全文获取类型
收费全文 | 6638篇 |
免费 | 460篇 |
出版年
2023年 | 34篇 |
2022年 | 33篇 |
2021年 | 112篇 |
2020年 | 73篇 |
2019年 | 83篇 |
2018年 | 101篇 |
2017年 | 97篇 |
2016年 | 156篇 |
2015年 | 331篇 |
2014年 | 346篇 |
2013年 | 412篇 |
2012年 | 553篇 |
2011年 | 515篇 |
2010年 | 308篇 |
2009年 | 276篇 |
2008年 | 401篇 |
2007年 | 423篇 |
2006年 | 412篇 |
2005年 | 316篇 |
2004年 | 329篇 |
2003年 | 324篇 |
2002年 | 322篇 |
2001年 | 73篇 |
2000年 | 57篇 |
1999年 | 82篇 |
1998年 | 78篇 |
1997年 | 54篇 |
1996年 | 53篇 |
1995年 | 68篇 |
1994年 | 37篇 |
1993年 | 55篇 |
1992年 | 42篇 |
1991年 | 39篇 |
1990年 | 43篇 |
1989年 | 37篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 32篇 |
1985年 | 30篇 |
1984年 | 39篇 |
1983年 | 35篇 |
1982年 | 29篇 |
1981年 | 20篇 |
1979年 | 22篇 |
1978年 | 25篇 |
1977年 | 27篇 |
1976年 | 12篇 |
1975年 | 15篇 |
1974年 | 17篇 |
1971年 | 12篇 |
排序方式: 共有7098条查询结果,搜索用时 781 毫秒
41.
Johan Kumlien Torbjörn Frejd Göran Magnusson David Zopf Arne Lundblad 《Glycoconjugate journal》1986,3(1):85-94
The tetrasaccharide, Glc1-6Glc1-4Glc1-4Glc, denoted (Glc)4, is a limit dextrin formed by amylolytic degradation of glycogen. In order to evaluate the possible clinical importance of (Glc)4 excretion as an indicator of certain physiological and pathological conditions, we have developed a new rapid and inexpensive immunoassay using a monoclonal antibody raised against (Glc)4 glycosidically-linked to a carrier protein. As the antibody is highly specific, it can be used to measure native (Glc)4 directly, without the chemical reduction step required in previous methods. A new type of non-equilibrium ELISA inhibition test was developed based on the capacity of free (Glc)4 to decrease initial rates of antibody binding to (Glc)4-coated microtiter wells. The method is highly reproducible and is as sensitive and accurate as the gas chromatography method or radioimmunoassay used previously.Abbreviations (Glc)4
Glc1-6Glc1-4Glc1-4Glc
- KLH
keyhole limpet hemacyanin
- BSA
bovine serum albumin
- PEG
polyethylene glycol 相似文献
42.
43.
Suraj B. Baloda Gunnar Fröman Johan E. Peeters Torkel Wadström 《FEMS microbiology letters》1986,34(2):225-229
Abstract 32 different strains of Escherichia coli isolated from rabbits with diarrhoea were studied for cell-surface properties which may be involved in intestinal colonisation. Strains isolated from diarrhoeic suckling (6 strains) and weaning (26 strains) rabbits which were shown to attach to brush borders in vivo, showed high relative cell-surface hydrophobicity as determined by the Salt Aggregation Test (SAT) when grown on Colonisation Factor Antigen (CFA) agar at 33°C. Cells of these strains grown to express surface hydrophobicity were also defined as high, moderate or low binders of 125 I-fibronectin or its 125 I-29-kDa fragment in a standard binding assay. Based on these findings, we propose that binding to intestinal cell surface (mucus)-associated fibronectin may be an early important step in intestinal colonisation of the small bowel in enteropathogenic E. coli (EPEC) diarrhoea in rabbits and other animal species. 相似文献
44.
Ole G. Mouritsen 《生物化学与生物物理学报:生物膜》1983,731(2):217-221
The gel-to-fluid first-order melting transition of lipid bilayers is simulated by the use of a microscopic interaction model which includes a variable number of lipid-chain conformational states. The results suggest that the experimental observation of ‘continuous melting’ in pure wet lipid bilayers, rather than being ascribed to the presence of impurities, may be explained as a result of kinetically caused metastability of intermediate lipid-chain conformations. 相似文献
45.
Frans van Cauwelaert Ignace Hanssens Willy Herreman Jean-Claude van Ceunebroeck Johan Baert Hugo Berghmans 《生物化学与生物物理学报:生物膜》1983,727(2):273-284
The characteristics of small unilamellar, large unilamellar and large multilamellar vesicles of dimyristoylphosphatidylcholine and their interaction with α-lactalbumin are compared at pH 4. (1) By differential scanning calorimetry and from steady-state fluorescence anisotropy data of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene it is shown that the transition characteristics of the phospholipids in the large unilamellar vesicles resemble more those of the multilamellar vesicles than of the small unilamellar vesicles. (2) The size and composition of the lipid-protein complex formed with α-lactalbumin around the transition temperature of the lipid are independent of the vesicle type used. Fluorescence anisotropy data indicate that in this complex the motions of the lipid molecules are strongly restricted in the presence of α-lactalbumin. (3) The previous data and a comparison of the enthalpy changes, , of the interaction of the three vesicle types with α-lactalbumin allow us to derive that the enthalpy state of the small unilamellar vesicles just below 24°C is about 24 kJ/mol lipid higher than the enthalpy state of both large vesicle types at the same temperature. The abrupt transition from endothermic to exothermic values around 24°C for large vesicles approximates the transition enthalpy of the pure phospholipid 相似文献
46.
An apparatus suitable for the recovery of proteins from polyacrylamide gels on a milligram scale by displacement electrophoresis (isotachophoresis) is described along with a buffer system that is suitable for this purpose with most proteins. The technique is illustrated by the recovery of a protein from a 15% polyacrylamide gel. The recovery was almost quantitative and the eluted protein showed little contamination upon quantitative amino acid analysis and automatic Edman degradation. 相似文献
47.
A neutral growth inhibitor, isolated from methanolic extracts of sunflower seedlings, was characterized by spectral data as caprolactam. Light-grown se 相似文献
48.
Rob J.M. Moormann Johan T. den Dunnen Leon Mulleners Peter Andreoli Hans Bloemendal John G.G. Schoenmakers 《Journal of molecular biology》1983,171(4):353-368
Two complementary DNA clones pRLγ-2 and pRLγ-3 of different rat lens γ-crystallin messenger RNAs have been used to identify γ-crystallin gene sequences in rat genomic DNA. Subsequently, the DNA present in the 18,000 to 20,000 bases region of the EcoRI digest, giving rise to a strong doublet hybridization signal, was cloned in λ phage Charon-4A. One of the clones, λRCHγ-3, carrying an insert of 17,500 bases has been characterized in detail. From analysis at the restriction enzyme level with 5′-, “middle” and 3′-specific subprobes of pRLγ-3 it could be deduced that λRCHγ-3 contains only one γ-crystallin gene. The coding sequences of this gene are interrupted by intronic DNA. The primary structure of this gene and its flanking regions have been established by sequencing the relevant regions of a subclone of λRCHγ-3, designated pRCHγ-3.1. The sequence data show that the γ-crystallin gene extends over 2700 bases of rat genomic DNA. The gene is split by two introns, one of 87 base-pairs after the third translation codon and a large one of 1880 base-pairs after codon 84. The mosaic structure of the gene is strictly co-linear with the structure of the γ-crystallin polypeptide in that the large intron is positioned in a region which specifies the so-called “connecting peptide” and which links the two highly symmetrical and homologous protein domains. Although expected from the cDNA and protein sequence no introns were observed between the coding regions in the DNA specifying the two homologous folding motifs present in each protein domain. The relevance of this phenomenon in terms of the evolution of the mature γ-crystallin gene is discussed. 相似文献
49.
Na+, Cl− cotransport in Ehrlich ascites tumor cells activated during volume regulation (regulatory volume increase) 总被引:2,自引:0,他引:2
Else K. Hoffmann Carsten Sjøholm Lars Ole Simonsen 《The Journal of membrane biology》1983,76(3):269-280
Ehrlich ascites cells were preincubated in hypotonic medium with subsequent restoration of tonicity. After the initial osmotic shrinkage the cells recovered their volume within 5 min with an associated KCl uptake. The volume recovery was inhibited when NO-3 was substituted for Cl-, and when Na+ was replaced by K+, or by choline (at 5 mM external K+). The volume recovery was strongly inhibited by furosemide and bumetanide, but essentially unaffected by DIDS. The net uptake of Cl- was much larger than the value predicted from the conductive Cl- permeability. The undirectional 36Cl flux, which was insensitive to bumetanide under steady-state conditions, was substantially increased during regulatory volume increase, and showed a large bumetanide-sensitive component. During volume recovery the Cl- flux ratio (influx/efflux) for the bumetanide-sensitive component was estimated at 1.85, compatible with a coupled uptake of Na+ and Cl-, or with an uptake via a K+,Na+,2Cl- cotransport system. The latter possibility is unlikely, however, because a net uptake of KCl was found even at low external K+, and because no K+ uptake was found in ouabain-poisoned cells. In the presence of ouabain a bumetanide-sensitive uptake during volume recovery of Na+ and Cl- in nearly equimolar amounts was demonstrated. It is proposed that the primary process during the regulatory volume increase is an activation of an otherwise quiescent, bumetanide-sensitive Na+,Cl- cotransport system with subsequent replacement of Na+ by K+ via the Na+/K+ pump, stimulated by the Na+ influx through the Na+,Cl- cotransport system. 相似文献
50.
Anders Fjose Ian F. Pryme Johan R. Lillehaug 《Molecular and cellular biochemistry》1983,56(2):137-144
Summary After transfer of Krebs II ascites cells from the mouse peritoneum to suspension culture addition of the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) causes an early stimulation of 3H-choline incorporation into phosphatidylcholine (PC). Choline transport into the treated cells, however, was unaffected. Within 30 min of TPA treatment 3H-choline incorporation was almost 300% above the control level. During a 5 hr period of suspension culture the overall patterns of 3H-choline incorporation were similar in TPA-treated and control cultures though the rate was greatly accentuated by the presence of the phorbol ester. Incubation of cells with cycloheximide prior to incubation with TPA did not result in an inhibition of the TPA-directed 3H-choline incorporation. After 3 hr incubation with TPA there were large increases in radioactivity in all subcellular fractions. At 20 hr, however, the values were not far from those of the control. During the first 3 hr of incubation with TPA the incorporation of 3H-choline into light rough (LR) and smooth (S) membranes was stimulated to levels of 400% and 320% respectively above control values. At later times the profiles of radioactivity in membrane subfractions in TPA-treated and control cultures were similar. The results illustrate an early effect of TPA on PC biosynthesis in Krebs II ascites cells while at later times of incubation the stimulatory effect was virtually abolished. 相似文献