全文获取类型
收费全文 | 28623篇 |
免费 | 3405篇 |
国内免费 | 1838篇 |
专业分类
电工技术 | 9484篇 |
技术理论 | 1篇 |
综合类 | 2524篇 |
化学工业 | 1133篇 |
金属工艺 | 732篇 |
机械仪表 | 2972篇 |
建筑科学 | 1173篇 |
矿业工程 | 705篇 |
能源动力 | 840篇 |
轻工业 | 553篇 |
水利工程 | 589篇 |
石油天然气 | 877篇 |
武器工业 | 327篇 |
无线电 | 5490篇 |
一般工业技术 | 1828篇 |
冶金工业 | 460篇 |
原子能技术 | 260篇 |
自动化技术 | 3918篇 |
出版年
2024年 | 129篇 |
2023年 | 369篇 |
2022年 | 659篇 |
2021年 | 875篇 |
2020年 | 999篇 |
2019年 | 759篇 |
2018年 | 732篇 |
2017年 | 967篇 |
2016年 | 1046篇 |
2015年 | 1292篇 |
2014年 | 2045篇 |
2013年 | 1794篇 |
2012年 | 2537篇 |
2011年 | 2573篇 |
2010年 | 1872篇 |
2009年 | 1811篇 |
2008年 | 1697篇 |
2007年 | 1978篇 |
2006年 | 1731篇 |
2005年 | 1433篇 |
2004年 | 1213篇 |
2003年 | 978篇 |
2002年 | 702篇 |
2001年 | 681篇 |
2000年 | 547篇 |
1999年 | 463篇 |
1998年 | 362篇 |
1997年 | 315篇 |
1996年 | 261篇 |
1995年 | 209篇 |
1994年 | 192篇 |
1993年 | 131篇 |
1992年 | 110篇 |
1991年 | 71篇 |
1990年 | 72篇 |
1989年 | 72篇 |
1988年 | 38篇 |
1987年 | 24篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 24篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Yuan Deng Yihai Yang Yuanhang Xiao He-Lou Xie Ruochen Lan Lanying Zhang Huai Yang 《Advanced functional materials》2023,33(35):2301319
Switchable passive radiative cooling (PRC) smart windows can modulate sunlight transmission and spontaneously emit heat to outer space through atmospheric transparent window, presenting great potential in building energy conservation. However, realizing stable and on-demand control of the cooling efficiency for PRC materials is still challenging. Herein, an electro-controlled polymer-dispersed liquid crystal (PDLC) smart window showing PRC property is designed and prepared by adding mid-infrared emitting reactive monomers into the conventional PDLC matrix. It is found that not only the electro-optical properties but also the PRC efficiency of PRC PDLC film are tunable by regulating the content of the mid-infrared emitting components, film thickness, and micromorphology. This advanced PRC PDLC material achieves a near/sub-ambient temperature when the solar irradiance is below 400 W m−2 and can dynamically manage daytime cooling efficiency. Importantly, its PRC efficiency is capable of being tuned in an on-demand and ultrafast millisecond-scale way, whose controllable transparency enables multistage heat regulation. This study is hoped to provide new inspiration in the preparation of advanced optical devices and energy-efficient equipment. 相似文献
32.
In today's Internet routing infrastructure, designers have addressed scaling concerns in routing constrained multiobjective optimization problems examining latency and mobility concerns as a secondary constrain. In tactical Mobile Ad-hoc Network (MANET), hubs can function based on the work plan in various social affairs and the internally connected hubs are almost having the related moving standards where the topology between one and the other are tightly coupled in steady support by considering the touchstone of hubs such as a self-sorted out, self-mending and self-administration. Clustering in the routing process is one of the key aspects to increase MANET performance by coordinating the pathways using multiple criteria and analytics. We present a Group Adaptive Hybrid Routing Algorithm (GAHRA) for gathering portability, which pursues table-driven directing methodology in stable accumulations and on-request steering strategy for versatile situations. Based on this aspect, the research demonstrates an adjustable framework for commuting between the table-driven approach and the on-request approach, with the objectives of enhancing the output of MANET routing computation in each hub. Simulation analysis and replication results reveal that the proposed method is promising than a single well-known existing routing approach and is well-suited for sensitive MANET applications. 相似文献
33.
为满足非接触化、小型化、集成化、数字化、智能化等现代检测技术的发展要求,从成本、工作原理、灵敏度等方面综合考虑,现采用以光电定位模块为核心的光电定位技术,以无线传感器网络作为数据传输与管理的技术手段,构建了无线光电定位网络,并进行了实验分析.可实现多点实时监测、异地显示测量数据、数据网络化管理等特殊需求;涵盖了多学科领... 相似文献
34.
35.
Distributed uplink scheduling in OFDMA systems is considered. In the proposed model, mobile terminals have the responsibility of making their own transmission decisions. The proposed scheme is based on two dimensional reservation in time and frequency. Terminals use channel state information in order to favor transmissions over certain subchannels, and transmission is done in a probabilistic manner. The proposed approach provides more autonomy to mobile devices in making transmission decisions. Furthermore, it allows avoiding collisions during transmission since it leads to collision detection during the resource reservation phase. The proposed approach is compared to other random access methods and shown to be superior in terms of increasing sum-rate, reducing the number of users in outage, and reducing the collision probability in the reservation phase. 相似文献
36.
This paper deals with the stability radii of implicit dynamic equations on time scales when the structured perturbations act on both the coefficient of derivative and the right-hand side. Formulas of the stability radii are derived as a unification and generalization of some previous results. A special case where the real stability radius and the complex stability radius are equal is studied. Examples are derived to illustrate results. 相似文献
37.
J. Huston McCulloch 《Computational Economics》2000,16(1-2):47-62
A method of estimating the spectral representation of a generalized bivariatestable distribution is presented, based on a series of maximum likelihood (ML)estimates of the stable parameters of univariate projections of the data. Thecorresponding stable spectral density is obtained by solving a quadraticprogram. The proposed method avoids the often arduous task of computing themultivariate stable density, relying instead on the standard univariate stabledensity. The paper applies this projection procedure, under the simplifyingassumption of symmetry, to simulated data as well as to foreign exchangereturn data, with favorable results. Kanter projection coefficients governingconditional expectations are computed from the estimated spectral density. For the simulated data these compare well to their known true values. 相似文献
38.
分析了自行车的连续圆周运动不能使脚蹬力均匀变化的特性,对传统自行车的传动机构中存在的问题进行了改进。本文基于人机工程学原理用椭圆链轮代替主动圆链轮作为自行车的不等速传动装置,对该传动机构进行了优化,克服了自行车传动过程中出现的缺点,能最大限度的发挥人体结构的用力功能,从而推广了自行车的新应用。 相似文献
39.
40.