全文获取类型
收费全文 | 9235篇 |
免费 | 501篇 |
国内免费 | 5篇 |
专业分类
9741篇 |
出版年
2022年 | 61篇 |
2021年 | 92篇 |
2020年 | 66篇 |
2019年 | 80篇 |
2018年 | 104篇 |
2017年 | 92篇 |
2016年 | 188篇 |
2015年 | 280篇 |
2014年 | 301篇 |
2013年 | 688篇 |
2012年 | 548篇 |
2011年 | 594篇 |
2010年 | 339篇 |
2009年 | 338篇 |
2008年 | 567篇 |
2007年 | 610篇 |
2006年 | 563篇 |
2005年 | 535篇 |
2004年 | 596篇 |
2003年 | 466篇 |
2002年 | 481篇 |
2001年 | 136篇 |
2000年 | 127篇 |
1999年 | 142篇 |
1998年 | 120篇 |
1997年 | 92篇 |
1996年 | 83篇 |
1995年 | 80篇 |
1994年 | 80篇 |
1993年 | 69篇 |
1992年 | 95篇 |
1991年 | 114篇 |
1990年 | 77篇 |
1989年 | 75篇 |
1988年 | 92篇 |
1987年 | 58篇 |
1986年 | 68篇 |
1985年 | 60篇 |
1984年 | 45篇 |
1983年 | 49篇 |
1982年 | 36篇 |
1981年 | 46篇 |
1980年 | 49篇 |
1979年 | 40篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1975年 | 23篇 |
1974年 | 32篇 |
1973年 | 32篇 |
1972年 | 21篇 |
排序方式: 共有9741条查询结果,搜索用时 15 毫秒
31.
Subhash Padhye Takeshi Kambara David N. Hendrickson Govindjee 《Photosynthesis research》1986,9(1-2):103-112
The recent model of Kambara and Govindjee for water oxidation [Kambara T. and Govindjee (1985) Proc. Natl. Acad. Sci. U.S.A., 82:6119–6123] has been extended in this paper by examining all the data in order to identify the most likely candidate for the redox-active ligand (RAL), suggested to operate between the water oxidizing complex (WOC) and Z, the electron donor to the reaction center P680. We have concluded that a very suitable candidate for RAL is the imidazole moiety of a histidine residue. The electrochemical data available on imidazole derivatives play heavily in this identification of RAL. Thus, we suggest that histidine might play the role of an electron mediator between the WOC and Z. A model of S-states in terms of their plausible chemical identity is presented here.Abbreviations J
electronic spin of ion
- P680
reaction center chlorophyll
- RAL
Redox active ligand
- Sn
state of the oxygen-evolving system
- WOC
water oxidation complex
- Z
electron donor to P680
Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement 相似文献
32.
33.
Flavonoids in the leaves of twenty-eight species belonging to the Polygonaceae were studied. Thirty-three kinds of flavonoids
were isolated, and eighteen kinds were obtained as crystals. Quercetin glycosides were commonly found in the family. In the
quercetin glycosides, 3-O-rhamnoside was most frequently found: 3-O-glucuronide is also distributed widely. Myricetin glycosides were rare. Methylated flavonols were found in some species of
the sectionsEchinocaulon andPersicaria. Eleven kinds ofC-glycosylflavones were found in the present survey, andC-glycosylflavones were distributed in all species of the genusRheum and in almost all species of the section Tiniaria.Rumex Acetosella andPolygonum suffultum are exceptional, the former contains flavone glycoside and the latterC-glycosylflavones only, as main components. 相似文献
34.
Isolation of virus causing hemorrhagic fever with renal syndrome (HFRS) through a cell culture system 总被引:4,自引:0,他引:4
T Kitamura C Morita T Komatsu K Sugiyama J Arikawa S Shiga H Takeda Y Akao K Imaizumi A Oya N Hashimoto S Urasawa 《Japanese journal of medical science & biology》1983,36(1):17-25
Twenty-three rat lung specimens collected in outbreaks of hemorrhagic fever with renal syndrome (HFRS) in three medical institutions were inoculated onto the VERO-E6 cell monolayers. After several blind passages, an agent growing serially in the cell cultures and reacting specifically with known HFRS-positive sera was isolated from two of these specimens. The two isolates were antigenically identical each other. The agent, named strain SR-11, was identified as the causative virus of HFRS by its antigenic identity with E6 cell-adapted HFRS virus, Hantaan 76-118 strain, and the specific reactions with sera from various HFRS cases. 相似文献
35.
36.
Stimulation of eicosapentaenoic acid metabolism in washed human platelets by 12-hydroperoxyeicosatetraenoic acid 总被引:2,自引:0,他引:2
Washed human platelets were not able to convert eicosapentaenoic acid (EPA) to thromboxane B3 (TXB3) and 12-hydroxyeicosapentaenoic acid (AA) to washed human platelets induced conversion of EPA to TXB3 and 12-HEPE. Esculetin, a specific inhibitor of 12-lipoxygenase, prevented the effect of AA, but cyclooxygenase inhibitor did not. The conversion of AA to TXB2 was not affected by the same dose of esculetin. These data suggest that products of AA formed by 12-lipoxygenase in human platelets have stimulatory effects on EPA metabolism. When AA was preincubated with washed human platelets, its effect on EPA conversion was reduced, suggesting that a labile product of AA formed by 12-lipoxygenase is involved in the facilitation of EPA metabolism. Addition of 12-hydroperoxyeicosatetraenoic acid directly to washed human platelets caused dose-dependent synthesis of TXB3 and 12-HEPE, while addition of 12-hydroxyeicosatetraenoic acid had no effect. Thus, 12-hydroperoxyeicosatetraenoic acid formed from AA promotes the metabolism of EPA in washed human platelets. 相似文献
37.
Dichroism of bacteriochlorophyll in cells of the photosynthetic bacterium Rhodopseudomonas palustris
1. The dichroism was measured at varied wavelengths of polarized light in “intact” cells of Rhodopseudomonas palustris and in films of air-dried lamellar fragments of the bacterium. 相似文献
38.
Mutants of Group D1Salmonella Carrying the Somatic Antigen of Group A Organisms: Isolation and Serological Characterization 总被引:2,自引:2,他引:0
O antigen mutants were obtained from Salmonella durban, a group D(1) organism, by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. Serological studies demonstrated that the mutants lost the O-9 antigen factor of the parent organism but acquired the O-2 factor specific to group A Salmonella. Lipopolysaccharides of the mutant strains contained paratose which determines the specificity of O-2 factor. Tyvelose, present in the wild-type lipopolysaccharide, was not found in the mutants. H antigens and other biological characteristics of the mutant strains were the same as those of the wild-type organism. The present finding implies that group A Salmonella species might be derived from group D(1) organisms. 相似文献
39.
40.
Isolated microspores of Chinese cabbage (Brassica campestris ssp. pekinensis) were incubated in modified NN medium containing 10% sucrose in darkness at 33°C for one day followed by culture at 25°C. After 14 days of culture, microspores developed into embryos ranging from globular to cotyledonary stage. Plants were regenerated after transfer of embryos to medium containing 3% sucrose and no plant growth regulators.Abbreviations NN
Nitsch and Nitsch
- MS
Murashige and Skoog
- NAA
naphthaleneacetic acid
- BA
6-benzylaminopurine 相似文献