全文获取类型
收费全文 | 8813篇 |
免费 | 1013篇 |
国内免费 | 4篇 |
出版年
2021年 | 90篇 |
2018年 | 80篇 |
2017年 | 67篇 |
2016年 | 138篇 |
2015年 | 233篇 |
2014年 | 248篇 |
2013年 | 342篇 |
2012年 | 413篇 |
2011年 | 451篇 |
2010年 | 290篇 |
2009年 | 257篇 |
2008年 | 417篇 |
2007年 | 388篇 |
2006年 | 394篇 |
2005年 | 393篇 |
2004年 | 439篇 |
2003年 | 376篇 |
2002年 | 355篇 |
2001年 | 137篇 |
2000年 | 159篇 |
1999年 | 197篇 |
1998年 | 152篇 |
1997年 | 95篇 |
1996年 | 84篇 |
1995年 | 98篇 |
1994年 | 96篇 |
1993年 | 86篇 |
1992年 | 155篇 |
1991年 | 134篇 |
1990年 | 140篇 |
1989年 | 134篇 |
1988年 | 108篇 |
1987年 | 116篇 |
1986年 | 104篇 |
1985年 | 119篇 |
1984年 | 97篇 |
1983年 | 92篇 |
1982年 | 106篇 |
1981年 | 86篇 |
1980年 | 108篇 |
1979年 | 108篇 |
1978年 | 91篇 |
1977年 | 108篇 |
1976年 | 82篇 |
1975年 | 80篇 |
1974年 | 113篇 |
1973年 | 93篇 |
1972年 | 61篇 |
1969年 | 66篇 |
1967年 | 60篇 |
排序方式: 共有9830条查询结果,搜索用时 328 毫秒
21.
22.
Acholeplasma laidlawii cells were grown in cholesterol-enriched medium and exposed continuously to either air (control), 4.0 vol.% halothane in air at 1 atm pressure (4% atm halothane), or 80% cyclopropane in oxygen for 24 h at 37°C. Cells grown in the presence of 4% atm halothane or 80% cyclopropane had approximately twice as much membrane cholesterol content/mg protein as the control cells. Cells grown in an anesthetic environment also tended to have a higher membrane cholesterol/phospholipid molar ratio compared to control cells. Membranes isolated from halothane-exposed cells grown in a cholesterol-enriched medium were more ordered at 37°C (measurements were made with no anesthetic present) than membranes from control cells grown in an identically enriched medium. This difference in membrane physical state between control and anesthetic-exposed cells decreased as the temperature decreased, and disappeared at approx. 23°C. Continuous exposure of A. laidlawii to 4% atm halothane or 80% cyclopropane for 24 h did not markedly affect membrane fatty acid composition, either in cells grown on an unsupplemented medium or in cells grown in a medium enriched in myristic, palmitic or stearic acids. These results further support the hypothesis that an increased membrane cholesterol content may play a role in the tolerance or dependence that develops after chronic exposure to anesthetic agents. 相似文献
23.
Band 3, the erythrocyte anion transporter, transfers spontaneously between human red cells and model membranes. During incubation of intact erythrocytes with sonicated dimyristoylphosphatidylcholine vesicles, the transporter inserts in functional form and native orientation into the liposome bilayer, with the cytoplasmic segment of the protein contacting the lumen of the vesicle [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117; Huestis, W. H., & Newton, A. C. (1986) J. Biol. Chem. 261, 16274-16278]. When band 3-vesicle complexes are incubated with erythrocytes whose native band 3 has been inhibited irreversibly, reverse transfer of the protein restores anion transport capacity to the cells [Newton, A. C., Cook, S. L., & Huestis, W. H. (1983) Biochemistry 22, 6110-6117]. Here we report the vesicle-mediated transfer of band 3 to human peripheral blood lymphocytes and to cultured murine lymphoma cells (BL/VL3). Subsequent to incubation with protein-vesicle complexes, both lymphoid cell types exhibit a 2-4-fold increase in the rate of chloride uptake. This enhanced permeability is inhibited greater than or equal to 98% by the exofacial band 3 inhibitor 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid, consistent with right-side-out insertion of functional band 3 into the lymphoid cell membrane. 相似文献
24.
25.
26.
N. Howard Mummery 《BMJ (Clinical research ed.)》1908,2(2496):1408-1409
27.
Leonard F. Liebes Howard Fleit Dorothea Zucker-Franklin Robert Silber 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,633(2):245-257
Tubulin has been purified from human blood and tonsil lymphocytes. Using gel filtration, the molecular weight of human lymphocyte tubulin was estimated to be 119 000. The proteins was shown to consist of two subunits, with molecular weights of 61 000 and 58 000 comparable to the α and β polypeptides of human brain tubulin. A partial identity reaction was observed between lymphocyte tubulin and human tubulin when tested by double immunodiffusion against a rabbit anti-human brain tubulin antibody. In the presence of GTP, the purified protein polymerized to form microtubules. Tubulin was localized to the cell's juxtacentriolar region by immunofluorescence and electron microscopy. When assayed by a colchicine-binding assay corrected for time decay, the binding affinity was 1.50 ± 0.86 · 106M?1 and a level in normal lymphocytes of 1.21 · 10?2 ± 0.79 g/g of soluble protein was determined. Since chronic lymphocytic leukemia lymphocytes have an anomalous capping behavior as well as an unusual susceptibility to colchicine toxicity, the properties and levels of tubulin were determined in these cells. Similar values were obtained for the level, decay rate, molecular weight, and Ka for colchicine as for normal lymphocytes. Chronic lymphocytic leukemia lymphocyte tubulin polymerized in a normal fashion. It thus appears that a decrease in the quantity or function of tubulin does not account for these anomalies in the chronic lymphocytic leukemia lymphocyte. 相似文献
28.
Albert H. Newton 《The Western journal of medicine》1948,68(3):167-169
29.
Three species of tilapia native to Zimbabwe, Oreochromis mossambicus, O. mortimeri and O. macrochir are not naturally sympatric, but because of transplantation they have been brought into sympatry. Allozymes of fish examined from Lakes Kariba, Kyle and Chivero showed evidence of introgressive hybridization. The data showed non-random mating populations in Lakes Kariba and Kyle. All three reservoirs displayed individuals with intermediate principal component scores and hybrid index scores indicating hybridization. 相似文献