全文获取类型
收费全文 | 45723篇 |
免费 | 4912篇 |
国内免费 | 2620篇 |
专业分类
电工技术 | 3707篇 |
技术理论 | 2篇 |
综合类 | 3441篇 |
化学工业 | 6683篇 |
金属工艺 | 2743篇 |
机械仪表 | 3232篇 |
建筑科学 | 3520篇 |
矿业工程 | 1542篇 |
能源动力 | 1303篇 |
轻工业 | 3577篇 |
水利工程 | 1014篇 |
石油天然气 | 2025篇 |
武器工业 | 490篇 |
无线电 | 5766篇 |
一般工业技术 | 4869篇 |
冶金工业 | 1907篇 |
原子能技术 | 565篇 |
自动化技术 | 6869篇 |
出版年
2024年 | 229篇 |
2023年 | 759篇 |
2022年 | 1620篇 |
2021年 | 2161篇 |
2020年 | 1680篇 |
2019年 | 1288篇 |
2018年 | 1550篇 |
2017年 | 1709篇 |
2016年 | 1553篇 |
2015年 | 2391篇 |
2014年 | 2870篇 |
2013年 | 3140篇 |
2012年 | 3578篇 |
2011年 | 3719篇 |
2010年 | 3259篇 |
2009年 | 2943篇 |
2008年 | 2857篇 |
2007年 | 2683篇 |
2006年 | 2484篇 |
2005年 | 2035篇 |
2004年 | 1431篇 |
2003年 | 1121篇 |
2002年 | 1023篇 |
2001年 | 855篇 |
2000年 | 764篇 |
1999年 | 658篇 |
1998年 | 535篇 |
1997年 | 468篇 |
1996年 | 456篇 |
1995年 | 327篇 |
1994年 | 249篇 |
1993年 | 193篇 |
1992年 | 161篇 |
1991年 | 122篇 |
1990年 | 96篇 |
1989年 | 85篇 |
1988年 | 50篇 |
1987年 | 34篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1973年 | 2篇 |
1966年 | 1篇 |
1959年 | 4篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
针对煤矸石粉替代率50%、聚酯纤维掺量0.4%的沥青混合料,开展盐冻耦合作用(NaCl溶液质量分数为0%、7.0%、13.0%、26.5%,冻融循环次数为0、2、4、6、8)下的半圆弯曲(SCB)试验,分析了盐冻耦合作用对SCB试件内部损伤劣化过程的影响.结果表明:NaCl溶液质量分数为13.0%、冻融循环为8次时,盐冻耦合作用对沥青混合料的侵蚀破坏作用最强,试件内部损伤最严重;在煤矸石粉与矿粉质量比为1∶1、聚酯纤维掺量为0.4%的条件下,沥青混合料能够形成高黏性、致密、厚实的沥青膜以及由纤维形成的三维网状结构,从而显著降低盐冻侵蚀对沥青混合料的损伤.通过Poly2D模型对SCB试件的极限拉应力损伤量进行拟合,拟合系数为0.944. 相似文献
3.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
4.
5.
Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We... 相似文献
6.
Pu Mao Jiping Wang Peng Xiao Lixue Zhang Fang Kang Hao Gong 《Ceramics International》2021,47(1):111-120
In this work, we developed a novel system of isovalent Zr4+ and donor Nb5+ co-doped CaCu3Ti4O12 (CCTO) ceramics to enhance dielectric response. The influences of Zr4+ and Nb5+ co-substituting on the colossal dielectric response and relaxation behavior of the CCTO ceramics fabricated by a conventional solid-phase synthesis method were investigated methodically. Co-doping of Zr4+ and Nb5+ ions leads to a significant reduction in grain size for the CCTO ceramics sintered at 1060 °C for 10 h. XRD and Raman results of the CaCu3Ti3.8-xZrxNb0.2O12 (CCTZNO) ceramics show a cubic perovskite structure with space group Im-3. The first principle calculation result exhibits a better thermodynamic stability of the CCTO structure co-doped with Zr4+ and Nb5+ ions than that of single-doped with Zr4+ or Nb5+ ion. Interestingly, the CCTZNO ceramics exhibit greatly improved dielectric constant (~105) at a frequency range of 102–105 Hz and at a temperature range of 20–210 °C, indicating a giant dielectric response within broader frequency and temperature ranges. The dielectric properties of CCTZNO ceramics were analyzed from the viewpoints of defect-dipole effect and internal barrier layer capacitance (IBLC) model. Accordingly, the immensely enhanced dielectric response is primarily ascribed to the complex defect dipoles associated with oxygen vacancies by co-doping Zr4+ and Nb5+ ions into CCTO structure. In addition, the obvious dielectric relaxation behavior has been found in CCTZNO ceramics, and the relaxation process in middle frequency regions is attributed to the grain boundary response confirmed by complex impedance spectroscopy and electric modulus. 相似文献
7.
Neural Processing Letters - This paper presents an approach to identify the unknown parameters of genetic regulatory network (GRN) in finite-time. The adaptive synchronization-based method is used... 相似文献
8.
10.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文