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   155726篇
  免费   8381篇
  国内免费   325篇
林业   6861篇
农学   5344篇
基础科学   1272篇
  19471篇
综合类   27220篇
农作物   6083篇
水产渔业   7754篇
畜牧兽医   76932篇
园艺   2391篇
植物保护   11104篇
  2018年   2887篇
  2017年   3110篇
  2016年   2384篇
  2015年   1757篇
  2014年   2076篇
  2013年   5505篇
  2012年   4278篇
  2011年   5903篇
  2010年   4188篇
  2009年   4027篇
  2008年   5552篇
  2007年   5553篇
  2006年   4497篇
  2005年   4273篇
  2004年   4039篇
  2003年   4087篇
  2002年   3961篇
  2001年   4755篇
  2000年   4615篇
  1999年   3762篇
  1998年   1517篇
  1997年   1545篇
  1996年   1437篇
  1995年   1781篇
  1994年   1633篇
  1993年   1558篇
  1992年   3207篇
  1991年   3310篇
  1990年   3351篇
  1989年   3365篇
  1988年   3081篇
  1987年   3135篇
  1986年   3227篇
  1985年   3088篇
  1984年   2608篇
  1983年   2309篇
  1982年   1576篇
  1981年   1473篇
  1980年   1430篇
  1979年   2317篇
  1978年   1909篇
  1977年   1636篇
  1976年   1441篇
  1975年   1540篇
  1974年   2074篇
  1973年   2086篇
  1972年   2054篇
  1971年   1816篇
  1970年   1712篇
  1969年   1572篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
Isolated dog neutrophils exposed to known chemotactic factors assumed a bipolar configuration in suspension. This response was initiated within 2 minutes with a gradual return to spherical shape. The rate of return to sphere was positively correlated with the dose of stimulant. Dog neutrophils exposed to N-formylmethionyl-leucyl-phenylalanine (fMLP) did not adapt to bipolar conformation and did not bind radiolabeled fMLP. These findings are consistent with other species (pig and cow) that also did not respond to fMLP.  相似文献   
87.
Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.  相似文献   
88.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.  相似文献   
89.
90.
A steam-dryer, designed and manufactured in Sweden, was evaluated for destroying Bursaphelenchus xylophilus in pine chips from southern USA. In a trial, pine chips were treated at different temperature and pressure regimes for 5 or 10min. The lowest time/temperature/pressure combination was to increase the vessel temperature from 85 to 104°C in 5 min at low pressure. Samples of pine chips were assayed for nematodes in laboratories in USA, Sweden, and Finland. No nematodes of any species were recovered from any of the treated pine-chip samples. Large and heterogeneous pieces of wood in the treated samples were also nematode-free. The apparatus was a prototype capable of handling about 400 kg h-1. The final version would have to be able to process 100-200 th-1.  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