全文获取类型
收费全文 | 378065篇 |
免费 | 41325篇 |
国内免费 | 217篇 |
出版年
2018年 | 3461篇 |
2017年 | 3275篇 |
2016年 | 4796篇 |
2015年 | 6888篇 |
2014年 | 7964篇 |
2013年 | 11014篇 |
2012年 | 12816篇 |
2011年 | 12886篇 |
2010年 | 8734篇 |
2009年 | 7847篇 |
2008年 | 11280篇 |
2007年 | 11816篇 |
2006年 | 11069篇 |
2005年 | 10684篇 |
2004年 | 10313篇 |
2003年 | 9956篇 |
2002年 | 9856篇 |
2001年 | 18614篇 |
2000年 | 18759篇 |
1999年 | 14641篇 |
1998年 | 4886篇 |
1997年 | 4999篇 |
1996年 | 4746篇 |
1995年 | 4391篇 |
1994年 | 4325篇 |
1993年 | 4191篇 |
1992年 | 11910篇 |
1991年 | 11498篇 |
1990年 | 11052篇 |
1989年 | 10593篇 |
1988年 | 9819篇 |
1987年 | 9127篇 |
1986年 | 8404篇 |
1985年 | 8313篇 |
1984年 | 6807篇 |
1983年 | 5899篇 |
1982年 | 4545篇 |
1981年 | 4056篇 |
1980年 | 3706篇 |
1979年 | 6407篇 |
1978年 | 4887篇 |
1977年 | 4399篇 |
1976年 | 4069篇 |
1975年 | 4540篇 |
1974年 | 4755篇 |
1973年 | 4648篇 |
1972年 | 4270篇 |
1971年 | 3634篇 |
1970年 | 3298篇 |
1969年 | 3104篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
Vitronectin is a cell-adhesive glycoprotein in serum and plasma, also termed serum spreading factor and complement S-protein. It consists of a mixture of a polypeptide of molecular weight 75 kilodalton (kDa) and its nicked product of 65 kDa plus 10 kDa. By a quantitative immunoblotting assay, human blood samples could be classified into three distinct vitronectin types; type I (58% of the population) was 75 kDa rich and 65 kDa poor, type II (35% of the population) contained approximately equal amounts of 75 kDa and 65 kDa, and type III (5% of the population) was 75 kDa poor and 65 kDa rich. The vitronectin type did not correlate with age, sex, or ABO blood type. 相似文献
992.
993.
994.
A method for the extraction and quantitative determination of both the mass and radioactivity of glycolic acid from -14C-labeled leaf tissue is described. The recoveries of both mass and radioactivity from standard [1-14C]glycolic acid solutions averaged 98 percent, and recovery of radioactivity added to plant samples as [1-14C]glycolic acid was over 90 percent after the complete procedure. The method was reliable with total samples containing as little as 130 nmol of glycolic acid. The mass of glycolic acid recovered from sunflower leaf tissue was proportional to the amount of tissue extracted. In experiments with different plant material, the amount of glycolic acid varied between 530 and 1120 nmol/dm-2 of leaf tissue. The specific radioactivity of the glycolic acid in sunflower leaf tissue during photosynthesis in -14CO(2) was never more than 20 percent of the specific radioactivity of the -14CO(2) supplied. 相似文献
995.
996.
Intermittent illumination increased H2 and C2H4 yields per unit of light from growing cells and from nitrogren-starved cells by 1.7- and 1.35-fold, respectively, as compared with continuous illumination. 相似文献
997.
Z discs were isolated from Lethocerus flight muscle by removing the contractile proteins from myofibrils with a solution of high ionic strength. The protein composition of the Z discs was analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis; the major proteins were alpha-actinin, actin and tropomyosin. Z lines were selectively removed from intact myofibrils by digestion with crude lipase and chymotrypsin, but not by purified lipase. 相似文献
998.
999.
1000.
C. L. Keith R. L. Bridges L. R. Fina K. L. Iverson J. A. Cloran 《Archives of microbiology》1978,118(2):169-172
Anaerobic rupture of the benzoic acid ring was investigated. Carbon 4 was converted primarily to carbon dioxide. Following ring rupture during methane fermentation, propanoic acid is an intermediate, and carbon 4 of benzoate becomes its carboxyl.Contribution No. 1285-j, Division of Biology, Kansas State University, Manhattan, KS 66506. This work was supported in part by funds from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS 66506. Paper II of this series is Fina and Fiskin (1960) 相似文献