全文获取类型
收费全文 | 1443篇 |
免费 | 119篇 |
出版年
2023年 | 6篇 |
2022年 | 24篇 |
2021年 | 53篇 |
2020年 | 19篇 |
2019年 | 50篇 |
2018年 | 34篇 |
2017年 | 35篇 |
2016年 | 64篇 |
2015年 | 83篇 |
2014年 | 98篇 |
2013年 | 109篇 |
2012年 | 133篇 |
2011年 | 119篇 |
2010年 | 86篇 |
2009年 | 74篇 |
2008年 | 76篇 |
2007年 | 80篇 |
2006年 | 60篇 |
2005年 | 49篇 |
2004年 | 46篇 |
2003年 | 33篇 |
2002年 | 32篇 |
2001年 | 19篇 |
2000年 | 8篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1968年 | 2篇 |
排序方式: 共有1562条查询结果,搜索用时 46 毫秒
131.
Guillaume Gayet Cyril Eraud Maurice Benmergui Joël Broyer François Mesleard Hervé Fritz Matthieu Guillemain 《European Journal of Wildlife Research》2011,57(5):1051-1056
A number of native and exotic animal species show dramatic population increases in terms of both numbers and geographic range.
Understanding the habitat selection processes behind such increases is crucial to implement adequate management measures.
Mute swan (Cygnus olor) populations have experienced a tremendous demographic and geographic expansion in Western Europe during the twentieth century,
colonizing a wide variety of aquatic habitats. We aimed at assessing how swans select nesting sites during the pre-laying
and laying periods on medium to large fishponds (from 10 to 50 ha) in Eastern France, while accounting for detectability biases
and testing for the effects of fishpond spatial configuration, vegetation resources, human disturbance and habitat management.
Our results demonstrate that the mute swan is a non-selective species regarding its nesting habitat among such fishponds,
using these independently from the parameters considered although fishpond characteristics varied. Although mute swan is one
of the least cryptic Anatidae, owing to its white colour and large size, detection of breeding pairs remained imperfect for
each over several sampling occasions. However, because we repeated the sampling sessions, detection of swan pairs by the end
of the monitoring period was as high as 0.94. These results are consistent with previous assertions that the mute swan is
a species of high ecological plasticity, which may partly explain its recent colonization rates. Given that even swan breeding
events were imperfectly detected on each occasion, we highlight the fact that most studies of breeding ducks (which are more
cryptic) would be considerably improved by better considering detection biases. 相似文献
132.
There is now ample evidence that plant development, responses to abiotic environments, and immune responses are tightly intertwined in their physiology. Thus optimization of the immune system during evolution will occur in coordination with that of plant development. Two alternative and possibly complementary forces are at play: genetic constraints due to the pleiotropic action of players in both systems, and coevolution, if developmental changes modulate the cost-benefit balance of immunity. A current challenge is to elucidate the ecological forces driving evolution of quantitative variation for defense at molecular level. The analysis of natural co-variation for developmental and immunity traits in Arabidopsis thaliana promises to bring important insights. 相似文献
133.
134.
Genome-Wide Association Studies are powerful tools to detect genetic variants associated with diseases. Their results have, however, been questioned, in part because of the bias induced by population stratification. This is a consequence of systematic differences in allele frequencies due to the difference in sample ancestries that can lead to both false positive or false negative findings. Many strategies are available to account for stratification but their performances differ, for instance according to the type of population structure, the disease susceptibility locus minor allele frequency, the degree of sampling imbalanced, or the sample size. We focus on the type of population structure and propose a comparison of the most commonly used methods to deal with stratification that are the Genomic Control, Principal Component based methods such as implemented in Eigenstrat, adjusted Regressions and Meta-Analyses strategies. Our assessment of the methods is based on a large simulation study, involving several scenarios corresponding to many types of population structures. We focused on both false positive rate and power to determine which methods perform the best. Our analysis showed that if there is no population structure, none of the tests led to a bias nor decreased the power except for the Meta-Analyses. When the population is stratified, adjusted Logistic Regressions and Eigenstrat are the best solutions to account for stratification even though only the Logistic Regressions are able to constantly maintain correct false positive rates. This study provides more details about these methods. Their advantages and limitations in different stratification scenarios are highlighted in order to propose practical guidelines to account for population stratification in Genome-Wide Association Studies. 相似文献
135.
136.
137.
Cobo F Stacey GN Hunt C Cabrera C Nieto A Montes R Cortés JL Catalina P Barnie A Concha A 《Applied microbiology and biotechnology》2005,68(4):456-466
The transplant of cells of human origin is an increasingly complex sector of medicine which entails great opportunities for
the treatment of a range of diseases. Stem cell banks should assure the quality, traceability and safety of cultures for transplantation
and must implement an effective programme to prevent contamination of the final product. In donors, the presence of infectious
micro-organisms, like human immunodeficiency virus, hepatitis B virus, hepatitis C virus and human T cell lymphotrophic virus,
should be evaluated in addition to the possibility of other new infectious agents (e.g. transmissible spongiform encephalopathies
and severe acute respiratory syndrome). The introduction of the nucleic acid amplification can avoid the window period of
these viral infections. Contamination from the laboratory environment can be achieved by routine screening for bacteria, fungi,
yeast and mycoplasma by European pharmacopoeia tests. Fastidious micro-organisms, and an adventitious or endogenous virus,
is a well-known fact that will also have to be considered for processes involving in vitro culture of stem cells. It is also
a standard part of current good practice in stem cell banks to carry out routine environmental microbiological monitoring
of the cleanrooms where the cell cultures and their products are prepared. The risk of viral contamination from products of
animal origin, like bovine serum and mouse fibroblasts as a “feeder layer” for the development of embryonic cell lines, should
also be considered. Stem cell lines should be tested for prion particles and a virus of animal origin that assure an acceptable
quality. 相似文献
138.
Orbital and maxillofacial computer aided surgery: patient-specific finite element models to predict surgical outcomes 总被引:2,自引:0,他引:2
Luboz V Chabanas M Swider P Payan Y 《Computer methods in biomechanics and biomedical engineering》2005,8(4):259-265
This paper addresses an important issue raised for the clinical relevance of Computer-Assisted Surgical applications, namely the methodology used to automatically build patient-specific finite element (FE) models of anatomical structures. From this perspective, a method is proposed, based on a technique called the mesh-matching method, followed by a process that corrects mesh irregularities. The mesh-matching algorithm generates patient-specific volume meshes from an existing generic model. The mesh regularization process is based on the Jacobian matrix transform related to the FE reference element and the current element.This method for generating patient-specific FE models is first applied to computer-assisted maxillofacial surgery, and more precisely, to the FE elastic modelling of patient facial soft tissues. For each patient, the planned bone osteotomies (mandible, maxilla, chin) are used as boundary conditions to deform the FE face model, in order to predict the aesthetic outcome of the surgery. Seven FE patient-specific models were successfully generated by our method. For one patient, the prediction of the FE model is qualitatively compared with the patient's post-operative appearance, measured from a computer tomography scan. Then, our methodology is applied to computer-assisted orbital surgery. It is, therefore, evaluated for the generation of 11 patient-specific FE poroelastic models of the orbital soft tissues. These models are used to predict the consequences of the surgical decompression of the orbit. More precisely, an average law is extrapolated from the simulations carried out for each patient model. This law links the size of the osteotomy (i.e. the surgical gesture) and the backward displacement of the eyeball (the consequence of the surgical gesture). 相似文献
139.
valois (vls) was identified as a posterior group gene in the initial screens for Drosophila maternal-effect lethal mutations. Despite its early genetic identification, it has not been characterized at the molecular level until now. We show that vls encodes a divergent WD domain protein and that the three available EMS-induced point mutations cause premature stop codons in the vls ORF. We have generated a null allele that has a stronger phenotype than the EMS mutants. The vlsnull mutant shows that vls+ is required for high levels of Oskar protein to accumulate during oogenesis, for normal posterior localization of Oskar in later stages of oogenesis and for posterior localization of the Vasa protein during the entire process of pole plasm assembly. There is no evidence for vls being dependent on an upstream factor of the posterior pathway, suggesting that Valois protein (Vls) instead acts as a co-factor in the process. Based on the structure of Vls, the function of similar proteins in different systems and our phenotypic analysis, it seems likely that vls may promote posterior patterning by facilitating interactions between different molecules. 相似文献
140.
Sarkar S Floto RA Berger Z Imarisio S Cordenier A Pasco M Cook LJ Rubinsztein DC 《The Journal of cell biology》2005,170(7):1101-1111
Macroautophagy is a key pathway for the clearance of aggregate-prone cytosolic proteins. Currently, the only suitable pharmacologic strategy for up-regulating autophagy in mammalian cells is to use rapamycin, which inhibits the mammalian target of rapamycin (mTOR), a negative regulator of autophagy. Here we describe a novel mTOR-independent pathway that regulates autophagy. We show that lithium induces autophagy, and thereby, enhances the clearance of autophagy substrates, like mutant huntingtin and alpha-synucleins. This effect is not mediated by glycogen synthase kinase 3beta inhibition. The autophagy-enhancing properties of lithium were mediated by inhibition of inositol monophosphatase and led to free inositol depletion. This, in turn, decreased myo-inositol-1,4,5-triphosphate (IP3) levels. Our data suggest that the autophagy effect is mediated at the level of (or downstream of) lowered IP3, because it was abrogated by pharmacologic treatments that increased IP3. This novel pharmacologic strategy for autophagy induction is independent of mTOR, and may help treatment of neurodegenerative diseases, like Huntington's disease, where the toxic protein is an autophagy substrate. 相似文献