全文获取类型
收费全文 | 19950篇 |
免费 | 1832篇 |
国内免费 | 21篇 |
专业分类
21803篇 |
出版年
2022年 | 135篇 |
2021年 | 264篇 |
2020年 | 133篇 |
2019年 | 206篇 |
2018年 | 262篇 |
2017年 | 206篇 |
2016年 | 380篇 |
2015年 | 672篇 |
2014年 | 744篇 |
2013年 | 925篇 |
2012年 | 1205篇 |
2011年 | 1270篇 |
2010年 | 768篇 |
2009年 | 669篇 |
2008年 | 965篇 |
2007年 | 1074篇 |
2006年 | 991篇 |
2005年 | 980篇 |
2004年 | 970篇 |
2003年 | 945篇 |
2002年 | 920篇 |
2001年 | 213篇 |
2000年 | 146篇 |
1999年 | 211篇 |
1998年 | 265篇 |
1997年 | 190篇 |
1996年 | 172篇 |
1995年 | 204篇 |
1994年 | 182篇 |
1993年 | 168篇 |
1992年 | 170篇 |
1991年 | 147篇 |
1990年 | 138篇 |
1989年 | 130篇 |
1988年 | 139篇 |
1987年 | 138篇 |
1986年 | 138篇 |
1985年 | 159篇 |
1984年 | 180篇 |
1983年 | 151篇 |
1982年 | 216篇 |
1981年 | 224篇 |
1980年 | 223篇 |
1979年 | 143篇 |
1978年 | 149篇 |
1977年 | 134篇 |
1976年 | 164篇 |
1975年 | 123篇 |
1974年 | 137篇 |
1973年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
Jamie A. G. Hamilton Miyoung Y. Lee Rae Hunter Raira S. Ank Jamie Y. Story Ganesh Talekar Talia Sisroe Dov B. Ballak Andrew Fedanov Christopher C. Porter Elan Z. Eisenmesser Charles A. Dinarello Sunil S. Raikar James DeGregori Curtis J. Henry 《Aging cell》2021,20(2)
Aging‐associated declines in innate and adaptive immune responses are well documented and pose a risk for the growing aging population, which is predicted to comprise greater than 40 percent of the world''s population by 2050. Efforts have been made to improve immunity in aged populations; however, safe and effective protocols to accomplish this goal have not been universally established. Aging‐associated chronic inflammation is postulated to compromise immunity in aged mice and humans. Interleukin‐37 (IL‐37) is a potent anti‐inflammatory cytokine, and we present data demonstrating that IL‐37 gene expression levels in human monocytes significantly decline with age. Furthermore, we demonstrate that transgenic expression of interleukin‐37 (IL‐37) in aged mice reduces or prevents aging‐associated chronic inflammation, splenomegaly, and accumulation of myeloid cells (macrophages and dendritic cells) in the bone marrow and spleen. Additionally, we show that IL‐37 expression decreases the surface expression of programmed cell death protein 1 (PD‐1) and augments cytokine production from aged T‐cells. Improved T‐cell function coincided with a youthful restoration of Pdcd1, Lat, and Stat4 gene expression levels in CD4+ T‐cells and Lat in CD8+ T‐cells when aged mice were treated with recombinant IL‐37 (rIL‐37) but not control immunoglobin (Control Ig). Importantly, IL‐37‐mediated rejuvenation of aged endogenous T‐cells was also observed in aged chimeric antigen receptor (CAR) T‐cells, where improved function significantly extended the survival of mice transplanted with leukemia cells. Collectively, these data demonstrate the potency of IL‐37 in boosting the function of aged T‐cells and highlight its therapeutic potential to overcome aging‐associated immunosenescence. 相似文献
172.
173.
Rouhana L Wang L Buter N Kwak JE Schiltz CA Gonzalez T Kelley AE Landry CF Wickens M 《RNA (New York, N.Y.)》2005,11(7):1117-1130
Cytoplasmic polyadenylation is important in the control of mRNA stability and translation, and for early animal development and synaptic plasticity. Here, we focus on vertebrate poly(A) polymerases that are members of the recently described GLD2 family. We identify and characterize two closely related GLD2 proteins in Xenopus oocytes, and show that they possess PAP activity in vivo and in vitro and that they bind known polyadenylation factors and mRNAs known to receive poly(A) during development. We propose that at least two distinct polyadenylation complexes exist in Xenopus oocytes, one of which contains GLD2; the other, maskin and Pumilio. GLD2 protein interacts with the polyadenylation factor, CPEB, in a conserved manner. mRNAs that encode GLD2 in mammals are expressed in many tissues. In the brain, mouse, and human GLD2 mRNAs are abundant in anatomical regions necessary for long-term cognitive and emotional learning. In the hippocampus, mouse GLD2 mRNA colocalizes with CPEB1 and Pumilio1 mRNAs, both of which are likely involved in synaptic plasticity. We suggest that mammalian GLD2 poly(A) polymerases are important in synaptic translation, and in polyadenylation throughout the soma. 相似文献
174.
175.
Mark P. Peterson Kimberly A. Rosvall Jeong-Hyeon Choi Charles Ziegenfus Haixu Tang John K. Colbourne Ellen D. Ketterson 《PloS one》2013,8(4)
Despite sharing much of their genomes, males and females are often highly dimorphic, reflecting at least in part the resolution of sexual conflict in response to sexually antagonistic selection. Sexual dimorphism arises owing to sex differences in gene expression, and steroid hormones are often invoked as a proximate cause of sexual dimorphism. Experimental elevation of androgens can modify behavior, physiology, and gene expression, but knowledge of the role of hormones remains incomplete, including how the sexes differ in gene expression in response to hormones. We addressed these questions in a bird species with a long history of behavioral endocrinological and ecological study, the dark-eyed junco (Junco hyemalis), using a custom microarray. Focusing on two brain regions involved in sexually dimorphic behavior and regulation of hormone secretion, we identified 651 genes that differed in expression by sex in medial amygdala and 611 in hypothalamus. Additionally, we treated individuals of each sex with testosterone implants and identified many genes that may be related to previously identified phenotypic effects of testosterone treatment. Some of these genes relate to previously identified effects of testosterone-treatment and suggest that the multiple effects of testosterone may be mediated by modifying the expression of a small number of genes. Notably, testosterone-treatment tended to alter expression of different genes in each sex: only 4 of the 527 genes identified as significant in one sex or the other were significantly differentially expressed in both sexes. Hormonally regulated gene expression is a key mechanism underlying sexual dimorphism, and our study identifies specific genes that may mediate some of these processes. 相似文献
176.
As the public debate in Europe about genetically modified (GM) crops heats up and the trade row between the United States and the European Union over GM food escalates, what better time to examine the issues with an international group of experts (Box 1). Their views are diverse, but they all agree that we need more impartial communication, less propaganda and an effective regulatory regime that is based on a careful case-by-case consideration of GM technology. It seems that GM crops are here to stay, so let us hope that these requirements are met and that the developing nations that perhaps have the most to gain from this technology can start to reap its benefits. 相似文献
177.
Rodriguez D Ramesh C Henson LH Wilmeth L Bryant BK Kadavakollu S Hirsch R Montoya J Howell PR George JM Alexander D Johnson DL Arterburn JB Shuster CB 《Bioorganic & medicinal chemistry》2011,19(18):5446-5453
Assembly of a bipolar mitotic spindle requires the action of class 5 kinesins, and inhibition or depletion of this motor results in mitotic arrest and apoptosis. S-Trityl-l-cysteine is an allosteric inhibitor of vertebrate Kinesin Spindle Protein (KSP) that has generated considerable interest due to its anti-cancer properties, however, poor pharmacological properties have limited the use of this compound. We have modified the triphenylmethyl and cysteine groups, guided by biochemical and cell-based assays, to yield new cysteinol and cysteamine derivatives with increased inhibitory activity, greater efficacy in model systems, and significantly enhanced potency against the NCI60 tumor panel. These results reveal a promising new class of conformationally-flexible small molecules as allosteric KSP inhibitors for use as research tools, with activities that provide impetus for further development as anti-tumor agents. 相似文献
178.
179.
180.