全文获取类型
收费全文 | 95336篇 |
免费 | 8586篇 |
国内免费 | 45篇 |
专业分类
103967篇 |
出版年
2023年 | 357篇 |
2022年 | 804篇 |
2021年 | 1660篇 |
2020年 | 940篇 |
2019年 | 1241篇 |
2018年 | 1527篇 |
2017年 | 1398篇 |
2016年 | 2259篇 |
2015年 | 3883篇 |
2014年 | 4402篇 |
2013年 | 5259篇 |
2012年 | 7070篇 |
2011年 | 6862篇 |
2010年 | 4378篇 |
2009年 | 4135篇 |
2008年 | 5856篇 |
2007年 | 5893篇 |
2006年 | 5498篇 |
2005年 | 5330篇 |
2004年 | 5132篇 |
2003年 | 4932篇 |
2002年 | 4639篇 |
2001年 | 958篇 |
2000年 | 719篇 |
1999年 | 1000篇 |
1998年 | 1303篇 |
1997年 | 886篇 |
1996年 | 814篇 |
1995年 | 768篇 |
1994年 | 655篇 |
1993年 | 736篇 |
1992年 | 660篇 |
1991年 | 559篇 |
1990年 | 563篇 |
1989年 | 543篇 |
1988年 | 506篇 |
1987年 | 468篇 |
1986年 | 435篇 |
1985年 | 609篇 |
1984年 | 680篇 |
1983年 | 617篇 |
1982年 | 719篇 |
1981年 | 658篇 |
1980年 | 659篇 |
1979年 | 387篇 |
1978年 | 465篇 |
1977年 | 396篇 |
1976年 | 398篇 |
1974年 | 351篇 |
1973年 | 346篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
Expression of the Opc protein correlates with invasion of epithelial and endothelial cells by Neisseria meningitidis 总被引:11,自引:0,他引:11
Mumtaz Virji Katherine Makepeace David J. P. Ferguson Mark Achtman Jasmine Sarkari E. Richard Moxon 《Molecular microbiology》1992,6(19):2785-2795
Whereas capsulate strains of Neisseria meningitidis are dependent on pili for adhesion to human endothelial and epithelial cells, strains which lacked assembled pili and were partially capsule-deficient adhered to and invaded human endothelial and epithelial cells if they expressed the Opc protein. Bacteria expressing low or undetectable levels of Opc protein failed to adhere to or invade eukaryotic cells. In addition, the presence of OpaAC751 protein on the surface of bacteria did not increase bacterial interactions with host cells. Association of Opc-expressing bacteria was inhibited by antibodies against Opc. Invasion was dependent on the host-cell cytoskeletal activity and was inhibited by cytochalasin D. In some cells, infected at the apical surface, bacteria emerging from basal surface were detected by electron microscopy. Opc is found in diverse meningococci and may represent a common virulence factor which facilitates adherence and invasion by these bacteria. 相似文献
192.
Summary Membrane inlet mass spectrometry (MIMS) is introduced as a method for measuring water activity in nonpolar solvents, aqueous
solutions and gas phase. The determination of the rate of hydrolysis of diphenyl carbonate by porcine liver esterase as a
function of water activity in diisopropyl ether is presented as an example. A linear relationship is found between the enzyme
activity and the water activity. 相似文献
193.
Michele Solem Angela Helmrich Paul Collodi David Barnes 《Molecular and cellular biochemistry》1991,100(2):141-149
Summary Human S-protein is a serum glycoprotein that binds and inhibits the activated complement complex, mediates coagulation through interaction with antithrombin III and plasminogen activator inhibitor I, and also functions as a cell adhesion protein through interactions with extracellular matrix and cell plasma membranes. A full length cDNA clone for human S-protein was isolated from a lambda gt11 cDNA library of mRNA from the HepG2 hepatocellular carcinoma cell line using mixed oligonucleotide sequences predicted from the amino-terminal amino acid sequence of human S-protein. The cDNA clone in lambda was subcloned into pUC18 for Southern and Northern blot experiments. Hybridization with radiolabeled human S-protein cDNA revealed a single copy gene encoding S-protein in human and mouse genomic DNA. In addition, the S-protein gene was detected in monkey, rat, dog, cow and rabbit genomic DNA. A 1.7 Kb mRNA for S-protein was detected in RNA from human liver and from the PLC/PRF5 human hepatoma cell line. No S-protein mRNA was detected in mRNA from human lung, placenta, or leukocytes or in total RNA from cultured human embryonal rhabdomyosarcoma (RD cell line) or cultured human fibroblasts from embryonic lung (IMR90 cell line) and neonatal foreskin. A 1.6 Kb mRNA for S-protein was detected in mRNA from mouse liver and brain. No S-protein mRNA was detected in mRNA from mouse skeletal muscle, kidney, heart or testis. 相似文献
194.
195.
David Hyndman 《Dialectical Anthropology》1991,16(2):169-184
David Hyndman is Professor in the Department of Anthropology and Sociology, University of Queensland, Australia 相似文献
196.
197.
David B. Herbst 《Hydrobiologia》1988,158(1):145-166
The population dynamics of Ephydra hians Say final instar larvae and pupae were compared over a two year period in rocky littoral habitats of two alkaline saline lakes in the western Great Basin. Relative abundance increased from 1983 to 1984 at Mono Lake (California), during dilution from ca. 90 to 80 g 1-1 TDS (total dissolved solids). In contrast, relative abundance decreased over the same period at Abert Lake (Oregon), accompanied by a dilution of salinity from ca. 30 to 20 g l-1 and a marked increase in the number and abundance of other benthic macroinvertebrate species. These observations are consistent with a hypothesis that proposes biotic interactions limit E. hians abundance at low salinity, and physiological stress limits abundance at high salinity.Oviposition extends from early spring to early fall. Mixed instars present throughout this period indicates multivoltine population dynamics with overlapping generations. The standing stock biomass of final instars increases exponentially in late spring and peaks in late summer or early fall. Pupae increase in proportional representation and abundance from a spring minimum to a fall maximum. The body size of adults and pupae cycle seasonally from a spring maximum to a fall minimum, and may be related to either or both food limitation, or water temperature. 相似文献
198.
199.
David Díaz-Miranda 《Brittonia》1988,40(2):235-238
A report on the family Scrophulariaceae in the páramos of the Venezuelan Andes is made, which includes 13 genera. A key to
the genera is provided. 相似文献