全文获取类型
收费全文 | 56345篇 |
免费 | 5471篇 |
国内免费 | 3656篇 |
专业分类
电工技术 | 3146篇 |
技术理论 | 8篇 |
综合类 | 6660篇 |
化学工业 | 5882篇 |
金属工艺 | 2811篇 |
机械仪表 | 3390篇 |
建筑科学 | 4827篇 |
矿业工程 | 1953篇 |
能源动力 | 1969篇 |
轻工业 | 1262篇 |
水利工程 | 1171篇 |
石油天然气 | 1538篇 |
武器工业 | 808篇 |
无线电 | 6938篇 |
一般工业技术 | 9811篇 |
冶金工业 | 3164篇 |
原子能技术 | 446篇 |
自动化技术 | 9688篇 |
出版年
2024年 | 196篇 |
2023年 | 835篇 |
2022年 | 1035篇 |
2021年 | 1364篇 |
2020年 | 1636篇 |
2019年 | 1445篇 |
2018年 | 1579篇 |
2017年 | 1859篇 |
2016年 | 2005篇 |
2015年 | 2041篇 |
2014年 | 3150篇 |
2013年 | 3826篇 |
2012年 | 3715篇 |
2011年 | 4178篇 |
2010年 | 3193篇 |
2009年 | 3368篇 |
2008年 | 3436篇 |
2007年 | 3747篇 |
2006年 | 3533篇 |
2005年 | 3007篇 |
2004年 | 2427篇 |
2003年 | 2099篇 |
2002年 | 1867篇 |
2001年 | 1558篇 |
2000年 | 1366篇 |
1999年 | 1109篇 |
1998年 | 920篇 |
1997年 | 753篇 |
1996年 | 625篇 |
1995年 | 609篇 |
1994年 | 490篇 |
1993年 | 415篇 |
1992年 | 355篇 |
1991年 | 263篇 |
1990年 | 211篇 |
1989年 | 205篇 |
1988年 | 165篇 |
1987年 | 86篇 |
1986年 | 102篇 |
1985年 | 78篇 |
1984年 | 76篇 |
1983年 | 53篇 |
1982年 | 57篇 |
1981年 | 49篇 |
1980年 | 34篇 |
1979年 | 37篇 |
1978年 | 34篇 |
1977年 | 27篇 |
1964年 | 26篇 |
1955年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
YIN YunFei GONG GuangHong & HAN Liang College of Computer Science Chongqing University Chongqing China School of Automation Science Electrical Engineering Beijing University of Aeronautics Astronautics Beijing 《中国科学:信息科学(英文版)》2011,(4)
For the large quantity of data,rules and models generated in the course of computer generated forces (CGFs) behavior modeling,the common analytical methods are statistical methods based on the tactical rules,tactical doctrine and empirical knowledge.However,from the viewpoint of data mining,we can find many of these analytical methods are also each-and-every different data mining methods.In this paper,we survey the data mining theory and techniques that have appeared in the course of CGF behavior modeling f... 相似文献
82.
The spectral properties of the incidence matrix of the communication graph are exploited to provide solutions to two multi-agent control problems. In particular, we consider the problem of state agreement with quantized communication and the problem of distance-based formation control. In both cases, stabilizing control laws are provided when the communication graph is a tree. It is shown how the relation between tree graphs and the null space of the corresponding incidence matrix encode fundamental properties for these two multi-agent control problems. 相似文献
83.
Jung Hyeon Bae Gun Hee Kim Woong Hee Jeong Hyun Jae Kim 《Journal of the Society for Information Display》2011,19(5):404-409
Abstract— Non‐volatile memory effects of an all‐solution‐processed oxide thin‐film transistor (TFT) with ZnO nanoparticles (NPs) as the charge‐trapping layer are reported. The device was fabricated by using a soluble MgInZnO active channel on a ZrHfOx gate dielectric. ZnO NPs were used as the charge‐trapping site at the gate‐insulator—channel interface, and Al was used for source and drain electrodes. Transfer characteristics of the device showed a large clockwise hysteresis, which can be used to demonstrate its memory function due to electron trapping in the ZnO NP charge‐trapping layer. This memory effect has the potential to be utilized as a memory application on displays and disposable electronics. 相似文献
84.
Circular splicing systems are a formal model of a generative mechanism of circular words, inspired by a recombinant behaviour of circular DNA. Some unanswered questions are related to the computational power of such systems, and finding a characterization of the class of circular languages generated by circular splicing systems is still an open problem. In this paper we solve this problem for monotone complete systems, which are finite circular splicing systems with rules of a simpler form. We show that a circular language L is generated by a monotone complete system if and only if the set Lin(L) of all words corresponding to L is a pure unitary language generated by a set closed under the conjugacy relation. The class of pure unitary languages was introduced by A. Ehrenfeucht, D. Haussler, G. Rozenberg in 1983, as a subclass of the class of context-free languages, together with a characterization of regular pure unitary languages by means of a decidable property. As a direct consequence, we characterize (regular) circular languages generated by monotone complete systems. We can also decide whether the language generated by a monotone complete system is regular. Finally, we point out that monotone complete systems have the same computational power as finite simple systems, an easy type of circular splicing system defined in the literature from the very beginning, when only one rule of a specific type is allowed. From our results on monotone complete systems, it follows that finite simple systems generate a class of languages containing non-regular languages, showing the incorrectness of a longstanding result on simple systems. 相似文献
85.
为了能够在认知无线电网络中有效、准确地检测出授权用户,提出了基于改进的证据理论的合作频谱感知方案设计方法.根据各个次用户对授权用户进行多次本地检测得出的时域DS融合结果,设计并改进融合顺序和融合结构,将多个时域DS融合结果送到融合中心进行空域DS融合,得到最终判决.在此基础上,给出了融合顺序、融合结构的改变对算法性能的... 相似文献
86.
87.
移动自组网中非完全信息节点风险评估 总被引:1,自引:0,他引:1
移动自组网是一种无中心、自组织以及多跳的无线网络,能否有效可靠地对通信节点进行风险评估是保障节点高质量通信的重要因素.当前基于可信度或是信誉的评估方法对评估样本都有特殊的要求,对评估对象提出种种假设,无法辨别间接样本的恶意推荐问题,在实际移动自组网中各个节点尤其是恶意节点对外暴漏的信息往往偏少,样本数量有限,无法明确判断其状态,大部分是非完全信息,从而导致评估结果缺乏客观性与可靠性.文中提出采用灰色系统理论描述通信节点非完全信息状态,根据灰类白化以及灰色聚类思想进行节点风险评估.方案针对自组网络通信需求对节点行为进行多关键属性划分,采用味集群方法收集原始样本,避免恶意推荐;将难以用数值精确刻画的关键属性以白化权函数量化,引入灰聚类的概念和计算方法,将实体的通信风险水平定义为实体关键属性值序列针对各评估灰类的聚类评估值,从而得到该实体通信风险水平的相对参考值.分析与实际计算表明该方法是一种适合移动自组网中非完全信息节点风险评估的有效方法. 相似文献
88.
Geometrically non-linear behavior of structural systems with random material property: An asymptotic spectral stochastic approach 总被引:1,自引:0,他引:1
M. Tootkaboni L. Graham-Brady B.W. Schafer 《Computer Methods in Applied Mechanics and Engineering》2009,198(37-40):3173-3185
An asymptotic spectral stochastic approach is presented for computing the statistics of the equilibrium path in the post-bifurcation regime for structural systems with random material properties. The approach combines numerical implementation of Koiter’s asymptotic theory with a stochastic Galerkin scheme and collocation in stochastic space to quantify uncertainties in the parametric representation of the load–displacement relationship, specifically in the form of uncertain post-buckling slope, post-buckling curvature, and a family of stochastic displacement fields. Using the proposed method, post-buckling response statistics for two plane frames are obtained and shown to be in close agreement with those obtained from Monte Carlo simulation, provided a fine enough spectral representation is used to model the variability in the random dimension. 相似文献
89.
90.
We consider the problem of revenue maximization on multi‐unit auctions where items are distinguished by their relative values; any pair of items has the same ratio of values to all buyers. As is common in the study of revenue maximizing problems, we assume that buyers' valuations are drawn from public known distributions and they have additive valuations for multiple items. Our problem is well motivated by sponsored search auctions, which made money for Google and Yahoo! in practice. In this auction, each advertiser bids an amount bi to compete for ad slots on a web page. The value of each ad slot corresponds to its click‐through‐rate, and each buyer has her own per‐click valuations, which is her private information. Obviously, a strategic bidder may bid an amount that is different with her true valuation to improve her utility. Our goal is to design truthful mechanisms avoiding this misreporting. We develop the optimal (with maximum revenue) truthful auction for a relaxed demand model (where each buyer i wants at most di items) and a sharp demand model (where buyer i wants exactly di items). We also find an auction that always guarantees at least half of the revenue of the optimal auction when the buyers are budget constrained. Moreover, all of the auctions we design can be computed efficiently, that is, in polynomial time. 相似文献