全文获取类型
收费全文 | 8098篇 |
免费 | 1152篇 |
国内免费 | 5篇 |
出版年
2023年 | 34篇 |
2022年 | 83篇 |
2021年 | 174篇 |
2020年 | 101篇 |
2019年 | 131篇 |
2018年 | 180篇 |
2017年 | 135篇 |
2016年 | 251篇 |
2015年 | 366篇 |
2014年 | 418篇 |
2013年 | 477篇 |
2012年 | 626篇 |
2011年 | 620篇 |
2010年 | 370篇 |
2009年 | 316篇 |
2008年 | 436篇 |
2007年 | 457篇 |
2006年 | 480篇 |
2005年 | 401篇 |
2004年 | 437篇 |
2003年 | 358篇 |
2002年 | 377篇 |
2001年 | 198篇 |
2000年 | 124篇 |
1999年 | 113篇 |
1998年 | 85篇 |
1997年 | 72篇 |
1996年 | 60篇 |
1995年 | 56篇 |
1994年 | 52篇 |
1993年 | 40篇 |
1992年 | 72篇 |
1991年 | 71篇 |
1990年 | 65篇 |
1989年 | 52篇 |
1988年 | 57篇 |
1987年 | 59篇 |
1986年 | 71篇 |
1985年 | 62篇 |
1984年 | 49篇 |
1983年 | 39篇 |
1981年 | 41篇 |
1980年 | 33篇 |
1979年 | 55篇 |
1977年 | 32篇 |
1975年 | 34篇 |
1974年 | 37篇 |
1973年 | 37篇 |
1972年 | 34篇 |
1971年 | 40篇 |
排序方式: 共有9255条查询结果,搜索用时 93 毫秒
1.
2.
3.
Plasma concentrations of adrenaline and noradrenaline were measured at rest from cannulated fish and following net capture. Adrenaline and noradrenaline concentrations in capture-stressed fish averaged 36,740 pmol l-1 and 38,860 pmol l-1 respectively, whereas resting values were less than 200 pmol l-1 for both amines. Erythrocyte swelling and raised blood lactate were evident in stressed fish. In vitro effects of 5 mmol l-1 adrenaline on erythrocyte suspensions suggested that the catecholamine had a direct effect on erythrocyte volume. The significance of these results is discussed in relation to the oxygen transport properties of the blood. 相似文献
4.
5.
6.
7.
8.
Tim Schwarting Philipp Lechler Johannes Struewer Marius Ambrock Thomas Manfred Frangen Steffen Ruchholtz Ewgeni Ziring Michael Frink 《PloS one》2015,10(2)
IntroductionSuccessful graft ingrowth following reconstruction of the anterior cruciate ligament is governed by complex biological processes at the tendon-bone interface. The aim of this study was to investigate in an in vitro study the effects of bone morphogenetic protein 7 (BMP-7) on tendon-bone integration.ResultsIn both models, positive effects of BMP-7 on ALP enzyme activity were observed (p<0.001). Additionally, similar results were noted for LDH activity and lactate concentration. BMP-7 stimulation led to a significant increase in OCN expression. Whereas the effects of BMP-7 on tendon monoculture peaked during an early phase of the experiment (p<0.001), the cocultures showed a maximal increase during the later stages (p<0.001). The histological analysis showed a stimulating effect of BMP-7 on extracellular matrix formation. Organized ossification zones and calcium carbonate-like structures were only observed in the BMP-stimulated cell cultures.DiscussionThis study showed the positive effects of BMP-7 on the biological process of tendon-bone integration in vitro. Histological signs of improved mineralization were paralleled by increased rates of osteoblast-specific protein levels in primary bovine osteoblasts and fibroblasts.ConclusionOur findings indicated a role for BMP-7 as an adjuvant therapeutic agent in the treatment of ligamentous injuries, and they emphasized the importance of the transdifferentiation process of tendinous fibroblasts at the tendon-bone interface. 相似文献
9.
10.
Summary The carbon cycle of a loblolly pine plantation in North Carolina was examined during its 12th through 16th years from planting. Net primary production during the study period averaged 2056 g C m-2 year-1. With autotrophic respiration equal to 2068 g C, the calculated gross production was 4124 g C m-2 year-1. Heterotrophic respiration of 694 g C m-2 year-1 resulted in net ecosystem production of 1362 g C m-2 year-1. In carbon cycle comparisons between forest ecosystems, autotrophic respiration rates were found to be closely coupled to regional temperature. 相似文献