全文获取类型
收费全文 | 7761篇 |
免费 | 1124篇 |
国内免费 | 700篇 |
专业分类
电工技术 | 568篇 |
综合类 | 744篇 |
化学工业 | 609篇 |
金属工艺 | 546篇 |
机械仪表 | 548篇 |
建筑科学 | 775篇 |
矿业工程 | 234篇 |
能源动力 | 324篇 |
轻工业 | 118篇 |
水利工程 | 162篇 |
石油天然气 | 202篇 |
武器工业 | 114篇 |
无线电 | 2326篇 |
一般工业技术 | 1172篇 |
冶金工业 | 261篇 |
原子能技术 | 65篇 |
自动化技术 | 817篇 |
出版年
2024年 | 25篇 |
2023年 | 147篇 |
2022年 | 192篇 |
2021年 | 266篇 |
2020年 | 342篇 |
2019年 | 347篇 |
2018年 | 289篇 |
2017年 | 345篇 |
2016年 | 361篇 |
2015年 | 361篇 |
2014年 | 424篇 |
2013年 | 529篇 |
2012年 | 549篇 |
2011年 | 593篇 |
2010年 | 405篇 |
2009年 | 499篇 |
2008年 | 415篇 |
2007年 | 543篇 |
2006年 | 483篇 |
2005年 | 381篇 |
2004年 | 331篇 |
2003年 | 278篇 |
2002年 | 250篇 |
2001年 | 235篇 |
2000年 | 156篇 |
1999年 | 163篇 |
1998年 | 110篇 |
1997年 | 92篇 |
1996年 | 81篇 |
1995年 | 82篇 |
1994年 | 63篇 |
1993年 | 41篇 |
1992年 | 39篇 |
1991年 | 39篇 |
1990年 | 46篇 |
1989年 | 22篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有9585条查询结果,搜索用时 15 毫秒
11.
Organic conductor is a kind of organic compound which has special electronic and magnetic properties. The research of the organic compounds has received considerable attention because of their potential applications in many areas. The molecular conductive units are theoretically investigated as well as their energy gap and charge distribution. The relationship of conductivity and micro-mechanism is discussed. 相似文献
12.
宽带建设低潮期实际上是一次优胜劣汰的过程,宽带运营竞争的手段将由低价竞争转向服务质量和特色的竞争。应在重视宽带接入建设的同时,也要重视业务运营管理平台的建设。应从长远考虑,不应仅为了节省投资而降低对设备的要求。由于降低成本的主要方向是在线缆部分,因此EVDSL技术应用的速度将大大超过人们的预期。在网络建设上,IPDSLAM虽有优势但也有不足,还需要进一步的成熟、稳定和实践的检验。 相似文献
13.
The bond strength and slip of epoxy-coated reinforcing bars in concrete have been evaluated by carrying out single pullout and double pullout tests. In extended single pullout tests, slip measurements were made while tensile force was applied to reinforcing bars embedded in concrete. In double pullout tests, 20 cycles of load were applied at levels of steel stress between zero and 0·5 times characteristic steel strength. Strains were measured by electrical resistance strain gauges glued inside the bars. Both epoxy-coated and uncoated bars were used in the investigation, to obtain comparative results. The strain gradient along the bar was found to be less for the coated reinforcement. In general, the epoxy coating was found to increase slip in bond and thereby reduce the bond performance of coated bars. 相似文献
14.
Three distinct stages of kink band formation and propagation exist in ductile matrix composites subjected to compressive loading. These stages are called incipient kinking, transient kinking and kink band broadening. Each stage involves a different deformation mode. The mechanics governing each stage are discussed. Incipient kinking, where the peak load is attained, and kink band broadening, where the load attains a steady-state, are important in structural design. Two design philosophies are presented. References to pertinent literature are made throughout. 相似文献
15.
量子阱红外探测器能带结构的计算 总被引:1,自引:1,他引:0
利用电子波在阱与垒的界面上的反射及干涉效应,计算了量子阱红外探测器(QWIP)的能带结构,并对其适用性进行了分析和讨论。通过与K-P模型比较发现,本方法对计算较宽势阱(阱宽大于4nm)的量子阱结构的电子态适合。在垒宽和阱宽不变条件下,用两种方法计算得到的AlGaAs/GaAs量子阱材料中Al组分x与吸收峰值波长λp的关系曲线基本相同。结果说明,在较宽的范围内,本方法对QWIP能带结构的计算是适用且简便的。 相似文献
16.
介绍了作者研制的应用于固态雷达发射机上的L波段500W固态功放组件的工作原理、用途及其主要技术指标。描述了功放组件的设计过程和测试结果。该功放组件在窄脉宽条件下实现了快速上升沿,性能优良,工作稳定可靠。 相似文献
17.
18.
19.
20.
JOHANNA C.M. JACOBS† JACQUES H. HOUBEN† TON VAN VLIET‡ PIETER S. VAN ROON† BEREND KROL† 《International Journal of Food Science & Technology》1994,29(3):321-329
A specially designed tube viscometer was used to measure apparent viscosity during flow of Bologna type sausage emulsions moving through a pipe. Emulsions varied in fat content (from 21.8 to 44.3%) and in moisture/protein ratio (from 3.7 to 5.6), and the effects of added sodium chloride, sodium diphosphate, starch and blood plasma were investigated in a 36% fat, 3.7 moisture/protein emulsion.
The shear stresses determined as a function of shear rate were fitted by a power law. Yield stress of the emulsions was negligible relative to the applied stress. However, inspection of the flow profiles indicated that considerable slip of the sausage emulsion occurred at the pipe wall. Both emulsion flow and slip contribute to overall flow behaviour, so a kind of effective viscosity is determined. Intrinsic rheological properties and wall slip will both be affected by the composition of the sausage emulsion. 相似文献
The shear stresses determined as a function of shear rate were fitted by a power law. Yield stress of the emulsions was negligible relative to the applied stress. However, inspection of the flow profiles indicated that considerable slip of the sausage emulsion occurred at the pipe wall. Both emulsion flow and slip contribute to overall flow behaviour, so a kind of effective viscosity is determined. Intrinsic rheological properties and wall slip will both be affected by the composition of the sausage emulsion. 相似文献