全文获取类型
收费全文 | 1660篇 |
免费 | 155篇 |
专业分类
1815篇 |
出版年
2022年 | 8篇 |
2021年 | 26篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 20篇 |
2016年 | 42篇 |
2015年 | 60篇 |
2014年 | 69篇 |
2013年 | 78篇 |
2012年 | 107篇 |
2011年 | 112篇 |
2010年 | 78篇 |
2009年 | 58篇 |
2008年 | 101篇 |
2007年 | 102篇 |
2006年 | 78篇 |
2005年 | 89篇 |
2004年 | 94篇 |
2003年 | 92篇 |
2002年 | 95篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 23篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 17篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 6篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 13篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1971年 | 7篇 |
排序方式: 共有1815条查询结果,搜索用时 0 毫秒
91.
Transglutaminase 2 (TG2) is the most widely distributed member of the transglutaminase family with almost all cell types in the body expressing TG2 to varying extents. In addition to being widely expressed, TG2 is an extremely versatile protein exhibiting transamidating, protein disulphide isomerase and guanine and adenine nucleotide binding and hydrolyzing activities. TG2 can also act as a protein scaffold or linker. This unique protein also undergoes extreme conformational changes and exhibits localization diversity. Being mainly a cytosolic protein; it is also found in the nucleus, associated with the cell membrane (inner and outer side) and with the mitochondria, and also in the extracellular matrix. These different activities, conformations and localization need to be carefully considered while assessing the role of TG2 in physiological and pathological processes. For example, it is becoming evident that the role of TG2 in cell death processes is dependent upon the cell type, stimuli, subcellular localization and conformational state of the protein. In this review we discuss in depth the conformational and functional diversity of TG2 in the context of its role in numerous cellular processes. In particular, we have highlighted how differential localization, conformation and activities of TG2 may distinctly mediate cell death processes. 相似文献
92.
Yu W Hegarty JP Berg A Chen X West G Kelly AA Wang Y Poritz LS Koltun WA Lin Z 《PloS one》2011,6(5):e20454
BACKGROUND: NKX2-3 is associated with inflammatory bowel disease (IBD). NKX2-3 is expressed in microvascular endothelial cells and the muscularis mucosa of the gastrointestinal tract. Human intestinal microvascular endothelial cells (HIMECs) are actively involved in the pathogenesis of IBD and IBD-associated microvascular dysfunction. To understand the cellular function of NKX2-3 and its potential role underlying IBD pathogenesis, we investigated the genes regulated by NKX2-3 in HIMEC using cDNA microarray. METHODOLOGY/PRINCIPAL FINDINGS: NKX2-3 expression was suppressed by shRNA in two HIMEC lines and gene expression was profiled by cDNA microarray. Pathway Analysis was used to identify gene networks according to biological functions and associated pathways. Validation of microarray and genes expression in intestinal tissues was assessed by RT-PCR. NKX2-3 regulated genes are involved in immune and inflammatory response, cell proliferation and growth, metabolic process, and angiogenesis. Several inflammation and angiogenesis related signaling pathways that play important roles in IBD were regulated by NKX2-3, including endothelin-1 and VEGF-PI3K/AKT-eNOS. Expression levels of NKX2-3, VEGFA, PI3K, AKT, and eNOS are increased in intestinal tissues from IBD patients and expression levels of EDN1 are decreased in intestinal tissues from IBD patients. These results demonstrated the important roles of NKX2-3, VEGF, PI3K, AKT, eNOS, and EDN1 in IBD pathogenesis. Correlation analysis showed a positive correlation between mRNA expression of NKX2-3 and VEGFA and a negative correlation between mRNA expression of NKX2-3 and EDN1 in intestinal tissues from IBD patients. CONCLUSION/RELEVANCE: NKX2-3 may play an important role in IBD pathogenesis by regulating endothelin-1 and VEGF signaling in HIMECs. 相似文献
93.
Bunyamwera bunyavirus RNA synthesis requires cooperation of 3'- and 5'-terminal sequences 总被引:1,自引:0,他引:1 下载免费PDF全文
Bunyamwera virus (BUNV) is the prototype of both the Orthobunyavirus genus and the Bunyaviridae family of segmented negative-sense RNA viruses. The tripartite BUNV genome consists of small (S), medium (M), and large (L) segments that are each transcribed to yield a single mRNA and are replicated to generate an antigenome that acts as a template for synthesis of further genomic strands. As for all negative-sense RNA viruses, the 3'- and 5'-terminal nontranslated regions (NTRs) of the BUNV S, M, and L segments exhibit nucleotide complementarity and, except for one conserved U-G pairing, this complementarity extends for 15, 18, and 19 nucleotides, respectively. We investigated whether the complementarity of 3' and 5' NTRs reflected a functional requirement for terminal cooperation to promote BUNV RNA synthesis or, alternatively, was a consequence of genomic and antigenomic NTRs having similar functions requiring sequence conservation. We show that cooperation between 3'- and 5'-NTR sequences is required for BUNV RNA synthesis, and our results suggest that this cooperation is due to nucleotide complementarity allowing 3' and 5' NTRs to associate through base-pairing interactions. To examine the importance of complementarity in promoting BUNV RNA synthesis, we utilized a competitive replication assay able to examine the replication ability of all possible combinations of interacting nucleotides within a defined region of BUNV 3' and 5' NTRs. We show here that maximal RNA replication was signaled when sequences exhibiting perfect complementarity within 3' and 5' NTRs were selected. 相似文献
94.
95.
Hueffer K Holcomb D Ballweber LR Gende SM Blundell G O'Hara TM 《Journal of wildlife diseases》2011,47(4):984-988
The harbor seal population in Glacier Bay National Park, Alaska, has declined by over 70% since 1992. The reasons for this decline are not known. We examined serum antibodies and feces for evidence of exposure to multiple pathogens in this population. We also studied harbor seals from a reference site on Kodiak Island. In 2007, we found antibodies against Leptospira spp. in 31% of specimens from harbor seals in Glacier Bay, but no detectable serum antibodies in samples from Kodiak. In 2008, no samples had detectable antibodies against Leptospira spp. No serum antibodies against Toxoplasma gondii, morbilliviruses, or presence of Cryptosporidium in fecal samples were detected. However, Giardia was found in 6% of the fecal samples from Glacier Bay. Our results indicate that the harbor seal population in Glacier Bay National Park could be immunologically na?ve to distemper viruses and therefore vulnerable to these pathogens. Given the relatively low prevalence of antibodies and low titers, pathogens likely are not the reason for the harbor seal decline in Glacier Bay. 相似文献
96.
We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF. 相似文献
97.
98.
99.
Beta‐diversity metrics of the upper digestive tract microbiome are associated with body mass index 下载免费PDF全文
100.