全文获取类型
收费全文 | 5561篇 |
免费 | 226篇 |
国内免费 | 14篇 |
专业分类
林业 | 401篇 |
农学 | 233篇 |
基础科学 | 39篇 |
660篇 | |
综合类 | 580篇 |
农作物 | 214篇 |
水产渔业 | 218篇 |
畜牧兽医 | 3035篇 |
园艺 | 45篇 |
植物保护 | 376篇 |
出版年
2019年 | 45篇 |
2018年 | 68篇 |
2017年 | 102篇 |
2016年 | 87篇 |
2015年 | 58篇 |
2014年 | 81篇 |
2013年 | 206篇 |
2012年 | 158篇 |
2011年 | 179篇 |
2010年 | 112篇 |
2009年 | 123篇 |
2008年 | 221篇 |
2007年 | 214篇 |
2006年 | 183篇 |
2005年 | 205篇 |
2004年 | 180篇 |
2003年 | 185篇 |
2002年 | 174篇 |
2001年 | 205篇 |
2000年 | 199篇 |
1999年 | 185篇 |
1998年 | 54篇 |
1997年 | 73篇 |
1996年 | 66篇 |
1995年 | 57篇 |
1994年 | 47篇 |
1993年 | 63篇 |
1992年 | 127篇 |
1991年 | 136篇 |
1990年 | 135篇 |
1989年 | 138篇 |
1988年 | 108篇 |
1987年 | 122篇 |
1986年 | 103篇 |
1985年 | 97篇 |
1984年 | 93篇 |
1983年 | 67篇 |
1982年 | 39篇 |
1979年 | 81篇 |
1978年 | 63篇 |
1977年 | 73篇 |
1976年 | 46篇 |
1975年 | 69篇 |
1974年 | 85篇 |
1973年 | 74篇 |
1972年 | 75篇 |
1971年 | 56篇 |
1970年 | 70篇 |
1969年 | 51篇 |
1968年 | 44篇 |
排序方式: 共有5801条查询结果,搜索用时 15 毫秒
81.
Effect of postural changes on certain circulatory and respiratory values in the horse 总被引:4,自引:0,他引:4
U Schatzmann M Koehli F Dudan W Rohr R S Jones 《American journal of veterinary research》1982,43(6):1003-1005
Certain circulatory and respiratory values were measured in horses in the standing, lateral, and supine positions. Twelve adult horses were kept in the standing position under the influence of glycerol guiacolate. Alterations in position to lateral and dorsal recumbencies were achieved without any further drug administration. The changes from the standing to the lateral position decreased the arterial oxygen tension, but left the arterial carbon dioxide tension unchanged. There was no statistically significant effect of body position on respiratory flow rates or volumes. The shift from the lateral position to the supine position had no statistically significant effect on any of the measured values. It is assumed that the change from the standing to the lateral position results in an increase in ventilation of the uppermost parts of the lung. The perfusion inequalities are due mainly to the effect of gravity of the pulmonary circulation which may result in a decrease in arterial oxygen tension. 相似文献
82.
Wijkstrom UN 《Veterinary research communications》2003,27(Z1):461-468
If real prices for fish remain at the levels they had attained by 1999, in the year 2050 demand for fish and shellfish as food could be of the order of 270 million tons (live weight equivalent) per year. If producers were able to supply these quantities consumption would rise by 176% over this 50-year period. To meet the demand supply would have to expand at the rate of 2.1% annually; but, a review of the pattern of population growth--and of historical patterns of increases in per capita consumption of fish--shows that annual growth in the volume of fish demanded is likely to be largest in the coming two decades, and then to taper off. Will producers be able to deliver? It is clear that wild marine stocks at present harvested by capture fishermen cannot support fisheries that would yield much more than 100 million tons per year and of this amount a significant proportion will continue to be used for fish meal and oil production. The question therefore narrows down to: can aquaculture, or non-traditional marine species, supply the required amounts? The historical context of supply is considerably different from that which has prevailed during the past 30 years. At that time the growing demand in OECD countries was met partly through imports of fish produced in the seas and lakes of developing countries. During coming decades the increased demand in developing countries must be met essentially through their own resources. In fact, in poor countries it seems unlikely that supply will respond to demand unless they experience economic growth. 相似文献
83.
84.
In a consecutive and non-selected study of 54 kidney transplanted dogs, 12 cases of intussusception of the small intestine developed in 8 dogs. The patogenesis is still unknown. It has been postulated that the time of the operation (4--7 hours) and the segmental termination of the post-operative atony in the intestine are essential factors in this fatal complication. The last 16 dogs in this material were peroperatively treated with antikolinergics (Mestinon NFN), which was continued until normal function of the intestine. In these dogs there were no evidence of intussusception. The value of this profylaxis is open to discussion and it is essential to solve the problem of intussusception through a "blind" and controlled trial. 相似文献
85.
86.
87.
An account is given of various techniques of blood sampling in the context of certain mustelids, including cardiopuncture, amputation of tail tip, talon cutting, incision of the ear vein, puncture of the jugular or femoral vein, and catheterisation of the abdominal aorta. Reference is made to details of use of all techniques, characteristics, advantages and potential setbacks, and preferable use of some of the tested methods to collect blood from mustela and martes species. Blood collection from the abdominal aorta may be helpful in obtaining no-haemolysis and no-additive plasma for biochemical multi-screening. Biochemical, pharmacological, and toxicological follow-up checks may be feasible under certain conditions following surgical exposure of the external jugular vein. The use of "Fimomed" (n-butylcyano-acrylate), a tissue adhesive, may help to reduce effort in terms of time and material and consequently, rationalise veterinary hygiene action as a whole, provided that the conditions for its application are observed. The skin adhesive is properly applicable to skin lesions of mustelids. A combination of suturing with adhesive should be used to close laparotomy wounds for better mechanical strength of the abdominal wall. Possible applications of "Fimomed" should be tested with other species as well. 相似文献
88.
89.
Pees MC Kiefer I Ludewig EW Schumacher JP Krautwald-Junghanns ME Oechtering GU 《American journal of veterinary research》2007,68(4):428-434
OBJECTIVE: To evaluate the use of computed tomography (CT) for detection of pneumonia in snakes. ANIMALS: 8 clinically normal Indian pythons (Python molurus) and 5 pythons with evidence of respiratory tract disease. PROCEDURES: Preliminary examinations (clinical examination, conventional radiography, and microbiologic examination of a transtracheal wash sample) were performed. The lungs of each snake were then examined by use of CT performed in accordance with a standardized protocol. Structures of the lungs were assessed, and thickness and attenuation of the parenchyma were determined. RESULTS: It was possible to assess lung parenchyma in all pythons. Mean +/- SD attenuation in healthy pythons was -744.4 +/- 47.1 Hounsfield units. Significant differences were not evident between the right and left lungs or among measurement areas within a lung. In all Indian pythons with clinical signs of dyspnea and microbiologic detection of pathogens, hyperattenuation of the alveolar tissue was evident. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the results revealed the benefit of CT for use in the diagnosis of pneumonia in snakes. A standardized protocol and reference values were established as a basis for CT assessment of the lungs of snakes. 相似文献
90.
Ivermectin (IVM- Eqvalan paste, 1.87%) and doramectin (DRM-Dectomax 1%) were each administered orally to donkeys at 200 microgkg(-1) bodyweight. Blood and faecal samples were collected at predetermined times over 30 days and plasma pharmacokinetics and faecal excretion determined. Maximum plasma concentrations (C(max)) of IVM (23.6 ngml(-1)) and DRM (33.9 ngml(-1)) were obtained at (t(max)) 19.2 and 24h, respectively. The area under the concentration curve (AUC) of DRM (228.9 ngdayml(-1)) was significantly larger than that of IVM (119.3 ngdayml(-1)) and mean residence time (MRT) was 6.5 days for IVM and 9.1days for DRM. The highest (dry weight) faecal concentrations (9.33 microgg(-1) - IVM, 12.12 microgg(-1) - DRM) were detected at 55.9 and 48.0 h, respectively and each compound was detected (0.05 microgg(-1)) in faeces between 11h and 9 days following oral administration in donkeys. 相似文献