全文获取类型
收费全文 | 122377篇 |
免费 | 6685篇 |
国内免费 | 62篇 |
专业分类
林业 | 6167篇 |
农学 | 3890篇 |
基础科学 | 693篇 |
15201篇 | |
综合类 | 20859篇 |
农作物 | 4719篇 |
水产渔业 | 6086篇 |
畜牧兽医 | 61778篇 |
园艺 | 1435篇 |
植物保护 | 8296篇 |
出版年
2018年 | 1829篇 |
2017年 | 2050篇 |
2016年 | 1890篇 |
2015年 | 1590篇 |
2014年 | 1980篇 |
2013年 | 4598篇 |
2012年 | 3657篇 |
2011年 | 4053篇 |
2010年 | 2633篇 |
2009年 | 2700篇 |
2008年 | 3983篇 |
2007年 | 3860篇 |
2006年 | 3547篇 |
2005年 | 3399篇 |
2004年 | 3150篇 |
2003年 | 3271篇 |
2002年 | 3028篇 |
2001年 | 3523篇 |
2000年 | 3477篇 |
1999年 | 2826篇 |
1998年 | 1121篇 |
1997年 | 1183篇 |
1996年 | 1083篇 |
1995年 | 1307篇 |
1994年 | 1130篇 |
1993年 | 1145篇 |
1992年 | 2321篇 |
1991年 | 2432篇 |
1990年 | 2374篇 |
1989年 | 2397篇 |
1988年 | 2274篇 |
1987年 | 2269篇 |
1986年 | 2351篇 |
1985年 | 2243篇 |
1984年 | 1895篇 |
1983年 | 1655篇 |
1982年 | 1139篇 |
1979年 | 1761篇 |
1978年 | 1407篇 |
1977年 | 1297篇 |
1976年 | 1212篇 |
1975年 | 1284篇 |
1974年 | 1693篇 |
1973年 | 1616篇 |
1972年 | 1636篇 |
1971年 | 1565篇 |
1970年 | 1445篇 |
1969年 | 1405篇 |
1968年 | 1164篇 |
1967年 | 1291篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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
92.
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
93.
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
94.
95.
The utilization of dietary lysine for protein synthesis is affected by the digestibility of protein-bound lysine, by its intestinal resorption and by its oxidative catabolism. The approach chosen in this paper enables a comparison of the cumulative effect of these processes on the utilization of free and protein-bound lysine, respectively. The principle of the approach is based on a quantification of the expiration of 14C-labelled carbon dioxide after an oral administration of a diet, which contains L-(U-14C)-lysine either as a free amino acid or bound to yeast proteins. During an adaptation phase cockerels of the Japanese quail received a diet based mainly on ground wheat and wheat gluten. This diet was supplemented either with yeast proteins or with a mixture of L-amino acids which simulates the composition of the yeast proteins. In the main experiment the expiration of labelled carbon dioxide was measured during 240 minutes after the administration of the corresponding labelled diets. Just before treatment the animals were either in the postprandial phase or in a state of slight hunger. The maximum of expiration of labelled carbon dioxide occurred around the 60th minute after administration of the corresponding labelled diets. The cumulative expiration of labelled carbon dioxide, expressed in per cent of the radioactive dose used, amounts to 15.5% and 14.3% for free and protein-bound lysine, respectively. The utilization of both forms of lysine in the Japanese quail is lower than in broilers. 相似文献
96.
97.
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
98.
99.
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
100.