全文获取类型
收费全文 | 124092篇 |
免费 | 12073篇 |
国内免费 | 7120篇 |
专业分类
电工技术 | 6635篇 |
综合类 | 10085篇 |
化学工业 | 21256篇 |
金属工艺 | 13218篇 |
机械仪表 | 9688篇 |
建筑科学 | 10724篇 |
矿业工程 | 4406篇 |
能源动力 | 5759篇 |
轻工业 | 10865篇 |
水利工程 | 3670篇 |
石油天然气 | 5048篇 |
武器工业 | 1142篇 |
无线电 | 10100篇 |
一般工业技术 | 15111篇 |
冶金工业 | 6438篇 |
原子能技术 | 1793篇 |
自动化技术 | 7347篇 |
出版年
2024年 | 542篇 |
2023年 | 1986篇 |
2022年 | 3357篇 |
2021年 | 4082篇 |
2020年 | 4329篇 |
2019年 | 3718篇 |
2018年 | 3523篇 |
2017年 | 4484篇 |
2016年 | 4655篇 |
2015年 | 4875篇 |
2014年 | 7097篇 |
2013年 | 8091篇 |
2012年 | 9174篇 |
2011年 | 9682篇 |
2010年 | 6840篇 |
2009年 | 6979篇 |
2008年 | 6350篇 |
2007年 | 8089篇 |
2006年 | 7424篇 |
2005年 | 5981篇 |
2004年 | 5137篇 |
2003年 | 4384篇 |
2002年 | 3734篇 |
2001年 | 3207篇 |
2000年 | 2746篇 |
1999年 | 2237篇 |
1998年 | 1815篇 |
1997年 | 1599篇 |
1996年 | 1422篇 |
1995年 | 1073篇 |
1994年 | 956篇 |
1993年 | 718篇 |
1992年 | 649篇 |
1991年 | 497篇 |
1990年 | 435篇 |
1989年 | 286篇 |
1988年 | 256篇 |
1987年 | 134篇 |
1986年 | 157篇 |
1985年 | 130篇 |
1984年 | 118篇 |
1983年 | 91篇 |
1982年 | 73篇 |
1981年 | 29篇 |
1980年 | 44篇 |
1979年 | 32篇 |
1977年 | 8篇 |
1975年 | 6篇 |
1959年 | 18篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We describe a new, real-time, noninvasive method for dis-bond (delamination) detection which is based on a technique known as impulsive stimulated thermal scattering (ISTS). We first explain the ISTS technique and compare data from polyimide films tightly bound to silicon substrates with data from unsupported polyimide films. The observed differences in the data from these two cases are readily understandable and offer an unmistakable signature for delaminations. We demonstrate ISTS dis-bond detection by locating and mapping out randomly-distributed and spatially-fine regions of delamination in a polyimide film-silicon substrate system. Finally, we present two simple physical models of the interfacial region which comprehensively describe acoustic data from the tightly-bound and the unsupported samples. With insight from simulations using these models, we suggest how ISTS might be used to determine interfacial adhesion quality and we show how ISTS sensitivity to interfacial effects can be adjusted. 相似文献
992.
低温共烧陶瓷技术及其应用 总被引:3,自引:0,他引:3
低温共烧陶瓷(low temperature co-fired ceramic,LTCC)技术是实现电子元件小型化、片式化的一种理想的封装技术,已成为电子元件集成的主要工艺方式,引起了人们的广泛关注。本文详细叙述了LTCC技术的特点、LTCC材料体系、国内外发展现状以及LTCC技术在电子元件集成中的应用。认为利用LTCC技术来实现电源、有源和无源器件的一体化将是今后信息功能陶瓷发展的一个重要方向。我国应该抓住LTCC技术所面临的前所未有的发展机遇,大力开发具有自主知识产权的LTCC技术,整体提升我国在电子集成领域的技术水平和国际竞争力。 相似文献
993.
铝电解电容器用新型宽温高压工作电解液 总被引:3,自引:0,他引:3
采用异癸二酸铵为主溶质,乙二醇和γ-丁内酯为复合溶剂,制备新型宽温(-40~105℃)、高压(400 V)铝电解电容器工作电解液,并检测了该电解液和用该电解液生产的电解电容器的性能。测试结果表明,该工作电解液25℃时电导率达到1.6 mS/cm,闪火电压为480 V,-40℃下未见晶体析出;CD 110/400 V铝电解电容器试样的漏电流≤10μA,损耗0.03,容量变化率只有-3%。经过105℃高温贮存250 h后各项电气性能不仅优于国家标准,而且能达到严格的企业标准。 相似文献
994.
On the Predominant Electron-Donicity of Polar Solid Surfaces 总被引:2,自引:0,他引:2
The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γAB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ⊖/γ⊕), measured on the hydrated surface. 相似文献
995.
Carbon Aerogels as Electrode Material in Supercapacitors 总被引:5,自引:0,他引:5
U. Fischer R. Saliger V. Bock R. Petricevic J. Fricke 《Journal of Porous Materials》1997,4(4):281-285
Due to their large specific surface area and their high electrical conductivity carbon aerogels are promising materials for electrodes in electrochemical double-layer capacitors (supercapacitor). The carbon aerogels were made via pyrolysis of resorcinol formaldehyde aerogels. The latter were prepared by supercritical and subcritical drying as well. The important findings of our investigation were, that the highest capacities of 46 F/cm3 were measured for samples with a density of about 800 kg/m3 pyrolyzed at 800°C. Also it was shown that RF-gels with molar resorcinol/catalyst ratios 1000 or higher can be dried subcritically without cracking or significant shrinkage. Carbon aerogels derived from these RF-aerogels have a small mesopore surface area, however an especially large micropore area. They provide electrical capacities which are most suitable for their use in supercapacitors. 相似文献
996.
介绍了环糊精和表面活性剂作为有序介质在室温磷光中的研究进展.并对各种方法的特点和应用情况作了简要概括。认为环糊精和表面活性剂混合介质能大大提高发光物质的室温磷光.而且操作简便.应用前景广阔。 相似文献
997.
电晕法处理超高相对分子质量聚乙烯纤维 总被引:3,自引:1,他引:3
吴涛 《高科技纤维与应用》2005,30(6):14-16
用电晕法对超高相对分子质量聚乙烯纤维进行了表面处理。利用DPPH检测纤维表面自由基的产生和变化,并用XPS表面元素分析、SEM等方法探讨了纤维表面性能处理前后的变化。实验发现,通过电晕处理后,纤维复合材料的抗剪切强度从未处理的5.98MPa提高到14.3MPa。 相似文献
998.
999.
A new kind of organophilic clay, cotreated by methyl tallow bis‐2‐hydroxyethyl quaternary ammonium and epoxy resin into sodium montmorillonite (to form a strong interaction with polyamide 66 matrix), was prepared and used in preparing PA66/clay nanocomposites (PA66CN) via melt‐compounding method. Three different types of organic clays, CL30B–E00, CL30B–E12, and CL30B–E23, were used to study the effect of epoxy resin in PA66CN. The morphological, mechanical, and thermal properties have been studied using X‐ray diffraction, transmission electron microscopy (TEM), mechanical, and thermal analysis, respectively. TEM analysis of the nanocomposites shows that most of the silicate layers were exfoliated to individual layers and to some thin stacks containing a few layers. PA66CX–E00 and PA66CX–E12 had nearly exfoliated structures in agreement with the SAXS results, while PA66CX–E23 shows a coexistence of intercalated and exfoliated structures. The storage modulus of PA66 nanocomposites was higher than that of the neat PA66 in the whole range of tested temperature. On the other hand, the magnitude of the loss tangent peak in α‐ or β‐transition region decreased gradually with the increase in the clay loading. Multiple melting behavior in PA66 was also observed. Thermal stability more or less decreased with an increasing inorganic content. Young's modulus and tensile strength were enhanced by introducing organoclay. Among the three types of nanocomposites prepared, PA66CX–E12 showed the highest improvement in properties, while PA66CX–E23 showed properties inferior to that of PA66CX–E00 without epoxy resin. In conclusion, an optimum amount of epoxy resin is required to form the strong interaction with the amide group of PA66. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1711–1722, 2006 相似文献
1000.