全文获取类型
收费全文 | 2095篇 |
免费 | 276篇 |
国内免费 | 2篇 |
出版年
2023年 | 18篇 |
2022年 | 47篇 |
2021年 | 79篇 |
2020年 | 44篇 |
2019年 | 61篇 |
2018年 | 62篇 |
2017年 | 40篇 |
2016年 | 91篇 |
2015年 | 107篇 |
2014年 | 112篇 |
2013年 | 144篇 |
2012年 | 174篇 |
2011年 | 169篇 |
2010年 | 93篇 |
2009年 | 77篇 |
2008年 | 94篇 |
2007年 | 67篇 |
2006年 | 66篇 |
2005年 | 78篇 |
2004年 | 68篇 |
2003年 | 43篇 |
2002年 | 53篇 |
2001年 | 41篇 |
2000年 | 31篇 |
1999年 | 30篇 |
1998年 | 21篇 |
1997年 | 14篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 19篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 20篇 |
1975年 | 13篇 |
1973年 | 18篇 |
1969年 | 11篇 |
1967年 | 11篇 |
1966年 | 13篇 |
排序方式: 共有2373条查询结果,搜索用时 0 毫秒
101.
102.
Katharine Tyler 《Ethnic and racial studies》2013,36(2):290-309
In this article I examine the formation of white working-class racialized discourses in a former coal-mining town in Leicestershire. I draw upon my ethnographic research in the area to explore the conditions in which young white adults confront, challenge and question what they perceive to be others’ conventional racist attitudes and beliefs, for example, the racist attitudes of members of their nuclear and extended families, friends and acquaintances. I argue that it is vital to examine these “moments of questioning” if white hegemony in predominantly working-class areas is to be understood. 相似文献
103.
Colin A. Chapman Tyler R. Bonnell Jan F. Gogarten Joanna E. Lambert Patrick A. Omeja Dennis Twinomugisha Michael D. Wasserman Jessica M. Rothman 《International journal of primatology》2013,34(1):1-14
Animals can play important roles in structuring the plant communities in which they live. Some species are particularly influential in that they modify the physical environment by changing, maintaining, and/or creating new habitats; the term ecosystem engineer has been used to describe such species. We here assess the two major foraging strategies of primates, frugivory and folivory, in terms of the potential for primates to function as ecosystem engineers. We argue that whereas the role of primates as seed dispersers has received a great deal of attention, the potential role that folivorous primates play in structuring their environment through herbivory has received much less attention. Further, while quantifying if frugivorous primates are ecosystem engineers through their seed dispersal has proved very difficult, it is not as difficult to ascertain whether folivorous primates are ecosystem engineers. We document situations in which folivorous primates act as ecosystem engineers by 1) eating the leaves and/or bark of trees to the extent that they kill trees, 2) feeding on trees to the degree that they slow their growth relative to nonpreferred tree species, 3) eating the flowers of species to the extent that it does not set fruit, or 4) feeding on plants in such a way as to increase their productivity and abundance. Because evidence from the literature is very limited, where possible we present new evidence of these processes from the colobus monkeys at our long-term field site in Kibale National Park, Uganda. We conclude by discussing promising research programs that could be established to refine our understanding of the role primates play in shaping the structure of plant communities, especially tropical forests. 相似文献
104.
Tyler Schwend Zhigang Jin Kai Jiang Brian J. Mitchell Jianhang Jia Jing Yang 《The Journal of biological chemistry》2013,288(45):32809-32820
105.
106.
107.
The characteristic feature of Lake Leake and Tooms Lake is their great similarity in physical and chemical limnology. This similarity extends to the plankton populations in general terms, both lakes being dominated by Cyclotella stelligera Cleve et Grun. and having few other species. Floristic differences are minimal. Despite this floristic similarity distinct differences exist in plankton periodicity, principally in that of Cyclotella stelligera. The extreme oligotrophy of the lakes, already suspected from their low nutrient levels, is confirmed by the extremely meagre standing crops. 相似文献
108.
Keith Clinch Douglas R. Crump Gary B. Evans Keith Z. Hazleton Jennifer M. Mason Vern L. Schramm Peter C. Tyler 《Bioorganic & medicinal chemistry》2013,21(17):5629-5646
The pathogenic protozoa responsible for malaria lack enzymes for the de novo synthesis of purines and rely on purine salvage from the host. In Plasmodium falciparum (Pf), hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT) converts hypoxanthine to inosine monophosphate and is essential for purine salvage making the enzyme an anti-malarial drug target. We have synthesized a number of simple acyclic aza-C-nucleosides and shown that some are potent inhibitors of Pf HGXPRT while showing excellent selectivity for the Pf versus the human enzyme. 相似文献
109.
110.
Theresa S. Betancourt Robert T. Brennan Patrick Vinck Tyler J. VanderWeele Dayo Spencer-Walters Joshua Jeong Adeyinka M. Akinsulure-Smith Phuong Pham 《PLoS medicine》2016,13(8)
BackgroundLittle attention has been paid to potential relationships between mental health, trauma, and personal exposures to Ebola virus disease (EVD) and health behaviors in post-conflict West Africa. We tested a conceptual model linking mental health and trauma to EVD risk behaviors and EVD prevention behaviors.ConclusionsIn post-conflict settings, past war trauma and mental health problems are associated with health behaviors related to combatting EVD. The associations between war trauma and both EVD risk behaviors and EVD prevention behaviors may be mediated through two key mental health variables: depression and PTSD symptoms. Considering the role of mental health in the prevention of disease transmission may help fight continuing and future Ebola outbreaks in post-conflict Sierra Leone. This sample is specific to Freetown and the Western Area and may not be representative of all of Sierra Leone. In addition, our main outcomes as well as personal EVD exposure, war exposures, and mental health predictors rely on self-report, and therefore raise the possibility of common methods bias. However, the findings of this study may be relevant for understanding dynamics related to EVD and mental health in other major capital cities in the EVD-affected countries of West Africa. 相似文献