全文获取类型
收费全文 | 3164篇 |
免费 | 242篇 |
专业分类
3406篇 |
出版年
2022年 | 23篇 |
2021年 | 21篇 |
2019年 | 24篇 |
2018年 | 33篇 |
2017年 | 20篇 |
2016年 | 58篇 |
2015年 | 104篇 |
2014年 | 97篇 |
2013年 | 129篇 |
2012年 | 207篇 |
2011年 | 193篇 |
2010年 | 117篇 |
2009年 | 100篇 |
2008年 | 162篇 |
2007年 | 137篇 |
2006年 | 146篇 |
2005年 | 155篇 |
2004年 | 146篇 |
2003年 | 151篇 |
2002年 | 142篇 |
2001年 | 37篇 |
2000年 | 37篇 |
1999年 | 30篇 |
1998年 | 58篇 |
1997年 | 31篇 |
1996年 | 28篇 |
1995年 | 38篇 |
1994年 | 32篇 |
1993年 | 31篇 |
1992年 | 22篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 24篇 |
1988年 | 33篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1982年 | 30篇 |
1981年 | 32篇 |
1980年 | 31篇 |
1979年 | 26篇 |
1978年 | 27篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1975年 | 19篇 |
1973年 | 19篇 |
1972年 | 19篇 |
1965年 | 13篇 |
排序方式: 共有3406条查询结果,搜索用时 9 毫秒
71.
V Gallo JP Mackenbach M Ezzati G Menvielle AE Kunst S Rohrmann R Kaaks B Teucher H Boeing MM Bergmann A Tjønneland SO Dalton K Overvad ML Redondo A Agudo A Daponte L Arriola C Navarro AB Gurrea KT Khaw N Wareham T Key A Naska A Trichopoulou D Trichopoulos G Masala S Panico P Contiero R Tumino HB Bueno-de-Mesquita PD Siersema PP Peeters S Zackrisson M Almquist S Eriksson G Hallmans G Skeie T Braaten E Lund AK Illner T Mouw E Riboli P Vineis 《PloS one》2012,7(7):e39013
Background
Socio-economic inequalities in mortality are observed at the country level in both North America and Europe. The purpose of this work is to investigate the contribution of specific risk factors to social inequalities in cause-specific mortality using a large multi-country cohort of Europeans.Methods
A total of 3,456,689 person/years follow-up of the European Prospective Investigation into Cancer and Nutrition (EPIC) was analysed. Educational level of subjects coming from 9 European countries was recorded as proxy for socio-economic status (SES). Cox proportional hazard model''s with a step-wise inclusion of explanatory variables were used to explore the association between SES and mortality; a Relative Index of Inequality (RII) was calculated as measure of relative inequality.Results
Total mortality among men with the highest education level is reduced by 43% compared to men with the lowest (HR 0.57, 95% C.I. 0.52–0.61); among women by 29% (HR 0.71, 95% C.I. 0.64–0.78). The risk reduction was attenuated by 7% in men and 3% in women by the introduction of smoking and to a lesser extent (2% in men and 3% in women) by introducing body mass index and additional explanatory variables (alcohol consumption, leisure physical activity, fruit and vegetable intake) (3% in men and 5% in women). Social inequalities were highly statistically significant for all causes of death examined in men. In women, social inequalities were less strong, but statistically significant for all causes of death except for cancer-related mortality and injuries.Discussion
In this European study, substantial social inequalities in mortality among European men and women which cannot be fully explained away by accounting for known common risk factors for chronic diseases are reported. 相似文献72.
Sabrina Briefer Freymond Elodie F. Briefer Rudolf Von Niederh?usern Iris Bachmann 《PloS one》2013,8(1)
Horses are often kept in individual stables, rather than in outdoor groups, despite such housing system fulfilling many of their welfare needs, such as the access to social partners. Keeping domestic stallions in outdoor groups would mimic bachelor bands that are found in the wild. Unfortunately, the high level of aggression that unfamiliar stallions display when they first encounter each other discourages owners from keeping them in groups. However, this level of aggression is likely to be particularly important only during group integration, when the dominance hierarchy is being established, whereas relatively low aggression rates have been observed among stable feral bachelor bands. We investigated the possibility of housing breeding stallions owned by the Swiss National Stud in groups on a large pasture (5 stallions in 2009 and 8 stallions in 2010). We studied the pattern of agonistic, ritual and affiliative interactions after group integration (17–23 days), and the factors influencing these interactions (time after group integration, dominance rank, age or experience of group housing). We found that stallions displayed generally more ritual than agonistic and than affiliative interactions. The frequency of agonistic and ritual interactions decreased quickly within the first three to four days. The frequency of affiliative interactions increased slowly with time before decreasing after 9–14 days. A stable hierarchy could be measured after 2–3 months. The highest-ranking males had less ritual interactions than the lowest-ranking. Males had also less agonistic, ritual and affiliative interactions if they had already been housed in a group the previous year. Therefore, we found that breeding stallions could be housed together on a large pasture, because the frequency of agonistic interactions decreased quickly and remained at a minimal level from the fourth day following group integration. This housing system could potentially increase horse welfare and reduce labour associated with horse management. 相似文献
73.
Heterogeneous perfusion is a consequence of uniform shear stress in optimized arterial tree models 总被引:1,自引:0,他引:1
Schreiner W Karch R Neumann M Neumann F Roedler SM Heinze G 《Journal of theoretical biology》2003,220(3):285-301
Using optimized computer models of arterial trees we demonstrate that flow heterogeneity is a necessary consequence of a uniform shear stress distribution. Model trees are generated and optimized under different modes of boundary conditions. In one mode flow is delivered to the tissue as homogeneously as possible. Although this primary goal can be achieved, resulting shear stresses between blood and the vessel walls show very large spread. In a second mode, models are optimized under the condition of uniform shear stress in all segments which in turn renders flow distribution heterogeneous. Both homogeneous perfusion and uniform shear stress are desirable goals in real arterial trees but each of these goals can only be approached at the expense of the other. While the present paper refers only to optimized models, we assume that this dual relation between the heterogeneities in flow and shear stress may represent a more general principle of vascular systems. 相似文献
74.
Camarero G Tyrsin OY Xiang C Pfeiffer V Pleiser S Wiese S Götz R Rapp UR 《Molecular and cellular biology》2006,26(19):7103-7115
We have previously shown that mice lacking the protein kinase B-RAF have defects in both neural and endothelial cell lineages and die around embryonic day 12 (E12). To delineate the function of B-RAF in the brain, B-RAF KIN/KIN mice lacking B-RAF and expressing A-RAF under the control of the B-RAF locus were created. B-RAF KIN/KIN embryos displayed no vascular defects, no endothelial and neuronal apoptosis, or gross developmental abnormalities, and a significant proportion of these animals survived for up to 8 weeks. Cell proliferation in the neocortex was reduced from E14.5 onwards. Newborn cortical neurons were impaired in their migration toward the cortical plate, causing a depletion of Brn-2-expressing pyramidal neurons in layers II, III, and V of the postnatal cortex. Our data reveal that B-RAF is an important mediator of neuronal survival, migration, and dendrite formation and that A-RAF cannot fully compensate for these functions. 相似文献
75.
76.
Berthold F. Matzanke Rudolf Böhnke Ute Möllmann Volker Schünemann Gisbert Schumann Alfred X. Trautwein G. Winkelmann 《Biometals》1999,12(4):315-321
Transport and metabolization of iron bound to the fungal siderophore rhizoferrin was analyzed by transport kinetics, Mössbauer and EPR spectroscopy. Saturation kinetics (v
max=24.4 pmol/(mg min), K
m=64.4M) and energy dependence excluded diffusion and provided evidence for a rhizoferrin transport system in M. smegmatis. Based on the spectroscopic techniques indications for intracellular presence of the ferric rhizoferrin complex were found. This feature could be of practical importance in the search of novel drugs for the treatment of mycobacterial infections. EPR and Mössbauer spectroscopy revealed different ferritin mineral cores depending on the siderophore iron source. This finding was interpreted in terms of different protein shells, i.e. two types of ferritins. 相似文献
77.
78.
79.
80.
Erin Styles Ji-Young Youn Mojca Mattiazzi Usaj Brenda Andrews 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1629)
The budding yeast Saccharomyces cerevisiae has been used extensively for the study of cell polarity, owing to both its experimental tractability and the high conservation of cell polarity and other basic biological processes among eukaryotes. The budding yeast has also served as a pioneer model organism for virtually all genome-scale approaches, including functional genomics, which aims to define gene function and biological pathways systematically through the analysis of high-throughput experimental data. Here, we outline the contributions of functional genomics and high-throughput methodologies to the study of cell polarity in the budding yeast. We integrate data from published genetic screens that use a variety of functional genomics approaches to query different aspects of polarity. Our integrated dataset is enriched for polarity processes, as well as some processes that are not intrinsically linked to cell polarity, and may provide new areas for future study. 相似文献