全文获取类型
收费全文 | 124411篇 |
免费 | 6331篇 |
国内免费 | 74篇 |
专业分类
林业 | 5411篇 |
农学 | 3775篇 |
基础科学 | 814篇 |
13752篇 | |
综合类 | 24614篇 |
农作物 | 4819篇 |
水产渔业 | 5446篇 |
畜牧兽医 | 63075篇 |
园艺 | 1374篇 |
植物保护 | 7736篇 |
出版年
2018年 | 1372篇 |
2017年 | 1538篇 |
2016年 | 1433篇 |
2015年 | 1224篇 |
2014年 | 1478篇 |
2013年 | 4206篇 |
2012年 | 2888篇 |
2011年 | 3426篇 |
2010年 | 2276篇 |
2009年 | 2293篇 |
2008年 | 3447篇 |
2007年 | 3323篇 |
2006年 | 3139篇 |
2005年 | 3082篇 |
2004年 | 2921篇 |
2003年 | 3137篇 |
2002年 | 2906篇 |
2001年 | 3402篇 |
2000年 | 3332篇 |
1999年 | 2676篇 |
1997年 | 1189篇 |
1995年 | 1322篇 |
1994年 | 1198篇 |
1993年 | 1175篇 |
1992年 | 2502篇 |
1991年 | 2694篇 |
1990年 | 2711篇 |
1989年 | 2764篇 |
1988年 | 2595篇 |
1987年 | 2548篇 |
1986年 | 2637篇 |
1985年 | 2552篇 |
1984年 | 2162篇 |
1983年 | 1871篇 |
1982年 | 1336篇 |
1981年 | 1213篇 |
1979年 | 2069篇 |
1978年 | 1636篇 |
1977年 | 1514篇 |
1976年 | 1406篇 |
1975年 | 1551篇 |
1974年 | 1967篇 |
1973年 | 1935篇 |
1972年 | 1945篇 |
1971年 | 1858篇 |
1970年 | 1766篇 |
1969年 | 1616篇 |
1968年 | 1338篇 |
1967年 | 1570篇 |
1966年 | 1270篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
An ammonium sulfate fraction of Taenia hydatigena cyst fluid (ThFAS) was further fractionated by hydrophobic interaction chromatography, using alkylagarose and omega-amino alkylagarose columns, in an effort to isolate and purify a specific diagnostic antigen in the ThFAS preparation. The less than 12 kDa antigen was found to have an affinity for immobilized alkanes with chain length of six carbons or greater. The antigen was recovered in an ethylene glycol eluate from a hexylagarose column then analyzed by Western blot; it reacted with bovine and human cysticercosis infection sera and with specific monoclonal antibodies but not with control sera or fascioliasis infection sera. When the eluate was used as coating antigen in a plate ELISA assay no false positive reactions were seen in sera from cattle infected with Fasciola hepatica; false positive reactions were observed for the unfractionated ThFAS antigen preparation. 相似文献
122.
R. Iori O. Leoni L. Lazzeri G. Mosca S. Palmieri 《Journal of Agronomy and Crop Science》1991,167(2):91-95
Samples of rapeseed from three Italian growing environments (Bologna, Perugia and Palermo) were analysed for glucose content and dry weight of 1000 seeds every three or four days starting from the end of flowering until complete ripening. In addition, the content of oil, soluble and total proteins, glucosinolates and myrosinase activity was determined in samples of mature seeds. The cultivars used were jet Neuf and Lingot (type 0) and Tandem, Jade and Santana (type 00). From the results it emerged that the point of intersection of the two branches of the linear regression plots for different glucose-consumption kinetics found during seed filling, in addition to being strongly affected by the climate of the test environment, is correlated with quantitative and qualitative production, independently of the genotype. 相似文献
123.
山羊脑灰质软化症 (POLIOEN CEPHALOMALACIA)和李氏杆菌病 (LIS TERIOSIS)是症状相似治疗方法截然不同的两种疾病。山羊饲养者和兽医工作者必须从两种疾病的细微差别中进行鉴别 ,以便正确治疗和处理病羊。多数情况下 ,这两种疾病出现在饲养条件比较好、但饲养方法不当的地方。特别是在快速育肥时。精饲料喂量过多 ,而含粗纤维的饲料喂量过少是诱发两种疾病的重要因素。突然更换饲料常常导致此病突然发作。脑灰质软化症 (通常又称为大脑皮层坏死症 )是缺乏硫胺 (即维生素B1)而造成的一种代谢性疾病。瘤胃环… 相似文献
124.
125.
Gastro-oesophageal reflux together with sliding hiatus hernia is reported in a dog, associated with laryngeal paralysis. Diagnosis was made following endoscopy and fluoroscopy. Surgical treatment of the laryngeal paralysis resulted in complete remission of clinical signs. 相似文献
126.
127.
Intact chicks and those that had their glands of Harder (GH) removed (GHx) at 1 day of age were studied for their response to optically or intraperitoneally (IP) applied antigens. Following exposure of the chicks to sheep red blood cells (SRBCs), killed Brucella abortus, or bovine serum albumin (BSA), serum and tear samples were collected and assayed for antibodies. Of the two sources of antibodies, the serum generally had higher levels than did the tears. The only exception to this occurred in the intact chicks inoculated by the eye, in which serum and tear levels were equivalent. With SRBCs, no difference could be detected between the two routes of inoculation. However, IP inoculation produced higher levels of antibody in the serum of intact and GHx chicks inoculated with B. abortus or BSA and in the tears of the GHx chicks exposed to B. abortus. Removal of the GH resulted in a consistent decrease in antibody levels in the tears, regardless of the route of exposure. Although this effect was noted with all three antigens, it was more pronounced in the trials using B. abortus and BSA. This finding is discussed in terms of describing the importance of the GH as a source of antibodies to optically applied antigens, and its importance as a route of circulating antibody egress. Furthermore, the feasibility of using the antibody response in tears to a test antigen is discussed as a means of measuring the immune status of a functioning GH. 相似文献
128.
The management of guttural pouch mycosis 总被引:1,自引:0,他引:1
J G Lane 《Equine veterinary journal》1989,21(5):321-324
129.
130.
Described in this paper are 2 methodological variants for photometric recording of sperm aggregation. Heparin was used to induce aggregation. One of the working principles was related to aggregation-associated alteration of turbidity in an agitated cell suspension, measured by the KZM-1 coagulation-time meter, in analogy to measurement of thrombocyte aggregation. The 2nd variant was based on variation of cloudiness due to sedimentation of aggregates in a non-agitated suspension. Both methods provided equally valid information. They characterised both intensity of aggregation as a combined effect of the number and size of aggregates as well as the rate of aggregation. Photometric recording has proved to be an objectivated method for quantitative assessment of aggregation. Its use is proposed for studies into capacitation or immunological response of spermatozoa. 相似文献