全文获取类型
收费全文 | 76878篇 |
免费 | 3780篇 |
国内免费 | 52篇 |
专业分类
林业 | 3665篇 |
农学 | 2373篇 |
基础科学 | 393篇 |
7979篇 | |
综合类 | 15545篇 |
农作物 | 3102篇 |
水产渔业 | 3432篇 |
畜牧兽医 | 38723篇 |
园艺 | 910篇 |
植物保护 | 4588篇 |
出版年
2018年 | 870篇 |
2017年 | 938篇 |
2016年 | 874篇 |
2015年 | 788篇 |
2014年 | 973篇 |
2013年 | 2629篇 |
2012年 | 1696篇 |
2011年 | 2100篇 |
2010年 | 1373篇 |
2009年 | 1307篇 |
2008年 | 2060篇 |
2007年 | 2112篇 |
2006年 | 1912篇 |
2005年 | 1858篇 |
2004年 | 1767篇 |
2003年 | 1797篇 |
2002年 | 1708篇 |
2001年 | 2231篇 |
2000年 | 2234篇 |
1999年 | 1856篇 |
1998年 | 705篇 |
1997年 | 699篇 |
1995年 | 813篇 |
1993年 | 697篇 |
1992年 | 1501篇 |
1991年 | 1554篇 |
1990年 | 1668篇 |
1989年 | 1648篇 |
1988年 | 1531篇 |
1987年 | 1480篇 |
1986年 | 1529篇 |
1985年 | 1516篇 |
1984年 | 1249篇 |
1983年 | 1144篇 |
1982年 | 772篇 |
1981年 | 718篇 |
1979年 | 1251篇 |
1978年 | 980篇 |
1977年 | 848篇 |
1976年 | 803篇 |
1975年 | 913篇 |
1974年 | 1201篇 |
1973年 | 1240篇 |
1972年 | 1256篇 |
1971年 | 1183篇 |
1970年 | 1104篇 |
1969年 | 1005篇 |
1968年 | 865篇 |
1967年 | 906篇 |
1966年 | 837篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
881.
The clinical pathology and histopathology of two groups of Atlantic salmon with severe degenerative myopathy (pancreas disease) is described and compared with a third healthy group. One affected group was anorexic and had low plasma protein and albumin levels while the other was feeding and had normal levels. Both diseased groups had plasma and tissue vitamin E and selenium levels lower than the healthy group. Similarly, creatine kinase values were raised in affected groups. If representative of the syndrome as a whole, the results suggest that the myopathy of pancreas disease has a basis in a vitamin E-selenium deficiency, but whether primary or induced is not clear. The results also demonstrate that the myopathy and pancreatic atrophy do not inevitably lead to anorexia or any other clinically obvious sign of disease, despite both cardiac and oesophageal involvement. 相似文献
882.
883.
884.
885.
886.
G. H. Adlam 《Canadian journal of veterinary research》1953,17(10):418-421
887.
K G Braund H S Steinberg A Shores J E Steiss J R Mehta M Toivio-Kinnucan K A Amling 《Journal of the American Veterinary Medical Association》1989,194(12):1735-1740
Six dogs with laryngeal paralysis had clinical, electrophysiologic, and pathologic evidence of a more generalized polyneuropathy. Three of the dogs were young Dalmatians, one was a young Bouvier des Flandres, and two were older, large-breed dogs. The results of this study suggest that laryngeal paralysis in dogs may frequently be one clinical sign of an underlying, more generalized polyneuropathy. Two forms of this generalized polyneuropathy may exist: an early form, as seen in young dogs with congenital or hereditary disease, and a delayed-onset form that is usually found in older dogs with so-called idiopathic laryngeal paralysis, some of which may have hypothyroidism. 相似文献
888.
M Suzuki K Sitizyo T Takeuchi T Saito 《Nippon juigaku zasshi. The Japanese journal of veterinary science》1990,52(5):1077-1087
Electroencephalogram (EEG) examinations were carried out on three Japanese Black calves (1, 2 and 14 week old) affected with cerebrocortical necrosis (CCN) in order to investigate the relationship between EEG abnormalities and encephalic lesions. Some neurologic signs such as circling, astasia, convulsion and opisthotonus appeared in two of the calves (case 1 and 3). The other calf (case 2), however, showed no neurologic signs. The EEGs obtained from the two calves (case 1 and 2), in the awake state, showed constant high amplitude (50-160 microV) and slow (1-4 Hz) activity (HASA). One of these (case 1) had necrosis mainly in the right hemisphere and showed a markedly asymmetric sharp wave. On the other hand, in case 3, the EEG showed diffuse lowered activity, and almost flat in some leads. A decrease in fast activity observed in common with all three animals. These findings suggest that one of the characteristic EEG patterns of CCN patient may be HASA and decreased fast activity. Histopathologic diagnoses of the calves were CCN in various degrees. The degrees of abnormality of the EEGs seemed to accord with the seriousness of the lesions. Because the EEG obtained from the calf having no obvious neurologic signs showed an abnormal pattern, it was considered that EEG examinations in the early stages of disorders are valuable to diagnose CCN. 相似文献
889.
890.
A computer-derived protocol using recursive partitioning to aid in estimating prognosis of horses with abdominal pain in referral hospitals 下载免费PDF全文
P J Pascoe N G Ducharme G R Ducharme J H Lumsden 《Canadian journal of veterinary research》1990,54(3):373-378
In order to determine which variables are useful and accurate in estimating prognosis in horses with abdominal pain, data were analyzed from 231 horses presented at a veterinary teaching hospital. Using multiple stepwise discriminant analysis in a recursive partition model, we obtained a decision protocol that identified survivors and nonsurvivors. The prevalence of survivors was 61% in this population. The sensitivity, specificity, and positive and negative predictive values of this model were 71, 83, 87 and 65%, respectively. This decision protocol was validated by Jackknife classification and also by evaluation with a referral population of 100 horses in which the prevalence of survivors was 83%. This led to sensitivity, specificity, and positive and negative predictive values of 83, 78, 94 and 50%, respectively. 相似文献