全文获取类型
收费全文 | 10121篇 |
免费 | 1080篇 |
国内免费 | 252篇 |
专业分类
11453篇 |
出版年
2024年 | 80篇 |
2023年 | 100篇 |
2022年 | 139篇 |
2021年 | 154篇 |
2020年 | 393篇 |
2019年 | 470篇 |
2018年 | 448篇 |
2017年 | 336篇 |
2016年 | 287篇 |
2015年 | 305篇 |
2014年 | 464篇 |
2013年 | 644篇 |
2012年 | 337篇 |
2011年 | 341篇 |
2010年 | 232篇 |
2009年 | 312篇 |
2008年 | 343篇 |
2007年 | 402篇 |
2006年 | 371篇 |
2005年 | 365篇 |
2004年 | 277篇 |
2003年 | 268篇 |
2002年 | 258篇 |
2001年 | 176篇 |
2000年 | 148篇 |
1999年 | 152篇 |
1998年 | 167篇 |
1997年 | 132篇 |
1996年 | 136篇 |
1995年 | 118篇 |
1994年 | 139篇 |
1993年 | 151篇 |
1992年 | 119篇 |
1991年 | 129篇 |
1990年 | 99篇 |
1989年 | 105篇 |
1988年 | 75篇 |
1987年 | 90篇 |
1986年 | 63篇 |
1985年 | 169篇 |
1984年 | 313篇 |
1983年 | 235篇 |
1982年 | 291篇 |
1981年 | 274篇 |
1980年 | 183篇 |
1979年 | 182篇 |
1978年 | 144篇 |
1977年 | 120篇 |
1976年 | 73篇 |
1975年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Human erythrocytes were incubated in isotonic solutions of different monovalent cations. The apparent size of the red cells
measured on scanning electron microscopic pictures decreases in the order Li+>Na+=K+>Rb+. These differences in size are abolished after pretreatment with trypsin, which removes a large part of the charges associated
with membrane glycoproteins. Shape alterations are also observed. Normal biconcave shapes are visible after Na+ or K+ incubation, whereas Li+ leads to flabby, flattened cells with a certain tendency to crenation, and Rb+ causes more pronounced biconcavity with a certain tendency to cupping. The overall effects of pretreatment with trypsin are
similar to those of Li+. Our results provide evidence that the electrostatic repulsion of glycoproteins and other charged membrane components may
play an essential role in maintaining red cell shape. 相似文献
95.
C. Lal Kapoor Gerald J. Chader 《Biochemical and biophysical research communications》1984,122(3):1397-1403
A calcium phospholipid-dependent protein kinase (C-kinase) activity was detected in the soluble fraction of rod outer segments (ROS) of the bovine retina. The enzyme required calcium, phosphatidylserine (PS) and diacylglycerol for maximal activity. In the presence of calcium and PS, C-kinase endogenously phosphorylated proteins with molecular weights of 95,000, 91,000, 31,000, 21,000, 19,000, 18,000, 16,000, 14,000 and 11,000. Addition of diolein in the reaction mixture further enhanced the endogenous phosphorylation of these proteins. Retinal was found to inhibit the phosphorylation of endogenous proteins by C-kinase in a concentration dependent manner. Half-maximal inhibition of enzyme activity was obtained at a retinal concentration of about 12μM. These results suggest that calcium, phospholipids and the C-kinase enzyme may play an important role in the functional regulation of rod photoreceptors and, with retinal, perhaps in the visual process as well. 相似文献
96.
P Midoux J P Grivet F Delmotte M Monsigny 《Biochemical and biophysical research communications》1984,119(2):603-611
The synthesis of N-acetyl- and N-trifluoroacetyl-glucosaminides was reported. The interaction of these compounds with wheat germ agglutinin, a plant lectin specific for N-acetyl-glucosamine and sialic acid, was investigated by two complementary approaches: 1H and 19F NMR, and fluorescence spectroscopy. This last technique relies on the existence of a competitive equilibrium involving the protein, the ligand and O-(methylumbelliferyl)-N-acetyl-glucosaminide, a fluorescent saccharide. The binding constants and the chemical shifts in the complex were determined and were related to the protein structure. 相似文献
97.
Cytochrome c oxidase preparations from bovine heart muscle contain 1 zinc per 2 irons. Metal contents of nine preparations determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) show that Cu, Fe and Zn are the only metals present in significant amounts with average Cu/Fe, Fe/Zn, and Cu/Zn atom ratios of 1.3, 2.1 and 2.8, respectively. Removal of adventitious copper results in a Cu:Fe:Zn stoichiometry of 2:2:1. The zinc is tightly bound. Dialysis against a solution of 1,10-phenanthroline at pH 7.4 or an acidic buffer (pH 4.4) does not remove Zn. Dialysis against 0.8 M KCN at pH 10 causes partial loss of both Cu and Zn. This is the first evidence for the presence of Zn in a cytochrome c oxidase. 相似文献
98.
Y Gache F Landon H Touitou A Olomucki 《Biochemical and biophysical research communications》1984,124(3):877-881
Purified alpha-actinin from human platelets was digested with Ca2+-activated protease from muscle. The alpha subunit (Mr = 100 kDa) was degraded into a unique polypeptide b of slightly lower molecular mass. In fresh platelets, only the a subunit was detected by immunoblotting techniques, while in out-dated platelets, both a and b polypeptides were present. Since a similar conversion of a to b occurs in vitro as in whole platelets, it can be assumed that, in platelets, alpha-actinin is cleaved by the endogenous Ca2+-activated protease. 相似文献
99.
SODIUM TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK 总被引:1,自引:1,他引:0
100.
Electrophoretic analysis of polyphenoloxidase isoenzymes from a variety of angiosperms and from mushroom revealed that the enzymes remain active in the presence of 0.1 % sodium dodecylsulfate. Electrophoresis in the presence of sodium dodecylsulfate allows the detection of latent enzyme forms of polyphenoloxidase, and can also convert slower migrating enzyme forms to faster migrating forms. Electrophoresis in the absence of sodium dodecylsulfate followed by incubation in the presence of sodium dodecylsulfate can also be used to detect latent forms of polyphenoloxidase. Together, these approaches provide a method for screening latent enzymes and give some insight into the mechanism of activation by sodium dodecylsulfate. 相似文献