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   38462篇
  免费   2268篇
  国内免费   285篇
林业   1584篇
农学   1416篇
基础科学   325篇
  5505篇
综合类   5707篇
农作物   1492篇
水产渔业   1808篇
畜牧兽医   20013篇
园艺   467篇
植物保护   2698篇
  2021年   363篇
  2020年   426篇
  2019年   471篇
  2018年   789篇
  2017年   840篇
  2016年   754篇
  2015年   631篇
  2014年   788篇
  2013年   1843篇
  2012年   1322篇
  2011年   1535篇
  2010年   1064篇
  2009年   1093篇
  2008年   1483篇
  2007年   1335篇
  2006年   1261篇
  2005年   1085篇
  2004年   1042篇
  2003年   1034篇
  2002年   913篇
  2001年   1252篇
  2000年   1235篇
  1999年   931篇
  1998年   392篇
  1997年   419篇
  1996年   343篇
  1995年   396篇
  1994年   344篇
  1992年   662篇
  1991年   787篇
  1990年   695篇
  1989年   726篇
  1988年   670篇
  1987年   626篇
  1986年   674篇
  1985年   597篇
  1984年   467篇
  1983年   415篇
  1979年   558篇
  1978年   431篇
  1977年   362篇
  1976年   367篇
  1975年   402篇
  1974年   465篇
  1973年   482篇
  1972年   449篇
  1970年   369篇
  1969年   401篇
  1968年   361篇
  1967年   359篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
36.
37.
Quantitative and qualitative bacterial assays were performed on the skin of 15 normal and 32 seborrheic dogs. Nonionic detergent scrubs were made on areas demarcated by glass sidearm cylinders. Quantitative analysis was accomplished by the serial dilution technique, and the bacteria were identified by individual and colonial morphology and by enzyme production. Areas measured on control dogs had a markedly lower total bacterial count than similar areas measured on seborrheic animals. Control dogs had a flora consisting primarily of coagulase-negative cocci, whereas seborrheic dogs usually had a cutaneous flora composed primarily of Stahylococcus aureus, coagulase-positive.  相似文献   
38.
Sunlight is known to reduce the incidence of blister blight disease of tea, caused by Exobasidium vexans . The effects of the ultraviolet-B (UV-B: 290–320 nm) component of solar radiation on the disease and the development of E. vexans were studied in the field in Sri Lanka using UV-screening filter materials held over a commercial crop. Exclusion of UV-B radiation by Polyester, which reduces fluxes in the UV-B region by approximately 75–85%, increased both the number of translucent spots (immature sites of infection) and number of sporulating blisters (mature sites of infection), but it had little or no effect on the sporulation of the pathogen. When basidiospores were artificially inoculated on leaves, and were exposed to full or filtered solar radiation, their survival and germination increased when UV-B wavelengths were removed; significant differences were found 62 h after inoculation. However, UV-B did not affect the extension of germ tubes. This study indicates that the UV-B component of solar radiation plays an important role in the natural regulation of blister blight disease in the field.  相似文献   
39.
Pseudomonas fluorescens strain Pf1, inhibitory to the growth of the rice blast pathogen Pyricularia oryzae in vitro , was developed as a talc-based powder formulation. When rice seeds were treated with this formulation, the bacteria spread to roots, stems and leaves of the plants and protected against leaf infection by P. oryzae . When applied as a foliar spray, the bacteria survived on the leaves. The powder formulation controlled leaf blast under greenhouse conditions. In tests as a seed treatment and foliar spray in four field trials it effectively controlled the disease and increased grain yield.  相似文献   
40.
In recent years, natural deep eutectic solvents (NADES) have been widely investigated for the extraction of food and medicinal plants as well as seaweeds. However, the ability of NADES for trace elements co-extraction from natural sources is not well investigated. The aim of this study was to investigate the ability of common NADES for trace elements co-extraction from Fucus vesiculosus. All of the tested NADES did not recover As and Co (concentration <LOQ). Moreover, all of the tested NADES provided a low recovery (<9%) of Ba, Ca, Fe, Mg, Mn, Sr, and Zn. The method of extraction had not shown a statistically significant effect on the co-extraction of all elements (excluding Ba and Ca). In contrast, the water content in NADES was significantly affected on the recovery of Ba, Ca, Mg, Mn, Sr, and Zn. The recovery of Al and Cr was relatively high and considerably varied (from 1.5 to 59.9%). NADES comprising lactic acid:glucose:H2O (5:3:1) provided the lowest contents of all elements, and the highest extracted amounts were obtained employing water contents of 60–80%. The calculated daily intake of all the elements contained in NADES extracts were less than the daily dose risk estimators. The hazard quotients, hazard indexes, and carcinogenic risk calculated for all trace elements and their combination were considerably less than 1. This evidences no health risk, and carcinogenic risk after topical application of all studied NADES. For the first time, the results of the current study demonstrated that NADES extracts of F. vesiculosus contain a lower amount of trace metals and are safer than the extracts obtained with water and 70% acetone. This indicates a significant advantage for NADES compared with the other solvents.  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