全文获取类型
收费全文 | 120203篇 |
免费 | 2720篇 |
国内免费 | 834篇 |
出版年
2022年 | 202篇 |
2021年 | 436篇 |
2020年 | 254篇 |
2019年 | 333篇 |
2018年 | 12191篇 |
2017年 | 10956篇 |
2016年 | 8025篇 |
2015年 | 1684篇 |
2014年 | 1430篇 |
2013年 | 1750篇 |
2012年 | 6074篇 |
2011年 | 14571篇 |
2010年 | 13041篇 |
2009年 | 9126篇 |
2008年 | 11100篇 |
2007年 | 12744篇 |
2006年 | 1661篇 |
2005年 | 1875篇 |
2004年 | 2326篇 |
2003年 | 2329篇 |
2002年 | 1995篇 |
2001年 | 558篇 |
2000年 | 375篇 |
1999年 | 308篇 |
1998年 | 353篇 |
1997年 | 257篇 |
1996年 | 234篇 |
1995年 | 257篇 |
1994年 | 240篇 |
1993年 | 232篇 |
1992年 | 240篇 |
1991年 | 236篇 |
1990年 | 176篇 |
1989年 | 172篇 |
1988年 | 186篇 |
1987年 | 179篇 |
1986年 | 167篇 |
1985年 | 203篇 |
1984年 | 222篇 |
1983年 | 197篇 |
1982年 | 244篇 |
1981年 | 249篇 |
1980年 | 255篇 |
1979年 | 172篇 |
1978年 | 178篇 |
1977年 | 159篇 |
1976年 | 195篇 |
1973年 | 169篇 |
1972年 | 336篇 |
1971年 | 357篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Protein phosphorylation in human peripheral blood lymphocytes. Phosphorylation of endogenous plasma membrane and cytoplasmic proteins 下载免费PDF全文
Phosphorylation of endogenous proteins in subcellular fractions of human peripheral-blood lymphocytes was studied by one- and two-dimensional polyacrylamide-gel electrophoresis. Studies using extensively purified subcellular fractions indicated that the endogenous phosphorylating activity in the particulate fractions was derived primarily from the plasma membrane. Electrophoresis of (32)P-labelled subcellular fractions in two dimensions [O'Farrell (1975) J. Biol. Chem.250, 4007-4021] provided much greater resolution of the endogenous phosphoproteins than electrophoresis in one dimension, facilitating their excision from gels for quantification of (32)P content. More than 100 cytoplasmic and 20 plasma-membrane phosphorylated species were observed. Phosphorylation of more than 10 cytoplasmic proteins was absolutely dependent on cyclic AMP. In the plasma membrane, cyclic AMP-dependent phosphoproteins were observed with mol.wts. of 42000, 42000, 80000 and 90000 and pI values of 6.1, 6.3, 6.25 and 6.5 respectively. Phosphorylation of endogenous cytoplasmic and plasma-membrane proteins was rapid with t((1/2))=5-12s at 25 degrees C. Between 40 and 70% of the (32)P was recovered as phosphoserine and phosphothreonine when acid hydrolysates of isolated plasma-membrane phosphoproteins were analysed by high-voltage paper electrophoresis. The presence of cyclic AMP-dependent protein kinase and endogenous phosphate-acceptor proteins in the plasma membranes of lymphocytes provides a mechanism by which these cells might respond to plasma-membrane pools of cyclic AMP generated in response to stimulation by mitogens or physiological modulators of lymphocyte function. 相似文献
992.
Shyi Yi Huang Charles W. Berry Joseph T. Newman William H. Cooper Nannepaga Y. Zachariah 《Mycopathologia》1979,67(1):55-58
Rabbits were employed as experimental models to evaluate a solid-phase radioimmunoassay (RIA) method for the diagnosis of systemic candidiasis. Ten rabbits were inoculated subcutaneously to mimic superficial candidiasis and were found to produce no antibodies to Candida as determined by both immunodiffusion and RIA procedures. However, 94 per cent of 18 rabbits systemically infected by intravenous injection of Candida cells were observed to produce antibody as assessed by the RIA technique. These data encourage further tests with human sera and the continued development of this RIA procedure as a useful tool in the early serodiagnosis of systemic candidiasis. 相似文献
993.
Dr. Darrell R. Stokes Anthony J. Vitale Charles R. Morgan 《Cell and tissue research》1979,198(1):175-189
Histochemical techniques have been employed to characterize enzymatic activity in the mesocoxal muscles of the cockroach, Periplaneta americana. Through our studies of the enzymes myosin-ATPase, NADH reductase, succinic dehydrogenase (SDH), and lactic dehydrogenase (LDH), we were able to classify fibers within these muscles according to criteria established for muscle fibers of vertebrates. Many of the mesocoxal muscles possess two different and distinct populations of fibers, whereas the remaining muscles are homogeneous with respect to their constituent fibers. The data presented here indicate biochemical heterogeneity for muscles of differing structural and functional features and possible neurotrophic influences upon oxidative enzymes and myosin-ATPase isozymes. 相似文献
994.
Jaap H. Waterborg Hermanus F. W. van Brakel Charles M. A. Kuyper 《Archives of microbiology》1979,122(2):195-200
During the sclerotization of microplasmodia of Physarum polycephalum in non-nutrient salt medium or in salt medium supplemented by glucose, RNA or nucleotides a 6-fold increase in the specific activity of an alkaline endonuclease was found within 6 h after the induction. The increase was based on de novo synthesis of the enzyme and it was strongly correlated to the sharp drop in the level of cellular RNA in the first hours of the process of scerotization. The induction in exhausted growth medium or in salt medium supplemented by protein or mannitol showed a gradual 2-3-fold increase of the endonuclease in 30 h, parallel to the gradual decrease of the RNA. No changes in the specific activity of the endonuclease were found during logarithmic growth or under conditions of starvation without the induction to sclerotization.The alkaline, polyA-specific endonuclease could possibly regulate the turnover of RNA. 相似文献
995.
996.
Carlos E. Nasjleti Charles J. Kowalski James E. Harris Nadia A. Abu Elsoued Mohamed M. Nofal 《Human genetics》1979,47(2):203-205
Summary A total of 242 metaphase plates from the peripheral blood of Nubian males living near Aswan, Egypt were studied with respect to the length of the Y chromosome and its location in metaphase spreads. The length of the Y was similar to that found in American Negroes, and the Y chromosome was peripherally located in 79 of the 242 cells. 相似文献
997.
998.
999.
John H. Pazur Yoshio Tominaga Charles W. DeBrosse Lloyd M. Jackman 《Carbohydrate research》1978,61(1):279-290
The formation of 1,6-anhydro-β-d-glucopyranose and several d-glucosyl oligosaccharides has been observed during the action of a purified, fungal glucosyltransferase (EC 2.4.1.24) on maltose. Such products are synthesized by a transglucosylation mechanism involving the formation of a d-glucosyl-enzyme complex and the displacement of the d-glucosyl group by appropriate acceptor-substrates. The formation of the 1,6-anhydro bond is a novel type of transfer reaction and occurs by displacement of the enzyme from the d-glucosyl-enzyme complex by the proton of the primary hydroxyl group of the same glucosyl group. This reaction is characterized by inversion of configuration at the position of glucosidic bond-cleavage of the substrate. Synthesis of the d-glucosyl oligosaccharides occurs by displacement of the d-glucosyl groups from the enzyme by suitable acceptor-substrates. In these cases, the reactions are characterized by retention of configuration of the d-glucosidic bonds of the substrate. The list of oligosaccharides produced from maltose includes nigerose, kojibiose, isomaltose, maltotriose, panose, isomaltotriose, and 6-O-d-glucosyl-panose. The identity of these compounds has been established by methylation analysis and enzymic hydrolysis. d-Glucose is also a product of the reaction and arises from both the reducing and the non-reducing groups of maltose. 相似文献
1000.
Treatment of d-glucono-1,5-lactone (3) with excess of acetic anhydride in anhydrous pyridine at room temperature afforded the tetra-acetate and 2,4,6-tri-O-acetyl-3-deoxy-d-erythro-hex-2-enono-1,5-lactone (1). On prolonged reaction or at 80°, 3-acetoxy-6-acetoxymethylpyran-2-one (5) was the unexpected main product. The mechanistic implications of the conversion of 1 → 5 are discussed. 相似文献