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   1018篇
  免费   33篇
各国政治   62篇
工人农民   31篇
世界政治   93篇
外交国际关系   89篇
法律   489篇
中国政治   9篇
政治理论   256篇
综合类   22篇
  2023年   5篇
  2021年   5篇
  2020年   6篇
  2019年   9篇
  2018年   16篇
  2017年   29篇
  2016年   39篇
  2015年   19篇
  2014年   15篇
  2013年   150篇
  2012年   24篇
  2011年   40篇
  2010年   33篇
  2009年   27篇
  2008年   37篇
  2007年   39篇
  2006年   45篇
  2005年   41篇
  2004年   39篇
  2003年   47篇
  2002年   39篇
  2001年   21篇
  2000年   19篇
  1999年   24篇
  1998年   15篇
  1997年   19篇
  1996年   18篇
  1995年   15篇
  1994年   16篇
  1993年   15篇
  1992年   13篇
  1991年   13篇
  1990年   8篇
  1989年   9篇
  1988年   12篇
  1987年   13篇
  1986年   18篇
  1985年   6篇
  1984年   8篇
  1983年   11篇
  1982年   8篇
  1981年   9篇
  1980年   4篇
  1979年   6篇
  1978年   7篇
  1977年   5篇
  1975年   7篇
  1974年   8篇
  1971年   3篇
  1969年   3篇
排序方式: 共有1051条查询结果,搜索用时 0 毫秒
71.
72.
The solution parameters associated with gradient elution reversed phase high-performance liquid chromatography (HPLC) were characterized by evaluating the electrospray ionization mass spectrometry (ESIMS) response of selected smokeless powder additives. Using direct liquid infusion, the positive ion ESIMS responses were determined for three general classes of powder constituents: dialkylphthalate acid esters, N,N'-dialkyl-N,N'-diphenyl urea based stabilizers and nitroso-, nitro-, and dinitro- derivatives of diphenylamine. The relative ESIMS intensities of the powder components were investigated as a function of three solution parameters: ammonium acetate concentration, pH, and percent methanol. The effect of the ammonium acetate concentration demonstrates that the electrolyte is required for efficient ionization and the ESIMS intensity was optimal at a concentration of 2mM for the selected compounds, except 2,4'-dinitrodiphenylamine. The aqueous solution pH, corresponding to the available protons in solution, did not have a significant effect on the ESIMS intensity of the analytes. The percent methanol was evaluated with both decreasing and constant electrolyte concentrations to demonstrate the effects of droplet stability and ion transfer into the gas phase. These findings were applied to the analysis of the selected smokeless powder additives using HPLC-ESIMS to illustrate increased sensitivity for the protonated molecules.  相似文献   
73.
There is evidence that the multinational corporation (MNC) and a developing nation may have a set of mutually beneficial goals. This article investigates the goals of the multinational corporation and the goals of a developing nation. It then illustrates the mutual benefits in terms of resource identification, and technology selection and development. A planning mechanism is suggested. Finally, some guide lines are offered that should enhance the probability of cooperation.  相似文献   
74.
Political relationships often vary over time, but standard modelsignore temporal variation in regression relationships. We describea Bayesian model that treats the change point in a time seriesas a parameter to be estimated. In this model, inference forthe regression coefficients reflects prior uncertainty aboutthe location of the change point. Inferences about regressioncoefficients, unconditional on the change-point location, canbe obtained by simulation methods. The model is illustratedin an analysis of real wage growth in 18 OECD countries from1965–1992.  相似文献   
75.
76.
Suicide by asphyxiation with a plastic bag placed over the head is a method that has been advocated by right-to-die groups. Recently, such groups have proposed the introduction of helium into the plastic bag as a means of hastening death. Helium is readily available at toy stores, where it is sold in tanks for balloon inflation. It produces asphyxiation by the exclusion of oxygen in enclosed spaces. We report 7 fatalities throughout an 18-month period involving plastic bag suffocation in conjunction with helium use. These fatalities coincide with publication of an update to a popular right-to-die text in which this method is described. Although right-to-die literature was absent from all scenes, this method was not previously observed in our jurisdiction, and the deaths likely reflect exposure to this information. Because of analytical difficulties in testing for helium in biologic specimens, death certification rests on scene investigation.  相似文献   
77.
This paper discusses results of a supercritical fluid extraction-gas chromatography/mass spectrometry (SFE-GC/MS) study of small samples ( 100 microg to 1 mg) of human scalp hair. The method offers a number of benefits including greater sensitivity than liquid extraction methods because the entire extractable mass is transferred to the analytical system, compared with only a few percent from a conventional liquid extraction/injection. The project's goals were to determine if SFE-GC/MS analyses of the surface-extractable components of an individual's hair yield consistent chemical profiles and to investigate if the profiles are sufficiently different to distinguish them from those of other individuals. In addition, the mtDNA sequences from ten of the same individuals used in the SFE-GC/MS study from four family units were determined, and, while the families were distinguishable, the maternal relations yielded identical sequences. In tandem, SFE-GC/MS and mtDNA techniques may provide valuable complementary data from forensic hair samples.  相似文献   
78.
According to Gottfredson and Hirschi's (1990) A General Theory ofCrime, all illegal activity is the manifestation of a single underlyingcause. The authors argue that inadequate child-rearing causes individualsto develop a similar type of propensity for criminal and analogousbehavior. Gottfredson and Hirschi label this characteristiclow self-control. Six dimensions, which can be identified intheir theory, are suggested to comprise a final low self-controltrait. Further, low self-control is proposed to be an invariantcharacteristic (i.e., its form does not change with the age of theindividual or context in which the person resides). In this research, weevaluate these two propositions. First, the six dimensions are measured andused to determine if a multidimensional model can explain another commonfactor—low self-control—in two samples of individuals (fromdifferent locales) with dissimilar mean ages. Second, low self-control inboth samples is tested for invariance. We test the proposed invariance oflow self-control by examining if the parameter values in a model, which isreflective of Gottfredson and Hirschi's conceptualization of thecharacteristic, differ across the two samples of individuals. The resultssupport both of Gottfredson and Hirschi's propositions. Lowself-control does appear to be a multidimensional characteristic whosedimensions represent another common factor. Low self-control also appears tobe an invariant latent trait that members of these two samplespossess. These tests help to clarify Gottfredson and Hirschi'sconceptualization of low self-control.  相似文献   
79.
80.
This paper considers two specific difficulties in developing a code of ethics for the public sector, the contested nature of the values to be expressed in a code of ethics and the organisational demands of a corporate managerialist framework which uses performance indicators. Using the example of the Western Australian public sector code of ethics, the authors conclude that a good strategy for developing a public sector code of ethics will recognise contestability, demonstrate philosophical integrity in the code, mesh the code with identified performance indicators and provide whistleblower protection. The strategy described provides a sufficient framework for any public sector bureaucracy to develop a justifiable code of ethics for use by public sector employees.  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