全文获取类型
收费全文 | 36840篇 |
免费 | 16492篇 |
国内免费 | 12篇 |
出版年
2023年 | 79篇 |
2022年 | 199篇 |
2021年 | 594篇 |
2020年 | 2300篇 |
2019年 | 3855篇 |
2018年 | 3997篇 |
2017年 | 4276篇 |
2016年 | 4374篇 |
2015年 | 4478篇 |
2014年 | 4214篇 |
2013年 | 4817篇 |
2012年 | 2583篇 |
2011年 | 2345篇 |
2010年 | 3653篇 |
2009年 | 2290篇 |
2008年 | 1348篇 |
2007年 | 889篇 |
2006年 | 845篇 |
2005年 | 854篇 |
2004年 | 833篇 |
2003年 | 741篇 |
2002年 | 729篇 |
2001年 | 355篇 |
2000年 | 255篇 |
1999年 | 243篇 |
1998年 | 176篇 |
1997年 | 102篇 |
1996年 | 111篇 |
1995年 | 110篇 |
1994年 | 107篇 |
1993年 | 105篇 |
1992年 | 88篇 |
1991年 | 78篇 |
1990年 | 85篇 |
1989年 | 59篇 |
1988年 | 71篇 |
1987年 | 61篇 |
1986年 | 51篇 |
1985年 | 78篇 |
1984年 | 69篇 |
1983年 | 67篇 |
1982年 | 71篇 |
1981年 | 66篇 |
1980年 | 66篇 |
1979年 | 49篇 |
1978年 | 51篇 |
1977年 | 52篇 |
1976年 | 52篇 |
1974年 | 44篇 |
1973年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Victoria Levterova Stefan Panaiotov Nadia Brankova Kristin Tankova 《Molecular biotechnology》2010,45(1):34-38
Identification of genetic markers involved in stress response to physical factors or chemical substances in organisms is a
challenging task. Typing of upregulated gene expression due to selective antibacterial pressure is a promising approach in
the search of molecular mechanisms responsible for development of resistance. cDNA-Fluorescent Amplified Fragment Length Polymorphism
(cDNA-FAFLP) strategy was developed and applied in the search of antimycotic drug resistance marker(s) in medically important
fungi as an alternative method to microarray analysis. We compared differential gene expression of two sensitive Candida albicans reference strains (ATCC 10231 and ATCC 60133) and two of their paired resistant to fluconazole and itraconazole mutants.
Resistant mutants Candida albicans
FLC-R, resistant to fluconazole (MIC > 128 μg/ml) and Candida albicans ICZ-R, resistant to itraconazole (MIC > 4 μg/ml) were obtained in subcultures with gradual increase of the antifungal in the culture
medium. cDNA-AFLP profile in both itraconazole resistant mutants showed specific spectrophotometric peaks with 5–6-fold RNA
overexpression product of 500 bp length compared to the sensitive strains. Fluconazole mutants do not reveal RNA level changes
under tested by us typing conditions. These results indicate that the cDNA-FAFLP strategy is a relatively rapid, simple, and
reliable method for simultaneous typing of both constitutive and induced differences in expression of host genes providing
insight into the biological processes involved in response to drugs in bacteria and fungi. Moreover, this methodology could
be tested for typing of the genome response of any organism to physical or chemical stress factors. 相似文献
62.
63.
Body size but not colony size increases with altitude in the holarctic ant,Leptothorax acervorum
下载免费PDF全文
![点击此处可从《Ecological Entomology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
ABEL BERNADOU CHRISTINE RÖMERMANN NANA GRATIASHVILI JÜRGEN HEINZE 《Ecological Entomology》2016,41(6):733-736
1. Bergmann's rule states that organisms inhabiting colder environments show an increase in body size or mass in comparison to their conspecifics living in warmer climates. Although originally proposed for homoeothermic vertebrates, this rule was later extended to ectotherms. In social insects, only a few studies have tested this rule and the results were ambiguous. Here, ‘body size’ can be considered at two different levels (the size of the individual workers or the size of the colony). 2. In this study, data from 53 nests collected along altitudinal gradients in the Alps were used to test the hypotheses that the worker body size and colony size of the ant Leptothorax acervorum increase with increasing altitude and therefore follow Bergmann's rule. 3. The results show that the body size of workers but not the colony size increases with altitude. Whether this pattern is driven by starvation resistance or other mechanisms remains to be investigated. 相似文献
64.
65.
66.
67.
68.
T. Phanitchat C. Apiwathnasorn S. Sungvornyothin Y. Samung S. Dujardin J.‐P. Dujardin S. Sumruayphol 《Medical and veterinary entomology》2019,33(4):476-484
Wing geometry helps to identify mosquito species, even cryptic ones. On the other hand, temperature has a well‐known effect on insect metric properties. Can such effects blur the taxonomic signal embedded in the wing? Two strains of Aedes albopictus (laboratory and field strain) were examined under three different rearing temperatures (26, 30 and 33 °C) using landmark‐ and outline‐based morphometric approaches. The wings of each experimental line were compared with Aedes aegypti. Both approaches indicated similar associations between wing size and temperature. For the laboratory strain, the wing size significantly decreased as the temperature increased. For the field strain, the largest wings were observed at the intermediate temperature. The two morphometric approaches describing shape showed different sensibilities to temperature. For both strains and sexes, the landmark‐based approach disclosed significant wing shape changes with temperature changes. The outline‐based approach showed lesser effects, detecting significant changes only in laboratory females and in field males. Despite the size and shape changes induced by temperature, the two strains of Ae. albopictus were always distinguished from Ae. aegypti. The present study confirms the lability of size. However, it also suggests that, despite environmentally‐induced variation, the architecture of the wing still provides a strong taxonomic signal. 相似文献
69.
Lauren Petrullo Matthew J. Jorgensen Noah Snyder‐Mackler Amy Lu 《American journal of primatology》2019,81(10-11)
The human milk microbiome is vertically transmitted to offspring during the postnatal period and has emerged as a critical driver of infant immune and metabolic development. Despite this importance in humans, the milk microbiome of nonhuman primates remains largely unexplored. This dearth of comparative work precludes our ability to understand how species‐specific differences in the milk microbiome may differentially drive maternal effects and limits how translational models can be used to understand the role of vertically transmitted milk microbes in human development. Here, we present the first culture‐independent data on the milk microbiome of a nonhuman primate. We collected milk and matched fecal microbiome samples at early and late lactation from a cohort of captive lactating vervet monkeys (N = 15). We found that, similar to humans, the vervet monkey milk microbiome comprises a shared community of taxa that are universally present across individuals. However, unlike in humans, this shared community is dominated by the genera Lactobacillus, Bacteroides, and Prevotella. We also found that, in contrast to previous culture‐dependent studies in humans, the vervet milk microbiome exhibits greater alpha‐diversity than the gut microbiome across lactation. Finally, we did not find support for the translocation of microbes from the gut to the mammary gland within females (i.e., “entero‐mammary pathway”). Taken together, our results show that the vervet monkey milk microbiome is taxonomically diverse, distinct from the gut microbiome, and largely stable. These findings demonstrate that the milk microbiome is a unique substrate that may selectively favor the establishment and persistence of particular microbes across lactation and highlights the need for future experimental studies on the origin of microbes in milk. 相似文献
70.