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   7948篇
  免费   482篇
各国政治   406篇
工人农民   267篇
世界政治   568篇
外交国际关系   300篇
法律   5364篇
中国政治   37篇
政治理论   1448篇
综合类   40篇
  2021年   53篇
  2020年   188篇
  2019年   193篇
  2018年   236篇
  2017年   246篇
  2016年   249篇
  2015年   226篇
  2014年   210篇
  2013年   872篇
  2012年   181篇
  2011年   190篇
  2010年   235篇
  2009年   242篇
  2008年   187篇
  2007年   192篇
  2006年   195篇
  2005年   178篇
  2004年   194篇
  2003年   180篇
  2002年   157篇
  2001年   327篇
  2000年   258篇
  1999年   238篇
  1998年   108篇
  1997年   74篇
  1996年   75篇
  1995年   83篇
  1994年   92篇
  1993年   96篇
  1992年   154篇
  1991年   160篇
  1990年   147篇
  1989年   158篇
  1988年   129篇
  1987年   144篇
  1986年   125篇
  1985年   138篇
  1984年   108篇
  1983年   117篇
  1982年   85篇
  1981年   79篇
  1980年   57篇
  1979年   112篇
  1978年   73篇
  1977年   60篇
  1976年   50篇
  1975年   49篇
  1974年   56篇
  1973年   59篇
  1972年   45篇
排序方式: 共有8430条查询结果,搜索用时 15 毫秒
241.
A 55-year-old man complained of sudden onset of severe neck pain. This was followed by prompt loss of consciousness and death. Autopsy revealed rupture of a saccular aneurysm, which was considered to have resulted from enlargement of the remaining ductal tissue, and was located on the medial aspect of the uppermost portion of the descending aorta. Dense blood extravasation was noted in the posterior mediastinum and extending to the strap muscles of the neck and larynx. Histological examination of the rupture site revealed disappearance of the medial elastic fibers and thickened intima covered with dense fibrous tissue. Spontaneous ductus arteriosus aneurysm in adults is a rare finding, but widespread use of imaging technologies has revealed that it develops more frequently than previously recognized. Fatal complications may occur even when the aneurysm is relatively small. Therefore, pathologists should be aware of this aneurysm as a potential cause of sudden death.  相似文献   
242.
This study is the first to examine the background level of male DNA on underpants worn by females in the absence of sexual contact. Here, we examined 103 samples from the inside front of underpants from 85 female volunteers. Samples were examined for the presence of male DNA using NGM SElect and PowerPlex Y23 kits. Only five samples gave a “complete” Y-STR profile, even though 83.5% of our volunteers cohabited with a male. In all cases where a partner reference sample was available, the Y-STR profile matched the cohabiting partner. We have demonstrated that a Y-STR profile is not expected on the inside front of underpants worn by females after social contact alone. The results of this study are informative for evaluating the significance of a Y-STR profile on underpants in cases of alleged sexual assault.  相似文献   
243.
This study describes the performance of handheld Raman devices for determining whether suspect pharmaceutical tablets declared to contain controlled substances were consistent with authentic (CWA) or not consistent with authentic (NCWA) tablets using a simple, rapid, field-friendly method capable of being used by nonexperts. Twenty-five authentic products and 84 known NCWA tablets were examined using three “parent” devices for a total of 327 analyses. On average, the parent devices yielded a true pass rate of 100%, a true fail rate of 98.4%, a false pass rate of 1.6%, and a false fail rate of 0%. The methods/libraries were then transferred to 13 identical “daughter” devices, which were used to examine 10 suspect finished dosage forms in duplicate (six known NCWA tablets and four authentic tablets) for a total of 260 measurements. On average, the daughter devices had a true pass rate of 100%, a true fail rate of 95.5%, a false pass rate of 4.5%, and a false fail rate of 0.0%. These data demonstrate that the parent–daughter electronic transfer method was successful, which permits the ability to develop methods in the laboratory that can be seamlessly pushed out to field devices. The methods can then be used to (i) prioritize samples for additional testing using other more time-consuming laboratory-based techniques needed to detect and quantify active ingredients and (ii) help support the interdiction of dangerous tablets at ports of entry, thereby preventing them from reaching the supply chain.  相似文献   
244.
Objectives

While block randomized designs have become more common in place-based policing studies, there has been relatively little discussion of the assumptions employed and their implications for statistical analysis. Our paper seeks to illustrate these assumptions, and controversy regarding statistical approaches, in the context of one of the first block randomized studies in criminal justice—the Jersey City Drug Market Analysis Project (DMAP).

Methods

Using DMAP data, we show that there are multiple approaches that can be used in analyzing block randomized designs, and that those approaches will yield differing estimates of statistical significance. We develop outcomes using both models with and without interaction, and utilizing both Type I and Type III sums-of-squares approaches. We also examine the impacts of using randomization inference, an approach for estimating p values not based on approximations using normal distribution theory, to adjust for possible small N biases in estimating standard errors.

Results

The assumptions used for identifying the analytic approach produce a comparatively wide range of p values for the main DMAP program impacts on hot spots. Nonetheless, the overall conclusions drawn from our re-analysis remain consistent with the original analyses, albeit with more caution. Results were similar to the original analyses under different specifications supporting the identification of diffusion of benefits effects to nearby areas.

Conclusions

The major contribution of our article is to clarify statistical modeling in unbalanced block randomized studies. The introduction of blocking adds complexity to the models that are estimated, and care must be taken when including interaction effects in models, whether they are ANOVA models or regression models. Researchers need to recognize this complexity and provide transparent and alternative estimates of study outcomes.

  相似文献   
245.

We study voting rules with respect to how they allow or limit a majority from dominating minorities: whether a voting rule makes a majority powerful and whether minorities can veto the candidates they do not prefer. For a given voting rule, the minimal share of voters that guarantees a victory to one of the majority’s most preferred candidates is the measure of majority power; and the minimal share of voters that allows the minority to veto each of their least preferred candidates is the measure of veto power. We find tight bounds on such minimal shares for voting rules that are popular in the literature and used in real elections. We order the rules according to majority power and veto power. Instant-runoff voting has both the highest majority power and the highest veto power; plurality rule has the lowest. In general, the greater is the majority power of a voting rule, the greater its veto power. The three exceptions are: voting with proportional veto power, Black’s rule and Borda’s rule, which have relatively weak majority power and strong veto power, thus providing minority protection. Our results can shed light on how voting rules provide different incentives for voter participation and candidate nomination.

  相似文献   
246.
This study examines the relationship between policy interventions by the International Monetary Fund (IMF) and de jure labor rights. Combining two novel data sets with unprecedented country-year coverage – leximetric data on labor laws and disaggregated data on IMF conditionality – our analysis of up to 70 developing countries from 1980 to 2014 demonstrates that IMF-mandated labor market policy measures significantly reduce both individual and collective labor rights. Once we control for the effect of labor market policy measures, however, we find that collective labor rights increase in the wake of IMF programs. We argue that this result is explained by the impact of union pressure on governments which, in such a context, are imbued with the policy space to respond to domestic interest groups. The study has broader theoretical implications as to when international organizations are effective in constraining governments’ choices.  相似文献   
247.
Empirical research on the determinants of individual-level support for trade liberalization has focused almost entirely on the economic effects of trade. Yet, international relations scholarship has long recognized that commerce also has a variety of security implications. This paper explores if and when security considerations influence individual attitudes toward trade. In this study, we ask two questions: First, to what extent do expectations about the security implications of trade affect individual-level attitudes toward trade agreements? Second, does the introduction of security concerns into the discussion of trade agreements influence how heavily individuals weigh their economic costs and benefits? We employ an original experiment embedded in a conjoint survey to investigate the relative impact of a variety of economic and security considerations on respondents’ support for trade. Our findings suggest that security information matters and undermines the appeal of some, though not all, economic arguments for trade liberalization among our respondents.  相似文献   
248.
Journal of Youth and Adolescence - Chronotype, or morningness/eveningness, has been associated with adjustment in both children and adolescents. Specifically, eveningness has been linked to...  相似文献   
249.

There is strong evidence that chronic, systemic inflammation hastens onset of the diseases of old age that ultimately lead to death. Importantly, several studies suggest that childhood adversity predicts chronic inflammation. Unfortunately, this research has been plagued by retrospective reports of childhood adversity, an absence of controls for adult stressors, and a failure to investigate various competing models of the link between childhood adversity and chronic inflammation. The present study was designed to address these limitations. Using 18 years of data collected from 413 African Americans (58% female) included in the Family and Community Health Study, hierarchical regression analyses provided support for a nuanced early life sensitivity explanation for the link between early adversity and adult chronic inflammation. Controlling for health risk behaviors and adult SES, late childhood (ages 10–12) adversity amplified the association between adult adversity (age 29) and chronic inflammation. This interaction operated in a domain-specific fashion. Harsh parenting amplified the relation between intimate partner hostility and inflammation, whereas early discrimination amplified the relation between adult discrimination and inflammation. These findings suggest that individuals may be primed to respond physiologically to adverse adult circumstances that resemble those experienced earlier in life.

  相似文献   
250.
The problem‐solving capacity and problem‐generating potential of multilevel systems entail the need for the delegation of authority. When the problem concerned is about how to put an abstract policy concept into a practicable policy tool, the choice of the respective delegation trajectory depends on the policy models or the policy‐relevant knowledge that the respective political levels can supply. When regarding the European Union (EU) level as the starting point of knowledge creation and delegation trajectories, and concentrating on transaction costs, policy knowledge and models generated at the international level provide the most cost‐effective solution. Only when the international level is not able to provide further policy knowledge and innovation does the EU delegate its definitional authority, first downward to the member states and then sideways to EU agencies. We illustrate the plausibility of our dynamic understanding of multilevel governance by using Environmental Policy Integration as an example.  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