全文获取类型
收费全文 | 62506篇 |
免费 | 3580篇 |
国内免费 | 47篇 |
专业分类
林业 | 3244篇 |
农学 | 2431篇 |
基础科学 | 394篇 |
8070篇 | |
综合类 | 7105篇 |
农作物 | 2256篇 |
水产渔业 | 3361篇 |
畜牧兽医 | 34749篇 |
园艺 | 825篇 |
植物保护 | 3698篇 |
出版年
2019年 | 551篇 |
2018年 | 1030篇 |
2017年 | 1122篇 |
2016年 | 1070篇 |
2015年 | 915篇 |
2014年 | 1078篇 |
2013年 | 2490篇 |
2012年 | 1950篇 |
2011年 | 2395篇 |
2010年 | 1591篇 |
2009年 | 1511篇 |
2008年 | 2210篇 |
2007年 | 2190篇 |
2006年 | 2077篇 |
2005年 | 1929篇 |
2004年 | 1810篇 |
2003年 | 1780篇 |
2002年 | 1682篇 |
2001年 | 2428篇 |
2000年 | 2286篇 |
1999年 | 1810篇 |
1998年 | 731篇 |
1997年 | 654篇 |
1996年 | 636篇 |
1995年 | 704篇 |
1994年 | 613篇 |
1993年 | 610篇 |
1992年 | 1330篇 |
1991年 | 1462篇 |
1990年 | 1520篇 |
1989年 | 1394篇 |
1988年 | 1281篇 |
1987年 | 1284篇 |
1986年 | 1210篇 |
1985年 | 1156篇 |
1984年 | 972篇 |
1983年 | 771篇 |
1982年 | 574篇 |
1979年 | 830篇 |
1978年 | 657篇 |
1977年 | 510篇 |
1976年 | 560篇 |
1975年 | 533篇 |
1974年 | 662篇 |
1973年 | 635篇 |
1972年 | 664篇 |
1971年 | 632篇 |
1970年 | 611篇 |
1969年 | 572篇 |
1967年 | 522篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
271.
272.
273.
K Doll 《Tier?rztliche Praxis》1991,19(1):44-47
The impairment of fluid, electrolyte and acid-base status which is observed in calves and juvenile cattle as a result of ileus and subileus is not only dependent on form and site of the obstruction, but is also influenced considerably by the duration of the condition and any coexisting disease. This publication reviews the most important blood, urine and ruminal fluid parameters in such patients. The diagnostic significance of the laboratory values under discussion is not so great with obstructions to the caudal part of the digestive tract. However, markedly raised ruminal fluid chloride levels, combined with hypochloraemia and a metabolic acidosis, are indicative of an "abomasoruminal reflux syndrome" resulting from an obstruction in the region of the abomasum or cranial small intestine. 相似文献
274.
Prins B Loewen KG 《The Canadian veterinary journal. La revue veterinaire canadienne》1991,32(8):487-491
The results of laboratory examination of 20460 specimens for the diagnosis of rabies by the standard fluorescent antibody and mouse inoculation tests over a five year period are presented. Specimens were received from British Columbia, Alberta, Saskatchewan, Manitoba, and the Yukon and Northwest Territories. Of those examined, 9.96% were positive. The main reservoirs of rabies were skunks, bats, and foxes. During this observation period a rabies epizootic occurred in skunks in Saskatchewan. When both tests were performed, the fluorescent antibody test was found to agree with the mouse inoculation test in over 99% of cases. 相似文献
275.
Efficacy of parenteral antibiotics for disease prophylaxis in feedlot calves 总被引:9,自引:9,他引:0
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Harland RJ Jim GK Guichon PT Townsend HG Janzen ED 《The Canadian veterinary journal. La revue veterinaire canadienne》1991,32(3):163-168
Trimethoprim-sulfadoxine (TMPSDX) and two formulations of oxytetracycline (OTC) were examined for their prophylactic efficacy in feedlot calves when given by intramuscular injection on arrival at a large commercial feedlot. The study included 2,112 high-risk feeder calves that developed disease early in the feeding period. Both formulations of OTC reduced bovine respiratory disease morbidity during the first two weeks on feed and for the entire feeding period by 15-19% (p<0.05), and they also reduced all fatal fibrinous pneumonia by 67% and 84% (p<0.05). All three drugs significantly reduced all fatal disease in animals first treated during the second week on feed, but not for the overall feeding period. Oxytetracycline with 2-pyrrolidone reduced the incidence of all fatal disease by 44% (p<0.05) during the entire feeding period. The case fatality risk for calves first treated during the second week on feed was lower (p<0.05) in the TMPSDX group and in the OTC with polyvinyl-pyrrolidone group. 相似文献
276.
277.
278.
The processes involved in the dissolution and growth of crystals are closely related. Atomic force microscopy (AFM) of faceted pits (called negative crystals) formed during quartz dissolution reveals subtle details of these underlying physical mechanisms for silicates. In imaging these surfaces, the AFM detected ledges <1 nanometer (nm) high that were spaced 10 to 90 nm apart. A dislocation pit, invisible to optical and scanning electron microscopy measurements and serving as a ledge source, was also imaged. These observations confirm the applicability of ledge-motion models to dissolution and growth of silicates; coupled with measurements of dissolution rate on facets, these methods provide a powerful tool for probing mineral surface kinetics. 相似文献
279.
The atomic force microscope (AFM) was used to image an electrode surface at atomic resolution while the electrode was under potential control in a fluid electrolyte. A new level of subtlety was observed for each step of a complete electrochemical cycle that started with an Au(111) surface onto which bulk Cu was electrodeposited. The Cu was stripped down to an underpotential-deposited monolayer and finally returned to a bare Au(111) surface. The images revealed that the underpotential-deposited monolayer has different structures in different electrolytes. Specifically, for a perchloric acid electrolyte the Cu atoms are in a close-packed lattice with a spacing of 0.29 +/- 0.02 nanometer (nm). For a sulfate electrolyte they are in a more open lattice with a spacing of 0.49 +/- 0.02 nm. As the deposited Cu layer grew thicker, the Cu atoms converged to a (111)-oriented layer with a lattice spacing of 0.26 +/- 0.02 nm for both electrolytes. A terrace pattern was observed during dissolution of bulk Cu. Images were obtained of an atomically resolved Cu monolayer in one region and an atomically resolved Au substrate in another in which a 30 degrees rotation of the Cu monolayer lattice from the Au lattice is clearly visible. 相似文献
280.