全文获取类型
收费全文 | 118263篇 |
免费 | 6652篇 |
国内免费 | 70篇 |
专业分类
林业 | 5759篇 |
农学 | 4243篇 |
基础科学 | 749篇 |
14706篇 | |
综合类 | 16798篇 |
农作物 | 4289篇 |
水产渔业 | 6219篇 |
畜牧兽医 | 63301篇 |
园艺 | 1525篇 |
植物保护 | 7396篇 |
出版年
2018年 | 1800篇 |
2017年 | 1919篇 |
2016年 | 1840篇 |
2015年 | 1598篇 |
2014年 | 1936篇 |
2013年 | 4548篇 |
2012年 | 3457篇 |
2011年 | 4175篇 |
2010年 | 2826篇 |
2009年 | 2801篇 |
2008年 | 4159篇 |
2007年 | 3992篇 |
2006年 | 3846篇 |
2005年 | 3556篇 |
2004年 | 3513篇 |
2003年 | 3492篇 |
2002年 | 3257篇 |
2001年 | 4228篇 |
2000年 | 4085篇 |
1999年 | 3314篇 |
1998年 | 1448篇 |
1997年 | 1277篇 |
1996年 | 1217篇 |
1995年 | 1362篇 |
1994年 | 1295篇 |
1993年 | 1200篇 |
1992年 | 2544篇 |
1991年 | 2690篇 |
1990年 | 2860篇 |
1989年 | 2611篇 |
1988年 | 2465篇 |
1987年 | 2373篇 |
1986年 | 2348篇 |
1985年 | 2238篇 |
1984年 | 1882篇 |
1983年 | 1646篇 |
1982年 | 1070篇 |
1979年 | 1671篇 |
1978年 | 1308篇 |
1977年 | 1122篇 |
1976年 | 1121篇 |
1975年 | 1146篇 |
1974年 | 1304篇 |
1973年 | 1346篇 |
1972年 | 1348篇 |
1971年 | 1267篇 |
1970年 | 1242篇 |
1969年 | 1200篇 |
1967年 | 1087篇 |
1966年 | 1033篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Timmer CP 《Science (New York, N.Y.)》1979,205(4404):385-386
992.
993.
Abelson PH 《Science (New York, N.Y.)》1979,203(4385):1071
994.
995.
In a consecutive and non-selected study of 54 kidney transplanted dogs, 12 cases of intussusception of the small intestine developed in 8 dogs. The patogenesis is still unknown. It has been postulated that the time of the operation (4--7 hours) and the segmental termination of the post-operative atony in the intestine are essential factors in this fatal complication. The last 16 dogs in this material were peroperatively treated with antikolinergics (Mestinon NFN), which was continued until normal function of the intestine. In these dogs there were no evidence of intussusception. The value of this profylaxis is open to discussion and it is essential to solve the problem of intussusception through a "blind" and controlled trial. 相似文献
996.
The intraindividual variability in mean electric axis referable to choice of ECG leads and augmentation ratio was investigated by means of a digital computer program. Although, in theory, the choice of leads for determining the QRS axis should make no difference, the maximum intraindividual variation in axis angle was about 50 degrees for canine and feline subjects. The angle conputed for the lead combinations I and III and I and aVF will usually fall within 5 to 10 degrees of the mean of all lead combinations, but larger variations are seen at time. The application of an "augmentation ratio" for the augmented unipolar leads was most helpful when it was individually computed. Further methods of lead-vector improvement are discussed. 相似文献
997.
The hemolysis of unsensitized human erythrocytes by fresh bovine serums was investigated. Lysis occurred in ethylene glycol bis-amino tetraacetate buffers and with serums depleted of Clq. Serums extensively absorbed with packed human erythrocytes at 0 C effectively lysed human erythrocytes, but optimal lytic capacity required target cells "sensitized" with a heat-stable serum factor. Lysis did not occur with serums absorbed with zymosan at 17 C or heat inactivated at 50 C. These results indicate that human erythrocytes can activate the alternative pathway of complement in bovine serums. Lysis can proceed in the apparent absence of antibodies, although their presence may enhance the reaction. 相似文献
998.
999.
1000.