全文获取类型
收费全文 | 204028篇 |
免费 | 21238篇 |
国内免费 | 13219篇 |
专业分类
电工技术 | 15481篇 |
技术理论 | 3篇 |
综合类 | 23500篇 |
化学工业 | 25469篇 |
金属工艺 | 10718篇 |
机械仪表 | 15017篇 |
建筑科学 | 22176篇 |
矿业工程 | 9006篇 |
能源动力 | 6839篇 |
轻工业 | 12371篇 |
水利工程 | 7847篇 |
石油天然气 | 9156篇 |
武器工业 | 2752篇 |
无线电 | 17772篇 |
一般工业技术 | 25638篇 |
冶金工业 | 9116篇 |
原子能技术 | 3512篇 |
自动化技术 | 22112篇 |
出版年
2024年 | 827篇 |
2023年 | 2570篇 |
2022年 | 4849篇 |
2021年 | 5701篇 |
2020年 | 6520篇 |
2019年 | 5638篇 |
2018年 | 5460篇 |
2017年 | 6937篇 |
2016年 | 7625篇 |
2015年 | 7918篇 |
2014年 | 12425篇 |
2013年 | 12225篇 |
2012年 | 15537篇 |
2011年 | 15646篇 |
2010年 | 11989篇 |
2009年 | 12262篇 |
2008年 | 11392篇 |
2007年 | 14079篇 |
2006年 | 12401篇 |
2005年 | 10556篇 |
2004年 | 8790篇 |
2003年 | 7667篇 |
2002年 | 6399篇 |
2001年 | 5447篇 |
2000年 | 4738篇 |
1999年 | 4023篇 |
1998年 | 3243篇 |
1997年 | 2814篇 |
1996年 | 2411篇 |
1995年 | 2108篇 |
1994年 | 1787篇 |
1993年 | 1327篇 |
1992年 | 1162篇 |
1991年 | 859篇 |
1990年 | 706篇 |
1989年 | 637篇 |
1988年 | 480篇 |
1987年 | 272篇 |
1986年 | 227篇 |
1985年 | 145篇 |
1984年 | 128篇 |
1983年 | 81篇 |
1982年 | 78篇 |
1981年 | 77篇 |
1980年 | 52篇 |
1979年 | 49篇 |
1978年 | 23篇 |
1976年 | 17篇 |
1975年 | 26篇 |
1959年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
62.
For rechargeable wireless sensor networks, limited energy storage capacity, dynamic energy supply, low and dynamic duty cycles cause that it is unpractical to maintain a fixed routing path for packets delivery permanently from a source to destination in a distributed scenario. Therefore, before data delivery, a sensor has to update its waking schedule continuously and share them to its neighbors, which lead to high energy expenditure for reestablishing path links frequently and low efficiency of energy utilization for collecting packets. In this work, we propose the maximum data generation rate routing protocol based on data flow controlling technology. For a sensor, it does not share its waking schedule to its neighbors and cache any waking schedules of other sensors. Hence, the energy consumption for time synchronization, location information and waking schedule shared will be reduced significantly. The saving energy can be used for improving data collection rate. Simulation shows our scheme is efficient to improve packets generation rate in rechargeable wireless sensor networks. 相似文献
63.
64.
65.
Fatemeh Abdi 《Optimization methods & software》2019,34(1):25-36
In this paper, we propose a globally convergent BFGS method to solve Variational Inequality Problems (VIPs). In fact, a globalization technique on the basis of the hyperplane projection method is applied to the BFGS method. The technique, which is independent of any merit function, is applicable for pseudo-monotone problems. The proposed method applies the BFGS direction and tries to reduce the distance of iterates to the solution set. This property, called Fejer monotonicity of iterates with respect to the solution set, is the basis of the convergence analysis. The method applied to pseudo-monotone VIP is globally convergent in the sense that subproblems always have unique solutions, and the sequence of iterates converges to a solution to the problem without any regularity assumption. Finally, some numerical simulations are included to evaluate the efficiency of the proposed algorithm. 相似文献
66.
67.
The rate of penetration (ROP) model is of great importance in achieving a high efficiency in the complex geological drilling process. In this paper, a novel two-level intelligent modeling method is proposed for the ROP considering the drilling characteristics of data incompleteness, couplings, and strong nonlinearities. Firstly, a piecewise cubic Hermite interpolation method is introduced to complete the lost drilling data. Then, a formation drillability (FD) fusion submodel is established by using Nadaboost extreme learning machine (Nadaboost-ELM) algorithm, and the mutual information method is used to obtain the parameters, strongly correlated with the ROP. Finally, a ROP submodel is established by a neural network with radial basis function optimized by the improved particle swarm optimization (RBFNN-IPSO). This two-level ROP model is applied to a real drilling process and the proposed method shows the best performance in ROP prediction as compared with conventional methods. The proposed ROP model provides the basis for intelligent optimization and control in the complex geological drilling process. 相似文献
68.
《工程(英文)》2019,5(4):637-645
The rapid development of information and communication technologies (ICTs) and cyber–physical systems (CPSs) has paved the way for the increasing popularity of smart products. Context-awareness is an important facet of product smartness. Unlike artifacts, various bio-systems are naturally characterized by their extraordinary context-awareness. Biologically inspired design (BID) is one of the most commonly employed design strategies. However, few studies have examined the BID of context-aware smart products to date. This paper presents a structured design framework to support the BID of context-aware smart products. The meaning of context-awareness is defined from the perspective of product design. The framework is developed based on the theoretical foundations of the situated function–behavior–structure ontology. A structured design process is prescribed to leverage various biological inspirations in order to support different conceptual design activities, such as problem formulation, structure reformulation, behavior reformulation, and function reformulation. Some existing design methods and emerging design tools are incorporated into the framework. A case study is presented to showcase how this framework can be followed to redesign a robot vacuum cleaner and make it more context-aware. 相似文献
69.
This paper considers the state‐dependent interference relay channel (SIRC) in which one of the two users may operate as a secondary user and the relay has a noncausal access to the signals from both users. For discrete memoryless SIRC, we first establish the achievable rate region by carefully merging Han‐Kobayashi rate splitting encoding technique, superposition encoding, and Gelfand‐Pinsker encoding technique. Then, based on the achievable rate region that we derive, the capacity of the SIRC is established in many different scenarios including (a) the weak interference regime, (b) the strong interference regime, and (c) the very strong interference regime. This means that our capacity results contain all available known results in the literature. Next, the achievable rate region and the associated capacity results are also evaluated in the case of additive Gaussian noise. Additionally, many numerical examples are investigated to show the value of our theoretical derivations. 相似文献
70.
This paper considers thermochemical recuperation (TCR) of waste-heat using natural gas reforming by steam and combustion products. Combustion products contain steam (H2O), carbon dioxide (CO2), and ballast nitrogen (N2). Because endothermic chemical reactions take place, methane steam-dry reforming creates new synthetic fuel that contains valuable combustion components: hydrogen (H2), carbon monoxide (CO), and unreformed methane (CH4). There are several advantages to performing TCR in the industrial furnaces: high energy efficiency, high regeneration rate (rate of waste-heat recovery), and low emission of greenhouse gases (CO2, NOx). As will be shown, the use of TCR is significantly increasing the efficiency of industrial furnaces – it has been observed that TCR is capable of reducing fuel consumption by nearly 25%. Additionally, increased energy efficiency has a beneficial effect on the environment as it leads to a reduction in greenhouse gas emissions. 相似文献