全文获取类型
收费全文 | 3466篇 |
免费 | 298篇 |
国内免费 | 3篇 |
出版年
2021年 | 30篇 |
2020年 | 22篇 |
2019年 | 34篇 |
2018年 | 41篇 |
2017年 | 42篇 |
2016年 | 56篇 |
2015年 | 95篇 |
2014年 | 101篇 |
2013年 | 120篇 |
2012年 | 180篇 |
2011年 | 155篇 |
2010年 | 114篇 |
2009年 | 98篇 |
2008年 | 148篇 |
2007年 | 170篇 |
2006年 | 180篇 |
2005年 | 135篇 |
2004年 | 142篇 |
2003年 | 119篇 |
2002年 | 140篇 |
2001年 | 72篇 |
2000年 | 54篇 |
1999年 | 52篇 |
1998年 | 50篇 |
1997年 | 37篇 |
1996年 | 44篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 37篇 |
1992年 | 45篇 |
1991年 | 54篇 |
1990年 | 37篇 |
1989年 | 43篇 |
1988年 | 35篇 |
1987年 | 42篇 |
1986年 | 33篇 |
1985年 | 22篇 |
1984年 | 33篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1979年 | 29篇 |
1977年 | 23篇 |
1976年 | 28篇 |
1975年 | 27篇 |
1973年 | 21篇 |
1972年 | 22篇 |
1971年 | 21篇 |
1970年 | 21篇 |
1968年 | 23篇 |
排序方式: 共有3767条查询结果,搜索用时 31 毫秒
41.
Dr. Hans-Joachim Gabius Katalin Vehmeyer Reinhild Engelhardt Gerd A. Nagel Friedrich Cramer 《Cell and tissue research》1986,246(3):515-521
Summary A tumor model system of clones of myeloproliferative sarcoma virus (MPV)-transformed rat fibroblasts (NRK) with different growth properties and metastatic potential was studied. The relationship between metastatic behavior and composition of carbohydrate-binding proteins (lectins) was analyzed by affinity chromatography. The metastatic variant differs qualitatively from its parental clone in the presence of galactoside-binding proteins at apparent molecular weights of 80 kDa, 70 kDa, 22 kDa, 18 kDa and 16 kDa and of a fucose-binding protein at apparent molecular weight of 42 kDa. The -glucosyl-binding proteins at apparent molecular weights of 67 kDa and 53 kDa and a galactoside-binding protein of apparent molecular weight of 34 kDa, however, are not detectable in the metastatic variant in comparison to its parental clone. In this respect the parental clone shows closer resemblance to the clone 5–8#1 with different growth properties and low metastatic potential than to its own metastatic variant. Furthermore, only the parental clone has a melibiose- and a mannan-binding protein of an apparent molecular weight of 64 kDa and 14 kDa, respectively. Rosette formation as model system for intercellular interaction reveals differences in the inhibition pattern with sugar between the two clones 5–8#1 and 5–20#20, whereas the metastatic variant 5–20#20 (s) exhibits drastically reduced capability to form rosettes. Initial experiments demonstrate the feasibility of drug targeting to transformed fibroblasts via carbohydrate-binding proteins. 相似文献
42.
M Solti P Dévay I Kiss J Londesborough P Friedrich 《Biochemical and biophysical research communications》1983,111(2):652-658
Like adult heads and whole flies, larval brains of wild type Drosophila melanogaster contain two major soluble cyclic nucleotide phosphodiesterases, forms I and II. Larval brains of the learning-defective mutant strain, dunceM11, contain only the form I enzyme. In both wild type and dunce strains the form I enzyme is activated by Ca2+/calmodulin. A time-dependent loss of this Ca2+ activation was observed. 相似文献
43.
Gliding motility, ultrastructure and nutrition of two newly isolated filamentous sulfate-reducing bacteria, strains 5ac10 and 4be13, were investigated. The filaments were always attached to surfaces. Growth was supported by addition of insoluble aluminium phosphate or agar as substrata for gliding movement. Electron microscopy of ultrathin sections revealed cell walls characteristic of Gramnegative bacteria; the undulated structure of the outer membrane may pertain to the translocation mechanism. Intracytoplasmic membranes were present. Acetate, higher fatty acids, succinate or fumarate served as electron donors and carbon sources. Strain 5ac10 grew also with lactate, but not with benzoate that was used only by strain 4be13. Strain 5ac10 was able to grow slowly on H2 plus CO2 or formate in the presence of sulfate without additional organic carbon source. The capacity of complete oxidation was shown by stoichiometric measurements with acetate plus sulfate. Both strains contained b- and c-type cytochromes. Desulfoviridin was detected only in strain 5ac10. The two filamentous gliding sulfate reducers are described as new species of a new genus, Desulfonema limicola and Desulfonema magnum. 相似文献
44.
45.
46.
Mathias Sprinzl Karl-Heinz Scheit Hans Sternbach Friedrich von der Haar Friedrich Cramer 《Biochemical and biophysical research communications》1973,51(4):881-887
2′-Deoxyadenosine and 3′-deoxyadenosine (cordycepin) can be incorporated into the 3′-terminal position of tRNAPhe by tRNA nucleotidyl transferase. tRNAPhe-C-C-2′dA and tRNAPhe-C-C-3′dA, missing the cis-diol group at the 3′-terminal end are resistant to periodate oxidation and are not able to form borate complexes. In aminoacylation experiments only the tRNAPhe-C-C-3′dA proved to be chargeable. 相似文献
47.
Friedrich Leibenguth 《Biochemical genetics》1973,10(3):231-242
Esterase-2 polymorphism has been investigated quantitatively. Staining intensities of the homodimer bands mm, ff, and ss are not equally expressed but found in relative activities of 1:0.5:0.7 in fat bodies and 1:1:3 in testes and gut walls. Relative intensities of the parental bands are binomially distributed in the three-banded patterns of heterozygotes in an exactly tissue-specific manner. Organ-specific proportions of relative activity remain constant throughout postembryonic development. Among reasons which may influence genesis of allele- and organ-specific activities of homodimer bands in homozygotes and may lead to asymmetrical distribution of intensities in the patterns of heterozygotes, a hypothesis of differential allelic activity is discussed, according to which the structural alleles 2
m
, 2
f
, and 2
s
are closely linked to the alleles RG
a
, RG
b
, and RG
c
of a controlling gene.This work was supported by the Deutsche Forschungsgemeinschaft and submitted with Part I in partial fulfillment of the requirements for the degree of Dr.-habil. at the University of Tübingen. 相似文献
48.
49.
50.
In a chromosome study on leucocyte cultures made in 13 patients treated with chlorpromazine, 15 treated with perphenazine, and nine treated with lysergide, a significantly higher frequency of gaps, breaks, and hypodiploid cells in the patients treated with perphenazine and lysergide occurred compared with the 41 controls studied. It is concluded that if some drugs can induce major chromosome abnormalities, and less toxic alternatives are available, the latter should be used in preference. 相似文献