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   36135篇
  免费   3142篇
  国内免费   2653篇
  2024年   63篇
  2023年   343篇
  2022年   771篇
  2021年   1351篇
  2020年   1121篇
  2019年   1324篇
  2018年   1360篇
  2017年   1062篇
  2016年   1417篇
  2015年   2127篇
  2014年   2473篇
  2013年   2708篇
  2012年   3107篇
  2011年   2864篇
  2010年   1943篇
  2009年   1653篇
  2008年   1928篇
  2007年   1776篇
  2006年   1621篇
  2005年   1422篇
  2004年   1229篇
  2003年   1268篇
  2002年   1055篇
  2001年   768篇
  2000年   665篇
  1999年   588篇
  1998年   335篇
  1997年   273篇
  1996年   232篇
  1995年   209篇
  1994年   224篇
  1993年   149篇
  1992年   288篇
  1991年   241篇
  1990年   212篇
  1989年   224篇
  1988年   170篇
  1987年   147篇
  1986年   154篇
  1985年   138篇
  1984年   84篇
  1983年   87篇
  1982年   59篇
  1981年   42篇
  1979年   55篇
  1977年   78篇
  1976年   49篇
  1975年   44篇
  1974年   56篇
  1973年   42篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
As a member of the low-density lipoprotein receptor (LDLR) superfamily, vitellogenin (Vg) receptor (VgR) is responsible for the uptake of Vg into developing oocytes and is a potential target for pest control. Here, a full-length VgR complementary DNA (named as CsVgR) was isolated and characterized in the rice stem borer, Chilo suppressalis. The composite CsVgR gene contained an open reading frame of 5,484 bp encoding a protein of 1,827 amino acid residues. Structural analysis revealed that CsVgR contained two ligand-binding domains (LBDs) with four Class A (LDLRA) repeats in LBD1 and seven in LBD2, which was structurally different from most non-Lepidopteran insect VgRs having five repeats in LBD1 and eight in LBD2. The developmental expression analysis showed that CsVgR messenger RNA expression was first detectable in 3-day-old pupae, sharply increased in newly emerged female adults, and reached a peak in 2-day-old female adults. Consistent with most other insects VgRs, CsVgR was exclusively expressed in the ovary. Notably, injection of dsCsVgR into late pupae resulted in fewer follicles in the ovarioles as well as reduced fecundity, suggesting a critical role of CsVgR in female reproduction. These results may contribute to the development of RNA interference-mediated disruption of reproduction as a control strategy of C. suppressalis.  相似文献   
942.
In order to place a newly discovered species Antigracilus costatus gen. sp. n. from the Lower Cretaceous Yixian Formation (China) and to assess previously unplaced fossil taxa, we investigated the relationships of extant and extinct lineages of Histeridae based on three data sets: (i) 69 morphological characters belonging to 48 taxa (representing all 11 subfamilies and 15 of 17 tribes of modern Histeridae); (ii) partitioned alignment of 6030 bp from downloaded nucleotide sequences (28S, CAD, COI, 18S) of 50 taxa (representing 10 subfamilies and 15 of 17 tribes of modern Histeridae); and (iii) a combined morphological and molecular dataset for 75 taxa. Phylogenetic analyses of the morphology and combined matrices recovered the new Lower Cretaceous taxon as a sister group to remaining Histeridae and it is placed in †Antigracilinae subfam. n. †Antigracilinae constitutes the earliest record of Histeridae from the Lower Cretaceous Yixian Formation (∼125 Myr), backdating the minimum age of the family by 25 Myr from the earliest Cenomanian (~99 Myr) to the Barremian of the Cretaceous Period. Our molecular phylogeny supports Histeridae to be divided into seven different clades, with currently recognised subfamilies Abraeinae (sensu lato), Saprininae, Chlamydopsinae, and Histerinae (sensu lato) recovered as monophyletic, while Dendrophilinae, Onthophilinae, and Tribalinae are polyphyletic taxa. The Burmese amber species †Pantostictus burmanicus Poinar & Brown is placed as a sister group to the tribe Plegaderini (Abraeinae) and was assigned as a new tribe Pantostictini trib. n. Both molecular and combined phylogenies recovered the subfamilies Trypanaeinae and Trypeticinae deeply within the subfamily Abraeinae (sensu lato), and they are downgraded into Trypanaeini stat. n. and Trypeticini stat. n.  相似文献   
943.
Molecular Biology Reports - TBI is the main cause of death and disability in individuals aged 1–45 in Western countries. One of the main challenges of TBI at present is the lack of specific...  相似文献   
944.
Dong  Xin  Wang  Shaoyu  Xu  Lian  Lin  Juan  Xu  Xinqi 《Molecular biology reports》2020,47(2):967-975
Molecular Biology Reports - Penicillin V is a bacteriolytic β-lactam antibiotic drug. In the present work, we investigated the inhibitory effect of Penicillin V on the activity of mushroom...  相似文献   
945.
Yao  Hanhan  Liu  Chenshan  Lin  Dehai  Liu  Sheng  Lin  Zhihua  Dong  Yinghui 《Molecular biology reports》2020,47(2):1257-1264
Molecular Biology Reports - Leucine aminopeptidase 3 (LAP3) is an important proteolytic enzyme that catalyzes the hydrolysis of leucine residues from the amino termini of protein or peptide...  相似文献   
946.
Zhang  Huan  Sun  Gaigai  Lin  Zhihua  Yao  Hanhan  Dong  Yinghui 《Molecular biology reports》2020,47(12):9579-9593
Molecular Biology Reports - High ammonia can inhibit the survival and growth, and even cause mortality of razor clam (S. constricta). The accumulation of ammonia to lethal concentrations in some...  相似文献   
947.
Molecular Biology Reports - Serotoninergic system is one of the most important neurotransmission systems investigated in the field of psychiatry. Extensive evidence reveals how alterations of this...  相似文献   
948.
Yang  Tianran  Li  Wanjie  Li  Yi  Liu  Xin  Yang  Dong 《Mycopathologia》2020,185(3):439-454
Mycopathologia - Candida albicans is an important opportunistic fungal pathogen, and its pathogenicity is closely related to its ability to form hyphae. ESCRT system was initially discovered as a...  相似文献   
949.
王吉成  李洁  丁天波  褚栋 《昆虫学报》2020,63(2):159-165
【目的】本研究旨在建立TaqMan实时荧光定量PCR(TaqMan RT-qPCR)技术,快速检测单头烟粉虱Bemisia tabaci体内的番茄褪绿病毒(tomato chlorosis virus,ToCV)。【方法】根据ToCV外壳蛋白保守序列设计了1对特异性引物和1条TaqMan探针,建立了TaqMan RT-qPCR方法;与常规PCR检测进行比较,检测该方法的灵敏度与特异性;并应用该方法对单头烟粉虱成虫体内ToCV进行了快速检测。【结果】本研究构建的TaqMan RT-qPCR检测ToCV的标准曲线,其循环阈值(Ct值)与模板浓度具有良好的线性关系,扩增效率为98%。该方法对ToCV的最低检测浓度为8.3×10 copies/μL,灵敏度是常规RT-PCR的1000倍。该方法与田间番茄两种重要病毒番茄黄化曲叶病毒(tomato yellow leaf curl virus,TYLCV)和番茄斑萎病毒(tomato spotted wilt virus,TSWV)检测无交叉反应。单头烟粉虱成虫ToCV检测结果表明,温室内ToCV侵染植株上烟粉虱携毒率为100%,田间烟粉虱的携毒率为30%。【结论】本研究建立的TaqMan RT-qPCR检测方法,可快速有效检测单头烟粉虱体内ToCV携毒情况,为该病毒病的防控提供了技术支撑。  相似文献   
950.
Li  Yanteng  Lv  Wenying  Cheng  Gang  Wang  Shuwei  Liu  Bangxin  Zhao  Hulin  Wang  Hongwei  Zhang  Leiming  Dong  Chao  Zhang  Jianning 《Neurochemical research》2020,45(11):2723-2731
Neurochemical Research - Blast-induced traumatic brain injury (bTBI) is a leading cause of disability and mortality in soldiers during the conflicts in Iraq and Afghanistan. Although substantial...  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