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   284篇
  免费   3篇
各国政治   10篇
工人农民   14篇
世界政治   16篇
外交国际关系   15篇
法律   154篇
中国政治   1篇
政治理论   77篇
  2022年   1篇
  2021年   4篇
  2020年   4篇
  2019年   6篇
  2018年   4篇
  2017年   3篇
  2016年   7篇
  2015年   1篇
  2014年   9篇
  2013年   19篇
  2012年   8篇
  2011年   8篇
  2010年   13篇
  2009年   8篇
  2008年   6篇
  2007年   10篇
  2006年   15篇
  2005年   12篇
  2004年   10篇
  2003年   15篇
  2002年   9篇
  2001年   15篇
  2000年   8篇
  1999年   8篇
  1998年   4篇
  1997年   3篇
  1995年   2篇
  1994年   5篇
  1993年   1篇
  1992年   5篇
  1991年   6篇
  1990年   7篇
  1989年   6篇
  1988年   4篇
  1987年   5篇
  1986年   6篇
  1985年   7篇
  1984年   2篇
  1982年   3篇
  1980年   1篇
  1979年   4篇
  1978年   1篇
  1977年   3篇
  1975年   2篇
  1974年   1篇
  1973年   3篇
  1972年   1篇
  1971年   1篇
  1969年   1篇
排序方式: 共有287条查询结果,搜索用时 156 毫秒
141.
The U.S. agricultural sector is vulnerable to intentionally introduced microbial threats because of its wide and open distribution and economic importance. To investigate such events, forensically valid assays for plant pathogen detection are needed. In this work, real‐time PCR assays were developed for three model plant pathogens: Pseudomonas syringae pathovar tomato, Xylella fastidiosa, and Wheat streak mosaic virus. Validation included determination of the linearity and range, limit of detection, sensitivity, specificity, and exclusivity of each assay. Additionally, positive control plasmids, distinguishable from native signature by restriction enzyme digestion, were developed to support forensic application of the assays. Each assay displayed linear amplification of target nucleic acid, detected 100 fg or less of target nucleic acid, and was specific to its target pathogen. Results obtained with these model pathogens provide the framework for development and validation of similar assays for other plant pathogens of high consequence.  相似文献   
142.
Based on a quantitative content analysis of Irish Times newspaper articles, this study investigates how Irish relief and development NGOs were linked with the concepts of legitimacy and accountability in newspaper coverage between 1994 and 2009. Key findings included that NGO accountability received more coverage than NGO legitimacy, and “principal-agent” approaches to NGO accountability received more coverage than “stakeholder” approaches. Employing the media theories of agenda-setting and priming, one can infer that Irish Times readers might be more likely to evaluate Irish NGOs in terms of accountability than legitimacy and to consider NGO accountability in principal-agent rather than stakeholder terms.  相似文献   
143.
The International Society for Forensic Genetics (ISFG) has established a Paternity Testing Commission (PTC) with the purpose of formulating international recommendations concerning genetic investigations in paternity testing. The PTC recommends that paternity testing be performed in accordance with the ISO 17025 standards. The ISO 17025 standards are general standards for testing laboratories and the PTC offers explanations and recommendations concerning selected areas of special importance to paternity testing.  相似文献   
144.
145.
The introduction of DNA analysis to forensic science brought with it a number of choices for analysis, not all of which were compatible. As laboratories throughout Europe were eager to use the new technology different systems became routine in different laboratories and consequently, there was no basis for the exchange of results. A period of co-operation then started in which a nucleus of forensic scientists agreed on an uniform system. This collaboration spread to incorporate most of the established forensic science laboratories in Europe and continued through two major changes in the technology. At each step agreement was reached on which systems to use. From the beginning it was realised that DNA databases would provide the criminal justice systems with an efficient way of crime solving and consequently some local databases were created. It was not until the introduction of the amplification technology linked to the analysis of short tandem repeats that a sufficiently sensitive and robust system was available for the formation of efficient and effective DNA databases. Comprehensive legislation enacted in the UK in 1995 enabled forensic scientists to set up the first national DNA database which would hold both personal DNA profiles together with results obtained from crime scenes. Other countries quickly followed but in some the legislation has severely restricted the amount and type of data which can be retained and, therefore, effectiveness of the databases is limited. The widespread use of commercially produced multiplex kits has produced a situation in which nearly all European laboratories are using compatible systems and there is, therefore, the potential for the introduction of a pan-European DNA database. However, the exchange of results between countries is hampered by the various legislations which currently exist.  相似文献   
146.
How do individuals on the battlefield respond to the introduction of new technologies? How will unmanned and increasingly autonomous technologies be received by ground combat personnel? In this paper we explore tactical-level perceptions of one particular technology—armed unmanned aerial vehicles (UAVs)—by conducting a survey experiment of ground fires controllers. Our findings reveal that these personnel have strong behavioral reactions to the introduction of unmanned technology. Especially in situations with high risk to ground troops, we find a strong preference for manned aircraft with implications for the future use of UAVs and human–machine relationships in war. These results suggest the need to incorporate behavioral variables into future studies of military adoption and innovation and indicate that the future adoption of unmanned systems may be just as much about the “warm fuzzy” of trust as confidence in unmanned capabilities.  相似文献   
147.
148.
Knowledge transfer from science to industry has been shown to be beneficial for the corporate partner. In order to get a better understanding of the reasons behind these positive effects, this study focuses on the junction of science and industry by comparing characteristics of academic inventions that are transferred to industry and those staying in the public sector. Academic inventions are identified via patent applications of German academic scientists. We find that academic patents assigned to corporations are more likely to enable firms reaping short term rather than, possibly more uncertain, long-run returns, in contrast to patents that stay in the public sector. Firms also strive for academic inventions with a high blocking potential in technology markets. Academic patents issued to corporations appear to reflect less complex inventions as compared to inventions that are patented by the public science sector.  相似文献   
149.
The development of the HIV-1-prevalence among drug deaths (n = 753) in several German cities (West Berlin, Frankfurt, Munich, Hamburg, Bremen, Cologne and Stuttgart) from 1985 to 1988 was evaluated; in 1988 43% of 674 deceased drug addicts were examined. The regional prevalence rate was between 15 and 25%; only in Berlin 42% of the drug deaths were HIV-infected (cumulated data of all cities over the 4-year-period: 26%). There was no uniform or steady regional development of HIV-1-prevalence in the different cities. The ratio men/women among drug deaths was 3:1. The HIV-1-prevalence among males was 22%, among females 40%. HIV-infected individuals were 2-3 years older than seronegatives. Predictions concerning the trend of prevalence rates are not possible up to now. Continuous monitoring of the HIV-status of drug deaths seems to be a worthful method to evaluate the spread of this disease among the risk group of intravenous drug addicts.  相似文献   
150.
DNA extracted from 33 postmortem muscle specimens was analyzed using MZ 1.3, a hypervariable minisatellite probe, as well as locus-specific minisatellite probes (g3, MS1 and MS43). After storage at -25 degrees C for 10 months, DNA from all the samples was partially (approximately 21% of total DNA) degraded even when autopsy was performed 1 day postmortem. However, more than 90% of DNA samples up to at least 3 days postmortem were suitable to obtain good restriction fragment length polymorphism (RFLP) patterns. When small strips of specimen were stored for 8 days at room temperature in moist chambers, approximately 42% of total DNA was degraded. Only 30% of these DNA samples still showed good RFLP patterns. However, no obvious relation between qualities of DNA analyzed by detection of RFLP and quantities of total and high-MW DNA became apparent. A case of familial relationship was ascertained by DNA fingerprints. Since DNA of good quality can be recovered from muscle tissues in large quantities, DNA extraction from muscle tissues and detection of RFLP patterns should be very useful for individual identification in autopsy cases.  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