全文获取类型
收费全文 | 3544篇 |
免费 | 202篇 |
国内免费 | 1篇 |
出版年
2022年 | 20篇 |
2021年 | 44篇 |
2020年 | 23篇 |
2019年 | 24篇 |
2018年 | 38篇 |
2017年 | 38篇 |
2016年 | 61篇 |
2015年 | 134篇 |
2014年 | 150篇 |
2013年 | 231篇 |
2012年 | 208篇 |
2011年 | 209篇 |
2010年 | 139篇 |
2009年 | 151篇 |
2008年 | 200篇 |
2007年 | 198篇 |
2006年 | 240篇 |
2005年 | 216篇 |
2004年 | 237篇 |
2003年 | 194篇 |
2002年 | 186篇 |
2001年 | 59篇 |
2000年 | 54篇 |
1999年 | 67篇 |
1998年 | 41篇 |
1997年 | 39篇 |
1996年 | 24篇 |
1995年 | 28篇 |
1994年 | 24篇 |
1993年 | 24篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1976年 | 12篇 |
1973年 | 13篇 |
1971年 | 13篇 |
1969年 | 13篇 |
1968年 | 14篇 |
1966年 | 12篇 |
排序方式: 共有3747条查询结果,搜索用时 15 毫秒
81.
82.
Hideaki Yamada Toru Nagasawa Haruyuki Ohkishi Bunsei Kawakami Yoshiki Tani 《Biochemical and biophysical research communications》1981,100(3):1104-1110
Synthesis of D-cysteine from 3-chloro-D-alanine and hydrogen sulfide is catalyzed by highly purified 3-chloro-D-alanine hydrogen chloride-lyase from . The synthetic reaction proceeds optimally at pH 8.5, as a function of enzyme concentration and incubation time. The enzymatically synthesized D-cysteine was isolated from the large scale reaction mixture and identified by physicochemical means. 相似文献
83.
Cytochrome c oxidase from rat liver was incubated with various proteinases of different specificities and the enzymic activity was measured after various incubation times. A loss of catalytic activity was found after digestion with proteinase K, aminopeptidase M and a mitochondrial proteinase from rat liver. In each case the decrease in enzymic activity was compared with the changes in intensities of the polypeptide pattern obtained after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibilities of the subunit polypeptides of the soluble cytochrome c oxidase to proteinases were very different. Whereas subunit I was most susceptible, subunits V–VII were rather resistant to degradation. From the relative inaccessibility of subunits V–VII to proteinases it is likely that these polypeptides are buried in the interior of the enzyme complex. 相似文献
84.
Effects of an orally active angiotensin I-converting enzyme inhibitor, SQ 14225, on the actions of angiotensin I (AI) infused intravenously for 120 to 390 min were studied in 5 normal men. When 20 ng/kg/min of AI infusion was started immediately after a single oral administration of 100 mg of SQ 14225, a significant rise in blood pressure (BP) was observed for the first 15 min, but BP began to fall from 17 min and returned to the pretreatment level at 45 min. This BP level continued at least to 120 min and in one subject to 180 min. In this subject BP began to rise again from 185 min and reached the level of 15 min at 390 min. Plasma AI level increased gradually from 45 min. At 15 min plasma renin activity (PRA) decreased and plasma aldosterone (PA) increased, but then PRA began to increase and PA began to decrease. At 120 min the values of PRA and PA were similar to the pretreatment values. In one subject plasma AI and PRA began to decrease and PA began to increase after 120 or 180 min. On the other hand, in the 5 men sole AI infusion caused a continued BP rise, PRA decrease and PA increase, and sole SQ 14225 administration caused increases in plasma AI and PRA and a decrease in PA but no BP change. From these results it was concluded that complete blockade and partial inhibition of AI conversion by 100 mg of oral SQ 14225 lasted for about 2.5 and 6.5 hr, respectively and that BP rise, PRA suppression and aldosterone stimulation after AI infusion were entirely due to the actions of angiotensin II converted from AI. 相似文献
85.
86.
Circular dichroism (CD) and absorption spectra of squid (Todarodes pacificus) rhodopsin, isorhodopsin and the intermediates were measured at low temperatures. Squid rhodopsin has positive CD bands at wavelengths corresponding the - and β-absorption bands at liquid nitrogen temperature (CD maxima: 485 nm at -band and 348 nm at β-band) as well as at room temperature (CD maxima: 474 nm at -band and 347 nm at β-band). The rotational strength of the -band has a molecular ellipticity about twice that of cattle rhodopsin. The CD spectrum of bathorhodopsin displays a negative peak at 532 nm, the rotational strength of which has an absolute value slightly larger than that of rhodopsin. The reversal in sign at -band of the CD spectrum may indicate that the isomerization of retinal chromophore from twisted 11-cis form to twisted 11-trans form has occurred in the process of conversion from rhodopsin to bathorhodopsin. Lumirhodopsin has a small negative CD band at 490 nm, the maximum of which lies at 25 nm shorter wavelengths than the absorption maximum (515 nm), and a large positive CD band near 290 nm, which is not observed in rhodopsin and the other intermediates. This band may be derived from a conformational change of the opsin. In the process of changing from lumirhodopsin to LM-rhodopsin, the CD bands at visible and near ultraviolet regions disappear. Both alkaline and acid metarhodopsins have no CD bands at visible and near ultraviolet regions. 相似文献
87.
Activities of phosphatases in the aleurone layers of a husklessbarley, Ehime-hadaka No. 1, were enhanced in the absence ofgibberellic acid (GA3), while the enzyme secretion was absolutelydependent upon its presence. GA3 was required for both inductionand secretion of a-amylase. The longer the preincubation ofthe tissue without GA3, the longer was the lag period beforesecretion of both a group of phosphatases and a-amylase. Changesin the fine structure of aleurone cells were also investigated.Characteristics of the phase transition from enzyme accumulationto enzyme secretion seemed to be a development of a bundledtype of endoplasmic reticulum.
1Present address: Institute of Biological Sciences, The Universityof Tsukuba, Ibaraki 300-31, Japan. (Received August 25, 1975; ) 相似文献
88.
89.
M Kashiwazaki S Namioka K Mitani M Kono T Nakahara 《National Institute of Animal Health quarterly》1975,15(4):186-191
An effective and economical method was developed for procuring and rearing calves in gnotobiotic conditions. To evaluate apparatuses and surgical techniques, three calves, 1 to 3, welf 1 was weak and pale at delivery and died within 5 hours after delivery. Calf 2 was delivered alive, but died from a human error at 3 days of age. It was free from demonstrable bacteria and fungi at that time. Calf 3 was also successfully delivered and raised. It was killed at 10 days of age, since fungi were isolated from the feces and waste materials from it. 相似文献
90.