全文获取类型
收费全文 | 138427篇 |
免费 | 9148篇 |
国内免费 | 7324篇 |
专业分类
电工技术 | 9533篇 |
技术理论 | 3篇 |
综合类 | 8865篇 |
化学工业 | 27702篇 |
金属工艺 | 10440篇 |
机械仪表 | 9631篇 |
建筑科学 | 4789篇 |
矿业工程 | 1972篇 |
能源动力 | 4802篇 |
轻工业 | 9192篇 |
水利工程 | 827篇 |
石油天然气 | 5580篇 |
武器工业 | 1140篇 |
无线电 | 16377篇 |
一般工业技术 | 15676篇 |
冶金工业 | 3556篇 |
原子能技术 | 1843篇 |
自动化技术 | 22971篇 |
出版年
2024年 | 356篇 |
2023年 | 1645篇 |
2022年 | 2876篇 |
2021年 | 3376篇 |
2020年 | 2994篇 |
2019年 | 2974篇 |
2018年 | 2766篇 |
2017年 | 3683篇 |
2016年 | 4169篇 |
2015年 | 4545篇 |
2014年 | 6681篇 |
2013年 | 7494篇 |
2012年 | 8035篇 |
2011年 | 10574篇 |
2010年 | 8694篇 |
2009年 | 9744篇 |
2008年 | 8981篇 |
2007年 | 9605篇 |
2006年 | 9001篇 |
2005年 | 7449篇 |
2004年 | 6545篇 |
2003年 | 6336篇 |
2002年 | 5290篇 |
2001年 | 3806篇 |
2000年 | 3268篇 |
1999年 | 2632篇 |
1998年 | 1927篇 |
1997年 | 1557篇 |
1996年 | 1349篇 |
1995年 | 1303篇 |
1994年 | 1169篇 |
1993年 | 960篇 |
1992年 | 727篇 |
1991年 | 464篇 |
1990年 | 314篇 |
1989年 | 318篇 |
1988年 | 198篇 |
1987年 | 140篇 |
1986年 | 139篇 |
1985年 | 117篇 |
1984年 | 106篇 |
1983年 | 72篇 |
1982年 | 79篇 |
1981年 | 81篇 |
1980年 | 108篇 |
1979年 | 40篇 |
1978年 | 29篇 |
1977年 | 34篇 |
1976年 | 29篇 |
1975年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
141.
This paper deals with the investigation of the effect of hygrothermal conditions on the bending of nanoplates using Levy type solution model employing the state-space concept. The nanoplates are assumed to be subjected to a hygrothermal environment. The two-unknown function plate theory is used to derive the governing differential equations on the basis of Eringen's nonlocal elasticity theory. The governing equations contain the small scale effect as well as hygrothermal and mechanical effects. These equations are converted into a set of first-order linear ordinary differential equations with constant coefficients. Analytical solution of bending response for nanoplates under combinations of simply supported, clamped and free boundary conditions is obtained. Comparison of the results with those being in the open literature is made. The influences played by small scale parameter, temperature rise, the degree of moisture concentration, boundary conditions, plate aspect ratio and side-to-thickness ratio are studied. 相似文献
142.
143.
1-read/1-write (1R1W) register file (RF) is a popular memory configuration in modern feature rich SoCs requiring significant amount of embedded memory. A memory compiler is constructed using the 8T RF bitcell spanning a range of instances from 32 b to 72 Kb. An 8T low-leakage bitcell of 0.106 μm2 is used in a 14 nm FinFET technology with a 70 nm contacted gate pitch for high-density (HD) two-port (TP) RF memory compiler which achieves 5.66 Mb/mm2 array density for a 72 Kb array which is the highest reported density in 14 nm FinFET technology. The density improvement is achieved by using techniques such as leaf-cell optimization (eliminating transistors), better architectural planning, top level connectivity through leaf-cell abutment and minimizing the number of unique leaf-cells. These techniques are fully compatible with memory compiler usage over the required span. Leakage power is minimized by using power-switches without degrading the density mentioned above. Self-induced supply voltage collapse technique is applied for write and a four stack static keeper is used for read Vmin improvement. Fabricated test chips using 14 nm process have demonstrated 2.33 GHz performance at 1.1 V/25 °C operation. Overall Vmin of 550 mV is achieved with this design at 25 °C. The inbuilt power-switch improves leakage power by 12x in simulation. Approximately 8% die area of a leading 14 nm SoC in commercialization is occupied by these compiled RF instances. 相似文献
144.
介绍了免费的TCP/IP协议栈LWIP开发工具和环境,分析了如何实现LWIP的移植,并给出了一种嵌入式系统与网络互联的新思路。 相似文献
145.
146.
高频结构仿真器(HFSS)是一种微波器件设计软件,该软件界面友好,通过仿真计算减小了调试工作量,使得微波器件的设计变得简单易行。本文利用HFSS对波导魔T进行了仿真分析,得到了该器件的S参数和动、静态场的分布情况,并对该器件进行了优化设计。 相似文献
147.
ZnO基薄膜晶体管的研究 总被引:2,自引:1,他引:1
ZnO是一种宽带隙的光电半导体材料,能应用于很多领域,如可用在压敏变阻器、声表面波器件、气敏元件、紫外光探测等。ZnO也可以作为有源层应用于薄膜晶体管(TFT)中。ZnO基薄膜晶体管具有以下突出优势:对于可见光部分平均具有80%以上的透射率,迁移率可以高达36cm2/V·s,开/关电流比大于106,可在较低温度(甚至室温)下制备。基于这些优点,ZnOTFT具有取代有源矩阵液晶显示器中常规a-SiTFT的趋势。同时对ZnOTFT的研究也推动了透明电子学的发展。本文阐述了ZnOTFT优越的电学性能,指出了其目前尚存在的不足,并对其发展前景进行了展望。 相似文献
148.
X.W. Lou C. Yuan E. Rhoades Q. Zhang L.A. Archer 《Advanced functional materials》2006,16(13):1679-1684
We report a general template strategy for rational fabrication of a new class of nanostructured materials consisting of multicore shell particles. Our approach is demonstrated by encapsulating Au or Pt nanoparticles in silica shells. Other superstructures of these hollow shells, like dimers, trimers, and tetramers can also be formed by nanoparticle‐mediated self‐assembly. We have also used the as‐prepared multicore Au–silica hollow particles to perform the first studies of Ostwald ripening in confined microspace, in which chloride was found to be an efficient mediating ligand. After treatment with aqua regia, Au–Cl complex is formed inside the shell, and is found to be very active under in situ transmission electron microscopy observations while confined in a microcell. This aspect of the work is expected to motivate further in situ studies of confined crystal growth. 相似文献
149.
高分散度Pt/C电催化剂的制备 总被引:3,自引:1,他引:2
Cabot公司Vulcan XC-72型炭黑,经过H2O2氧化处理后作为Pt的载体,H2PtCl6作为金属前驱体制备了高度分散的Pt/C催化剂。讨论了不同条件下H2PtCl6在炭黑上的吸附性能。载体经过H2O2氧化处理24h,H2PtCl6在pH=9下吸收48h,H2 350℃还原2h,可以制备出铂晶粒平均大小为1.8nm的Pt/C电催化剂。 相似文献
150.
Hiromichi Ichinose Masanori Taira Sachiko Furuta Hiroaki Katsuki 《Journal of the American Ceramic Society》2003,86(9):1605-1608
Niobium- or vanadium-doped anatase sols were prepared by hydrothermal treatment of 0.1 mol/dm3 peroxotitanium complex aqueous solutions dissolving 0–10 mol% niobium or vanadium at 100°C for 8 h. Niobium-doping caused the increase of lattice constants of anatase and the shape change of anatase crystal from spindle-like to cubic-like structure, but no change of the optical absorbance. Vanadium-doping caused the decrease of lattice constant of c -axis, the miniaturization of anatase crystal and the increase of optical absorbance at the wavelength from 350–700 nm. 相似文献