全文获取类型
收费全文 | 91687篇 |
免费 | 4060篇 |
国内免费 | 11044篇 |
出版年
2023年 | 912篇 |
2022年 | 990篇 |
2021年 | 1806篇 |
2020年 | 1611篇 |
2019年 | 2371篇 |
2018年 | 2537篇 |
2017年 | 1703篇 |
2016年 | 1891篇 |
2015年 | 2282篇 |
2014年 | 3300篇 |
2013年 | 4692篇 |
2012年 | 2964篇 |
2011年 | 2652篇 |
2010年 | 2047篇 |
2009年 | 2744篇 |
2008年 | 3008篇 |
2007年 | 3667篇 |
2006年 | 3772篇 |
2005年 | 3752篇 |
2004年 | 3844篇 |
2003年 | 3407篇 |
2002年 | 3276篇 |
2001年 | 2840篇 |
2000年 | 2147篇 |
1999年 | 2406篇 |
1998年 | 2150篇 |
1997年 | 1679篇 |
1996年 | 1586篇 |
1995年 | 1585篇 |
1994年 | 1712篇 |
1993年 | 1502篇 |
1992年 | 1336篇 |
1991年 | 1256篇 |
1990年 | 1055篇 |
1989年 | 899篇 |
1988年 | 905篇 |
1987年 | 711篇 |
1985年 | 2101篇 |
1984年 | 3116篇 |
1983年 | 2067篇 |
1982年 | 2449篇 |
1981年 | 2082篇 |
1980年 | 1929篇 |
1979年 | 1709篇 |
1978年 | 1563篇 |
1977年 | 1432篇 |
1976年 | 1313篇 |
1975年 | 1111篇 |
1974年 | 1099篇 |
1973年 | 1028篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
51.
52.
Jin Wei Mia Madel Alfajaro Peter C. DeWeirdt Ruth E. Hanna William J. Lu-Culligan Wesley L. Cai Madison S. Strine Shang-Min Zhang Vincent R. Graziano Cameron O. Schmitz Jennifer S. Chen Madeleine C. Mankowski Renata B. Filler Neal G. Ravindra Victor Gasque Fernando J. de Miguel Ajinkya Patil Huacui Chen Craig B. Wilen 《Cell》2021,184(1):76-91.e13
53.
Charles L. Nunn Peter H. Thrall Kelly Stewart Alexander H. Harcourt 《Evolutionary ecology》2008,22(4):519-543
Emerging infectious diseases threaten a wide diversity of animals, and important questions remain concerning disease emergence
in socially structured populations. We developed a spatially explicit simulation model to investigate whether—and under what
conditions—disease-related mortality can impact rates of pathogen spread in populations of polygynous groups. Specifically,
we investigated whether pathogen-mediated dispersal (PMD) can occur when females disperse after the resident male dies from
disease, thus carrying infections to new groups. We also examined the effects of incubation period and virulence, host mortality
and rates of background dispersal, and we used the model to investigate the spread of the virus responsible for Ebola hemorrhagic
fever, which currently is devastating African ape populations. Output was analyzed using regression trees, which enable exploration
of hierarchical and non-linear relationships. Analyses revealed that the incidence of disease in single-male (polygynous)
groups was significantly greater for those groups containing an average of more than six females, while the total number of
infected hosts in the population was most sensitive to the number of females per group. Thus, as expected, PMD occurs in polygynous
groups and its effects increase as harem size (the number of females) increases. Simulation output further indicated that
population-level effects of Ebola are likely to differ among multi-male–multi-female chimpanzees and polygynous gorillas,
with larger overall numbers of chimpanzees infected, but more gorilla groups becoming infected due to increased dispersal
when the resident male dies. Collectively, our results highlight the importance of social system on the spread of disease
in wild mammals. 相似文献
54.
Herbert L. Needleman 《人类与生态风险评估》2005,11(1):153-157
In the environmental health literature, errors in interpreting studies or data are not infrequent. Many are of the Type II variety. Common solecisms of this type are: treating the criterion of p < 0.05 as a sacrament; demanding complete confounder control; arguing for the existence of phantom confounders; arguing that the effect size is trivial; building nonveridical models; arguing for no effect from inadequate sample size; demanding causal proof; arguing that causality is reversed; conducting a ballot of published studies. These are examined in this paper. 相似文献
55.
56.
Hugh S. Keeping Peter H. Jellinck 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,632(2):150-158
Iodide administered in the drinking water for 5–7 days increased the activity of estradiol-induced uterine peroxidase in the immature rat. This effect was specific for iodide and could not be mimicked by chloride, bromide, thiocyanate, perchlorate or iodate. Sodium iodide also increased peroxidase activity in the parotid gland but had no effect on glucose-6-phosphate dehydrogenase in the uterus, thyroid or parotid even though estradiol produced a 2-fold increase in the activity of this enzyme in the uterus. 125I was taken up more readily by the uterus than by muscle but this process was not influenced by prior treatment of the animals with estrogen. The in vitro effect of sulfhydryl reagents on uterine peroxidase was also investigated and proposals made for possible mechanisms of action of iodide on this enzyme in the intact animal. 相似文献
57.
58.
59.
A.S. Tsaftaris J.C. Sorenson J.G. Scandalios 《Biochemical and biophysical research communications》1980,92(3):889-895
A protein isolated from maize scutella which inhibits catalase in vitro has been shown to contain 12% carbohydrate in the form of galactose. This corresponds to four galactose molecules per inhibitor subunit. Removal of the carbohydrate with β-galactosidase or blockage with a galactose-specific lectin abolished activity of the inhibitor. 相似文献
60.
Elucidation of the pathogenesis in respiratory chain diseases is of great importance for developing specific treatments. The limitations inherent to the use of patient material make studies of human tissues often difficult and the mouse has therefore emerged as a suitable model organism for studies of respiratory chain diseases. In this review, we present an overview of the field and discuss in depth a few examples of animal models reproducing pathology of human disease with primary and secondary respiratory chain involvement. 相似文献