全文获取类型
收费全文 | 2058篇 |
免费 | 83篇 |
国内免费 | 1篇 |
出版年
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 43篇 |
2014年 | 32篇 |
2013年 | 174篇 |
2012年 | 81篇 |
2011年 | 100篇 |
2010年 | 78篇 |
2009年 | 61篇 |
2008年 | 110篇 |
2007年 | 119篇 |
2006年 | 96篇 |
2005年 | 123篇 |
2004年 | 153篇 |
2003年 | 152篇 |
2002年 | 113篇 |
2001年 | 36篇 |
2000年 | 34篇 |
1999年 | 36篇 |
1998年 | 37篇 |
1997年 | 22篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 23篇 |
1993年 | 18篇 |
1992年 | 22篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 31篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1981年 | 27篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1974年 | 7篇 |
1973年 | 10篇 |
1971年 | 8篇 |
排序方式: 共有2142条查询结果,搜索用时 24 毫秒
1.
2.
Hiroyuki Kozu Isao Kobayashi Mitsutoshi Nakajima Kunihiko Uemura Seigo Sato Sosaku Ichikawa 《Food biophysics》2010,5(4):330-336
This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis.
We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric
walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function
defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity
of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly
affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to
gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately
20 s−1 in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass
transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The
visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric
walls with an intragastric fluid. 相似文献
3.
Free radical mechanisms in enzyme reactions 总被引:1,自引:0,他引:1
Isao Yamazaki 《Free radical biology & medicine》1987,3(6):397-404
Free radicals are formed in prosthetic groups or amino acid residues of certain enzymes. These free radicals are closely related to the activation process in enzyme catalysis, but their formation does not always result in the formation of substrate free radicals as a product of the enzyme reactions. The role of free radicals in enzyme catalysis is discussed. 相似文献
4.
Whole cells of Chlorella vulgaris and Clostridium butyricum were co-immobilized in 2% agar gel. NADP was suitable as an electron carrier. The rate of hydrogen evolution increased with increasing NADP concentration. The optimum conditions for hydrogen evolution were pH 7.0 and 37°C. The immobilized C. vulgaris-NADP-immobilized Cl. butyricum system continuously evolved hydrogen at a rate of 0.29–1.34 μmol/h per mg Chl for 6 days. On the other hand, the system without NADP evolved only a trace amount of hydrogen. 相似文献
5.
6.
Silvia Pastorekova Daniela Vullo Angela Casini Andrea Scozzafava Jaromir Pastorek Isao Nishimori 《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):211-217
The tumor-associated transmembrane carbonic anhydrase (CA, EC 4.2.1.1) isozymes IX (CA IX) and XII (CA XII) are involved in acidification of hypoxic tumors, a process correlated with poor prognosis and clinical outcome of patients harboring such tumors. This process may be reversed by inhibiting these enzymes with potent sulfonamide/sulfamate inhibitors. A series of such aromatic/heterocyclic sulfonamides incorporating 2,3,5,6-tetrafluorobenzoyl-, 2,3,5,6-tetrafluoro- phenylsulfonyl- and pentafluorophenylureido moieties has been investigated for its interaction with the catalytic domain of the human isozymes hCA IX and hCA XII. Some of these compounds showed excellent inhibitory properties against both isozymes IX and XII, with several subnanomolar inhibitors detected for the first time. These sulfonamides may constitute valuable candidates for the development of novel antitumor therapies based on the inhibition of such tumor-associated CA isozymes. 相似文献
7.
Four kinds of active sites of bacterial fatty acid synthetase were mapped on distinct regions within a subunit. Active sites were specifically labeled with radioactive substrates and active-site-directed inhibitors. Labeled enzymes were cleaved with proteases, and the fragments thus produced were identified with respect to specific labels by SDS-polyacrylamide gel electrophoresis and a fluorographic technique. The linear alignment of such fragments in the original subunit was established and when the results were combined with those of our previous work, five active sites were located in three regions as follows. Starting from the N-terminal of the subunit, we located acetyl, malonyl and palmitoyl transferases in the first region, the acyl carrier site in the second region (Morishima & Ikai (1985) Biochim. Biophys. Acta 832, 297-307), and beta-ketoacyl synthetase in the third region. The observed order of active sites of bacterial fatty acid synthetase can be correlated with that of the yeast enzyme, which has two kinds of subunits. 相似文献
8.
T Matuura M Kohno Y Kanayama K Yasunari K Murakawa T Takeda K Ishimori I Morishima T Yonezawa 《Biochemical and biophysical research communications》1987,143(3):1012-1017
Using 31p-NMR (the phosphorus nuclear magnetic resonance) spectroscopy, we measured intracellular free Mg levels in the erythrocytes of untreated (n = 7) and diltiazem-treated spontaneously hypertensive rats (SHR) (n = 8), and compared them with age-matched Wistar-Kyoto rats (WKY) (n = 10). The intracellular free Mg levels were significantly (p less than 0.01) decreased in untreated SHR compared with those in control WKY. A successful antihypertensive treatment with diltiazem increased the intracellular free Mg levels compared with untreated SHR (p less than 0.05). Furthermore, an inverse correlation was observed between intracellular free Mg levels and blood pressure levels in all groups (r = -0.48, p less than 0.01, n = 25). These observations suggest that abnormalities of intracellular Mg metabolism may be, in part, related to the development or the maintenance of hypertension in SHR. 相似文献
9.
Diurnal Rhythm and Characteristics of Photosynthesis and Respiration in the Leaf and Root of a Phalaenopsis Plant 总被引:1,自引:0,他引:1
A hybrid Phalaenopsis plant was grown hydroponically on a nutrientsolution of Hyponex in the greenhouse. Typical daily patternsof CO2 fixation, production of malic acid and citric acid andpH of the leaf and root were determined. The rate of primaryfixation of CO2 in the leaf increased markedly in the evening,remained high until well into the afternoon, then decreasedsharply. The pattern of production of organic acids resultedfrom the fact that the rate of uptake of CO2 gas was highestat night and fell during the day. A high correlation betweenpH value and level of malic acid in the leaves was observed,and an exponential relationship appeared to exist between theseparameters. These rhythmic sequences were not observed in theroot. The results suggest that metabolism in the leaf had characteristicsof CAM (Crassulacean Acid Metabolism), while the root did not. (Received May 6, 1988; Accepted October 25, 1988) 相似文献