全文获取类型
收费全文 | 2931篇 |
免费 | 184篇 |
国内免费 | 4篇 |
专业分类
林业 | 198篇 |
农学 | 70篇 |
基础科学 | 22篇 |
490篇 | |
综合类 | 701篇 |
农作物 | 65篇 |
水产渔业 | 238篇 |
畜牧兽医 | 1028篇 |
园艺 | 91篇 |
植物保护 | 216篇 |
出版年
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 | 213篇 |
2006年 | 198篇 |
2005年 | 190篇 |
2004年 | 194篇 |
2003年 | 184篇 |
2002年 | 177篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 18篇 |
1995年 | 15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 | 2篇 |
1961年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有3119条查询结果,搜索用时 15 毫秒
71.
Lawler A 《Science (New York, N.Y.)》2003,299(5613):1653-1654
72.
Adin CA Herrgesell EJ Nyland TG Hughes JM Gregory CR Kyles AE Cowgill LD Ling GV 《Journal of the American Veterinary Medical Association》2003,222(11):1576-1581
OBJECTIVE: o determine sensitivity and specificity of radiography, ultrasonography, and antegrade pyelography for detection of ureteral obstructions in cats. DESIGN: Retrospective study. ANIMALS: 11 cats. PROCEDURE: Medical records of cats that had radiography, ultrasonography, and antegrade pyelography performed for suspected ureteral obstructions were examined. Ultrasound-guided pyelocentesis and fluoroscopic-assisted antegrade pyelography were performed on 18 kidneys in 11 cats. Obstructive ureteral lesions were confirmed in all cats by surgical or necropsy examination. Sensitivity and specificity of survey radiography, ultrasonography, and antegrade pyelography for identification of ureteral obstructions were calculated. Surgical or necropsy findings were used as the standard for comparison. RESULTS: All cats were azotemic. Mean +/- SD serum creatinine and BUN concentrations were 10.2 +/- 6.1 and 149 +/- 82 mg/dL, respectively. Fifteen of 18 ureters were found to be obstructed at surgery or necropsy. Sensitivity and specificity were 60 and 100% for radiography and 100 and 33% for ultrasonography, respectively, in identification of ureteral obstructions. Leakage of contrast material developed in 8 of 18 kidneys during antegrade pyelography and prevented diagnostic interpretation in 5 of 18 studies. For the 13 diagnostic studies, specificity and sensitivity were 100% by use of the antegrade pyelography technique. Correct identification of the anatomic location of the ureteral obstruction was obtained in 100% of diagnostic antegrade pyelography studies and in 60% of radiography or ultrasonography studies. CONCLUSIONS AND CLINICAL RELEVANCE: Antegrade pyelography can be a useful alternative in the diagnosis and localization of ureteral obstructions in azotemic cats, although leakage of contrast material may prevent interpretation of the study. 相似文献
73.
Cazabon EP Adogwa AO 《The Canadian veterinary journal. La revue veterinaire canadienne》2003,44(1):56-58
A case of cephalothoracopagus in sheep complicated with several defects of skeletal, cardiovascular, respiratory, gastrointestinal, and urogenital systems is reported. 相似文献
74.
75.
Evaluation of various compounds to inhibit activity of matrix metalloproteinases in the tear film of horses with ulcerative keratitis 总被引:1,自引:0,他引:1
Ollivier FJ Brooks DE Kallberg ME Komaromy AM Lassaline ME Andrew SE Gelatt KN Stevens GR Blalock TD van Setten GB Schultz GS 《American journal of veterinary research》2003,64(9):1081-1087
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
76.
77.
Nawrocki MA Mackin AJ McLaughlin R Cantwell HD 《Journal of the American Animal Hospital Association》2003,39(3):257-261
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
78.
79.
Lawler A 《Science (New York, N.Y.)》2002,296(5575):1950-1951
80.
Kyles AE Hardie EM Mehl M Gregory CR 《Journal of the American Veterinary Medical Association》2002,220(9):1341-1347
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