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   4748篇
  免费   166篇
各国政治   232篇
工人农民   182篇
世界政治   339篇
外交国际关系   126篇
法律   2990篇
中国共产党   1篇
中国政治   28篇
政治理论   985篇
综合类   31篇
  2020年   60篇
  2019年   68篇
  2018年   85篇
  2017年   104篇
  2016年   104篇
  2015年   94篇
  2014年   87篇
  2013年   489篇
  2012年   130篇
  2011年   120篇
  2010年   106篇
  2009年   104篇
  2008年   134篇
  2007年   129篇
  2006年   126篇
  2005年   122篇
  2004年   126篇
  2003年   120篇
  2002年   112篇
  2001年   181篇
  2000年   170篇
  1999年   128篇
  1998年   68篇
  1997年   52篇
  1996年   43篇
  1995年   56篇
  1994年   50篇
  1993年   47篇
  1992年   91篇
  1991年   88篇
  1990年   106篇
  1989年   88篇
  1988年   83篇
  1987年   83篇
  1986年   104篇
  1985年   109篇
  1984年   76篇
  1983年   78篇
  1982年   50篇
  1981年   47篇
  1980年   44篇
  1979年   48篇
  1978年   55篇
  1976年   35篇
  1975年   46篇
  1974年   61篇
  1973年   55篇
  1972年   42篇
  1970年   34篇
  1969年   41篇
排序方式: 共有4914条查询结果,搜索用时 15 毫秒
901.
This paper applies Gini and concentration coefficient decomposition as well as the Foster-Greer-Thorbecke poverty index and the Stark-Yitzhaki welfare index to new data from four villages in Burkina Faso, to compare the marginal effects of remittances from intercontinental and intra-African migration on inequality, poverty and social welfare. Evidence is found that intra-African remittances reduce inequality while intercontinental remittances have the opposite effect. Also, it is found that although remittances from intercontinental migration are associated with much lower incidence, depth and severity of poverty, the marginal impact of remittances from this form of migration on social welfare is limited because recipients do not include the rural poor.  相似文献   
902.
Using data from the Philippines, we study the impact of mobile phones on the prices agricultural producers receive for their cash crop. We first look at the impact on price of mobile phone ownership at the household level. Because this masks a considerable amount of heterogeneity, we then look at the impact on price of the intrahousehold allocation of mobile phones. We find that whether the household owns a mobile phone has no impact on price, but whether a farmer or spouse owns a mobile phone is associated with a 5- to 8-per cent increase in price.  相似文献   
903.
The rapid spread of modern supply chains in developing countries is profoundly changing the way food is produced and traded. In this article we examine gender issues related to this change. We conceptualise various mechanisms through which women are directly affected, we review existing empirical evidence and add new survey-based evidence. Our results suggest that, although modern supply chains are gendered, their growth is associated with reduced gender inequalities in rural areas. We find that women benefit more and more directly from large-scale estate production and agro-industrial processing, and the creation of employment in these modern agro-industries than from smallholder contract-farming.  相似文献   
904.
This study uses pairing of Mexican‐owned manufacturing firms and firms with direct United States investment, to examine the effects of ownership structure on firms’ performance and sources of technology. Results suggest that in terms of profitability, growth and export performance the Mexican firms were competing successfully during the period 1966–73. Furthermore, the basis for this strong posture by the Mexican manufacturers was not due to a heavy reliance on foreign technology imported through formal channels, but rather is linked with internal innovative activity and the use of domestic consultants.  相似文献   
905.

This article focuses on the measurement of embodied technological change. It develops the core-machinery approach to capital measurement, which is based on an engineering perspective on technological change. Using technical characteristics of different types of machinery, technical progress in the capital stock can be decomposed into incremental innovation in existing machinery and radical shifts to new technologies. The usefulness of this approach is illustrated by an analysis of embodied technological change in the Indonesian spinning and weaving industries. The core-machinery measure is compared with more traditional measures of the capital stock which are based on price information. Strengths, weaknesses and relevance of the new measure are discussed.  相似文献   
906.
This article uses household data from Nepal's two major populated regions (and 27 of 59 districts within those regions) to examine fuelwood consumption and production. In contrast with a purely market assessment, household analysis includes production which is consumed in the producing household. The household regressions yield coefficients and elasticities that are very different from and more reliable than a comparable assessment of market demand and supply. Household results generally support the hypotheses that expenditures on fuelwood are a small share of total household activity and that fuelwood is not sufficiently scarce to alter household behaviour. Fuelwood is sufficiently scarce, however, to alter behaviour for those households in the hill region that do not participate in market exchange. These households may be the best targets for public market interventions designed to alter fuelwood supply and deforestation.  相似文献   
907.
Fibers are a commonly encountered evidence type and fiber comparisons are routinely conducted. When the characteristics of questioned and known fibers correspond, the probative value is limited because the characteristics compared are determined by their manufacture. It would be valuable to test the hypothesis that questioned fibers originated from a specific carpet. One means of testing this is to analyze fine particles on the fibers. A procedure was developed for removing adhering particles from fibers and preparing them for scanning electron microscopy/ energy dispersive X‐ray spectrometry (SEM/EDS) analysis. The efficacy of several fluids (acetone, ethanol, hexanes, aqueous ethanol, aqueous sodium hexametaphosphate) and agitation methods (sonication and vortexing) for removing particles from fibers was evaluated. The most effective method evaluated was sonication in ethanol for 10 min. The recovered particles were filtered onto a polycarbonate filter and analyzed by automated SEM/EDS analysis to generate data on the particle assemblage. This method makes possible future research to test the within‐item and between‐item variability of particle assemblages on fibers.  相似文献   
908.
Raman spectroscopy has found increased use in the forensic controlled substances laboratory in recent years due to its rapid and nondestructive analysis capabilities. Here, Raman spectroscopy as a screening test for methamphetamine in clandestine laboratory liquid samples is discussed as a way to improve the efficiency of a laboratory by identifying the most probative samples for further workup among multiple samples submitted for analysis. Solutions of methamphetamine in ethanol, diethyl ether, and Coleman fuel were prepared in concentrations ranging from 0.5% to 10% w/v, and Raman spectra of each were collected. A concentration‐dependant Raman peak was observed at 1003 per cm in each solution in 4% w/v and greater solutions. Case samples were analyzed and also found to reliably contain this diagnostic peak when methamphetamine was present. The use of this diagnostic indicator can save the forensic controlled substances laboratory time and materials when analyzing clandestine laboratory liquid submissions.  相似文献   
909.
The majority of microfluidic devices used as a platform for low‐cost, rapid DNA analysis are glass devices; however, microchip fabrication in glass is costly and laborious, enhancing the interest in polymeric substrates, such as poly (methyl methacrylate) (PMMA), as an inexpensive alternative. Here, we report amplification in PMMA polymerase chain reaction (PCR) microchips providing full short tandem repeat profiles (16 of 16 loci) in 30–40 min, with peak height ratios and stutter percentages that meet literature threshold requirements. In addition, partial profiles (15 of 16 loci) were generated using an ultrafast PCR method in 17.1 min, representing a ~10‐fold reduction in reaction time as compared to current amplification methods. Finally, a multichamber device was demonstrated to simultaneously amplify one positive, one negative, and five individual samples in 39 min. Although there were instances of loci dropout, this device represents a first step toward a microfluidic system capable of amplifying more than one sample simultaneously.  相似文献   
910.
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