全文获取类型
收费全文 | 82349篇 |
免费 | 5062篇 |
国内免费 | 771篇 |
专业分类
林业 | 3156篇 |
农学 | 2519篇 |
基础科学 | 685篇 |
9843篇 | |
综合类 | 16453篇 |
农作物 | 3043篇 |
水产渔业 | 3794篇 |
畜牧兽医 | 42605篇 |
园艺 | 1129篇 |
植物保护 | 4955篇 |
出版年
2021年 | 724篇 |
2020年 | 802篇 |
2019年 | 984篇 |
2018年 | 1356篇 |
2017年 | 1566篇 |
2016年 | 1385篇 |
2015年 | 1324篇 |
2014年 | 1507篇 |
2013年 | 2911篇 |
2012年 | 2879篇 |
2011年 | 3466篇 |
2010年 | 2299篇 |
2009年 | 2174篇 |
2008年 | 3083篇 |
2007年 | 2969篇 |
2006年 | 2681篇 |
2005年 | 2603篇 |
2004年 | 2312篇 |
2003年 | 2360篇 |
2002年 | 2213篇 |
2001年 | 2492篇 |
2000年 | 2531篇 |
1999年 | 1948篇 |
1998年 | 795篇 |
1997年 | 709篇 |
1995年 | 746篇 |
1993年 | 666篇 |
1992年 | 1530篇 |
1991年 | 1720篇 |
1990年 | 1640篇 |
1989年 | 1597篇 |
1988年 | 1480篇 |
1987年 | 1532篇 |
1986年 | 1573篇 |
1985年 | 1401篇 |
1984年 | 1190篇 |
1983年 | 1018篇 |
1982年 | 681篇 |
1979年 | 1059篇 |
1978年 | 831篇 |
1977年 | 677篇 |
1976年 | 711篇 |
1975年 | 750篇 |
1974年 | 1005篇 |
1973年 | 986篇 |
1972年 | 954篇 |
1971年 | 883篇 |
1970年 | 857篇 |
1969年 | 809篇 |
1967年 | 704篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
The effects of feeding milk to diarrheic calves supplemented with oral electrolytes. 总被引:1,自引:3,他引:1 下载免费PDF全文
S E Heath J M Naylor B L Guedo L Petrie C G Rousseaux O M Radostits 《Canadian journal of veterinary research》1989,53(4):477-485
The effects of feeding different levels of milk to diarrheic calves (n = 19) supplemented with oral electrolytes were investigated. In the early stages of the disease the calves were fed either enough milk to maintain normal growth in a healthy calf, one half that volume or no milk. The three groups were further subdivided according to whether or not the electrolyte solution contained bicarbonate. A full milk ration allowed uninterrupted weight gains of 1% body weight/day (p = 0.003), but caused greater inappetence (p = 0.003 to 0.037) at the beginning of the trial than lower levels of milk intake. Electrolyte solutions with bicarbonate reduced growth rates in milk fed calves (p = 0.014). The density of fat stores increased with the level of milk feeding (p = 0.04 to 0.053). The mitotic index of the duodenal mucosa increased with milk feeding (p = 0.08), indicating a superior mucosal regeneration potential. Thymic atrophy was pronounced in those calves fed no milk (p = 0.001). It was concluded that the continued feeding of milk to diarrheic calves was beneficial. Electrolyte solutions containing bicarbonate should be avoided when milk is fed to diarrheic calves. 相似文献
992.
Enzyme-linked immunosorbent assay for the detection of circulating antigens of Toxoplasma gondii in the serum of cats 总被引:1,自引:0,他引:1
M R Lappin C E Greene A K Prestwood D L Dawe R L Tarleton 《American journal of veterinary research》1989,50(9):1586-1590
An ELISA was developed to detect circulating antigens of Toxoplasma gondii in the serum of cats. For the experiment, toxoplasmosis was induced in a group of cats by oral administration of bradyzoites. An ELISA that detects anti-Toxoplasma IgG, an ELISA to detect circulating antigens, and fecal examinations were performed on samples from each cat for 1 year after inoculation. When coupled with IgG-class antibody measurement, antigen detection can aid in the diagnosis of some cases of subclinical feline toxoplasmosis. 相似文献
993.
994.
995.
996.
Studies on some digestive enzymes in swine gastroenteritis 总被引:1,自引:0,他引:1
997.
Experimental Hemorrhagic Septicemia: Gross and Microscopic Lesions Resulting from Acute Infections and from Endotoxin Administration 总被引:1,自引:0,他引:1 下载免费PDF全文
Keith R. Rhoades Kenneth L. Heddleston Paul A. Rebers 《Canadian journal of veterinary research》1967,31(9):226-233
Gross and microscopic lesions observed in bovine and porcine hemorrhagic septicemia, and in bovine Pasteurella multocida endotoxemia are described. Widely distributed hemorrhages, edema, and general hyperemia were the most obvious tissue changes observed in the infected calves. Pneumonia was a constant lesion. Aerosol exposure produced a multiple focal fibrinosuppurative pneumonia, while intranasal and intramuscular inoculation resulted in generalized interstitial pneumonia. A slight lymphadenitis and degenerative changes in hepatic and renal parenchymal cells were also observed.
The predominant lesions observed in infected pigs were a diffuse, extensive, fibrinous pneumonia and fibrinous polyserositis. Edema and general hyperemia were observed, but the widespread hemorrhages which occurred in the calves were not present. Acute lymphadenitis and renal tubule vacuolar degeneration were observed. A slight amount of cloudy swelling and focal areas of necrosis were found in the liver.
Lesions in a calf that died following administration of Past. multocida endotoxin were widely distributed hemorrhages, edema, and general hyperemia. These lesions were especially evident in the lungs, and indicated widespread vascular alteration.
相似文献998.
999.
L. Ferasin L. Crews D.S. Biller K.E. Lamb M. Borgarelli 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2013,27(2):286-292
Background
Cough often is reported as the primary clinical sign of congestive heart failure (CHF) in dogs with chronic degenerative myxomatous mitral valve disease (MMVD). Concurrent airway disease and compression of the left mainstem bronchus by a large left atrium also have been proposed as potential causes of coughing in these patients.Objectives
To investigate the association between the presence of coughing and different potential causes of cough, including CHF, abnormal radiographic airway pattern, and cardiomegaly in dogs affected by naturally acquired MMVD.Animals
Two hundred six client‐owned dogs.Methods
Retrospective analysis performed on medical records of dogs affected by MMVD that underwent full cardiac evaluation, including echocardiographic examination and thoracic radiography.Results
Univariate analyses showed that CHF is not a predictor of coughing (OR = 1.369; 0.723, 2.594), whereas abnormal radiographic airway pattern (OR = 3.650; 2.051, 6.496) and increased left atrial size observed radiographically (OR = 3.637; 1.904, 6.950) or echocardiographically (OR = 2.553; 1.436, 4.539) were significantly associated with coughing in dogs with MMVD. The same risk factors were significant in multivariate analyses.Conclusions and Clinical Importance
This study indicates that CHF is not significantly associated with coughing in dogs with MMVD. Instead, abnormal radiographic airway pattern and left atrial enlargement are associated with coughing in these patients. This important finding should be taken into account when considering diagnosis and clinical management of CHF in these dogs. 相似文献1000.
A. Vlassoff Jennifer M. Ayling L.W. McMurtry Shona J. Smith A.J. Watson 《New Zealand veterinary journal》2013,61(6):79-81
Forty-three randomly selected farms located throughout South Island, excluding the Nelson region, were surveyed for anthelmintic usage and for sheep nematodes resistant to anthelmintics. Most farmers had used both benzimidazole and non-benzimidazole broad-spectrum drenches on their properties in previous years. Sheep were being drenched, on average, 5.6 times within their first year of life but much less frequently thereafter. Commercial interests played the dominant role in helping farmers formulate their drenching policies. On each farm 24 numbered ewe replacement lambs, born during the spring of 1980, were sampled for faeces at the beginning of the trial to provide material for egg counts and larval cultures. The lambs were weighed and divided into three groups of eight. One group received thiabendazole (TBZ) at 66 mg/kg, the second levamisole (LEV) at 8 mg/kg while the third remained untreated as controls. All were resampled 4 to 10 days later. On 32 (88%) of the 40 farms where drenching trials were successfully carried out during autumn 1981, the faecal egg count depression (FECD) following treatment with either drench was 100%. On one farm TBZ was less than 100% effective as gauged by FECD. LEV proved to be less than 100% effective on 7 farms. On one farm the FECD was less than 80%, on 2 between 90% and 95% and on 4 between 95% and 99%. 相似文献