全文获取类型
收费全文 | 8656篇 |
免费 | 458篇 |
国内免费 | 1155篇 |
专业分类
林业 | 830篇 |
农学 | 1030篇 |
基础科学 | 781篇 |
954篇 | |
综合类 | 3969篇 |
农作物 | 1237篇 |
水产渔业 | 260篇 |
畜牧兽医 | 677篇 |
园艺 | 276篇 |
植物保护 | 255篇 |
出版年
2024年 | 16篇 |
2023年 | 114篇 |
2022年 | 194篇 |
2021年 | 205篇 |
2020年 | 211篇 |
2019年 | 238篇 |
2018年 | 192篇 |
2017年 | 264篇 |
2016年 | 344篇 |
2015年 | 336篇 |
2014年 | 427篇 |
2013年 | 402篇 |
2012年 | 632篇 |
2011年 | 647篇 |
2010年 | 545篇 |
2009年 | 534篇 |
2008年 | 524篇 |
2007年 | 601篇 |
2006年 | 543篇 |
2005年 | 432篇 |
2004年 | 356篇 |
2003年 | 357篇 |
2002年 | 299篇 |
2001年 | 281篇 |
2000年 | 247篇 |
1999年 | 203篇 |
1998年 | 148篇 |
1997年 | 167篇 |
1996年 | 117篇 |
1995年 | 136篇 |
1994年 | 99篇 |
1993年 | 90篇 |
1992年 | 85篇 |
1991年 | 55篇 |
1990年 | 71篇 |
1989年 | 50篇 |
1988年 | 35篇 |
1987年 | 29篇 |
1986年 | 15篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
111.
112.
113.
With the study of minbus's accelerated exterior noise control,the principle of sound intensity measurement was applied,the sound intensity of a minbus's surface noise was tested,and the surface noise distribution was presented.Several identification of noise source methods including sound power,sound intensity contour map,frequency spectrum were used together for surface noise analysis and study.Engine radiation noise and exhaust noise was identified as the major noise sources.On the contrary,car body vibration noise,tyre noise,transmission agent noise,air admission noise just occupied a little proportion of surface sound radiation energy.The research provides the reliable basis to determine main projects of minibus's accelerated exterior noise control. 相似文献
114.
The design of multi-controller and multi-mode control law is presented for the three-link Acrobot on horizontal bar by employing Human simulated intelligent control method based on sensory-motor Schema.Imitated the characteristics of gymnast's swing-up and handstand movement,the control process of robot is divided by six sequence phase.Then the sensory cell and motor cell and the group of sensory-motor schema is designed based on the analysis of quality-quantity combination.The simulation results show that the controller ensures the gesture and the energy to the desired goal,farther more the motion control of giant swing backword is realized in the simulation. 相似文献
115.
Zhang Jin Hu Zhenji Zhou Shangqi 《保鲜与加工》1991,(3):44-47
The phase transformation in the diffusion layer after slow cooling and aging of pure iron ion -nitrided was investigated with TEM. Refering to principle of Moire method measuring macroscopical strain, the values of coherent strain at interfaces between a" and aN phases were determined by means of TEM analyses. 相似文献
116.
This paper analyzes contractor's pricing connotation during bidding period with the implementation of National Standard GB50500-2003 and publish of document JB \206,expatiates the contents of measurements during construction period.Considering the problems derived from expenses of measurements during accounts settlement stage,a classified management method according to the characteristics of these measurements is put forward,and one step further,the rational pricing method of measurement items during the bidding period is suggested. 相似文献
117.
This paper introduces a method of solving the problem of leather cavity measurement in shoe CAD/CAM by industrial CT technology. Concentrating on peculiarity and requirement of leather cavity measurement, this paper presents a X-ray industrial CT system scheme, which not only satisfy the requirement of leather cavity measurement but also can achieve general industrial CT. measurement. The achievement on data collection system and motion control of stepping motor is emphasized. 相似文献
118.
The exact computing of house architectural area and apportionment of area is strongly related to the actual interests of people. If it is done manually,there are many problem such as longer time spending, more workload, requiring detailed verification, nonstandard calculating report. Using ActiveX automation and ADO techniques, the house architectural area computing and plotting system was developed under Autocad R14 environment with VB 6.0 and Access database in order to solve above problem. The developed system can automatically compute house architectural area and apportionment of area for each floor of each building and can print the related data report and drawing. The system works well in many departments of house measurement. Several key technical problem of the system are discussed. 相似文献
119.
Based on the principles of operational risk measurement provided by Basel II,the paper discusses the problem of operational risk correlations among different business lines / risk types.The correlation coefficients between the aggregate losses among different business lines / risk types are calculated.Copula arithmetic is put forward to compute correlation coefficients matrix of aggregate losses.Besides,the result is used to calculate the capital requirement of operational risk. 相似文献
120.
:In
accordance with the problems, occurred in the mountainous city's construction, especially
the crises such as the destruction of ecological and humanistic environment, the loss of
traditional culture and characteristics and the disorder of urban structure, this paper
discusses the distinctive landscape characteristic of mountainous city thoroughly. 相似文献