全文获取类型
收费全文 | 2875篇 |
免费 | 210篇 |
国内免费 | 215篇 |
专业分类
3300篇 |
出版年
2024年 | 5篇 |
2023年 | 45篇 |
2022年 | 122篇 |
2021年 | 192篇 |
2020年 | 110篇 |
2019年 | 130篇 |
2018年 | 120篇 |
2017年 | 115篇 |
2016年 | 158篇 |
2015年 | 196篇 |
2014年 | 214篇 |
2013年 | 247篇 |
2012年 | 278篇 |
2011年 | 246篇 |
2010年 | 150篇 |
2009年 | 121篇 |
2008年 | 148篇 |
2007年 | 114篇 |
2006年 | 93篇 |
2005年 | 73篇 |
2004年 | 63篇 |
2003年 | 48篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 17篇 |
1997年 | 20篇 |
1996年 | 23篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1968年 | 3篇 |
排序方式: 共有3300条查询结果,搜索用时 0 毫秒
1.
2.
3.
The bioinorganic complexes of europium with N-acetyl-DL-alanine, N-acetyl-DL-valine, and DL-alanyl-DL-alanine have been synthesized and the M?ssbauer spectra at room temperature have been measured for these solid state complexes. The M?ssbauer parameters indicate that the water molecules in these complexes are not directly linked to the central europium ion and are outside the coordination sphere of europium and biological ligands, and that the chemical bond between the europium ion and the ligands may be predominantly ionic in character, with the possibility of partial covalent contribution. 相似文献
4.
Formation of lymphocyte colonies under serum-free culture conditions in normal individuals and patients with chronic lymphocytic leukemia 总被引:1,自引:0,他引:1
Y C Dai G Z Hu H Y Niu Z Wen Z Fang X G Lu J Li Q Wu Y P Huang R Wen 《International journal of cell cloning》1987,5(6):480-491
This paper describes a culture system which supports the formation of B cell and some T cell colonies under serum-free conditions in peripheral blood samples of normal individuals and patients with chronic lymphocytic leukemia (CLL) of B cell type. In this system, serum is replaced by bovine serum albumin, transferrin, cholesterol, insulin and catalase or horseradish peroxidase. In addition, it is necessary to add staphylococcus protein A, mitomycin-treated T cells as feeders and phytohemagglutinin leukocyte-conditioned medium as a source of growth factors. The plating efficiency is greatly enhanced when normal cells are incubated with galactose oxidase prior to plating and when CLL cells are exposed sequentially to neuraminidase and galactose oxidase. 相似文献
5.
Conformation of the second disulfide loop in human transforming growth factor-alpha studied by two-dimensional NMR spectroscopy 总被引:1,自引:0,他引:1
The determination of the conformation of a cyclic heptadecapeptide derived from the second loop of human transforming growth factor-α, [Ala21]-hTGF-α-(16–32), is described. Two-dimensional homonuclear Hartmann–Hahn and rotating-frame cross-relaxation spectroscopy in H2O were used to obtain the complete proton resonance assignments and the necessary distance constraints between nonbonded hydrogen atoms to derive a conformation without involving any energy minimization. The result is an ellipsoidal-shaped structure with a turn at Gly19 and a bend formed by residues 26–29, Gln-Glu-Asp-Lys. Comparison is made with the second loop of human epidermal growth factor and the results are discussed in terms of receptor binding and biological activity. 相似文献
6.
用硫酸铵分段盐析及DEAE-Sephadex A-50、羟磷灰石和CM纤维素等多种柱层析方法,从正常小鼠肝浸液中分离纯化出一种免疫抑制蛋白质(LISP)。在体外用微量该蛋白质就能强烈抑制小鼠T、B淋巴细胞对促有丝分裂原和同种异型抗原的增生反应。纯化的蛋白质在聚丙烯酰胺凝胶电泳(PACE)和等电聚焦(IEF)鉴定时均显示为一条区带,其等电点(pI)值在7.5—7.8范围。沉降系数利S_(20),w为5.39。Sephadex G-100凝胶层析测得LISP的分子量为78,000道尔顿。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)提示LISP是由二个相同的亚基组成,亚基分子量为38,500道尔顿。LISP是一种既非糖蛋白又非脂蛋白的碱性蛋白质,对它的氨基酸组成也作了分析。 相似文献
7.
8.
A wheat cDNA encoding a glycine-rich RNA-binding protein, whGRP-1, was isolated. WhGRP-1 contains two conserved domains, the RNA-binding motif (RNP motif) combined with a series of glycine-rich imperfect repeats, characteristic of a conserved family of plant RNA-binding proteins. Northern analysis revealed that whGRP-1 mRNA accumulates to high levels in roots and to lower levels in leaves of wheat seedlings. whGRP-1 mRNA accumulation is not enhanced by exogenous abscisic acid in seedlings and accumulates to very high levels during wheat embryo development, showing a pattern different from that of the ABA-inducible wheat Em gene. 相似文献
9.
10.