全文获取类型
收费全文 | 4028篇 |
免费 | 345篇 |
国内免费 | 1篇 |
专业分类
4374篇 |
出版年
2023年 | 20篇 |
2022年 | 43篇 |
2021年 | 83篇 |
2020年 | 45篇 |
2019年 | 91篇 |
2018年 | 83篇 |
2017年 | 81篇 |
2016年 | 152篇 |
2015年 | 182篇 |
2014年 | 212篇 |
2013年 | 262篇 |
2012年 | 264篇 |
2011年 | 229篇 |
2010年 | 155篇 |
2009年 | 176篇 |
2008年 | 172篇 |
2007年 | 175篇 |
2006年 | 184篇 |
2005年 | 187篇 |
2004年 | 161篇 |
2003年 | 148篇 |
2002年 | 135篇 |
2001年 | 111篇 |
2000年 | 120篇 |
1999年 | 81篇 |
1998年 | 61篇 |
1997年 | 58篇 |
1996年 | 41篇 |
1995年 | 36篇 |
1994年 | 30篇 |
1993年 | 35篇 |
1992年 | 63篇 |
1991年 | 47篇 |
1990年 | 53篇 |
1989年 | 47篇 |
1988年 | 44篇 |
1987年 | 43篇 |
1986年 | 26篇 |
1985年 | 33篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1968年 | 6篇 |
排序方式: 共有4374条查询结果,搜索用时 15 毫秒
1.
2.
M del Mar Medina-Puerta A Garrido-Pertierra 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,83(1):215-220
The enzyme 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.44) from bass liver has been purified to over 95% of homogeneity by gel filtration, affinity and ion exchange chromatographies. The apparent molecular weight was estimated by gel filtration chromatography to about 100,000. Analysis of the enzyme on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed to be a dimeric protein. The effect of pH and kinetic properties were studied. 相似文献
3.
A Soler C García del Río L García-Torres F Vargas A Martín-Andrés C Osorio 《Revista Espanola de Fisiología》1985,41(1):107-116
The effects of changes in arterial pressure and in circulating volume on Plasma Renin Activity (PRA) in the intact rat were compared by two experimental procedures. Gradual volume depletion was induced by intraperitoneal injection of a hyperoncotic polyethyleneglycol solution (PEG) in absence of acute changes in Systolic Arterial Pressure (SAP). SAP was measured in the conscious state by the tail cuff technique. Plasma Protein Concentration (PPC) and Hematocrit (Hct) increases after PEG injection were compared as the index for measuring the Plasma Volume Reduction (PVR). PRA showed a significant (p less than 0.001) linear relationship with PPC, suggesting a direct dependence of renin secretion on volume depletion. Acute changes in the circulating volume were induced by controlled hemorrhages of 5.0, 10.0, 15.0 and 20.0 ml of blood/kg body weight. The increase in PRA showed a significant relationship with the changes in circulating volume, but it did not show any dependence on the changes in Mean Arterial Pressure (MAP). Our results suggest that, in the intact and conscious rat, renin secretion responds to the information from the cardiopulmonary volume receptors rather than to that from the high pressure receptors. 相似文献
4.
Andrea Schrödel 《当今生物学》2007,37(5):289-289
5.
6.
The method of tissue embedding in melamine resin was applied to rat skeletal muscle. This method does not require tissue dehydration with organic solvents; only aqueous solutions are used. Electron micrographs of muscles embedded in melamine differ from those embedded in the conventional epoxy resin. In melamine-embedded muscles the actin and myosin filaments appear larger in diameter and subunits can be recognized in cross-sectioned myosin filaments. Within the Z-line, the characteristic patterns described for muscles embedded in epoxy resin are not visible; the spaces between the actin filaments are filled with electron-dense material. This suggests that the Z-line is more compact than could be concluded from epoxy resin-embedded muscle specimens. The M-line appears to be different from what is observed in epoxy-embedded muscle. The membranes appear as several clearly delineated layers. Dehydration rather than the action of the organic solvents per se is the main reason for the differences in the structure of the contractile apparatus between melamine- and epoxy-embedded muscles. 相似文献
7.
Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane 总被引:4,自引:0,他引:4
Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho
0 strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion. 相似文献
8.
W Bandlow U Schwarz G R?del G Strobel C Wachter 《Biological chemistry Hoppe-Seyler》1985,366(6):545-553
We have isolated a cAMP-binding protein from highly purified yeast mitochondria by affinity chromatography. It is a lipophilic protein of molecular mass 45 000 Da, which is tightly membrane-bound and localized on the outer surface of the inner membrane. It can be solubilized in active form under mild conditions. The cAMP receptor resembles mitochondrial RNA polymerase prepared as described by Levens et al. [(1981) J. Biol. Chem. 256, 1474] in a surprisingly large number of properties including molecular mass. Comparison of the two proteins revealed that the polypeptide previously considered as RNA polymerase is, in fact, a mitochondrial cAMP receptor protein. 相似文献
9.
Screening of plasmids in non-pathogenic corynebacteria 总被引:1,自引:0,他引:1
H. Sandoval G. del Real L.M. Mateos A. Aguilar J.F. Martín 《FEMS microbiology letters》1985,27(1):93-98
Abstract A screening of plasmids in 25 nonpathogenic coryneform bacteria was carried out. 11 Strains showed at least one plasmid, ranging in size from 4.2 to 55 kb. These plasmids did not encode bacteriocin production or resistance to a number of antibiotics or to ions such as arsenite, mercury(II) and cobalt(II). A detailed study of plasmid pBL100 from Brevibacterium linens is presented. pBL100 has a size of 7.75 kb, and contains single sites for the endonucleases: Hin dIII; Pst I, Bgl II, Eco RI and Bam HI. B. linens is easily and efficiently transformed with vectors derived from pBL1 isolated from Brevibacterium lactofermentum . 相似文献
10.
Freeze etching studies in a symbiotic and a freeliving strain of Chroococcidiopsis revealed a specific layer in the outer cell wall not described so far from Cyanophyta. The layer showed a complex organisation: The main unit are ribbons, 2–3 nm thick, striated at right angle to the longitudinal axis. They are interwoven to a patchwork-like leaflet. The ribbons are virtually composed of globular particles associated in parallel rows. The cytoplasmic membrane and the cell walls of the symbiotic and the free-living strain were compared.Abbreviations cm
cytoplasmic membrane
- CW 1,2,3
cell wall layer 1,2,3
- EF
exoplasmic fracture face
- PF
protoplasmic fracture face 相似文献