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   117901篇
  免费   1696篇
  国内免费   839篇
  2023年   222篇
  2022年   364篇
  2021年   921篇
  2020年   532篇
  2019年   590篇
  2018年   12380篇
  2017年   11135篇
  2016年   8244篇
  2015年   1783篇
  2014年   1780篇
  2013年   2338篇
  2012年   6278篇
  2011年   14550篇
  2010年   12955篇
  2009年   9076篇
  2008年   10871篇
  2007年   12374篇
  2006年   1262篇
  2005年   1455篇
  2004年   1720篇
  2003年   1658篇
  2002年   1385篇
  2001年   756篇
  2000年   617篇
  1999年   438篇
  1998年   167篇
  1997年   159篇
  1996年   158篇
  1995年   131篇
  1994年   120篇
  1993年   125篇
  1992年   290篇
  1991年   299篇
  1990年   211篇
  1989年   188篇
  1988年   233篇
  1987年   201篇
  1986年   164篇
  1985年   177篇
  1984年   172篇
  1983年   118篇
  1982年   87篇
  1981年   93篇
  1980年   98篇
  1979年   136篇
  1978年   94篇
  1977年   93篇
  1973年   74篇
  1972年   303篇
  1971年   319篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Plant Molecular Biology - Role of Rubisco Activase in imparting thermotolerance to the photosynthetic apparatus under high temperature. Thus, to improve the grain filling, we need to fine tune...  相似文献   
992.
Key message

Genome wide association studies allowed prediction of 17 candidate genes for association with nitrogen use efficiency. Novel information obtained may provide better understanding of genomic controls underlying germplasm variations for this trait in Indian mustard.

Abstract

Nitrogen use efficiency (NUE) of Indian mustard (Brassica juncea (L.) Czern & Coss.) is low and most breeding efforts to combine NUE with crop performance have not succeeded. Underlying genetics also remain unexplored. We tested 92 SNP-genotyped inbred lines for yield component traits, N uptake efficiency (NUPEFF), nitrogen utilization efficiency (NUTEFF), nitrogen harvest index (NHI) and NUE for two years at two nitrogen doses (No without added N and N100 added @100 kg/ha). Genotypes IC-2489-88, M-633, MCP-632, HUJM 1080, GR-325 and DJ-65 recorded high NUE at low N. These also showed improved crop performance under high N. One determinate mustard genotype DJ-113 DT-3 revealed maximum NUTEFF. Genome wide association studies (GWAS) facilitated recognition of 17 quantitative trait loci (QTLs). Environment specificity was high. B-genome chromosomes (B02, B03, B05, B07 and B08) harbored many useful loci. We also used regional association mapping (RAM) to supplement results from GWAS. Annotation of the genomic regions around peak SNPs helped to predict several gene candidates for root architecture, N uptake, assimilation and remobilization. CAT9 (At1g05940) was consistently envisaged for both NUE and NUPEFF. Major N transporter genes, NRT1.8 and NRT3.1 were predicted for explaining variation for NUTEFF and NUPEFF, respectively. Most significant amino acid transporter gene, AAP1 appeared associated with NUE under limited N conditions. All these candidates were predicted in the regions of high linkage disequilibrium. Sequence information of the predicted candidate genes will permit development of molecular markers to aid breeding for high NUE.

  相似文献   
993.
Plant Cell, Tissue and Organ Culture (PCTOC) - A method for in vitro screening and selection of drought (moisture stress) tolerant mango calli was developed. Poly ethylene glycol (PEG) (Molecular...  相似文献   
994.
Abstract

High-throughput sequencing approach of the 16S rRNA gene was employed to evaluate the bacterial diversity inhabit in melted water, snow, soil, and rocks samples at the lower altitudes of the Laohugou glacial environment. Bioinformatics tools were used to process millions of Illumina reads for alpha and beta diversities of bacterial communities. The diversity indices such as Chao, Shannon, and Simpson were different in the collected samples and solid samples (soil and rocks) showed higher taxon richness and evenness. Taxonomic diversity was unexpectedly higher and the major portion of sequences was assigned to Proteobacteria, Actinobacteria, and Acidobacteria. Higher variation in community structure was reported at the class level and Alphaproteobacteria was dominant. The solid niches were occupied by a higher number of phyla compared with liquid. The physicochemical variables acted as spatial gradients and associated with the bacterial structural communities of the glacial ecosystem. Findings showed that both Proteobacteria and Actinobacteria in solid samples influenced the bacterial community structure in downstream liquid samples. Interestingly, the metagenomic biomarkers were higher in liquid samples. This study provides precious datasets to understand the bacterial community in a better way under the influence of spatial, physical and environmental factors.  相似文献   
995.
996.
997.
998.
999.
1000.
The present study provides the first detailed early embryonic development of the Shalyni barb, Pethia shalynius (Yazdani & Talukdar, 1975), a vulnerable cyprinid fish occurring in streams and lentic waters of Meghalaya, northeast India. Induced spawning by synthetic hormone injection in May 2019 was conducted to a pair of mature female and male P. shalynius under controlled conditions in a well-aerated aquarium. Fertilized eggs were spherical, 0.75–0.80 mm (approx.) in diameter, transparent, unpigmented and non-adhesive. A total of 22 developmental stages could be categorized under seven broad periods, viz. the zygote, cleavage, blastula, gastrula, segmentation, pharyngula and hatchling. The first cleavage occurred at 15 min post fertilization (mpf), followed by blastulation at 01:23 hr post-fertilization (hpf), gastrulation at 04:20 hpf, initial somite formation at 07:00 hpf, and pharyngula period at 19:20 hpf, respectively. Embryos hatched between 26–27 hpf and the newly-hatched larvae ranged 2.2–2.5 mm in total length. For naturally-declining populations of this vulnerable fish species, inferences drawn from the present study will help provide a baseline data for its conservation and management, and aid the research fields of developmental biology, biotechnology, molecular biology as well as taxonomy of this species.  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