首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   11212篇
  免费   829篇
  国内免费   1篇
  2023年   103篇
  2022年   170篇
  2021年   354篇
  2020年   308篇
  2019年   330篇
  2018年   443篇
  2017年   343篇
  2016年   552篇
  2015年   672篇
  2014年   721篇
  2013年   842篇
  2012年   936篇
  2011年   881篇
  2010年   560篇
  2009年   484篇
  2008年   589篇
  2007年   567篇
  2006年   528篇
  2005年   374篇
  2004年   366篇
  2003年   300篇
  2002年   291篇
  2001年   180篇
  2000年   172篇
  1999年   145篇
  1998年   75篇
  1997年   61篇
  1996年   56篇
  1995年   46篇
  1994年   43篇
  1993年   39篇
  1992年   57篇
  1991年   44篇
  1990年   28篇
  1989年   53篇
  1988年   29篇
  1987年   22篇
  1986年   15篇
  1985年   22篇
  1984年   29篇
  1983年   30篇
  1982年   24篇
  1981年   13篇
  1980年   11篇
  1979年   14篇
  1978年   15篇
  1975年   10篇
  1974年   13篇
  1972年   9篇
  1971年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
The first checklist of the Peruvian Hymenoptera listed 1169 species and subspecies of aculeate wasps, including 173 species of Pompilidae, seven of Scoliidae, 39 of Sphecidae and 403 of Vespidae. Herein are reported 32 species as new for Peru based mainly on the collection of the Natural History Museum, London. The loss of the endemic status of two species is also reported: Entypus peruvianus (Rohwer) (Pompilidae: Pepsinae) and Omicron ruficolle schunkei Giordani Soika (Vespidae: Eumeninae).  相似文献   
973.
There are many complex interactions between transposable elements (TEs) and host genomes. Environmental changes that induce stressful conditions help to contribute for increasing complexity of these interactions. The transposon mariner-Mos1 increases its mobilization under mild heat stress. It has putative heat shock elements (HSEs), which are probably activated by heat shock factors (HSFs). Ultraviolet radiation (UVC) is a stressor that has been suggested as able to activate heat shock protein genes (Hsp). In this study, we test the hypothesis that if UVC induces Hsp expression, as heat does, it could also promote mariner-Mos1 transposition and mobilization. The Drosophila simulans white-peach is a mutant lineage that indicates the mariner-Mos1 transposition phenotypically through the formation of mosaic eyes. This lineage was exposed to UVC or mild heat stress (28 °C) in order to evaluate the induction of mariner-Mos1 expression by RT-qPCR, as well as the mariner-Mos1 mobilization activity based on the count number of red spots in the eyes. The effects of both treatments on the developmental time of flies and cell cycle progression were also investigated. Both the analysis of eyes and mariner-Mos1 gene expression indicate that UVC radiation has no effect in mariner-Mos1 transposition, although heat increases the expression and mobilization of this TE soon after the treatment. However, the expression of Hsp70 gene increased after 24 h of UVC exposure, suggesting different pathway of activation. These results showed that heat promotes mariner-Mos1 mobilization, although UVC does not induce the expression or mobilization of this TE.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-015-0611-2) contains supplementary material, which is available to authorized users.  相似文献   
974.
975.
Gatts  Pedro  Franco  Marcos  dos Santos  Luciano  Rocha  Diogo  de Sá  Fabrício  Netto  Eurico  Machado  Phillipe  Masi  Bruno  Zalmon  Ilana 《Aquatic Ecology》2015,49(3):343-355
Aquatic Ecology - To investigate how variations in the small-scale distance between patchy reef modules affect the structure and composition of the associated ichthyofauna, concrete reefballs were...  相似文献   
976.
977.
Phenotypic plasticity is a hallmark of the caste systems of social insects, expressed in their life history and morphological traits. These are best studied in bees. In their co-evolution with angiosperm plants, the females of corbiculate bees have acquired a specialized structure on their hind legs for collecting pollen. In the highly eusocial bees (Apini and Meliponini), this structure is however only present in workers and absent in queens. By means of histological sections and cell proliferation analysis we followed the developmental dynamics of the hind legs of queens and workers in the fourth and fifth larval instars. In parallel, we generated subtractive cDNA libraries for hind leg discs of queen and worker larvae by means of a Representational Difference Analysis (RDA). From the total of 135 unique sequences we selected 19 for RT-qPCR analysis, where six of these were confirmed as differing significantly in their expression between the two castes in the larval spinning stage. The development of complex structures such as the bees’ hind legs, requires diverse patterning mechanisms and signaling modules, as indicated by the set of differentially expressed genes related with cell adhesion and signaling pathways.  相似文献   
978.
Entry into host cells and intracellular persistence by invasive bacteria are tightly coupled to the ability of the bacterium to disrupt the eukaryotic cytoskeletal machinery. Herein we review the main strategies used by three intracellular pathogens to harness key modulators of the cytoskeleton. Two of these bacteria, namely Listeria monocytogenes and Salmonella enterica serovar Typhimurium, exhibit quite distinct intracellular lifestyles and therefore provide a comprehensive panel for the understanding of the intricate bacteria–cytoskeleton interplay during infections. The emerging intracellular pathogen Vibrio parahaemolyticus is depicted as a developing model for the uncovering of novel mechanisms used to hijack the cytoskeleton.  相似文献   
979.
980.

Background

Root system architecture is important for water acquisition and nutrient acquisition for all crops. In soybean breeding programs, wild soybean alleles have been used successfully to enhance yield and seed composition traits, but have never been investigated to improve root system architecture. Therefore, in this study, high-density single-feature polymorphic markers and simple sequence repeats were used to map quantitative trait loci (QTLs) governing root system architecture in an inter-specific soybean mapping population developed from a cross between Glycine max and Glycine soja.

Results

Wild and cultivated soybean both contributed alleles towards significant additive large effect QTLs on chromosome 6 and 7 for a longer total root length and root distribution, respectively. Epistatic effect QTLs were also identified for taproot length, average diameter, and root distribution. These root traits will influence the water and nutrient uptake in soybean. Two cell division-related genes (D type cyclin and auxin efflux carrier protein) with insertion/deletion variations might contribute to the shorter root phenotypes observed in G. soja compared with cultivated soybean. Based on the location of the QTLs and sequence information from a second G. soja accession, three genes (slow anion channel associated 1 like, Auxin responsive NEDD8-activating complex and peroxidase), each with a non-synonymous single nucleotide polymorphism mutation were identified, which may also contribute to changes in root architecture in the cultivated soybean. In addition, Apoptosis inhibitor 5-like on chromosome 7 and slow anion channel associated 1-like on chromosome 15 had epistatic interactions for taproot length QTLs in soybean.

Conclusion

Rare alleles from a G. soja accession are expected to enhance our understanding of the genetic components involved in root architecture traits, and could be combined to improve root system and drought adaptation in soybean.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1334-6) contains supplementary material, which is available to authorized users.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号