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   51650篇
  免费   2450篇
  国内免费   18篇
林业   1889篇
农学   1572篇
基础科学   318篇
  7362篇
综合类   6961篇
农作物   1957篇
水产渔业   2392篇
畜牧兽医   27905篇
园艺   583篇
植物保护   3179篇
  2019年   521篇
  2018年   902篇
  2017年   1039篇
  2016年   912篇
  2015年   661篇
  2014年   910篇
  2013年   2438篇
  2012年   1520篇
  2011年   1909篇
  2010年   1359篇
  2009年   1309篇
  2008年   1899篇
  2007年   1826篇
  2006年   1596篇
  2005年   1387篇
  2004年   1306篇
  2003年   1317篇
  2002年   1137篇
  2001年   1474篇
  2000年   1474篇
  1999年   1131篇
  1998年   495篇
  1997年   495篇
  1995年   505篇
  1993年   433篇
  1992年   780篇
  1991年   903篇
  1990年   834篇
  1989年   814篇
  1988年   722篇
  1987年   735篇
  1986年   720篇
  1985年   717篇
  1984年   655篇
  1983年   575篇
  1982年   439篇
  1979年   802篇
  1978年   574篇
  1977年   591篇
  1976年   687篇
  1975年   707篇
  1974年   790篇
  1973年   728篇
  1972年   703篇
  1971年   580篇
  1970年   567篇
  1969年   659篇
  1968年   639篇
  1967年   683篇
  1966年   674篇
排序方式: 共有10000条查询结果,搜索用时 71 毫秒
101.
OBJECTIVE: To evaluate semiquantitative and quantitative assays for microalbuminuria and determination of the urine albumin-creatinine (UAC) ratio in detection of systemic disease in dogs without overt proteinuria. DESIGN: Prospective study. ANIMALS: 408 dogs. PROCEDURES: Urine samples that had been obtained from dogs for which a complete medical record was available and in which results of a dipstick test for urine protein were negative were evaluated. Urine protein-creatinine ratios (cutoff values, 0.5 and 0.1), semiquantitative and quantitative microalbuminuria values (cutoff value, 1 mg/dL), and UAC ratios (cutoff values, 100 and 200 mg/g) were determined. Clinical diagnoses rendered within 3 months of enrollment in the study were recorded. Sensitivity and specificity were determined with disease status serving as the standard. Associations with clinical diagnosis, sex, age, BUN and serum creatinine concentrations, blood pressure, results of bacterial culture of urine, temperature, pyuria, hematuria, and bacteriuria were evaluated by use of logistic regression analysis. RESULTS: 48 dogs were healthy, and 360 had at least 1 disease. Significant associations were detected between age, presence of disease, presence of neoplastic disease, BUN and serum creatinine concentrations, and hematuria and results of 1 or both of the microalbuminuria assays. CONCLUSIONS AND CLINICAL RELEVANCE: Microalbuminuria was associated with underlying disease. The sensitivity and specificity of the semiquantitative microalbuminuria test for detection of systemic disease were superior to those of other tests. Microalbuminuria testing in conjunction with other screening procedures may increase diagnosis of subclinical disease, but a prospective study in which the predictive values of screening tests are evaluated, with and without microalbuminuria determination, is needed.  相似文献   
102.
A 6-year-old multiparous Holstein cow was admitted for evaluation of progressive milk flow obstruction of one quarter of the udder. Physical examination findings suggested the presence of a mural teat abscess. Ultrasonography substantiated the physical examination findings and delineated the extent of the lesion. Surgical excision of the abscess en bloc yielded satisfactory functional and cosmetic results.  相似文献   
103.
104.
全球禽肉生产和贸易中的沙门菌风险评估与控制   总被引:1,自引:0,他引:1  
1 禽源沙门菌对公共卫生的影响 在许多国家,沙门菌仍是引发食源性肠道疾病的主要原因.沙门菌通常存在于家畜、家禽中,也可在啮齿类、爬行类和鸟类等野生动物中发现.当农场的禽群感染沙门菌后,通常会有一部分家禽的消化道中携带沙门菌,但并无症状.随后,沙门菌可能会通过粪便污染感染动物屠体.  相似文献   
105.
编者按:在家禽养殖中,饲料是支撑家禽生长的最基本元素.除去营养需要外,高度加工处理的饲料从一开始着眼于提高家禽的生产性能,以达到效率最优化.  相似文献   
106.
The aim of this study was to compare the development of Glasser's disease in sow-reared and colostrum-deprived piglets. Ninety piglets from a commercial pig farm in Spain were used. The farm was positive for Haemophilus parasuis. Fifty-two pigs were sow-reared (SR) and 38 were colostrum-deprived (CD) piglets. The animals were intratracheally inoculated with H. parasuis serovar 5 and sacrificed at 1, 2 and 3 days post-infection. To assess the development of disease, antibody titers, clinical signs, pathological lesions, microbiological isolation and PCR amplification were compared between the groups. Inoculation of SR pigs did not cause clinical signs or lesions of Glasser's disease. In SR pigs, H. parasuis isolation and specific PCR amplification from tissues showed a very low number of positive samples. In contrast, in CD pigs, inoculation resulted in the typical signs and lesions of Glasser's disease. Positive microbiological isolation and specific PCR products were obtained from the majority of the tissues tested, and no antibodies against H. parasuis were detected. The experimental infection using CD pigs describes a successful method to study this microorganism and confirms the important role that maternal antibodies play in protection against clinical signs and disease.  相似文献   
107.
A survey of aldicarb poisoning in companion animals was conducted by posting questionnaires to all private practitioners in Gauteng Province, South Africa. The survey was designed to determine the percentage of aldicarb cases seen, treatment regimen, clinical signs observed, proposals for preventative actions and more effective treatments. Other questions included duration of treatment, survival rate, cost to clients, post mortem findings and reasons for poisonings.  相似文献   
108.
109.
110.
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