全文获取类型
收费全文 | 121544篇 |
免费 | 19484篇 |
国内免费 | 13952篇 |
专业分类
电工技术 | 13885篇 |
技术理论 | 2篇 |
综合类 | 15797篇 |
化学工业 | 5317篇 |
金属工艺 | 3473篇 |
机械仪表 | 10386篇 |
建筑科学 | 6844篇 |
矿业工程 | 2925篇 |
能源动力 | 3045篇 |
轻工业 | 1727篇 |
水利工程 | 2982篇 |
石油天然气 | 2294篇 |
武器工业 | 2219篇 |
无线电 | 16399篇 |
一般工业技术 | 10104篇 |
冶金工业 | 1841篇 |
原子能技术 | 508篇 |
自动化技术 | 55232篇 |
出版年
2024年 | 853篇 |
2023年 | 2079篇 |
2022年 | 3782篇 |
2021年 | 4147篇 |
2020年 | 4602篇 |
2019年 | 3913篇 |
2018年 | 3845篇 |
2017年 | 4682篇 |
2016年 | 5400篇 |
2015年 | 6080篇 |
2014年 | 8161篇 |
2013年 | 8240篇 |
2012年 | 9939篇 |
2011年 | 10140篇 |
2010年 | 8205篇 |
2009年 | 8380篇 |
2008年 | 8653篇 |
2007年 | 9706篇 |
2006年 | 7952篇 |
2005年 | 6576篇 |
2004年 | 5308篇 |
2003年 | 4350篇 |
2002年 | 3462篇 |
2001年 | 2880篇 |
2000年 | 2542篇 |
1999年 | 2016篇 |
1998年 | 1633篇 |
1997年 | 1403篇 |
1996年 | 1140篇 |
1995年 | 908篇 |
1994年 | 790篇 |
1993年 | 605篇 |
1992年 | 535篇 |
1991年 | 372篇 |
1990年 | 338篇 |
1989年 | 299篇 |
1988年 | 216篇 |
1987年 | 110篇 |
1986年 | 98篇 |
1985年 | 88篇 |
1984年 | 103篇 |
1983年 | 68篇 |
1982年 | 76篇 |
1981年 | 41篇 |
1980年 | 60篇 |
1979年 | 54篇 |
1978年 | 23篇 |
1977年 | 31篇 |
1976年 | 18篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Chia‐Yin Chen Yu‐Chi Cheng Shau‐Wei Tsai 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(6):699-705
A lipase‐catalyzed enantioselective hydrolysis process under in situ racemization of the remaining (R)‐thioetser substrate with trioctylamine as the catalyst was developed for the production of (S)‐fenoprofen from (R,S)‐fenoprofen 2,2,2‐trifluoroethyl thioester in isooctane. Detailed investigations of trioctylamine concentration on the enzyme activation and the kinetic behavior of the thioester in racemization and enzymatic reactions were conducted, in which good agreement between the experimental data and theoretical results was observed. © 2002 Society of Chemical Industry 相似文献
102.
基于约束优化的联想记忆模型学习算法 总被引:1,自引:1,他引:0
本文提出了一种对称互连神经元网络的学习策略,利用全局约束优化方法确定连接权。优化过程采用了梯度下降技术。这种学习算法可以保证训练样本成为系统的稳定吸引子,并且具有优化意义上的最大吸引域。本文讨论了网络的存储容量,训练样本的渐近稳定性和吸引域大小。计算机实验结果说明了学习算法的优越性。 相似文献
103.
提出种基于TEMIC射频卡Manchester编码的速率自适应读卡算法,并对该算法进行了说明和示例。 相似文献
104.
文章讨论了OSPF路由协议的扩散算法在多冗余点到点链路情况下存在的缺陷,提出了一种基于扩散接口选举的改进方案。 相似文献
105.
106.
Aiming at the detail rendering in volume data, a new volume illumination model, called Composed Scattering Model (CSM), is presented. In order to enhance different details in volume data, scattering intensity is decomposed into volume scattering intensity and surface scattering intensity with different weight functions. According to the Gauss probability distribution of gray and gradient of data, we propose an accurate method to detect the materials in a voxel, called composed segmentation. In addition, we discuss the principle of constructing these weight functions based on the operators defined in composed segmentation. CSM can generate images containing more details than most popular volume rendering models. This model has been applied to the direct volume rendering of 3D data sets obtained by CT and MRI. The resultant images show not only rich details but also clear boundary surfaces. CSM is demonstrated as an accurate volume rendering model suited for detail enhancement in volume data sets. 相似文献
107.
Jaroslav Mackerle 《International Journal of Pressure Vessels and Piping》1996,69(3):279-339
The paper gives a bibliographical review of the finite element methods (FEMs) applied for the analysis of pressure vessel structures/components and piping from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore the aim of this review is to give the reader an encyclopaedic view of the differnt possibilities that exist today for the finite element analysis in the fields of pressure vessels and piping. The bibliography at the end of the paper contains approximately 1900 references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. These are classified in the following categories: linear and non-linear, static and dynamic, stress and deflection analysis; stability problems; thermal problems; fracture mechanics problems; contact problems; fluid-structure interaction problems; manufacturing of pipes and tubes; welded pipes and pressure vessel components; development of special finite elements for pressure vessels and pipes; finite element software; and other topics. Also finite element software, general purpose and special purpose codes, used for the analysis of pressure vessels and pipes are briefly discussed and presented. 相似文献
108.
109.
介绍了自行设计的,不依赖其他软件支持而存在,可直接运行在Intel80376、80386、80486和80586处理器的计算机上,便于移植的一个完全独立的实时操作系统—FCCRTOS。其特点为:32位寻址、内存保护模式的段式管理、多任务并发处理、实时事件线程管理、支持多总线通信协议、模块化设计及目标程序完全ROM化等。 相似文献
110.
In this paper, we study a manufacturing system consisting of two machines separated by two intermediate buffers, and capable of producing two different products. Each product requires a constant processing time on each of the machines. Each machine requires a constant non-negligible setup change time from one product to the other. The demand rate for each product is considered to be piecewise constant. Each machine undergoes failure and repair. The time-to-failure and time-to-repair are exponentially distributed random variables. The setup change and processing operations are resumable. We model our system as a continuous time, continuous flow process. An optimal control problem is formulated for the system to minimize the total expected discounted cost over an infinite horizon. To determine the optimal control policy structure, a discrete version of the problem is solved numerically using a dynamic programming formulation with a piecewise linear penalty function. A real-time control algorithm is then developed with the objective of maintaining low work-in-process inventory and keeping the production close to the demand. The algorithm uses a hierarchical control structure to generate the loading times for each product on each machine in real time and to respond to random disruptions in the system. The system is simulated using this algorithm to study its performance. The performance of the algorithm is also compared to alternative policies. 相似文献