全文获取类型
收费全文 | 28128篇 |
免费 | 1827篇 |
国内免费 | 1184篇 |
专业分类
电工技术 | 634篇 |
综合类 | 2123篇 |
化学工业 | 3320篇 |
金属工艺 | 1043篇 |
机械仪表 | 1405篇 |
建筑科学 | 1873篇 |
矿业工程 | 509篇 |
能源动力 | 993篇 |
轻工业 | 1457篇 |
水利工程 | 175篇 |
石油天然气 | 799篇 |
武器工业 | 142篇 |
无线电 | 3000篇 |
一般工业技术 | 4079篇 |
冶金工业 | 1393篇 |
原子能技术 | 160篇 |
自动化技术 | 8034篇 |
出版年
2024年 | 56篇 |
2023年 | 339篇 |
2022年 | 654篇 |
2021年 | 529篇 |
2020年 | 592篇 |
2019年 | 708篇 |
2018年 | 497篇 |
2017年 | 685篇 |
2016年 | 760篇 |
2015年 | 715篇 |
2014年 | 1036篇 |
2013年 | 1034篇 |
2012年 | 1397篇 |
2011年 | 1511篇 |
2010年 | 911篇 |
2009年 | 1350篇 |
2008年 | 1114篇 |
2007年 | 1112篇 |
2006年 | 1026篇 |
2005年 | 867篇 |
2004年 | 1489篇 |
2003年 | 1221篇 |
2002年 | 1800篇 |
2001年 | 1458篇 |
2000年 | 1303篇 |
1999年 | 1104篇 |
1998年 | 678篇 |
1997年 | 716篇 |
1996年 | 1630篇 |
1995年 | 899篇 |
1994年 | 652篇 |
1993年 | 189篇 |
1992年 | 160篇 |
1991年 | 180篇 |
1990年 | 151篇 |
1989年 | 86篇 |
1988年 | 70篇 |
1987年 | 49篇 |
1986年 | 68篇 |
1985年 | 74篇 |
1984年 | 52篇 |
1983年 | 37篇 |
1982年 | 38篇 |
1981年 | 36篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
利用全息技术对本振光束进行调制以实现与信号光束的匹配,进而提高外差效率的原理及实施方法,介绍了作为调制器用的全息位相光栅的研制技术,为在外差探测系统中应用全息技术提供了依据。 相似文献
982.
在北天东雷达直角坐标系内建立了再入目标的动力学方程及雷达测量方程,目标机动特性采用-阶马尔科夫过程描述。根据给定的在目标直角坐标系中的再入机动目标的弹道数据形成了雷达模拟测量信息。以上工作为再入机动目标的跟踪与弹道预报奠定了基础。 相似文献
983.
浅谈柔性制造系统的现状及实施 总被引:1,自引:0,他引:1
冯健民 《组合机床与自动化加工技术》1997,(11):30-33
本文以美国所用柔性制造系统为例,以大量翔实的数据。阐述了柔性制造系统使用的现状及存在的问题,并针对这些问题提出相应的措施。 相似文献
984.
985.
986.
Andrey V. Savkin 《Systems & Control Letters》1998,33(5):281-289
This paper considers the problem of simultaneous H∞ control of a finite collection of linear time-invariant systems via a nonlinear digital output feedback controller. The main result is given in terms of the existence of suitable solutions to Riccati algebraic equations and a dynamic programming equation. Our main result shows that if the simultaneous H∞ control problem for k linear time-invariant plants of orders n1,n2,…,nk can be solved, then this problem can be solved via a nonlinear time-invariant controller of order nn1+n2++nk. 相似文献
987.
Minos N. Garofalakis Banu Özden Avi Silberschatz 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):206-225
The Enhanced Pay-Per-View (EPPV) model for providing continuous-media services associates with each continuous-media clip
a display frequency that depends on the clip's popularity. The aim is to increase the number of clients that can be serviced
concurrently beyond the capacity limitations of available resources, while guaranteeing a constraint on the response time.
This is achieved by sharing periodic continuous-media streams among multiple clients. The EPPV model offers a number of advantages
over other data-sharing schemes (e.g., batching), which make it more attractive to large-scale service providers. In this
paper, we provide a comprehensive study of the resource-scheduling problems associated with supporting EPPV for continuous-media
clips with (possibly) different display rates, frequencies, and lengths. Our main objective is to maximize the amount of disk
bandwidth that is effectively scheduled under the given data layout and storage constraints. Our formulation gives rise to
-hard combinatorial optimization problems that fall within the realm of hard real-time scheduling theory. Given the intractability
of the problems, we propose novel heuristic solutions with polynomial-time complexity. We also present preliminary experimental
results for the average case behavior of the proposed scheduling schemes and examine how they compare to each other under
different workloads. A major contribution of our work is the introduction of a robust scheduling framework that, we believe,
can provide solutions for a variety of realistic EPPV resource-scheduling scenarios, as well as any scheduling problem involving
regular, periodic use of a shared resource. Based on this framework, we propose various interesting research directions for
extending the results presented in this paper.
Received June 9, 1998 / Accepted October 13, 1998 相似文献
988.
Identifying and tracking changing interests 总被引:4,自引:0,他引:4
989.
Praveen Seshadri 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(3):130-140
The explosion in complex multimedia content makes it crucial for database systems to support such data efficiently. This
paper argues that the “blackbox” ADTs used in current object-relational systems inhibit their performance, thereby limiting
their use in emerging applications. Instead, the next generation of object-relational database systems should be based on
enhanced abstract data type (E-ADT) technology. An (E-ADT) can expose the semantics of its methods to the database system, thereby permitting advanced query optimizations. Fundamental architectural changes
are required to build a database system with E-ADTs; the added functionality should not compromise the modularity of data
types and the extensibility of the type system. The implementation issues have been explored through the development of E-ADTs
in Predator. Initial performance results demonstrate an order of magnitude in performance improvements.
Received January 1, 1998 / Accepted May 27, 1998 相似文献
990.
Jung-Hong Chuang Christoph M. Hoffmann Kun-Ming Ko Wei-Chung Hwang 《The Visual computer》1998,14(10):455-470
n -dimensional space, where n>3. This definition can be used for given surfaces that are implicit or parametric. This paper presents a robust, adaptive
polygonization algorithm for evaluating and visualizing geometrically constrained surfaces. Let be the constrained surface, a 2-surface in n-space, and let π() be its projection into the subspace spanned by the first three coordinates. Our polygonization algorithm computes π(). The method works directly with the n-space representation, but performs all major computations in 3-space. Techniques for triangulation, polygon decimation, and
local refinement are also presented. 相似文献