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   14037篇
  免费   399篇
各国政治   638篇
工人农民   605篇
世界政治   941篇
外交国际关系   465篇
法律   8810篇
中国共产党   3篇
中国政治   103篇
政治理论   2778篇
综合类   93篇
  2021年   78篇
  2020年   174篇
  2019年   240篇
  2018年   328篇
  2017年   330篇
  2016年   326篇
  2015年   215篇
  2014年   265篇
  2013年   1479篇
  2012年   352篇
  2011年   365篇
  2010年   304篇
  2009年   341篇
  2008年   413篇
  2007年   366篇
  2006年   387篇
  2005年   346篇
  2004年   369篇
  2003年   317篇
  2002年   313篇
  2001年   545篇
  2000年   513篇
  1999年   368篇
  1998年   193篇
  1997年   197篇
  1996年   159篇
  1995年   153篇
  1994年   143篇
  1993年   149篇
  1992年   289篇
  1991年   320篇
  1990年   301篇
  1989年   294篇
  1988年   265篇
  1987年   291篇
  1986年   260篇
  1985年   254篇
  1984年   242篇
  1983年   243篇
  1982年   152篇
  1981年   160篇
  1980年   107篇
  1979年   175篇
  1978年   116篇
  1977年   98篇
  1976年   84篇
  1975年   95篇
  1974年   108篇
  1973年   120篇
  1972年   95篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
A simple procedure based on a common silica gel column chromatography for the isolation of Delta9-tetrahydrocannabinolic acid A (Delta9-THCA-A) from hemp in a multi-milligram scale is presented. Further, the decarboxylation reaction of Delta9-THCA-A to the toxicologically active Delta9-tetrahydrocannabinol (Delta9-THC) at different analytical and under-smoking conditions is investigated. Maximal conversion in an optimised analytical equipment yields about 70% Delta9-THC. In the simulation of the smoking process, only about 30 % of the spiked substance could be recovered as Delta9-THC.  相似文献   
942.
Few studies have examined how animal cruelty is learned within a specific social context among incarcerated individuals. Using data from 261 inmates, this study specifically addressed how demographic characteristics and childhood experiences with animal abuse may have affected the recurrence and onset of childhood and adolescent cruelty as a learned behavior. Multiple regression analyses revealed that inmates who experienced animal cruelty at a younger age were more likely to demonstrate recurrent animal cruelty themselves. In addition, respondents who observed a friend abuse animals were more likely to hurt or kill animals more frequently. Finally, inmates who were younger when they first witnessed animal cruelty also hurt or killed animals at a younger age.  相似文献   
943.
A single nucleotide polymorphism (SNP) multiplex has been developed to analyse highly degraded and low copy number (LCN) DNA template, i.e. <100 pg, for scenarios including mass disaster identification. The multiplex consists of 20 autosomal non-coding loci plus Amelogenin for sex determination, amplified in a single tube PCR reaction and visualised on the Applied Biosystems 3100 capillary electrophoresis (CE) system. Allele-specific primers tailed with shared universal tag sequences were designed to speed multiplex design and balance the amplification efficiencies of all loci through the use of a single reverse and two differentially labelled allele denoting forward universal primers. As the multiplex is intended for use with samples too degraded for conventional profiling, a computer program was specifically developed to aid interpretation. Critical factors taken into account by the software include empirically determined extremes of heterozygous imbalance (Hb) and the drop-out threshold (Ht) defined as the maximum peak height of a surviving heterozygous allele, where its partner may have dropped out. The discrimination power of the system is estimated at 1 in 4.5 million, using a White Caucasian population database. Comparisons using artificially degraded samples profiled with both the SNP multiplex and AMPFISTR SGM plus (Applied Biosystems) demonstrated a greater likelihood of obtaining a profile using SNPs for certain sample types. Saliva stains degraded for 147 days generated an 81% complete SNP profile whilst short tandem repeats (STRs) were only 18% complete; similarly blood degraded for 243 days produced full SNP profiles but only 9% with STRs. Reproducibility studies showed concordance between SNP profiles for different sample types, such as blood, saliva, semen and hairs, for the same individual, both within and between different DNA extracts.  相似文献   
944.
The consumption of Delta9-tetrahydrocannabinol (THC) as cannabis has been shown to result in impaired and culpable driving. Testing drivers for the presence of THC in blood is problematic as THC and its metabolites may remain in the blood for several days following its consumption, even though the drug may no longer have an influence on driving performance. In the present study, the aim was to assess whether performance on the standardised field sobriety tests (SFSTs) provides a sensitive measure of impaired driving behaviour following the consumption of THC. In a repeated measures design, 40 participants consumed cigarettes that contained either 0% THC (placebo), 1.74% THC (low dose) or 2.93% THC (high dose). For each condition, after smoking a cigarette, participants performed the SFSTs on three occasions (5, 55 and 105 min after the smoking procedure had been completed) as well as a simulated driving test on two occasions (30 and 80 min after the smoking procedure had been completed). The results revealed that driving performance was not significantly impaired 30 min after the consumption of THC but was significantly impaired 80 min after the consumption of THC in both the low and high dose conditions. The percentage of participants whose driving performance was correctly classified as either impaired or not impaired based on the SFSTs ranged between 65.8 and 76.3%, across the two THC conditions. The results suggest that performance on the SFSTs provides a moderate predictor of driving impairment following the consumption of THC and as such, the SFSTs may provide an appropriate screening tool for authorities that wish to assess the driving capabilities of individuals suspected of being under the influence of a drug other than alcohol.  相似文献   
945.
946.
The capacity of police departments to solve crimes and apprehend offenders is low for many types of crime, particularly crimes of profit. This article reviews a variety of studies of police apprehension and hypothesizes that an important determinant of the ability of the police to apprehend criminals is information. The complete absence of information for many types of crime places fairly clear upper bounds on the ability of the police to effect solutions.To discover whether these boundaries are high or low we analyzed data from the 1973 National Crime Panel about the types and amount of information potentially available to police through victim reports and patrol activities. The evidence suggests that if the police rely on information made readily available to them, they will never do much better than they are doing now. On the other hand, there appears to be more information available to bystanders and passing patrols than currently is being used, which suggests that surveillance strategies and improved police methods for eliciting, recording, and analyzing information supplied by victims and witnesses might increase the probability of solving crimes and making arrests. In light of this we review a few possibly helpful innovations suggested in the literature on police productivity and procedure.  相似文献   
947.
948.
949.
950.
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