全文获取类型
收费全文 | 144136篇 |
免费 | 15496篇 |
国内免费 | 8921篇 |
专业分类
电工技术 | 11329篇 |
技术理论 | 4篇 |
综合类 | 12862篇 |
化学工业 | 19152篇 |
金属工艺 | 9069篇 |
机械仪表 | 9383篇 |
建筑科学 | 10094篇 |
矿业工程 | 5420篇 |
能源动力 | 4109篇 |
轻工业 | 13917篇 |
水利工程 | 4132篇 |
石油天然气 | 5700篇 |
武器工业 | 2088篇 |
无线电 | 13897篇 |
一般工业技术 | 13042篇 |
冶金工业 | 13404篇 |
原子能技术 | 2199篇 |
自动化技术 | 18752篇 |
出版年
2024年 | 464篇 |
2023年 | 2357篇 |
2022年 | 5032篇 |
2021年 | 6697篇 |
2020年 | 4896篇 |
2019年 | 3658篇 |
2018年 | 4064篇 |
2017年 | 4319篇 |
2016年 | 4047篇 |
2015年 | 6123篇 |
2014年 | 7646篇 |
2013年 | 9036篇 |
2012年 | 11073篇 |
2011年 | 11498篇 |
2010年 | 10687篇 |
2009年 | 9936篇 |
2008年 | 9866篇 |
2007年 | 9482篇 |
2006年 | 8387篇 |
2005年 | 6677篇 |
2004年 | 4963篇 |
2003年 | 3774篇 |
2002年 | 3603篇 |
2001年 | 3251篇 |
2000年 | 2622篇 |
1999年 | 1892篇 |
1998年 | 3505篇 |
1997年 | 2180篇 |
1996年 | 1576篇 |
1995年 | 1094篇 |
1994年 | 854篇 |
1993年 | 851篇 |
1992年 | 353篇 |
1991年 | 289篇 |
1990年 | 253篇 |
1989年 | 199篇 |
1988年 | 191篇 |
1987年 | 125篇 |
1986年 | 132篇 |
1985年 | 79篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 52篇 |
1981年 | 48篇 |
1980年 | 78篇 |
1979年 | 26篇 |
1977年 | 165篇 |
1976年 | 286篇 |
1959年 | 36篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 274 毫秒
991.
We propose a novel fault detection and localization scheme for all-optical networks with the information of real-time data
traffic. Our adaptive fault localization framework is based on combining passive and proactive monitoring solutions, together
with adaptive management in two phases. Numerical results indicate that our proposed scheme has good scalability, in terms
of the number of fault monitors required. Also, we show that our framework allows more flexible network design, and requires
much less monitoring bandwidth when compared with the passive monitoring solutions. 相似文献
992.
Xu Y Xu D Lin S Han TX Cao X Li X 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2012,42(3):729-739
In this paper, we study the problem of detecting sudden pedestrian crossings to assist drivers in avoiding accidents. This application has two major requirements: to detect crossing pedestrians as early as possible just as they enter the view of the car-mounted camera and to maintain a false alarm rate as low as possible for practical purposes. Although many current sliding-window-based approaches using various features and classification algorithms have been proposed for image-/video-based pedestrian detection, their performance in terms of accuracy and processing speed falls far short of practical application requirements. To address this problem, we propose a three-level coarse-to-fine video-based framework that detects partially visible pedestrians just as they enter the camera view, with low false alarm rate and high speed. The framework is tested on a new collection of high-resolution videos captured from a moving vehicle and yields a performance better than that of state-of-the-art pedestrian detection while running at a frame rate of 55 fps. 相似文献
993.
Range-free localization methods are suitable for large scale wireless ad hoc and sensor networks due to their less-demanding hardware requirements. Many existing connectivity- or hop-count-based range-free localization methods suffer from the hop-distance ambiguity problem where a node has a same distance estimation to all of its one-hop neighbors. In this paper, we define a new measure, called regulated neighborhood distance (RND), to address this problem by relating the proximity of two neighbors to their neighbor partitions. Furthermore, we propose a new RND-based range-free localization method, and compare our localization algorithm with peer classical algorithms in different network scenarios, which include grid deployment, random uniform deployment, non-uniform deployment and uniform deployment with a coverage hole. Simulation results show that ours can achieve better and reliable localization accuracy in these network scenarios. 相似文献
994.
Jianwei Zhao Dong Sun Park Joonwhoan Lee Feilong Cao 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(9):1503-1514
Functional data learning is an extension of traditional data learning, that is, learning the data chosen from the Euclidean space ${\mathbb{R}^{n}}$ to a metric space. This paper focuses on the functional data learning with generalized single-hidden layer feedforward neural networks (GSLFNs) acting on some metric spaces. In addition, three learning algorithms, named Hilbert parallel overrelaxation backpropagation (H-PORBP) algorithm, ν-generalized support vector regression (ν-GSVR) and generalized extreme learning machine (G-ELM) are proposed to train the GSLFNs acting on some metric spaces. The experimental results on some metric spaces indicate that GELM with additive/RBF hidden-nodes has a faster learning speed, a better accuracy, and a better stability than HPORBP algorithm and ν-GSVR for training the functional data. The idea of GELM can be used to extend those improved extreme learning machines (ELMs) that act on the Euclidean space ${\mathbb{R}^{n}, }$ such as online sequential ELM, incremental ELM, pruning ELM and so on, to some metric spaces. 相似文献
995.
Dong?Seop?LeeEmail author J.?Periaux L.?F.?Gonzalez K.?Srinivas E.?Onate 《Structural and Multidisciplinary Optimization》2012,45(3):433-450
There are many applications in aeronautical/aerospace engineering where some values of the design parameters/states cannot
be provided or determined accurately. These values can be related to the geometry (wingspan, length, angles) and or to operational
flight conditions that vary due to the presence of uncertainty parameters (Mach, angle of attack, air density and temperature,
etc.). These uncertainty design parameters cannot be ignored in engineering design and must be taken into the optimisation
task to produce more realistic and reliable solutions. In this paper, a robust/uncertainty design method with statistical
constraints is introduced to produce a set of reliable solutions which have high performance and low sensitivity. Robust design
concept coupled with Multi-Objective Evolutionary Algorithms (MOEAs) is defined by applying two statistical sampling formulas;
mean and variance/standard deviation associated with the optimisation fitness/objective functions. The methodology is based
on a canonical evolution strategy and incorporates the concepts of hierarchical topology, parallel computing and asynchronous
evaluation. It is implemented for two practical Unmanned Aerial System (UAS) design problems; the first case considers robust
multi-objective (single-disciplinary: aerodynamics) design optimisation and the second considers a robust multidisciplinary
(aero-structures) design optimisation. Numerical results show that the solutions obtained by the robust design method with
statistical constraints have a more reliable performance and sensitivity in both aerodynamics and structures when compared
to the baseline design. 相似文献
996.
Qiyong Han Xiaodong Zhang Dong Chen Pengfei Wang 《Metallurgical and Materials Transactions B》1988,19(4):617-622
The equilibrium Ca3P2(s) = 3[Ca] + 2[P] was studied at 1600 ° by equilibrating liquid iron, saturated with Ca3P2, and contained in a TiN crucible, with Ca vapor. The source of Ca was liquid Ca contained in an Mo crucible, and the vapor
pressure of Ca was varied by varying the position of the Mo crucible in the temperature gradient of a vertical tube furnace.
A least-squares analysis of the data gave and. The simultaneous equilibria CaO(s) = [Ca] + [O] and CaS(s) = [Ca] + [S] were studied at 1600 ° by equilibrating liquid iron, contained in a pressed and sintered CaO-CaS crucible with
Ca vapor. The advantage of this technique is that two equilibrium constants,K
cas andK
cao, and two interaction coefficients, and can be determined from one set of experiments. It was determined that, at 1600 °,K
cas = 5.9 × 10−8
K
cao = 5.5 × 10−9,, and.
Formerly Graduate Students 相似文献
997.
998.
999.
1000.
针对当前高校面临的就业问题,本文利用决策树C4.5算法对某高校近三年的毕业生就业信息进行分析,建立就业分析预测模型。首先选取高校就业信息管理系统中的就业信息,对信息进行采集和预处理,然后利用分类算法中的C4.5分类算法进行挖掘,最后对建立的决策树进行规则提取,从而得到毕业生就业预测规则。实验结果表明建立的就业分析模型是有效的、可靠的,对于全面提高大学生的就业能力、完善就业服务体系等方面具有一定指导意义。 相似文献