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   91597篇
  免费   5317篇
  国内免费   59篇
林业   3654篇
农学   2592篇
基础科学   616篇
  11451篇
综合类   15057篇
农作物   3485篇
水产渔业   4735篇
畜牧兽医   48625篇
园艺   1010篇
植物保护   5748篇
  2018年   1424篇
  2017年   1576篇
  2016年   1485篇
  2015年   1252篇
  2014年   1513篇
  2013年   3573篇
  2012年   2730篇
  2011年   3243篇
  2010年   1996篇
  2009年   2011篇
  2008年   3047篇
  2007年   2874篇
  2006年   2762篇
  2005年   2507篇
  2004年   2409篇
  2003年   2363篇
  2002年   2192篇
  2001年   2874篇
  2000年   2963篇
  1999年   2269篇
  1998年   843篇
  1997年   848篇
  1996年   826篇
  1995年   1030篇
  1994年   899篇
  1993年   853篇
  1992年   1979篇
  1991年   2116篇
  1990年   1960篇
  1989年   1975篇
  1988年   1858篇
  1987年   1955篇
  1986年   2007篇
  1985年   1911篇
  1984年   1510篇
  1983年   1330篇
  1982年   898篇
  1979年   1396篇
  1978年   1145篇
  1977年   996篇
  1976年   944篇
  1975年   989篇
  1974年   1296篇
  1973年   1337篇
  1972年   1255篇
  1971年   1167篇
  1970年   1092篇
  1969年   974篇
  1968年   837篇
  1967年   872篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
A bovine adenovirus with agglutinating activity was isolated from feedlot calves and classified as serotype 3. The agglutinating activity was shown to be the property of an adenovirus-associated virus (AAV). The AAV was isolated from the bovine adenovirus by isopycnic centrifugation in CsCl; the AAV had a density of 1.4 g/cm2. This AAV is serologically related to bovine AAV-TR-15, but is distinct from bovine parvovirus-1 and primate AAV types 1 to 4, using counterimmunoelectrophoresis and hemagglutination-inhibition.  相似文献   
922.
Bovine adenovirus type 7 was isolated from a 10-month-old calf with fibrinopurulent pneumonia and from 2 newborn calves with pneumoenteritis. The viruses were isolated on calf lung and adrenal gland cell cultures and were identified as serotype 7 by immunoelectron microscopy and serum-neutralization tests.  相似文献   
923.
Aprotinin, a proteinase inhibitor, was evaluated as a pharmacologic aid in dogs subjected to lethal hemorrhagic shock. Survival time, hemodynamic changes, and plasma enzyme analysis were measured as criteria for drug effects. Mixed-breed dogs (n = 14) were divided into 2 groups of 7 each: nontreated dogs in shock (group 1) and aprotinin-treated dogs in shock (group 2). One of 7 dogs in group 1 and 2 of 7 dogs in group 2 survived. Survival time, for the remaining dogs in group 1 (190 min, n = 6) and group 2 (188 min, n = 5) were not significantly different. There was no significant difference in mean arterial pressure, mean pulmonary arterial pressure, cardiac output, or left ventricle systolic pressure associated with aprotinin treatment at any time after hemorrhagic shock. There was no significant difference in plasma lactic acid, aspartate aminotransferase, alanine aminotransferase, creatine phosphokinase, alpha-amylase, and beta-glucuronidase associated with treatment at any time; however, there were significant (P less than 0.05) increases with time. The gastrointestinal tract was the site of most obvious lesions found at necropsy. Lesions varied considerably in extent and severity without apparent correlation to the treatment regimen. These experiments did not show beneficial effects of aprotinin in dogs subjected to hemorrhagic shock, but neither did they completely rule out some valuable actions that may have been obscured by the type of model used.  相似文献   
924.
1. Blackening of the skin in factory processed cooked hens has been associated with elevated copper levels.

2. The degree of blackening was not directly related to copper content although the latter level was always higher than in control hens.

3. Simulated factory procedures, using scald water at 53 °C or 60 °C containing 50 mg Cu2+/1 and 50 mg C12/1, produced blackened skins of varying intensity on cooking.

4. It is suggested that the problem arose from a malfunction of the chlorination plant which produced excessive levels of chlorine and low pH, followed by erosion of copper from water pipes and subsequent interaction of copper and chlorine with the chicken skin.  相似文献   

925.
1. n‐Paraffin‐grown yeast and a mixture of soyabean meal and fish meal were compared in the net protein utilisation (NPU) test, and as protein supplements in diets for broilers up to 4 weeks of age.

2. The difference between the NPU values, 0.66 for yeast and 0.80 for the soyabean meal and fish meal mixture, could largely be attributed to the high nucleic acid content of the yeast.

3. Chicks given the diet containing yeast (190 g/kg) did not grow as rapidly as those given the soyabean meal and fish meal reference diet, and the reduced growth could only partly be explained by a marginal deficiency of methionine.

4. Food conversion efficiency with the yeast diet was improved by maize oil while responses to α‐tocopheryl acetate and sodium selenite were inconsistent.

5. Chicks grew well when yeast replaced fish meal in the mixture of soyabean meal and fish meal, and when fish meal (194 g/kg diet) was the sole protein supplement.  相似文献   

926.
927.
928.
929.
930.
"Sound and careful surgery is the sine qua non of wound management; antimicrobials are adjunctive." The key to successful use of prophylactic antibiotics in surgery is careful selection of cases and medication. There are no final rule or formulas that will always give optimal results. Listed below are some guidelines that may assis the clinician in determining the need and form of antimicrobial use. 1. The operation must carry a significant risk of bacterial contamination. Refined-clean and clean procedures should not be given prophylactic antibiotics. 2. Bacterial cultures should be taken when possible, and the medication used for prophylaxis should be effective against the organisms expected to be encountered. 3. Narrow spectrum antibiotics should be used to conserve the body's normal flora. Broad spectrum antibiotics needed to combat resistant infections should not be used for prophylaxis. 4. The antibiotic should be present in the wound in effective concentrations at the time of the incision and be maintained only as long as the risk of new bacterial contamination exists.  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