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   2032篇
  免费   23篇
  国内免费   178篇
  2023年   25篇
  2022年   30篇
  2021年   55篇
  2020年   59篇
  2019年   72篇
  2018年   93篇
  2017年   36篇
  2016年   47篇
  2015年   65篇
  2014年   154篇
  2013年   126篇
  2012年   64篇
  2011年   87篇
  2010年   66篇
  2009年   87篇
  2008年   88篇
  2007年   86篇
  2006年   68篇
  2005年   94篇
  2004年   62篇
  2003年   57篇
  2002年   54篇
  2001年   22篇
  2000年   17篇
  1999年   32篇
  1998年   29篇
  1997年   35篇
  1996年   40篇
  1995年   36篇
  1994年   42篇
  1993年   33篇
  1992年   30篇
  1991年   36篇
  1990年   28篇
  1989年   30篇
  1988年   29篇
  1987年   28篇
  1986年   14篇
  1985年   27篇
  1984年   34篇
  1983年   28篇
  1982年   12篇
  1981年   10篇
  1980年   10篇
  1979年   7篇
  1978年   10篇
  1977年   11篇
  1976年   9篇
  1975年   7篇
  1971年   5篇
排序方式: 共有2233条查询结果,搜索用时 14 毫秒
831.
832.
Comparative in planta studies with Pseudomonas syringae pv. syringae have established optimum conditions for disease expression in lilac in terms of inoculum concentration, host age and post-inoculation conditions (temperature and day-length). Reproducible disease reactions required an inoculum concentration exceeding the ED50, 5 × 106 cfu/ml, and a temperature for post-inoculation incubation not exceeding 19°C. A revised host range of P. syringae pv. syringae, proposed on the basis of confirmation of pathogenicity of strains to lilac, comprises 44 species from monocotyledonous and dicotyledonous plants. Nine new hosts Abelmoschus esculentus, Bromus willdenowii, Camellia sinensis, Centrosema pubescens, Citrullus lanatus, Cotoneaster sp., Cucumis melo, Populus×euramericana and Triticum aestivum, are recorded. A comparative laboratory study was made of strains of P. syringae pv. syringae using more than 30 selected biochemical and nutritional tests. The pathovar could be characterised on the basis of 11 of these which may prove to be useful determinative tests.  相似文献   
833.
A new species, Propionibacterium innocuum, is proposed to accommodate strains of coryneform bacteria from human skin with phenotypic characters similar to those of the classical propionibacteria but differing in exhibiting primarily aerobic respiration and possessing a unique cell wall composition in which LL-diaminopimelic acid and arabinose occur together. The partial 16S rRNA sequence confirms an affinity with the genus Pro-pionibacterium and indicates that the species represents a distinct line within the genus. The type strain of Propionibacterium innocuum is NCTC 11082.  相似文献   
834.
蓼属植物果皮微形态特征及其分类意义初探   总被引:1,自引:0,他引:1  
本文运用扫描电镜对部分蓼属植物果皮的微形态特征进行了观察,着重了解各类群果皮微形态特征的特性,比较不同类群间的区别,确定其分类价值。观察结果表明:蓼属植物在果皮微形态特征上存在较明显的种间差异,并且对不同类群和不同分类等级来说,其分类价值是不同的。研究结果还为蓼属某些类群和等级的合理划分提供了有用的资料。  相似文献   
835.
中国千斤拔属植物的初步研究   总被引:7,自引:0,他引:7  
韦裕宗   《广西植物》1991,11(3):193-207
本文叙述了千斤拔属名的拉丁学名的变换和研究情况,并研究该属植物国产种的分类、地理分布及其特点。进而对该属植物的习性和苞片、花序、花和叶等诸器官演化趋势作初步探讨,并对该属6个类群之间可能的演化关系、属的起源、分布中心和迁移路线等问题提出初设想。  相似文献   
836.
837.
Immunodiffusion patterns of the different morphological types of female Haemonchus contortus (Rudolphi, 1803) indicate that the three phenotypes—smooth, linguiform, and knobbed—differ from each other serologically. Linguiform antigens gave five precipitin lines, knobbed gave four lines, and smooth gave three precipitin lines with rabbit antisera. Also, lines unite in a manner indicating marked antigenic differences between the three types. Since serological studies are considered to be sensitive tools in taxonomy, the present work indicates that taxonomic importance should be attached to the vulvar configurations in female H. contortus.  相似文献   
838.
A total of 136 strains of Actinobacillus actinomycetemcomitans were studied for 135 features. All isolates were small nonmotile capnophilic gram-negative rods which grew with no requirement of X or V growth factors. They all decomposed hydrogen peroxide, were oxidase-negative and benzidine-positive, reduced nitrate, produced strong alkaline and acid phosphatases, and fermented fructose, glucose and mannose. Variable fermentation results were obtained with dextrin, maltose, mannitol and xylose. Some isolates produced small amounts of gas. Representative strains of Haemophilusaphrophilus were morphologically and biochemically quite similar to A. actinomycetemcomitans. Characters which should prove to be useful to identify and distinguish these two species include catalase reaction, fermentation of lactose, starch, sucrose and trehalose, and resistance to sodium fluoride. This information allows a rapid diagnosis by species and may be helpful in studies of infections involving these organisms.Abbreviations ONPG O-nitrophenyl--d-galactopyranoside  相似文献   
839.
ABSTRACT The surface structures of the elytra in twenty two species belonging to the subfamily Sericinae (Coleoptera, Melolonthidae) were observed by scanning electron microscopy. For viewing specific characters, elytral punctures and diffraction gratings on interstitial surface were focused on. The elytral punctures of observed Sericid beetles have three representative forms: horseshoe, ocellus, and crease types. The diffraction gratings of the elytra show three distinctive patterns: regular and parallel, discontinued, and interconnected and curved. These patterns of elytral punctures and diffraction gratings considered to be useful for identification.  相似文献   
840.
One species of Drepaninae, Tridrepana crocea (Leech), is added to the Korean fauna. Up to now, 23 species of Drepaninae are known in Korea. Diagnosis and the photographs of male and female genitalia of T. crocea are provided.  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