全文获取类型
收费全文 | 16467篇 |
免费 | 722篇 |
国内免费 | 1077篇 |
专业分类
林业 | 1820篇 |
农学 | 1202篇 |
基础科学 | 1337篇 |
2006篇 | |
综合类 | 7814篇 |
农作物 | 1141篇 |
水产渔业 | 397篇 |
畜牧兽医 | 1442篇 |
园艺 | 549篇 |
植物保护 | 558篇 |
出版年
2024年 | 96篇 |
2023年 | 271篇 |
2022年 | 466篇 |
2021年 | 558篇 |
2020年 | 557篇 |
2019年 | 606篇 |
2018年 | 316篇 |
2017年 | 583篇 |
2016年 | 698篇 |
2015年 | 629篇 |
2014年 | 1089篇 |
2013年 | 1056篇 |
2012年 | 1465篇 |
2011年 | 1447篇 |
2010年 | 1091篇 |
2009年 | 1044篇 |
2008年 | 862篇 |
2007年 | 1026篇 |
2006年 | 883篇 |
2005年 | 742篇 |
2004年 | 611篇 |
2003年 | 458篇 |
2002年 | 296篇 |
2001年 | 257篇 |
2000年 | 238篇 |
1999年 | 151篇 |
1998年 | 155篇 |
1997年 | 115篇 |
1996年 | 98篇 |
1995年 | 69篇 |
1994年 | 60篇 |
1993年 | 61篇 |
1992年 | 48篇 |
1991年 | 43篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 18篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1963年 | 1篇 |
1962年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, India, during the wet seasons of 1992 and 1993 to study the effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two levels of N (100 and 200 kg ha−1 ) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and green manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha−1 (72 kg N) green manure) and a no N control. Nitrogen application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha−1 and of single fertilizer N at 200 kg N ha−1 recorded the maximum N uptake, increased the yield attributes such as number of panicles per unit area, weight per panicle, number of total and filled grains per panicle and test weight. At 200 kg N ha−1 full substitution of N by green manure reduced the grain yield but only partial substitution of N by green manure resulted in almost similar yield as single fertilizer N. Thus 200 kg N ha−1 applied in equal proportions of fertilizer and green manure N can be recommended for medium duration rice cultivars. 相似文献
12.
JEV、PPV、PRRSV、PRV多联PCR的应用研究 总被引:3,自引:0,他引:3
用 JEV、PRRSV二联 PCR,PPV、PRV二联 PCR以及这 4种病毒 4联 PCR对来自内蒙、广州、广西、天津、北京、吉林病料进行检测 ,共检了 1 4 6份病料。其中 PRRSV阳性 7份 ,PPV阳性 1 2份 ,PRV阳性 2 1份 ,PRV和 PPV混合感染 4份。并对 5份人工接种 JEV小鼠病料检测 ,其中 4份为阳性。随后对部分阳性 PCR扩增产物进行点杂交和核苷酸测序鉴定 ,证实了 PCR扩增准确性。对内蒙 PRRSV阳性扩增带测序结果显示 ,我国流行 PRRSV为美洲型 ,在扩增片段的核苷酸序列上有 3个碱基差异 相似文献
13.
14.
15.
K.F. Stock 《Livestock Production Science》2005,92(1):77-94
The results of a standardised radiological examination of 5928 Hanoverian Warmblood horses selected for sale at auction were used to predict relative breeding values (RBV) in the 23,662 horses included in the last four generations of the probands' pedigrees. The distribution of the RBV was investigated in the whole four-generation pedigree, in the probands and in those stallions that contributed at least three offspring to the probands. The RBV of the probands' sires were further compared with the officially published performance-based relative breeding values, i.e., total indices dressage (TID) and jumping (TIJ). The sires' level of dressage indices was considerably higher (mean TID=110) than of the jumping indices (mean TIJ=98). Total indices radiographic findings (TIR) were calculated for the sires with varying weighting given to the individual RBV. In each case, this resulted in a mean TIR of 99. Finally, total indices were derived from TIR and TID and/or TIJ in order to develop different selection schemes for all-purpose breeding and for breeding focused on dressage and show jumping. All breeding values under consideration increased by between 1% and 19% when radiographic findings were weighted with between 30% and 60% complementary to the corresponding performance parameters, and when only sires were selected with above average total indices. At the same time, the prevalences of the radiographic findings investigated here were lowered by up to 10% each. When only one radiographic finding was considered at a time, the maximum attainable response to selection was a 16-23% increase in the relative breeding values and a relative decrease in prevalences of radiographic findings of between 31% and 52%. The results of this study indicate that it is possible in horse breeding to consider simultaneously health and performance traits. Medical data should be included in the prediction of breeding values in order to improve the radiological status of today's riding horses. 相似文献
16.
17.
甲氧基丙烯酸酯类杀菌剂的应用、开发现状及展望 总被引:19,自引:2,他引:19
本文对甲氧基丙烯酸酯类杀菌剂的开发现状及应用前景进行了简要的介绍。文中涉及甲氧基丙烯酸酯类杀菌剂的化学结构、生物活性、登记与专利和开发公司等。 相似文献
18.
19.
20.
农药酶免疫分析技术研究进展 总被引:4,自引:0,他引:4
自从酶免疫分析原理提出后,近30年来已获得了巨大的进步,成为农药分析的一个非常重要的方法。本文对农药酶免疫分析技术的原理和测定程序进行了评述.并总结了近年酶免疫分析在农药领域研究中的应用,最后,对农药酶免疫分析技术存在的问题和发展趋势作了讨论。 相似文献