全文获取类型
收费全文 | 71630篇 |
免费 | 6990篇 |
国内免费 | 3262篇 |
专业分类
电工技术 | 4228篇 |
技术理论 | 3篇 |
综合类 | 4556篇 |
化学工业 | 11958篇 |
金属工艺 | 4359篇 |
机械仪表 | 4948篇 |
建筑科学 | 5336篇 |
矿业工程 | 2479篇 |
能源动力 | 1914篇 |
轻工业 | 4525篇 |
水利工程 | 1290篇 |
石油天然气 | 4481篇 |
武器工业 | 627篇 |
无线电 | 8748篇 |
一般工业技术 | 8570篇 |
冶金工业 | 3457篇 |
原子能技术 | 764篇 |
自动化技术 | 9639篇 |
出版年
2024年 | 679篇 |
2023年 | 1354篇 |
2022年 | 2170篇 |
2021年 | 3054篇 |
2020年 | 2328篇 |
2019年 | 2011篇 |
2018年 | 2198篇 |
2017年 | 2415篇 |
2016年 | 2269篇 |
2015年 | 2835篇 |
2014年 | 3436篇 |
2013年 | 4091篇 |
2012年 | 4588篇 |
2011年 | 5024篇 |
2010年 | 4172篇 |
2009年 | 3977篇 |
2008年 | 3805篇 |
2007年 | 3735篇 |
2006年 | 4113篇 |
2005年 | 3371篇 |
2004年 | 2395篇 |
2003年 | 2030篇 |
2002年 | 1763篇 |
2001年 | 1635篇 |
2000年 | 1740篇 |
1999年 | 1889篇 |
1998年 | 1650篇 |
1997年 | 1384篇 |
1996年 | 1253篇 |
1995年 | 1028篇 |
1994年 | 886篇 |
1993年 | 608篇 |
1992年 | 450篇 |
1991年 | 388篇 |
1990年 | 270篇 |
1989年 | 227篇 |
1988年 | 187篇 |
1987年 | 125篇 |
1986年 | 102篇 |
1985年 | 60篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 16篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
TNV电路会通过空气间隙、绝缘表面爬电距离和接触电流等方面对人体和公共信息网路传递危险能量。文章将从传递危险的电能流通渠道来分析TNV电路的设计要求以及相应的解决方法。 相似文献
992.
一种无线数据传输方案及实现 总被引:1,自引:0,他引:1
本文介绍了一种数据信号的无线传输方案,给出了该方案的硬件设计电路框图和软件的主程序流程图.该方案由单片机控制通过无线调制解调芯片与常规UHF、VHF调频电台相连通信,同时与具有标准RS-232接口的计算机数据设备相连,从而实现数据信号的无线传输,由此方案可进一步可组成计算机分组无线网. 相似文献
993.
GPS及其干扰技术研究 总被引:2,自引:0,他引:2
全球定位系统(GPS)在现代导航战中发挥着极为重要的作用,已经成为一种极其重要的导航和制导手段,针对GPS进行的干扰技术也日益成为研究的热点。文中阐述了全球定位系统(GPS)的工作原理,系统组成以及信号格式,并研究和分析了GPS干扰中使用的技术手段和体制,包括侦察引导技术和干扰方法,对它们的特点和干扰性能进行了讨论,并得到了有益的结论. 相似文献
994.
盲均衡技术是一种新兴的均衡技术,不需要发送训练序列就能在接收端恢复出发送序列。本文着重介绍了盲均衡技术的原理及其算法,并对盲均衡技术的新研究进行了展望。盲均衡技术能有效地克服码间干扰,对于提高通信质量具有十分重要的意义。 相似文献
995.
以硝酸锌、氨水为原料,采用低温水浴法在不同的温度下大规模制备了团簇状ZnO纳米棒,采用扫描电子显微镜(SEM)、能谱分析(EDX)、X射线衍射(XRD)、室温光致发光(PL)等手段对ZnO纳米棒进行了表征.SEM结果表明,环境温度对ZnO的形貌和性质有很大的影响,随着温度增加,ZnO长径比越来越大,当温度为90℃时ZnO的平均直径100 nm,长度约为5 μm;EDX和XRD图谱表明,ZnO纳米棒是高纯的六角纤锌矿结构;对90℃条件下制备的ZnO进行光致发光性能测试,观察到波长位于423 nm附近有较强的蓝光发射. 相似文献
996.
WCDMA的MBMS技术 总被引:2,自引:0,他引:2
主要介绍了基于WCDMA的MBMS技术,给出了其网络架构和技术难点,并对其应用给无线网络带来的影响作了一定深度的探讨。 相似文献
997.
998.
Yikun Su Weirui Yu Liming Liao Xinbo Xiong Huanwen Chen Lingzhi Hu Tongjia Lei Jinlai Zhao Dong Chen Wenjie Mai 《Advanced functional materials》2023,33(42):2303976
Photo-electrochemical (PEC) water splitting is a promising method for converting solar energy into clean energy, but the mechanism of improving PEC efficiency through the interfacial contact and defect strategy remains highly controversial. Herein, reduced graphene oxide (rGO) and oxygen vacancies are introduced into α-Fe2O3 nanorod (NR) arrays using a simple spin-coating method and acid treatment. The resultant oxygen vacancy–α-Fe2O3/rGO-integrated system exhibits a higher photocurrent, four times than the pristine α-Fe2O3. It is well evidenced that the electronic interface interaction between α-Fe2O3 and rGO is boosted with the oxygen vacancies, facilitating electron transfer from α-Fe2O3 to rGO. Moreover, the oxygen vacancies not only create interband states in α-Fe2O3 that can trap photogenerated holes and thus facilitate charge separation but significantly also strengthen the adsorption of oxidative intermediates and reduce the energy barrier of rate-determining step during oxygen evolution reaction (OER). This study demonstrates an rGO–oxygen vacancy synergistic interfacial contact and defect modification approach to design semiconducting photocatalysts for high-efficiency solar energy capture and conversion. The generated principle is expected to be extendable to another material system. 相似文献
999.
Yong Long Bing Jiang Tianci Huang Yuxiu Liu Jianan Niu Zhong Lin Wang Weiguo Hu 《Advanced functional materials》2023,33(41):2304625
Due to their intrinsic flexibility, tunable conductivity, multiple stimulus-response, and self-healing ability, ionic conductive hydrogels have drawn significant attention in flexible/wearable electronics. However, challenges remain because traditional hydrogels inevitably faced the problems of losing flexibility and conductivity because of the inner water loss when exposed to the ambient environment. Besides, the water inside the hydrogel will freeze at the water icing temperatures, making the device hard and fragile. As a promising alternative, organogels have attracted wide attention because they can, to some extent, overcome the above drawbacks. Herein, a kind of organogel ionic conductor (MOIC) by a self-polymerization reaction is involved, which is super stretchable, anti-drying, and anti-freezing. Meanwhile, it can still maintain high mechanical stability after alternately loading/unloading at the strain of 600% for 600 s (1800 cycles). Using this MOIC, high-performance triboelectric nanogenerator (TENG) is constructed (MOIC-TENG) to harvest small mechanical energy even the MOIC electrode underwent an extremely low temperature. In addition, multifunctional flexible/wearable sensors (strain sensor, piezoresistive sensor, and tactile sensor) are realized to monitor human motions in real time, and recognize different materials by triboelectric effect. This study demonstrates a promising candidate material for flexible/wearable electronics such as electronic skin, flexible sensors, and human-machine interfaces. 相似文献
1000.
In this paper, inaccurate spectrum detecting by the secondary user (SU) is taken into account. The impact of the interference caused by the SUs due to miss detection on the primary user (PU) in a spectrum sharing network is analyzed, and those SU nodes of correct detection are assumed to act as potential relays to assist the PU transmission process based on two proposed cooperative transmission schemes, referred to as, the distance based and the signal-to-noise-ratio (SNR) based schemes. We utilize stochastic geometry to analyze the impact of the secondary network parameters and cooperative transmission schemes on a typical primary source–destination (S–D) pair for the SU relay assisted spectrum sharing networks in Rayleigh fading environment. Using this approach, closed-form expressions for the primary system success probabilities with those cooperative transmission schemes as well as the PU direct re-transmission scheme are derived respectively. Simulations confirm our analytical derivations and results demonstrate that significant improvement on the PU success probability by using SU cooperative transmission schemes, and the SNR based scheme is superior to the distance based scheme. 相似文献