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   6790篇
  免费   1205篇
  国内免费   3536篇
  2024年   39篇
  2023年   236篇
  2022年   355篇
  2021年   407篇
  2020年   412篇
  2019年   441篇
  2018年   268篇
  2017年   287篇
  2016年   290篇
  2015年   415篇
  2014年   611篇
  2013年   526篇
  2012年   732篇
  2011年   667篇
  2010年   577篇
  2009年   590篇
  2008年   634篇
  2007年   621篇
  2006年   541篇
  2005年   486篇
  2004年   359篇
  2003年   309篇
  2002年   254篇
  2001年   255篇
  2000年   252篇
  1999年   166篇
  1998年   94篇
  1997年   80篇
  1996年   42篇
  1995年   44篇
  1994年   26篇
  1993年   25篇
  1992年   33篇
  1991年   37篇
  1990年   37篇
  1989年   49篇
  1988年   28篇
  1987年   28篇
  1986年   37篇
  1985年   22篇
  1984年   26篇
  1983年   19篇
  1982年   26篇
  1981年   14篇
  1980年   9篇
  1979年   9篇
  1978年   10篇
  1976年   8篇
  1973年   8篇
  1965年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
G. Morel  M. Fouillaud 《BioControl》1994,39(2):137-147
Bioassays were used to study the infectivity of cytoplasmic polyhedrosis viruses (CPVs), nuclear polyhedrosis viruses (NPVs) and entomopoxviruses (EPVs) contained in 16 nests of the paper waspPolistes hebraues F. in Réunion Island. Several virosis were propagated from 6 nest contents in 5 Lepidoptera:Catopsilia thauruma Saalmüller,Catopsilia florella F.,Callixena versicolora Mabille,Polydesma umbricola Boisduval andEagris sabadius Boisduval. Each of the previous species supported the development of one or two virosis and therefore, wasp nests must be considered as accumulating centres where infectivity of occluded entomoviruses is preserved. The accurate origin of the virosis propagated through bioassays was searched for using ecological investigations on similar natural diseases, REN analysis and a cross-transmission test onSpodoptera mauritia Boisduval. The nuclear polyhedrosis and one cytoplasmic polyhedrosis appearing in bioassays can be assigned respectively to viruses produced byC. thauruma andC. versicolora; the other virosis must be considered as developing in alternate or substitution hosts. Wasp nests could therefore be used to detect the presence of specific viruses in an environment and to collect new virus isolates.  相似文献   
2.
3.
Regenerative medicine is a burgeoning field that is important to combat challenging diseases and functional impairments. Compared with traditional cell therapies with evident shortcomings (e.g., cell suspension injection or tissue engineering with scaffolds), scaffold-free cell sheet technology enables transplanted cells to be grafted and fully maintain their viability on target sites. Clinical and experimental studies have advanced the application of cell sheet technology to numerous tissues and organs (e.g., liver, cornea and bone). However, previous reviews have failed to discuss vital aspects of this rapidly developing technology, and many new challenges are gradually emerging. This review aims to provide a comprehensive introduction to cell sheet technology from cell selection to the ultimate applications of cell sheets, and challenges and future visions are also described.  相似文献   
4.
5.
Poaching and habitat destruction in the Congo Basin threaten African great apes including the bonobo (Pan paniscus), chimpanzees (Pan troglodytes), and gorillas (Gorilla spp.) with extinction. One way to combat extinction is to reintroduce rescued and rehabilitated apes and repopulate native habitats. Reintroduction programs are only successful if they are supported by local populations. Ekolo ya Bonobo, located in Equateur province of the Democratic Republic of Congo (DRC), is the world's only reintroduction site for rehabilitated bonobos. Here we assess whether children, of the Ilonga‐Pôo, living adjacent to Ekolo ya Bonobo demonstrate more pro‐ape conservation attitudes than children living in, Kinshasa, the capital city. We examined children's attitudes toward great apes because children are typically the focus of conservation education programs. We used the Great Ape Attitude Questionnaire to test the Contact Hypothesis, which posits that proximity to great ape habitat influences pro‐conservation attitudes toward great apes. Ilonga‐Pôo children who live in closer contact with wild bonobos felt greater responsibility to protect great apes compared to those in Kinshasa who live outside the natural habitat of great apes. These results suggest that among participants in the DRC, spatial proximity to a species fosters a greater sense of responsibility to protect and conserve. These results have implications for the successful implementation of great ape reintroduction programs in the Congo Basin. The data analyzed in this study were collected in 2010 and therefore provide a baseline for longitudinal study of this reintroduction site.  相似文献   
6.
7.
8.
This article presents work carried out as part of the robot sécurisé d’assistance à la chirurgie endoscopique (Rosace) project (funding ANR TecSan06), involving both academic and clinical partners along with an industrial partner in charge of technology integration. The main subject is a lightweight and compact robot for assistance in the endoscopic surgery field. The goal of the project has been to improve then transfer on a medical-grade product some technologies initially developed by the two academic partners. These technologies are: a first prototype of a robotic endoscope holder, an original method for visual servoing based on instrument tracking and some work done on comanipulation concept which consists in synergic interaction between robot and user. In accordance with the initial goals, major improvements have been obtained on these three aspects of the project. Robotic architecture improvement has contributed to enhance robot's versatility while robot command has been made more efficient and simple to use thanks to instrument tracking and comanipulation. After this 3-year project, initial prototype has turned into a commercially available product integrating (or that will integrate in a few months) these new technologies.  相似文献   
9.
Inhibitory effect of myasthenic patients antibodies on alpha-bungarotoxin binding to the human acetylcholine receptor has been demonstrated by radioimmunoassay. By using decamethonium, an acetylcholine agonist, we have shown the existence of two antibody sub-groups reacting with the toxin-binding site: one sub-group is represented by antibodies which block the binding directly, the other by antibodies that inhibit the binding, only in the presence of decamethonium.  相似文献   
10.
This work was performed to test the efficacy of winter–spring control strategies against Rhipicephalus (Boophilus) microplus (Ixodida: Ixodidae) infestations on cattle in the area ecologically most favourable for the development of this tick in Argentina. Two control schemes using three and four annual applications of acaricides, respectively, were evaluated. Animals in Group 1 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, and fipronil on day 85. Animals in Group 2 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, flumethrin on day 85, and fipronil on day 114. Animals in Group 3 represented the control group. Both treatment schemes provided appropriate levels of efficacy against R. microplus and also prevented the occurrence of the major peak in the frequency of this tick in autumn. The two treatment schemes were similar in terms of efficacy and thus the addition of a fourth treatment does not seem to confer any further advantage. The results of this work indicate that these strategic control methods provide appropriate levels of control against R. microplus.  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