全文获取类型
收费全文 | 18440篇 |
免费 | 977篇 |
国内免费 | 1895篇 |
专业分类
林业 | 2533篇 |
农学 | 2855篇 |
基础科学 | 1584篇 |
3084篇 | |
综合类 | 5208篇 |
农作物 | 909篇 |
水产渔业 | 769篇 |
畜牧兽医 | 2447篇 |
园艺 | 537篇 |
植物保护 | 1386篇 |
出版年
2024年 | 46篇 |
2023年 | 210篇 |
2022年 | 496篇 |
2021年 | 688篇 |
2020年 | 661篇 |
2019年 | 590篇 |
2018年 | 423篇 |
2017年 | 625篇 |
2016年 | 607篇 |
2015年 | 774篇 |
2014年 | 746篇 |
2013年 | 892篇 |
2012年 | 1007篇 |
2011年 | 1109篇 |
2010年 | 1061篇 |
2009年 | 1056篇 |
2008年 | 1006篇 |
2007年 | 1039篇 |
2006年 | 1045篇 |
2005年 | 993篇 |
2004年 | 446篇 |
2003年 | 406篇 |
2002年 | 304篇 |
2001年 | 369篇 |
2000年 | 426篇 |
1999年 | 567篇 |
1998年 | 508篇 |
1997年 | 459篇 |
1996年 | 452篇 |
1995年 | 384篇 |
1994年 | 333篇 |
1993年 | 305篇 |
1992年 | 291篇 |
1991年 | 265篇 |
1990年 | 192篇 |
1989年 | 164篇 |
1988年 | 126篇 |
1987年 | 77篇 |
1986年 | 45篇 |
1985年 | 29篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Guang Rong Jun-Ming Zhao Guan-Yu Hou Han-Lin Zhou 《Tropical animal health and production》2014,46(8):1491-1495
In the present study, the seroprevalence and genetic identification of Mycoplasma ovipneumoniae infection in goats were investigated in Hainan Province, tropical China between October 2012 and October 2013. A total of 1,210 serum samples collected from 16 herds in various administrative regions in tropical China were evaluated using indirect hemagglutination assay (IHA). Antibodies to M. ovipneumoniae were tested in (31.7 %, 95 % confidence interval (CI) 29–34.3) 383 of 1,210 serum samples (IHA titer ≥1:16). The M. ovipneumoniae seroprevalence ranged from 26.8 % (95 % CI 20.8–32.9) to 39 % (95 % CI 30.8–47.2) among different regions in tropical China, and the difference was statistically significant (P?<?0.01). The seroprevalence of M. ovipneumoniae infection in goats was higher in winter (46.1 %, 95 % CI 39.6–52.5) and spring (33.8 %, 95 % CI 28.3–39.3) than in autumn (27.5 %, 95 % CI 22.6–32.3) and summer (24.7 %, 95 % CI 20.3–29.1), and the difference was statistically significant (P?<?0.01). In addition, DNA was extracted from nasal swab; lung samples and the 16S rRNA gene sequences were amplified by polymerase chain reaction (PCR) and then sequenced. Twenty-four of 329 (7.3 %) nasal swab samples and 73 of 280 (26.1 %) pneumonic lung tissues were found to contain M. ovipneumoniae, respectively. The results of the present survey indicate that M. ovipneumoniae infection is highly prevalent in goats in tropical China. This is the first report of the comprehensive survey of M. ovipneumoniae prevalence in goats in China. 相似文献
992.
993.
G. Yang R. Forrest H. Zhou S. Hodge J. Hickford 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2014,131(6):437-444
The uncoupling protein 1 (UCP1) plays an important role in the regulation of lipolysis and thermogenesis in adipose tissues. Genetic variation within three regions (the promoter, intron 2 and exon 5) of the ovine UCP1 gene (UCP1) was investigated using polymerase chain reaction‐single‐strand conformational polymorphism (PCR‐SSCP) analyses. These revealed three promoter variants (designated A, B and C) and two intron 2 variants (a and b). The association of this genetic variation with variation in lamb carcass traits and postweaning growth was investigated in New Zealand (NZ) Romney and Suffolk sheep. The presence of B in a lamb's genotype was associated with decreased subcutaneous carcass fat depth (V‐GR) (p = 0.004) and proportion of total lean meat yield of loin meat (p = 0.005), and an increased proportion of total lean meat yield of hind‐leg meat (p = 0.018). In contrast, having two copies of C was associated with increased V‐GR (p < 0.001) and proportion of total lean meat yield of shoulder meat (p = 0.009), and a decreased hind‐leg yield (p = 0.032). No associations were found with postweaning growth. These results suggest that ovine UCP1 is a potential gene marker for carcass traits. 相似文献
994.
995.
996.
Bioassays and scanning electron microscopy of Conidiobolus obscurus for bamboo aphids as well as its effects on the fecundity of bamboo aphids were carried out to estimate bamboo aphid biocontrol potential. Multi-concentration bioassay and fecundity assessment were performed on aphid species of Takecallis taiwanus, Takecallis arundinariae, Melanaphis bambusae, and Metamacropodaphis bambusisucta. C. obscurus can effectively infect four species of bamboo aphids, and most cadavers appeared in the first 2 days after inoculation. The final mortalities reached 74–91 % at high concentrations of conidia among the tested species. Based on the fitted time–concentration–mortality models, the estimates of the median lethal concentration (LC50) of the fungal conidia differed significantly among different aphid species and decreased with observation days. The lowest LC50 was estimated to be 57 conidia mm?2 for T. taiwanus on day 5 after conidial shower. Moreover, the C. obscurus-infected aphids only produced 3.9–18.2 % progeny of the corresponding healthy aphids, which strongly presented fungal influence on host fecundity. In conclusion, C. obscurus has the ability of restraining the development of bamboo aphid populations, which is suitable for further application in aphid biocontrol in bamboo forests. 相似文献
997.
998.
农村水污染现状及防治对策 总被引:1,自引:0,他引:1
指出了由于农业生产方式的转变,乡镇企业的崛起,农民生活方式以及环保意识薄弱等原因,使农村水污染问题日益突出,农村水环境保护工作有待加强,农村水环境立法有待完善。通过简要分析我国农村水污染现状,结合农村水污染治理的方法及政策经验,提出了合理化建议,以期规范和提高农村水污染治理水平。 相似文献
999.
采用专家判读、AHP法、指数衰减法、加权法对平煤天安股份五矿矿区土地系统存在的生态环境压力进行了综合评价。结果表明:平煤天安股份五矿矿区土地系统生态环境总压力整体为,轻度环境压力(202hm2,32.90%)>中度环境压力(190hm2,30.94%)>中高度环境压力(154hm2,25.08%)>高强度环境压力(68hm2,11.07%)。其中,资源消耗压力A2最大,其次为环境污染压力A3、生产规模压力A4,自然环境压力A1最小。在评价基础上利用矿区土地的自然环境压力和人为生产压力的分异性,将矿区的土地系统分为保护型、消费型、生产型和调和型4种土地生态功能类型和11种土地生态类型区;平煤天安股份五矿矿区土地利用状况呈现不合理的利用状态,主要体现在具有生态保护功能的保护型土地生态系统的总面积仅为4.94hm2,占地比例为13.1%。 相似文献
1000.