全文获取类型
收费全文 | 2365篇 |
免费 | 192篇 |
国内免费 | 2篇 |
出版年
2023年 | 10篇 |
2022年 | 14篇 |
2021年 | 53篇 |
2020年 | 32篇 |
2019年 | 49篇 |
2018年 | 48篇 |
2017年 | 45篇 |
2016年 | 77篇 |
2015年 | 107篇 |
2014年 | 123篇 |
2013年 | 162篇 |
2012年 | 198篇 |
2011年 | 166篇 |
2010年 | 127篇 |
2009年 | 108篇 |
2008年 | 126篇 |
2007年 | 128篇 |
2006年 | 122篇 |
2005年 | 113篇 |
2004年 | 104篇 |
2003年 | 85篇 |
2002年 | 98篇 |
2001年 | 33篇 |
2000年 | 34篇 |
1999年 | 30篇 |
1998年 | 17篇 |
1997年 | 18篇 |
1996年 | 16篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 18篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 10篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1970年 | 6篇 |
1967年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有2559条查询结果,搜索用时 15 毫秒
111.
112.
In the present study, we examined the effects of four kinds of cysteine protease inhibitors (E64, E64d, leupeptin, and ALLN) on the in vitro asexual growth of Babesia bovis. Of these, only the lipophilic inhibitors, E64d and ALLN, were found to effectively inhibit the growth of B. bovis. In further experiments, E64d, but not ALLN, significantly suppressed the parasite’s invasion of host erythrocytes, while both chemicals, especially ALLN, inhibited the parasite’s replication within the infected erythrocytes. These data suggested the presence of cysteine protease(s) derived from B. bovis, in which the protease(s) would play important roles in the erythrocyte invasion and/or replication processes of the parasite. 相似文献
113.
Tom N Grammatopoulos Susan M Jones Ferogh A Ahmadi Brian R Hoover Lawrence D Snell Jesse Skoch Vimal V Jhaveri Andy M Poczobutt James A Weyhenmeyer W Michael Zawada 《Molecular neurodegeneration》2007,2(1):1-17
Background
Recent attention has focused on understanding the role of the brain-renin-angiotensin-system (RAS) in stroke and neurodegenerative diseases. Direct evidence of a role for the brain-RAS in Parkinson's disease (PD) comes from studies demonstrating the neuroprotective effect of RAS inhibitors in several neurotoxin based PD models. In this study, we show that an antagonist of the angiotensin II (Ang II) type 1 (AT1) receptor, losartan, protects dopaminergic (DA) neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity both in primary ventral mesencephalic (VM) cultures as well as in the substantia nigra pars compacta (SNpc) of C57BL/6 mice (Fig. 1).Results
In the presence of exogenous Ang II, losartan reduced MPP+ (5 μM) induced DA neuronal loss by 72% in vitro. Mice challenged with MPTP showed a 62% reduction in the number of DA neurons in the SNpc and a 71% decrease in tyrosine hydroxylase (TH) immunostaining of the striatum, whereas daily treatment with losartan lessened MPTP-induced loss of DA neurons to 25% and reduced the decrease in striatal TH+ immunostaining to 34% of control.Conclusion
Our study demonstrates that the brain-RAS plays an important neuroprotective role in the MPTP model of PD and points to AT1 receptor as a potential novel target for neuroprotection. 相似文献114.
Pre-term birth is the leading cause of perinatal and neonatal mortality, 40% of which are attributed to the pre-term premature rupture of amnion. Rupture of amnion is thought to be associated with a corresponding decrease in the extracellular collagen content and/or increase in collagenase activity. However, there is very little information concerning the detailed organisation of fibrillar collagen in amnion and how this might influence rupture. Here we identify a loss of lattice like arrangement in collagen organisation from areas near to the rupture site, and present a 9% increase in fibril spacing and a 50% decrease in fibrillar organisation using quantitative measurements gained by transmission electron microscopy and the novel application of synchrotron X-ray diffraction. These data provide an accurate insight into the biomechanical process of amnion rupture and highlight X-ray diffraction as a new and powerful tool in our understanding of this process. 相似文献
115.
Due to its inherent asymmetry, competition for light is thought to cause loss of diversity from eutrophied systems. However, most of the work on this topic in grasslands has been phenomenological and has not measured light directly. We present the results of one of the few mechanistic experiments investigating the outcome of short-term competition using measurements of light interception from monocultures of five perennial grass species grown under fertilized and irrigated conditions. We found that the level of incident light intercepted by each species in monoculture, a direct measure of resource-reduction ability, was an excellent predictor of the relative competitive effect in pairwise mixtures. Competition for light was asymmetric in relation to differences in light intercepting ability. Our results are consistent with the idea that when light is a limiting resource, competition between species for this resource can be asymmetric, contributing to high dominance and low diversity. 相似文献
116.
117.
Prospero is required in dividing longitudinal glia (LG) during axon guidance; initially to enable glial division in response to neuronal contact, and subsequently to maintain glial precursors in a quiescent state with mitotic potential. Only Prospero-positive LG respond to neuronal ablation by over-proliferating, mimicking a glial-repair response. Prospero is distributed unequally through the progeny cells of the longitudinal glioblast lineage. Just before axon contact the concentration of Prospero is higher in two of the four progeny cells, and after axon guidance Prospero is present only in six out of ten progeny LG. Here we ask how Prospero is distributed unequally in these two distinct phases. We show that before neuronal contact, longitudinal glioblasts undergo invaginating divisions, perpendicular to the ectodermal layer. Miranda is required to segregate Prospero asymmetrically up to the four glial-progeny stage. After neuronal contact, Prospero is present in only the LG that activate Notch signalling in response to Serrate provided by commissural axons, and Numb is restricted to the glia that do not contain Prospero. As a result of this dual regulation of Prospero deployment, glia are coupled to the formation and maintenance of axonal trajectories. 相似文献
118.
Susanna-Assunta Sansone Daniel Schober Helen J. Atherton Oliver Fiehn Helen Jenkins Philippe Rocca-Serra Denis V. Rubtsov Irena Spasic Larisa Soldatova Chris Taylor Andy Tseng Mark R. Viant 《Metabolomics : Official journal of the Metabolomic Society》2007,3(3):249-256
In this article we present the activities of the Ontology Working Group (OWG) under the Metabolomics Standards Initiative
(MSI) umbrella. Our endeavour aims to synergise the work of several communities, where independent activities are underway
to develop terminologies and databases for metabolomics investigations. We have joined forces to rise to the challenges associated
with interpreting and integrating experimental process and data across disparate sources (software and databases, private
and public). Our focus is to support the activities of the other MSI working groups by developing a common semantic framework
to enable metabolomics-user communities to consistently annotate the experimental process and to enable meaningful exchange
of datasets. Our work is accessible via a public webpage and a draft ontology has been posted under the Open Biological Ontology
umbrella. At the very outset, we have agreed to minimize duplications across omics domains through extensive liaisons with
other communities under the OBO Foundry. This is work in progress and we welcome new participants willing to volunteer their
time and expertise to this open effort.
See the MSI Ontology Working Group website for a complete list of members and contributors. Web URL: 相似文献
119.
120.