全文获取类型
收费全文 | 6826篇 |
免费 | 373篇 |
国内免费 | 775篇 |
专业分类
林业 | 680篇 |
农学 | 899篇 |
基础科学 | 524篇 |
1119篇 | |
综合类 | 2398篇 |
农作物 | 378篇 |
水产渔业 | 343篇 |
畜牧兽医 | 974篇 |
园艺 | 258篇 |
植物保护 | 401篇 |
出版年
2024年 | 33篇 |
2023年 | 123篇 |
2022年 | 282篇 |
2021年 | 363篇 |
2020年 | 310篇 |
2019年 | 355篇 |
2018年 | 203篇 |
2017年 | 281篇 |
2016年 | 248篇 |
2015年 | 356篇 |
2014年 | 321篇 |
2013年 | 386篇 |
2012年 | 414篇 |
2011年 | 457篇 |
2010年 | 418篇 |
2009年 | 384篇 |
2008年 | 398篇 |
2007年 | 318篇 |
2006年 | 290篇 |
2005年 | 255篇 |
2004年 | 142篇 |
2003年 | 110篇 |
2002年 | 122篇 |
2001年 | 138篇 |
2000年 | 136篇 |
1999年 | 151篇 |
1998年 | 151篇 |
1997年 | 109篇 |
1996年 | 96篇 |
1995年 | 124篇 |
1994年 | 93篇 |
1993年 | 82篇 |
1992年 | 68篇 |
1991年 | 66篇 |
1990年 | 54篇 |
1989年 | 37篇 |
1988年 | 34篇 |
1987年 | 23篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1964年 | 1篇 |
1963年 | 2篇 |
1956年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有7974条查询结果,搜索用时 15 毫秒
71.
在目前非洲猪瘟疫苗毒株、变异毒株、野毒株并存背景下,只做好外部生物安全已不足以达到防控非洲猪瘟的目的。因疫苗毒株隐蔽性强、检测难度大,不知道通过引种是否会将疫苗毒株带到猪场。因此,未来猪场生物安全不能只关注场外生物安全,更重要的是要运用“以猪为本”的“1237”P氏生物安全立体非洲猪瘟防控体系,即在做好“控五流”等外部生物安全的同时,更要关注饮水安全、注重猪的自身健康度、提高猪的非特异性免疫力,才能实现“与非共存,与蓝共舞”。所谓“立体防控”是指全方位的防控,而不是仅仅针对猪场大门的传统生物安全防控。 相似文献
72.
RAN Xu-hua ZHANG Yao CAO Si LU Yuan-he ZHANG Ling-ling LIU Yang-yang NI Hong-bo ZHU Zhan-bo WEN Xiao-bo 《中国畜牧兽医》2016,43(5):1368-1373
To identify the infection agents from Ningxia Hui Autonomous region, where feedlot cattle indicated bovine respiratory disease complex (BRDC), the M gene of the bovine parainfluenza virus type 3 was amplified by RT-PCR.The PCR product was ligated to pMD18-T vector and cloned to E.coli DH5α.The positive clones were sequenced and compared with the reference strains in GenBank by the molecular biology software.Sequence alignment results showed that a BPIV3 strain was isolated from the samples and named NX49, the M gene of NX49 included 1 056 nucleotides.Evolutionary analysis showed that the NX49 belonged to BPIV3 C genotype and shared 99.4% nucleotide identity with that of the SD0835 isolated in Shandong province.The characterization of the NX49 demonstrated that it was sensitive to temperature, acid and organic matter.The presence of Mg2+ showed no protection against the treatment at high temperature.The HA test suggested that the NX49 enables to agglutinate the guinea pig RBC at 4 ℃ and the titer was 1∶4.The study isolated a BPIV3 genotype C strain successfully, which facilitate the study of molecular evolution and epidemiology of BPIV3 in China. 相似文献
73.
YAO Wei YU Xue-wu CAO Dong ZHAO Xiao-tong GU Gui-bo CHEN Yao ZHANG Lei LIU Yao-chuan FENG Jun-ke 《中国畜牧兽医》2016,43(11):3080-3084
In order to understand the main bacterial pathogen species causing dairy cow mastitis in Liaoning, as well as the characteristics of drug sensitivity of the pathogenic E.coli,the milk samples from 75 dairy cows with clinical manifestations for mastitis in certain large-scale dairy farm in Liaoning were collected.The bacteria in milk were cultured and isolated with biochemical methods and in vitro drug sensitivity tests were processed with the isolated E.coli strains.The results showed that the main bacterial pathogen for dairy cow mastitis were E.coli(separation rate 58.7%),S.aureus(64.0%)and S.agalactiae(54.7%),and multiple infection including double and triple infection were identified.The drug sensitivity tests on the isolated E.coli indicated that the E.coli isolates were highly resistant to sulfonamides(resistance rate>85%)and chloramphenicol(resistance rate>30%),and they were relatively low resistant to ampicillin(9.5%),ciprofloxacin(9.5%),ceftiofur(7.1%)and ofloxacin(4.8%).The results was able to provide reliable theoretical basis for prevention and control of dairy cow mastitis in Liaoning area. 相似文献
74.
75.
76.
77.
弱光条件下桃光合作用的动态变化及品种差异分析 总被引:3,自引:1,他引:3
就日光温室桃树光合生理进行了详尽的研究,结果表明:1d中叶温与气温以14:00时较高。遮阴明显地降低了到达叶片表面的有效光合辐射、叶温与气温。桃叶片的光合速率日变化为双峰曲线,峰值大约出现在上午10:00与下午14:00时;不同品种弱光下的光合速率有明显的差异,以NJN较高,其次为五月火与麦香。遮阴降低了桃叶片的光合速率,以NJN光合速率降低的较少,说明NJN能适应设施栽培。气孔阻力与蒸腾速率则随着遮阴程度的增加而增加。桃中位叶的光合速率较幼叶高。 相似文献
78.
Condition assessment on power transformer is an important approach to improve reliability of transformer and provide proper decision-making for condition-based maintenance. For long, static assessment method used in the past has already not adapted to the development of modem electricity transmission and distribution technology. So based on the deficiency of fuzzy synthetic assessment method, matter-element synthetic assessment method is introduced. The method can evaluate transformer condition not only in quality but also in quantity. Because each index weight can be given fairly and fast through improved analytic hierarchy process, which need not carry on consistency chec accuracy of assessment can be improved. Examples analysis has proved that assessment method of power transformer condition based on matter-element theory is rational and effective. 相似文献
79.
Yao Jiafei 《保鲜与加工》1994,(2)
This paper discusses the model for lifting capacity of the crane and optimal con-trol of eliminating swing in lifting process. One half loop control method is presented, which is onlyto examine and measure the trolley speed for eleiminating swing.The fact shows this methOd is sim-ple and practicle for enginceering. 相似文献
80.