全文获取类型
收费全文 | 4506篇 |
免费 | 347篇 |
专业分类
4853篇 |
出版年
2023年 | 23篇 |
2022年 | 32篇 |
2021年 | 65篇 |
2020年 | 48篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 62篇 |
2016年 | 110篇 |
2015年 | 198篇 |
2014年 | 234篇 |
2013年 | 224篇 |
2012年 | 327篇 |
2011年 | 311篇 |
2010年 | 240篇 |
2009年 | 187篇 |
2008年 | 274篇 |
2007年 | 243篇 |
2006年 | 243篇 |
2005年 | 225篇 |
2004年 | 228篇 |
2003年 | 212篇 |
2002年 | 230篇 |
2001年 | 41篇 |
2000年 | 31篇 |
1999年 | 58篇 |
1998年 | 60篇 |
1997年 | 46篇 |
1996年 | 51篇 |
1995年 | 41篇 |
1994年 | 37篇 |
1993年 | 52篇 |
1992年 | 36篇 |
1991年 | 40篇 |
1990年 | 26篇 |
1989年 | 48篇 |
1988年 | 33篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 21篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1974年 | 20篇 |
1973年 | 17篇 |
1970年 | 14篇 |
排序方式: 共有4853条查询结果,搜索用时 15 毫秒
1.
2.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献3.
Regeneration of Triticum aestivum apical explants after microinjection of germ line progenitor cells with DNA 总被引:2,自引:0,他引:2
A highly efficient method of regenerating fertile, phenotypically normal plants from shoot apex cultures of T. aestivum was developed. The hypodermal layer (L2) of the vegetative apex containing germ line precursor cells could be located with bright field microscopy and targeted for microinjection. Fluorescently labelled dextrans were used as markers to develop a microinjection procedure which did not disrupt nuclear or cytoplasmic structure. This procedure was used to inject plasmid DNA into L2 cells. Capillary microinjection did not shear the plasmid DNA and delivery of DNA was confirmed by polymerase chain reaction analysis of DNA isolated from injected apices. The significance of these findings in relation to the development of cereal transformation systems will be discussed. 相似文献
4.
Daniel A. Vardy Csaba Kari Gerald S. Lazarus Pamela J. Jensen Asher Zilberstein Gregory D. Plowman Ulrich Rodeck 《Journal of cellular physiology》1995,163(2):257-265
Autocrine activation of the epidermal growth factor (EGF) receptor on keratinocytes has been recognized as an important growth regulatory mechanism involved in epithelial homeostasis, and, possibly, hyperproliferative diseases. Insulin-like growth factor (IGF)-1 and insulin have been shown to be paracrine keratinocyte mitogens that bind to the type I IGF receptor which is expressed on actively proliferating keratinocytes in situ. In this report, we demonstrate that IGF-1/insulin induced production of keratinocyte-derived autocrine growth factors that bind to the EGF receptor. Increased steady-state mRNA levels for transforming growth factor alpha (TGF-α) and for amphiregulin (AR) were observed upon incubation of keratinocytes with mitogenic concentrations of IGF-1. IGF-1 also induced production and secretion of TGF-α and AR proteins as detected by immunoassays. An EGF receptor antagonistic monoclonal antibody abolished the mitogenic effect of IGF-1 on cultured keratinocytes. These results suggest that stimulation of keratinocyte growth by IGF-1 requires activation of an EGF receptor-mediated autocrine loop. © 1995 Wiley-Liss, Inc. 相似文献
5.
During 1975--77 Hemophilus vaginalis bacteremia occurred post partum in eight previously healthy women. Seven had been admitted for delivery at term and one because of threatened abortion. Six underwent cesarean section. Post-partum pyrexia and neutrophilia were the main features. All the patients recovered uneventfully while receiving antibiotics. H. vaginalis is an infrequent agent of bacteremia; it affects predominantly women after obstetric trauma. 相似文献
6.
7.
8.
Abstract: Schwannoma-derived growth factor (SDGF) is a potent mitogen and neuronal differentiation factor. Because of its relationship to epidermal growth factor (EGF) and the heregulins, it was asked if SDGF interacts with the EGF receptor or HER2/neu. SDGF binds to and causes the phosphorylation on tyrosine of the EGF receptor but not HER2/neu. 相似文献
9.
T Groves 《BMJ (Clinical research ed.)》1990,300(6732):1128-1130
10.
The cold-shock response — a hot topic 总被引:4,自引:2,他引:2