全文获取类型
收费全文 | 20799篇 |
免费 | 1485篇 |
国内免费 | 676篇 |
专业分类
电工技术 | 981篇 |
技术理论 | 3篇 |
综合类 | 1243篇 |
化学工业 | 3734篇 |
金属工艺 | 998篇 |
机械仪表 | 1256篇 |
建筑科学 | 1608篇 |
矿业工程 | 433篇 |
能源动力 | 555篇 |
轻工业 | 1454篇 |
水利工程 | 331篇 |
石油天然气 | 1058篇 |
武器工业 | 153篇 |
无线电 | 2184篇 |
一般工业技术 | 3060篇 |
冶金工业 | 1175篇 |
原子能技术 | 250篇 |
自动化技术 | 2484篇 |
出版年
2024年 | 74篇 |
2023年 | 283篇 |
2022年 | 443篇 |
2021年 | 590篇 |
2020年 | 488篇 |
2019年 | 445篇 |
2018年 | 468篇 |
2017年 | 590篇 |
2016年 | 530篇 |
2015年 | 702篇 |
2014年 | 837篇 |
2013年 | 1091篇 |
2012年 | 1163篇 |
2011年 | 1247篇 |
2010年 | 1063篇 |
2009年 | 1026篇 |
2008年 | 1101篇 |
2007年 | 1055篇 |
2006年 | 1131篇 |
2005年 | 1101篇 |
2004年 | 696篇 |
2003年 | 658篇 |
2002年 | 605篇 |
2001年 | 526篇 |
2000年 | 675篇 |
1999年 | 726篇 |
1998年 | 626篇 |
1997年 | 555篇 |
1996年 | 490篇 |
1995年 | 456篇 |
1994年 | 334篇 |
1993年 | 248篇 |
1992年 | 208篇 |
1991年 | 169篇 |
1990年 | 134篇 |
1989年 | 116篇 |
1988年 | 90篇 |
1987年 | 44篇 |
1986年 | 48篇 |
1985年 | 43篇 |
1984年 | 18篇 |
1983年 | 5篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Guang-rui Gu Zhi HeYan-chun Tao Ying-ai LiJun-jie Li Hong YinWei-qin Li Yong-nian Zhao 《Vacuum》2003,70(1):17-20
The conductivity of nanometer TiO2 thin films was presented in this paper. The dependence of the conductivity of TiO2 thin films on the thickness of the film and the substrate material were educed. The TiO2 films were deposited by reactive magnetron sputtering of a Ti targets in an Ar+O2 mixture in a conventional sputtering reactor. The thickness of the films deposited on Ti varied in the range from 15 to 225 nm. The resistivity of the films was measured at room temperature in the air. It was found that the conductivity of TiO2 thin films varies in the range from conductor, semiconductor to nonconductor. This was attributed to electrons transfer at the interface between the TiO2 and substrates, and the depth of electrons transfer was determined by the difference of work function. 相似文献
992.
Real-time monitoring of lactate release from brain slices has been studied with an optical two-dimensional (2D) imaging biosensor. The 2D biosensor is prepared by direct immobilization of lactate dehydrogenase (LDH) molecules onto a flat silica glass surface through a covalent binding mechanism. The biosensor is able to spatially differentiate lactate concentration variations with conventional optical microscopic spatial resolution. This biosensor has the capability to effectively detect lactate down to a concentration of 100 nM. The 2D biosensor responds uniformly with 2.5% RSD from pixel to pixel. With a 100 ms response time, this 2D biosensor has the capability of monitoring simultaneously many cells in one image. We have studied the impact of KCI on lactate release from brain slices. Clear differences have been observed in lactate release for different regions of the tissue. The real-time determination of the newly released lactate from the mouse brain slices clearly demonstrates the feasibility of monitoring lactate release from living specimens. The 2D biosensor will enable us to study cellular communications and possibly other biological processes that require simultaneous temporal and spatial resolution. 相似文献
993.
Gu G Schmid M Chiu PW Minett A Fraysse J Kim GT Roth S Kozlov M Muñoz E Baughman RH 《Nature materials》2003,2(5):316-319
Vanadium oxides, such as V2O5, are promising for lithium-ion batteries, catalysis, electrochromic devices and sensors. Vanadium oxides were proposed more than a decade ago for another redox-dependent application: the direct conversion of electrical energy to mechanical energy in actuators (artificial muscles). Although related conducting polymer and carbon nanotube actuators have been demonstrated, electromechanical actuators based on vanadium oxides have not be realized. V2O5 nanofibres and nanotubes provide the potential advantages of low-cost synthesis by sol-gel routes and high charging capacity and long cycle life. Here, we demonstrate electromechanical actuation for obtained high modulus V2O5 sheets comprising entangled V2O5 nanofibres. The high surface area of these V2O5 sheets facilitates electrochemical charge injection and intercalation that causes the electromechanical actuation. We show that the V2O5 sheets provide high Young's modulus, high actuator-generated stress, and high actuator stroke at low applied voltage. 相似文献
994.
To solve the contradiction between convergence rate and steady-state error in least mean square (LMS) algorithm, basing on independence assumption, this paper proposes and proves the optimal step-size theorem from the view of minimizing mean squared error (MSE). The theorem reveals the one-to-one mapping between the optimal step-size and MSE. Following the theorem, optimal variable step-size LMS (OVS-LMS) model, describing the theoretical bound of the convergence rate of LMS algorithm, is constructed. Then we discuss the selection of initial optimal step-size and updating of optimal step-size at the time of unknown system changing. At last an optimal step-size LMS algorithm is proposed and tested in various environments. Simulation results show the proposed algorithm is very close to the theoretical bound. 相似文献
995.
本文用详实的数据说明了静重式力标准机的"逆程"现象及对传感器检测结果的影响,介绍了电液伺服技术解决"逆程"现象的几个关键技术问题,肯定了电液伺服技术是消除"逆程"现象的一个行之有效的途径. 相似文献
996.
Three-dimensional fluorescence spatial distributions under single-photon and two-photon excitation within a turbid medium are studied with Monte Carlo simulation. It is demonstrated that two-photon excitation has an advantage of producing much less fluorescence light outside the focal region compared with single-photon excitation. With the increase of the concentration of scattering particles in a turbid medium, the position of the maximum fluorescence intensity point shifts from the geometric focal region toward the medium surface. Further studies show that the optical sectioning property of two-photon fluorescence microscopy is degraded in thick turbid media or when the numerical aperture of an objective becomes low. 相似文献
997.
DyPt2 films were prepared by alternate deposition thin Dy and Pt layers on glass substrates by DC magneto controlled sputtering method. The XRD data indicated that for as-deposited Dy/Pt films, and the periodic layered structures along thickness direction were evidenced with low angle X-ray scattering. With increasing annealing temperature, the compounds of DyPt, DyPt2 and DyPt3 were formed successively at temperature ranging from 300 to 400℃. It was found that the composition reaction DyPt DyPt3→2DyPt2 took place at 500℃. After annealing at 500℃ for 1h, the compounds DyPt and DyPt3 transformed completely into the DyPt2 compound. 相似文献
998.
图像区域的表示和显示是图像处理和图像分析、计算机制图和计算机图形学中的重要研究课题.以顶点链编码为基础,提出一种以顶点链编码来表示二值图像的方法,完成了对于图像区域的简单表示.同时着重提出了一种将用以表示二值图像的顶点链编码转化为原二值图像的算法.该算法对表示二值图像区域的顶点链编码点进行记录处理,配对被记录的顶点链编码点,然后运用水平扫描线来填充图像区域,从而将原图像根据顶点链编码完全恢复出来. 相似文献
999.
以燕莎商城和凯宾斯基酒店的冰蓄冷空调工程为基础,阐述冰蓄冷空调对于平衡华北电网负荷、移峰填谷能够起到积极的作用。通过分析机房内合理配置的冰蓄冷系统设备,满足建筑物最舒适的空调要求,并结合北京市电价政策,分析冰蓄冷空调在节约运行费用方面的收益。 相似文献
1000.