全文获取类型
收费全文 | 90518篇 |
免费 | 16352篇 |
国内免费 | 11833篇 |
专业分类
电工技术 | 10500篇 |
技术理论 | 4篇 |
综合类 | 11723篇 |
化学工业 | 2727篇 |
金属工艺 | 2077篇 |
机械仪表 | 7563篇 |
建筑科学 | 2366篇 |
矿业工程 | 1557篇 |
能源动力 | 1903篇 |
轻工业 | 1251篇 |
水利工程 | 1714篇 |
石油天然气 | 1812篇 |
武器工业 | 1487篇 |
无线电 | 15625篇 |
一般工业技术 | 7169篇 |
冶金工业 | 922篇 |
原子能技术 | 500篇 |
自动化技术 | 47803篇 |
出版年
2024年 | 689篇 |
2023年 | 1701篇 |
2022年 | 3084篇 |
2021年 | 3406篇 |
2020年 | 3775篇 |
2019年 | 3209篇 |
2018年 | 3205篇 |
2017年 | 3773篇 |
2016年 | 4288篇 |
2015年 | 4900篇 |
2014年 | 6410篇 |
2013年 | 6208篇 |
2012年 | 7701篇 |
2011年 | 7922篇 |
2010年 | 6301篇 |
2009年 | 6484篇 |
2008年 | 6723篇 |
2007年 | 7383篇 |
2006年 | 5921篇 |
2005年 | 4949篇 |
2004年 | 4047篇 |
2003年 | 3229篇 |
2002年 | 2493篇 |
2001年 | 1983篇 |
2000年 | 1743篇 |
1999年 | 1355篇 |
1998年 | 1074篇 |
1997年 | 920篇 |
1996年 | 721篇 |
1995年 | 597篇 |
1994年 | 488篇 |
1993年 | 371篇 |
1992年 | 364篇 |
1991年 | 215篇 |
1990年 | 229篇 |
1989年 | 188篇 |
1988年 | 142篇 |
1987年 | 65篇 |
1986年 | 73篇 |
1985年 | 64篇 |
1984年 | 49篇 |
1983年 | 46篇 |
1982年 | 42篇 |
1981年 | 26篇 |
1980年 | 34篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1975年 | 14篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A weighting algorithm to determine the coordinates of the center of a Gaussian laser beam projected onto a matrix photodetector is considered. The influence of the internal noise of the photodetector, the maximum brightness of the signal at the beam maximum, and the beam radius on the precision of the algorithm is investigated. Recommendations on image processing are presented. 相似文献
62.
一种基于混沌的随机数发生器设计及其IC实现 总被引:1,自引:1,他引:0
在密码学、仿真学以及集成电路测试等许多领域 ,随机数起着重要的作用。在密码学中 ,通常要求所使用的随机数具有不可预测性。基于混沌现象 ,使用开关电容技术 ,用集成电路实现了一种硬件随机数发生器。测试结果表明 ,其产生的序列具有不可预测性 ,可以满足密码学的应用要求。 相似文献
63.
Andrzej Ciepielewski 《International journal of parallel programming》1991,20(6):421-451
Implementation of or-parallel Prolog systems offers a number of interesting scheduling problems. The main issues are the interaction between memory models and scheduling, ordering of multiple solutions, and scheduling of speculative work. The problems occur partly because of the design choices (e.g. the choice of a memory model), and partly because of the desire to maintain observational equivalence between parallel and sequential implementations of Prolog, while achieving high efficiency. In the first part of this paper a common framework for discussing scheduling in or-parallel systems is introduced, and also a collection of issues that must be addressed in such systems is presented. In the second part of the paper we survey a number of solutions to these problems comparing their efficiency whenever possible. We close the survey with a short discussion of open problems.Current association: Carlstedt Elektronik AB 相似文献
64.
Memory loss in retrograde amnesia has long been held to be larger for recent periods than for remote periods, a pattern usually referred to as the Ribot gradient. One explanation for this gradient is consolidation of long-term memories. Several computational models of such a process have shown how consolidation can explain characteristics of amnesia, but they have not elucidated how consolidation must be envisaged. Here findings are reviewed that shed light on how consolidation may be implemented in the brain. Moreover, consolidation is contrasted with alternative theories of the Ribot gradient. Consolidation theory, multiple trace theory, and semantization can all handle some findings well but not others. Conclusive evidence for or against consolidation thus remains to be found. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
David Mills 《Granular Matter》2004,6(2-3):173-177
For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem. 相似文献
66.
Due to interference, path loss, multipath fading, background noise, and many other factors, wireless communication normally
cannot provide a wireless link with both a high data rate and a long transmission range. To address this problem, striping
network traffic in parallel over multiple lower-data-rate but longer-transmission-range wireless channels may be used. In
this paper, we propose a new striping method and evaluate its performances over multiple IEEE 802.11(b) channels under various
conditions. Our extensive simulation results show that this method is quite effective for such an application.
S.Y. Wang is an Associate Professor of the Department of Computer Science and Information Engineering at National Chiao Tung University,
Taiwan. He received his Master and Ph.D. degree in computer science from Harvard University in 1997 and 1999, respectively.
His research interests include wireless networks, Internet technologies, network simulations, and operating systems. He is
the author of the NCTUns 2.0 network simulator and emulator, which is being widely used by network and communication researchers.
More information about the tool is available at http://NSL.csie.nctu.edu.tw/nctuns.html.
C.H. Hwang received his master degree in computer science from NCTU in 2002 and currently is working for a network company.
C.L. Chou currently is a third-year Ph.D. student at the Department of Computer Science and Information Engineering, National Chiao
TungUniversity (NCTU), Taiwan. He received his master degree in computer science from NCTU in 2002. 相似文献
67.
68.
To find the exact probability distribution of the global maximum or minimum of a random field within a bounded domain is a pending problem even for Gaussian fields. Except for very special examples of fields, recourse must be taken to approximate reasoning or asymptotic considerations to be judged with respect to accuracy by simulations. In this paper, the problem is addressed through a functional equation that leads to the definition of a class of distribution functions that depend solely on process or field characteristics and domain quantities that can be calculated explicitly. This distribution function class is studied for Gaussian processes in earlier works by the author and it has been obtained explicitly for Gaussian fields on rectangular domains in the plane. Simulation studies show that rather good predictions are obtained for sufficiently smooth wide band Gaussian processes and fields. In this paper, the distribution function is obtained in general for Gaussian fields over arbitrary bounded domains with piecewise continuous and differentiable boundaries, and as in earlier works the distribution function is tested against empirical distribution functions obtained by simulation of sample functions of a smooth approximately Gaussian field, herein called a broken line Hino field. For completeness this particular field type is defined in appendix a and appendix b. The paper concludes with a statistical application on data for plain concrete tensile strength. 相似文献
69.
70.
结构-波浪-海床耦合系统中大圆筒结构的波压力响应 总被引:5,自引:2,他引:3
以沉入式大圆筒结构为对象,通过设计随机波浪水槽实验,测取了在单筒和连续筒两种结构型式、两种沉入深度和两种波谱输入下结构表面的动波压力分布。波面高度以及波压力历程均在领域进行分析。通过计算结构表面沿高程和沿环向的波压力谱及波压力传递函数,将单筒实测结果与基于线性绕射理论的解析解进行了比较,同时也详细对比了两种结构型式下的实测结果。文中汇报了在研究中获得的新发现及进行的相应分析,特别是在结构——波浪——海床动力相互作用下对波压力响应机理以及针对连续筒的研究,可为工程应用提供有价值的参考。 相似文献