全文获取类型
收费全文 | 212篇 |
免费 | 8篇 |
专业分类
系统科学 | 9篇 |
理论与方法论 | 4篇 |
现状及发展 | 92篇 |
研究方法 | 16篇 |
综合类 | 73篇 |
自然研究 | 26篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 4篇 |
2012年 | 11篇 |
2011年 | 21篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 11篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1965年 | 5篇 |
1963年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 78 毫秒
51.
We provide the 1st documented accounts of the Mexican endemic rattlesnake Crotalus aquilus from the state of México. The new records extend the known distribution of the species into a region where it may be sympatric with the superficially similar C. triseriatus . Because these taxa have previously been subject to some taxonomic confusion, we performed a preliminary morphological comparison using individuals of both species obtained from proximal localities. Our analyses support the supposition that these taxa are morphologically distinct. The new localities for C. aquilus are situated in high valleys that have been extensively modified by human settlement and agriculture. 相似文献
52.
João Nicolau 《Journal of forecasting》2011,30(8):706-720
We propose a new nonparametric density forecast based on time‐ and state‐domain smoothing. We analyze some of its asymptotic properties and provide an empirical illustration. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
53.
54.
55.
Pauline Ferraris Elodie Beaumont Rustem Uzbekov Denys Brand Julien Gaillard Emmanuelle Blanchard Philippe Roingeard 《Cellular and molecular life sciences : CMLS》2013,70(7):1297-1306
Like most positive-strand RNA viruses, hepatitis C virus (HCV) forms a membrane-associated replication complex consisting of replicating RNA, viral and host proteins anchored to altered cell membranes. We used a combination of qualitative and quantitative electron microscopy (EM), immuno-EM, and the 3D reconstruction of serial EM sections to analyze the host cell membrane alterations induced by HCV. Three different types of membrane alteration were observed: vesicles in clusters (ViCs), contiguous vesicles (CVs), and double-membrane vesicles (DMVs). The main ultrastructural change observed early in infection was the formation of a network of CVs surrounding the lipid droplets. Later stages in the infectious cycle were characterized by a large increase in the number of DMVs, which may be derived from the CVs. These DMVs are thought to constitute the membranous structures harboring the viral replication complexes in which viral replication is firmly and permanently established and to protect the virus against double-stranded RNA-triggered host antiviral responses. 相似文献
56.
Frazão C McVey CE Amblar M Barbas A Vonrhein C Arraiano CM Carrondo MA 《Nature》2006,443(7107):110-114
RNA degradation is a determining factor in the control of gene expression. The maturation, turnover and quality control of RNA is performed by many different classes of ribonucleases. Ribonuclease II (RNase II) is a major exoribonuclease that intervenes in all of these fundamental processes; it can act independently or as a component of the exosome, an essential RNA-degrading multiprotein complex. RNase II-like enzymes are found in all three kingdoms of life, but there are no structural data for any of the proteins of this family. Here we report the X-ray crystallographic structures of both the ligand-free (at 2.44 A resolution) and RNA-bound (at 2.74 A resolution) forms of Escherichia coli RNase II. In contrast to sequence predictions, the structures show that RNase II is organized into four domains: two cold-shock domains, one RNB catalytic domain, which has an unprecedented alphabeta-fold, and one S1 domain. The enzyme establishes contacts with RNA in two distinct regions, the 'anchor' and the 'catalytic' regions, which act synergistically to provide catalysis. The active site is buried within the RNB catalytic domain, in a pocket formed by four conserved sequence motifs. The structure shows that the catalytic pocket is only accessible to single-stranded RNA, and explains the specificity for RNA versus DNA cleavage. It also explains the dynamic mechanism of RNA degradation by providing the structural basis for RNA translocation and enzyme processivity. We propose a reaction mechanism for exonucleolytic RNA degradation involving key conserved residues. Our three-dimensional model corroborates all existing biochemical data for RNase II, and elucidates the general basis for RNA degradation. Moreover, it reveals important structural features that can be extrapolated to other members of this family. 相似文献
57.
Eriogallococcus isaias Hodgson and Magalhães is a Neotropical species of gall-inducing scale insect (Coccoidea: Eriococcidae), whose phenological synchrony with its host plant, Pseudobombax grandiflorum, is fundamental to the maintenance of its population. Furthermore, E. isaias is unusual among gall-inducing Eriococcidae because its galls are not sexually dimorphic and are induced by the second-instar nymphs. We studied the life cycles of the host plant and the galling insect, and followed the development of the insects and the structure of the gall. The results showed that gall induction is synchronous with leaf flushing, and that the galls and leaves mature concomitantly. Males have a 36–48-day life cycle within the gall, whereas females have a 75–100-day life cycle. 相似文献
58.
59.
A. G. Del Río 《Cellular and molecular life sciences : CMLS》1979,35(2):185-186
Summary
Bufo arenarum spermatozoa were able to sustain motility both under aerobic and anaerobic conditions. In aerobiosis, the oxygen consumption varies between 2.6 and 4.2 l O2/108 cells/h at 30°C. The synthesis of lactic acid by anaerobic spermatozoa demonstrated the existence of an active glycolytic pathway.This work was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas and the Latinoamerican Program of Human Reproduction (PLAMIRH), grant 34-95-2-75. 相似文献
60.
Sara Canato João D. Santos Ana S. Carvalho Kerman Aloria Margarida D. Amaral Rune Matthiesen André O. Falcao Carlos M. Farinha 《Cellular and molecular life sciences : CMLS》2018,75(24):4495-4509
Misfolded F508del-CFTR, the main molecular cause of the recessive disorder cystic fibrosis, is recognized by the endoplasmic reticulum (ER) quality control (ERQC) resulting in its retention and early degradation. The ERQC mechanisms rely mainly on molecular chaperones and on sorting motifs, whose presence and exposure determine CFTR retention or exit through the secretory pathway. Arginine-framed tripeptides (AFTs) are ER retention motifs shown to modulate CFTR retention. However, the interactions and regulatory pathways involved in this process are still largely unknown. Here, we used proteomic interaction profiling and global bioinformatic analysis to identify factors that interact differentially with F508del-CFTR and F508del-CFTR without AFTs (F508del-4RK-CFTR) as putative regulators of this specific ERQC checkpoint. Using LC–MS/MS, we identified kinesin family member C1 (KIFC1) as a stronger interactor with F508del-CFTR versus F508del-4RK-CFTR. We further validated this interaction showing that decreasing KIFC1 levels or activity stabilizes the immature form of F508del-CFTR by reducing its degradation. We conclude that the current approach is able to identify novel putative therapeutic targets that can be ultimately used to the benefit of CF patients. 相似文献