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   137453篇
  免费   2848篇
  国内免费   75篇
林业   5388篇
农学   4270篇
基础科学   871篇
  17128篇
综合类   21488篇
农作物   5396篇
水产渔业   6807篇
畜牧兽医   68212篇
园艺   1801篇
植物保护   9015篇
  2020年   1264篇
  2019年   1436篇
  2018年   2032篇
  2017年   2335篇
  2016年   2118篇
  2015年   1746篇
  2014年   2229篇
  2013年   5298篇
  2012年   4122篇
  2011年   5096篇
  2010年   3248篇
  2009年   3392篇
  2008年   4973篇
  2007年   4667篇
  2006年   4355篇
  2005年   4088篇
  2004年   3850篇
  2003年   3973篇
  2002年   3542篇
  2001年   4150篇
  2000年   4252篇
  1999年   3372篇
  1998年   1474篇
  1997年   1387篇
  1996年   1288篇
  1995年   1529篇
  1994年   1358篇
  1993年   1231篇
  1992年   2584篇
  1991年   2700篇
  1990年   2591篇
  1989年   2611篇
  1988年   2368篇
  1987年   2348篇
  1986年   2427篇
  1985年   2340篇
  1984年   1881篇
  1983年   1677篇
  1982年   1149篇
  1979年   1748篇
  1978年   1397篇
  1977年   1151篇
  1976年   1212篇
  1975年   1292篇
  1974年   1500篇
  1973年   1514篇
  1972年   1405篇
  1971年   1304篇
  1970年   1251篇
  1969年   1283篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
71.
The entomogenous nematode,Steinernema carpocapsae was applied in three forms in two fields cultivated with cotton and tomato, under each cotton seedling or tomato plant: a bait like form, a suspension and in irrigation water. High concentrations of 2000 and 1000 IJS/seedling induced 100% mortality (after 5 days), while lower concentrations showed the same result but after 15 days or later. Under all doses of nematode, bait form application was more effective than suspension or irrigated water.  相似文献   
72.
A new species of myocoptid mite, Trichoecius calomysci sp. n. (Acari: Myocoptidae), from Calomyscus sp. (Rodentia: Cricetidae) from Iran is described.  相似文献   
73.
74.
75.
76.
BACKGROUND: For an oil adjuvant to enhance uptake of a particulate active ingredient (AI), it is hypothesised that closer association between the two should result in higher uptake. Accordingly, factors important for the spray deposit size on grapevine leaves have been investigated for a series of model suspoemulsion formulations containing colloidal crystalline AI or fluorescent pigment particles and an emulsion of an oil adjuvant with different degrees of wetting and different spray volumes. RESULTS: Low spray volumes (<100 L ha(-1)) produced small deposits with high particle-adjuvant association. Complementary uptake studies showed increased uptake with decreasing deposit size, in agreement with the above hypothesis. Higher spray volumes produced larger deposits that consisted of annuli formed by pinning of the contact line by particles. Low surfactant concentrations favoured particles in the annulus and adjuvant separated in the centre. Intermediate surfactant concentrations produced annuli containing both particles and adjuvant, while with high surfactant concentrations the deposits were large with few annuli.CONCLUSIONS: Small deposits result in high AI-adjuvant association. With larger deposits, annulus structures allow for enhanced AI-adjuvant association (5-20 times greater). The formation of annuli appears to be important in enhancing the biodelivery of particulate AIs in adjuvant-containing suspoemulsion formulations at intermediate spray volumes.  相似文献   
77.
The efficacy of a topical preparation containing 0.5% fusidic acid and 0.1% betamethasone-17-valerate was compared to a systemic therapy (comprising a combination of parenteral dexamethasone and oral clavulanate-potentiated amoxycillin) in the treatment of 104 dogs with acute moist dermatitis. Significant improvement was evident after seven days in both treatment groups in all clinical parameters assessed and there was no significant difference in the overall response between the two treatment groups. Staphylococcus intermedius was the most frequently isolated organism from swabs at the first visit (Day 0). No resistance to fusidic acid or clavulanate-potentiated amoxycillin was encountered. The study demonstrates no difference in the clinical improvement achieved in canine acute moist dermatitis following topical or systemic therapy and that both treatment regimes represent effective treatment options for the condition.  相似文献   
78.
Harcourt AH 《Science (New York, N.Y.)》2005,310(5752):1276-8; author reply 1276-8
  相似文献   
79.
80.
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