全文获取类型
收费全文 | 3525篇 |
免费 | 333篇 |
出版年
2021年 | 50篇 |
2020年 | 14篇 |
2019年 | 35篇 |
2018年 | 41篇 |
2017年 | 34篇 |
2016年 | 64篇 |
2015年 | 109篇 |
2014年 | 161篇 |
2013年 | 189篇 |
2012年 | 225篇 |
2011年 | 216篇 |
2010年 | 140篇 |
2009年 | 150篇 |
2008年 | 177篇 |
2007年 | 190篇 |
2006年 | 197篇 |
2005年 | 197篇 |
2004年 | 191篇 |
2003年 | 164篇 |
2002年 | 183篇 |
2001年 | 39篇 |
2000年 | 45篇 |
1999年 | 65篇 |
1998年 | 68篇 |
1997年 | 52篇 |
1996年 | 50篇 |
1995年 | 42篇 |
1994年 | 39篇 |
1993年 | 39篇 |
1992年 | 57篇 |
1991年 | 53篇 |
1990年 | 44篇 |
1989年 | 39篇 |
1988年 | 46篇 |
1987年 | 21篇 |
1986年 | 29篇 |
1985年 | 36篇 |
1984年 | 36篇 |
1983年 | 26篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1977年 | 19篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1974年 | 19篇 |
1973年 | 16篇 |
1972年 | 10篇 |
排序方式: 共有3858条查询结果,搜索用时 562 毫秒
21.
Sabine Lhernould Yannis Karamanos Sylvain Bourgerie Gerard Strecker Raymond Julien Henri Morvan 《Glycoconjugate journal》1992,9(4):191-197
We have previously isolated mannoside and xylomannoside oligosaccharides with one or two terminal reducingN-acetylglucosamine residues from the extracellular medium of white campion (Silene alba) suspension culture. We have now demonstrated the presence of peptide-N
4-(N-acetylglucosaminyl)asparagine amidase (PNGase) activity in cell extracts as well in the culture medium that could explain the production of those compounds. An additional xylomannoside, (GlcNAc)Man3(Xyl)GlcNAc(Fuc)GlcNAc, was characterized, and1H- and13C-NMR assignments for the oligosaccharide Man3(Xyl)GlcNAc(Fuc)GlcNAc were obtained using homonuclear and heteronuclear spectroscopy (COSY).Abbreviations Endo
endo--N-acetylglucosaminidase
- Fuc
fucose
- GlcNAc
N-acetylglucosamine
- Man
mannose
- NMR
nuclear magnetic resonance
- PNGase
peptide-N
4-(N-acetylglucosaminyl)asparagine amidase
- Xyl
xylose 相似文献
22.
23.
Signal peptidase I overproduction results in increased efficiencies of export and maturation of hybrid secretory proteins in Escherichia coli 总被引:4,自引:0,他引:4
Jan Maarten van Dijl Anne de Jong Hilde Smith Sierd Bron Gerard Venema 《Molecular & general genetics : MGG》1991,227(1):40-48
Summary The effects of 25-fold overproduction ofEscherichia coli signal peptidase I (SPase I) on the processing kinetics of various (hybrid) secretory proteins, comprising fusions between
signal sequence functions selected from theBacillus subtilis chromosome and the mature part of TEM-β-lactamase, were studied inE. coli. One precursor (pre[A2d]-β-lactamase) showed an enhanced processing rate, and consequently, a highly improved release of
the mature enzyme into the periplasm. A minor fraction of a second hybrid precursor (pre[Al3i]-β-lactamase), which was not
processed under standard conditions of SPase I synthesis, was shown to be processed under conditions of SPase I overproduction.
However, this did not result in efficient release of the mature β-lactamase into the periplasm. In contrast, the processing
rates of wild-type pre-β-lactamase and pre(A2)-β-lactamase, already high under standard conditions, were not detectably altered
by SPase I overproduction. These results demonstrate that the availability of SPase I can be a limiting factor in protein
export inE. coli, in particular with respect to (hybrid) precursor proteins showing low (SPase I) processing efficiencies. 相似文献
24.
25.
Gerard H. Markx Christopher L. Davey Douglas B. Kell Phillip Morris 《Journal of biotechnology》1991,20(3):279-290
A novel technique is described for the measurement of the volume fraction of biomass in a suspension by the simultaneous measurement of the conductivity of a suspension containing cells and of the medium in which the cells are suspended. The presence of non-conducting particulate matter in a suspension will cause the conductivity of a suspension to be decreased relative to that of the medium in which the particles are suspended. A simple equation (the Bruggeman equation) describes the relationship between the volume fraction of non-conducting particulate matter and the decrease in conductivity. The accuracy of this method for the determination of the biomass concentration of plant cells (Festuca arundinacea) in culture was shown. The method was successfully applied to the on-line determination of biomass concentrations during the growth of F. arundinacea cultures, and gave good agreement with biomass levels as determined from measurements of the radio-frequency dielectric permittivity of such cultures. 相似文献
26.
Jessica E. Hoogendijk Gerard W. Hensels Ina Zorn Linda Valentijn Emiel A. M. Janssen Marianne de Visser David F. Barker Bram W. Ongerboer de Visser Frank Baas Pieter A. Bolhuis 《Human genetics》1991,88(2):215-218
Summary Recently, it has been shown that Charcot-Marie-Tooth disease type 1a (CMT1a) is linked with a duplication of a DNA segment that is detected by probe VAW409R3, and that is located on chromosome 17p11.2. Here, we show that this duplication also contains VAW412R3a, but not A10-41 and EW503. Accounting for the duplication in recombination analysis, we found recombinants between CMT1a and EW301 and EW502, but not with A10-41, VAW409R3, and VAW412R3. Using pulsed-field gel electrophoresis analysis, we estimated the minimal size of the duplicated region in CMT1a patients to be 1100 kb. 相似文献
27.
The serum unsaturated vitamin B12-binding capacity (UBBC), unsaturated transcobalamin (UTC) I, UTC II, UTC III levels, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase activities and bilirubin concentration were estimated in 61 patients with liver diseases (31 with hepatoma, 30 with viral hepatitis). The levels of serum cobalamin, UTC I, UTC III, UBBC, alanine and aspartate aminotransferases, and bilirubin were raised in both hepatoma and viral hepatitis patients. Serum UTC II was reduced in both conditions. Alkaline phosphatase activity was significantly increased in hepatoma. Four significant correlations were observed among these parameters in the hepatoma patients while only one significant correlation was observed in viral hepatitis. 相似文献
28.
29.
Further evidence for a biological role of anti-estrogen-binding sites in mediating the growth inhibitory action of diphenylmethane derivatives 总被引:1,自引:0,他引:1
A Fargin F Bayard J C Faye M Traore M Poirot A Klaebe J J Perie 《Chemico-biological interactions》1988,66(1-2):101-109
Several diphenylmethane derivatives have been synthesized with variable affinities for Anti-estrogen Binding Sites (ABS) but not for the estrogen receptor. Using these molecules as probes it is shown that their binding affinities for ABS correlate with their abilities to inhibit the growth of MCF-7 human breast cancer cells. In contrast they have no influence on the proliferation of tamoxifen-resistant variant cells (RTx6) in which ABS are undetectable. These data support the conclusion that ABS has a functional role in the anti-proliferative effect of triphenylethylene anti-estrogens and structurally related compounds. 相似文献
30.
CNBr cleavage of unreduced proenzyme Clr yielded fragment CP2b, isolated by gel filtration and highpressure gel permeation chromatography. This fragment (˜ Mτ 55000) comprised at least 4 disulphidelinked peptides, which were separated by gel filtration after reduction and alkylation. Peptide CP2bRA4, overlapping the A- and B-chain regions in proenzyme Clr was digested by V8 staphylococcal protease, and the digest separated by reversed-phase HPLC. N-terminal sequence analysis of peptide CP2bRA4SP9 established that Clr activation involves the cleavage of a single Arg-Ile bond, located in the sequence: Gln-Arg-Gln-Arg-Ile-Ile-Gly-Gly 相似文献