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   2884篇
  免费   194篇
  国内免费   4篇
林业   198篇
农学   70篇
基础科学   22篇
  486篇
综合类   701篇
农作物   62篇
水产渔业   241篇
畜牧兽医   1018篇
园艺   90篇
植物保护   194篇
  2023年   20篇
  2022年   23篇
  2021年   66篇
  2020年   77篇
  2019年   91篇
  2018年   81篇
  2017年   77篇
  2016年   89篇
  2015年   71篇
  2014年   79篇
  2013年   108篇
  2012年   192篇
  2011年   225篇
  2010年   147篇
  2009年   97篇
  2008年   224篇
  2007年   214篇
  2006年   198篇
  2005年   191篇
  2004年   194篇
  2003年   184篇
  2002年   177篇
  2001年   31篇
  2000年   21篇
  1999年   20篇
  1998年   9篇
  1997年   7篇
  1996年   9篇
  1995年   14篇
  1994年   12篇
  1993年   9篇
  1992年   5篇
  1991年   11篇
  1990年   6篇
  1989年   10篇
  1988年   6篇
  1987年   10篇
  1986年   7篇
  1985年   8篇
  1984年   4篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1976年   5篇
  1974年   8篇
  1973年   3篇
  1970年   3篇
  1968年   2篇
  1961年   2篇
  1957年   2篇
排序方式: 共有3082条查询结果,搜索用时 46 毫秒
991.
992.
20世纪90年代在英国出现新的猪病如PMWS/PDNS,迫使人们开始重新评估现有的生产系统,疫苗已经不能解决所有问题,养猪场必须采用改进管理方法来控制疾病。如PRRS,离开了综合饲养管理,疫苗仍然不起作用。本文涵盖各种控制疾病的基本饲养管理方法,每个场则须针对各自情况采用合适的方法。  相似文献   
993.
Abstract: Aggregation of feline platelets in vitro results in difficulty assessing platelet number. A citrate-based anticoagulant containing the platelet inhibitors theophylline, adenosine, and dipyridamole (CTAD; Diatube-H, Becton Dickinson, Oxford, UK) has been developed for use in human platelet studies and heparin assays. To evaluate the efficacy of CTAD in reducing platelet aggregation in feline blood samples, aliquots of blood from 51 cats were anticoagulated with EDTA, CTAD, and for 12 samples, citrate solution. Samples preserved in CTAD had significantly higher (P ≤ .001) platelet counts, as determined by an impedance counter, hemacy-tometer, and smear estimation, than samples preserved in EDTA. In addition, subjective assessment of blood smears showed significantly fewer platelet aggregates (P<.001) in CTAD-treated samples compared with EDTA samples. Although values were similar, automated platelet counts and smear estimates of platelet number were significantly higher (P < .05) and platelet aggregation was significantly less (P < .05) in CTAD samples than in citrate samples. These results suggest that the platelet inhibitory activity of CTAD reduced feline platelet aggregation. Automated total WBC counts in CTAD samples were significantly lower (P<.001) than automated counts in EDTA samples but were similar to manual WBC counts in EDTA samples. Differences in both platelet and WBC counts between CTAD and EDTA or citrate samples were clinically relevant. Mean platelet volume and MCV were significantly lower (P< .05) in CTAD samples than in EDTA samples. No effect was seen on cell morphology or staining characteristics. The anticoagulant CTAD offers an advantage over both EDTA and citrate for feline hematologic analysis, by decreasing pseudothrombocytopenia and pseudoleukocytosis.  相似文献   
994.
995.
996.
997.
998.
OBJECTIVE: To quantitate the density of Dermatophagoides farinae and D pteronyssinus and concentrations of house dust mite (HDM) allergens (Der f 1, Der p 1, and Group 2 allergens) in the indoor microenvironment of dogs. Sample Population-50 homes in Columbus, Ohio. PROCEDURES: n each home, samples of dust were collected from 3 locations in which dogs spent most time. Whenever possible, the species of mites collected was identified. Mite density (mites/g of dust) was assessed, and allergen concentrations were assayed by standardized ELISAs. Relative humidity and temperature in each home were monitored during a 5-day period. Characteristics of homes and sample sources were evaluated. RESULTS: Dust samples from all 50 homes contained > or = 1 HDM allergen; Der f 1 and Der p 1 were detected in 100 and 74% of homes, respectively. Fifteen homes had HDMs; compared with D pteronyssinus, D farinae was found more commonly (14/15 homes) and at a higher density. Basements, homes without central air-conditioning, and dog beds that were > or = 1 year old had high HDM allergen concentrations. Homes with > or = 2 microg of Der f 1 or Group 2 allergens/g of dust or > or = 100 mites/g of dust were significantly more likely to have a maximum relative humidity > or = 75%. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate the presence of HDMs and HDM allergens in the specific microenvironment of dogs in homes. Factors associated with high levels of exposure were identified, which may be associated with increased risk for sensitization and development of atopic diseases.  相似文献   
999.
OBJECTIVE: To compare pathologic findings and results of adrenalectomy for adrenal gland tumors in dogs with and without vena caval tumor thrombi. DESIGN: Retrospective study. ANIMALS: 40 dogs with adrenal gland tumors. PROCEDURE: Medical records were examined. An exact logistic regression analysis was used to evaluate associations between tumor type or right-sided versus left-sided tumor involvement and development of caval tumor thrombi and associations between tumor thrombi, tumor type, or right- versus left-sided location and perioperative complications and mortality rate. Survival was compared between dogs with and without tumor thrombi. RESULTS: Caval thrombi were detected in 25% of dogs, including 3 of 28 (11%) dogs with an adrenocortical tumor and 6 of 11 dogs with a pheochromocytoma. A caval tumor thrombus was detected in 6 of 17 right-sided and 4 of 20 left-sided tumors. Sensitivity and specificity of abdominal ultrasonography for detection of caval thrombi were 80 and 90%, respectively. Intraoperative and postoperative complications developed in 15 and 51% of dogs, respectively. The mortality rate was 22%. There were no significant differences in perioperative morbidity and mortality rates between dogs with and without tumor thrombi. CONCLUSIONS AND CLINICAL RELEVANCE: Caval thrombi associated with adrenal gland tumors are amenable to adrenalectomy and thrombectomy without significantly increased perioperative morbidity and mortality rates, assuming the surgeon is experienced in appropriate techniques.  相似文献   
1000.
OBJECTIVE: To assess the ability of a porcine submucosal collagen patch to enhance ventriculotomy healing in quail. STUDY DESIGN: Histologic assessment of wound repair after ventriculotomy. Animal Population-Eighteen adult Japanese quail. METHODS: All quail had a ventriculotomy through the caudoventral thin muscle. The quail were randomly assigned to 1 of 2 groups: group I (n = 9) had routine closure and group II (n = 9) had routine closure and the application of a porcine submucosal collagen patch over the serosal surface of the ventricular suture line. Three quail from each group underwent necropsy at 7, 14, and 21 days after surgery and healing of the ventriculotomy site was evaluated by microscopy. RESULTS: Ventricular mucosal epithelium was completely healed at 21 days postoperatively. Time to restoration of the ventricular submucosal integrity was variable in both groups. There was evidence of a gross or microscopic perforation in 4 quail in group II, which was statistically significant (P =.041). Quail with perforations had significantly elevated numbers of ventricular serosal lymphoid aggregates compared with those without perforations (P =.029). There were no other significant temporal differences between group I and group II for mortality or histopathologic grading of wound healing. CONCLUSIONS: A porcine collagen patch did not enhance ventriculotomy wound healing. Subjectively, the collagen patch might have contributed to perforation by the generation of a lymphocytic xenograft rejection response. CLINICAL RELEVANCE: Ventriculotomy can be safely performed using routine closure methods in healthy birds.  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