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   604篇
  免费   22篇
  国内免费   2篇
  2023年   4篇
  2022年   23篇
  2021年   35篇
  2020年   23篇
  2019年   33篇
  2018年   28篇
  2017年   19篇
  2016年   24篇
  2015年   27篇
  2014年   33篇
  2013年   56篇
  2012年   53篇
  2011年   35篇
  2010年   23篇
  2009年   19篇
  2008年   28篇
  2007年   23篇
  2006年   27篇
  2005年   30篇
  2004年   20篇
  2003年   18篇
  2002年   11篇
  2001年   3篇
  2000年   3篇
  1999年   1篇
  1998年   4篇
  1985年   1篇
  1983年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
  1968年   2篇
  1967年   1篇
  1966年   2篇
  1964年   1篇
排序方式: 共有628条查询结果,搜索用时 15 毫秒
1.
2.
Résumé Les auteurs décriventPseudoscymnus simmondsi, espèce nouvelle deCoccinellidae prédatrice dePinnaspis strachani (Cooley) surFicus palmata au Pakistan occidental. Les autres espèces du genre sont connues seulement de l'Extrême-Orient.

This research has been financed in part by a grant made by the United States Department of Agriculture, Agricultural Research Service.  相似文献   
3.
Rafiq Ahmad 《BioControl》1978,23(2):161-162
Hyperodes bonariensis Kuschel underwent ovarial diapause from March to August in the Bariloche area in Argentina. Feeding on germinating seedlings ofTriticum aestivum L. andPoa annua L. in continuous dark induced the weevil for oviposition in 24 and 32 days, respectively. Breeding techniques are described forH. bonariensis and its parasitePatasson atomarius (Brethes).  相似文献   
4.
Salinity induced changes in the reproductive physiology of wheat plants   总被引:2,自引:0,他引:2  
The effect of salinity on reproductive physiology of wheat wasinvestigated. One set of wheat plants was subjected to increasingsalt levels up to a certain concentration, whereas another setwas given the same concentration in a single application. Theformer was called "gradual" and latter "shock" treatment. Theireffects on pollen viability, germination and activity of starchsynthetase were studied. Gradual treatment seemed to reducethe toxic effects of salts on the viability of pollen grainsand their germination. Seeds obtained from the two sets weregerminated in the same salinities in which their plants hadbeen growing, and the results were compared with those of seedsobtained from control plants growing in a non-saline medium.The seeds of plants from the gradual treatment were better suitedfor germination on a saline medium than those from the shocktreatment or the control group. Salt treatment also increasedthe activity of starch synthetase at the midmilky stage in developinggrains. This phenomenon was considered essential for synthesisof starch in a saline environment. The increase in Na+ and Cl and decrease in K+ contentsof wheat grains in both treatments suggest that the effect ofsalinity on the physiological phenomenon studied is due to changesin the ionic content of the plants. 1 In partial fulfilment of a Ph.D. degree from the Universityof Karachi, Pakistan. 2 Professor of Botany, Director of Research Projects, Head,Plant Physiology Section, University of Karachi, Pakistan. (Received July 11, 1977; )  相似文献   
5.
6.

Background  

A hot new topic in medical treatment is the use of mesenchymal stem cells (MSC) in therapy. The low frequency of this subpopulation of stem cells in bone marrow (BM) necessitates their in vitro expansion prior to clinical use. We evaluated the effect of long term culture on the senescence of these cells.  相似文献   
7.
8.
Molecular Biology Reports - Heat shock phenomenon is a process by which cells express a set of proteins called heat shock proteins (HSPs) against heat stress. HSPs include several families...  相似文献   
9.
10.
An efficient protocol for in-vitro propagation of an important ornamental crop, Petunia hybrida Vilm. Cv. “Bravo” was developed. The explants that were used to carry out the experiment were Leaf segments, nodal segments and shoot tips. Nodal segments recorded highest per cent asepsis followed by shoot tips and leaf segments. Asepsis was found to be highest when the explants were sterilized with Fungicide (Carbendazim) 0.02% for the duration of 30 min followed by 0.1% HgCl2 for duration of 10 min and then ethanol 70% for 10 s. Longer duration of the sterilant treatment showed more necrotic effects on the explants, thus mercuric chloride treatment when given for 5 min proved to be more effective in terms of survival of the explants. Maximum establishment per cent was recorded in Murashige and Skoog (MS) media fortified with BAP (1.5 mg L−1) and IBA (0.5 mg L−1) in shoot tips and nodal segments, i.e. 97.90 and 95.74% respectively. Callus was efficiently induced and developed when PGR amalgamation of BAP (0.1 mg L−1) and 2,4-D (1.5mg L−1) was used. Kinetin at the concentration of 2.0 mg L−1 along with IBA at 0.5mg L−1 recorded highest callus regeneration in both leaf and internodal segment derived callus. Maximum proliferation percent of shoots (97.90%), highest number of shoots (20.50 explant−1) and maximum length of shoot (2.70 cm) was recorded in PGR combination of IBA and BAP both at 0.5 mg L1 concentration level. Rhizogenesis was recorded to be highest in the MS media containing IBA 1.00 mg L−1. Best hardening media which recorded maximum survival per cent 92.50% was noticed on the media formulation comprised of equal ratio of perlite and vermiculite mix, under poly house conditions.  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