全文获取类型
收费全文 | 176127篇 |
免费 | 7833篇 |
国内免费 | 848篇 |
出版年
2022年 | 630篇 |
2021年 | 1548篇 |
2020年 | 879篇 |
2019年 | 1109篇 |
2018年 | 12988篇 |
2017年 | 11667篇 |
2016年 | 9380篇 |
2015年 | 4189篇 |
2014年 | 4317篇 |
2013年 | 5087篇 |
2012年 | 10649篇 |
2011年 | 18905篇 |
2010年 | 15797篇 |
2009年 | 11789篇 |
2008年 | 14863篇 |
2007年 | 16386篇 |
2006年 | 5462篇 |
2005年 | 5517篇 |
2004年 | 5818篇 |
2003年 | 5643篇 |
2002年 | 5140篇 |
2001年 | 1103篇 |
2000年 | 776篇 |
1999年 | 983篇 |
1998年 | 1237篇 |
1997年 | 843篇 |
1996年 | 752篇 |
1995年 | 653篇 |
1994年 | 622篇 |
1993年 | 693篇 |
1992年 | 573篇 |
1991年 | 557篇 |
1990年 | 469篇 |
1989年 | 407篇 |
1988年 | 439篇 |
1987年 | 355篇 |
1986年 | 317篇 |
1985年 | 399篇 |
1984年 | 525篇 |
1983年 | 419篇 |
1982年 | 503篇 |
1981年 | 486篇 |
1980年 | 415篇 |
1979年 | 295篇 |
1978年 | 324篇 |
1977年 | 282篇 |
1976年 | 263篇 |
1974年 | 241篇 |
1972年 | 360篇 |
1971年 | 375篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
141.
142.
143.
Cathrine Laustrup M?ller Rasmus Kj?bsted Pablo J. Enriori Thomas Elbenhardt Jensen Cecilia Garcia-Rudaz Sara A. Litwak Kirsten Raun J?rgen Wojtaszewski Birgitte Schjellerup Wulff Michael A. Cowley 《PloS one》2016,11(7)
The melanocortin system includes five G-protein coupled receptors (family A) defined as MC1R-MC5R, which are stimulated by endogenous agonists derived from proopiomelanocortin (POMC). The melanocortin system has been intensely studied for its central actions in body weight and energy expenditure regulation, which are mainly mediated by MC4R. The pituitary gland is the source of various POMC-derived hormones released to the circulation, which raises the possibility that there may be actions of the melanocortins on peripheral energy homeostasis. In this study, we examined the molecular signaling pathway involved in α-MSH-stimulated glucose uptake in differentiated L6 myotubes and mouse muscle explants. In order to examine the involvement of AMPK, we investigate α-MSH stimulation in both wild type and AMPK deficient mice. We found that α-MSH significantly induces phosphorylation of TBC1 domain (TBC1D) family member 1 (S237 and T596), which is independent of upstream PKA and AMPK. We find no evidence to support that α-MSH-stimulated glucose uptake involves TBC1D4 phosphorylation (T642 and S704) or GLUT4 translocation. 相似文献
144.
Michael W. Shiflett Kristy L. Gould Tom V. Smulders Timothy J. DeVoogd 《Developmental neurobiology》2002,51(3):215-222
The hippocampal formation (HF) of food‐storing birds is larger than non‐storing species, and the size of the HF in food‐storing Black‐Capped Chickadees (Poecile atricapillus) varies seasonally. We examined whether the volume of the septum, a medial forebrain structure that shares reciprocal connections with the HF, demonstrates the same species and seasonal variation as has been shown in the HF. We compared septum volume in three parid species; non‐storing Blue Tits (Parus caeruleus) and Great Tits (Parus major), and food‐storing Black‐Capped Chickadees. We found the relative septum volume to be larger in chickadees than in the non‐storing species. We also compared septum and nucleus of the diagonal band (NDB) volume of Black‐Capped Chickadees at different times of the year. We found that the relative septum volume varies seasonally in food‐storing birds. The volume of the NDB does not vary seasonally. Due to the observed species and seasonal variation, the septum, like the hippocampal formation of food‐storing birds, may be specialized for some aspects of food‐storing and spatial memory. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 215–222, 2002 相似文献
145.
146.
Mingyue Wang Pranab K Mukherjee Jyotsna Chandra Ali Abdul Lattif Thomas S McCormick Mahmoud A Ghannoum 《BMC microbiology》2008,8(1):31
Background
We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed. 相似文献147.
Dana M. Bergstrom George R. Stewart Patricia M. Selkirk Susanne Schmidt 《Oecologia》2002,130(2):309-314
'15N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '15N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '15N signatures of peat layers. At two sites 15N-enriched peat '15N signatures of up to +17 were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '15N. Less 15N enriched '15N signatures (e.g. -1.9 to +3.9) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that 15N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology. 相似文献
148.
149.
150.