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   10634篇
  免费   269篇
各国政治   402篇
工人农民   384篇
世界政治   721篇
外交国际关系   289篇
法律   6715篇
中国政治   67篇
政治理论   2237篇
综合类   88篇
  2020年   103篇
  2019年   159篇
  2018年   191篇
  2017年   219篇
  2016年   213篇
  2015年   161篇
  2014年   184篇
  2013年   963篇
  2012年   216篇
  2011年   263篇
  2010年   213篇
  2009年   266篇
  2008年   269篇
  2007年   269篇
  2006年   262篇
  2005年   242篇
  2004年   235篇
  2003年   242篇
  2002年   235篇
  2001年   423篇
  2000年   368篇
  1999年   297篇
  1998年   161篇
  1997年   122篇
  1996年   136篇
  1995年   133篇
  1994年   133篇
  1993年   134篇
  1992年   232篇
  1991年   251篇
  1990年   241篇
  1989年   249篇
  1988年   225篇
  1987年   224篇
  1986年   262篇
  1985年   257篇
  1984年   229篇
  1983年   214篇
  1982年   152篇
  1981年   128篇
  1980年   113篇
  1979年   151篇
  1978年   85篇
  1977年   111篇
  1976年   95篇
  1975年   71篇
  1974年   89篇
  1973年   83篇
  1972年   78篇
  1971年   69篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
311.
On the afternoon of 7 May 1915 the Cunard Liner Lusitania was torpedoed by a German U-boat whilst en route to Liverpool. Consequently in sank with the loss of 1,195 lives. A series of investigative and formal research exercises, undertaken in the light of eye-witness accounts of the events surrounding that tragedy, has given rise to a number of hypotheses concerning the loss of this vessel. In this paper all the available evidence concerning the attack, and the one or more explosions that occurred, is summarised. The conclusions regarding the torpedo effects and the most likely causes of the secondary events are reported.  相似文献   
312.
The article presents the results of an examination of the dry residue of liquor crystallograms (DRLC) using infrared spectroscopy technique. 36 spectrograms were studied. Elements of similarity and difference were revealed in the spectrograms of organic substance (antifreeze, sodium cyclamate and fatty tissue), of DRLC of the crystal-forming matter CuCl(2)x2H(2)0, of DRLC of a live person and cadaveric liquor (with no brain injury in respective case histories), of DRLC of liquor of live persons with a brain injury, of DRLC of liquor of persons who died of a brain injury and of persons who died of other causes.  相似文献   
313.
314.

Purpose

Knowledge about offenders and knowledge about victims has traditionally been undertaken without formal consideration of the overlap among the two. A small but growing research agenda has examined the extent of this overlap. At the same time, there has been a minimal amount of research regarding offending and victimization among minority youth, and this is most apparent with respect to Hispanics, who have been increasing in population in the United States.

Materials &; Methods

This study explores the joint, longitudinal overlap between offending and victimization among a sample of Puerto Rican youth from the Bronx, New York.

Results

Results indicate: (1) an overlap between offending and victimization that persists over time, (2) a considerable overlap in the number, type, direction, and magnitude of the effect of individual, familial, peer, and contextual factors on both offending and victimization, (3) some of the factors related to offending were only relevant at baseline and not for the growth in offending but that several factors were associated with the growth in victimization, and (4) various risk factors could not explain much of the overlap between offending and victimization.

Conclusions

Theoretical, policy, and future research directions are addressed.  相似文献   
315.
This study examines the psychological impact of viewing disturbing media on investigators engaged in computer forensics work. Twenty-eight federal law enforcement personnel who investigate Internet child pornography cases completed measures of secondary traumatic stress disorder (STSD) and burnout. Substantial percentages of investigators reported poor psychological well-being. Greater exposure to disturbing media was related to higher levels of STSD and cynicism. STSD and burnout scores were related to increased protectiveness of family, reliance on co-workers, general distrust, and turnover intentions. On a positive note, investigators scored high in professional efficacy, indicating they feel their work makes a difference. Furthermore, personnel with supportive relationships scored lower on both STSD and burnout.  相似文献   
316.
Deterrence theory has been a centerpiece of theoretical and empirical research in criminology. Largely due to the early work of Beccaria however, much of this research has focused on estimating the effect of the certainty of punishment, or the costs of crime, on criminal offending. Although the benefits/rewards of crime are as important as the costs, conceptualization and operationalization of this portion of the decision-making process has only recently accumulated. In an effort to provide a counterpart to the summary statements available regarding the costs of crime, this paper undertakes a statistical summary of the empirical studies that have examined the benefits/offending relationship, with specific attention paid not only to the overall relationship, but also to several key moderators. Using 40 specific estimates from 13 studies since 1990, the analysis provides evidence of a positive and significant relationship between benefits and offending, but that the overall relationship varies in several ways. Directions for future research are outlined.  相似文献   
317.
Abstract:  We retrospectively reviewed autopsy records at a statewide medical examiner's office in order to identify and characterize deaths due to child abuse. In a 6-year period in New Mexico, the medical examiner investigated 45 deaths determined to be child abuse-related. Decedents were predominantly male (68.9%), Hispanic White (53.3%), and all were 5 years of age or younger, with a median age of 1 year. Head injuries were the most common cause of death (44.4%), followed by battered baby syndrome (15.6%). Relatives were involved as alleged perpetrators in 80% of the cases, with the father most often implicated (36.1% of cases), and 88.9% of child abuse injuries resulting in death occurred in the family's residence. Toxicology was positive in 26.7% of cases, but only two cases had substances of abuse present. Information on risk factors such as prematurity, parental age, and history of abuse was also collected.  相似文献   
318.
The extent to which local life circumstances influence criminal activity has been the focus of much theoretical debate. Although empirical research has been initiated, it remains limited. Herein, we use data on 524 serious offenders from the California Youth Authority for a seven‐year post‐parole period to examine the relationship between changes in local life circumstances and criminal activity. We extend previous research by employing a statistical model that accounts for the joint distribution of violent and nonviolent crime during the late teens and twenties in order to present information on patterns of criminal activity during a newly recognized developmental period of the life course, “emerging adulthood.”  相似文献   
319.
Since 1958 NASA has invested approximately $3.7 billion in life sciences R&D in the support of the successful human space flight program. There are numerous studies documenting the spin-off technologies that can be traced to NASA research and development activities. Most of these studies describe the technologies and their uses; however only a few measure the economic impact of the spin-offs and most of these are benefit/cost studies that tend to overstate benefits or underestimate costs. This study takes a different approach, measuring only economic impacts to the companies that developed successful spin-off products from NASA life sciences investments. A personal interview was conducted with each company and the benefits are conservatively estimated as the value-added by the NASA technology to the company's output and the amount of additional private R&D stimulated by the NASA R&D.This pilot study of fifteen companies, using a very conservative measurement technique, found a large return to companies that have successfully commercialized NASA life sciences spin-off products. Value-added benefits totaled over $3.7 billion in life sciences R&D in the support of the successful human space flight program. There are numerous studies documenting the spin-off technologies that can be traced to NASA research and development activities. Most of these studies describe the technologies and their uses; however only a few measure the economic impact of the spin-offs and most of these are benefit/cost studies that tend to overstate benefits or underestimate costs. This study takes a different approach, measuring only economic impacts to the companies that developed successful spin-off products from NASA life sciences investments. A personal interview was conducted with each company and the benefits are conservatively estimated as the value-added by the NASA technology to the company's output and the amount of additional private R&D stimulated by the NASA R&D.This pilot study of fifteen companies, using a very conservative measurement technique, found a large return to companies that have successfully commercialized NASA life sciences spin-off products. Value-added benefits totaled over 1.5 billion and a NASA R&D total investment in these 15 technologies of 64 million was found to stimulate an additional64 million was found to stimulate an additional 200 million in private R&D.  相似文献   
320.
An additional 20 novel mini-short tandem repeat (miniSTR) loci have been developed and characterized beyond the six previously developed by our laboratory for a total of 26 non-CODIS miniSTR markers. These new markers produce short PCR products in the target range of 50-150 base pairs (bp) by moving the primer sequences as close as possible-often directly next to the identified repeat region. These candidate loci were initially screened based on their small amplicon sizes and locations on chromosomes currently unoccupied by the 13 CODIS STR loci or at least 50 Mb away from them on the same chromosome. They were sequenced and evaluated across more than 600 samples, and their population statistics were determined. The heterozygosities of the new loci were compared with those of the 13 CODIS loci and all were found to be comparable. Only five of the new loci had lower values than the CODIS loci; however, all of these were much smaller in size. This data suggests that these 26 miniSTR loci will serve as useful complements to the CODIS loci to aid in the forensic analysis of degraded DNA, as well as missing persons work and parentage testing with limited next-of-kin reference samples.  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