全文获取类型
收费全文 | 6423篇 |
免费 | 397篇 |
国内免费 | 613篇 |
专业分类
林业 | 379篇 |
农学 | 302篇 |
基础科学 | 243篇 |
619篇 | |
综合类 | 3347篇 |
农作物 | 512篇 |
水产渔业 | 326篇 |
畜牧兽医 | 922篇 |
园艺 | 537篇 |
植物保护 | 246篇 |
出版年
2024年 | 51篇 |
2023年 | 116篇 |
2022年 | 311篇 |
2021年 | 308篇 |
2020年 | 285篇 |
2019年 | 285篇 |
2018年 | 173篇 |
2017年 | 288篇 |
2016年 | 209篇 |
2015年 | 346篇 |
2014年 | 312篇 |
2013年 | 383篇 |
2012年 | 587篇 |
2011年 | 583篇 |
2010年 | 500篇 |
2009年 | 440篇 |
2008年 | 497篇 |
2007年 | 459篇 |
2006年 | 373篇 |
2005年 | 272篇 |
2004年 | 155篇 |
2003年 | 109篇 |
2002年 | 117篇 |
2001年 | 104篇 |
2000年 | 102篇 |
1999年 | 33篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1963年 | 1篇 |
1962年 | 3篇 |
1956年 | 3篇 |
1955年 | 3篇 |
排序方式: 共有7433条查询结果,搜索用时 20 毫秒
61.
土质边坡稳定安全系数的计算值主要与采用的简化计算方法和土工参数有关。采用正交试验法计算分析了不同的计算方法、材料参数、水位及其相关荷载、地震作用等对边坡安全系数计算值的影响,进而对设计中的计算方法和材料参数提出了一些有益的建议,并提出了在工程运行管理中应尽量避免低水位或水位骤降情况的意见,为土石坝类工程的设计与运行管理提供了重要参考。 相似文献
62.
63.
The cavity induced by top-blow gas jets impinging on the bath surface is one of most important parameters, which has overwhelming influence on the rate of slag formation and metallurgical performance. Water model experiments are conducted through a 1/10 scaled-down top-blown convertor. Effects of lance height and gas flow rate on penetration behavior are studied, and also the influence mechanism of liquid surface tension on penetration depth is addressed based on the experiments and theory analysis. An energy utilization index (EUI) is defined to reflect how much the impinging kinetic energy of gas jets are transferred into bath for formation of cavity, and an improved model is proposed to predict penetration depth of jets. The results show that penetration depth increases with lowering lance height and increasing gas flow rate, and impact diameter increases with increasing lance height, but is little affected by gas flow rate. Influence of liquid surface tension on penetration depth is enhanced with increasing surface tension and penetration depth. The EUI increases with increasing lance height, and a function relationship of it with lance height is obtained based on the experiments. 相似文献
64.
The externality of surrounding is introduced into the 2-capital of economical increasing models, which includes human factors, to explore the influences of circumstances contradiction on the human capital formation. The normal and special nash equilibrium of environmental and human capital is presented through a limited boundary model of overlapping generations. The character of equilibrium trail and its economical meaning are examined. The study on the model shows that laissez faire economy will be either stagnant,growing,or collapsing in the long-run,depending on the returns of the learning technology with respect to the two kinds of capital,the initial state of economy,and the relative price of the environmental and consumption goods. 相似文献
65.
YANG Zhong-ren RAO Cheng ZOU Jian PENG Zhen-liane Ministry of Education Chongqing Chin 《保鲜与加工》2004,(2):32-35
Dong village is very valuable for research work because of its special regional and national character and rich cultural implication. In this paper, some information about the location, form and features of Dong village is given. Then, the relationship between the culture and the settlement is analyzed, which provides a clue for understanding Dong village and will be beneficial to creating modern human settlements. 相似文献
66.
Pushover analysis is a tool to study the inelastic behavior of structures under strong seismic action. The 3D-pushover analysis was performed to analyze the inelastic lateral-torsional coupled response of multistory asymmetric structures. The symmetric frame and frame-wall systems were studied in this paper, and the capability curve of the top displacement and base shear,the story drift and the position of rotation center were compared with reference to corresponding symmetric structures. The characters of inelastic response of multistory asymmetric structures were found. The conclusion provides reference for performance-based seismic design of asymmetric structures. 相似文献
67.
68.
69.
70.