交国际关系   969篇
法律   14488篇
中国共产党   2篇
中国政治   146篇
政治理论   4819篇
综合类   152篇
  2023年   112篇
  2021年   137篇
  2020年   524篇
  2019年   579篇
  2018年   716篇
  2017年   760篇
  2016年   834篇
  2015年   612篇
  2014年   688篇
  2013年   2768篇
  2012年   634篇
  2011年   662篇
  2010年   677篇
  2009年   712篇
  2008年   648篇
  2007年   707篇
  2006年   702篇
  2005年   630篇
  2004年   637篇
  2003年   546篇
  2002年   613篇
  2001年   787篇
  2000年   717篇
  1999年   577篇
  1998年   321篇
  1997年   263篇
  1996年   275篇
  1995年   272篇
  1994年   259篇
  1993年   248篇
  1992年   385篇
  1991年   395篇
  1990年   348篇
  1989年   328篇
  1988年   361篇
  1987年   323篇
  1986年   389篇
  1985年   380篇
  1984年   294篇
  1983年   287篇
  1982年   219篇
  1981年   203篇
  1980年   175篇
  1979年   252篇
  1978年   147篇
  1977年   121篇
  1976年   103篇
  1975年   108篇
  1974年   138篇
  1973年   94篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
901.
Methyl nitrite is suggested to cause methemoglobinemia by generating methemoglobin, which may be lethal when the methemoglobin concentration exceeds 70%. However, intoxication with methyl nitrite is seldom reported compared with that with other nitrites. Here, we present an industrial accident involving methyl nitrite inhalation during its synthesis process that resulted in three fatalities and one survivor. The autopsy revealed conspicuous blue-gray discoloration in various parts of the body, including the skin, airway mucosa, vessels, brain, heart, and among other areas. The toxicological tests on the deceased showed methemoglobin concentrations in the blood over the lethal level and increased nitrite ion levels in the blood, gastric contents, liver, and lung tissue compared with those in control samples. The cause of death was determined to be methemoglobinemia-induced hypoxia due to methyl nitrite inhalation. This report provides evidence that in methyl nitrite intoxication, exposure duration has a significant influence on the postmortem changes and likelihood of a fatal outcome may be related to the age of the victim. More attention is required regarding the industrial hazards of this substance.  相似文献   
902.
In 2007, the Bureau of Justice Statistics reported on 2004 data collected from the Census of Medical Examiner and Coroner Offices (CMEC). The CMEC was one of the first comprehensive reports on the state of the medicolegal death investigation system in the United States and included information on administration, expenditure, workload, specialized death investigations, records and evidence retention, and resources. However, the report did not include responses on questions that were related to toxicology such as specimen retention and type of testing. The purpose of this publication is to provide the community with toxicology laboratory-specific responses from nearly 2000 medical examiner and coroner (MEC) offices. Data obtained from a BJS CMEC public use dataset for any remaining information that was not reported in the 2007 BJS report were evaluated specific to the operation of toxicology laboratories within a MEC office or specific to toxicology testing. The CMEC includes information on average operating budget for MEC offices with internal or external toxicology services, budget for toxicology/microbiology services, respondents’ routine uses of toxicology analysis, toxicology specimen retention time, average turnaround times, use of computerized information management systems, and participation in federal data collections. These historical data begin to address the present state of our nation’s toxicology laboratories within the medicolegal death investigation system and their preparedness for the current drug overdose epidemic.  相似文献   
903.
Network-attached storage (NAS) is a system that uses a redundant array of disks (RAID) to create virtual disks comprising multiple disks and provide network services such as FTP, SSH, and WebDAV. Using these services, the NAS's virtual disks store data about individuals or groups, making them a critical analysis target for digital forensics. Well-known storage manufacturers like Seagate, Synology, and NETGEAR use Linux-based software RAID, and they usually support Berkeley RAID (e.g., RAID 0, 1, 5, 6, and 10) as well as self-developed hybrid RAID. Those manufacturers have published data on the introduction and features of hybrid RAID, but there is not enough information to reassemble RAID from a digital forensic perspective. Besides, digital forensic tools (such as EnCase, FTK, X-ways, and RAID Reconstructor) do not support automatic RAID reassembly for hybrid RAID, so research on hybrid RAID reassembly methods is necessary. This paper analyzes the disk array composed of hybrid RAID and explains the layout of disk array, partition layout in hybrid RAID, and hybrid RAID configuration strategy. Furthermore, it suggests parameters that are required for RAID reassembly and then propose a hybrid RAID reassembly procedure using them. Finally, we propose a proof-of-concept tool (Hybrid RAID Reconstructor) that identifies hybrid RAID from disk array and parse RAID parameters.  相似文献   
904.
A 55-year-old man complained of sudden onset of severe neck pain. This was followed by prompt loss of consciousness and death. Autopsy revealed rupture of a saccular aneurysm, which was considered to have resulted from enlargement of the remaining ductal tissue, and was located on the medial aspect of the uppermost portion of the descending aorta. Dense blood extravasation was noted in the posterior mediastinum and extending to the strap muscles of the neck and larynx. Histological examination of the rupture site revealed disappearance of the medial elastic fibers and thickened intima covered with dense fibrous tissue. Spontaneous ductus arteriosus aneurysm in adults is a rare finding, but widespread use of imaging technologies has revealed that it develops more frequently than previously recognized. Fatal complications may occur even when the aneurysm is relatively small. Therefore, pathologists should be aware of this aneurysm as a potential cause of sudden death.  相似文献   
905.
Previous studies suggest cardiovascular pathologists are less accurate than noncardiovascular pathologists (e.g., clinical pathologists) in estimating the degree of coronary artery stenosis. To further investigate the effect of training on accurate estimation of coronary artery stenosis, we designed a study to compare the accuracy of estimates made by forensic pathologists versus medical students. Six forensic pathologists and twelve medical students each independently examined 24 images of coronary artery cross sections and gave an estimate of the degree of stenosis. When comparing all 24 images, the forensic pathologists had a median difference between the estimated percentage of stenosis and actual percentage of stenosis of −12.380 and the medical students had a median difference of −16.50 (p-value of 0.08542). In estimating the percentage of stenosis, training in forensic pathology does not guarantee significantly improved accuracy compared with medical students. Our study showed no consistent statistically significant difference between estimates given by forensic pathologists and by medical students.  相似文献   
906.
This study is the first to examine the background level of male DNA on underpants worn by females in the absence of sexual contact. Here, we examined 103 samples from the inside front of underpants from 85 female volunteers. Samples were examined for the presence of male DNA using NGM SElect and PowerPlex Y23 kits. Only five samples gave a “complete” Y-STR profile, even though 83.5% of our volunteers cohabited with a male. In all cases where a partner reference sample was available, the Y-STR profile matched the cohabiting partner. We have demonstrated that a Y-STR profile is not expected on the inside front of underpants worn by females after social contact alone. The results of this study are informative for evaluating the significance of a Y-STR profile on underpants in cases of alleged sexual assault.  相似文献   
907.
Novel psychoactive substances (NPS) are synthetic drugs that pose serious public health and safety concerns. A multitude of NPS have been identified in the United States, often implicated in forensic investigations. The most common and effective manner for identifying NPS is by use of mass spectrometry and the true utility lies within nontargeted acquisition techniques. During this study, a liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) assay was developed, validated, and implemented for forensic toxicology testing. A SCIEX TripleTOF™ 5600 + with SWATH® acquisition was used. Resulting data were compared against an extensive library database containing more than 800 compounds. The LC-QTOF-MS assay was applied to the reanalysis of biological sample extracts to discover emergent NPS. More than 3,000 sample extracts were analyzed, and more than 20 emerging NPS were detected for the first time. Among these were isopropyl-U-47700, 3,4-methylenedioxy-U-47700, fluorofuranylfentanyl, N-methyl norfentanyl, 2F-deschloroketamine, 3,4-methylenedioxy-alpha-PHP, eutylone, and N-ethyl hexedrone.  相似文献   
908.
This study describes the performance of handheld Raman devices for determining whether suspect pharmaceutical tablets declared to contain controlled substances were consistent with authentic (CWA) or not consistent with authentic (NCWA) tablets using a simple, rapid, field-friendly method capable of being used by nonexperts. Twenty-five authentic products and 84 known NCWA tablets were examined using three “parent” devices for a total of 327 analyses. On average, the parent devices yielded a true pass rate of 100%, a true fail rate of 98.4%, a false pass rate of 1.6%, and a false fail rate of 0%. The methods/libraries were then transferred to 13 identical “daughter” devices, which were used to examine 10 suspect finished dosage forms in duplicate (six known NCWA tablets and four authentic tablets) for a total of 260 measurements. On average, the daughter devices had a true pass rate of 100%, a true fail rate of 95.5%, a false pass rate of 4.5%, and a false fail rate of 0.0%. These data demonstrate that the parent–daughter electronic transfer method was successful, which permits the ability to develop methods in the laboratory that can be seamlessly pushed out to field devices. The methods can then be used to (i) prioritize samples for additional testing using other more time-consuming laboratory-based techniques needed to detect and quantify active ingredients and (ii) help support the interdiction of dangerous tablets at ports of entry, thereby preventing them from reaching the supply chain.  相似文献   
909.
Objectives

While block randomized designs have become more common in place-based policing studies, there has been relatively little discussion of the assumptions employed and their implications for statistical analysis. Our paper seeks to illustrate these assumptions, and controversy regarding statistical approaches, in the context of one of the first block randomized studies in criminal justice—the Jersey City Drug Market Analysis Project (DMAP).

Methods

Using DMAP data, we show that there are multiple approaches that can be used in analyzing block randomized designs, and that those approaches will yield differing estimates of statistical significance. We develop outcomes using both models with and without interaction, and utilizing both Type I and Type III sums-of-squares approaches. We also examine the impacts of using randomization inference, an approach for estimating p values not based on approximations using normal distribution theory, to adjust for possible small N biases in estimating standard errors.

Results

The assumptions used for identifying the analytic approach produce a comparatively wide range of p values for the main DMAP program impacts on hot spots. Nonetheless, the overall conclusions drawn from our re-analysis remain consistent with the original analyses, albeit with more caution. Results were similar to the original analyses under different specifications supporting the identification of diffusion of benefits effects to nearby areas.

Conclusions

The major contribution of our article is to clarify statistical modeling in unbalanced block randomized studies. The introduction of blocking adds complexity to the models that are estimated, and care must be taken when including interaction effects in models, whether they are ANOVA models or regression models. Researchers need to recognize this complexity and provide transparent and alternative estimates of study outcomes.

  相似文献   
910.

The aim of this paper is to examine the influence of the right to information laws on sustainability transparency in European local governments. This goal is novel, in that previous studies have examined the effects of various factors on the dissemination of government information (demographic, socioeconomic, political and financial) but not the contribution of legal factors to online transparency on environmental, social and economic sustainability. Our research question is this: Do information laws contribute to transparency on sustainability? Using the Global Reporting Initiative guidelines and a statistical regression analysis, we studied the websites of 106 local governments in ten European countries. The results obtained show that when transparency laws clearly stipulate the rules applicable and the procedures established for appeals, exceptions, refusals and requests, this can favour transparency on environmental, social and economic sustainability. Our findings advance understanding of this field and reinforce the basis for legal reforms to enhance sustainability transparency.

  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