全文获取类型
收费全文 | 17732篇 |
免费 | 1853篇 |
国内免费 | 2360篇 |
专业分类
电工技术 | 288篇 |
技术理论 | 2篇 |
综合类 | 827篇 |
化学工业 | 1612篇 |
金属工艺 | 3113篇 |
机械仪表 | 1217篇 |
建筑科学 | 498篇 |
矿业工程 | 1599篇 |
能源动力 | 507篇 |
轻工业 | 65篇 |
水利工程 | 47篇 |
石油天然气 | 87篇 |
武器工业 | 67篇 |
无线电 | 758篇 |
一般工业技术 | 2618篇 |
冶金工业 | 3719篇 |
原子能技术 | 45篇 |
自动化技术 | 4876篇 |
出版年
2024年 | 91篇 |
2023年 | 545篇 |
2022年 | 773篇 |
2021年 | 789篇 |
2020年 | 828篇 |
2019年 | 829篇 |
2018年 | 766篇 |
2017年 | 788篇 |
2016年 | 895篇 |
2015年 | 791篇 |
2014年 | 1103篇 |
2013年 | 1341篇 |
2012年 | 1563篇 |
2011年 | 1474篇 |
2010年 | 1141篇 |
2009年 | 1433篇 |
2008年 | 871篇 |
2007年 | 1158篇 |
2006年 | 1036篇 |
2005年 | 454篇 |
2004年 | 277篇 |
2003年 | 240篇 |
2002年 | 248篇 |
2001年 | 213篇 |
2000年 | 277篇 |
1999年 | 320篇 |
1998年 | 295篇 |
1997年 | 233篇 |
1996年 | 224篇 |
1995年 | 184篇 |
1994年 | 135篇 |
1993年 | 67篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 41篇 |
1989年 | 23篇 |
1988年 | 70篇 |
1987年 | 105篇 |
1986年 | 87篇 |
1985年 | 31篇 |
1984年 | 34篇 |
1983年 | 15篇 |
1982年 | 6篇 |
1980年 | 11篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
针对已有的3D实体真实性认证方法中实体的标识不与实体自身绑定且难以验证的问题,提出了一种面向3D实体的签名算法。给出了3D实体签名算法的设计思想、签名产生算法以及签名验证算法。在粗配准和精匹配阶段分别通过自旋图(Spin Image)和ICP(Iterative Closest Point)算法对签名表面和待测表面进行匹配,从而提高了验证的准确率。对所设计的签名算法进行了实验仿真,所获得的迭代误差和匹配率表明该算法可以区分原始和伪造的签名表面,进而证明了算法的有效性。 相似文献
182.
目前在大多数多代理多签名(multi-proxy multi-signature,MPMS)方案中,所有的原始签名人指定同一个代理群生成代理签名。然而在很多实际应用中,每个原始签名人经常需要在自己所在的组织中选择代理群,从而导致各个原始签名人需要选择不同的代理群,代表自己生成代理签名。现有的多代理多签名方案中还没有考虑这方面的需求。提出一个可以指定不同代理群的MPMS方案。在该方案中,可以指定一个多人的验证群合作验证最终签名的合法性。为证明方案的安全性,对现有的安全模型进行改进,在计算Diffie-Hellman假设的基础上,验证所提方案是安全的。与已有方案相比,本方案更加安全和有效。 相似文献
183.
This paper is concerned with the quantized output feedback stabilization problem for a class of uncertain systems with nonsmooth nonlinearities in the actuator device via sliding mode control schemes. It is assumed that system signals are quantized before being transmitted through communication channels. First, a dynamical compensator is developed to estimate unmeasurable system state. Then a sliding surface, in the augmented space using the system output and the estimated state, is proposed, and an adaptive sliding mode control scheme with a static adjustment law of the quantization parameter is established. It is shown that the proposed quantized feedback control strategy is able to tackle parameter uncertainty, external disturbances, and nonsymmetric input nonlinearity simultaneously and guarantees the reachability of the sliding modes of the uncertain system. Finally, an example is given to verify the validity of the theoretical results. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
184.
This paper is concerned with the problem of the fault detection filter design for discrete‐time switched linear systems with average dwell‐time. The designed fault detection filters are also switched systems, which are assumed to be asynchronously switched with the original switched systems. Improved results on the weighted l2 performance and the H ? performance are first given, and the multiple Lyaounov‐like functions during matched period and unmatched period for the running time of one subsystem are used. By the aid of multiple Lyapunov‐like functions combined with Projection Lemma, the FD filters are designed such that the augmented systems under asynchronous switching are exponentially stable, and the residual signal generated by the filters achieves the weighted l2‐gain for disturbances and guarantees the H ? performance for faults. Sufficient conditions are formulated by linear matrix inequalities, and the filter gains are characterized in terms of the solution of a convex optimization problem. Finally, examples are provided to demonstrate the effectiveness of the proposed design method. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
185.
In this paper, a generalized robust H ∞ filtering method is proposed for a class of singular Markovian jump systems, whose generality is mainly embodied that the desired filter could bear perturbances in terms of uncertainties on its parameter matrices. Firstly, an LMI condition of robust mode‐dependent filter is developed. Based on the given result, a new approach to mode‐independent H ∞ filter is presented, which establishes a direct connection between mode‐dependent and mode‐independent filters. Secondly, when the transition rate matrix is with elementwise bounded uncertainties or partially unknown, sufficient conditions of such robust mode‐dependent and mode‐independent filters are all developed within LMI frameworks. Finally, a numerical example is used to demonstrate the effectiveness of the proposed methods. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
186.
187.
Charge transfer complexes possessing a … DADA … structure with both the donor, D, and acceptor, A, being S = 1/2 radicals may exhibit cooperative magnetic phenomena. The complex [Fe(C5Me5)2]+·[TCNQ]−· exhibits metamagnetic behavior. The similarly structured [TCNE]−· and [C4(CN)6]−· complexes are ferromagnets, whereas the [DDQ]−· salt is a paramagnet. The high temperature magnetic susceptibility obeys the Curie-Weiss expression with θ = + 30, + 30, and + 3 for the [TCNE]−·, [C4(CN)6]−·, and [TCNQ]−· salts, respectively. The ferromagnetic [TCNE]−· salt exhibits zero field Zeeman split 57Fe Mossbauer spectra with an internal field of 425.6 kOe at 4.23 K. After reviewing the current papers discussing ferromagnetism in molecular (organic) compounds, a qualitative model consistent with the necessary bulk spin alignment required for a ferromagnet is presented. 相似文献
188.
《Inorganic chemistry communications》2007,10(4):467-470
The complex [Cd2(phen)4(p-phth)(H2O)2](p-phth) · 10H2O (1) has been synthesized by the reaction Cd(NO3)2 with phen and p-phth (where phen = 1,10-phenanthroline, p-phth = p-phthalic acid) in a solution of ethanol and distilled water. The crystal structure was characterized by X-ray single-crystal diffraction and infrared spectrum. In 1, a novel 2D supramolecular structure was formed, containing water octamer and tetramer. 相似文献
189.
新型气田水质防垢剂的合成研究 总被引:1,自引:0,他引:1
针对四川地区天然气气田水矿化度高、温度高、水型多、结垢严重的特点,将醋酸乙烯酯和马来酸酐进行自由基共聚,研究了试验条件对合成聚合物型防垢剂性能的影响规律,并运用正交试验原理,研究出合成聚合物型防垢剂的最佳试验条件;通过性能评价,该防垢剂对四川地区各种气田水均有很好的防垢作用。 相似文献
190.
针对无线传感器网络中DV-Hop定位算法在未知节点到锚节点距离计算中的不足,提出了一种新的距离计算方法。该算法考虑了未知节点到锚节点路径中相邻三个节点组成的夹角对距离的影响,从而更精确计算出距离,并对改进算法和原算法进行了对比仿真。仿真结果表明,改进算法有效地提高了节点的定位精度和覆盖率. 相似文献