全文获取类型
收费全文 | 155567篇 |
免费 | 21560篇 |
国内免费 | 11136篇 |
专业分类
电工技术 | 14712篇 |
技术理论 | 4篇 |
综合类 | 15299篇 |
化学工业 | 19626篇 |
金属工艺 | 10379篇 |
机械仪表 | 11322篇 |
建筑科学 | 12009篇 |
矿业工程 | 5586篇 |
能源动力 | 4707篇 |
轻工业 | 17424篇 |
水利工程 | 5851篇 |
石油天然气 | 4923篇 |
武器工业 | 2031篇 |
无线电 | 17257篇 |
一般工业技术 | 14914篇 |
冶金工业 | 6176篇 |
原子能技术 | 2671篇 |
自动化技术 | 23372篇 |
出版年
2025年 | 28篇 |
2024年 | 2756篇 |
2023年 | 3134篇 |
2022年 | 5902篇 |
2021年 | 7567篇 |
2020年 | 5615篇 |
2019年 | 4032篇 |
2018年 | 4227篇 |
2017年 | 4794篇 |
2016年 | 4500篇 |
2015年 | 6699篇 |
2014年 | 8358篇 |
2013年 | 10248篇 |
2012年 | 11948篇 |
2011年 | 12397篇 |
2010年 | 11981篇 |
2009年 | 11538篇 |
2008年 | 11819篇 |
2007年 | 11551篇 |
2006年 | 10117篇 |
2005年 | 8284篇 |
2004年 | 6338篇 |
2003年 | 4905篇 |
2002年 | 5378篇 |
2001年 | 4866篇 |
2000年 | 3349篇 |
1999年 | 1686篇 |
1998年 | 760篇 |
1997年 | 624篇 |
1996年 | 509篇 |
1995年 | 460篇 |
1994年 | 369篇 |
1993年 | 261篇 |
1992年 | 243篇 |
1991年 | 187篇 |
1990年 | 146篇 |
1989年 | 124篇 |
1988年 | 109篇 |
1987年 | 76篇 |
1986年 | 55篇 |
1985年 | 40篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 49篇 |
1979年 | 32篇 |
1977年 | 11篇 |
1959年 | 26篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
介绍了几种胶辊用混炼硅橡胶的配制,包括低硬度胶辊用混炼硅橡胶、低环硅氧烷含量的胶辊用混炼硅橡胶、送纸胶辊用混炼硅橡胶及工业胶辊用混炼硅橡胶的配制。 相似文献
32.
33.
CeO2 particles confined within the pores of an SBA-15 mesoporous silica host were prepared by incipient wetness impregnation (IMP)
and deposition precipitation (DP) methods. The materials were characterized by XRD, N2-adsorption and temperature programmed reduction (TPR) to evaluate the structure, texture, and redox properties. The preparation
procedure had significant impact on the assembling mode of CeO2 inside the SBA-15 mesopores. A high dispersion of CeO2 particles was achieved via DP, whereas the dispersion of CeO2 prepared by IMP was found to be inhomogeneous and CeO2 partially blocked the pores. The CO conversion in the water-gas-shift reaction was enhanced over 1 wt% Pt supported on CeO2-modified SBA-15 obtained by DP. 相似文献
34.
The glass transition temperatures (Tg's) of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers were measured using thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). The polymers studied had number-average molecular weights from 3000 to 250,000 g/mole. The results indicate that the composition dependence of the Tg's for the copolymers and terpolymers can be satisfactorily described by a general Fox equation. In general, the measured Tg's of the copolymer and terpolymer samples depend more on the steric effects of the constituent pendent groups than on their molecular weights. The chain flexibility rather than the size of the pendent group is the determining factor in the glass transition properties of the styrene polymers. 相似文献
35.
ZHENG Nan YANG Ping WANG QiYi YANG ZhongHai & HUANG Nan Key Laboratory of Advanced Technology for Materials of Education Ministry Key Laboratory of Artificial Organ Surface Engineering of Sichuan School of Materials Science Engineering Southwest Jiaotong University Chengdu China 《中国科学:信息科学(英文版)》2010,(1)
Microgrooves were prepared on Si(100) surface by photolithography and wet etching.Subsequently,Si-N-O films were deposited on the microgrooves by unbalanced magnetron sputtering(UBMS) and micro-patterned surfaces of Si-N-O films were obtained.The size of the micropatterns was measured by surface profilometer.The chemical composition of Si-N-O films were characterized by X-ray photoelectron spectrometry(XPS) and the wettability of the micropatterned surfaces was evaluated by contact angle measurement.The beh... 相似文献
36.
Potassium humate was extracted from brown coal.A novel super absorbent composite,poly (acrylic acid-co-acrylamide)/potassium humate (PAA-AM/KHA),was prepared by graft polymerization of acrylic acid,acrylamide and coal based potassium humate using N,N'-methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator.The effects of reaction temperature,degree of neutralization of the poly (acrylic acid) and the amounts of crosslinker,initiator and potassium humate were investigated.Salt resistance tests were also carried out.The composite prepared under optimal conditions had a potassium humate content of 10% and exhibited a water absorption of 770 g/g in distilled water,and 349,286 and 41 g/g in 0.5 mol/L KC1,MgCl2 and AlCl3 solutions respectively.The results indicate that the salt resistance of PAA-AM/KHA was superior to that of poly (acrylic acid-co-acrylamide) because of the collaborative effect of functional groups of the coal based potassium humate.The PAA-AM/KHA micro powder was characterized by IR spectroscopy and the micrographic surface was characterized by scanning electron microscopy.Introduction of potassium humate into the poly (acrylic acid-co-acrylamide) structure creates a composite more suitable for use as a water-managing material in the renewal of arid and desert environments.The salt resisting property of the composite is improved,production costs are reduced and the growth stimulant effect is still present. 相似文献
37.
基于Java3D的虚拟雕塑系统的设计与实现 总被引:2,自引:0,他引:2
针对雕塑作品构思和设计阶段的需求,开发了一个基于Java3D中索引曲面造型方法的虚拟雕塑系统.可以用简单的交互操作,模仿雕塑的手工过程,修改形体几何信息.通过对变形结果的展现、比较和修改,优化设计效果,给出修改形体拓扑结构的实现方法,丰富了虚拟雕塑操作的种类,提高了模型的变形能力.该系统操作方便,对用户使用的技术水平要求低,与专业雕塑人员习惯操作比较吻合,并可推广到工艺品、玩具、景观的方案设计等多个领域. 相似文献
38.
提出了呼叫中心模型采用业务与交换分离的设计思想,以Active X技术对中间层进行封装,业务层通过方法和事件与中间层交互。由于交换接入层的消息驱动机制,在Active X控件方法的实现上采用了DFA理论,通过DFA各状态的转换来完成相应的功能。 相似文献
39.
40.
物联网作为未来的发展趋势之一,将在各个方面决定未来世界和人类社会的发展方向。而自智慧地球、感知中国等战略提出以来,世界各国也纷纷开展物联网领域的规划布局,将物联网建设上升到国家战略。物联网在全世界范围内掀起了继计算机和互联网之后的第三次信息革命浪潮。在这空前火爆的物联网宏观背景下,微观企业也不可避免的受到物联网影响。在这一背景下,通过分析物联网环境对企业内部控制环境的影响。本文认为,物联网环境下企业内部控制环境将更加信息化、虚拟化、智能化。 相似文献