全文获取类型
| 收费全文 | 2451篇 |
| 免费 | 178篇 |
| 国内免费 | 2篇 |
专业分类
| 2631篇 |
出版年
| 2023年 | 9篇 |
| 2022年 | 20篇 |
| 2021年 | 62篇 |
| 2020年 | 22篇 |
| 2019年 | 37篇 |
| 2018年 | 47篇 |
| 2017年 | 29篇 |
| 2016年 | 67篇 |
| 2015年 | 117篇 |
| 2014年 | 141篇 |
| 2013年 | 170篇 |
| 2012年 | 193篇 |
| 2011年 | 195篇 |
| 2010年 | 120篇 |
| 2009年 | 113篇 |
| 2008年 | 138篇 |
| 2007年 | 150篇 |
| 2006年 | 124篇 |
| 2005年 | 135篇 |
| 2004年 | 108篇 |
| 2003年 | 101篇 |
| 2002年 | 116篇 |
| 2001年 | 23篇 |
| 2000年 | 17篇 |
| 1999年 | 22篇 |
| 1998年 | 18篇 |
| 1997年 | 16篇 |
| 1996年 | 11篇 |
| 1995年 | 18篇 |
| 1994年 | 10篇 |
| 1993年 | 11篇 |
| 1992年 | 9篇 |
| 1991年 | 11篇 |
| 1990年 | 11篇 |
| 1989年 | 13篇 |
| 1987年 | 11篇 |
| 1986年 | 9篇 |
| 1985年 | 9篇 |
| 1983年 | 11篇 |
| 1982年 | 8篇 |
| 1979年 | 10篇 |
| 1978年 | 8篇 |
| 1977年 | 11篇 |
| 1974年 | 9篇 |
| 1973年 | 12篇 |
| 1972年 | 10篇 |
| 1970年 | 10篇 |
| 1968年 | 10篇 |
| 1967年 | 9篇 |
| 1956年 | 9篇 |
排序方式： 共有2631条查询结果，搜索用时 46 毫秒
101.
Mahmood Gholami Malena Erbe Christian G?rke Rudolf Preisinger Annett Weigend Steffen Weigend Henner Simianer 《PloS one》2014,9(4)
Identifying signatures of selection can provide valuable insight about the genes or genomic regions that are or have been under selective pressure, which can lead to a better understanding of genotype-phenotype relationships. A common strategy for selection signature detection is to compare samples from several populations and search for genomic regions with outstanding genetic differentiation. Wright''s fixation index, FST, is a useful index for evaluation of genetic differentiation between populations. The aim of this study was to detect selective signatures between different chicken groups based on SNP-wise FST calculation. A total of 96 individuals of three commercial layer breeds and 14 non-commercial fancy breeds were genotyped with three different 600K SNP-chips. After filtering a total of 1 million SNPs were available for FST calculation. Averages of FST values were calculated for overlapping windows. Comparisons of these were then conducted between commercial egg layers and non-commercial fancy breeds, as well as between white egg layers and brown egg layers. Comparing non-commercial and commercial breeds resulted in the detection of 630 selective signatures, while 656 selective signatures were detected in the comparison between the commercial egg-layer breeds. Annotation of selection signature regions revealed various genes corresponding to productions traits, for which layer breeds were selected. Among them were NCOA1, SREBF2 and RALGAPA1 associated with reproductive traits, broodiness and egg production. Furthermore, several of the detected genes were associated with growth and carcass traits, including POMC, PRKAB2, SPP1, IGF2, CAPN1, TGFb2 and IGFBP2. Our approach demonstrates that including different populations with a specific breeding history can provide a unique opportunity for a better understanding of farm animal selection. 相似文献
102.
103.
Stefan Haffke Barbara Kusterer F. Joachim Fromme Steffen Roux Bernd Hackauf Thomas Miedaner 《Bioenergy Research》2014,7(1):424-429
Winter rye (Secale cereale L.) is becoming increasingly important as substrate for biogas production in Central Europe. Dry matter yield has evolved as a breeding goal comparably important to the traditional grain yield. We analyzed the covariation between both traits and tested other agronomic traits for their correlation to dry matter yield that could be used for prediction of biomass yield. A set of 258 experimental hybrids were tested for dry matter yield harvested at late milk stage and grain yield harvested at full ripening at three to four locations in Germany in 2011 and 2012. We observed a wide range of dry matter yield (10–24 Mg ha?1) and grain yield (6–15 Mg ha?1) among testcross progenies. Genetic variances were significantly (P?<?0.01) different from zero for all traits. High entry-mean heritabilities (0.92–0.94) were found for plant height measurements and moderate heritabilities for grain and dry matter yield (0.52 and 0.49, respectively). Relative efficiencies for selection of dry matter yield estimated by second (EC 51–55) and third (EC 73) measurements of plant height were 1.24 and 0.98 respectively, compared to 0.52 for grain yield. Indirect selection for high dry matter yield using late plant height measurements should be successful. Using grain yield for indirect selection was less effective. The observed broad genetic variation for biomass yield in elite hybrid rye gives good prospects for the use as a resource of renewable energy. Plant height is a good predictor of dry matter yield but should be selected together with improved lodging resistance. 相似文献
104.
Bt-transgenic cotton has proven to be highly efficient in controlling key lepidopteran pests. One concern with the deployment of Bt cotton varieties is the potential proliferation of non-target pests. We previously showed that Bt cotton contained lower concentrations of insecticidal terpenoids as a result of reduced caterpillar damage, which benefited the aphid Aphis gossypii. It is thus important that non-target herbivores are under biological control in Bt cotton fields. The induction or lack of induction of terpenoids could also influence the quality of aphid honeydew, an important food source for beneficial insects. We therefore screened A. gossypii honeydew for cotton terpenoids, that are induced by caterpillars but not the aphids. We then tested the influence of induced insect-resistance of cotton on honeydew nutritional quality for the aphid parasitoid Lysiphlebus testaceipes and the whitefly parasitoid Eretmocerus eremicus. We detected the cotton terpenoids gossypol and hemigossypolone in A. gossypii honeydew. Although a feeding assay demonstrated that gossypol reduced the longevity of both parasitoid species in a non-linear, dose-dependent manner, the honeydew was capable of sustaining parasitoid longevity and reproduction. The level of caterpillar damage to Bt and non-Bt cotton had no impact on the quality of honeydew for the parasitoids.These results indicate that the nutritional quality of honeydew is maintained in Bt cotton and is not influenced by induced insect resistance. 相似文献
105.
Zhong Chen Lahcen Jaafar Davies G. Agyekum Haiyan Xiao Marlene F. Wade R. Ileng Kumaran David L. Spector Gang Bao Matthew H. Porteus William S. Dynan Steffen E. Meiler 《Nucleic acids research》2013,41(19):e182
Engineered nucleases, which incise the genome at predetermined sites, have a number of laboratory and clinical applications. There is, however, a need for better methods for controlled intracellular delivery of nucleases. Here, we demonstrate a method for ligand-mediated delivery of zinc finger nucleases (ZFN) proteins using transferrin receptor-mediated endocytosis. Uptake is rapid and efficient in established mammalian cell lines and in primary cells, including mouse and human hematopoietic stem-progenitor cell populations. In contrast to cDNA expression, ZFN protein levels decline rapidly following internalization, affording better temporal control of nuclease activity. We show that transferrin-mediated ZFN uptake leads to site-specific in situ cleavage of the target locus. Additionally, despite the much shorter duration of ZFN activity, the efficiency of gene correction approaches that seen with cDNA-mediated expression. The approach is flexible and general, with the potential for extension to other targeting ligands and nuclease architectures. 相似文献
106.
Tian Fang Qin Wen Zhang Ran Herzschuh Ulrike Ni Jian Zhang Chengjun Mischke Steffen Cao Xianyong 《Vegetation History and Archaeobotany》2022,31(6):549-558
Vegetation History and Archaeobotany - The terrestrial ecosystem in the Yellow River Source Area (YRSA) is sensitive to climate change and human impacts, although past vegetation change and the... 相似文献
107.
Nicola Hoppmann René Gollan Patrick Belikan Julia Bruttger Jérôme Birkenstock Steffen Jung Enric Esplugues Nir Yogev Richard A Flavell Tobias Bopp Frauke Zipp 《The EMBO journal》2016,35(1):89-101
Multiple sclerosis is the most frequent chronic inflammatory disease of the CNS. The entry and survival of pathogenic T cells in the CNS are crucial for the initiation and persistence of autoimmune neuroinflammation. In this respect, contradictory evidence exists on the role of the most potent type of antigen‐presenting cells, dendritic cells. Applying intravital two‐photon microscopy, we demonstrate the gatekeeper function of CNS professional antigen‐presenting CD11c+ cells, which preferentially interact with Th17 cells. IL‐17 expression correlates with expression of GM‐CSF by T cells and with accumulation of CNS CD11c+ cells. These CD11c+ cells are organized in perivascular clusters, targeted by T cells, and strongly express the inflammatory chemokines Ccl5, Cxcl9, and Cxcl10. Our findings demonstrate a fundamental role of CNS CD11c+ cells in the attraction of pathogenic T cells into and their survival within the CNS. Depletion of CD11c+ cells markedly reduced disease severity due to impaired enrichment of pathogenic T cells within the CNS. 相似文献
108.
109.
Jotham Suez Steffen Porwollik Amir Dagan Alex Marzel Yosef Ilan Schorr Prerak T. Desai Vered Agmon Michael McClelland Galia Rahav Ohad Gal-Mor 《PloS one》2013,8(3)
Human infection with non-typhoidal Salmonella serovars (NTS) infrequently causes invasive systemic disease and bacteremia. To understand better the nature of invasive NTS (iNTS), we studied the gene content and the pathogenicity of bacteremic strains from twelve serovars (Typhimurium, Enteritidis, Choleraesuis, Dublin, Virchow, Newport, Bredeney, Heidelberg, Montevideo, Schwarzengrund, 9,12:l,v:- and Hadar). Comparative genomic hybridization using a Salmonella enterica microarray revealed a core of 3233 genes present in all of the iNTS strains, which include the Salmonella pathogenicity islands 1–5, 9, 13, 14; five fimbrial operons (bcf, csg, stb, sth, sti); three colonization factors (misL, bapA, sinH); and the invasion gene, pagN. In the iNTS variable genome, we identified 16 novel genomic islets; various NTS virulence factors; and six typhoid-associated virulence genes (tcfA, cdtB, hlyE, taiA, STY1413, STY1360), displaying a wider distribution among NTS than was previously known. Characterization of the bacteremic strains in C3H/HeN mice showed clear differences in disease manifestation. Previously unreported characterization of serovars Schwarzengrund, 9,12:l,v:-, Bredeney and Virchow in the mouse model showed low ability to elicit systemic disease, but a profound and elongated shedding of serovars Schwarzengrund and 9,12:l,v:- (as well as Enteritidis and Heidelberg) due to chronic infection of the mouse. Phenotypic comparison in macrophages and epithelial cell lines demonstrated a remarkable intra-serovar variation, but also showed that S. Typhimurium bacteremic strains tend to present lower intracellular growth than gastroenteritis isolates. Collectively, our data demonstrated a common core of virulence genes, which might be required for invasive salmonellosis, but also an impressive degree of genetic and phenotypic heterogeneity, highlighting that bacteremia is a complex phenotype, which cannot be attributed merely to an enhanced invasion or intracellular growth of a particular strain. 相似文献
110.