全文获取类型
收费全文 | 82561篇 |
免费 | 5149篇 |
国内免费 | 767篇 |
专业分类
林业 | 3188篇 |
农学 | 2504篇 |
基础科学 | 674篇 |
9949篇 | |
综合类 | 16434篇 |
农作物 | 3093篇 |
水产渔业 | 3790篇 |
畜牧兽医 | 42721篇 |
园艺 | 1149篇 |
植物保护 | 4975篇 |
出版年
2021年 | 753篇 |
2020年 | 821篇 |
2019年 | 1016篇 |
2018年 | 1377篇 |
2017年 | 1583篇 |
2016年 | 1403篇 |
2015年 | 1347篇 |
2014年 | 1521篇 |
2013年 | 2932篇 |
2012年 | 2908篇 |
2011年 | 3533篇 |
2010年 | 2325篇 |
2009年 | 2192篇 |
2008年 | 3103篇 |
2007年 | 2980篇 |
2006年 | 2679篇 |
2005年 | 2597篇 |
2004年 | 2317篇 |
2003年 | 2364篇 |
2002年 | 2213篇 |
2001年 | 2488篇 |
2000年 | 2529篇 |
1999年 | 1941篇 |
1998年 | 790篇 |
1997年 | 705篇 |
1995年 | 741篇 |
1993年 | 664篇 |
1992年 | 1526篇 |
1991年 | 1717篇 |
1990年 | 1645篇 |
1989年 | 1588篇 |
1988年 | 1473篇 |
1987年 | 1530篇 |
1986年 | 1574篇 |
1985年 | 1398篇 |
1984年 | 1192篇 |
1983年 | 1017篇 |
1982年 | 681篇 |
1979年 | 1056篇 |
1978年 | 829篇 |
1977年 | 673篇 |
1976年 | 712篇 |
1975年 | 746篇 |
1974年 | 1004篇 |
1973年 | 984篇 |
1972年 | 951篇 |
1971年 | 878篇 |
1970年 | 853篇 |
1969年 | 804篇 |
1967年 | 702篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Sean G. Sanders DVM Russell L. Tucker DVM Rodney S. Bagley DVM Patrick R. Gavin DVM PhD 《Veterinary radiology & ultrasound》2001,42(4):291-296
Magnetic resonance imaging (MR) was used to make a diagnosis of equine nigropallidal encephalomalacia in a horse. Equine nigropallidal encephalomalacia is a neurodegenerative disease that has many characteristics with Parkinson-like diseases in humans. Historically, horses were euthanized based on clinical signs and exposure to the toxic weed, yellow star thistle (Centaurea solstitialis). Previously, the disease has only been confirmed on necropsy. MR imaging can provide accurate and sensitive visualization of typical lesions seen in the brain of horses affected with equine nigropallidal encephalomalacia. Lesions were seen on T1-weighted, T2-weighted and proton density images. There was no contrast enhancement following Gd-DTPA administration. Lesions seen on MR were confirmed at necropsy. Using MR to confirm a diagnosis of equine nigropallidal encephalomalacia will prevent unnecessary suffering of horses and expense to owners that would otherwise incur, while further diagnostics are performed. 相似文献
73.
1. Eggs from wild and captive populations of Greater Rhea (Rhea americana) were studied to determine their physical and chemical characteristics. 2. Significant differences were found among populations in almost all chemical parameters studied, whereas within physical parameters only shell weight (as a proportion of the entire egg) and density showed differences. 3. Eggs from wild populations had the highest protein and linolenic acid and the lowest total lipid contents, while cholesterol levels of these eggs and of those from the largest captive area were the lowest. 相似文献
74.
75.
C. Avgoulas L. Bouza A. Koutrou S. Papadopoulou S. Kosmas E. Makridou P. Papastylianou D. Bilalis 《Journal of Agronomy and Crop Science》2005,191(1):1-9
Studies were conducted in four regions of central Greece (Larisa, Karditsa, Livadia, Thiva), to evaluate the productivity and fibre properties (fibre strength and fibre length) of the five most commonly grown cotton cultivars in these regions. The experiments lasted for 6 years (1995–2000). All the characteristics tested were strongly influenced by the factors ‘year’, ‘cultivar’ and ‘region’. Significant cultivar × region, year × cultivar, region × year and cultivar × region × year interactions occurred for all the characteristics studied. The cultivar Alegria had the highest seed‐cotton and lint yield, while Aria had the lowest ones. Both cultivars gave the highest mean lint percentage but the lowest mean boll weight (MBW). Alegria had the lowest fibre strength, while Aria had the highest. The Acala‐type cultivars, Acala SJ2 and Zeta 2, had intermediate seed‐cotton and lint yield, while Vered 171 had high seed‐cotton and satisfactory lint yield. The three cultivars mentioned above had the highest MBW and very good fibre strength. Positive correlation was observed between fibre strength and length. In spite of the fact that mean fibre length was statistically the same in all cultivars, it was influenced by the factor ‘year’, as a result of different weather conditions. The year 1996 was the most unfavourable one for seed‐cotton yield and MBW, because it was characterized by lower than average air temperatures and rather dry conditions for all study sites. The factor ‘region’, a combination of different climatic conditions and cultural practices, influenced significantly all the parameters studied. 相似文献
76.
77.
S. J. Delaney A. S. Hill R. C. Backus G. L. Czarnecki-Maulden & Q. R. Rogers 《Journal of animal physiology and animal nutrition》2001,85(3-4):88-100
The objective of the present study was to examine the interaction between graded levels of leucine and dietary crude protein. Dose–response curves were generated using four 3 × 3 Latin squares (two dogs/square). Each square represented one of two concentrations of crude protein (140 or 280 g/kg diet) and one of two combinations of three concentrations of leucine (5.0, 7.0 and 9.0 g/kg diet or 9.0, 11 and 13 g/kg diet). An additional experiment was performed by feeding crude protein at 210 g/kg diet with either 7.0 or 11 g leucine/kg diet. Weight gain, food intake, nitrogen retention, plasma albumin and plasma amino acids were measured. The requirement was determined to be the minimum leucine concentration required to maximize weight gain and nitrogen retention. For 8–14-week-old male Beagle dogs, 140 g crude protein/kg diet in a diet containing 18 kJ metabolizable energy/g does not appear to support maximal growth. The leucine requirement was not affected by doubling the dietary crude protein level from 140 to 280 g/kg diet. From these results, the leucine requirement of 8–14-week-old Beagle dogs appears to be 11 g leucine/kg diet independent of the level of dietary crude protein, whereas dogs over 14 weeks require only 7 g leucine/kg diet for maximal nitrogen retention. 相似文献
78.
79.
随着瘦肉生长率的提高 ,猪对氨基酸的需要量也增加了。能影响生产水平的一切因素都能影响猪对氨基酸的需要量 ,比如遗传、健康、温度 ,等等。在确定氨基酸需要量的时候对这些因素都应加以考虑。 相似文献
80.
Lack of effect of recombinant bovine interferon alpha I1 in the treatment of experimentally-induced bovine warts.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fifteen four-month old calves were inoculated, on five scarified sites on each side of the neck, with a suspension of ground wart tissue from a steer naturally infected with bovine papilloma virus 1. Warts started to appear about one month postinfection and were measurable in ten calves two months postinfection, when the trial started. After stratification on the size of the warts, all fifteen calves were allocated randomly to one of the following treatment groups: twice weekly intramuscular injections of 5 mg recombinant bovine interferon alpha I1 (rBoIFN alpha I1), weekly injection of 5 mg of rBoIFN alpha I1 or placebo, for three weeks. The biggest wart on each calf at the beginning of the trial was measured and photographs of all warts were taken weekly for five weeks. An analysis of covariance on the log of the volumes of warts during the five weeks of the trial showed a significant difference between groups (p = 0.026). Warts in treated groups tended to grow faster than in the placebo group. 相似文献