全文获取类型
收费全文 | 11107篇 |
免费 | 715篇 |
国内免费 | 2篇 |
出版年
2023年 | 73篇 |
2021年 | 129篇 |
2020年 | 116篇 |
2019年 | 137篇 |
2018年 | 229篇 |
2017年 | 243篇 |
2016年 | 338篇 |
2015年 | 437篇 |
2014年 | 474篇 |
2013年 | 688篇 |
2012年 | 797篇 |
2011年 | 764篇 |
2010年 | 473篇 |
2009年 | 400篇 |
2008年 | 613篇 |
2007年 | 564篇 |
2006年 | 559篇 |
2005年 | 486篇 |
2004年 | 484篇 |
2003年 | 433篇 |
2002年 | 409篇 |
2001年 | 215篇 |
2000年 | 163篇 |
1999年 | 148篇 |
1998年 | 90篇 |
1997年 | 82篇 |
1996年 | 70篇 |
1995年 | 72篇 |
1994年 | 56篇 |
1993年 | 59篇 |
1992年 | 103篇 |
1991年 | 77篇 |
1990年 | 91篇 |
1989年 | 107篇 |
1988年 | 88篇 |
1987年 | 64篇 |
1986年 | 82篇 |
1985年 | 98篇 |
1983年 | 64篇 |
1982年 | 53篇 |
1981年 | 55篇 |
1979年 | 87篇 |
1978年 | 57篇 |
1974年 | 82篇 |
1973年 | 77篇 |
1972年 | 52篇 |
1970年 | 69篇 |
1969年 | 63篇 |
1968年 | 59篇 |
1967年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
191.
Monique Bedin Dominique Weil Thérèse Fournier Lise Cedard Jean Frezal 《Human genetics》1981,59(3):256-258
Summary Steroid sulfatase activities are significantly higher in placentas obtained after the birth of girls than after the birth of boys, and also in female fibroblasts compared to male strains. This constitutes biochemical evidence for the non-inactivation of the X-linked sulfatase locus. No hydrolytic activity is found in the fibroblasts of ichthyotic boys. Heterozygosity is demonstrated in the fibroblasts of the four mothers studied, as they have steroid sulfatase activity of less or equivalent to the normal male value. 相似文献
192.
Summary Specific detection of iota-Carrageenan (i-CAR) at the ultrastructural level has been obtained by coupling with ruthenium red (RR) — an electron microscopic stain. The i-CAR-RR complex showed electron density on carbon layers. Peritoneal macrophages were treated with the complex and after 3 h it caused the same morphological changes in macrophages as iota-Carrageenan alone. On the surfaces of macrophages, fine filamentous electron dense material — the i-CAR-RR complex — was detected. 相似文献
193.
Neonatal transplantation tolerance to the products of theH-2
b
complex was induced in B10.A (H-2
a
) mice. On the basis of the survival of skin allografts it was found that antigens determined by theD region of theH-2
b
complex (of the B10.A(2R) strain) were most easily overcome and that tolerance to the products of theD end of theH-2 complex (of the B10.A(4R) strain) was also easy to induce. The antigens produced by theK end ofH-2 (of the B10.A(5R) and B10.A(3R) strains) represented a stronger incompatibility barrier and a difference in the entireH-2
b
complex caused strongest resistance to tolerance induction. When tolerance to the products of the entireH-2
b
complex was induced in newborn B10.A mice, and the neonatally treated animals were grafted simultaneously with five different grafts, those disparate at theK end ofH-2 and in the entireH-2 region were rejected in some animals, while the grafts disparate at theD end of H-2 remained intact in the same mice. No dependence on theI-J subregion was observed in this system. Furthermore, tolerance was more easily inducible in male than in female B10.A mice. 相似文献
194.
Perfused rat hearts were treated with isoprenaline (10?6M) or ouabain (5.5 × 10?6M). The phosphate contents of troponin-I and myosin P light chains were established by radiolabelling with 32P; in the case of the light chains, direct chemical analysis of total and of specifically alkali-labile phosphate was also performed. Addition of isoprenaline caused phosphorylation of both troponin-I and myosin P light chains, reaching a maximum increment, after several minutes, of 1 mol/mol and 0.30 mol/mol, respectively. The Mg2+-ATPase activities, at saturating Ca2+ concentrations, of natural actomyosin isolated from treated hearts were significantly depressed, and an inverse correlation was established between the phosphate content of troponin-I and the Vmax[Ca2+] of this ATPase activity. The Ca2+ sensitivity of the was also decreased. These changes were all reversed by an incubation permitting dephosphorylation of proteins by endogenous phosphatases.Treatment of hearts with ouabain caused no increment in troponin-I phosphorylation, but increased the P light chain phosphate content to a maximum of 0.30 mol/mol after some minutes. A positive correlation was evident between phosphate content of the light chains (in all experiments) and the maximum myosin Ca2+-ATPase activities. In addition, the Vmax[ATP] of the of natural actomyosin was increased when light chain phosphorylation had occurred in the absence of troponin-I phosphorylation. P-light chain phosphorylation did not affect the Ca2+ sensitivity of activity.We suggest that the effects of phosphorylation of troponin-I are to diminish thin filament sensitivity to Ca2+, and to decrease the efficiency of the transduction process along neighbouring actin monomers, such that the number of actin-myosin crossbridge interactions is decreased even in the presence of Ca2+ excess. Phosphorylation of P light chains of myosin has an activating effect on myosin Ca2+-ATPase activity, as well as on the rate of cross-bridge formation. 相似文献
195.
Calmodulin stimulated 45Ca2+ uptake into a plasma membrane enriched fraction from ox neurohypophysial nerve endings and into a microsome fraction. The 45Ca2+ uptake and the (Ca2+-Mg2+) ATPase activity in the plasma membrane fraction exhibited similar pCa and calmodulin sensitivities, suggesting that the enzyme activity is the biochemical expression of a high affinity Ca2+ pump. Calmodulin thus seems to play a role in regulation of the intracellular free Ca2+ concentration in the neurohypophysis. 相似文献
196.
Dr. Thorvald Sætersdal Hogne Engedal Jakob Røli Harald Jodalen Svein Rotevatn 《Cell and tissue research》1981,215(1):13-19
Summary Calcium (Ca) and Magnesium (Mg) are determined by atomic absorption flame spectrometry in isolated cardiac mitochondria from mice receiving subcutaneous injections of DL-isoproterenol HC1 (ISO), and in mitochondria of untreated controls. In the controls, mitochondria were isolated in the presence or absence of ruthenium red. On the absence of ruthenium red in the isolation medium, mitochondrial Ca levels increase by about 300%, while levels of Mg remain unchanged. Focal myocardial necrosis following a single ISO-injection is shown by electron microscopy. Ca and Mg levels are largely unaffected by a single dose of ISO until 24 h after the injection. A slight increase in Ca occurs in the 48 h samples. When multiple injections of ISO are given every 12th hour for 48 h, 72 h and 96 h, respectively, endogenous Ca and Mg increase significantly. It is suggested that this increase might be associated with ISO-induced cardiac hypertrophy rather than with the pharmacological effects of ISO per se.This work was supported by grants from The Norwegian Council on Cardiovascular Disease and from The Norwegian Research Council for Science and the Humanities 相似文献
197.
198.
199.
200.
Nielsen Johannes Vetner Max Holm Vagn Askjær Svend Aage Reske-Nielsen Edith 《Human genetics》1977,38(3):357-362
Summary A case of Meckel or Gruber syndrome is reported, together with a survey of the relevant literature of recent years (1971–1977), in reference to a probably autosomal recessive inheritance of this malformation. 相似文献