全文获取类型
收费全文 | 4684篇 |
免费 | 385篇 |
国内免费 | 1篇 |
专业分类
5070篇 |
出版年
2021年 | 39篇 |
2020年 | 27篇 |
2019年 | 51篇 |
2018年 | 70篇 |
2017年 | 44篇 |
2016年 | 53篇 |
2015年 | 118篇 |
2014年 | 141篇 |
2013年 | 236篇 |
2012年 | 232篇 |
2011年 | 233篇 |
2010年 | 159篇 |
2009年 | 120篇 |
2008年 | 232篇 |
2007年 | 242篇 |
2006年 | 239篇 |
2005年 | 234篇 |
2004年 | 215篇 |
2003年 | 238篇 |
2002年 | 191篇 |
2001年 | 167篇 |
2000年 | 215篇 |
1999年 | 164篇 |
1998年 | 70篇 |
1997年 | 60篇 |
1996年 | 61篇 |
1995年 | 53篇 |
1994年 | 57篇 |
1993年 | 33篇 |
1992年 | 113篇 |
1991年 | 92篇 |
1990年 | 95篇 |
1989年 | 86篇 |
1988年 | 68篇 |
1987年 | 50篇 |
1986年 | 57篇 |
1985年 | 38篇 |
1984年 | 56篇 |
1983年 | 36篇 |
1982年 | 24篇 |
1981年 | 20篇 |
1980年 | 31篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1975年 | 22篇 |
1974年 | 26篇 |
1973年 | 27篇 |
1972年 | 20篇 |
排序方式: 共有5070条查询结果,搜索用时 15 毫秒
51.
Canine and feline cardiac Z-lines and Z-rods were examined by electron microscopy before and after digestion of muscle fibers with Ca2+-activated protease (CAF). Removal by CAF of electron-dense material which covers Z-lines and Z-rods exposed interdigitating longitudinal filaments (6-7 nm in diameter) apparently continuous with thin filaments of the respective I-bands. The newly exposed longitudinal filaments of CAF-treated Z-lines and of CAF-treated Z-rods bound heavy meromyosin and therefore are actin. The width of Z-lines and length of Z-rods are determined by the amount of overlap of actin filaments of opposite polarity. The oblique filaments in Z-lines and Z-rods are responsible for the perpendicular periodicity of Z-lines and Z-rods, and are attributed to alpha-actinin. 相似文献
52.
Park Keun-Hyung; Fujisawa Sachiko; Sakurai Akira; Yamaguchi Isomaro; Takahashi Nobutaka 《Plant & cell physiology》1983,24(7):1241-1249
Endogenous gibberellins (GAs) in several kinds of crown gallcells and cultured cells derived from normal tissue of Nicotianatabacum were systematically analyzed by gas chromatography-selectedion current monitoring (GC-SICM) after chromatographic purifications,and GA1, GA9, GA19 and GA20 were identified. Agrobacterium tumefaciens,a pathogen of crown gall, was confirmed not to produce GAs inits culture. We also investigated endogenous GAs of mother plant,tobacco, and found the same kinds of GAs as in cultured cells.
3 Present address: College of Agriculture, Chonnam NationalUniversity, Kwangju 500, Korea. (Received May 19, 1982; Accepted July 22, 1983) 相似文献
53.
Measurement of turbulence intensity in the center of the canine ascending aorta with a hot-film anemometer 总被引:1,自引:0,他引:1
T Yamaguchi S Kikkawa T Yoshikawa K Tanishita M Sugawara 《Journal of biomechanical engineering》1983,105(2):177-187
The blood flow velocity near the central axis of the canine ascending aorta was measured with a hot-film anemometer. The cardiac output and the heart rate were controlled at will by means of an extracorporeal circulation and by atrial pacing. The turbulent component of the blood flow velocity was calculated using an ensemble average technique. Ensemble average turbulent intensity was also calculated to show the time course of turbulence in the aorta. The ratio of the mean turbulence intensity to the time mean sectional average velocity in the aorta was constant in most animals regardless of the changes in fluid mechanical parameters. The correlation between the frequency parameter and the relative mean turbulence intensity was weakly positive. The power spectrum of the turbulence was also calculated. 相似文献
54.
55.
56.
57.
Masashi Yamaguchi Theodore Yanos Tomoko Yamaguchi Abel Lajtha 《Developmental neurobiology》1969,1(4):419-433
When rat sciatic nerves were incubated with C14l-lysine, l- or d-glutamate, or d-l γ-aminoisobutyrate, the labeled compounds penetrated the nerve, and the level of lysine and leucine after 1 hr was higher in the nerve than in the medium. The level increased with time, and at 24 hr glutamate levels also were higher in the nerve than in the medium. Lowering the temperature strongly inhibited uptake, while other conditions such as absence of glucose, absence of sodium, or the presence of cyanide inhibited uptake by nerve less than uptake by brain slices. The uptake against a concentration gradient, and inhibitions of this uptake by metabolic inhibitors and by structural analogs, were interpreted as showing the presence of transport processes for amino acids in peripheral nerves with characteristics similar to such transport processes in the central nervous system. 相似文献
58.
59.