全文获取类型
收费全文 | 1229篇 |
免费 | 95篇 |
国内免费 | 1篇 |
出版年
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 33篇 |
2014年 | 49篇 |
2013年 | 62篇 |
2012年 | 75篇 |
2011年 | 97篇 |
2010年 | 44篇 |
2009年 | 54篇 |
2008年 | 55篇 |
2007年 | 69篇 |
2006年 | 63篇 |
2005年 | 59篇 |
2004年 | 48篇 |
2003年 | 65篇 |
2002年 | 54篇 |
2001年 | 17篇 |
2000年 | 19篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 17篇 |
1975年 | 14篇 |
1973年 | 11篇 |
1971年 | 7篇 |
排序方式: 共有1325条查询结果,搜索用时 468 毫秒
41.
Roland M Klar Raquel Duarte Therese Dix‐Peek Caroline Dickens Carlo Ferretti Ugo Ripamonti 《Journal of cellular and molecular medicine》2013,17(11):1444-1457
Coral-derived calcium carbonate/hydroxyapatite macroporous constructs of the genus Goniopora with limited hydrothermal conversion to hydroxyapatite (7% HA/CC) initiate the induction of bone formation. Which are the molecular signals that initiate pattern formation and the induction of bone formation? To evaluate the role of released calcium ions and osteoclastogenesis, 7% HA/CC was pre-loaded with either 500 μg of the calcium channel blocker, verapamil hydrochloride, or 240 μg of the osteoclast inhibitor, biphosphonate zoledronate, and implanted in the rectus abdominis muscle of six adult Chacma baboons Papio ursinus. Generated tissues on days 15, 60 and 90 were analysed by histomorphometry and qRT-PCR. On day 15, up-regulation of type IV collagen characterized all the implanted constructs correlating with vascular invasion. Zoledronate-treated specimens showed an important delay in tissue patterning and morphogenesis with limited bone formation. Osteoclastic inhibition yielded minimal, if any, bone formation by induction. 7% HA/CC pre-loaded with the Ca++ channel blocker verapamil hydrochloride strongly inhibited the induction of bone formation. Down-regulation of bone morphogenetic protein-2 (BMP-2) together with up-regulation of Noggin genes correlated with limited bone formation in 7% HA/CC pre-loaded with either verapamil or zoledronate, indicating that the induction of bone formation by coral-derived macroporous constructs is via the BMPs pathway. The spontaneous induction of bone formation is initiated by a local peak of Ca++ activating stem cell differentiation and the induction of bone formation. 相似文献
42.
Junling Ma P. van den Driessche Frederick H. Willeboordse 《Journal of mathematical biology》2013,66(1-2):75-94
An ordinary differential equation (ODE) epidemiological model for the spread of a disease that confers immunity, such as influenza, is introduced incorporating both network topology and households. Since most individuals of a susceptible population are members of a household, including the household structure as an aspect of the contact network in the population is of significant interest. Epidemic curves derived from the model are compared with those from stochastic simulations, and shown to be in excellent agreement. Expressions for disease threshold parameters of the ODE model are derived analytically and interpreted in terms of the household structure. It is shown that the inclusion of households can slow down or speed up the disease dynamics, depending on the variance of the inter-household degree distribution. This model illustrates how households (clusters) can affect disease dynamics in a complicated way. 相似文献
43.
44.
John M. Atack Yogitha N. Srikhanta Karrera Y. Djoko Jessica P. Welch Norain H. M. Hasri Christopher T. Steichen Rachel N. Vanden Hoven Sean M. Grimmond Dk Seti Maimonah Pg Othman Ulrike Kappler Michael A. Apicella Michael P. Jennings Jennifer L. Edwards Alastair G. McEwan 《Journal of bacteriology》2013,195(11):2632-2641
NtrYX is a sensor-histidine kinase/response regulator two-component system that has had limited characterization in a small number of Alphaproteobacteria. Phylogenetic analysis of the response regulator NtrX showed that this two-component system is extensively distributed across the bacterial domain, and it is present in a variety of Betaproteobacteria, including the human pathogen Neisseria gonorrhoeae. Microarray analysis revealed that the expression of several components of the respiratory chain was reduced in an N. gonorrhoeae
ntrX mutant compared to that in the isogenic wild-type (WT) strain 1291. These included the cytochrome c oxidase subunit (ccoP), nitrite reductase (aniA), and nitric oxide reductase (norB). Enzyme activity assays showed decreased cytochrome oxidase and nitrite reductase activities in the ntrX mutant, consistent with microarray data. N. gonorrhoeae
ntrX mutants had reduced capacity to survive inside primary cervical cells compared to the wild type, and although they retained the ability to form a biofilm, they exhibited reduced survival within the biofilm compared to wild-type cells, as indicated by LIVE/DEAD staining. Analyses of an ntrX mutant in a representative alphaproteobacterium, Rhodobacter capsulatus, showed that cytochrome oxidase activity was also reduced compared to that in the wild-type strain SB1003. Taken together, these data provide evidence that the NtrYX two-component system may be a key regulator in the expression of respiratory enzymes and, in particular, cytochrome c oxidase, across a wide range of proteobacteria, including a variety of bacterial pathogens. 相似文献
45.
46.
Marlene M. Hao Joel C. Bornstein Pieter Vanden Berghe Alan E. Lomax Heather M. Young Jaime P.P. Foong 《Developmental biology》2013
The enteric nervous system (ENS) is a vital part of the autonomic nervous system that regulates many gastrointestinal functions, including motility and secretion. All neurons and glia of the ENS arise from neural crest-derived cells that migrate into the gastrointestinal tract during embryonic development. It has been known for many years that a subpopulation of the enteric neural crest-derived cells expresses pan-neuronal markers at early stages of ENS development. Recent studies have demonstrated that some enteric neurons exhibit electrical activity from as early as E11.5 in the mouse, with further maturation of activity during embryonic and postnatal development. This article discusses the maturation of electrophysiological and morphological properties of enteric neurons, the formation of synapses and synaptic activity, and the influence of neural activity on ENS development. 相似文献
47.
Eva Matalova Herve Lesot Eva Svandova Tom Vanden Berghe Paul T. Sharpe Christopher Healy Peter Vandenabeele Abigail S. Tucker 《Development, growth & differentiation》2013,55(5):615-621
Apoptosis during tooth development appears dependent on the apoptotic executioner caspase‐3, but not caspase‐7. Instead, activated caspase‐7 has been found in differentiated odontoblasts and ameloblasts, where it does not correlate with apoptosis. To further investigate these findings, the mouse incisor was used as a model. Analysis of caspase‐7‐deficient mice revealed a significant thinner layer of hard tissue in the adult incisor. Micro computed tomography scan confirmed this decrease in mineralized tissues. These data strongly suggest that caspase‐7 might be directly involved in functional cell differentiation and regulation of the mineralization of dental matrices. 相似文献
48.
Thérèse Vanden Driessche Ghislaine M. Petiau-de Vries Jean-Luc Guisset 《Biological Rhythm Research》2013,44(4):349-360
We were able to demonstrate the presence of F 2,6-BP in Acetabularia in 7 out of 7 experiments. The amount varies between 4 and 38 pmole par mg protein. We were not able to evidence a circadian rhythm (CR) in its content. However, important fluctuations occur.(Fig. 1). This, of course excludes any precise conclusion about absolute amounts. Biologically active substances often exert an action modulated by circadian time. Thus, the effect of exogenous F 2,6-BP was assayed by fragmenting the long cell in F 2,6-BP-containing sea-water, and then follow growth and cap formation (we performed the experiment at different times during the 24 h cycle, in LD 12:12 conditions. Interestingly, the growth curves (obtained with 4 different concentrations) are statistically accelerated when the treatment had been performed at the beginning of the 24 h cycle (circadian time, CT, 0 is the transition time dark/light), less at CT 9.5, nul at CT 12 and again significant at CT 20. (Fig.IV). There is apparently no strictly defined light effect that could immediately modify the F-2,6-BP level, but there is presumably an important influence of CT-dependent physiological state of the alga. Again, it should be underlined that experimental biology should take time into account. 相似文献
49.
50.
David A. Alter Barry Franklin Dennis T. Ko Peter C. Austin Douglas S. Lee Paul I. Oh Therese A. Stukel Jack V. Tu 《PloS one》2013,8(6)