全文获取类型
收费全文 | 867篇 |
免费 | 88篇 |
国内免费 | 29篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 25篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 29篇 |
2014年 | 25篇 |
2013年 | 48篇 |
2012年 | 44篇 |
2011年 | 51篇 |
2010年 | 36篇 |
2009年 | 26篇 |
2008年 | 33篇 |
2007年 | 32篇 |
2006年 | 42篇 |
2005年 | 33篇 |
2004年 | 24篇 |
2003年 | 18篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 26篇 |
1999年 | 17篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 21篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1972年 | 6篇 |
1968年 | 10篇 |
1964年 | 6篇 |
排序方式: 共有984条查询结果,搜索用时 31 毫秒
1.
Effects of choline deficiency on rat hepatocytes 总被引:6,自引:0,他引:6
B Lombardi 《Federation proceedings》1971,30(1):139-142
2.
V Lombardi F Capuano A Coci T R Broun R Graham 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1990,(6):51-60
Physiological and biochemical processes which take place in the nervous system at stroke and neurotrauma are reviewed, and the experience of using low doses of steroid derivatives with piridamole in the treatment of central nervous system (CNS) disorders is summarized. ATPases (including Na,K-ATPase) are reported to play an important role in CNS functioning, the correlation between Na,K-ATPase activity and the extent of CNS injury is revealed. The use of NMR-spectroscopy method for investigation of brain and spinal cord condition in vivo is suggested. 相似文献
3.
Payant V; Abukashawa S; Sasseville M; Benkel BF; Hickey DA; David J 《Molecular biology and evolution》1988,5(5):560-567
Nuclear DNA was extracted from each of the eight species comprising the
Drosophila melanogaster species subgroup. Southern hybridization of this
DNA by using a molecular probe specific for the alpha-amylase coding region
showed that the duplicated structure of the amylase locus, first found in
D. melanogaster, is conserved among all species of the melanogaster
subgroup. Evidence is also presented for the concerted evolution of the
duplicated genes within each species. In addition, it is shown that the
glucose repression of amylase gene expression, which has been extensively
studied in D. melanogaster, is not confined to this species but occurs in
all eight members of the species subgroup. Thus, both the duplicated gene
structure and the glucose repression of Drosophila amylase gene activity
are stable over extended periods of evolutionary time.
相似文献
4.
Tyrosine mutations within the alpha platelet-derived growth factor receptor kinase insert domain abrogate receptor-associated phosphatidylinositol-3 kinase activity without affecting mitogenic or chemotactic signal transduction. 总被引:18,自引:10,他引:8 下载免费PDF全文
J C Yu M A Heidaran J H Pierce J S Gutkind D Lombardi M Ruggiero S A Aaronson 《Molecular and cellular biology》1991,11(7):3780-3785
A phosphatidylinositol-3 (PI-3) kinase activity of unknown biological function associates with tyrosine kinase-containing proteins, including a number of growth factor receptors after ligand stimulation. In the beta platelet-derived growth factor (beta PDGF) receptor, phosphorylation of a specific tyrosine residue within the kinase insert domain was required for its interaction with this enzyme. We show that substitutions of phenylalanine for tyrosine residue 731 or 742 within the kinase insert domain of the alpha PDGF receptor do not impair PDGF-induced tyrosine phosphorylation of the receptor or of an in vivo substrate, phospholipase C-gamma. Moreover, phosphatidylinositol turnover in response to ligand stimulation is unaffected. However, both lesions markedly impair receptor association with PI-3 kinase. Antiphosphotyrosine antibody-recoverable PI-3 kinase was also dramatically reduced in PDGF-stimulated cells expressing either mutant receptor. Since neither mutation abolished PDGF-induced mitogenesis or chemotaxis, we conclude that alpha PDGF receptor-associated PI-3 kinase activity is not required for either of these major PDGF signalling functions. 相似文献
5.
Conclusive diagnosis of hepatic and pancreatic malignancies by fine needle aspiration 总被引:1,自引:0,他引:1
A study of the diagnosis of hepatic and pancreatic malignancies by fine needle aspiration (FNA) was made, based on 221 aspirates obtained from 209 patients with histologic or clinical confirmation: 159 with hepatic and 50 with pancreatic lesions. The values of sensitivity, specificity and predictivity for positive FNA results were, respectively, 0.84, 0.96 and 1.0 for the liver and 0.76, 1.0 and 1.0 for the pancreas. The composition of the case material showed an incidence of malignant tumors of the liver and pancreas of 84% and 60%, respectively (among which the primary malignancies were 39% and 48%), while nonneoplastic lesions had incidences of 14% and 40%. However, conclusive FNA diagnoses of the histologic type of the primary and the site of origin of metastatic tumors were made in 60% of the hepatic lesions but in only 9% of the pancreatic lesions. Primary hepatocellular carcinoma was diagnosed by FNA of the liver in 95% of the cases; FNA specifically diagnosed 42% of intrahepatic bile duct carcinomas and 40% of hepatic metastases. These findings correlate with the unique cytologic features of primary hepatocellular carcinoma of intrahepatic rather nonspecific morphology of carcinoma of intrahepatic and extrahepatic origin, as well as of pancreatic ductal origin. 相似文献
6.
7.
An ELISA for the identification of mosquito bloodmeals (MBM) is described. The technique makes use of commercial antisera and allows to investigate at least three different animal sources on the same MBM. The efficiency of identification is 100% for up to 20 hrs-digested MBM. 相似文献
8.
Rifampicin-resistant bacteriophage PBS2 infection and RNA polymerase in Bacillus subtilis 总被引:2,自引:0,他引:2 下载免费PDF全文
Bacteriophage PBS2 replication is unaffected by rifampicin and other rifamycin derivatives, which are potent inhibitors of Bacillus subtilis RNA synthesis. Extracts of gently-lysed infected cells contain a DNA-dependent RNA polymerase activity which is specific for uracil-containing PBS2 DNA. The PBS2-induced RNA polymerase is insensitive to rifamycin derivatives which inhibit the host's RNA polymerase. 相似文献
9.
10.