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   135641篇
  免费   7787篇
  国内免费   70篇
林业   5577篇
农学   4647篇
基础科学   862篇
  17486篇
综合类   18956篇
农作物   5088篇
水产渔业   7089篇
畜牧兽医   72969篇
园艺   1798篇
植物保护   9026篇
  2020年   1172篇
  2019年   1411篇
  2018年   2229篇
  2017年   2489篇
  2016年   2295篇
  2015年   1999篇
  2014年   2451篇
  2013年   5731篇
  2012年   4352篇
  2011年   5164篇
  2010年   3503篇
  2009年   3547篇
  2008年   5152篇
  2007年   4972篇
  2006年   4641篇
  2005年   4262篇
  2004年   4108篇
  2003年   4174篇
  2002年   3808篇
  2001年   4773篇
  2000年   4641篇
  1999年   3747篇
  1998年   1471篇
  1997年   1452篇
  1996年   1341篇
  1995年   1599篇
  1994年   1328篇
  1993年   1359篇
  1992年   2762篇
  1991年   2901篇
  1990年   2866篇
  1989年   2897篇
  1988年   2610篇
  1987年   2592篇
  1986年   2539篇
  1985年   2400篇
  1984年   1956篇
  1983年   1715篇
  1982年   1154篇
  1979年   1649篇
  1978年   1284篇
  1977年   1135篇
  1976年   1100篇
  1975年   1164篇
  1974年   1357篇
  1973年   1448篇
  1972年   1378篇
  1971年   1195篇
  1970年   1247篇
  1969年   1146篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
991.
992.
993.
Soluble proteins present in the supernatant prepared from a sonicated lysate of concentrated erythrocytes infected with Babesia divergens were separated by isoelectric focussing into acidic and non acidic fractions. The acidic fraction was further separated by passage through Concanavalin A Sepharose (Con A) into two fractions, the first (Fraction 2) consisting of proteins plus one glycoprotein which did not bind to Con A, the second of glycoproteins (Fraction 1) which were eluted after binding to Con A. One group of six cows was treated with three injections of Fraction 2 with incomplete Freunds adjuvant (IFA); two other groups received the same number of injections of Fraction 1, one with IFA, the other with glucan as adjuvant. These cows plus an untreated control group were infected with 10(5) erythrocytes infected with a heterologous isolate of B. divergens. Only the group treated with Fraction 2 (Group 1) resisted lethal multiplication of the parasite. There were significant differences in magnitude of parasitaemia, reduction of packed cell volume and antibody titres between Group 1 and the other groups.  相似文献   
994.
995.
996.
997.
In 7 horses, 4 anastomoses were done in the small intestine in each, using the combinations of synthetic absorbable monofilament and multifilament suture materials with continuous- and interrupted-suture patterns in the serosubmucosal layer of a 2-layer inverting-suture technique. Horses were evaluated 30 days after the operation for adhesion formation, lumen diameter, evidence of chronic obstruction, and suture tract inflammation at the anastomosis. Postoperative obstruction occurred in 5 of the 7 horses, and 6 horses survived. One horse was euthanatized on postoperative day 6 after 48 hours of ileus and obstruction; necropsy revealed a partial intussusception involving the anastomosis done with continuous multifilament-suture material. Two other horses that became obstructed between postoperative days 3 and 5 had protracted ileus and gastric reflux up to 48 hours' duration, but survived. Horses that had obstruction after the 6th postoperative day recovered within 4 hours of onset. The continuous inverting-suture pattern in the serosubmucosal layer resulted in significantly (P less than 0.05) fewer adhesions than did the interrupted pattern, and suture material had no effect on adhesion formation. There was no significant difference in the percentage of reduction of lumen diameter between the variations of the 2-layer technique, and there was no evidence of chronic obstruction related to any of the anastomoses. Suture tract inflammation was moderate in the anastomoses, using continuous-multifilament suture, with neutrophils being the predominant cell type. The anastomoses with continuous-monofilament suture had mild inflammation with focal accumulations of neutrophils. Minimal inflammation was associated with both types of suture in the interrupted pattern.  相似文献   
998.
Gold-induced immune thrombocytopenia in the dog   总被引:1,自引:0,他引:1  
In two seven-year studies with gold compounds in dogs of both sexes, thrombocytopenia was observed after 45 to 72 months of dosing in three of 14 and two of 14 dogs in high-dose groups that received 2.4 to 3.6 mg/kg of auranofin per day orally or 0.5 to 2.0 mg/kg of gold sodium thiomalate intramuscularly once every three days, respectively. An immune basis for the disorder was suggested by the apparent consumptive nature of the thrombocytopenia (increased bone marrow megakaryocytes and large peripheral blood platelets), the response to corticosteroid therapy and the demonstration of increased platelet-associated immunoglobulin. The latter was demonstrated with a solid phase radioimmunoassay and by electron microscopy using a staphylococcal protein A-colloidal gold conjugate. Platelet-associated immunoglobulin decreased as the platelet counts rose, and in one dog monitored over periods of steroid-induced remissions and subsequent relapses, the amount of platelet-associated immunoglobulin G correlated inversely with the platelet count (r = 0.82). These findings suggest that the long-term administration of gold compounds in dogs is associated with a dose-dependent incidence of thrombocytopenia, which is immune-mediated and similar to that associated with parenteral chrysotherapy in man. The application of tests for platelet-associated immunoglobulin to canine patients with immune thrombocytopenia should be useful in the diagnosis of the disorder in clinical practice.  相似文献   
999.
1000.
Seasonal variations in beta carotene intake and low levels of beta carotene and vitamin A in blood plasma were found in cows fed ration based mainly on maize silage. The supplementation of daily winter rations with 300 mg Rovimix-beta carotene per cow, beginning 14 days before parturition and 60 days after calving increased slighty the beta carotene and vitamin A concentrations of blood plasma and improved some fertility indices: the number of inseminations per cow was reduced and the percentage of conception rate was significantly higher. It may be assumed that beta carotene content in feeds and it's utilization rate generally reflected in beta carotene blood plasma level and in the improvement of fertility.  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