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   35750篇
  免费   1505篇
  国内免费   16篇
林业   1542篇
农学   1096篇
基础科学   224篇
  5861篇
综合类   4661篇
农作物   1410篇
水产渔业   1506篇
畜牧兽医   18283篇
园艺   495篇
植物保护   2193篇
  2021年   315篇
  2020年   373篇
  2019年   465篇
  2018年   698篇
  2017年   785篇
  2016年   690篇
  2015年   454篇
  2014年   696篇
  2013年   1920篇
  2012年   1165篇
  2011年   1490篇
  2010年   1050篇
  2009年   961篇
  2008年   1412篇
  2007年   1383篇
  2006年   1233篇
  2005年   1059篇
  2004年   1028篇
  2003年   939篇
  2002年   886篇
  2001年   820篇
  2000年   811篇
  1999年   628篇
  1998年   309篇
  1997年   275篇
  1995年   313篇
  1992年   434篇
  1991年   451篇
  1990年   470篇
  1989年   479篇
  1988年   381篇
  1987年   379篇
  1986年   403篇
  1985年   375篇
  1984年   353篇
  1983年   337篇
  1979年   494篇
  1978年   346篇
  1977年   387篇
  1976年   479篇
  1975年   494篇
  1974年   538篇
  1973年   496篇
  1972年   452篇
  1971年   360篇
  1970年   381篇
  1969年   438篇
  1968年   451篇
  1967年   454篇
  1966年   447篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Two enzyme-linked immunosorbent assays (ELISA), one based on a mouse anti-Trypanosoma brucei group-specific monoclonal antibody and the other on rabbit anti-Trypanosoma evansi polyclonal antibodies, have been evaluated for their ability to detect circulating trypanosome antigens in camel sera as a means for the diagnosis of T. evansi infections. All 91 sera from a negative control camel herd from Kenya gave negative antigen-ELISA results in the monoclonal antibody-based ELISA and only 2 of them (2.2%) gave false positive results in the polyclonal antibody-based ELISA. In subsequent analyses of sera from infected camels (as determined by mouse inoculation), the monoclonal antibody-based ELISA detected antigens in 90 (83.3%) out of the 108 sera tested. This percentage was lower for the polyclonal antibody-based ELISA which was able to detect antigens in 67 (60.9%) out of the 110 sera tested. The two tests detected probably different antigens and when the results were combined, 99 out of 107 (92.5%) sera were shown to be ELISA positive. In a survey involving 316 camels from the Gao and Nara areas, in Mali, a high proportion of animals tested were antigen positive (43.5 and 42.9%, respectively for the mono- and polyclonal antibody-based ELISA) compared to only 22 (7.0%) diagnosed by the parasite detection techniques. Thus, these immunoassays were at least six times more sensitive than the haematocrit centrifugation technique. As a large proportion of cases may be antigen positive but parasite negative, these two of "surra" immunoassays should be used in routine diagnosis in addition to the parasite detection techniques in the dromedary camel.  相似文献   
84.
85.
86.
87.
A mycoplasma identified asMycoplasma mycoides subspmycoides LC type was isolated from an outbreak of caprine pleuropneumonia and serofibrinous peritonitis. This isolate was the first to be reported in Italy. Experimentally, a rapidly fatal condition followed its inoculation into goats and sheep but inoculation of calves did not lead to clinically apparent infection. Although the organism was recovered for up to 45 days following experimental inoculation of calves, pathological changes were limited to the drainage lymph nodes except in one case where there were histological changes in the lungs.  相似文献   
88.
It is proposed that human comfort could be provided in otherwise chilly surroundings by filling the occupied space with electromagnetic energy of centimeter wavelength. Very considerable reductions in the consumption of energy required for the heating of buildings should result from the lowering of interior temperatures thereby permitted.  相似文献   
89.
D. V. CLAY 《Weed Research》1980,20(2):97-102
The tolerance of strawberries to herbicides was tested by applications to the roots of plants growing in sand and by foliage applications to plants grown in compost, and compared with tolerance in the field. Dimefuron was safe as a foliar application but much more toxic than simazine when applied in sand or in the field. Metamitron caused slight injury as a foliar spray; in sand and in the field it was intermediate in toxicity between simazine and lenacil. At normal rates propachlor was safe as a foliar spray and much safer than lenacil when applied in sand. High rates had no adverse effect in the field. Ethofumesate and pendimethalin caused some temporary stunting when applied to foliage, but were less toxic than lenacil when applied to roots in sand. Field applications of both herbicides at 1–1.5 kg/ha were safe. Foliage sprays of bentazone, oxadiazon and oxyfluorfen severely damaged the sprayed leaves, but these herbicides were less active than lenacil when applied to the roots. In the field they caused severe leaf damage, but by the end of the growing season the plants had recovered. The experiments demonstrated the value of separate root and shoot activity tests for indicating which herbicides merit further field testing.  相似文献   
90.
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