全文获取类型
收费全文 | 6329篇 |
免费 | 647篇 |
国内免费 | 3篇 |
出版年
2022年 | 39篇 |
2021年 | 76篇 |
2020年 | 43篇 |
2019年 | 58篇 |
2018年 | 79篇 |
2017年 | 83篇 |
2016年 | 124篇 |
2015年 | 192篇 |
2014年 | 214篇 |
2013年 | 289篇 |
2012年 | 343篇 |
2011年 | 333篇 |
2010年 | 219篇 |
2009年 | 191篇 |
2008年 | 315篇 |
2007年 | 292篇 |
2006年 | 283篇 |
2005年 | 267篇 |
2004年 | 266篇 |
2003年 | 238篇 |
2002年 | 237篇 |
2001年 | 162篇 |
2000年 | 126篇 |
1999年 | 129篇 |
1998年 | 78篇 |
1997年 | 77篇 |
1996年 | 80篇 |
1995年 | 82篇 |
1994年 | 60篇 |
1993年 | 69篇 |
1992年 | 106篇 |
1991年 | 103篇 |
1990年 | 106篇 |
1989年 | 81篇 |
1988年 | 67篇 |
1987年 | 90篇 |
1986年 | 70篇 |
1985年 | 79篇 |
1984年 | 85篇 |
1983年 | 89篇 |
1982年 | 72篇 |
1981年 | 62篇 |
1980年 | 51篇 |
1979年 | 70篇 |
1978年 | 65篇 |
1977年 | 68篇 |
1976年 | 49篇 |
1975年 | 44篇 |
1974年 | 63篇 |
1972年 | 45篇 |
排序方式: 共有6979条查询结果,搜索用时 203 毫秒
21.
Human RSV is one of the most prevalent viral pathogens of early childhood for which no vaccine is available. Herein we provide an analysis of RSV epitope data to examine its application to vaccine design and development. Our objective was to provide an overview of antigenic coverage, identify critical antibody and T cell determinants, and then analyze the cumulative RSV epitope data from the standpoint of functional responses using a combinational approach to characterize antigenic structure and epitope location. A review of the cumulative data revealed, not surprisingly, that the vast majority of epitopes have been defined for the two major surface antigens, F and G. Antibody and T cell determinants have been reported from multiple hosts, including those from human subjects following natural infection, however human data represent a minority of the data. A structural analysis of the major surface antigen, F, showed that the majority of epitopes defined for functional antibodies (neutralizing and/or protective) were either shown to bind pre-F or to be accessible in both pre- and post-F forms. This finding may have has implications for on-going vaccine design and development. These interpretations are in agreement with previous work and can be applied in the larger context of functional epitopes on the F protein. It is our hope that this work will provide the basis for further RSV-specific epitope discovery and investigation into the nature of antigen conformation in immunogenicity. 相似文献
22.
Chiara Tyndall Hansjo¨rg Lehnherr Ursula Sandmeier Eva Kulik & Thomas A. Bickle 《Molecular microbiology》1997,23(4):729-736
Eco R124I, Eco DXXI and Eco prrI are the known members of the type IC family of DNA restriction and modification systems. The first three are carried on large, conjugative plasmids, while Eco prrI is chromosomally encoded. The enzymes are coded by three genes, hsdR , hsdM and hsdS . Analysis of the DNA sequences upstream and downstream of the type IC hsd loci shows that all are highly homologous to each other and also to sequences present in the bacteriophage P1 genome. The upstream sequences include functional phd and doc genes, which encode an addiction system that stabilizes the P1 prophage state, and extend to and beyond pac , the site at which phage DNA packaging begins. Downstream of the hsd loci, P1 DNA sequences begin at exactly the same place for all of the systems. For Eco DXXI and Eco prrI the P1 homology extends for thousands of base pairs while for Eco R124I an IS 1 insertion and an associated deletion have removed most of the P1-homologous sequences. The significance of these results for the evolution of DNA restriction and modification systems is discussed. 相似文献
23.
24.
A light-weight nonmagnetic, nonconductive instrument has been devised for use with magnetic resonance imaging, computerized tomography, and digital subtraction imaging for work in the field of epilepsy, brain tumors and vascular lesions. The apparatus' main characteristic is its ability to use optionally either the lateral orthogonal or the spherical-radial approach. 相似文献
25.
26.
Netherlands Heart Journal - 相似文献
27.
28.
Anton Pauw Sunshine A. Van Bael Halton A. Peters Steven D. Allison José L. C. Camargo Miguel Cifuentes-Jara Aurlstela Conserva Teresa Garcia Restom Tamara Heartsill-Scalley Scott A. Mangan Gabriela Nunez-lturri Elsie Rivera-Ocasio Mark Rountree Susanne Vetter Carolina Volkmer de Castllho 《Biotropica》2004,36(3):410-413
29.
Hybrid formation within the genus Leishmania? 总被引:4,自引:0,他引:4
Leishmanial organisms isolated from a desert rodent (Psammomys obesus) and a feral dog (Canis familiaris) in the Eastern Province of Saudi Arabia were isoenzymically distinct from Leishmania major and L. arabica, organisms usually associated with human and wild animal cutaneous leishmaniasis in this area. Further examination of isoenzyme banding patterns of cloned populations of these organisms, together with karyotyping using orthogonal field alternation gel electrophoresis and the use of highly specific kinetoplast DNA probes, has produced evidence suggesting that these organisms isolated from the dog and the rodent are hybrids of L. major and L. arabica. 相似文献
30.
Basic mechanical properties of retina in simple elongation 总被引:4,自引:0,他引:4