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   119篇
  免费   2篇
  国内免费   1篇
林业   11篇
农学   8篇
基础科学   5篇
  22篇
综合类   19篇
农作物   14篇
水产渔业   3篇
畜牧兽医   22篇
植物保护   18篇
  2023年   2篇
  2022年   2篇
  2021年   4篇
  2020年   1篇
  2019年   3篇
  2018年   5篇
  2017年   3篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   9篇
  2012年   6篇
  2011年   5篇
  2010年   4篇
  2009年   2篇
  2008年   5篇
  2007年   3篇
  2006年   9篇
  2005年   5篇
  2004年   3篇
  2003年   5篇
  2002年   3篇
  2001年   3篇
  2000年   5篇
  1999年   1篇
  1995年   3篇
  1993年   2篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   3篇
  1987年   2篇
  1985年   2篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
  1968年   1篇
排序方式: 共有122条查询结果,搜索用时 99 毫秒
1.
Summary The effect of irrigation on tillering and tiller mortality in varieties of wheat (Triticum aestivum and T. durum), triticale and barley was studied under field conditions. Low temperature in the early stages of growth promoted production of tillers whereas increase in temperature during extension growth phase increased tiller mortality. More than 1000 tillers m–2 were produced with five irrigations but 40% or more died. With limited water availability tiller production was reduced but so was their mortality. Grain yield in wheat and triticale was positively correlated with productive tillers and negatively correlated with the maximum number of tillers produced in wheat and barley grown under limited irrigation conditions. Varieties with a capacity to produce fewer tillers were identified. Some of them proved more stable in yield. No correlation was found between tiller number and grain yield in the frequently irrigated treatment.  相似文献   
2.
3.
Summary Forty strains of mungbeans, including all of the entries in the 1st and 2nd International Mungbean Nurseries (IMN), were grown in plant growth chambers in photoperiods of 12, 13, 14, 15, and 16 hours and mean temperatures of 18, 23, and 28°C. Results show that (1) mungbean strains differ in their flowering response to photoperiod and to mean temperature; (2) increasing the photoperiod of reducing the mean temperature delayed flowering, the amount of delay varied with the strain: (3) variations in mean temperature may alter the effect of the photoperiod on flowering in particular strains. Twenty-five strains which flowered in all photoperiod-temperature treatments could be divided into four groups, each group being successively later in flowering. The remaining 15 strains could be divided into four groups, according to their failure to flower within 105 days in specific photoperiod-temperature treatments. Flowering response in the growth chamber is useful in explaining flowering response in the 2nd IMN at three locations varying from 14°N to 49°N latitude.Contribution No 7516 from the Missouri Agricultural Experiment Station.  相似文献   
4.

Introduction   

Wood quality is an important criterion in the selection of superior genotypes when breeding for solid wood.  相似文献   
5.
Earthquake prediction: a physical basis   总被引:13,自引:0,他引:13  
  相似文献   
6.
A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathology, revealed a conserved core proteome of about 6200 genes in large syntenic polycistronic gene clusters. Many species-specific genes, especially large surface antigen families, occur at nonsyntenic chromosome-internal and subtelomeric regions. Retroelements, structural RNAs, and gene family expansion are often associated with syntenic discontinuities that-along with gene divergence, acquisition and loss, and rearrangement within the syntenic regions-have shaped the genomes of each parasite. Contrary to recent reports, our analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont.  相似文献   
7.
8.
We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.  相似文献   
9.
10.
The use of indicators in soil monitoring schemes to detect changes in soil quality is receiving increased attention, particularly the application of soil biological methods. However, to date, the ability to compare information from different laboratories applying soil microbiological techniques in broad-scale monitoring has rarely been taken into account. This study aimed to assess the consistency and repeatability of two techniques that are being evaluated for use as microbiological indicators of soil quality: multi-enzyme activity assay and multiple substrate-induced respiration (MSIR). Data were tested for intrinsic (within-assay plate) variation, inter-laboratory repeatability (geometric mean regression and correlation coefficient) and land-use discrimination (principal components analysis). Intrinsic variation was large for both assays suggesting that high replicate numbers are required. Inter-laboratory repeatability showed diverging patterns for the enzyme assay and MSIR. Discrimination of soils was significant for both techniques with relatively consistent patterns; however, combined laboratory discrimination analyses for each technique showed inconsistent correspondence between the laboratories. These issues could be addressed through the adoption of reliable analytical standards for biological methods along with adequate replication. However, until the former is addressed, dispersed analyses are not currently advisable for monitoring schemes.  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