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   115224篇
  免费   5870篇
  国内免费   77篇
林业   5051篇
农学   3659篇
基础科学   589篇
  12790篇
综合类   21725篇
农作物   4292篇
水产渔业   5604篇
畜牧兽医   59144篇
园艺   1393篇
植物保护   6924篇
  2018年   1462篇
  2017年   1568篇
  2016年   1486篇
  2015年   1260篇
  2014年   1540篇
  2013年   4054篇
  2012年   2723篇
  2011年   3434篇
  2010年   2287篇
  2009年   2172篇
  2008年   3364篇
  2007年   3325篇
  2006年   3067篇
  2005年   2926篇
  2004年   2851篇
  2003年   2859篇
  2002年   2651篇
  2001年   3642篇
  2000年   3664篇
  1999年   2959篇
  1998年   1156篇
  1997年   1119篇
  1995年   1316篇
  1994年   1081篇
  1993年   1068篇
  1992年   2380篇
  1991年   2531篇
  1990年   2589篇
  1989年   2493篇
  1988年   2339篇
  1987年   2359篇
  1986年   2366篇
  1985年   2281篇
  1984年   1871篇
  1983年   1673篇
  1982年   1085篇
  1979年   1732篇
  1978年   1372篇
  1977年   1198篇
  1976年   1131篇
  1975年   1271篇
  1974年   1619篇
  1973年   1636篇
  1972年   1679篇
  1971年   1547篇
  1970年   1439篇
  1969年   1379篇
  1968年   1157篇
  1967年   1221篇
  1966年   1097篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
In the course of vaccine controls, the potency of 25 foot-and-mouth disease (FMD) vaccines was tested quantitatively in parallel in cattle using the intradermal infection and the determination of the SN titres. More than 95% of the vaccinated cattle with SN titres of greater than 1:20 were protected from generalized FMD, regardless of the virus type tested. 61.5% of the vaccinated cattle with SN titres less than or equal to 1:20 were not protected and developed generalized FMD. Comparison of the PD50 values calculated from the results of the intradermal infection and the corresponding SN titres (minimum protection titre greater than 1:20) showed that the results were in complete agreement in 56% of the tested vaccines. In a further 32% of vaccines, the PD50 calculated from the SN titre was slightly below that for the intradermal infection, in the remaining 12% it was somewhat above. The possibility of using the minimum titre determination for testing a vaccine and the significance of this titre as an expression of protection by vaccination are discussed.  相似文献   
122.
123.
124.
125.
126.
127.
128.
The attenuation of a Babesia bovis strain depends on its protease content. The present work evaluates this parameter on a virulent strain, before and after attenuation by quick passages on splenectomized calves. The protease activity at different pH values was determined in protein fractions from the blood of calves. The enzymatic test showed marked differences between the protease content of both substrains.  相似文献   
129.
Recombinant canine granulocyte colony-stimulating factor (rcG-CSF) was administered to clinically normal dogs, cyclic-hematopoietic dogs, and dogs undergoing autologous bone marrow transplantation, to determine whether rcG-CSF could be used to stimulate WBC production and function in normal and neutropenic dogs. To the normal dogs, rcG-CSF was administered by SC injection at rates of 1 microgram/kg of body weight, q 12 h; 2 micrograms/kg, q 12 h; or 5 micrograms/kg, q 12 h. A significant dose-dependent increase in the WBC count resulted from the stimulation of bone marrow progenitor cells. The increased WBC count was characterized by mature neutrophilia and monocytosis. Neutrophil myeloperoxidase and phagocytic activity were normal in rcG-CSF-treated normal dogs, demonstrating the production of normal functional neutrophils in response to rcG-CSF treatment. Recombinant canine G-CSF prevented neutropenia and associated clinical signs but did not completely eliminate the cycling of neutrophils in cyclic-hematopoietic dogs when it was administered at rates of 1 microgram/kg, q 12 h, and 2.5 micrograms/kg, q 12 h. The time to bone marrow reconstitution was not decreased in dogs treated with rcG-CSF at a rate of 2.5 micrograms/kg, q 12 h, for 13 days following autologous bone marrow transplantation. On the basis of our findings, we suggest that treatment with rcG-CSF is an effective way to stimulate myelopoiesis in dogs, but that the dose of rcG-CSF required to stimulate WBC production will vary depending on the cause of neutropenia. Recombinant canine G-CSF should be useful in stimulating production and maintaining function of WBC for treatment of clinical diseases seen commonly in veterinary practice.  相似文献   
130.
Coccidioidomycosis was diagnosed in 48 cats. Forty-one cases were identified within a period of 3 years. Coccidioides immitis was revealed by cytological or histopathological examinations, or culture in 70% of cats. The remaining 30% of cases were diagnosed by appropriate clinical signs, radiographic lesions, and serological test results. The average age of affected cats was 6.2 years with a median age of 5.0 years. Fifty-four percent (n = 26) were female and 46% (n = 22) were male. Domestic shorthaired and longhaired breeds comprised 89% (n = 41) of affected cats. Sixty-seven percent of cases were diagnosed during the 6-month period of December through May. Cats infected with C immitis were presented for evaluation of dermatologic (56%), respiratory (25%), musculoskeletal (19%), and neurological or ophthalmologic signs (19%). Fever, inappetence, and weight loss were present in 44% of the cats. Duration of clinical signs before diagnosis was less than 4 weeks in 85% (n = 42) of cats, with an average of 3.8 weeks and a median of 2 weeks. Agar gel immunodiffusion tests were positive in all 39 cats tested at sometime during the course of their disease. Hyperproteinemia (greater than 7.9 g/dL) was present in 52% (10/23) of cases. The majority of cats (n = 39) were negative for feline leukemia virus. Antibodies to feline immunodeficiency virus were absent in the 19 cats tested. Ketoconazole was the most common antifungal agent used to treat cats with Coccidioidomycosis. Duration of treatment ranged from less than 1 week to 43 months. Thirty-two cats are currently asymptomatic, with or without treatment. Eleven cats died or were euthanized. Five cats were lost to follow-up. Ketoconazole likely is more suppressive than curative because relapses were common after discontinuing therapy.  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