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   1566篇
  免费   65篇
各国政治   85篇
工人农民   190篇
世界政治   149篇
外交国际关系   97篇
法律   736篇
中国政治   13篇
政治理论   350篇
综合类   11篇
  2023年   6篇
  2022年   15篇
  2021年   20篇
  2020年   62篇
  2019年   62篇
  2018年   76篇
  2017年   78篇
  2016年   73篇
  2015年   60篇
  2014年   54篇
  2013年   264篇
  2012年   59篇
  2011年   55篇
  2010年   48篇
  2009年   53篇
  2008年   54篇
  2007年   51篇
  2006年   38篇
  2005年   54篇
  2004年   40篇
  2003年   43篇
  2002年   46篇
  2001年   31篇
  2000年   38篇
  1999年   25篇
  1998年   22篇
  1997年   17篇
  1996年   17篇
  1995年   18篇
  1994年   10篇
  1993年   16篇
  1992年   13篇
  1991年   6篇
  1990年   11篇
  1989年   13篇
  1988年   14篇
  1987年   10篇
  1986年   9篇
  1985年   6篇
  1984年   9篇
  1983年   5篇
  1982年   6篇
  1981年   3篇
  1980年   2篇
  1979年   5篇
  1978年   3篇
  1977年   3篇
  1975年   2篇
  1974年   2篇
  1969年   2篇
排序方式: 共有1631条查询结果,搜索用时 15 毫秒
101.
102.
The widespread use over the past two decades of Michigan's PA 198 Industrial Tax Abatement program provides an opportunity to assess the inter‐urban equity impacts of this economic development tool. Not only has PA 198 been used relatively more often by suburban municipalities, local governments at the metropolitan periphery are more likely to use abatements to attract new plants and new jobs. The older central cities primarily use the program to retain existing jobs, albeit at high cost of lost tax revenues. On balance, it appears that PA 198 has done little to alter the location decisions of participating firms.  相似文献   
103.
104.
105.
Among the unforeseen problems of the new industrial age has been the disposal of increasing quantities of wastes—many hazardous and toxic. Industrial chemistry has produced numerous products that, while useful, are alien to nature and resistant to biodegradation or detoxification. Growing public awareness of the possible hazards and risks involved in disposal of the residuals of industrial activities is arousing a popular demand for environmental protection. But this popular awareness depends upon public information and a degree of scientific literacy—conditions which vary widely among nations. Initial consequences are environmental regulations and restrictions respecting waste disposal in scientifically developed countries, and vulnerability among less developed countries to the export of hazardous wastes from the countries of their origin. A secondary consequence is the emergence of international waste trade as a national and international multidimensional policy problem.  相似文献   
106.
Hair samples of eight postmortem cases were analyzed in segments of 1 to 3 cm for cocaine, benzoylecgonine and cocaethylene. Samples were prepared for analysis by digestion in 0.1 M HCl and subsequent extraction with mixed-mode solid-phase extraction columns. Measurement was made by reversed-phase, narrow-bore HPLC and fluorescence detection using two laboratory-made internal standards. The concentrations were in the region of 0.29-316 ng/mg of hair for cocaine, 0.43-141 ng/mg of hair for benzoylecgonine and 0.93-1.83 ng/mg of hair for cocaethylene. All eight investigated cases had cocaine-positive segments. In six of the cases, all segments were positive, suggesting regular cocaine use and two showed in-between negative segments indicating an interruption or a change of the abuse intensity. The results showed a second, remarkable observation, i.e. enormous concentration differences (factor >150) for both cocaine and benzoylecgonine between the different subjects. Furthermore, interindividual cocaine/benzoylecgonine ratios ranged from 0.02 to 8.43. We believe these observations could in part be attributed to both some of the still existing limitations in the analytical approach(es), especially the mandatory hair washing steps, and in our still too limited knowledge of the hair incorporation processes. Nevertheless, in some cases, segmental analysis proved to be an important tool to distinguish, together with postmortem examination, deadly chronic abuse from single acute drug overdosage.  相似文献   
107.
A collaborative study on Raman spectroscopy was carried out by members of the ENFSI (European Network of Forensic Science Institutes) European Fibres Group (EFG) on three dyed fibers: two red acrylics and one red wool. Raman instruments from six different manufacturers were tested as well as nine different laser wavelengths ranging from blue (lambda = 458 nm) to near infrared-NIR (lambda = 1064 nm). This represents the largest comparison study of Raman analytical parameters carried out on identical fiber samples. For the chosen fiber and dye samples, red lasers (lambda = 633 and 685 nm) gave the poorest spectral quality whereas blue (458 nm), green (514 nm) and near infrared lasers (785, 830 and 1064 nm) provided average results. Blue (488 nm) and green lasers (532 nm) globally gave the best quality spectra. Fluorescence problems were often encountered with some of the excitation wavelengths and therefore a flexible Raman instrument equipped with different lasers can be recommended to measure forensic fiber samples. The instrument should also be equipped with a Raman microscope in order to be able to focus on a single fiber. This study shows that Raman spectroscopy usually enables the identification of the main dye present in a colored fiber; however, minor dye components are much more difficult to detect. SERRS (Surface Enhanced Resonance Raman Scattering) techniques give an improvement of the dye's spectral intensity but no spectral improvement was observed for the two red acrylic and red wool fibers tested.  相似文献   
108.
Although representative payeeship is prevalent among people with mental illness and shows promise to positively influence clinically relevant outcomes, research also suggests this legal mechanism could be implemented in ways that are problematic. The current study examined whether family representative payeeship was associated with elevated risk of family violence perpetrated by persons with severe mental illness (SMI). Data were collected every 4 months for 1 year in structured interviews with N = 245 persons with SMI who received disability benefits. Multivariate analyses showed that substance abuse, history of violence, frequency of family contact, and family representative payeeship were associated with elevated odds of family violence. Analyses also showed family contact and family representative payeeship had a cumulative effect on increasing the predicted probability of family violence (controlling for covariates such as violence history and substance abuse). The data shed light on the potential for family representative payeeship to be associated with increased risk of interpersonal conflict and violence in SMI.  相似文献   
109.
This study reports on the reduction in violent offending in a population of serious and violent juvenile offenders following an intensive institutional treatment program. The treatment group (N=101) is compared to a similar group that was assessed but not treated (N=147). All youth were sent to the program from a juvenile corrections institution where they had received the customary rehabilitation services. The results show a significant reduction in the prevalence of recidivism in the treated group after controlling for time at risk in the community and other covariates. The effects of non-random group assignment were reduced by including a propensity score analysis procedure in the outcome analysis. Untreated comparison youth appeared to be about twice as likely to commit violent offenses as were treated youth (44% vs. 23%). Similarly, treated youth had significantly lower hazard ratios for recidivism in the in the community than the comparison youth, even after accounting for the effects of non-random group assignment.  相似文献   
110.
Prevention science has produced information about risk and protective factors that predict adolescent drug use and related problem behaviors. This paper investigates the Communities That Care Youth Survey that measures multiple risk and protective factors. Using a sample of 172,628 students who participated in surveys administered in seven states in 1998, analyses were conducted to test the factor structure of these risk and protective factors and to test the equivalence of the factor models across five racial/ethnic groups (African Americans, Asians or Pacific Islanders, Caucasians, Hispanic Americans, and Native Americans), four grade levels (6th, 8th, 10th, and 12th) and both gender groups. Results support the construct validity of the surveys risk and protective factor scales and indicate that the measures are equally reliable across males and females and five racial/ethnic groups. Implications of these findings for science-based prevention planning are discussed.  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