全文获取类型
收费全文 | 20273篇 |
免费 | 1897篇 |
国内免费 | 12篇 |
出版年
2023年 | 102篇 |
2022年 | 87篇 |
2021年 | 562篇 |
2020年 | 267篇 |
2019年 | 390篇 |
2018年 | 438篇 |
2017年 | 343篇 |
2016年 | 591篇 |
2015年 | 985篇 |
2014年 | 1021篇 |
2013年 | 1400篇 |
2012年 | 1603篇 |
2011年 | 1575篇 |
2010年 | 978篇 |
2009年 | 847篇 |
2008年 | 1221篇 |
2007年 | 1198篇 |
2006年 | 1077篇 |
2005年 | 1018篇 |
2004年 | 920篇 |
2003年 | 858篇 |
2002年 | 829篇 |
2001年 | 199篇 |
2000年 | 153篇 |
1999年 | 181篇 |
1998年 | 169篇 |
1997年 | 140篇 |
1996年 | 116篇 |
1995年 | 110篇 |
1994年 | 116篇 |
1993年 | 112篇 |
1992年 | 125篇 |
1991年 | 109篇 |
1990年 | 101篇 |
1989年 | 86篇 |
1988年 | 93篇 |
1987年 | 74篇 |
1986年 | 67篇 |
1985年 | 94篇 |
1984年 | 99篇 |
1983年 | 63篇 |
1982年 | 82篇 |
1981年 | 71篇 |
1980年 | 69篇 |
1979年 | 77篇 |
1978年 | 57篇 |
1977年 | 61篇 |
1976年 | 66篇 |
1975年 | 69篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
71.
Frans P. Houwen Jeannette Plokker Alfons J. M. Stams Alexander J. B. Zehnder 《Archives of microbiology》1990,155(1):52-55
Enzyme measurements were carried out with crude cell-free extracts of the propionate oxidizing coculture of Syntrophobacter wolinii and Desulfovibrio G11. Using cell-free extracts of a pure culture of Desulfovibrio G11 as a blank, most of the enzymes involved in the methylmalonyl-CoA pathway for propionate oxidation, including a propionyl-CoA: oxaloacetate transcarboxylase, were demonstrated in S. wolinii. 相似文献
72.
Purification and some properties of the methyl-CoM reductase of Methanothrix soehngenii 总被引:1,自引:0,他引:1
Mike S.M. Jetten Alfons J.M. Stams Alexander J.B. Zehnder 《FEMS microbiology letters》1990,66(1-3):183-186
Abstract The methyl-CoM reductase from Methanothrix soehngenii was purified 18-fold to apparent homogeneity with 50% recovery in three steps. The native molecular mass of the enzyme estimated by gel-fitration was 280 kDa. SDS-polyacrylamide gel electrophoresis revealed three protein bands corresponding to M r 63 900, 41 700 and 30 400 Da. The methyl-coenzyme M reductase constitutes up to 10% of the soluble cell protein. The enzyme has K m apparent values of 23 μM and 2 mM for N -7-mercaptoheptanoylthreonine phosphate (HS- HTP = component B ) and methyl-coenzyme M (CH3 CoM) respectively. At the optimum pH of 7.0 60 nmol of methane were formed per min per mg protein. 相似文献
73.
74.
Reductive dechlorination of 1,2-dichloroethane and chloroethane by cell suspensions of methanogenic bacteria 总被引:4,自引:0,他引:4
Christof Holliger Gosse Schraa Alfons J. M. Stams Alexander J. B. Zehnder 《Biodegradation》1990,1(4):253-261
Concentrated cell suspensions of methanogenic bacteria reductively dechlorinated 1,2-dichloroethane via two reaction-mechanisms: a dihalo-elimination yielding ethylene and two hydrogenolysis reactions yielding chloroethane and ethane, consecutively. The transformation of chloroethane to ethane was inhibited by 1,2-dichloroethane. Stimulation of methanogenesis caused an increase in the amount of dechlorination products formed, whereas the opposite was found when methane formation was inhibited. Cells of Methanosarcina barkeri grown on H2/CO2 converted 1,2-dichloroethane and chloroethane at higher rates than acetate or methanol grown cells.Abbreviations BrES
2-bromoethanesulfonic acid
- CA
chloroethane
- 1,2-DCA
1,2-dichloroethane
- F430
Ni(II)tetrahydro-(12, 13)-corphin with an uroporphinoid (III) ligand skeleton 相似文献
75.
Abstract. The distal inner medullary collecting duct (IMCD) is critical in the urinary concentrating process, in part because it is the site of vasopressin (AVP)-regulated permeability to urea. The purpose of these experiments was to develop a cell culture model of the IMCD on permeable structure and to characterize the responsiveness to AVP. Rat IMCD cells were grown to confluence on collagen-coated Millipore filters glued onto plastic rings. To assess the time required to achieve confluence, the transepithelial resistance was measured periodically and was found to be stable after 2 weeks, at a maximal value of 595 ± 22 ω cm2 . In separate monolayers the effect of AVP on inulin and urea permeability was determined. While inulin permeability was unchanged after AVP, urea permeability increased from 6.0 ± 0–4 to peak values of 16.0 ± 3–8(10nM),23.1 ± 3–9(1 μM)and28 1 ± 4–9(10μM) X 10-6 cms-1 ( n = 24). In 10 other monolayers, after the addition of 1 mM 8-Br-cAMP, urea permeability increased from 5.1 ±0–3 to 8.1 ± 1–6 times 10-6 cm s-1 and, after 8-Br-cAMP +3-isobutyl-l-methylxanthine, to 12.2 ± 0–7 times 10-6 cms-1 . We conclude that rat IMCD cells grown in culture exhibit the characteristics of a 'tight' epithelium. Inulin and urea permeability are not different in the absence of AVP, consistent with high resistance junctional complexes. Furthermore, IMCD cells retain the capacity for AVP-regulated urea permeability, a characteristic feature of this nephron segment in vivo. 相似文献
76.
Hans Georg B?umert Akitsugu Kenmoku Gert Middelhoff Franz Ortanderl Alexander Thrun Heinz Faulstich Wolfgang Schiebler Hugo Fasold 《Journal of Protein Chemistry》1988,7(5):571-580
With the aid of tartryl-bis--aminocaprylazide artificial dimers were produced from F actin from rabbit striated muscle. These derivatives will not polymerize by themselves but are able to copolymerize fully with native G actin. By modification of a single side chain per dimer, this copolymerization was completely inhibited. The dimers are able to activate subfragment I ATPase of myosin and bind to DNase I with inactivation of the enzyme in the same manner as native G actin. Within the dimer, one ADP is immobilized and will exchange against ATP extremely slowly. The dimers do not bind to the mushroom toxin phalloidin. 相似文献
77.
Characterization of an antigenically related family of cell-type specific proteins implicated in slug migration in Dictyostelium discoideum 总被引:1,自引:0,他引:1
Stephen Alexander Elizabeth Smith Loralie Davis rew Gooley Suzanne B. Por Lois Browne Keith L. Williams 《Differentiation; research in biological diversity》1988,38(2):82-90
The monoclonal antibody MUD50 recognizes a group of developmentally regulated proteins, which are almost exclusively expressed by prespore cells in developing aggregates of Dictyostelium discoideum. Some of these antigens are integrally associated with the cell membrane, as assessed by physical and detergent-fractionation procedures. The MUD50-reactive proteins are glycosylated and some are phosphorylated. Post-translational modification is the common antigenic feature that is recognized by the MUD50 antibody in these cell-type-specific proteins. A glycosylation-defective mutant, DL118, (modB) does not express the MUD50 epitope, but does express the MUD52 epitope, which is found on a different group of glycoproteins. Therefore, we conclude that MUD50 recognizes a particular carbohydrate epitope on a restricted group of proteins. These proteins are structurally diverse, but are apparently involved in the maintenance of structure and movement of the multicellular D. discoideum slug. 相似文献
78.
The cyanobacterial photosystem, I complex from Synechococcus sp. PCC6301 contains polypeptides of apparent Mr of 70,000, 18,000, 17,700, 16,000 and 10,000. Procedures were developed for the purification of the Mr 17,700 and 10,000 polypeptides. Amino acid analyses showed the absence of cystine and cysteine from these polypeptides. Amino-terminal sequences of 98 residues for the Mr 17,700 polypeptide and of 42 residues for the Mr 10,000 polypeptide were determined. Studies of pigment distribution within the photosystem I complex indicated that the binding of chlorophyll a and -carotene is in part dependent on the presence of these polypeptides.Abbreviations PSI
photosystem I
- P700
reaction center of PSI
- SDS
sodium dodecylsulfate
- TBS
tris-buffered saline
- TTBS
TBS containing Tween-20 相似文献
79.
80.