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   936篇
  免费   32篇
各国政治   55篇
工人农民   21篇
世界政治   76篇
外交国际关系   36篇
法律   425篇
中国政治   5篇
政治理论   340篇
综合类   10篇
  2021年   6篇
  2020年   19篇
  2019年   12篇
  2018年   19篇
  2017年   23篇
  2016年   25篇
  2015年   13篇
  2014年   21篇
  2013年   141篇
  2012年   31篇
  2011年   27篇
  2010年   18篇
  2009年   26篇
  2008年   28篇
  2007年   43篇
  2006年   24篇
  2005年   20篇
  2004年   34篇
  2003年   32篇
  2002年   22篇
  2001年   15篇
  2000年   28篇
  1999年   15篇
  1998年   12篇
  1997年   15篇
  1996年   10篇
  1995年   12篇
  1994年   12篇
  1993年   15篇
  1992年   15篇
  1991年   16篇
  1990年   22篇
  1989年   13篇
  1988年   14篇
  1987年   10篇
  1986年   12篇
  1985年   15篇
  1984年   11篇
  1983年   9篇
  1982年   6篇
  1980年   10篇
  1979年   8篇
  1978年   12篇
  1976年   6篇
  1975年   11篇
  1974年   6篇
  1973年   5篇
  1969年   5篇
  1968年   6篇
  1966年   5篇
排序方式: 共有968条查询结果,搜索用时 31 毫秒
111.
112.
113.
114.
115.
116.
Transnational Models for Regulation of Nanotechnology   总被引:4,自引:0,他引:4  
Like all technologies, nanotechnology will inevitably present risks, whether they result from unintentional effects of otherwise beneficial applications, or from the malevolent misuse of technology. Increasingly, risks from new and emerging technologies are being regulated at the international level, although governments and private experts are only beginning to consider the appropriate international responses to nanotechnology. In this paper, we explore both the potential risks posed by nanotechnology and potential regulatory frameworks that law may impose. In so doing, we also explore the various rationales for international regulation including the potential for cross-boundary harms, sharing of regulatory expertise and resources, controlling protectionism and trade conflicts, avoiding a "race to the bottom" in which governments seek economic advantage through lax regulation, and limiting the "nano divide" between North and South. Finally, we examine some models for international regulation and offer tentative thoughts on the prospects for each.  相似文献   
117.
The Scent Transfer Unit (STU-100) is a portable vacuum that uses airflow through a sterile gauze pad to capture a volatiles profile over evidentiary items for subsequent canine presentation to assist law enforcement personnel. This device was evaluated to determine its ability to trap and release organic compounds at ambient temperature under controlled laboratory conditions. Gas chromatography-mass spectrometry (GC-MS) analyses using a five-component volatiles mixture in methanol injected directly into a capture pad indicated that compound release could be detected initially and 3 days after the time of collection. Additionally, 15 compounds of a 39-component toxic organic gaseous mixture (10-1000 parts per billion by volume [p.p.b.(v)]) were trapped, released, and detected in the headspace of a volatiles capture pad after being exposed to this mixture using the STU-100 with analysis via GC-MS. Component release efficiencies at ambient temperature varied with the analyte; however, typical values of c. 10% were obtained. Desorption at elevated temperatures of reported human odor/scent chemicals and colognes trapped by the STU-100 pads was measured and indicated that the STU-100 has a significant trapping efficiency at ambient temperature. Multivariate statistical analysis of subsequent mass spectral patterns was also performed.  相似文献   
118.
In forensics and archaeology, it is important to distinguish human from animal remains and to identify animal species from fragmentary bones and bloodstains. We report blind tests in which a protein radioimmunoassay (pRIA) was used to identify the species of six bone fragments lacking morphological specificity and 43 bloodstained lithic tools, knapped experimentally and soaked in blood of known animal and human origin. The submitters of the bone fragments and the bloodstained tools each listed a number of possible species, from which the testers selected the best match with the pRIA results. All six bone fragments were correctly identified: three humans, a deer, a dog, and a cow. Forty-three tools were stained with blood from a wide variety of species including ungulates, carnivores, a fish, and a bird. On 40 of these 43, at least one species (or blood-free control) was identified correctly. Some of the tools were stained with blood of two different species. A mixture of sheep and musk ox blood was correctly identified; in several other mixtures, only a single species was detected. Two tools with human blood and one with human sweat were correctly reported as human. There was a single false positive (one of three controls reported as weakly bovine) and no false negatives. We conclude that the pRIA technique shows a high degree of accuracy in discriminating human from animal bone fragments and bloodstains and in identifying animal species.  相似文献   
119.
120.
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