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   20029篇
  免费   1114篇
  国内免费   27篇
  2023年   163篇
  2022年   393篇
  2021年   735篇
  2020年   430篇
  2019年   452篇
  2018年   668篇
  2017年   626篇
  2016年   821篇
  2015年   939篇
  2014年   1178篇
  2013年   1615篇
  2012年   1699篇
  2011年   1506篇
  2010年   887篇
  2009年   770篇
  2008年   906篇
  2007年   885篇
  2006年   748篇
  2005年   670篇
  2004年   550篇
  2003年   477篇
  2002年   412篇
  2001年   347篇
  2000年   327篇
  1999年   287篇
  1998年   118篇
  1997年   87篇
  1996年   97篇
  1995年   92篇
  1994年   64篇
  1993年   69篇
  1992年   182篇
  1991年   176篇
  1990年   139篇
  1989年   119篇
  1988年   154篇
  1987年   136篇
  1986年   108篇
  1985年   108篇
  1984年   103篇
  1983年   61篇
  1982年   55篇
  1981年   61篇
  1980年   58篇
  1979年   81篇
  1978年   57篇
  1977年   59篇
  1975年   51篇
  1973年   49篇
  1972年   48篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
992.
Plant and Soil - Plant growth promoting bacteria (PGPB) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase can play an important role in abiotic stress tolerance in plants, particularly...  相似文献   
993.
Journal of Ichthyology - The present study reports the first record of the rearfin flying fish, Cypselurus opisthopus (Bleeker, 1865), in the south-eastern Arabian Sea based on a single specimen...  相似文献   
994.
Plant Cell, Tissue and Organ Culture (PCTOC) - Cowpea (Vigna unguiculata (L.) Walp.) is a warm-season legume crop which is widely grown by resource-poor small and marginal farmers of Sub-Saharan...  相似文献   
995.

The placental tissue of the highly pungent chilli cultivar, Capsicum chinense Jacq. cv. ‘Umorok’, is used as explants for callus induction. Callus cultures were subcultured after every 32 days and growth curves for a period of six consecutive growth cycles were studied till a stable capsaicinoids producing callus cultures were obtained. The capsaicinoids content in placental tissue explants decreased gradually during the first 2 months of culture as the explants dedifferentiated to form friable callus while the biomass and capsaicinoid content did not show much change in the subsequent growth cycles. The maximum callus biomass of 7.8 g freshweight (FW) or 0.56 g dry weight (DW) per culture were obtained on the 24th day of every growth cycle and the maximum average capsaicinoids content (1.6 mg g?1 FW capsaicin and 0.78 mg g?1 FW dihydrocapsaicin) were obtained on the 20th day of every growth cycle. To investigate the underlying dynamics for capsaicinoid biosynthesis during callus formation, comparative gene expression analysis of the genes involved in capsaicinoid biosynthesis pathway were also studied by qRT-PCR analysis. When compared with placental tissue, all the studied genes showed reduced expression during callus formation, especially putative aminotransferase (pAMT) and pungent gene 1 (Pun1), which were extensively down regulated from the 3rd month onwards in the callus cultures. Therefore, the present study revealed that the down-regulated expression of mainly two putative genes in capsaicinoid biosynthetic pathway (pAMT and Pun1) resulted in lower accumulation of capsaicinoids in callus cultures compared to placental tissues of fruits.

  相似文献   
996.
Molecular Biology Reports - Mulberry (Morus alba L.) is the sole food source for the mulberry silkworm, Bombyx mori and therefore important for sericulture industry. Different abiotic stress...  相似文献   
997.
Length–weight relationships (LWRs) were determined for seven riverine fish species from the river Ganga, India. Specimens were collected on a bi‐monthly basis from April 2017 to December 2018 using gill nets (mesh size 22–34 mm), cast nets (mesh size 16 mm) and bag nets (mesh size 14–22 mm). Total length was measured to the nearest 0.1 cm using a digital caliper and weight was recorded to the nearest 0.01 g on an electronic balance. From estimated length–weight relationships, the values for parameter “a” ranged from 0.004 (Bregmaceros mcclellandi and Setipinna tenuifilis) to 0.014 (Brachirus pan). Likewise, the values for the parameter “b” of the equation ranged from 2.958 (Bagarius bagarius) to 3.124 (Bregmaceros mcclellandi) and r2 from 0.978 (Gonialosa manmina) to 0.996 (Brachirus pan).  相似文献   
998.
The present study explains the intraspecific variation in Indian Hill trout (Barilius bendelisis) on the basis of image based truss network system and D‐loop region of mtDNA. A total of 210 samples were collected from three different rivers (Teesta, Kameng and Myntudu River) of North East India in Indo‐Burma Biodiversity Hotspot. By using the software applications (tpsDig version 2.1 and PAST), a total of 25 morphometric measurements were generated from 10 landmarks. The Analysis of Variance (ANOVA), Factor Analysis (FA) and Discriminate Function Analysis (DFA) showed, out of the total variations, factor 1 explained 46.74% while factor 2 and factor 3 explained 27.14% and 11.92%, respectively. Using these variables 83.33% of the cross‐validated specimens were classified into distinct groups. Analysis of Molecular Variance (AMOVA) and pairwise Fst value for D‐loop region of mtDNA also showed high to medium level of genetic variation among the stocks and within the stocks. We conclude that the observed discrete stocks might be the result of changing environmental conditions in different rivers of the hotspot as the rivers are present at different altitudinal labels. It is also believed that the variation might be due to the construction of barrages across the river which hinder the mixing among the stocks.  相似文献   
999.
Disease associated chromosomal rearrangements often have break points located within disease causing genes or in their vicinity. The purpose of this study is to characterize a balanced reciprocal translocation in a girl with intellectual disability and seizures by positional cloning and whole genome sequencing. The translocation was identification by G- banding and confirmed by WCP FISH. Fine mapping using BAC clones and whole genome sequencing using Oxford nanopore long read sequencing technology for a 1.46 X coverage of the genome was done. The positional cloning showed split signals with BAC RP11-943 J20. Long read sequencing analysis of chimeric reads carrying parts of chromosomes X and 20 helped to identify the breakpoints to be in intron 2 of ARHGEF9 gene on Xp11.1 and on 20p13 between RASSF2 and SLC23A2 genes. This is the first report of translocation which successfully delineated to single base resolution using Nanopore sequencing. The genotype-phenotype correlation is discussed.  相似文献   
1000.
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