全文获取类型
收费全文 | 1100272篇 |
免费 | 121278篇 |
国内免费 | 1237篇 |
出版年
2018年 | 10295篇 |
2017年 | 9668篇 |
2016年 | 14078篇 |
2015年 | 19653篇 |
2014年 | 22971篇 |
2013年 | 32290篇 |
2012年 | 36585篇 |
2011年 | 37246篇 |
2010年 | 25250篇 |
2009年 | 23040篇 |
2008年 | 32886篇 |
2007年 | 33832篇 |
2006年 | 31909篇 |
2005年 | 30652篇 |
2004年 | 30579篇 |
2003年 | 29161篇 |
2002年 | 28316篇 |
2001年 | 48383篇 |
2000年 | 48429篇 |
1999年 | 38773篇 |
1998年 | 14326篇 |
1997年 | 14609篇 |
1996年 | 13845篇 |
1995年 | 13026篇 |
1994年 | 12563篇 |
1993年 | 12439篇 |
1992年 | 32163篇 |
1991年 | 31383篇 |
1990年 | 30600篇 |
1989年 | 29777篇 |
1988年 | 27712篇 |
1987年 | 26102篇 |
1986年 | 24340篇 |
1985年 | 24240篇 |
1984年 | 20162篇 |
1983年 | 17200篇 |
1982年 | 13104篇 |
1981年 | 11804篇 |
1980年 | 10951篇 |
1979年 | 18611篇 |
1978年 | 14717篇 |
1977年 | 13188篇 |
1976年 | 12196篇 |
1975年 | 13717篇 |
1974年 | 14745篇 |
1973年 | 14597篇 |
1972年 | 13059篇 |
1971年 | 11979篇 |
1970年 | 10244篇 |
1969年 | 9929篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
L B Andersen P Henckel B Saltin 《European journal of applied physiology and occupational physiology》1987,56(1):74-82
A random sample of schoolchildren, 119 boys and 153 girls, was tested in the fall of 1983. The data presented here are anthropometric data (height, weight, fat % and vital capacity) and oxygen uptake directly measured on a bicycle ergometer. The mean height and weight for boys were 179.1 cm and 67.7 kg, and those for girls were 168.0 cm and 59.6 kg. The mean fat content was 9.1% for boys and 19.1% for girls, and their mean vital capacities were 4.91 and 3.61 respectively. The boys had a high maximal oxygen uptake (51.7 ml X kg-1 X min-1) showing no reduction over the age span studied. The girls' maximal oxygen uptake was lower (overall mean 40.0 ml X kg-1 X min-1) with a small reduction from 16 to 19 years of age. When comparing maximal oxygen uptake per kg lean body mass in the two sexes, the boys had 18.4% higher values than the girls, indicating that girls of this age have the lower fitness level. The results of maximal aerobic power measurement in the boys compare well with findings from other investigations using direct measurements, indicating that the fitness of teenage boys is kept at a high level. Comparable data from various countries for girls show different pictures, but it appears that in general they have a low fitness level. 相似文献
242.
243.
244.
Gregory L. Dilworth 《Archives of biochemistry and biophysics》1982,219(1):30-38
The nicotinic acid hydroxylase from Clostridium barkeri is a selenoenzyme, as evidenced by the copurification of selenium with enzyme activity. This conclusion is supported by data showing a 23-fold increase in nicotinic acid hydroxylase activity when C. barkeri was cultured in media supplemented with selenium. A labile, selenium-containing compound was released from the native protein by treatment with either chaotropic agents and heat or by heating alone. A stable selenium compound was formed when the enzyme was alkylated prior to denaturation. This compound had the same chromatographic properties as dialykyl selenide in a number of systems. The formation of dialkyl selenide upon alkylation is not consistent with the selenium moiety being selenocysteine. Thus, nicotinic acid hydroxylase represents a new type of selenoenzyme. 相似文献
245.
Johan D.M. Olsson 《Carbohydrate research》2010,345(10):1331-1338
2-(N-Benzyloxycarbonyl)aminoethyl 7-O-acetyl-6-O-allyl-2-O-benzoyl-4-O-benzyl-3-O-chloroacetyl-l-glycero-α-d-manno-heptopyranosyl-(1→3)-[2,3,4,6-tetra-O-benzoyl-β-d-glucopyranosyl-(1→4)]-6,7-di-O-acetyl-2-O-benzyl-l-glycero-α-d-manno-heptopyranoside, a spacer-equipped protected derivative of the common 3,4-branched diheptoside trisaccharide structure of the lipopolysaccharide core of Neisseria meningitidis and Haemophilus influenzae has been synthesized. The protecting group pattern installed allows regioselective introduction of phosphoethanolamine residues in the 3- and 6-position of the second heptose unit in accordance with native structures. From this intermediate the 3-and 6-monophosphoethanolamine as well as the non-phosphorylated deprotected trisaccharides have been synthesized to be used in evaluation of antibody binding specificity and in investigation of the substrate specificity of glycosyl transferases involved in the biosynthesis of LPS core structures. 相似文献
246.
247.
248.
249.
M. Rhr 《Biometrical journal. Biometrische Zeitschrift》1985,27(1):89-95
Some points of CLIFF /KRUS 's important rotation procedure are criticized. This result in the definition of simple structure of canonical solutions, the use of STEWART /LOVE 's redundancy index as a measure of common variance, and two new rotation procedures (HAKSTIAN 's modified varimax rotation, separate rotation of both sets). The objects of rotation should be the (intraset) loadings. 相似文献
250.
Properties of purified colchicine-binding protein from a cultured carrot cell extract 总被引:1,自引:0,他引:1
Colchicine-binding protein (CBP) was purified from a cultured carrot cell extract by DEAE-Sephacel, phosphocellulose and Sephadex G200 column chromatographies. The purified CBP separated into three bands on SDS-polyacrylamide gel electrophoresis. One of them reacted with a monoclonal antibody against chick brain alpha-tubulin and the other two with that against beta-tubulin. Colchicine-binding activity of the purified protein was enhanced by tartrate and inhibited little by an excess of podophyllotoxin. It decayed following first order kinetics, but was more stable than the CBP in the crude extract. The binding constant of the purified CBP for colchicine was 0.57 microM-1 and the number of binding sites of colchicine per mg protein was about 2 nmol. This binding constant is about ten times lower than that of porcine brain tubulin under identical conditions. 相似文献