全文获取类型
收费全文 | 232135篇 |
免费 | 12297篇 |
国内免费 | 159篇 |
专业分类
林业 | 10647篇 |
农学 | 7623篇 |
基础科学 | 1418篇 |
28501篇 | |
综合类 | 39187篇 |
农作物 | 9021篇 |
水产渔业 | 11579篇 |
畜牧兽医 | 118434篇 |
园艺 | 3069篇 |
植物保护 | 15112篇 |
出版年
2018年 | 3198篇 |
2017年 | 3494篇 |
2016年 | 3332篇 |
2015年 | 2890篇 |
2014年 | 3561篇 |
2013年 | 8983篇 |
2012年 | 6346篇 |
2011年 | 7660篇 |
2010年 | 5215篇 |
2009年 | 5135篇 |
2008年 | 7598篇 |
2007年 | 7441篇 |
2006年 | 6906篇 |
2005年 | 6439篇 |
2004年 | 6295篇 |
2003年 | 6360篇 |
2002年 | 5883篇 |
2001年 | 7069篇 |
2000年 | 7002篇 |
1999年 | 5712篇 |
1998年 | 2333篇 |
1997年 | 2364篇 |
1996年 | 2188篇 |
1995年 | 2628篇 |
1994年 | 2217篇 |
1993年 | 2251篇 |
1992年 | 4536篇 |
1991年 | 4795篇 |
1990年 | 4865篇 |
1989年 | 4857篇 |
1988年 | 4476篇 |
1987年 | 4437篇 |
1986年 | 4476篇 |
1985年 | 4281篇 |
1984年 | 3592篇 |
1983年 | 3211篇 |
1982年 | 2221篇 |
1979年 | 3304篇 |
1978年 | 2629篇 |
1977年 | 2351篇 |
1976年 | 2251篇 |
1975年 | 2443篇 |
1974年 | 2962篇 |
1973年 | 3056篇 |
1972年 | 3022篇 |
1971年 | 2744篇 |
1970年 | 2738篇 |
1969年 | 2542篇 |
1968年 | 2189篇 |
1967年 | 2304篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
O Diall V M Nantulya A G Luckins B Diarra B Kouyate 《Revue d'élevage et de médecine vétérinaire des pays tropicaux》1992,45(2):149-153
Two enzyme-linked immunosorbent assays (ELISA), one based on a mouse anti-Trypanosoma brucei group-specific monoclonal antibody and the other on rabbit anti-Trypanosoma evansi polyclonal antibodies, have been evaluated for their ability to detect circulating trypanosome antigens in camel sera as a means for the diagnosis of T. evansi infections. All 91 sera from a negative control camel herd from Kenya gave negative antigen-ELISA results in the monoclonal antibody-based ELISA and only 2 of them (2.2%) gave false positive results in the polyclonal antibody-based ELISA. In subsequent analyses of sera from infected camels (as determined by mouse inoculation), the monoclonal antibody-based ELISA detected antigens in 90 (83.3%) out of the 108 sera tested. This percentage was lower for the polyclonal antibody-based ELISA which was able to detect antigens in 67 (60.9%) out of the 110 sera tested. The two tests detected probably different antigens and when the results were combined, 99 out of 107 (92.5%) sera were shown to be ELISA positive. In a survey involving 316 camels from the Gao and Nara areas, in Mali, a high proportion of animals tested were antigen positive (43.5 and 42.9%, respectively for the mono- and polyclonal antibody-based ELISA) compared to only 22 (7.0%) diagnosed by the parasite detection techniques. Thus, these immunoassays were at least six times more sensitive than the haematocrit centrifugation technique. As a large proportion of cases may be antigen positive but parasite negative, these two of "surra" immunoassays should be used in routine diagnosis in addition to the parasite detection techniques in the dromedary camel. 相似文献
996.
Five Devon cattle with suspected ceroid-lipofuscinosis and aged between 19 and 39 months of age were humanely slaughtered and subjected to post-mortem examination. There was severe atrophy of the cerebrum, particularly of the occipital cortex. Microscopy also showed severe atrophy of the retina with complete loss of photoreceptor cells, even in the youngest animal examined. Histopathologically the disease was characterised by accumulation of a fluorescent lipopigment in neurones, including those of the retina and a severe astrocytosis. The disease, which is characterised by the accumulation of subunit c of mitochondrial ATP synthase, is similar to that extensively described in South Hampshire sheep except that the retinal lesions were more severe. In contrast, tremors were not noted in the cattle. The clinical history and similarity to the disease in sheep and other species indicated inheritance was as an autosomal recessive trait. 相似文献
997.
Twelve veterinarians were asked to estimate the percentage of lung surface that appeared consolidated in eleven projected colour transparencies of pneumonic ovine lungs. The estimates were compared to the pneumonic area measured by image analysis. Although all observers had some experience in veterinary pathology there was considerable variation between individuals in the accuracy of their estimates. Large lesions were underestimated and small lesions overestimated by most observers. 相似文献
998.
Bisset SA Vlassoff A McMurtry LW Elliott DC Cobb RM Kieran PJ Wood IB 《New Zealand veterinary journal》1992,40(3):97-100
The efficacy of an oral formulation of the newly developed parasiticide, moxidectin, was tested against benzimidazole-resistant Haemonchus contortus, Trichostrongylus colubriformis, and Nematodirus spathiger, levamisole-resistant Ostertagia circumcincta, and susceptible Cooperia curticei infections in weaned lambs. Thirty-two lambs were experimentally infected with mixed doses of the above strains of nematodes. They were allocated into four treatment groups by stratified randomisation using liveweights and faecal egg counts 28 days later. One group received moxidectin at 0.2 mg/kg liveweight, one group oxfendazole at 4.5 mg/kg liveweight, one group levamisole at 7.5 mg/kg liveweight and the last group remained untreated as the control. Worm burdens in the lambs at slaughter 10 days after oral treatment confirmed the resistance status of the nematode strains used, and showed that moxidectin had a greater than 99.9% efficacy (p<0.01) against all of them. No adverse effects due to treatment with moxidectin were observed in any of the animals. 相似文献
999.
The vascular organisation of the hind limb claws of clinically normal cattle was studied using scanning electron micrographs of plastic corrosion casts. The microvasculature of the dermal papillae and lamellae was demonstrated. A consistent vascular pattern was observed in the dermal papillae of the periople, coronary margin, sole and bulb. Ultrastructurally, the papillar vasculature consisted of a central artery and vein surrounded by a fine network of interconnected capillaries and venules. Arteriovenous anastomoses, connecting the central artery and vein, and peripherally situated arteriovenous loops were recognised in the terminal papillae of the white zone only. Arteriovenous anastomoses, focal enlargements and distension of the capillary bed were located within the interior half of the dermal lamellae. Numerous arteriovenous anastomoses were present throughout the entire dermis of the claw and were situated predominantly at the base of the dermal papillae and lamellae. The anastomoses and focal capillary enlargements may influence the blood flow in normal conditions and may play a significant role in the pathophysiology of bovine laminitis and sole ulceration. 相似文献
1000.
Thirty of 200 ewes died or were euthanatized during a 21-day period following a 1-day accidental exposure to natural gas condensate, a complex mixture of hydrocarbons obtained during collection of natural gas from wells. Despite access to potable well water, the poisoned ewes willingly consumed toxic doses of condensate that contaminated surface water. Eight animals died without premonitory signs; the remainder became ill over the course of a few days to 3 weeks. The principal cause of mortality was aspiration pneumonia, but myocardial degeneration and necrosis, renal tubular damage, gastritis, enteritis, and meningeal edema and hyperemia were also observed. Gas chromatographic analysis identified chemical traces of the hydrocarbons in the tissues, and "fingerprinting," the process of matching chromatographic tracings, provided forensic proof of the contamination source. Atomic absorption spectroscopy and cholinesterase analyses were performed to eliminate the possibility of toxicosis by heavy metal contaminants or other constituents. This appears to be the first reported incidence of natural gas condensate toxicity involving sheep or other ruminants. Although the available literature presents a suggestive pattern of clinical signs and pathologic lesions of petroleum product poisoning, diagnostic investigations should employ detailed analytic examination because each source of petroleum hydrocarbons contains unique sets of components that may produce different toxic effects. 相似文献