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   2951篇
  免费   184篇
  国内免费   4篇
林业   199篇
农学   70篇
基础科学   22篇
  490篇
综合类   711篇
农作物   65篇
水产渔业   238篇
畜牧兽医   1038篇
园艺   90篇
植物保护   216篇
  2024年   8篇
  2023年   20篇
  2022年   30篇
  2021年   71篇
  2020年   77篇
  2019年   91篇
  2018年   80篇
  2017年   77篇
  2016年   89篇
  2015年   69篇
  2014年   79篇
  2013年   108篇
  2012年   192篇
  2011年   225篇
  2010年   146篇
  2009年   97篇
  2008年   224篇
  2007年   215篇
  2006年   198篇
  2005年   190篇
  2004年   198篇
  2003年   184篇
  2002年   179篇
  2001年   33篇
  2000年   24篇
  1999年   29篇
  1998年   16篇
  1997年   7篇
  1996年   18篇
  1995年   14篇
  1994年   12篇
  1993年   9篇
  1992年   6篇
  1991年   11篇
  1990年   6篇
  1989年   10篇
  1988年   6篇
  1987年   10篇
  1986年   8篇
  1985年   11篇
  1984年   4篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1976年   5篇
  1975年   3篇
  1974年   8篇
  1973年   3篇
  1961年   2篇
  1957年   2篇
排序方式: 共有3139条查询结果,搜索用时 15 毫秒
101.
A case of cephalothoracopagus in sheep complicated with several defects of skeletal, cardiovascular, respiratory, gastrointestinal, and urogenital systems is reported.  相似文献   
102.
103.
OBJECTIVE: To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. SAMPLE POPULATION: Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. PROCEDURE: Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% alpha1-proteinase inhibitor (PI), 0.5% alpha1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples. RESULTS: Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% alpha1-PI, 93.6% by 0.5% alpha1-PI, and 90.0% by ES. CONCLUSIONS AND CLINICAL RELEVANCE: We documented that EDTA, doxycycline, NAC, ilomostat, alpha1PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses.  相似文献   
104.
105.
A 10-month-old, intact male Chihuahua presented for a 7-month history of regurgitation and coughing. Survey radiographs revealed a soft-tissue opacity within the distal esophagus. A contrast study confirmed the presence of an esophagobronchial fistula. Endoscopic removal of foreign material within the esophagus allowed for visualization of an esophageal diverticulum. Bronchoscopic examination revealed the presence of an abnormal opening in a right caudal tertiary bronchus. Passage of a cardiac guidewire was accomplished, confirming the presence of the fistula and aiding its subsequent surgical removal.  相似文献   
106.
107.
108.
OBJECTIVE: To document the signalment; history; clinical signs; clinicopathologic, diagnostic imaging, and surgical findings; perioperative complications; and long-term clinical results of ameroid ring constrictor (ARC) placement on single extrahepatic portosystemic shunts (PSS) in cats. DESIGN: Retrospective study. ANIMALS: 23 cats treated with an ARC on a single extrahepatic PSS. PROCEDURE: An ARC was placed surgically around the PSS. Portal pressure was measured prior to ARC placement, with complete temporary PSS occlusion, and after ARC placement. Cats were scheduled for recheck transcolonic portal scintigraphy 8 to 10 weeks after surgery. Follow-up information was obtained by telephone interview with the owners. RESULTS: An ARC was successfully placed in 22 of 23 cats. Intraoperative complications, consisting of PSS hemorrhage, occurred in 2 cats. Mean (+/- SD) portal pressure (n = 15) was 6.7+/-2.9 mm Hg before PSS manipulation, 18.6+/-7.7 mm Hg with complete temporary PSS occlusion, and 6.9+/-2.7 mm Hg after ARC placement. Postoperative complications developed in 77% (17 of 22) of cats after ARC placement, and included central blindness, hyperthermia, frantic behavior, and generalized motor seizures. Perioperative mortality rate was 4.3% (1 of 23). Persistent shunting was identified in 8 of 14 cats. Overall, 75% (15 of 20) of cats had an excellent long-term outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Placement of an ARC on single extrahepatic PSS in cats resulted in low surgical complication and perioperative mortality rates, but most cats did have substantial postoperative complications. Persistent shunting was common, although many cats with persistent shunting were clinically normal.  相似文献   
109.
Spinal deformities in farmed Atlantic salmon (Salmo salar) are often observed in intensive farming systems and result in production losses. Many putative factors have been implicated with the formation of spinal deformities in larger salmon. This condition has been described as broken back syndrome, curvy back disease, and short tails.  相似文献   
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