全文获取类型
收费全文 | 4929篇 |
免费 | 393篇 |
国内免费 | 1篇 |
出版年
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 101篇 |
2020年 | 79篇 |
2019年 | 93篇 |
2018年 | 127篇 |
2017年 | 114篇 |
2016年 | 178篇 |
2015年 | 236篇 |
2014年 | 271篇 |
2013年 | 311篇 |
2012年 | 388篇 |
2011年 | 371篇 |
2010年 | 254篇 |
2009年 | 234篇 |
2008年 | 309篇 |
2007年 | 257篇 |
2006年 | 239篇 |
2005年 | 206篇 |
2004年 | 212篇 |
2003年 | 202篇 |
2002年 | 208篇 |
2001年 | 81篇 |
2000年 | 56篇 |
1999年 | 62篇 |
1998年 | 54篇 |
1997年 | 47篇 |
1996年 | 37篇 |
1995年 | 53篇 |
1994年 | 38篇 |
1993年 | 46篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1972年 | 7篇 |
1970年 | 7篇 |
排序方式: 共有5323条查询结果,搜索用时 31 毫秒
71.
Christiane Chine Michael Fountoulakis Heinz Dbeli Brigitte D'Arcy Fritz Winkler Allan D'Arcy 《Proteins》1995,23(4):591-594
A complex of human interferon-γ (IFN- γ) with the soluble extracellular domain of the IFN- γ receptor α-chain (IFN-γ-R) has been crystallised. Crystals of the complex were grown using PEG 4000 as the precipitating agent in the presence of β-octyl glucoside. The receptor-ligand complex crystallizes in a monoclinic space group and diffracts to about 3.0 Å resolution. Isomorphous crystals have been obtained with complex containing selenomethionine and cysteine mutants of IFN-γ, which may facilitate the ongoing X-ray structure determination. © 1995 Wiley-Liss, Inc. 相似文献
72.
Marcela F. Lopes Vânia Lúcia C. Merquior JoséMauro Peralta Lúcia M. Teixeira 《FEMS immunology and medical microbiology》1995,12(3-4):205-211
Abstract Exosubstances (cohemolysins) produced by Streptococcus agalactiae (CAMP-factor) and Streptococcus uberis (Uberis-factor) showing hemolytic synergism with β-lysin produced by Staphylococcus aureus were compared. Cohemolytic activity was evaluated in the supernatants of bacterial cultures, before and after ammonium sulfate precipitation. Sheep erythrocytes sensitized with β-lysin were used as substrate. The assays were performed in microtiter plates and results were expressed as cohemolytic units/ml. Maximum cohemolytic activity was detected, respectively, after 8 h and 14 h of growth in Columbia broth in S. uberis and S. agalactiae cultures. Cohemolytic activities of both microorganisms showed similarities when submitted to various physical and chemical treatments. They were significantly decreased by heating at 60°C and 100°C, or in presence of trypsin, and were abolished in the presence of Tween 20. Activities were found to be stable in crude supernatants and concentrated preparations maintained at −20°C for 3 months. Differences were related to levels of activity and kinetics of detection during the growth cycle. The results indicate the proteic nature, at least in part, of the Uberis factor. Analysis by PAGE in the presence or absence of SDS allowed us to correlate Uberis activity with a protein band with apparent molecular mass of 42 kDa, while CAMP activity was associated with a protein band of 27 kDa. 相似文献
73.
A greenhouse experiment was carried out to investigate the influence of the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on metabolic changes in tropical maize (Zea mays L.) under drought. Two cultivars, Tuxpeno sequia CO (drought sensitive) and C8 (drought resistant), were subjected for 3 weeks to water stress following tasselling (75–95 days after sowing). Fully expanded 7th or 8th leaves were sampled and assessed for levels of chlorophyll, sugars, proteins, and amino acids. Chlorophyll content was not altered either by water stress or the presence of mycorrhizae. Mycorrhizal plants (M+) had higher total and reducing sugars than nonmycorrhizal plants (M-) at the end of 3 weeks of the drought cycle. An increase in protein content was observed with drought stress in M + plants of the cultivar C0. Most of the amino acids showed a linear increase during the period of water stress in M+ and M- plants for both cultivars. Total amino acids increased by 40.6% and 43.7% in M- plants of C0 and C8, respectively. With the presence of AM fungus, amino acid levels increased by only 10.7% and 19.2% of leaf dry mass in C0 and C8, respectively. Alanine, asparagine, glutamine, and glycine accounted for 70% of the amino acid pool. Under drought, AM inoculation enabled the plants to retain considerable amounts of sugars and proteins, especially in the drought-sensitive cultivar C0. This may be of physiological importance in helping the plant to withstand moderate drought. 相似文献
74.
Polysomes from dark-grown and illuminated barley seedlings were translated in cell-free systems. The translation products reacting with the antibody against the light-harvesting chlorophyll a/b protein (LHCP) were analyzed by polyacrylamide gel electrophoresis. It was found that, in addition to the precursor protein of LHCP, a product was obtained that co-migrated with the mature protein. Furthermore, the results show that the light-induced proly(A)RNA for LHCP is integrated into the polysomal complex without delay, indicating that the integration of LHCP into the membrane is controlled at a higher level of gene expression. 相似文献
75.
Christiane Lichtlé 《Protoplasma》1980,102(1-2):11-19
Summary C.rufescens excystment, experimentally induced, corresponds to a general metabolism recovery of the cell, previously in a resting phase. The cytoplasm changes without any polarity, and organelles like gullet and flagella redifferentiate. The thylakoids develop mainly from the stored lipidic compounds which then disappear. Phycoerythrin immediately fills the intrathylakoidal lumen. Pigment synthesis seems closely associated with the development of membranes. The activated cell divides and the cyst wall breaks down. The destruction of the wall begins in the median layer and is followed by a mechanical rupture of the external and internal layers. Each germinative cyst releases two or four fully differentiated cells. There is an exact symmetry between excystment and encystment, all the transformations of theC. rufescens cell being reversible. 相似文献
76.
Christiane Guguen-Guillouzo Marie-France Szanjnert Denise Glaiser Claudine Gregori Fanny Schapira 《In vitro cellular & developmental biology. Plant》1981,17(5):369-377
Summary Aldolase and pyruvate kinase isozymes were investigated in cultured hepatocytes from fetal, regenerating, and 2-acetyl-aminofluorene-fed
rat liver as well as in some epithelial liver cell lines. Our results show that: (a) cell proliferation and prolonged expression
of specific isozymes were found only in cultured hepatocytes from 17-day old fetuses; (b) the fetal type of pyruvate kinase
expressed in regenerating and carcinogen-treated liver was temporarily lost only in cultured hepatocytes from regenerating
liver; (c) the adult type of aldolase and pyruvate kinase was absent in one epithelial cell line derived from a carcinogen-treated
liver and in the hepatoma tissue cell (HTC) line but was found in the Faza clone of the Reuber H35 cell line during the 50 first passages in vitro; and (d) the isozyme pattern of pyruvate kinase was always more strongly
shifted than that of aldolase.
The observations suggest that: (a) hepatocytes from carcinogen-treated liver exhibit the same lack of ability to proliferate
in primary culture as normal adult hepatocytes; (b) adult hepatocytes can produce fetal isozymes without prior cell division;
(c) pyruvate kinase is a stronger marker of dedifferentiation (retrodifferentiation) than aldolase; and (d) regulatory processes
of isozyme expression are different during ontogenesis, regeneration, and hepatocarcinogenesis.
This work was supported by the “Institut National de la Santé et de la Recherche Médicale” and the “Fondation pour la Recherche
Medicale Fran?aise” 相似文献
77.
78.
79.
J A Simons M J Teixeira de Mattos O M Neijssel 《Journal of general microbiology》1991,137(7):1479-1483
Klebsiella pneumoniae NCTC 418 is able to convert 2-ketogluconate intracellularly to 6-phosphogluconate by the combined action of an NADPH-dependent 2-ketogluconate reductase and gluconate kinase. Synthesis of the former enzyme was maximal under 2-ketogluconate-limited growth conditions. An instantaneous transition to a 2-ketogluconate-excess condition resulted in an acceleration of catabolism of this carbon source, accompanied by complete inhibition of biosynthesis. It is suggested that the cause of this inhibition resides in depletion of the NADPH pool due to the high rate at which NADPH is oxidized by 2-ketogluconate reductase. 相似文献
80.
Alfred Berteloot Christiane Malo Sylvie Breton Michel Brunette 《The Journal of membrane biology》1991,122(2):111-125
Summary Kinetic data in (brush-border) membrane vesicles which rely on the validity of the initial rate assumption for their interpretation and depend on tracer flux studies using the rapid filtration technique for their experimental measurement have been limited to some extent by the absence of techniques that would allow for real-time data analysis. In this paper, we report on our successful design of a fast sampling, rapid filtration apparatus (FSRFA) which seems to fill up this technical gap since showing the following characteristics: (i) rapid injection (5 msec) and mixing (less than 100 msec) of small amounts of vesicles (10–40 l) with an incubation medium (0.2–1.0 ml); (ii) fast (20 to 80 msec depending on the sample volume) and multiple (up to 18 samples at a maximal rate of 4/sec) sampling of the uptake mixture followed by rapid quenching in the stop solution (approximately 5 msec) according to a predetermined time schedule (any time combination from 0.25 to 9999 sec); and (iii) fast, automated, and sampling-synchronized filtration and washings of the quenched uptake medium (only 15–20 sec are necessary for the first filtration followed by two washings and extra filtrations). As demonstrated using adult human jejunal brush-border membrane vesicles and Na+-d-glucose cotransport as models, the FSRFA accurately reproduces the manual aspects of the rapid filtration technique while allowing for very precise initial rate determinations. Moreover, the FSRFA has also been designed to provide as much versatility as possible and, in its present version, allows for a very precise control of the incubation temperature and also permits a few efflux protocols to be performed. Finally, its modular design, which separates the fast sampling unit from the rapid filtration device, should help in extending its use to fields other than transport measurement. 相似文献