全文获取类型
收费全文 | 10566篇 |
免费 | 730篇 |
专业分类
11296篇 |
出版年
2021年 | 102篇 |
2020年 | 60篇 |
2019年 | 72篇 |
2018年 | 140篇 |
2017年 | 95篇 |
2016年 | 159篇 |
2015年 | 226篇 |
2014年 | 320篇 |
2013年 | 553篇 |
2012年 | 493篇 |
2011年 | 539篇 |
2010年 | 296篇 |
2009年 | 304篇 |
2008年 | 523篇 |
2007年 | 517篇 |
2006年 | 481篇 |
2005年 | 492篇 |
2004年 | 527篇 |
2003年 | 466篇 |
2002年 | 474篇 |
2001年 | 368篇 |
2000年 | 375篇 |
1999年 | 306篇 |
1998年 | 157篇 |
1997年 | 115篇 |
1996年 | 115篇 |
1995年 | 123篇 |
1994年 | 92篇 |
1993年 | 76篇 |
1992年 | 233篇 |
1991年 | 242篇 |
1990年 | 209篇 |
1989年 | 208篇 |
1988年 | 163篇 |
1987年 | 150篇 |
1986年 | 127篇 |
1985年 | 135篇 |
1984年 | 116篇 |
1983年 | 118篇 |
1982年 | 106篇 |
1981年 | 83篇 |
1980年 | 61篇 |
1979年 | 84篇 |
1978年 | 84篇 |
1977年 | 62篇 |
1976年 | 72篇 |
1975年 | 58篇 |
1973年 | 64篇 |
1972年 | 43篇 |
1971年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
S Masumura M Hashimoto Y Hashimoto T Sato I Kihara Y Watanabe 《European journal of applied physiology and occupational physiology》1982,48(2):157-161
Activities of glycolytic enzymes in the aorta were investigated in female Wistar rats. There were two groups of rats; one served as the control (sedentary rats), while the other group was forced to run on a treadmill for 10 weeks. In the control animals, the activities of hexokinase, phosphofructokinase and aldolase were relatively lower than those of the other glycolytic enzymes (phosphoglucose isomerase, lactate dehydrogenase and pyruvate kinase). After exercise, the activity of phosphofructokinase increased by 15%, whereas the other enzymatic activities were much the same as in the controls. Within the limits of the experiments, the increased percentage of phosphofructokinase was statistically significant (p less than 0.05). Since phosphofructokinase is a putative rate limiting enzyme, this enzymatic activation may indicate that glycolytic activity in the rat aorta is enhanced during and after running exercise. 相似文献
12.
K Watanabe Y Fujii H Ohkubo S Kuramitsu H Kagamiyama S Nakanishi O Hayaishi 《Biochemical and biophysical research communications》1991,181(1):272-278
The full-length bovine lung prostaglandin(PG) F synthase cDNA was constructed from partial cDNA clones and ligated into bacterial expression vector pUC8 to develop expression plasmid pUCPF1. This plasmid permitted the synthesis of bovine lung PGF synthase in Escherichia coli. The recombinant bacteria overproduced a 36-KDa protein that was recognized by anti-PGF synthase antibody, and the expressed protein was purified to apparent homogeneity. The expressed protein reduced not only carbonyl compounds including PGD2 and phenanthrenequinone but also PGH2; and the Km values for phenanthrenequinone, PGD2, and PGH2 of the expressed protein were 0.1, 100, and 8 microM, respectively, which are the same as those of the bovine lung PGF synthase. The protein produced PGF2 alpha from PGH2, and 9 alpha, 11 beta-PGF2 from PGD2 at different active sites. Moreover, the structure of the purified protein from Escherichia coli was essentially identical to that of the native enzyme in terms of C-terminal sequence, sulfhydryl groups, and CD spectra except that the nine amino acids provided by the lac Z' gene of the vector were fused to the N-terminus. These results indicate that the expressed protein is essentially identical to bovine lung PGF synthase. We confirmed that PGF synthase is a dual function enzyme catalyzing the reduction of PGH2 and PGD2 on a single enzyme and that it has one binding site for NADPH. 相似文献
13.
14.
Between birth and 10 days of age, the volume density (volume/unit cytoplasmic volume) of the matrix, and the surface density (area/unit cytoplasmic volume) of the inner membrane and cristae increased in both periportal and perihepatic hepatocytes, and did not differ significantly between the cells of the two zones. After 10 days of age, however, the volume density of the matrix decreased in perihepatic cells and remained unchanged in periportal cells, and, therefore, it became greater in periportal cells than in perihepatic cells in 20-day-old and adult animals. The surface density of the inner membrane and cristae decreased in the cells of both zones. Further, the hepatocyte volume increased markedly, especially in perihepatic zones between 20 days of age and the adult. The results show that, in postnatally differentiating hepatocytes, mitochondria are likely to develop during early postnatal period, then the structural heterogeneity of mitochondria arises, and hepatocyte volume increases markedly during late postnatal period after weaning. Thus, the process of postnatal hepatocyte differentiation includes such several phases of development. 相似文献
15.
When pregnant mice were fed biotin-deficient diets, cleft palate occurred more frequently in male fetuses than in female fetuses. Possible underlying mechanisms are speculated on, and some methodological problems in the analysis of sex-related differences in multiparous animals are discussed. 相似文献
16.
Reiko Yu-Ito Kazuko Ôba Ikuzo Uritani 《Bioscience, biotechnology, and biochemistry》2013,77(8):2087-2091
In addition to HMG-CoA reductase, another HMG-CoA utilizing enzyme is present in the Mt fraction of sweet potato root tissue and its activity interferes with the assay to HMG-CoA reductase activity. 相似文献
17.
W Kuchinke O Barski K Watanabe O Hayaishi 《Biochemical and biophysical research communications》1992,183(3):1238-1246
Using the cDNA of bovine lung prostaglandin F synthase (EC 1.1.1.2) as a probe, we isolated a clone from a bovine liver cDNA library which differed in only eleven nucleotides from the probe. The corresponding protein contained three amino acid substitutions, including a leucine residue which is conserved throughout all aldo-keto reductases. We inserted the liver cDNA into expression vector pUC19 and expressed the recombinant liver enzyme in E.coli. The purified liver enzyme reduced prostaglandin H2 as well as prostaglandin D2 and various carbonyl compounds. The high relative activity against prostaglandin H2 in combination with a high Km value for prostaglandin D2 identified this liver enzyme as a lung type prostaglandin F synthase. However, the binding constant for NADPH of the liver enzyme was 3.5 fold higher than that of lung prostaglandin F synthase. 相似文献
18.
Hidekatsu Yokoyama Shin-ichi Niwa Kenji Itoh Reiko Mazuka 《Biological cybernetics》1996,75(2):137-140
On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects
(n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and
difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was
found in normal controls.
Received: 21 July 1995/Accepted in revised form: 30 April 1996 相似文献
19.
20.