全文获取类型
收费全文 | 4547篇 |
免费 | 438篇 |
国内免费 | 1篇 |
出版年
2023年 | 19篇 |
2022年 | 69篇 |
2021年 | 115篇 |
2020年 | 60篇 |
2019年 | 83篇 |
2018年 | 68篇 |
2017年 | 86篇 |
2016年 | 135篇 |
2015年 | 224篇 |
2014年 | 228篇 |
2013年 | 248篇 |
2012年 | 340篇 |
2011年 | 286篇 |
2010年 | 165篇 |
2009年 | 150篇 |
2008年 | 234篇 |
2007年 | 190篇 |
2006年 | 191篇 |
2005年 | 208篇 |
2004年 | 166篇 |
2003年 | 146篇 |
2002年 | 144篇 |
2001年 | 83篇 |
2000年 | 106篇 |
1999年 | 93篇 |
1998年 | 39篇 |
1997年 | 42篇 |
1996年 | 36篇 |
1995年 | 36篇 |
1994年 | 35篇 |
1993年 | 33篇 |
1992年 | 66篇 |
1991年 | 59篇 |
1990年 | 50篇 |
1989年 | 50篇 |
1988年 | 54篇 |
1987年 | 40篇 |
1986年 | 39篇 |
1985年 | 43篇 |
1984年 | 37篇 |
1983年 | 36篇 |
1982年 | 30篇 |
1981年 | 19篇 |
1979年 | 26篇 |
1978年 | 31篇 |
1977年 | 29篇 |
1976年 | 22篇 |
1975年 | 25篇 |
1973年 | 18篇 |
1971年 | 24篇 |
排序方式: 共有4986条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
945.
946.
947.
Naomi Drexler Mark Miller Justin Gerding Suzanne Todd Laura Adams F. Scott Dahlgren Nelva Bryant Erica Weis Kristen Herrick Jessica Francies Kenneth Komatsu Stephen Piontkowski Jose Velascosoltero Timothy Shelhamer Brian Hamilton Carmen Eribes Anita Brock Patsy Sneezy Cye Goseyun Harty Bendle Regina Hovet Velda Williams Robert Massung Jennifer H. McQuiston 《PloS one》2014,9(12)
Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a significant public health risk on American Indian reservations in eastern Arizona. During 2003–2012, more than 250 RMSF cases and 19 deaths were documented among Arizona''s American Indian population. The high case fatality rate makes community-level interventions aimed at rapid and sustained reduction of ticks urgent. Beginning in 2012, a two year pilot integrated tick prevention campaign called the RMSF Rodeo was launched in a ∼600-home tribal community with high rates of RMSF. During year one, long-acting tick collars were placed on all dogs in the community, environmental acaricides were applied to yards monthly, and animal care practices such as spay and neuter and proper tethering procedures were encouraged. Tick levels, indicated by visible inspection of dogs, tick traps and homeowner reports were used to monitor tick presence and evaluate the efficacy of interventions throughout the project. By the end of year one, <1% of dogs in the RMSF Rodeo community had visible tick infestations five months after the project was started, compared to 64% of dogs in Non-Rodeo communities, and environmental tick levels were reduced below detectable levels. The second year of the project focused on use of the long-acting collar alone and achieved sustained tick control with fewer than 3% of dogs in the RMSF Rodeo community with visible tick infestations by the end of the second year. Homeowner reports of tick activity in the domestic and peridomestic setting showed similar decreases in tick activity compared to the non-project communities. Expansion of this successful project to other areas with Rhipicephalus-transmitted RMSF has the potential to reduce brown dog tick infestations and save human lives. 相似文献
948.
Moira M. Ferguson David L. G. Noakes 《Ethology : formerly Zeitschrift fur Tierpsychologie》1983,62(1):72-86
Brook charr (Salvelinus fontinalis) defend territories and show high levels of agonistic behaviour. In contrast, lake charr (S. namaycush) are non-territorial and rarely show any agonistic behaviour. The genetic determinance of behavioural differences between these species was confirmed by the behavioural similarity of brook charr backcross hybrids and brook charr and a significant maternal effect on hybrid behavioural phenotypes. Backcross and F2 generations showed either one of two distinct behavioural strategies, one aggressive and territorial and the other non-aggressive and non-territorial. It seems most likely that these strategies are conditional on individual phenotypes, such as size of nearby conspecifics. However, precise measurements of costs and benefits of each strategy are required to distinguish between these alternate hypotheses for either species. Each action pattern was an independent pattern of variation and a distinct behavioural unit. However, patterns were coordinated with all other patterns at a higher hierarchical level (corresponding to the particular behavioural strategy). It seems most likely that these strategies would be controlled by a polygenic system, even though the nature of our data does not allow us to make firm conclusions in this regard. 相似文献
949.
Marie Manceau Vera S. Domingues Catherine R. Linnen Erica Bree Rosenblum Hopi E. Hoekstra 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1552):2439-2450
Convergence—the independent evolution of the same trait by two or more taxa—has long been of interest to evolutionary biologists, but only recently has the molecular basis of phenotypic convergence been identified. Here, we highlight studies of rapid evolution of cryptic coloration in vertebrates to demonstrate that phenotypic convergence can occur at multiple levels: mutations, genes and gene function. We first show that different genes can be responsible for convergent phenotypes even among closely related populations, for example, in the pale beach mice inhabiting Florida''s Gulf and Atlantic coasts. By contrast, the exact same mutation can create similar phenotypes in distantly related species such as mice and mammoths. Next, we show that different mutations in the same gene need not be functionally equivalent to produce similar phenotypes. For example, separate mutations produce divergent protein function but convergent pale coloration in two lizard species. Similarly, mutations that alter the expression of a gene in different ways can, nevertheless, result in similar phenotypes, as demonstrated by sister species of deer mice. Together these studies underscore the importance of identifying not only the genes, but also the precise mutations and their effects on protein function, that contribute to adaptation and highlight how convergence can occur at different genetic levels. 相似文献
950.