全文获取类型
收费全文 | 12489篇 |
免费 | 945篇 |
国内免费 | 1篇 |
出版年
2023年 | 53篇 |
2021年 | 89篇 |
2020年 | 93篇 |
2019年 | 92篇 |
2018年 | 225篇 |
2017年 | 272篇 |
2016年 | 313篇 |
2015年 | 387篇 |
2014年 | 451篇 |
2013年 | 637篇 |
2012年 | 992篇 |
2011年 | 1020篇 |
2010年 | 534篇 |
2009年 | 368篇 |
2008年 | 787篇 |
2007年 | 823篇 |
2006年 | 727篇 |
2005年 | 639篇 |
2004年 | 590篇 |
2003年 | 614篇 |
2002年 | 571篇 |
2001年 | 324篇 |
2000年 | 348篇 |
1999年 | 188篇 |
1998年 | 107篇 |
1997年 | 87篇 |
1996年 | 97篇 |
1995年 | 93篇 |
1994年 | 99篇 |
1993年 | 88篇 |
1992年 | 95篇 |
1991年 | 95篇 |
1990年 | 99篇 |
1989年 | 83篇 |
1988年 | 81篇 |
1987年 | 78篇 |
1986年 | 81篇 |
1985年 | 85篇 |
1984年 | 84篇 |
1983年 | 84篇 |
1982年 | 72篇 |
1981年 | 78篇 |
1980年 | 76篇 |
1979年 | 70篇 |
1978年 | 67篇 |
1977年 | 65篇 |
1976年 | 48篇 |
1974年 | 41篇 |
1973年 | 57篇 |
1971年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Ingemar Björkhem Hans Jörnvall Eila Zeppezauer 《Biochemical and biophysical research communications》1973,52(2):413-420
Recrystallized alcohol dehydrogenase from horse liver was found to oxidize 17-hydroxystearic acid into 17-oxostearic acid, the 17-L-enantiomer faster than the 17-D-enantiomer. Alone at high pH or in combination with aldehyde dehydrogenase, the alcohol dehydrogenase also catalyzed conversion of 18-hydroxystearic acid into 1, 18-octadecadioic acid and 5β-cholestane-3α,7α,12α,26-tetrol into 3α,7α,12α-trihydroxy-5β-cholestanoic acid. All the activities as well as the ethanol dehydrogenase activity disappeared after specific carboxymethylation of a single cystein residue at the active site of alcohol dehydrogenase. These results conclusively show that alcohol dehydrogenase itself has ω-hydroxyfatty acid dehydrogenase activity and ω-hydroxysteroid dehydrogenase activity. 相似文献
112.
Björn Sandström 《Histochemistry and cell biology》1970,24(4):281-286
Summary A new histochemically demonstrable thiaminepyrophosphatase activity in liver tissue is described. It appears to be localized solely to the cytosomes of the sinusoidal endothelium. The activity, which requires high concentration of lead ion for its demonstration, has a high degree of substrate specificity. It resists formaldehyde fixation, ethanol and many inhibitors. The optimum pH is at pH 6.This study was supported in part by a grant from the Swedish Medical Research Council. 相似文献
113.
Summary Histochemically demonstrable Golgi-associated TDP-ase activity in liver cells from cat, chicken, rat and frog has been investigated.This activity is highly substrate-specific, insensitive to aldehyde fixation, ethanol, acetate, lead and most enzyme inhibitors. It is stimulated by divalent manganese, calcium, magnesium and cobalt and optimum pH is at pH 6 to 7.The characteristics are identical for all four species but significant differences exist at a comparison with bile canalicular activity, Golgi-associated activity in other cells and biochemical findings.This study was supported in part by a grant from the Swedish Medical Research Council. 相似文献
114.
Serum activities of aspartate aminotransferase (AspAT = GOT), alanine aminotransferase (AlAT = GPT), and total lactate dehydrogenase (LDH) have been investigated in newborn calves, pigs, and lambs. In the two latter species the LDH isoenzyme distribution in serum was also studied. Blood samples were taken at frequent intervals from birth to 48–72 hrs. post partum. Calves and pigs were born with very low serum enzyme values, whereas lambs showed a picture more similar to what has been reported in human infants. In all species a marked temporary enzyme increase occurred during the first 24–48 hrs. This elevation was found not to be due to colostrum feeding, since a parallel increase was found in starved animals. Possible regulating mechanisms are discussed. The LDH isoenzyme pattern proved to be more stable than total LDH in the early post-natal period. The percentage isoenzyme distribution, however, showed characteristic differences from that found in adult animals of the same species. 相似文献
115.
Summary The isolation, morphology and growth chracteristics of pure cultures of a Thiothece, Lamprocystis and Thiodictyon strain are described.Their carotenoid composition is reported. The Thiothece strain produced in addition to okenone (1), several related ketocarotenoids, among which a demethylated okenone (6) was identified by a small scale total synthesis. Thiodictyon and Lamprocystis produced carotenoids of the rhodopinal (previously warmingone) series, the latter organism contained as major carotenoids a lycopenol (4), not previously found in Nature, and a cross-conjugated lycopenal (2), previously called anhydro-warmingone.Part 7. Acta chem. scand. 21, 2185 (1967). 相似文献
116.
117.
Subcellular fractionation of human liver 总被引:1,自引:0,他引:1
118.
119.
Else Nøst Hegseth 《Polar Biology》1989,9(8):479-486
Summary Photoadaptation in some marine Arctic diatoms has been studied. Thalassiosira antarctica, Nitzschia delicatissima and Chaetoceros furcellatus were grown at-0.5°C and various irradiances and continuous light. Growth and cellular chlorophyll were followed during transitional phase after the algae had been transferred from one irradiance to another. Adaptation time for cellular chlorophyll was linearly related to the gradient in irradiance, and adaptation to transfer from high to low light was faster than from low to high light. Adaptation time was found to be species dependent, and Arctic diatoms growing at low temperature seemed to adapt as fast as temperate species.Contribution No. 243 from Trondhjem Biological Station 相似文献
120.
Summary Plasminogen activator inhibitor type-1 (PAI-1) was identified in extracts of rat adrenal medulla, and its immunohistochemical localization was studied together with that of tissue-type plasminogen activator (t-PA). By staining of adjacent sections and by doublestaining of the same section we demonstrate that the same cells of the adrenal medulla contain both PAI-1 and t-PA immunoreactivity in the cytoplasm. In addition a few ganglion cells of the adrenal medulla were found to contain PAI-1 but not t-PA. Neither of the components were found in the adrenal cortex. Analysis of extracts from isolated adrenal medulla using reverse zymography showed the presence of a plasminogen activator inhibitor with M
r46000. The inhibitory activity disappeared when the extract was passed through a column with sepharose-coupled anti-PAI-1 IgG, while the run-through from a similar column coupled with preimmune IgG still contained the inhibitor. The present findings suggest that PAI-1 could play a role in the regulation of t-PA activity in the rat adrenal gland medullary cells. 相似文献