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   7316篇
  免费   157篇
各国政治   386篇
工人农民   192篇
世界政治   467篇
外交国际关系   283篇
法律   4614篇
中国共产党   1篇
中国政治   19篇
政治理论   1418篇
综合类   93篇
  2020年   61篇
  2019年   83篇
  2018年   122篇
  2017年   132篇
  2016年   154篇
  2015年   109篇
  2014年   128篇
  2013年   777篇
  2012年   199篇
  2011年   195篇
  2010年   157篇
  2009年   162篇
  2008年   194篇
  2007年   175篇
  2006年   186篇
  2005年   147篇
  2004年   154篇
  2003年   157篇
  2002年   161篇
  2001年   303篇
  2000年   276篇
  1999年   220篇
  1998年   82篇
  1997年   104篇
  1996年   79篇
  1995年   81篇
  1994年   90篇
  1993年   79篇
  1992年   156篇
  1991年   176篇
  1990年   155篇
  1989年   171篇
  1988年   147篇
  1987年   141篇
  1986年   163篇
  1985年   128篇
  1984年   124篇
  1983年   129篇
  1982年   78篇
  1981年   78篇
  1980年   58篇
  1979年   110篇
  1978年   63篇
  1977年   61篇
  1976年   56篇
  1975年   66篇
  1974年   82篇
  1973年   76篇
  1972年   67篇
  1971年   60篇
排序方式: 共有7473条查询结果,搜索用时 15 毫秒
181.
The profound socio-political crisis in El Salvador fully revealed itself in the events of 1979 and 1980, developing into an open civil war beginning on 10 January 1981. The conflict generated a series of profound changes in the social structure of the country (Segundo Montes, 1988:107).  相似文献   
182.
African agriculture is often dominated by smallholder farms composed of multiple plots. In policy circles it is often assumed that fragmentation coupled with small farm size is an impediment to increasing yields and thus decreasing poverty and food insecurity. There also exists an influential literature that explores the inverse relationship between farm size and yield. While there are many studies internationally, few have been conducted in Africa. Using an Ethiopian national survey, we explore the relationship between yield, farm size and fragmentation. We find an inverse relationship between farm size and yield, and a positive association between yield and land fragmentation.  相似文献   
183.
This paper analyzes how peasant movements scale up agroecology. It specifically examines Zero Budget Natural Farming (ZBNF), a grassroots peasant agroecology movement in Karnataka, India. ZBNF ends reliance on purchased inputs and loans for farming, positioning itself as a solution to extreme indebtedness and suicides among Indian farmers. The ZBNF movement has achieved massive scale not only because of effective farming practices, but because of a social movement dynamic – motivating members through discourse, mobilizing resources from allies, self-organized pedagogical activities, charismatic and local leadership, and generating a spirit of volunteerism among its members. This paper was produced as part of a self-study process in La Via Campesina, the global peasant movement.  相似文献   
184.
A breath alcohol profile is generated as a continuous function of time while a person is providing a breath sample. This paper describes a data acquisition system which samples breath alcohol concentrations at discrete intervals during exhalation. The data are stored on disk for later analysis. It is shown that the area under the profile curve for samples preceded by breath-holding is significantly larger than when breathing is normal prior to sample provision (p less than 0.001). The differences between the breath alcohol concentration measurements are also statistically significant (p less than 0.001) for the two different breathing patterns prior to breath exhalation. These results have physiological implications and suggest another means of evaluating breath alcohol profiles.  相似文献   
185.
186.
In order to establish pathological evidence in dermis for distinguishing between sequelae of electrical torture and those of other superficial injuries, the skin of eleven fully anaesthetized Danish Landrace pigs have been exposed to heat and electrical energy from either 50 Hz alternating current (a.c.) or direct current (d.c.) via 12 mm large contact knobs or via a pointed 0.5 mm large electrode (only 50 Hz a.c.). The lesions have been examined from 1 to 126 days after the injury. While heat lesions exposed to energy lower than 60 joule only gave minor changes, heat lesions exposed to more than 60 joule showed changes in both collagen fibres (basophilic or eosinophilic fibres without any birefringence or coarse cross-striation in polarized light, respectively) and dermal cells (granular cytoplasm). Areas exposed to 50 Hz a.c. via 0.5 mm. electrode showed basophilic collagen fibres and in a few biopsies on day 7 calcium salts on collagen fibres. Using 12 mm large electrodes the changes were minor, but basophilic and eosinophilic collagen fibres with no birefringence or with fine/coarse cross-striation respectively were seen. Even cells with 'vesicular nuclei' were seen on day 1 and 2 after the injury. The changes in the anode area showed resemblance to that of heat lesions (basophilic collagen fibres). Eosinophilic collagen fibres with fine densely spaced cross-striation in polarized light and 'vesicular nuclei' as well as collagen fibres with calcium salts were seen in the cathode lesions. It is concluded that the dermal changes in the cathode area are specific for electrical injury from day 1 to 14. However, earlier studies have demonstrated dermal changes specific for electrical injury at day 0 and the presence of calcified collagen fibres up to 2 months after injury. The dermal changes in anode lesions were non specific and could not be differentiated from those found in heat lesions. Alternating current lesions (50 Hz) were specific from day 1 to day 7, when the pointed electrode was used, but only in a few days when the energy was transferred via the 12-mm electrodes.  相似文献   
187.
In the second of our two-part review of Vladimir Lenin’s 1917 study of American agriculture, we extrapolate upon Alexander Chayanov’s neoliberal appropriation, Giovanni Arrighi’s treatment of partial proletarianization, the propagandistic “family farm,” agribusiness’s fluctuating territorial embeddedness, agriculture as an industry, and land and rent as commodities themselves. We finish by deploying Lenin’s alternate history as a Benjaminian détournement in the face of what now appear insurmountable obstacles. An alternate food future is not only possible, it is already underway.  相似文献   
188.
Policymakers have actively pursued urban renewal and dispersal programs to deconcentrate poverty in urban neighborhoods. Relocation strategies lead to new housing opportunities and may encourage employment opportunities for relocated residents if resourceful contacts and job information become more easily available after the move. This study provides an innovative evaluation of the early impacts of involuntary relocation programs in the Netherlands on the housing careers, earnings and employment rates of forced relocatees. It establishes a quasi-experimental design by employing unique longitudinal individual-level population registry data from Statistics Netherlands: forced relocatees are tracked and matched to a control group consisting of similar residents that were not forced to move. A difference-in-difference design shows that forced relocatees are living in less deprived neighborhoods after the move. However, we find no conclusive evidence that this upgrade in housing leads to more socioeconomic opportunities for the forced relocatees.  相似文献   
189.
190.
Are internalizing and externalizing behavior problems interrelated via mutually reinforcing relationships (with each behavior leading to increases over time in levels of the other behavior) or mutually suppressing relationships (with each behavior leading to decreases over time in levels of the other behavior)? Past research on the directionality of these relationships has led to ambiguous results, particularly in adolescence. Furthermore, the extent to which prior results will generalize to adolescents with low levels of cognitive abilities remains unknown. This second limit is particularly important, given that these adolescents are known to present higher levels of externalizing and internalizing behaviors than their peers with average-to-high levels of cognitive abilities, and that the mechanisms involved in the reciprocal relationships between these two types of behaviors may differ across both populations. This study examines the directionality of the longitudinal relationships between externalizing and internalizing behavior problems as rated by teachers across three measurement waves (corresponding to Grades 8–10) in matched samples of 138 adolescents (34.78?% girls) with low levels of cognitive abilities and 556 adolescents (44.88?% girls) with average-to-high levels of cognitive abilities. The results showed that the measurement structure was fully equivalent across time periods and groups of adolescents, revealing high levels of developmental stability in both types of problems, and moderately high levels of cross-sectional associations. Levels of both internalizing and externalizing behaviors were higher among adolescents with low levels of cognitive abilities relative to those with average-to-high levels of cognitive abilities. Finally, the predictive analyses revealed negative reciprocal longitudinal relationships (i.e., mutually suppressing relationships) between externalizing and internalizing problems, a result that was replicated within samples of adolescents with low, and average-to-high levels of cognitive ability.  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