全文获取类型
收费全文 | 20508篇 |
免费 | 1696篇 |
国内免费 | 5篇 |
出版年
2023年 | 78篇 |
2022年 | 228篇 |
2021年 | 437篇 |
2020年 | 242篇 |
2019年 | 311篇 |
2018年 | 433篇 |
2017年 | 359篇 |
2016年 | 645篇 |
2015年 | 1050篇 |
2014年 | 1195篇 |
2013年 | 1435篇 |
2012年 | 1769篇 |
2011年 | 1682篇 |
2010年 | 1076篇 |
2009年 | 956篇 |
2008年 | 1286篇 |
2007年 | 1318篇 |
2006年 | 1130篇 |
2005年 | 1085篇 |
2004年 | 1051篇 |
2003年 | 957篇 |
2002年 | 920篇 |
2001年 | 218篇 |
2000年 | 164篇 |
1999年 | 163篇 |
1998年 | 240篇 |
1997年 | 156篇 |
1996年 | 138篇 |
1995年 | 129篇 |
1994年 | 114篇 |
1993年 | 107篇 |
1992年 | 89篇 |
1991年 | 74篇 |
1990年 | 70篇 |
1989年 | 67篇 |
1988年 | 60篇 |
1987年 | 59篇 |
1986年 | 48篇 |
1985年 | 60篇 |
1984年 | 54篇 |
1983年 | 69篇 |
1982年 | 41篇 |
1981年 | 36篇 |
1980年 | 40篇 |
1979年 | 35篇 |
1978年 | 44篇 |
1977年 | 37篇 |
1976年 | 33篇 |
1975年 | 25篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Frank Thévenod Martine Dehlinger-Kremer Thomas P. Kemmer Anna-Luise Christian Barry V. L. Potter Irene Schulz 《The Journal of membrane biology》1989,109(2):173-186
Summary We have measured Ca2+ uptake and Ca2+ release in isolated permeabilized pancreatic acinar cells and in isolated membrane vesicles of endoplasmic reticulum prepared from these cells. Ca2+ uptake into cells was monitored with a Ca2+ electrode, whereas Ca2+ uptake into membrane vesicles was measured with45Ca2+. Using inhibitors of known action, such as the H+ ATPase inhibitors NBD-Cl and NEM, the Ca2+ ATPase inhibitor vanadate as well as the second messenger inositol 1,4,5-trisphosphate (IP3) and its analog inositol 1,4,5-trisphosphorothioate (IPS3), we could functionally differentiate two non-mitochondrial Ca2+ pools. Ca2+ uptake into the IP3-sensitive Ca2+ pool (IsCaP) occurs by a MgATP-dependent Ca2+ uptake mechanism that exchanges Ca2+ for H+ ions. In the absence of ATP Ca2+ uptake can occur to some extent at the expense of an H+ gradient that is established by a vacuolar-type MgATP-dependent H+ pump present in the same organelle. The other Ca2+ pool takes up Ca2+ by a vanadate-sensitive Ca2+ ATPase and is insensitive to IP3 (IisCaP). The IsCaP is filled at higher Ca2+ concentrations (10–6 mol/liter) which may occur during stimulation. The low steady-state [Ca2+] of 10–7 mol/liter is adjusted by the IisCaP.It is speculated that both Ca2+ pools can communicate with each other, the possible mechanism of which, however, is at present unknown. 相似文献
112.
Ihssane Bouhtiauy Yassin Choukri Christian Turpin Didier Gauthier 《Neurochemical research》1989,14(7):635-640
We have studied the cytoskeletal nature of a brain subcellular fraction previously shown to contain polyribosomes. We have identified the major proteins of this fraction by electrophoretic comparison to a standard cytoskeletal fraction and by immunodetection. These methods have shown the presence of actin, glial fibrillary acidic protein, and neurofilament triplet proteins. We have also studied the effect of various ions and nonionic detergents on the stability of this structure. It was stable in presence of Triton X-100 up to 2% but disrupted by 200 mM K+ acetate.Abbreviations CMT
cytomatrix
- CSK
cytoskeleton
- DOC
sodium deoxycholate
- DTT
dithiothreitol
- EGTA
ethylenglycolbis (-Ether)-N,N-N-N-Tetraacetic Acid
- GFAP
glial fibrillary acidic protein
- PR
polyribosome
- PRCMC
polyribosomes-cytomatrix complex 相似文献
113.
The loading of amino acids and nitrate into the xylem was investigated by collection and analysis of root-pressure exudate from the cut hypocotyl stumps of seedlings of Ricinus communis L. Glutamine was found to be the dominant amino acid in the exudate and also to be the amino acid which is transferred to the xylem most rapidly and accumulated to the greatest extent. The comparison between uptake and xylem loading showed significant differences in specificity between these two transport reactions, indicating a different set of transport systems. Nitrate is transferred to the xylem at a higher relative rate than any amino acid despite the great nitrate-storage capacity of the root system. Thus the supply of nitrate to Ricinus plants leads to enhanced nitrogen allocation to the shoots. 相似文献
114.
Daniel Gygax Henk Nachtegaal Oreste Ghisalba René Lattmann Hans-Peter Schär Christian Wandrey Markus B. Streiff 《Applied microbiology and biotechnology》1990,32(6):621-626
Summary The production of d-ribulose-5-phosphate in an enzyme membrane reactor was examined. Phosphoryl transfer from ATP to d-ribulose was catalysed by d-ribulokinase isolated from Klebsiella pneumoniae. For production of d-ribulose-5-phosphate the phosphoryl donor ATP was used either in stoichiometric or in catalytic amounts. Using catalytic amounts of ATP requires a second enzyme, e.g. pyruvate kinase, to regenerate ATP. The kinetic parameters for d-ribulokinase and pyruvate kinase were determined to calculate the performance of an enzyme membrane reactor for continuous production of d-ribulose-5-phosphate. Both processes operated for more than 200 h. Regardless of whether ATP was used in catalytic or stoichiometric amounts, about the same production parameters were determined. In continuous production space/time yields of 117 g (with ATP regeneration) and 103 g (without ATP regeneration) of d-ribulose-5-phosphate 1–1 per day were reached.Offprint requests to: D. Gygax 相似文献
115.
Rolf Wichmann Christian Wandreg Joachim Große-Wiesmann 《Applied microbiology and biotechnology》1990,32(4):373-379
Summary Continuous production ofl-leucine was carried out withCorynebacterium glutamicum, strain ATCC 13032 starting from-ketoisocaproic acid as the precursor, glucose as the carbon source and ammonium sulphate as the nitrogen source, with biotin in a mineral medium. By means of cross-flow microfiltration or centrifugal separation for cell retention in continuous fermentation an increase in cell density was achieved and the product solution was obtained cell-free. The cells were concentrated to over 70 g cell dry mass/1. In experiments of up to 42 days, conversion rates of 85%–99% andl-leucine yields of 85%–93% were achieved. With a substrate residence time of 3.6 h, 114 mmol/1l-leucine was produced with a space-time yield of 97 g/1 per day. A scale-up of the fermentation volume from 4 to 1001 provided comparable results. 相似文献
116.
Pascale Andre Christian Capo Anne Marie Benoliel Michel Buferne Pierre Bongrand 《Cell biochemistry and biophysics》1990,16(1-2):13-34
Fluorescent probes are widely used to study cell structure and function. However, few reports were devoted to a quantitative analysis of the intracellular distribution of fluorescent markers. In the present work, we describe the topographical changes of surface and cytoskeletal markers on individual cells subjected to adhesive or mechanical interaction. Conjugates were prepared with a cytotoxic T-lymphocyte clone and target cells. Specific antigens, membrane phospholipids, surface glycoconjugates, and polymerized actin were labeled with fluorescent antibodies or biochemical probes. The analysis of fluorescence distributions in conjugates demonstrated a selective reorganization of the plasma membrane with a gathering of some molecular species in the intercellular adhesion area. Furthermore, individual phagocytic cells were sucked into glass micropipets, then stained with fluorescent phallacidin to analyze the effect of mechanical efforts on the cytoskeleton organization. The concentration of polymerized actin was found to be similar in mechanicallyinduced protrusions and whole cells. It is concluded that adhesive interactions may result in marked cell polarization and formation of membrane zones with a particular biochemical composition. The submembranar cytoskeleton might play a role in this process. 相似文献
117.
Marianne Horoyan Anne-Marie Benoliel Christian Capo Pierre Bongrand 《Cell biochemistry and biophysics》1990,17(3):243-256
We combined fluorescence labeling, digital image processing, and micromanipulation to investigate the intracellular events induced by inflicting a mechanical stress on rat basophilic leukemia cells. Our findings were as follows:
- Most cells displayed a localized calcium rise in response to micropipet aspiration. This represented an average threefold increase as compared to resting level, and it was observed during the first 10 s following aspiration. A slow return to initial level occurred within about 3 min. Further, this calcium rise involved a mobilization of intracellular stores, since it was not prevented by adding a calcium chelator into the extracellular medium.
- All micropipet-aspirated cells displayed a local accumulation of microfilaments, with a preferential localization in the cell protrusions or near the pipet tips.
- No absolute correlation was found between the localization of calcium rise and cytoskeletal accumulation.
- Cell deformability was decreased when intracellular calcium was maintained at a constant (high or low) level with ionomycin and/or EGTA.
118.
Christian Damgaard 《Evolution; international journal of organic evolution》1996,50(4):1425-1431
The fixation rates of selfing rate modifiers were found by stochastic simulation in an infinite site model, including effects of several deleterious alleles with variable effects, which were randomly distributed in the genome without assuming any pollen discounting. Previous results on the evolution of selfing obtained by more precise methods were in this study further validated, and it was concluded that the effect of genetic associations on the evolution of mating systems is small except in the case of full pollen discounting. Furthermore, attention was given to the uneven distribution of the genetic load in the population, and the accompanying large among-genome variation in fixation rates. This among-genome variation will be of significance for the evolution of mating systems. 相似文献
119.
Christian Tessier Gian-Paolo Rossini Jean-François Pageaux Hélène Cohen Michel Lagarde Christian Laugier Jean-Michel Fayard 《FEBS letters》1996,390(3):311-314
Rat uterine stromal cells (UIII) express pancreatic type PLA2 (PLA2-I) receptor and internalize the enzyme bound to receptors. Here, we investigate the proliferating effect and alterations in binding of PLA2-I. There is a dramatic decline in PLA2-I binding in UIII cells as they progress from a nonconfluent proliferating state (40,000 sites/cell) to a confluent state (1300 sites/cell). Intracellular concentration of PLA2-I changed with the alteration in binding, suggesting that regulation in the PLA2 binding capacity may have important implications in growth control mechanisms. 相似文献
120.