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Jeffrey Butler 《Journal of contemporary African studies : JCAS》1983,3(1-2):230-245
Patrick Duncan: South African and Pan‐African by C. J. Driver Heinemann, London, 1980. xiv plus 326 pp. including illustrations, maps, notes, bibliography and indexes. £19,50. 相似文献
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Multiplex analysis of genetic markers has become increasingly important in a number of fields, including DNA diagnostics and human identity testing. Two methods for examination of single nucleotide polymorphisms (SNPs) with a potential for a high degree of multiplex analysis of markers are primer extension with fluorescence detection, and allele-specific hybridization using flow cytometry. In this paper, we examined 50 different SNPs on the Y-chromosome using three primer extension multiplexes and five hybridization multiplex assays. For certain loci, the allele-specific hybridization method exhibited sizable background signal from the absent alternate allele. However, 100% concordance (>2000 alleles) was observed in ten markers that were typed using both methods. A total of 18 unique haplogroups out of a possible 45 were observed in a group of 229 U.S. African American and Caucasian males with the majority of samples being assigned into 2 of the 18 haplogroups. 相似文献
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This article analyzes the impact of policy variables--employer accommodations, state Social Security Disability Insurance (DI) allowance rates, and DI benefits--on the timing of an application for DI benefits by workers with a work-limiting health condition starting when their health condition first begins to bother them. The analysis uses a rich mixture of personal and employer characteristics from the Health and Retirement Study linked to Social Security administrative records. We find that most workers do not apply immediately for DI benefits when they are first bothered by a health condition. On the contrary, the median working-age man with a work-limiting condition waits 7 years after that time before applying, and the median working-age woman waits 8 years. Although the risk of applying for benefits is greatest in the year following onset, only 16 percent of men and 13 percent of women in our sample apply within the first year, and the risk of application falls thereafter. That finding suggests that institutional factors, in addition to health factors, may play a role in the timing of DI applications. Using kernel density estimates of the distribution of application and nonapplication ordered by state allowance rates (the rate of acceptance per DI determination in each state), we find that both men and women who live in states with high allowance rates are disproportionately more likely to apply for benefits in the first year after their condition begins to bother them than are those in states with low allowance rates. Using life-table analysis, we also find that men and women who are accommodated by their employers are significantly less likely to apply for DI benefits in each of the first few years after their condition begins to bother them than are those who are not accommodated. On the basis of this evidence, we include these policy variables in a model of the timing of DI application that controls for other socioeconomic variables as well as health. Using a hazard model, we find that workers who live in states with higher allowance rates apply for DI benefits significantly sooner than those living in states with lower allowance rates following the onset of a work-limiting health condition. Workers who are accommodated following the onset of a work-limiting health condition, however, are significantly slower to apply for DI benefits. Using the mean values of all explanatory variables, we estimate the relative importance of changes in these policy variables on the speed with which workers apply for benefits after onset. We find that the mean time until application for men is 10.22 years. Universal accommodations following onset would delay application by 4.36 years. In contrast, a 20 percent decrease in state allowance rates would delay application by only 0.88 years. For working-age women, the average expected time until application once a condition begins to bother them is 10.58 years. Universal accommodations would delay that by 3.76 years, and a 20 percent decrease in allowance rates would delay it by 1.47 years. A complication in this analysis is that the policy variables are to some degree endogenous. Accommodation is probably offered more often to workers who want to continue working. Allowance rates are chosen by states on the basis of federal policy and local choices and probably in part on the health condition of workers in the state. Therefore, our estimates are upper bounds of these policy effects. Still, we believe we provide evidence that the social environment faced by workers with work-limiting health conditions can significantly influence their decision to apply for DI benefits, holding their specific health conditions constant. 相似文献
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A Linear Poisson Autoregressive Model: The Poisson AR(p) Model 总被引:1,自引:0,他引:1
Time series of event counts are common in political scienceand other social science applications. Presently, there arefew satisfactory methods for identifying the dynamics in suchdata and accounting for the dynamic processes in event countsregression. We address this issue by building on earlier workfor persistent event counts in the Poisson exponentially weightedmoving-average model (PEWMA) of Brandt et al. (American Journalof Political Science 44(4):823843, 2000). We developan alternative model for stationary mean reverting data, thePoisson autoregressive model of order p, or PAR(p) model. Issuesof identification and model selection are also considered. Wethen evaluate the properties of this model and present bothMonte Carlo evidence and applications to illustrate. 相似文献
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