全文获取类型
收费全文 | 468447篇 |
免费 | 57670篇 |
国内免费 | 286篇 |
专业分类
526403篇 |
出版年
2018年 | 4127篇 |
2017年 | 3768篇 |
2016年 | 5972篇 |
2015年 | 9025篇 |
2014年 | 10042篇 |
2013年 | 13986篇 |
2012年 | 16172篇 |
2011年 | 16158篇 |
2010年 | 10668篇 |
2009年 | 9941篇 |
2008年 | 14084篇 |
2007年 | 14567篇 |
2006年 | 13200篇 |
2005年 | 13009篇 |
2004年 | 12720篇 |
2003年 | 12149篇 |
2002年 | 11593篇 |
2001年 | 21943篇 |
2000年 | 22012篇 |
1999年 | 17670篇 |
1998年 | 6490篇 |
1997年 | 6683篇 |
1996年 | 6469篇 |
1995年 | 5882篇 |
1994年 | 5907篇 |
1993年 | 5744篇 |
1992年 | 13870篇 |
1991年 | 13164篇 |
1990年 | 12828篇 |
1989年 | 12670篇 |
1988年 | 11329篇 |
1987年 | 10939篇 |
1986年 | 10020篇 |
1985年 | 9819篇 |
1984年 | 8355篇 |
1983年 | 7187篇 |
1982年 | 5659篇 |
1981年 | 5128篇 |
1980年 | 4771篇 |
1979年 | 7832篇 |
1978年 | 6041篇 |
1977年 | 5533篇 |
1976年 | 5162篇 |
1975年 | 5445篇 |
1974年 | 5892篇 |
1973年 | 5754篇 |
1972年 | 5176篇 |
1971年 | 4803篇 |
1970年 | 3993篇 |
1969年 | 3918篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
G J Moore 《International journal of peptide and protein research》1985,26(5):469-481
The possible existence of intramolecular interactions involving the tyrosine and histidine residues in angiotensin II has been investigated by measuring the reactivities of the functional groups in the molecule. Angiotensin II catalyzed the hydrolysis of p-nitrophenylacetate in the pH range 6.6-8.2 at higher rates than were consistent with the reactivities of the free constituent functional groups, and had 2-4% of the activity of chymotrypsin between pH 6.6 and 7.5. Treatment of angiotensin II with acetic anhydride demonstrated that the tyrosine hydroxyl and the imidazole side-chain in angiotensin II acetylated and deacetylated at markedly higher rates than for the free amino acids, indicating increased nucleophilicities and the presence of intrinsic deacetylation mechanisms for these residues in angiotensin II. These findings are consistent with the presence of tyrosine hydroxyl-histidine-carboxylate charge relay system in ANG II in aqueous environments, and suggest that ANG II may act at membrane receptors by a mechanism which is analogous to that operating in serine proteases. 相似文献
73.
C. A. STACE C. E. JARVIS 《Botanical journal of the Linnean Society. Linnean Society of London》1985,91(3):435-444
STACE, C. A. & JARVIS, C. E., 1985. TypiHcation of Linnaean taxa of annual Poaceae: Poeae related to Vulpia and Desmazeria. The status and typification of 15 Linnaean species of annual grasses related to Vulpia and Desmazeria are discussed. Of these 15, eight are represented by holotypes or lectotypes in LINN, two by lectotypes in Herb. A. van Royen (L), and one by a neotype in LINN. One (Festuca marina) is based on a pre-Linnaean polynomial and is represented by a lectotype in Herb. Sloane (BM); one (Cynosurus durus) has no known type specimens and we have chosen a Barrelier (1714) illustration as lectotype; one (Nardus aristatus) is an illegitimate name change for Nardus incurvus Gouan, for which we have selected a Scheuchzer (1719) illustration as lectotype; and finally Festuca incrassala appeared on a cancelled page of Species Plantarum and has no nomenclatural standing. 相似文献
74.
75.
76.
Complementarity of regulation for the two glutamine synthetases from Bacillus caldolyticus, an extreme thermophile 总被引:1,自引:0,他引:1
F C Wedler D S Shreve K E Fisher D J Merkler 《Archives of biochemistry and biophysics》1981,211(1):276-287
Chromatophores from Rhodopseudomonas capsulata cells grown semiaerobically in the dark oxidize NADH, succinate, and dichlorophenolindophenol. In the presence of N3? these activities are inhibited, but light induces oxidation of dichlorophenolindophenol with O2 as a terminal electron acceptor. Cyanide also inhibits electron transport but much higher concentrations are required to inhibit the photooxidation than the dark oxidation. The photooxidation was studied in a mutant strain of Rhodopseudomonas capsulata (YIV) which cannot grow anaerobically in the light, but similarly to the wild type, grows in the presence of oxygen. Chromatophores from YIV mutant catalyze photophosphorylation and dark oxidation activities with the same properties as those of the wild type. However, the rate of photooxidation in the mutant is only one-third that of the wild type. Based on the differential inhibitor sensitivity and on the mutation it is suggested that the photooxidase is different from the two respiratory oxidases and that this photooxidation activity might be essential for growth of the cells under anaerobic conditions in the light. 相似文献
77.
78.
An apparatus for polyacrylamide slab gel electrophoresis is decribed which combines all parts into one integral unit. It eliminates several steps in the process of sealing, pouring, and setting the gels. Construction is easy with modest workshop facilities and the design easily adapted to suit most requirements. The apparatus provides a high degree of versatility and is suitable for use with many slab gel electrophoretic techniques. 相似文献
79.
80.
Conditions for breaking various medically important yeasts using glass beads, 30 ml Corex centrifuge tubes, and a Vortex mixer were determined. From 75–95% ofCandida hyphal cells and all species of yeasts exceptSporothrix schenckii were broken when 10 g of 0.45–0.50 mm glass beads, 50–300 mg of wet cells in 5 ml of buffer, and 90 s of vortexing were employed. Yeasts ofSporothrix schenckii broke more efficiently when 0.25–0.30 mm beads were used. 相似文献