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991.
992.
Reproductive biology of Syzygiella rubricaulis (Nees) Steph. (Adelanthaceae,Marchantiophyta), a liverwort disjunctly distributed in high‐altitude Neotropical mountains
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![点击此处可从《Plant biology (Stuttgart, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A. S. Maciel‐Silva E. P. Gaspar F. P. da Conceição N. Dias dos Santos D. Pinheiro da Costa 《Plant biology (Stuttgart, Germany)》2016,18(4):601-608
Syzygiella rubricaulis is a dioecious leafy liverwort disjunctly distributed and restricted to high‐altitude mountains in the Neotropics and the Azores. This study is part of a larger project examining the phylogeography of S. rubricaulis in the Neotropics, and our main goals were to understand its reproductive biology, where sex expression occurs, if vegetative propagules are frequently found, how the sexes are distributed in populations, how frequently sporophytes are formed and what environmental conditions influence sexual expression. S. rubricaulis patches are mostly female, but all patches also contain non sex‐expressing shoots. Out of 42 patches examined, 29 (69%) were sex‐expressing: 25 were unisexual (21 female and four male) and four of mixed sex (two male‐biased and two unbiased). At shoot level, out of 4200 shoots 18% were female and 7% male; among sex‐expressing shoots, 73% were female, representing a sex ratio of 0.8 (female‐biased). We encountered a total of 33 sporophytes in six patches (in Brazil, Venezuela and Ecuador). Leaf regenerants were found in one patch in Mexico. Low rates of sporophytes were likely related to low frequencies of male shoots and large distances between the sexes. As 25% of S. rubricaulis shoots expressed sex (occasionally producing sporophytes), we suggest that short‐distance (and rarely long‐distance) spore dispersal events occur in mountainous areas on a short‐term basis. On a long‐term basis, however, these events likely contribute to dynamic exchanges among populations in the Neotropics. 相似文献
993.
Landscape‐scale spatial abundance distributions discriminate core from random components of boreal lake bacterioplankton
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Juan Pablo Niño‐García Clara Ruiz‐González Paul A. del Giorgio 《Ecology letters》2016,19(12):1506-1515
Aquatic bacterial communities harbour thousands of coexisting taxa. To meet the challenge of discriminating between a ‘core’ and a sporadically occurring ‘random’ component of these communities, we explored the spatial abundance distribution of individual bacterioplankton taxa across 198 boreal lakes and their associated fluvial networks (188 rivers). We found that all taxa could be grouped into four distinct categories based on model statistical distributions (normal like, bimodal, logistic and lognormal). The distribution patterns across lakes and their associated river networks showed that lake communities are composed of a core of taxa whose distribution appears to be linked to in‐lake environmental sorting (normal‐like and bimodal categories), and a large fraction of mostly rare bacteria (94% of all taxa) whose presence appears to be largely random and linked to downstream transport in aquatic networks (logistic and lognormal categories). These rare taxa are thus likely to reflect species sorting at upstream locations, providing a perspective of the conditions prevailing in entire aquatic networks rather than only in lakes. 相似文献
994.
Surface polysaccharides and quorum sensing are involved in the attachment and survival of Xanthomonas albilineans on sugarcane leaves
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Imene Mensi Jean‐Heinrich Daugrois Isabelle Pieretti Daniel Gargani Laura A. Fleites Julie Noell Francois Bonnot Dean W. Gabriel Philippe Rott 《Molecular Plant Pathology》2016,17(2):236-246
Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is a bacterial plant pathogen that is mainly spread by infected cuttings and contaminated harvesting tools. However, some strains of this pathogen are known to be spread by aerial means and are able to colonize the phyllosphere of sugarcane before entering the host plant and causing disease. The objective of this study was to identify the molecular factors involved in the survival or growth of X. albilineans on sugarcane leaves. We developed a bioassay to test for the attachment of X. albilineans on sugarcane leaves using tissue‐cultured plantlets grown in vitro. Six mutants of strain XaFL07‐1 affected in surface polysaccharide production completely lost their capacity to survive on the sugarcane leaf surface. These mutants produced more biofilm in vitro and accumulated more cellular poly‐β‐hydroxybutyrate than the wild‐type strain. A mutant affected in the production of small molecules (including potential biosurfactants) synthesized by non‐ribosomal peptide synthetases (NRPSs) attached to the sugarcane leaves as well as the wild‐type strain. Surprisingly, the attachment of bacteria on sugarcane leaves varied among mutants of the rpf gene cluster involved in bacterial quorum sensing. Therefore, quorum sensing may affect polysaccharide production, or both polysaccharides and quorum sensing may be involved in the survival or growth of X. albilineans on sugarcane leaves. 相似文献
995.
Manuel J. Steinbauer Richard Field John‐Arvid Grytnes Panayiotis Trigas Claudine Ah‐Peng Fabio Attorre H. John B. Birks Paulo A. V. Borges Pedro Cardoso Chang‐Hung Chou Michele De Sanctis Miguel M. de Sequeira Maria C. Duarte Rui B. Elias José María Fernández‐Palacios Rosalina Gabriel Roy E. Gereau Rosemary G. Gillespie Josef Greimler David E. V. Harter Tsurng‐Juhn Huang Severin D. H. Irl Daniel Jeanmonod Anke Jentsch Alistair S. Jump Christoph Kueffer Sandra Nogué Rüdiger Otto Jonathan Price Maria M. Romeiras Dominique Strasberg Tod Stuessy Jens‐Christian Svenning Ole R. Vetaas Carl Beierkuhnlein 《Global Ecology and Biogeography》2016,25(9):1097-1107
996.
997.
Phenyl 2‐pyridyl ketoxime induces cellular senescence‐like alterations via nitric oxide production in human diploid fibroblasts
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Kyeong Eun Yang Hyun‐Jin Jang In‐Hu Hwang Young‐Ho Chung Jong‐Soon Choi Tae‐Hoon Lee Yun‐Jo Chung Min‐Seung Lee Mi Young Lee Eui‐Ju Yeo Ik‐Soon Jang 《Aging cell》2016,15(2):245-255
Phenyl‐2‐pyridyl ketoxime (PPKO) was found to be one of the small molecules enriched in the extracellular matrix of near‐senescent human diploid fibroblasts (HDFs). Treatment of young HDFs with PPKO reduced the viability of young HDFs in a dose‐ and time‐dependent manner and resulted in senescence‐associated β‐galactosidase (SA‐β‐gal) staining and G2/M cell cycle arrest. In addition, the levels of some senescence‐associated proteins, such as phosphorylated ERK1/2, caveolin‐1, p53, p16ink4a, and p21waf1, were elevated in PPKO‐treated cells. To monitor the effect of PPKO on cell stress responses, reactive oxygen species (ROS) production was examined by flow cytometry. After PPKO treatment, ROS levels transiently increased at 30 min but then returned to baseline at 60 min. The levels of some antioxidant enzymes, such as catalase, peroxiredoxin II and glutathione peroxidase I, were transiently induced by PPKO treatment. SOD II levels increased gradually, whereas the SOD I and III levels were biphasic during the experimental periods after PPKO treatment. Cellular senescence induced by PPKO was suppressed by chemical antioxidants, such as N‐acetylcysteine, 2,2,6,6‐tetramethylpiperidinyloxy, and L‐buthionine‐(S,R)‐sulfoximine. Furthermore, PPKO increased nitric oxide (NO) production via inducible NO synthase (iNOS) in HDFs. In the presence of NOS inhibitors, such as L‐NG‐nitroarginine methyl ester and L‐NG‐monomethylarginine, PPKO‐induced transient NO production and SA‐β‐gal staining were abrogated. Taken together, these results suggest that PPKO induces cellular senescence in association with transient ROS and NO production and the subsequent induction of senescence‐associated proteins . 相似文献
998.
One of the greatest unresolved questions in aging biology is determining the genetic basis of interspecies longevity variation. Gene duplication is often the key to understanding the origin and evolution of important Eutherian phenotypes. We systematically identified longevity‐associated genes in model organisms that duplicated throughout Eutherian evolution. Longevity‐associated gene families have a marginally significantly higher rate of duplication compared to non‐longevity‐associated gene families. Anti‐longevity‐associated gene families have significantly increased rate of duplication compared to pro‐longevity gene families and are enriched in neurodegenerative disease categories. Conversely, duplicated pro‐longevity‐associated gene families are enriched in cell cycle genes. There is a cluster of longevity‐associated gene families that expanded solely in long‐lived species that is significantly enriched in pathways relating to 3‐UTR‐mediated translational regulation, metabolism of proteins and gene expression, pathways that have the potential to affect longevity. The identification of a gene cluster that duplicated solely in long‐lived species involved in such fundamental processes provides a promising avenue for further exploration of Eutherian longevity evolution. 相似文献
999.
Absence of Tau triggers age‐dependent sciatic nerve morphofunctional deficits and motor impairment
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Sofia Lopes André Lopes Vítor Pinto Marco R. Guimarães Vanessa Morais Sardinha Sara Duarte‐Silva Sara Pinheiro João Pizarro João Filipe Oliveira Nuno Sousa Hugo Leite‐Almeida Ioannis Sotiropoulos 《Aging cell》2016,15(2):208-216
Dementia is the cardinal feature of Alzheimer's disease (AD), yet the clinical symptoms of this disorder also include a marked loss of motor function. Tau abnormal hyperphosphorylation and malfunction are well‐established key events in AD neuropathology but the impact of the loss of normal Tau function in neuronal degeneration and subsequent behavioral deficits is still debated. While Tau reduction has been increasingly suggested as therapeutic strategy against neurodegeneration, particularly in AD, there is controversial evidence about whether loss of Tau progressively impacts on motor function arguing about damage of CNS motor components. Using a variety of motor‐related tests, we herein provide evidence of an age‐dependent motor impairment in Tau?/? animals that is accompanied by ultrastructural and functional impairments of the efferent fibers that convey motor‐related information. Specifically, we show that the sciatic nerve of old (17–22‐months) Tau?/? mice displays increased degenerating myelinated fibers and diminished conduction properties, as compared to age‐matched wild‐type (Tau+/+) littermates and younger (4–6 months) Tau?/? and Tau+/+ mice. In addition, the sciatic nerves of Tau?/? mice exhibit a progressive hypomyelination (assessed by g‐ratio) specifically affecting large‐diameter, motor‐related axons in old animals. These findings suggest that loss of Tau protein may progressively impact on peripheral motor system. 相似文献
1000.
Loic Verlingue Aurélien Dugourd Gautier Stoll Emmanuel Barillot Laurence Calzone Arturo Londoño‐Vallejo 《Aging cell》2016,15(6):1018-1026
Altered molecular responses to insulin and growth factors (GF) are responsible for late‐life shortening diseases such as type‐2 diabetes mellitus (T2DM) and cancers. We have built a network of the signaling pathways that control S‐phase entry and a specific type of senescence called geroconversion. We have translated this network into a Boolean model to study possible cell phenotype outcomes under diverse molecular signaling conditions. In the context of insulin resistance, the model was able to reproduce the variations of the senescence level observed in tissues related to T2DM's main morbidity and mortality. Furthermore, by calibrating the pharmacodynamics of mTOR inhibitors, we have been able to reproduce the dose‐dependent effect of rapamycin on liver degeneration and lifespan expansion in wild‐type and HER2–neu mice. Using the model, we have finally performed an in silico prospective screen of the risk–benefit ratio of rapamycin dosage for healthy lifespan expansion strategies. We present here a comprehensive prognostic and predictive systems biology tool for human aging. 相似文献