全文获取类型
收费全文 | 2263篇 |
免费 | 26篇 |
国内免费 | 16篇 |
出版年
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 75篇 |
2013年 | 75篇 |
2012年 | 67篇 |
2011年 | 69篇 |
2010年 | 52篇 |
2009年 | 38篇 |
2008年 | 47篇 |
2007年 | 76篇 |
2006年 | 47篇 |
2005年 | 47篇 |
2004年 | 20篇 |
2003年 | 23篇 |
2002年 | 4篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1985年 | 88篇 |
1984年 | 194篇 |
1983年 | 161篇 |
1982年 | 205篇 |
1981年 | 222篇 |
1980年 | 146篇 |
1979年 | 137篇 |
1978年 | 113篇 |
1977年 | 98篇 |
1976年 | 56篇 |
1975年 | 28篇 |
1974年 | 29篇 |
1973年 | 22篇 |
1972年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有2305条查询结果,搜索用时 31 毫秒
131.
The origin of replication of the IncW plasmid pSa has been cloned and the function of this origin in Escherichia coli examined. A 1.9-kb region of DNA is required for efficient autonomous replication, and a 0.47-kb fragment within this region can initiate replication only in the presence of an autonomously replicating derivative of pSa. An Mr 35,000 protein (repA) is encoded adjacent to the origin and is required for efficient initiation of replication. The derivatives examined provide information suggesting a direct role of partition factors in plasmid replication and incompatibility. 相似文献
132.
Donald Moir Jen-i Mao James W. Schumm Gerald F. Vovis Bernadette L. Alford Alison Taunton-Rigby 《Gene》1982,19(1):127-138
A full-length cDNA copy of the mRNA encoding calf chymosin (also known as rennin), a proteolytic enzyme with commercial importance in the manufacture of cheese, has been cloned in an f1 bacteriophage vector. The nucleotide sequence of the cDNA was determined, and translation of that sequence into amino acids predicts that the zymogen prochymosin is actually synthesized in vivo as preprochymosin with a 16 amino acid signal peptide. In vitro translation of total poly(A)-enriched RNA from the calf fourth stomach (abomasum) and immunoprecipitation with antichymosin antiserum revealed that a form of chymosin (probably preprochymosin judging from the Mr-value) is the major in vitro translation product of RNA from that tissue. Gel-transfer hybridization of restriction endonuclease-cleaved bovine chromosomal DNA with labeled cDNA probes indicated that the two known forms of chymosin, A and B, must be products of two different alleles of a single chymosin gene. 相似文献
133.
A single mutation in the oli2 region of the mitochondrial DNA causes a charge alteration in a mitochondrially translated subunit of the mitochondrial ATPase (subunit 6; apparent Mr 20 000; apparent pI 6.9 and 7.1). This alteration leads to the defective assembly of the proteolipid subunit into the enzyme complex. The mutant, which is able to grow only very slowly by oxidative metabolism at 28°C offers new possibilities for studying the assembly of the membrane sector (F0) into the mitochondrial ATPase complex and the role of subunit 6 in this process. 相似文献
134.
Robert C. Jennings Flavio M. Garlaschi Paolo D. Gerola Rachel Etzion-Katz Giorgio Forti 《BBA》1981,638(1):100-107
Lowering the pH of the incubation medium to pH 5.4 leads to grana formation morphologically similar to that induced by metal cations. The same phenomenon is observed in EDTA-washed chloroplasts, indicating that it is not due in part to electrostatic ‘masking’ by residual cations associated with the membranes. Digitonin fractionation studies have indicated that the distribution of the major chlorophyll-protein complexes between granal and stromal membrane regions is similar at pH 5.4 in the absence of Mg2+, and at pH 7.4 in the presence of Mg2+. Chlorophyll fluorescence induction studies have indicated that the primary photochemistry of Photosystem II (PS II) is stimulated by lowering the pH to 5.4, just as it is upon metal cation addition at higher pH values. The failure to observe such an increase at pH 5.4 by measuring electron transport to ferricyanide is attributed to a combination of an inhibition by this pH of electron transport at a site after Q reduction and an increase in the number of PS II centres detached from the plastoquinone pool. We conclude that the stacked configuration of chloroplast membranes leads to increased PS II primary photochemistry, which is most simply explained in terms of a redistribution of excitation energy towards PS II. 相似文献
135.
136.
45Ca2+ incorporated in response to glucose was selectively mobilized from the beta-cell-rich pancreatic islets of ob/ob-mice after raising the intracellular Na+ by removal of K+ or addition of ouabain or veratridine. Also studies of insulin release indicated opposite effects of glucose and Na+ on the intracellular sequestration of calcium. The fact that glucose inhibits insulin release induced by raised intracellular Na+ indicates that this sugar can lower the cytoplasmic [Ca2+]. The concept of a dual action of glucose on the cytoplasmic [Ca2+]. The concept of a dual action of glucose on the cytoplasmic [Ca2+] might well explain previous observations of an inhibitory component in the glucose action on the 45Ca2+ efflux. 相似文献
137.
138.
139.
The 125I-labeled Mr 80000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1-39 adrenocorticotropin. The ACTH peptides 22-39 and 1-8, as well as the 1-7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high Mr neurophysin may contain the sequence of ACTH. 相似文献
140.
In brain tissue a spectrin-like calmodulin-binding protein calspectin, or fodrin, is concentrated in a synaptosome fraction, where most of the calspectin is associated with the synaptic membranes. This endogenous calspectin was phosphorylated by protein kinase system(s) associated with the membranes. Here, we report the solubilization and partial purification of the membrane-associated calspectin kinase activity. The activity was resolved on a gel filtration column into two fractions, peaks I and II having estimated Mr of 800 000 and 88 000. The activity of peak I was dependent on the presence of both Ca2+ and calmodulin. Peak II revealed a basal activity in the absence of Ca2+ and calmodulin, which was stimulated 2-fold by addition of Ca2+. Calmodulin had no effect on the peak II activity. 相似文献