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   15799篇
  免费   1416篇
  国内免费   12篇
  2023年   66篇
  2022年   110篇
  2021年   280篇
  2020年   123篇
  2019年   178篇
  2018年   246篇
  2017年   200篇
  2016年   345篇
  2015年   593篇
  2014年   711篇
  2013年   941篇
  2012年   1053篇
  2011年   1105篇
  2010年   687篇
  2009年   608篇
  2008年   919篇
  2007年   974篇
  2006年   870篇
  2005年   812篇
  2004年   803篇
  2003年   779篇
  2002年   697篇
  2001年   275篇
  2000年   220篇
  1999年   254篇
  1998年   242篇
  1997年   162篇
  1996年   146篇
  1995年   157篇
  1994年   154篇
  1993年   151篇
  1992年   180篇
  1991年   125篇
  1990年   171篇
  1989年   126篇
  1988年   121篇
  1987年   113篇
  1986年   97篇
  1985年   92篇
  1984年   86篇
  1983年   85篇
  1982年   80篇
  1981年   83篇
  1980年   90篇
  1979年   88篇
  1977年   64篇
  1976年   65篇
  1974年   55篇
  1973年   49篇
  1971年   47篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Hepatitis C virus (HCV) is a major cause of liver disease worldwide and HCV infection represents a major health problem. HCV associates with host lipoproteins forming host/viral hybrid complexes termed lipoviral particles. Apolipoprotein E (apoE) is a lipoprotein component that interacts with heparan sulfate proteoglycans (HSPG) to mediate hepatic lipoprotein uptake, and may likewise mediate HCV entry. We sought to define the functional regions of apoE with an aim to identify critical apoE binding partners involved in HCV infection. Using adenoviral vectors and siRNA to modulate apoE expression we show a direct correlation of apoE expression and HCV infectivity, whereas no correlation exists with viral protein expression. Mutating the HSPG binding domain (HSPG-BD) of apoE revealed key residues that are critical for mediating HCV infection. Furthermore, a novel synthetic peptide that mimics apoE’s HSPG-BD directly and competitively inhibits HCV infection. Genetic knockdown of the HSPG proteins syndecan (SDC) 1 and 4 revealed that SDC4 principally mediates HCV entry. Our data demonstrate that HCV uses apoE-SDC4 interactions to enter hepatoma cells and establish infection. Targeting apoE-SDC interactions could be an alternative strategy for blocking HCV entry, a critical step in maintaining chronic HCV infection.  相似文献   
32.
33.
34.
35.
36.
Abstract Pupae and mature larvae of the Australian ceratocanthid beetle, Cyphopisthes descarpentriesi Paulian 1977, are described and extensively illustrated. This is the sixth species of the family for which immature stages are known and the first from the Australian region. Unlike other ceratocanthid larvae described before, those of Cyphopisthes Gestro lack stridulatory teeth on the middle and hind legs and any trace of a frontoclypeal suture on the cranium. Reduced one-segmented labial palpi in Cyphopisthes are unique in Scarabaeoidea. Monophyly of the family is not corroborated by larval characters. Absence of spiracular closing apparatus in larvae is reported in the family for the first time. Like pupae of Ceratocanthus White and Germarostes Paulian, those of Cyphopisthes have thoracic projections, but their shape and location are different. Spiracles are found on abdominal segments 2−4 of pupa; that on segment 2 differs in colour and location from the others.  相似文献   
37.
38.
Decapod crustaceans are relatively widespread in Jurassic deposits of Europe and a small number have been collected from the north-east of France. A new fossil of a macrurous decapod assigned to Eryma burgundiaca sp. nov., an erymid lobster, is described from this area and comparisons are made with closely allied species from Europe. Probable pagurid anomurous decapods are represented by Orhomalus magnificus sp. nov., Palaeopagurus acutus sp. nov. and Palaeopagurus neraudeaui sp. nov. No brachyurous decapods are presently known from the fauna. Based on the associated ammonites, the material is considered to be Callovian in age.  相似文献   
39.
Old World pitcher plants (Nepenthes spp., Nepenthaceae) trapand digest invertebrate prey to derive nutrients, primarilynitrogen (N). In the majority of lowland Nepenthes species studiedto date, ants (Hymenoptera, Formicidae) are numerically thedominant prey taxon. Nepenthes albomarginata is unusual in showingan apparent bias towards the capture of termites (Isoptera).We tested the hypothesis that N. albomarginata derives N fromtermite capture, by comparison of foliar stable N isotope abundance(  相似文献   
40.
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