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   93292篇
  免费   4053篇
  国内免费   8152篇
  105497篇
  2023年   851篇
  2022年   1369篇
  2021年   1691篇
  2020年   1817篇
  2019年   3153篇
  2018年   2189篇
  2017年   1821篇
  2016年   2240篇
  2015年   3413篇
  2014年   4734篇
  2013年   6397篇
  2012年   4108篇
  2011年   5614篇
  2010年   4109篇
  2009年   4207篇
  2008年   4546篇
  2007年   4783篇
  2006年   4291篇
  2005年   3760篇
  2004年   3216篇
  2003年   2886篇
  2002年   2509篇
  2001年   1970篇
  2000年   1768篇
  1999年   1771篇
  1998年   1673篇
  1997年   1453篇
  1996年   1331篇
  1995年   1524篇
  1994年   1463篇
  1993年   1341篇
  1992年   1345篇
  1991年   1134篇
  1990年   1029篇
  1989年   992篇
  1988年   926篇
  1987年   919篇
  1986年   623篇
  1985年   1075篇
  1984年   1465篇
  1983年   1047篇
  1982年   1395篇
  1981年   1011篇
  1980年   992篇
  1979年   946篇
  1978年   563篇
  1977年   453篇
  1976年   379篇
  1975年   283篇
  1973年   290篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Three species of interstitial Collembola in Entomobryidae were identified from South Korean coast. One of them, Sinella (Coecobrya) maritima, is new to science. So far 21 halophilous species in 10 families of Collembola, including the new species in this paper, were reported from the Korean peninsula.  相似文献   
202.
203.
204.
This review essay of Across Borders: Beadwork in Iroquois Life focuses on the display of beadwork as a cultural practice that has evolved significantly throughout its history while remaining central to Iroquois identity. The exhibition draws on historical documentation, objects, and imagery that depict the varied uses of beadwork as ritual objects, sources of income, markers of identity, and as works of art. The content and narrative for the display was developed through a broad collaboration between curators, scholars, artists, and members of two Iroquois communities. The changing and continued importance of beadwork is reflected in the adaptation of materials and styles for different forms of production and use. Across Borders places Iroquois beadwork in a broad context while concentrating on specific forms and meanings that are attached to beadwork, whether created in community gatherings or by individual artists.  相似文献   
205.
206.
207.
This article briefly reviews the classical cell cycle studies using oocytes and zygotes of mainly amphibians in the past century. The discussions are focused on the investigations into the cytoplasmic factors that regulate meiosis during oocyte maturation and the initiation of mitosis during fertilisation, which were carried out in the author's lab between 1967 and 1987. This chronicle traces the development of the problems and the direction in which their solutions were attempted in the course of these investigations. The author tries to answer the following questions: why he decided to study oocyte maturation, how he discovered progesterone as a maturation-inducing hormone, how he discovered and characterised the cytoplasmic regulators of the cell cycle, Maturation-Promoting Factor (MPF) and Cyto-Static Factor (CSF), and how he invented the method of observing cell cycle processes in a cytoplasmic extract in vitro.  相似文献   
208.
Top predators from the northern sub-polar and polar areas exhibit high cadmium concentrations in their tissues. In the aim to reveal possible adverse effects, samples of five Atlantic white-sided dolphins Lagenorhyncusacutus have been collected on the occasion of the drive fishery in the Faroe Islands, for ultrastructural investigations and energy dispersive X-ray microanalyses. Cadmium concentrations were less than the limit of detection in both immature individuals and ranged from 22.7 to 31.1 μg g?1 wet weight in the mature individuals. Two individuals with the highest cadmium concentrations exhibited electron dense mineral concretions in the basal membranes of the proximal tubules. They are spherocrystals made up of numerous strata mineral deposit of calcium and phosphorus together with cadmium. Cadmium has been detected with a molar ratio of Ca:Cd of 10:1 in the middle of these concretions. To our knowledge, this is the first report of such granules in a wild vertebrate. The role of these granules in the detoxification of the metal and the possible pathological effects are considered.  相似文献   
209.
210.
It is difficult to completely understand the life history of an intellectual excluding an understanding of his family upbringing and formative years. Family upbringing and childhood environment, often the less known part of a life history, play crucial roles in shaping the ideas and values individuals espouse in their adult life. Notwithstanding, this paper is not concerned with Don C. Ohadike’s childhood. It rather focuses on the professional career of our able historian – that is the part of his life as revealed by his most outstanding published writings. Ohadike’s published works contain a wellspring of idioms that tell much about his values, quality of mind, and his mission as an African historian. Ohadike was a humanist, an African patriot, and a nationalist crusader. His entire philosophy centered on safeguarding his African identity in an emergent world of cultural imperialism. The funds for this research were provided by a NEH-funded fellowship at the Schomburg Center, New York in the Spring of 2007. I owe a lot of gratitude to Professor John McLeod and Dean Blaine Hudson for granting me the extra incentives to pursue my research in New York. While all errors and misinterpretations are mine, I wish to thank the editors and anonymous reviewers for Journal of Dialectical Anthropology for their perspective comments and suggestions on earlier drafts of this paper.  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