全文获取类型
收费全文 | 305900篇 |
免费 | 29242篇 |
国内免费 | 17603篇 |
专业分类
电工技术 | 24413篇 |
技术理论 | 10篇 |
综合类 | 34177篇 |
化学工业 | 32365篇 |
金属工艺 | 13026篇 |
机械仪表 | 24975篇 |
建筑科学 | 36415篇 |
矿业工程 | 12760篇 |
能源动力 | 12098篇 |
轻工业 | 20768篇 |
水利工程 | 13137篇 |
石油天然气 | 13855篇 |
武器工业 | 3787篇 |
无线电 | 19205篇 |
一般工业技术 | 33876篇 |
冶金工业 | 12244篇 |
原子能技术 | 4595篇 |
自动化技术 | 41039篇 |
出版年
2024年 | 1265篇 |
2023年 | 3675篇 |
2022年 | 7307篇 |
2021年 | 8588篇 |
2020年 | 9312篇 |
2019年 | 7844篇 |
2018年 | 7714篇 |
2017年 | 9616篇 |
2016年 | 11144篇 |
2015年 | 11695篇 |
2014年 | 19148篇 |
2013年 | 18770篇 |
2012年 | 23101篇 |
2011年 | 24498篇 |
2010年 | 18191篇 |
2009年 | 18682篇 |
2008年 | 17315篇 |
2007年 | 21137篇 |
2006年 | 18454篇 |
2005年 | 15474篇 |
2004年 | 12948篇 |
2003年 | 11078篇 |
2002年 | 9145篇 |
2001年 | 7555篇 |
2000年 | 6564篇 |
1999年 | 5567篇 |
1998年 | 4567篇 |
1997年 | 3920篇 |
1996年 | 3247篇 |
1995年 | 2812篇 |
1994年 | 2443篇 |
1993年 | 1790篇 |
1992年 | 1637篇 |
1991年 | 1175篇 |
1990年 | 991篇 |
1989年 | 909篇 |
1988年 | 702篇 |
1987年 | 437篇 |
1986年 | 385篇 |
1985年 | 271篇 |
1984年 | 309篇 |
1983年 | 265篇 |
1982年 | 231篇 |
1981年 | 140篇 |
1980年 | 115篇 |
1979年 | 94篇 |
1978年 | 59篇 |
1977年 | 56篇 |
1976年 | 54篇 |
1959年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
标准物质在分析测试中的重要地位及发展前景 总被引:2,自引:0,他引:2
标准物质在分析测试领域中无论在定值,方法的研究,误差确定等方面都有着重要地位。标准物质的质量保证及正确使用也应引起我们重视。随着科学技术迅速发展标准物质有着广阔发展前景。 相似文献
83.
84.
冶金石灰是石灰石经过工业煅烧的产品。其二氧化碳含量低,且经过高温煅烧后基本不含有机物。无需按照《石灰石、白云石化学分析国家标准中二氧化碳的化学分析方法》中用酸进行试样分解,只需在1200℃高温中灼烧,使石灰中残留的或煅烧后吸收空气中二氧化碳而形成的碳酸盐分解,象通常测定含碳耐火材料中二氧化碳那样,采用气体容量法进行测定。 相似文献
85.
86.
87.
88.
Gyeong-Ho Kim 《Computer Methods in Applied Mechanics and Engineering》2008,198(2):234-244
A continuum-based modeling of coupled electrostatics-structure interactions is presented for the frequency computations of MEMS devices. The present general formulation of electrostatics accounting for free space is validated first by specializing it to one-dimensional uniform motion of conducting surfaces and comparing the resulting electrostatics to conventional lumped models. The general coupled electrostatics-structure interactions are then applied for the prediction of resonant frequencies of MEMS devices due to bias-voltage changes and temperature variations. Comparisons of predicted resonant frequencies obtained by the present coupled electrostatics-structure interaction models with experimental results available in the literature demonstrate that the proposed continuum-based interaction modeling yields high-confidence predictions of resonant frequencies of MEMS devices. 相似文献
89.
Heat resistant coatings are required primarily for stacks, exhaust pipes, reactors, space crafts and similar equipments that are permanently or occasionally exposed to elevated temperatures. High-temperature coatings are generally based on silicone resin with ceramic and metallic pigments. In this study, iron oxide, cobalt oxide (thermo chromic compound) and aluminum oxide are used for the preparation of four new types of coloured pigments. The thermal resistant characteristics of these ceramic pigments were studied by differential thermal analysis, thermo gravimetric analysis and differential scanning calorimetric analysis. These ceramic pigments are found to be thermally stable up to 400 °C. 相似文献
90.
Vatroslav Bubalo Vjekoslav Jerolimov Ivo Bau
i Mladen Andreis Zorica Veksli 《Polymer International》2005,54(5):848-853
The electron‐spin‐resonance (ESR) spin‐probe method, was used to study the heterogeneity of denture resins based on poly(methyl methacrylate). Results for three resins processed by microwave energy, conventional curing and cold curing (depending on the curing procedure and exposed to ageing in various environmental conditions) were compared. All three cured resins were stored over the same time (1200 h) in distilled water at ambient temperature and in artificial saliva at 348 K. The temperature‐dependent ESR spectra of a spin probe dispersed in the denture resins are analyzed in terms of line‐shapes and line‐widths. The appearance of two spectral components was taken as an indication of resin heterogeneity. The results reveal that the cold‐cured resin has a lower local density in comparison with microwave and conventionally cured resin. The amount of residual monomer also contributes to the local motion of polymer segments. The change of denture resins exposed to ageing is influenced both by the structure of the original resin and the ageing conditions. Restricted motion of a spin probe incorporated into the acrylic resins exposed to accelerated ageing suggests additional crosslinking of polymer chains. The differences are observed for all the investigated resins, but the highest change is observed with the cold‐cured resin. The ESR results are accompanied by Tg and Tm measurements. Copyright © 2005 Society of Chemical Industry 相似文献