全文获取类型
收费全文 | 103241篇 |
免费 | 5201篇 |
国内免费 | 100篇 |
专业分类
林业 | 4114篇 |
农学 | 2817篇 |
基础科学 | 600篇 |
12186篇 | |
综合类 | 18414篇 |
农作物 | 4019篇 |
水产渔业 | 4368篇 |
畜牧兽医 | 54947篇 |
园艺 | 1141篇 |
植物保护 | 5936篇 |
出版年
2019年 | 981篇 |
2018年 | 1538篇 |
2017年 | 1692篇 |
2016年 | 1470篇 |
2015年 | 1193篇 |
2014年 | 1622篇 |
2013年 | 4010篇 |
2012年 | 2772篇 |
2011年 | 3437篇 |
2010年 | 2258篇 |
2009年 | 2333篇 |
2008年 | 3443篇 |
2007年 | 3230篇 |
2006年 | 2975篇 |
2005年 | 2701篇 |
2004年 | 2628篇 |
2003年 | 2659篇 |
2002年 | 2389篇 |
2001年 | 2938篇 |
2000年 | 2999篇 |
1999年 | 2281篇 |
1998年 | 919篇 |
1997年 | 911篇 |
1996年 | 879篇 |
1995年 | 1033篇 |
1993年 | 917篇 |
1992年 | 1887篇 |
1991年 | 2076篇 |
1990年 | 1971篇 |
1989年 | 2004篇 |
1988年 | 1757篇 |
1987年 | 1805篇 |
1986年 | 1886篇 |
1985年 | 1813篇 |
1984年 | 1452篇 |
1983年 | 1300篇 |
1979年 | 1556篇 |
1978年 | 1166篇 |
1977年 | 1069篇 |
1976年 | 1058篇 |
1975年 | 1194篇 |
1974年 | 1457篇 |
1973年 | 1441篇 |
1972年 | 1407篇 |
1971年 | 1294篇 |
1970年 | 1302篇 |
1969年 | 1288篇 |
1968年 | 1196篇 |
1967年 | 1179篇 |
1966年 | 1114篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
J P Dubey A N Hamir C A Hanlon C E Rupprecht 《Journal of the American Veterinary Medical Association》1992,200(4):534-536
Serum samples from 427 raccoons (93 from Pennsylvania, 45 from New Jersey, 72 from South Carolina, 68 from Virginia, 30 from Iowa, and 119 from Ohio) were evaluated for Toxoplasma gondii antibodies in dilutions of 1:25, 1:50, and 1:500. The distribution of T gondii antibody titers was less than 1:25 for 212 raccoons (49.6%), 1:25 for 34 raccoons (7.9%), 1:50 for 117 raccoons (27.4%), and greater than or equal to 1:500 for 64 raccoons (14.9%). Tissue cysts were seen in the liver, and tachyzoites were in the brain of a raccoon with abnormal neurologic signs and concurrent infection with canine distemper virus. Organisms in the liver were stained with anti-T gondii serum, and the raccoon had a T gondii titer of 1:160 in the agglutination test. 相似文献
72.
When susceptibility to virulent Pasteurella multocida was compared, there was no significant (P greater than 0.05) difference between caponized and uncaponized tom turkeys. Neither was there any significant (P greater than 0.05) difference between the surviving caponized and uncaponized toms in the development of serum anti-P. multocida antibody. However, at 28 weeks of age, the average live body weight of the caponized toms was significantly (P less than 0.05) lower than that of the uncaponized toms. Turkeys were caponized when 9 weeks old, and different groups were exposed to P. multocida when 13, 18, 23, and 28 weeks old. 相似文献
73.
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
74.
75.
S. Dänicke I. Halle E. Strobel E. Franke & H. Jeroch 《Journal of animal physiology and animal nutrition》2001,85(9-10):301-313
76.
Mangroves as indicators of coastal change 总被引:2,自引:0,他引:2
In view of the unique biological characteristics of mangroves, it is interesting to assess the extent to which these ecosystems can be used as indicators of coastal change or sea-level rise. From recent studies of mangrove mortality at several locations (including Guiana, Gambia, Côte d'Ivoire, Kenya, India and Bangladesh), it appears that these coastal ecosystems are so specialized that any minor variation in their hydrological or tidal regimes causes noticeable mortality. Each species of mangrove (but particularly those belonging to the genera Rhizophora, Bruguiera, Sonneratia, Heritiera and Nypa) occurs in ecological conditions that approach its limit of tolerance with regard to salinity of the water and soil, as well as the inundation regime. If the duration of daily immersion were to be modified by tectonic, sedimentological or hydrological events, the species either readjusts to the new conditions or succumbs to unsuitable conditions. Consequently, the use of remote sensing data for mangrove ecosystems offers excellent potential as a tool for monitoring coastal change. 相似文献
77.
The effect of exploratory laparotomy on the serum and peritoneal haptoglobin concentrations of the pony. 总被引:1,自引:0,他引:1 下载免费PDF全文
Serum haptoglobin concentration was used as an indicator of the acute phase response in ponies undergoing exploratory laparotomy. Preoperative, 1 h intraoperative, 3 h, 6 h, 12 h and 24 h postoperative blood samples and 48 h postoperative peritoneal fluid samples were obtained for haptoglobin analysis. A spectrophotometric assay based on cyanmethemoglobin binding capacity (CyanBC) was used to determine haptoglobin concentrations. The preoperative reference range for serum haptoglobin concentrations in these ponies was 25-60 mg CyanBC/dL. Intraoperative and 3 h postoperative blood samples had decreased haptoglobin concentrations when compared to preoperative values. Serum haptoglobin concentrations began to rise by the 6 h postoperative sample and were generally elevated above preoperative values by the 24 h postoperative sample. Two of the ten ponies had mild signs of postoperative colic which were associated with twofold elevations in serum haptoglobin concentrations and fivefold elevations in peritoneal fluid haptoglobin concentrations. 相似文献
78.
79.
Time course of grain filling pattern in two rice (Oryza sativa L.) cultivars, grown under normal and low light intensities, was studied. The number of spikelets, partially filled grains and high density grains were monitored at a 5 day interval during grain filling period from uniform panicles tagged at anthesis. The low light tolerant cultivar Swarnaprabha had more high density grains and less partially filled grains throughout the grain filling period and at harvest compared to cultivar Ratna under both normal and low light intensities. Further, the opening of spikelets in two flushes in Swarnaprabha seemed to result in a more efficient resource allocation and hence better yield as compared to Ratna, in which the opening of spikelets was in a single flush on day 10. 相似文献
80.
A Desrochers D E Anderson G St-Jean 《Veterinary Clinics of North America: Food Animal Practice》2001,17(1):143-58, vii
Digital diseases are commonly seen in cattle. Cattle affected by digital disorders do not always respond to conservative therapy and require surgery. Surgical procedures for the common digital disorders are described, with emphasis on the different approaches to the distal interphalangeal joint. 相似文献