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   10228篇
  免费   705篇
  国内免费   8篇
  2024年   15篇
  2023年   77篇
  2022年   271篇
  2021年   405篇
  2020年   209篇
  2019年   243篇
  2018年   292篇
  2017年   214篇
  2016年   376篇
  2015年   593篇
  2014年   635篇
  2013年   748篇
  2012年   885篇
  2011年   815篇
  2010年   493篇
  2009年   470篇
  2008年   619篇
  2007年   572篇
  2006年   495篇
  2005年   417篇
  2004年   376篇
  2003年   396篇
  2002年   352篇
  2001年   75篇
  2000年   51篇
  1999年   93篇
  1998年   78篇
  1997年   63篇
  1996年   34篇
  1995年   55篇
  1994年   49篇
  1993年   47篇
  1992年   39篇
  1991年   29篇
  1990年   16篇
  1989年   27篇
  1988年   24篇
  1987年   17篇
  1986年   19篇
  1985年   18篇
  1984年   15篇
  1983年   16篇
  1982年   20篇
  1981年   17篇
  1980年   15篇
  1979年   13篇
  1978年   15篇
  1977年   12篇
  1975年   9篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
232.
Molecular Biology Reports - Molecular detection of Giardia duodenalis by polymerase chain reaction (PCR) is difficult in faecal samples due to inhibitors that contaminate DNA preparations, or due...  相似文献   
233.
Molecular Biology Reports - Introns experience lesser selection pressure, thus are liable for higher polymorphism. Intron Length Polymorphic (ILP) markers designed from exon-flanking introns...  相似文献   
234.
Background and AimsPlants depend fundamentally on establishment from seed. However, protocols in trait-based ecology currently estimate seed size but not seed number. This can be rectified. For annuals, seed number should simply be a positive function of vegetative biomass and a negative function of seed size.MethodsUsing published values of comparative seed number as the ‘gold standard’ and a large functional database, comparative seed yield and number per plant and per m2 were predicted by multiple regression. Subsequently, ecological variation in each was explored for English and Spanish habitats, newly calculated C-S-R strategies and changed abundance in the British flora.Key ResultsAs predicted, comparative seed mass yield per plant was consistently a positive function of plant size and competitive ability, and largely independent of seed size. Regressions estimating comparative seed number included, additionally, seed size as a negative function. Relationships differed numerically between regions, habitats and C-S-R strategies. Moreover, some species differed in life history over their geographical range. Comparative seed yield per m2 was positively correlated with FAO crop yield, and increasing British annuals produced numerous seeds. Nevertheless, predicted values must be viewed as comparative rather than absolute: they varied according to the ‘gold standard’ predictor used. Moreover, regressions estimating comparative seed yield per m2 achieved low precision.ConclusionsFor the first time, estimates of comparative seed yield and number for >800 annuals and their predictor equations have been produced and the ecological importance of these regenerative traits has been illustrated. ‘Regenerative trait-based ecology’ remains in its infancy, with work needed on determinate vs. indeterminate flowering (‘bet-hedging’), C-S-R methodologies, phylogeny, comparative seed yield per m2 and changing life history. Nevertheless, this has been a positive start and readers are invited to use estimates for >800 annuals, in the Supplementary data, to help advance ‘regenerative trait-based ecology’ to the next level.  相似文献   
235.
Neurochemical Research - Post-translational modification (PTMs) of proteins by ubiquitin and ubiquitin-like modifiers such as interferon-stimulated gene 15 (ISG15) and small ubiquitin-related...  相似文献   
236.
The thyroid hormone receptors (TRs) mediate thyroid hormone (T3)-dependent gene expression. The nuclear import and export signals that direct TR shuttling are well characterized, but little is known about factors modulating nuclear retention. We used fluorescence-based nucleocytoplasmic scoring and fluorescence recovery after photobleaching in transfected cells to investigate whether Mediator subunits MED1 and MED13 play a role in nuclear retention of TR. When MED1 was overexpressed, there was a striking shift towards a greater nuclear localization of TRβ1 and the oncoprotein v-ErbA, subtypes with cytosolic populations at steady-state, and TRβ1 intranuclear mobility was reduced. For TRα1, there was no observable change in its predominantly nuclear distribution pattern or mobility. Consistent with a role for MED1 in nuclear retention, the cytosolic TRα1 and TRβ1 population were significantly greater in MED1−/− cells, compared with MED1+/+ cells. Exposure to T3 and epidermal growth factor, which induces MED1 phosphorylation, also altered TR intranuclear dynamics. Overexpression of miR-208a, which downregulates MED13, led to a more cytosolic distribution of nuclear-localized TRα1; however, overexpression of MED13 had no effect on TRβ1 localization. The known binding site of MED1 overlaps with a transactivation domain and nuclear export signal in helix 12 of TR's ligand-binding domain (LBD). Coimmunoprecipitation assays demonstrated that TR's LBD interacts directly with exportins 5 and 7, suggesting that binding of exportins and MED1 to TR may be mutually exclusive. Collectively, our data provide evidence that MED1 promotes nuclear retention of TR, and highlight the dual functionality of helix 12 in TR transactivation and nuclear export.  相似文献   
237.
Plant Molecular Biology Reporter - Manihot esculenta Crantz is originally from the Amazon region of Brazil, which has the highest genetic diversity. Due to the wide adaptation of cassava to the...  相似文献   
238.
239.
Applied Entomology and Zoology - The efficacy of mating disruption with Isonet®-T at the rate of 30, 45 or 60 g a.i. ha –1 of sex pheromone to control Tuta absoluta (Meyrick)...  相似文献   
240.
Rational embellishment of self-assembling two-dimensional (2D) proteins make it possible to build 3D nanomaterials with novel catalytic, optoelectronic and mechanical properties. However, introducing multiple sites of embellishment into 2D protein arrays without affecting the self-assembly is challenging, limiting the ability to program in additional functionality and new 3D configurations. Here we introduce two orthogonal covalent linkages at multiple sites in a 2D crystalline-forming protein without affecting its self-assembly. We first engineered the surface-layer protein SbsB from Geobacillus stearothermophilus pV72/p2 to display isopeptide bond-forming protein conjugation pairs, SpyTag or SnoopTag, at four positions spaced 5.7-10.5 nm apart laterally and 3 nm axially. The C-terminal and two newly-identified locations within SbsB monomer accommodated the short SpyTag or SnoopTag peptide tags without affecting the 2D lattice structure. Introducing tags at distinct locations enabled orthogonal and covalent binding of SpyCatcher- or SnoopCatcher-protein fusions to micron-sized 2D nanosheets. By introducing different types of bifunctional cross-linkers, the dual-functionalized nanosheets were programmed to self-assemble into different 3D stacks, all of which retain their nanoscale order. Thus, our work creates a modular protein platform that is easy to program to create dual-functionalized 2D and lamellar 3D nanomaterials with new catalytic, optoelectronic, and mechanical properties.  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