全文获取类型
收费全文 | 113053篇 |
免费 | 12947篇 |
国内免费 | 6906篇 |
专业分类
电工技术 | 10300篇 |
技术理论 | 6篇 |
综合类 | 7771篇 |
化学工业 | 23044篇 |
金属工艺 | 10591篇 |
机械仪表 | 5375篇 |
建筑科学 | 10259篇 |
矿业工程 | 4126篇 |
能源动力 | 6243篇 |
轻工业 | 8188篇 |
水利工程 | 2380篇 |
石油天然气 | 6182篇 |
武器工业 | 1467篇 |
无线电 | 10237篇 |
一般工业技术 | 14049篇 |
冶金工业 | 6816篇 |
原子能技术 | 1583篇 |
自动化技术 | 4289篇 |
出版年
2024年 | 535篇 |
2023年 | 1956篇 |
2022年 | 3282篇 |
2021年 | 4150篇 |
2020年 | 4430篇 |
2019年 | 3860篇 |
2018年 | 3645篇 |
2017年 | 4345篇 |
2016年 | 4543篇 |
2015年 | 4606篇 |
2014年 | 6999篇 |
2013年 | 6900篇 |
2012年 | 8182篇 |
2011年 | 8432篇 |
2010年 | 5999篇 |
2009年 | 6325篇 |
2008年 | 5583篇 |
2007年 | 7248篇 |
2006年 | 6731篇 |
2005年 | 5564篇 |
2004年 | 4720篇 |
2003年 | 4118篇 |
2002年 | 3629篇 |
2001年 | 3205篇 |
2000年 | 2703篇 |
1999年 | 2203篇 |
1998年 | 1710篇 |
1997年 | 1375篇 |
1996年 | 1183篇 |
1995年 | 919篇 |
1994年 | 723篇 |
1993年 | 538篇 |
1992年 | 497篇 |
1991年 | 424篇 |
1990年 | 346篇 |
1989年 | 278篇 |
1988年 | 198篇 |
1987年 | 131篇 |
1986年 | 110篇 |
1985年 | 111篇 |
1984年 | 94篇 |
1983年 | 67篇 |
1982年 | 74篇 |
1981年 | 51篇 |
1980年 | 48篇 |
1979年 | 15篇 |
1975年 | 12篇 |
1964年 | 10篇 |
1959年 | 19篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
连续聚合法生产高粘度PA6 总被引:2,自引:0,他引:2
介绍连续聚合法生产高粘度PA6的聚合工艺,特点及产品性能指标,并介绍了关键生产设备的特点及作用。 相似文献
952.
Chih-Kuang Jack Lin Darrell F. Socie Youren Xu Avigdor Zangvil 《Journal of the American Ceramic Society》1992,75(3):637-648
Failure mechanisms of an alumina, tested at 1200°C under static and various cyclic loading conditions, were examined. Slow crack growth of a single crack is the dominant mechanism for the failure in specimens under cyclic loading with a short duration of maximum stress at all applied stress levels, as well as at high applied loads for static loading and cyclic loading with a longer hold time at maximum stress. At low stress levels, failure of static loading and cyclic loading with a longer hold time at maximum stress might occur by formation and/or growth of multiple macrocracks. More importantly, for all the given loading conditions. The viscous glassy phase behind the crack tip could have a bridging effect on the crack surfaces. A simplified model for calculating effective stress intensity factor at the crack tip under static and various cyclic loading demonstrated a trend consistent with the stress–life data. 相似文献
953.
954.
通过熔融共混使纳米CaCO3粒子周围包覆上一层TPE橡胶,制备出纳米CaCO3母料,用其与PP、ABS共混复合制备出ABS/PP合金纳米填料复合物.该复合材料力学性能及熔体流动性能测试结果表明,纳米CaCO3含量在试验用量范围内,ABS纳米CaCO3复合物的拉伸强度随填料含量的增加而增加,当母料含量为17%,母料中纳米CaCO3填料含量为60%左右时有较佳的冲击性能;ABS/PP纳米CaCO3复合物在PP含量9%~10%时有最好的拉伸强度和冲击强度;纳米CaCO3填料含量对复合物的拉伸强度影响不大,随其用量增加对冲击强度有明显的提高;熔体流动性能在PP含量10%左右时达最大,但随填料含量增加而下降. 相似文献
955.
956.
电除尘器绝缘子的设计与选择 总被引:1,自引:0,他引:1
根据电除尘器绝缘子的功能、工况条件等特点,分别从材质、外形尺寸等方面介绍了设计和选择的注意事项。为用户合理地选择电除尘器绝缘子提供了帮助。 相似文献
957.
The poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution 1H NMR, 29Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the 1H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic Tg and Tdec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
958.
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
959.
960.
The effects of oxyen plasma treatment on the surface chemistry of Spectra 1000® high modulus polyethylene fibers and on the mechanical properties of fiber-reinforced composites of the fibers in a Bis-GMA based acrylic resin have been studied. X-ray photoelectron spectroscopy and diffuse reflectance FTIR spectroscopy have been used to show that the majority of oxygen on the fiber surface exists mostly in the form of ether and/or epoxy linkages, with carbonyl-, carboxylic- and ester-containing compounds accounting for less than 10 percent of the total. While the untreated and plasma-treated fibers have similar chemical compositions, the surfaces of the plasma-treated fibers are more polar and the oxygen is chemically bonded instead of being merely physisorbed. The interfacial shear strength between the fibers and the acrylic resin is increased by a factor of 2.3 by the plasma treatment indicating the presence of a weak boundary layer on the surface of the untreated fibers. The hydrolytic stability of the composite interfaces was investigated for fibers sized with several Bis-GMA-based adhesives. Maximum stability was attained by sizing with Bis-GMA containing a peroxide catalyst or an amine accelerator. The flexural properties of composites utilizing plasma-treated and untreated fibers were compared in three-point bending. The ultimate bending loads for composites using treated fibers were much higher than those for composites with untreated fibers, but only a fraction of that for glass or Kevlar®-reinforced materials. 相似文献