全文获取类型
收费全文 | 452599篇 |
免费 | 26491篇 |
国内免费 | 28112篇 |
专业分类
林业 | 28565篇 |
农学 | 20513篇 |
基础科学 | 16959篇 |
48412篇 | |
综合类 | 179744篇 |
农作物 | 26780篇 |
水产渔业 | 19766篇 |
畜牧兽医 | 116798篇 |
园艺 | 26107篇 |
植物保护 | 23558篇 |
出版年
2024年 | 2568篇 |
2023年 | 6570篇 |
2022年 | 14448篇 |
2021年 | 14738篇 |
2020年 | 13862篇 |
2019年 | 14045篇 |
2018年 | 11421篇 |
2017年 | 16996篇 |
2016年 | 11829篇 |
2015年 | 16949篇 |
2014年 | 18602篇 |
2013年 | 24959篇 |
2012年 | 31044篇 |
2011年 | 33278篇 |
2010年 | 30382篇 |
2009年 | 27640篇 |
2008年 | 29566篇 |
2007年 | 27159篇 |
2006年 | 22716篇 |
2005年 | 18537篇 |
2004年 | 13074篇 |
2003年 | 9636篇 |
2002年 | 9352篇 |
2001年 | 9537篇 |
2000年 | 9189篇 |
1999年 | 5075篇 |
1998年 | 1648篇 |
1997年 | 1511篇 |
1996年 | 1355篇 |
1995年 | 1625篇 |
1994年 | 1461篇 |
1993年 | 1322篇 |
1992年 | 2690篇 |
1991年 | 2775篇 |
1990年 | 2634篇 |
1989年 | 2638篇 |
1988年 | 2384篇 |
1987年 | 2398篇 |
1986年 | 2483篇 |
1985年 | 2347篇 |
1984年 | 1882篇 |
1983年 | 1677篇 |
1979年 | 1749篇 |
1978年 | 1397篇 |
1975年 | 1292篇 |
1974年 | 1500篇 |
1973年 | 1515篇 |
1972年 | 1405篇 |
1971年 | 1304篇 |
1969年 | 1283篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
54.
为建立一种针对寨卡病毒的快速诊断方法,本研究根据寨卡病毒的3’端保守基因序列,设计合成1对引物,建立了检测寨卡病毒的荧光定量PCR方法。结果显示:所建立的检测方法的Ct值与标准品在1.41×10^1~1.41×10^10^ copies/μL具有良好的线性关系,相关性为1,斜率为-3.502;灵敏性结果显示,该方法的检测限度为1.41×10^1 copies/μL,是普通PCR的10000倍;特异性结果显示,对CHIKV、DENV和JEV无特异性扩增,特异性强;重复性试验结果显示,组内和组间变异系数均小于1%,重复性好。本研究建立的SYBR Green I real-time PCR检测方法,可用于寨卡病毒感染的快速诊断。 相似文献
55.
为确保科技项目查新的客观性、真实性、及时有效性,完成科技查新报告,中北大学图书馆自主开发了科技查新管理系统。该系统基于SSH框架进行设计,主要包括了科技查新工作所需的用户业务流程和后台管理流程,并通过严格的授权管理机制对系统加以保障。文章分析了系统的功能,给出了系统的体系结构及系统实现的关键技术。 相似文献
56.
伴随多元化时代的来临,用户的知识需求日益多元化、专业化,对图书馆服务提出了新的挑战。对智慧图书馆微观知识生态系统运行机理的研究,能够为新型知识服务提供理论基础,保障知识资源进行有效的优化整合,实现服务升级。文章在简要分析智慧图书馆微观知识生态系统四大要素的基础上,着重从社会发展、技术进步,知识富集、优化调整和需求驱动、服务升级三方面探讨其形成动因,重点分析智慧图书馆微观知识生态系统的生命周期,最后从合作、循环和保障三方面探讨其运行机理。 相似文献
57.
58.
T. Pudert A. Weyrich F. Geburek C. Herden M. Röcken 《Equine Veterinary Education》2021,33(11):e386-e392
Thymoma is a rare condition in horses. This case of a 24-year-old Warmblood gelding that was presented with oedema and signs of vascular congestion of the left forelimb caused by a thoracic mass is described. The diagnostic work-up included blood chemistry, cytology of pleural effusion, ultrasonography, radiography and the visualisation and collection of a tissue sample by thoracoscopy. Finally, post-mortem findings and histopathology revealed thymic epithelial neoplasia with histomorphologic features previously unreported in horses. The unique mixture of spindle-shaped and epithelioid tumour cells in combination with clear features of malignancy suggested the application of the Moran and Suster histological classification system for thymomas in humans (Moran and Suster, 2008, Curr. Treat. Options Oncol., 9, 288), which has not been reported in an equine case before and fits well to the present case. 相似文献
59.
Protective efficacy of an H5/H7 trivalent inactivated vaccine produced from Re-11, Re-12, and H7-Re2 strains against challenge with different H5 and H7 viruses in chickens 下载免费PDF全文
ZENG Xian-ying CHEN Xiao-han MA Shu-jie WU Jiao-jiao BAO Hong-mei PAN Shu-xin LIU Yan-jing DENG Guo-hua SHI Jian-zhong CHEN Pu-cheng JIANG Yong-ping LI Yan-bing HU Jing-lei LU Tong MAO Sheng-gang GUO Xing-fu LIU Jing-li TIAN Guo-bin CHEN Hua-lan 《农业科学学报》2020,19(9):2294-2300
We developed an H5/H7 trivalent inactivated vaccine by using Re-11, Re-12, and H7-Re2 vaccine seed viruses, which were generated by reverse genetics and derived their HA genes from A/duck/Guizhou/S4184/2017(H5 N6)(DK/GZ/S4184/17)(a clade 2.3.4.4 d virus), A/chicken/Liaoning/SD007/2017(H5 N1)(CK/LN/SD007/17)(a clade 2.3.2.1 d virus), and A/chicken/Guangxi/SD098/2017(H7 N9)(CK/GX/SD098/17), respectively. The protective efficacy of this novel vaccine and that of the recently used H5/H7 bivalent inactivated vaccine against different H5 and H7 N9 viruses was evaluated in chickens. We found that the H5/H7 bivalent vaccine provided solid protection against the H7 N9 virus CK/GX/SD098/17, but only 50–60% protection against different H5 viruses. In contrast, the novel H5/H7 trivalent vaccine provided complete protection against the H5 and H7 viruses tested. Our study underscores the importance of timely updating of vaccines for avian influenza control. 相似文献
60.
Do cover crops change the lability of phosphorus in a clayey subtropical soil under different phosphate fertilizers? 下载免费PDF全文
A. P. B. Teles M. Rodrigues W. F. Bejarano Herrera A. Soltangheisi L. R. Sartor P. J. A. Withers P. S. Pavinato 《Soil Use and Management》2017,33(1):34-44
Plants have developed different mechanisms to absorb and solubilize phosphorus (P) in the soil, especially in environments with low P availability. This study evaluated the effects of different winter cover crops on soil P availability in a clayey subtropical (Hapludox) soil receiving soluble P fertilizer and a rock phosphate applied to the summer crop, under no‐tillage. The experiment was carried out over 3 yrs (2009–2011) with five different cover crop species: common vetch, fodder radish, ryegrass, black oat, white clover and fallow as control. The soil was sampled after the third year of cover crop cultivation and analysed for inorganic and organic P forms according to the well‐established Hedley fractionation procedure. Phosphate fertilizers promoted accumulation of both labile and nonlabile P pools in soil in the near surface layer, especially under rock phosphate. Fertilizer applications were not able to change P fractions in deeper layers, emphasizing that the Brazilian clayey soils are a sink of P from fertilizer and its mobility is almost nil. Although the cover crops recycled a great amount of P in tissue, in a short‐term evaluation (3 yrs) they only changed the content of moderately labile P in soil, indicating that long‐term studies are needed for more conclusive results. 相似文献