全文获取类型
收费全文 | 3617篇 |
免费 | 306篇 |
国内免费 | 1篇 |
专业分类
3924篇 |
出版年
2021年 | 27篇 |
2019年 | 23篇 |
2018年 | 30篇 |
2016年 | 55篇 |
2015年 | 78篇 |
2014年 | 87篇 |
2013年 | 151篇 |
2012年 | 174篇 |
2011年 | 167篇 |
2010年 | 105篇 |
2009年 | 94篇 |
2008年 | 181篇 |
2007年 | 159篇 |
2006年 | 160篇 |
2005年 | 136篇 |
2004年 | 137篇 |
2003年 | 147篇 |
2002年 | 138篇 |
2001年 | 48篇 |
2000年 | 38篇 |
1999年 | 49篇 |
1998年 | 45篇 |
1997年 | 40篇 |
1996年 | 36篇 |
1995年 | 59篇 |
1994年 | 36篇 |
1993年 | 49篇 |
1992年 | 35篇 |
1991年 | 33篇 |
1990年 | 32篇 |
1989年 | 28篇 |
1988年 | 35篇 |
1987年 | 31篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 37篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1981年 | 45篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1978年 | 49篇 |
1976年 | 19篇 |
1974年 | 20篇 |
1973年 | 30篇 |
1971年 | 27篇 |
1966年 | 27篇 |
1965年 | 23篇 |
1964年 | 19篇 |
1956年 | 24篇 |
排序方式: 共有3924条查询结果,搜索用时 0 毫秒
1.
The l-thyroxine binding site in human serum thyroxine-binding globulin was investigated by affinity labeling with N-bromoacetyl-l-thyroxine (BrAcT4). Competitive binding studies showed that, in the presence of 100 molar excess of BrAcT4, binding of thyroxine to thyroxine-binding globulin was nearly totally abolished. The reaction of BrAcT4 to form covalent binding was inhibited in the presence of thyroxine and the affinity-labeled thyroxinebinding globulin lost its ability to bind thyroxine. These results indicate BrAcT4 and thyroxine competed for the same binding site. Affinity labeling with 2 mol of BrAcT4/mol of thyroxine-binding globulin resulted in the covalent attachment of 0.7 mol of ligand. By amino acid analysis and high voltage paper electrophoresis, methionine was identified as the major residue labeled (75%). Lysine, tyrosine, and histidine were also found to be labeled to the extent of 8, 8, and 5%, respectively. 相似文献
2.
3.
4.
Regina M. Santella Dezider Grunberger Alfred Nordheim Alexander Rich 《Biochemical and biophysical research communications》1982,106(4):1226-1232
Poly(dG-m5dC)·poly(dG-m5dC) was modified by treatment with N-acetoxy-N-2-acetylaminofluorene (N-Aco-AAF) and its conformation examined by circular dichroism (CD) and susceptibility to S1 nuclease digestion. A sample with a modification level of 10% shows a CD spectrum characteristic of the Z form and is resistant to digestion by S1 nuclease. The relative reactivity of several polymers with N-Aco-AAF was shown to follow the order of ease of formation of Z DNA: poly(dG-m5dC)·poly(dG-m5dC) > poly(dG-dC)·poly(dG-dC) > poly(dG)·poly(dC). This suggests that AAF reacts more readily with Z DNA than B DNA. 相似文献
5.
The kinetics of the electrostatically induced phase transition of dimyristoyl phosphatidic acid bilayers was followed using the stopped-flow technique. The phase transition was triggered by a fast change in the pH or the magnesium ion concentration and followed by recording the time dependence of the absorbance. When the phase transition was induced by a pH jump the time course of the absorbance could be described by two exponentials, their time constants displaying the for cooperative processes characteristic maximum at the transition midpoint. The time constants are in the 10 and 100 ms range for the H+ triggered transition from the fluid to the ordered state. A third slower process shows no appreciable temperature dependence and is probably caused by vesicle aggregation. For the OH--induced transition fron the ordered to the fluid state the time constants are in the 100 and 1000 ms range. The fluid-ordered transition could also be triggered by addition of magnesium ions. Of the several observed processes only the fastest in the 10–100 ms time range could definitely be assigned to the fluid-ordered transition while the others are due to aggregation phenomena. The experimental data were compared with results obtained from pressure jump experiments and could be interpreted on the basis of theories for non-equilibrium relaxation. 相似文献
6.
Ronald J.A. Wanders Carlo Van Roermund Cor Lof Alfred J. Meijer 《Analytical biochemistry》1983,129(1):80-87
A simple fluorimetric assay for the determination of carbamoyl phosphate in tissue extracts is described. In the assay, production of ATP from carbamoyl phosphate and ADP by carbamate kinase is coupled to the formation of NADPH, using glucose, hexokinase, NADP+, and glucose-6-phosphate dehydrogenase. Production of NADPH in this system proved to be equal to the amount of carbamoyl phosphate present. 相似文献
7.
8.
Lower Miocene siliciclastic sediments of the Vöckla Schichten and Atzbacher Sande, Austria, contain a shallow-water trace-fossil assemblage of the Cruziana ichnofacies includingSkolithos isp.,Planolites ? beverleyensis, Ophiomorpha annulata, O.nodosa, Rosselia socialis, Cylindrichnus concentricus, Scolicia isp., andBichordites monastiriensis. The ichnogenusRosselia and the ichnospeciesRosselia socialis are revised. Analysis ofScolicia isp. andB. monastiriensis provides new information about their morphology and ichnotaxonomy. 相似文献
9.
10.
Michael F. Seldin Lawrence A. D'Hoostelaere Alfred D. Steinberg Yumiko Saga Herbert C. Morse III 《Immunogenetics》1987,26(1-2):74-78
Allelic variants of Ly-5 in inbred commensal and other natural populations of mice were analyzed by patterns of restriction fragment length polymorphisms (RFLP) and Southern hybridization using an Ly-5 cDNA probe and by cell-surface staining with a panel of antibodies directed against polymorphic and nonpolymorphic Ly-5 determinants. New Ly-5 alleles were defined by RFLPs generated by both Eco RI and Bam HI restriction enzyme digests. The Mus musculus subspecies and other species within the genus Mus showed a strong correlation between allelic variants defined by restriction enzymes and serologic specificities. The data also suggest the conservation of the Ly-5 gene throughout the genus Mus. 相似文献