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   902篇
  免费   61篇
  国内免费   33篇
  2024年   1篇
  2023年   6篇
  2022年   12篇
  2021年   31篇
  2020年   19篇
  2019年   29篇
  2018年   31篇
  2017年   46篇
  2016年   57篇
  2015年   42篇
  2014年   56篇
  2013年   114篇
  2012年   30篇
  2011年   32篇
  2010年   24篇
  2009年   49篇
  2008年   29篇
  2007年   44篇
  2006年   31篇
  2005年   30篇
  2004年   29篇
  2003年   29篇
  2002年   19篇
  2001年   25篇
  2000年   11篇
  1999年   14篇
  1998年   11篇
  1997年   16篇
  1996年   11篇
  1995年   10篇
  1994年   13篇
  1993年   11篇
  1992年   5篇
  1991年   10篇
  1990年   4篇
  1989年   9篇
  1988年   9篇
  1987年   2篇
  1986年   13篇
  1985年   12篇
  1984年   5篇
  1983年   2篇
  1982年   1篇
  1981年   4篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1975年   1篇
  1972年   1篇
排序方式: 共有996条查询结果,搜索用时 189 毫秒
41.
This paper contextualizes racial and ethnic identities in shaping African women’s work lives in the USA. While the literature on black immigrant groups has posited that ethnic identities are often deployed to shield black immigrants from racism, my findings indicate that for a group of African women, their racial and ethnic identities are viewed as potential sources of discrimination. As black immigrant women from middle-class backgrounds in their home countries, they also articulate experiences with racism and downward social and occupational mobility. Accounting for how race and ethnicity intersect in the lives of black immigrant groups can nuance our understanding of racial identities and highlight diversity in experiences among national and regional groups. Focusing on particular health-care settings further suggests the importance of professional contexts in shaping the identity formations of recent black immigrants.  相似文献   
42.
Genealogy, or the study of one's ancestral patri-lineage, has a long and esteemed pedigree in French Canadian and Québécois history. From Cyprien Tanguay's late-nineteenth-century encyclopedias to René Jetté's updated versions more than a century later, genealogy has been an important component of French Canadian nationalisms. Tracing one's ancestry back to the early St. Lawrence settlement in the seventeenth century has provided Québécois subjects with opportune political and social capital with which to make territorial and national claims legitimate. Through a case study approach, I explain how genealogy provides the grounds upon which Québécois and French subjects remember a shared past. Specifically, I examine a variety of sites of memory in the French countryside, including a museum that relies on ‘genealogics’ to call the French Canadian Québécois back to its roots. As such, I demonstrate how the biological, read as a contemporary articulation of Balibar's notion of the racial supplément necessary to nation building, travels across the Atlantic.  相似文献   
43.
In this paper we bring together the literatures on frame analysis, the meaning of race and campus racial climate to analyse the race frames – lenses through which individuals understand the role of race in society – held by white students attending elite US universities. For most, the elite university experience coincides with a strengthening or emergence of the diversity frame, which emphasizes the positive benefits of cultural diversity. Still, many also hold a colour-blind frame, which sees race groups as equivalent and racial identities as insignificant. We highlight the ambivalence that these divergent frames create for student perspectives on affirmative action and interracial contact on campus. Our findings demonstrate the mutability of race frames. We also highlight the impact that institutions may have on individuals' race frames. The paper is based on in-depth interviews with forty-seven US-born white undergraduates attending Brown University and Harvard University.  相似文献   
44.
Different patterns of development can influence the strength and direction of selection of a trait. Here, it is shown how this may be the case for asexual reproduction in which eggs (animals) or spores (plants) inherit the maternal chromosome number through a precursor cell undergoing an endoduplication of its chromosomes prior to meiotic reduction. Asexuality involving premeiotic endoduplication (APE) has a wide but uneven distribution among animals and plants. It is argued that different patterns of egg and spore production and differences in when endoduplication occurs, together with differences in breeding structure (dioecious vs. hermaphroditic) and reproductive strategy (e.g. spawning vs. vivipary), can result in APE being associated with fecundity costs that can result in an overall cost of sex or in an overall cost of asex or in APE being selectively neutral relative to sex. There is a lack of a close correlation between the taxonomic distribution of APE and its potential costs and benefits however, possible causes of which are explored. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 487–495.  相似文献   
45.
The epidemiology of vector transmitted plant diseases is highly influenced by dispersal and the host‐plant range of the vector. Widening the vector's host range may increase transmission potential, whereas specialization may induce specific disease cycles. The process leading to a vector's host shift and its epidemiological outcome is therefore embedded in the frameworks of sympatric evolution vs. immigration of preadapted populations. In this study, we analyse whether a host shift of the stolbur phytoplasma vector, Hyalesthes obsoletus from field bindweed to stinging nettle in its northern distribution range evolved sympatrically or by immigration. The exploitation of stinging nettle has led to outbreaks of the grapevine disease bois noir caused by a stinging nettle‐specific phytoplasma strain. Microsatellite data from populations from northern and ancestral ranges provide strong evidence for sympatric host‐race evolution in the northern range: Host‐plant associated populations were significantly differentiated among syntopic sites (0.054 < FHT < 0.098) and constant over 5 years. While gene flow was asymmetric from the old into the predicted new host race, which had significantly reduced genetic diversity, the genetic identity between syntopic host‐race populations in the northern range was higher than between these populations and syntopic populations in ancestral ranges, where there was no evidence for genetic host races. Although immigration was detected in the northern field bindweed population, it cannot explain host‐race diversification but suggests the introduction of a stinging nettle‐specific phytoplasma strain by plant‐unspecific vectors. The evolution of host races in the northern range has led to specific vector‐based bois noir disease cycles.  相似文献   
46.
Caffeine (1,3,7-trimethixanthine) is a typical purine alkaloid produced in more than 80 plant species. Its biological role is considered to strengthen plant''s defense capabilities, directly as a toxicant to biotic attackers (allelopathy) and indirectly as an activator of defense system (priming). Caffeine is actively secreted into rhizosphere through primary root, and possibly affects the structure of microbe community nearby. The fungal community in coffee plant rhizosphere is enriched with particular species, including Trichoderma family, a mycoparasite that attacks and kills phytopathogens by coiling and destroying their hyphae. In the present study, the caffeine response of 8 filamentous fungi, 4 mycoparasitic Trichoderma, and 4 prey phytopathogens, was examined. Results showed that allelopathic effect of caffeine on fungal growth and development was differential, being stronger on pathogens than on Trichoderma species. Upon confronting, the prey immediately ceased the growth, whereas the predator continued to grow, indicating active mycoparasitism to have occurred. Caffeine enhanced mycoparasitism up to 1.7-fold. Caffeine thus functions in a double-track manner against fungal pathogens: first by direct suppression of growth and development, and second by assisting their natural enemy. These observations suggest that caffeine is a powerful weapon in the arms race between plants and pathogens by fostering enemy''s enemy, and we propose the idea of "caffeine fostering" as the third role of caffeine.  相似文献   
47.
48.
ABSTRACT

In this review essay, I place The Asian American Achievement Paradox, by Jennifer Lee and Min Zhou within a broad framework that reaches beyond immigration studies. I consider the book’s main contributions surrounding immigrant hyper-selectivity and stereotype promise in relation to class background, noting how the book makes an important contribution to our understanding of variations in educational achievement within and among ethno-racial groups. I note the relationship between stereotype promise and Robert K. Merton’s classic understanding of ‘self-fulfilling prophecy’. Finally, I draw attention to the way in which race and culture have been conflated thus creating new intellectual challenges for those interested in reaching greater levels of precision in analysis.  相似文献   
49.
ABSTRACT

The authors’ ‘new theoretical framework’ rests on their acceptance of ordinary language constructs. This leads them to an essentialized conception of race. It is not a true theory.  相似文献   
50.
ABSTRACT

Emirbayer and Desmond’s THE RACIAL ORDER is a heroic but ultimately quixotic effort. The work relies upon an attempted synthesis of Deweyan pragmatism and Bourdieuian social capital theory. Emirbayer and Desmond deploy an uneasy combination of approaches, insisting upon ‘reflexivity’ in sociological study of race and racism (the pragmatism dimension), and crafting a dubious taxonomy of sociological ‘fields’ where racial conflict takes shape, and in which sociologists study race as well (the social capital dimension). A chapter on ‘racial reconstruction’ proposes to apply their understanding to concrete political struggles, in pursuit of an augmented ‘racial democracy’. While the book is tremendously erudite theoretically and provides a valuable literature review, it does not advance racial theory very much. The authors are distracted by Bourdieu’s scientism and obsession with classification. Although ‘racial order’ is revealed to be a chimera, there is still much to be learned here.  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