全文获取类型
收费全文 | 3890篇 |
免费 | 228篇 |
国内免费 | 6篇 |
专业分类
4124篇 |
出版年
2022年 | 18篇 |
2021年 | 29篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 66篇 |
2015年 | 80篇 |
2014年 | 87篇 |
2013年 | 267篇 |
2012年 | 190篇 |
2011年 | 187篇 |
2010年 | 122篇 |
2009年 | 132篇 |
2008年 | 216篇 |
2007年 | 225篇 |
2006年 | 209篇 |
2005年 | 212篇 |
2004年 | 225篇 |
2003年 | 221篇 |
2002年 | 221篇 |
2001年 | 112篇 |
2000年 | 85篇 |
1999年 | 104篇 |
1998年 | 53篇 |
1997年 | 58篇 |
1996年 | 34篇 |
1995年 | 41篇 |
1994年 | 30篇 |
1993年 | 46篇 |
1992年 | 61篇 |
1991年 | 61篇 |
1990年 | 67篇 |
1989年 | 54篇 |
1988年 | 61篇 |
1987年 | 45篇 |
1986年 | 55篇 |
1985年 | 48篇 |
1984年 | 36篇 |
1983年 | 30篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 27篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 15篇 |
1974年 | 12篇 |
1973年 | 15篇 |
1972年 | 9篇 |
排序方式: 共有4124条查询结果,搜索用时 15 毫秒
101.
Asano R Ikoma K Shimomura I Taki S Nakanishi T Umetsu M Kumagai I 《The Journal of biological chemistry》2011,286(3):1812-1818
Diabodies (Dbs) and tandem single-chain variable fragments (taFv) are the most widely used recombinant formats for constructing small bispecific antibodies. However, only a few studies have compared these formats, and none have discussed their binding kinetics and cross-linking ability. We previously reported the usefulness for cancer immunotherapy of a humanized bispecific Db (hEx3-Db) and its single-chain format (hEx3-scDb) that target epidermal growth factor receptor and CD3. Here, we converted hEx3-Db into a taFv format to investigate how format affects the function of a small bispecific antibody; our investigation included a cytotoxicity assay, surface plasmon resonance spectroscopy, thermodynamic analysis, and flow cytometry. The prepared taFv (hEx3-taFv) showed an enhanced cytotoxicity, which may be attributable to a structural superiority to the diabody format in cross-linking target cells but not to differences in the binding affinities of the formats. Comparable cross-linking ability for soluble antigens was observed among hEx3-Db, hEx3-scDb, and hEx3-taFv with surface plasmon resonance spectroscopy. Furthermore, drastic increases in cytotoxicity were found in the dimeric form of hEx3-taFv, especially when the two hEx3-taFv were covalently linked. Our results show that converting the format of small bispecific antibodies can improve their function. In particular, for small bispecific antibodies that target tumor and immune cells, a functional orientation that avoids steric hindrance in cross-linking two target cells may be important in enhancing the growth inhibition effect. 相似文献
102.
Isolation and Characterization of a Catabolite Repression-Insensitive Mutant of a Methanol Yeast, Candida boidinii A5, Producing Alcohol Oxidase in Glucose-Containing Medium 总被引:1,自引:0,他引:1 下载免费PDF全文
Mutants exhibiting alcohol oxidase (EC 1.1.3.13) activity when grown on glucose in the presence of methanol were found among 2-deoxyglucose-resistant mutants derived from a methanol yeast, Candida boidinii A5. One of these mutants, strain ADU-15, showed the highest alcohol oxidase activity in glucose-containing medium. The growth characteristics and also the induction and degradation of alcohol oxidase were compared with the parent strain and mutant strain ADU-15. In the parent strain, initiation of alcohol oxidase synthesis was delayed by the addition of 0.5% glucose to the methanol medium, whereas it was not delayed in mutant strain ADU-15. This showed that alcohol oxidase underwent repression by glucose. On the other hand, degradation of alcohol oxidase after transfer of the cells from methanol to glucose medium (catabolite inactivation) was observed to proceed at similar rates in parent and mutant strains. The results of immunochemical titration experiments suggest that catabolite inactivation of alcohol oxidase is coupled with a quantitative change in the enzyme. Mutant strain ADU-15 was proved to be a catabolite repression-insensitive mutant and to produce alcohol oxidase in the presence of glucose. However, it was not an overproducer of alcohol oxidase and, in both the parent and mutant strains, alcohol oxidase was completely repressed by ethanol. 相似文献
103.
104.
105.
The mRNA coding for the common precursor of corticotropin and beta-lipotropin has been purified to homogeneity from neurointermediate lobes of bovine pituitaries. The homogeneity of the mRNA preparation is evidenced by analysis of its translation product, electrophoresis on polyacrylamide gel in the presence of formamide and analysis of the kinetics of hybridization with its cDNA. The purification procedure involves the isolation of RNA from membrane-bound polysomes, chromatography on oligo(dT)-cellulose and on poly(U)-Sepharose and sucrose density gradient centrifugation. The mRNA has a molecular weight of approximately 450000, equivalent to approximately 1360 nucleotides in length, and contains a polyadenylate sequence with an average length of 68 nucleotides. The size of the mRNA is sufficiently large to encode the corticotropin/beta-lipotropin precursor. 相似文献
106.
Hidehiko Kondo Iichiro Shimomura Ken Kishida Hiroshi Kuriyama Yasunaka Makino Hitoshi Nishizawa Morihiro Matsuda Norikazu Maeda Hiroyuki Nagaretani Shinji Kihara Yoshihisa Kurachi Tadashi Nakamura Tohru Funahashi Yuji Matsuzawa 《European journal of biochemistry》2002,269(7):1814-1826
Aquaporin adipose (AQPap), which we identified from human adipose tissue, is a glycerol channel in adipocyte [Kishida et al. (2000) J. Biol. Chem. 275, 20896-20902]. In the current study, we determined the genomic structure of the human AQPap gene, and identified three AQPap-like genes that resembled (approximately 95%) AQPap, with little expression in human tissues. The AQPap promoter contained a putative peroxisome proliferator response element (PPRE) at -46 to -62, and a putative insulin response element (IRE) at -542/-536. Deletion of the PPRE abolished the pioglitazone-mediated induction of AQPap promoter activity in 3T3-L1 adipocytes. Deletion and single base pair substitution analysis of the IRE abolished the insulin-mediated suppression of the human AQPap gene. Analysis of AQPap sequence in human subjects revealed three missense mutations (R12C, V59L and G264V), and two silent mutations (A103A and G250G). The cRNA injection of the missense mutants into Xenopus oocytes revealed the absence of the activity to transport glycerol and water in the AQPap-G264V protein. In the subject homozygous for AQPap-G264V, exercise-induced increase in plasma glycerol was not observed in spite of the increased plasma noradrenaline. We suggest that AQPap is responsible for the increase of plasma glycerol during exercise in humans. 相似文献
107.
Akira Kai Hiroko Karasawa Masayuki Kikawa Kenichi Hatanaka Kei Matsuzaki Tohru Mimura Yutaro Kaneko 《Carbohydrate polymers》1998,35(3-4):271-278
Biosynthesis of branched glucan by Pestalotiopsis from media containing D-(1-13C)glucose, D-(2-13C)glucose, D-(4-13C)glucose, D-(6-13C)glucose or a mixture of D-(1-13C)glucose and D-(2-13C)glucose was carried out to elucidate biosynthetic mechanism of branched polysaccharides. 13C NMR spectra of the labeled polysaccharides were determined and assigned. Analysis of 13C NMR spectra of glucitol acetates obtained from hydrolysates of the labeled branched polysaccharides indicated that transfer of labeling from C-1 to C-3 and C-6 carbons, from C-2 to C-1, C-3 and C-5 carbons, and from C-6 to C-1 carbon. From the results the percentages of routes via which the polysaccharide is biosynthesized are estimated. They show that the biosynthesis of the polysaccharide via the Embden-Meyerhof pathway and that from lipids and proteins are more active, and the pentose cycle is less active, than in the biosynthesis of cellulose and curdlan. As for the results, labeling at C-6 carbon in the branched polysaccharide cultured from D-(6-13C)glucose was low, compared to that of cellulose and curdlan. 相似文献
108.
109.
Tohru Kobayashi Yasushi Kageyama Nobuyuki Sumitomo Katsuhisa Saeki Tsuyoshi Shirai Susumu Ito 《World journal of microbiology & biotechnology》2005,21(6-7):961-967
Summary Crystallographic analysis of the highly alkaline M-protease from an alkaliphilic Bacillus strain shows the occurrence of a unique salt bridge triad Arg19–Glu271–Arg275 (in subtilisin BPN′ numbering), which is not
found in less alkaline true subtilisins BPN′ and Carlsberg from Bacillus amyloliquefaciens and Bacillus licheniformis, respectively. Because the corresponding residues are all Gln residue in the subtilisin BPN′, Gln residue was engineered
into the position(s) 19, 271 and/or 275 in M-protease by site-directed mutagenesis. Disruptions of the salt bridge caused
the reduction of the thermostability of the mutant proteins at alkaline pH with the following decreasing order of thermal
inactivation rate; the wild-type > Arg275 → Gln > Glu271 → Gln > Arg19 → Gln/Glu271 → Gln/Arg275 → Gln > Arg19 → Gln. This
result provides the evidence that the salt bridge triad contributes to the thermostability and structural rigidity of the
highly alkaline M-protease. 相似文献
110.