全文获取类型
收费全文 | 4165篇 |
免费 | 442篇 |
国内免费 | 2篇 |
专业分类
4609篇 |
出版年
2022年 | 34篇 |
2021年 | 77篇 |
2020年 | 51篇 |
2019年 | 63篇 |
2018年 | 74篇 |
2017年 | 61篇 |
2016年 | 113篇 |
2015年 | 160篇 |
2014年 | 172篇 |
2013年 | 231篇 |
2012年 | 267篇 |
2011年 | 233篇 |
2010年 | 176篇 |
2009年 | 156篇 |
2008年 | 204篇 |
2007年 | 212篇 |
2006年 | 178篇 |
2005年 | 164篇 |
2004年 | 151篇 |
2003年 | 135篇 |
2002年 | 146篇 |
2001年 | 90篇 |
2000年 | 92篇 |
1999年 | 79篇 |
1998年 | 55篇 |
1997年 | 40篇 |
1996年 | 32篇 |
1995年 | 29篇 |
1994年 | 27篇 |
1993年 | 32篇 |
1992年 | 49篇 |
1991年 | 47篇 |
1990年 | 47篇 |
1989年 | 56篇 |
1988年 | 44篇 |
1987年 | 39篇 |
1986年 | 46篇 |
1985年 | 37篇 |
1984年 | 27篇 |
1983年 | 31篇 |
1982年 | 29篇 |
1980年 | 30篇 |
1979年 | 34篇 |
1978年 | 34篇 |
1976年 | 26篇 |
1975年 | 30篇 |
1974年 | 38篇 |
1973年 | 31篇 |
1971年 | 27篇 |
1968年 | 26篇 |
排序方式: 共有4609条查询结果,搜索用时 15 毫秒
91.
Reduced atmospheric oxygen concentration is beneficial to embryo development; however, optimal oxygen concentration for oocyte maturation remains undetermined. Likewise, there is no consensus of appropriate medium supplementation during maturation. The objective of this study was to determine whether oxygen tension (20% or 5% O2) and epidermal growth factor (EGF) affect oocyte metabolism and subsequent embryo development. Cumulus-oocyte complexes (COCs) were collected from 28-day-old equine chorionic gonadotropin (eCG) primed or unprimed F1 (C57BL/6xCBA) mice. COCs were matured in defined medium in one of four groups: 20% O2, 20% O2 + EGF, 5% O2, 5% O2 + EGF. In vivo matured COCs were also collected for analysis. COCs from unprimed mice, matured in 5% O2 +/- EGF or 20% O2 + EGF had higher metabolic rates than COCs matured in 20% O2 (P < 0.05). COCs from primed mice had higher metabolic rates when matured in the presence of EGF, regardless of oxygen tension (P < 0.01). Oxygen uptake and mitochondrial membrane potential were higher for in vivo matured oocytes and oocytes matured under 5% O2 compared to oocytes matured under 20% O2 (P < 0.05). Blastocyst formation was not different between maturation groups (primed or unprimed); however, embryo cell numbers were 20-45% significantly higher when COCs were matured at 5% O2 (P < 0.05). Results suggest that oocytes matured in physiological concentrations of oxygen have improved development and metabolic activity, more closely resembling in vivo maturation. These findings have implications for oocyte maturation in both clinical and research laboratories. 相似文献
92.
Due to its inherent asymmetry, competition for light is thought to cause loss of diversity from eutrophied systems. However, most of the work on this topic in grasslands has been phenomenological and has not measured light directly. We present the results of one of the few mechanistic experiments investigating the outcome of short-term competition using measurements of light interception from monocultures of five perennial grass species grown under fertilized and irrigated conditions. We found that the level of incident light intercepted by each species in monoculture, a direct measure of resource-reduction ability, was an excellent predictor of the relative competitive effect in pairwise mixtures. Competition for light was asymmetric in relation to differences in light intercepting ability. Our results are consistent with the idea that when light is a limiting resource, competition between species for this resource can be asymmetric, contributing to high dominance and low diversity. 相似文献
93.
94.
Gardner RG Swarbrick GM Bays NW Cronin SR Wilhovsky S Seelig L Kim C Hampton RY 《The Journal of cell biology》2000,151(1):69-82
Endoplasmic reticulum (ER)-associated degradation (ERAD) is required for ubiquitin-mediated destruction of numerous proteins. ERAD occurs by processes on both sides of the ER membrane, including lumenal substrate scanning and cytosolic destruction by the proteasome. The ER resident membrane proteins Hrd1p and Hrd3p play central roles in ERAD. We show that these two proteins directly interact through the Hrd1p transmembrane domain, allowing Hrd1p stability by Hrd3p-dependent control of the Hrd1p RING-H2 domain activity. Rigorous reevaluation of Hrd1p topology demonstrated that the Hrd1p RING-H2 domain is located and functions in the cytosol. An engineered, completely lumenal, truncated version of Hrd3p functioned normally in both ERAD and Hrd1p stabilization, indicating that the lumenal domain of Hrd3p regulates the cytosolic Hrd1p RING-H2 domain by signaling through the Hrd1p transmembrane domain. Additionally, we identified a lumenal region of Hrd3p dispensable for regulation of Hrd1p stability, but absolutely required for normal ERAD. Our studies show that Hrd1p and Hrd3p form a stoichiometric complex with ERAD determinants in both the lumen and the cytosol. The HRD complex engages in lumen to cytosol communication required for regulation of Hrd1p stability and the coordination of ERAD events on both sides of the ER membrane. 相似文献
95.
Dumont Henri J. Han Bo-Ping Guo Fei Fei Chen Hua Cheng Dan Liu Ping Xu Lei Sanoamuang La-Orsri Rietzler Arnola C. Xu Shaolin Vierstraete Andy Elias-Gutierrez Manuel 《Aquatic Ecology》2021,55(4):1207-1222
Aquatic Ecology - Diaphanosoma s.l., with 40+? described species, is the largest genus of the Sididae and the Ctenopoda, similar in many ways to the anomopod genus Daphnia. Here, we offer a c... 相似文献
96.
97.
98.
99.
100.
Tom N Grammatopoulos Susan M Jones Ferogh A Ahmadi Brian R Hoover Lawrence D Snell Jesse Skoch Vimal V Jhaveri Andy M Poczobutt James A Weyhenmeyer W Michael Zawada 《Molecular neurodegeneration》2007,2(1):1-17