全文获取类型
收费全文 | 2101篇 |
免费 | 206篇 |
国内免费 | 106篇 |
专业分类
电工技术 | 67篇 |
综合类 | 131篇 |
化学工业 | 313篇 |
金属工艺 | 19篇 |
机械仪表 | 94篇 |
建筑科学 | 117篇 |
矿业工程 | 18篇 |
能源动力 | 163篇 |
轻工业 | 11篇 |
水利工程 | 239篇 |
石油天然气 | 26篇 |
武器工业 | 5篇 |
无线电 | 174篇 |
一般工业技术 | 291篇 |
冶金工业 | 41篇 |
原子能技术 | 27篇 |
自动化技术 | 677篇 |
出版年
2024年 | 4篇 |
2023年 | 33篇 |
2022年 | 29篇 |
2021年 | 39篇 |
2020年 | 45篇 |
2019年 | 51篇 |
2018年 | 49篇 |
2017年 | 63篇 |
2016年 | 57篇 |
2015年 | 53篇 |
2014年 | 87篇 |
2013年 | 124篇 |
2012年 | 121篇 |
2011年 | 177篇 |
2010年 | 116篇 |
2009年 | 139篇 |
2008年 | 152篇 |
2007年 | 126篇 |
2006年 | 150篇 |
2005年 | 128篇 |
2004年 | 121篇 |
2003年 | 90篇 |
2002年 | 81篇 |
2001年 | 52篇 |
2000年 | 47篇 |
1999年 | 37篇 |
1998年 | 34篇 |
1997年 | 29篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有2413条查询结果,搜索用时 15 毫秒
51.
One of the key functions of Workload Control is order release. Jobs are not released immediately onto the shop floor – they are withheld and selectively released to create a mix of jobs that keeps work-in-process within limits and meet due dates. A recent implementation of Workload Control’s release method highlighted an important issue thus far overlooked by research: How to accommodate re-entrant flows, whereby a station is visited multiple times by the same job? We present the first study to compare the performance of Workload Control both with and without re-entrant flows. Simulation results from a job shop model highlight two important aspects: (i) re-entrant flows increase variability in the work arriving at a station, leading to a direct detrimental effect on performance; (ii) re-entrant flows affect the release decision-making process since the load contribution of all visits by a job to a station has to fit within the norm. Both aspects have implications for practice and our interpretation of previous research since: (i) parameters given for work arriving may significantly differ from those realised; (ii) increased workload contributions at release mean that prior simulations may have been unstable, leading to some jobs never being released. 相似文献
52.
In this paper, a finite-difference based ENO (essentially nonoscillatory) procedure has been chosen for the direct numerical simulation (DNS) of compressible turbulence. The implementation of the ENO scheme follows the relatively efficient procedure in Shuet al. (1992), but the latter has been modified in the present paper to admit scalar conservation equations and to run on the iPSC/860 Paragon parallel supercomputer. DNS results with our procedure are in excellent agreement with pseudo-spectral and Padé approximation calculations in two and three dimensions. This is the case for a variety of initial conditions for compressible turbulence. The parallel algorithms presented are simple but quite efficient for DNS, with a speedup that approaches the theoretical value. Some of the attractive features include 1) minimum communication whereby a processor only communicates with two neighbors, 2) almost one hundred percent load balancing, 3) a checker-board approach to solve the Poisson equation reduces communication by a factor of approximately 2, and, 4) obtaining turbulence statistics is based on a global collect approach, which is implemented to ensure that a single number, rather than a large matrix of numbers, is communicated between processors. The ENO code presented in this paper should be quite useful in its own right, while the parallel implementation should allow the simulation of fairly realistic problems. 相似文献
53.
Based on the computational Diffie-Hellman problem, this paper proposes an identity-based authenticated key agreement protocol which removes bilinear pairings. Compared with previous protocols, the new protocol minimizes message exchange time with no extra cost. The protocol provides strong security guarantees including key compromise impersonation resilience, perfect forward secrecy, and master key forward secrecy. A security proof with the modular approach in the modified Bellare-Rogaway model is also provided. 相似文献
54.
提出一个应用椭圆曲线密码体制进行密钥协商而在基于身份的公钥密码系统内进行组通信的全新安全组播方案,分析子组成员的密钥协商和子组间的通信过程,以及组成员动态变化时密钥的更新过程。结果表明,该方案在降低计算和通信代价方面可取得较好的效果,且满足密钥协商的安全要求。 相似文献
55.
Morteza Nikooghadam Author VitaeAuthor Vitae Mohsen Ebrahimi Moghaddam Author Vitae 《Journal of Systems and Software》2010,83(10):1917-1929
The elliptic curve cryptosystem (ECC) has recently received significant attention by researchers due to its high performance, low computational cost, and small key size. In this paper, an efficient key management and derivation scheme based on ECC is proposed to solve dynamic access problems in a user hierarchy. Compared to previous ECC based works, the proposed method does not require constructing interpolate polynomials, therefore, the computational complexity of key generation and key derivation is significantly reduced. At the same time, time complexity of adding/deleting security classes, modifying their relationships, and changing of secret keys is decreased in the proposed method. 相似文献
56.
57.
58.
设计了一种新的具备消息恢复特性的指定验证者的代理盲签名方案.方案的安全性建立在椭圆曲线离散对数难解性之上,并对其进行了安全性分析.方案在验证签名过程中,消息可恢复出来.另外,方案节省了信息的传输量,有效地降低成本,有广泛的应用价值. 相似文献
59.
标量乘法的效率决定着椭圆曲线密码体制的性能,而JSF算法是当前最流行的计算椭圆曲线双标量乘的算法;Koblitz曲线上的快速标量乘算法是标量乘法研究的重要课题。Lee[12]算法采用Frobenius映射扩展正整数k并将其扩展后的系数改写成二进制形式有效地提高标量乘算法效率。将JSF应用到扩展后的系数中,以较小存储空间为代价来提高算法效率,并将算法运用到改进的ECDSA算法中,减少乘法运算次数,加速签名及验证过程,节约数字签名时间。 相似文献
60.
郝立峰 《计算机应用与软件》2011,(9)
针对嵌入式系统中信息安全的特点,选择椭圆曲线公钥密码体制ECC(Elliptic Curves Cryptosystem)作为加解密系统体制,应用开源安全软件开发包OpenSSL作为密码库开发了加解密系统。详细介绍了椭圆曲线密码体制的两种常用算法:EC-ELGamal与Menezes-Vanstone,在arm-linux平台上开发了完整的上述两种算法的加解密系统,在实际应用中对比、分析了两种算法的优缺点。分析表明:EC-ELGamal与Menezes-Vanstone两种椭圆曲线密码体制算法分别有其适合应用的领域。实践证明:OpenSSL在arm-linux和其他类型的嵌入式平台加密系统的设计方面有很大的易用性、通用性。 相似文献