全文获取类型
收费全文 | 105571篇 |
免费 | 12161篇 |
国内免费 | 6060篇 |
专业分类
电工技术 | 9420篇 |
技术理论 | 6篇 |
综合类 | 8103篇 |
化学工业 | 14008篇 |
金属工艺 | 8040篇 |
机械仪表 | 6519篇 |
建筑科学 | 12568篇 |
矿业工程 | 4337篇 |
能源动力 | 4709篇 |
轻工业 | 8876篇 |
水利工程 | 2346篇 |
石油天然气 | 6444篇 |
武器工业 | 1388篇 |
无线电 | 9310篇 |
一般工业技术 | 10387篇 |
冶金工业 | 7088篇 |
原子能技术 | 1142篇 |
自动化技术 | 9101篇 |
出版年
2024年 | 294篇 |
2023年 | 1745篇 |
2022年 | 3315篇 |
2021年 | 4030篇 |
2020年 | 4261篇 |
2019年 | 3525篇 |
2018年 | 3369篇 |
2017年 | 4043篇 |
2016年 | 4352篇 |
2015年 | 4472篇 |
2014年 | 6986篇 |
2013年 | 6404篇 |
2012年 | 8091篇 |
2011年 | 8152篇 |
2010年 | 5889篇 |
2009年 | 6074篇 |
2008年 | 5395篇 |
2007年 | 6984篇 |
2006年 | 6164篇 |
2005年 | 5249篇 |
2004年 | 4340篇 |
2003年 | 3838篇 |
2002年 | 3253篇 |
2001年 | 2834篇 |
2000年 | 2178篇 |
1999年 | 1788篇 |
1998年 | 1250篇 |
1997年 | 976篇 |
1996年 | 910篇 |
1995年 | 696篇 |
1994年 | 558篇 |
1993年 | 394篇 |
1992年 | 335篇 |
1991年 | 270篇 |
1990年 | 213篇 |
1989年 | 167篇 |
1988年 | 129篇 |
1987年 | 96篇 |
1986年 | 58篇 |
1985年 | 80篇 |
1984年 | 71篇 |
1983年 | 42篇 |
1982年 | 46篇 |
1981年 | 38篇 |
1980年 | 64篇 |
1964年 | 38篇 |
1963年 | 31篇 |
1959年 | 29篇 |
1956年 | 24篇 |
1955年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
Sania Saheli Ali Reza Rezvani Azim Malekzadeh Michal Dusek Vaclav Eigner 《International Journal of Hydrogen Energy》2018,43(2):685-694
The silica- and alumina-supported Co–Zn catalysts were synthesized by thermal decomposition of new inorganic precursors [Co4.32Zn1.68(HCO2)18(C2H8N)6]/SiO2 or Al2O3. A novel coordination polymer formulated as [Co4.32Zn1.68(HCO2)18(C2H8N)6] (1) was prepared using the solvothermal technique and characterized by elemental analysis, FT-infrared spectroscopy. Thermal stability of the complex 1 was investigated by thermogravimetric analysis and differential scanning calorimetry, and its structure was determined by single-crystal X-ray diffraction. Characterization of catalysts was carried out using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET specific surface area. The catalysts were evaluated for Fischer–Tropsch synthesis (FTS) in the temperature range 200–300 °C. The results revealed that the synthesized catalysts have higher selectivity to the desired products at 260 °C. The performance of the catalysts was compared to those of catalysts constructed via impregnation method and the fabricated catalysts show higher activity and selectivity than the reference catalysts. 相似文献
85.
针对《高电压与绝缘技术》课程中液体电介质的教学难点,提出了融合前沿研究的液体电介质击穿教学方法。基于前沿的液体放电应用背景与先进的液体放电研究平台,形象地展示液体电介质的动态击穿过程,在教学内容、教学方法、考核方式等方面进行科教融合改进,实施“以学生为中心”理念的课程教学设计。该教学方式取得了较好的教学效果,能够为其它知识点的教学质量提升提供参考。 相似文献
86.
为研究铝合金三角形波纹夹芯板对平头弹体的抗冲击性能及损伤特性,利用有限元软件ABAQUS/Explicit建立弹体冲击靶板的数值模拟模型,并结合实验验证了模型及其参数的有效性。基于数值计算结果,分析了三角形波纹夹芯板几何结构对其防护性能、失效模式和能量吸收的影响规律及机理,并与等面密度单层板进行对比分析,研究结果表明,靶体几何结构对其抗冲击性能存在影响,三角形波纹夹芯板抗冲击性能低于单层板抗冲击性能。此外,增加芯体拓扑结构夹角能显著提高三角形波纹夹芯板的抗冲击性能,并且靶板几何形状会对其失效模式及耗能特性存在影响。 相似文献
87.
88.
The use of touchscreen-based in-vehicle information systems (IVIS) is increasing. To ensure safe driving, it is important to evaluate IVIS task performance during driving situations. Therefore, we proposed a model to assess the task completion time (TCT) of IVIS tasks while driving using a keystroke-level modeling (KLM) technique. The basic assumptions and heuristic rules of driver behaviors were considered. In addition, based on the characteristics of visual and manual IVIS interactions, we determined the basic unit operators (i.e., visual, manual, and mental operators). User experiments were conducted to determine the individual execution times of unit tasks and to measure the TCT of IVIS tasks while driving. Based on the heuristic rules for model development and individual task execution times, we derive a predictive model for the TCT of IVIS tasks. We used a regression analysis to validate the modeling procedure, showing that the observed TCT was found to have a strong positive correlation with the predicted time from the modeling process. The findings showed that the task completion time needed to perform a secondary task in a driving context can be predicted by KLM. This study provides meaningful insights into the design of touchscreen-based IVIS to enhance driving safety. 相似文献
89.
The reduction of chromium-bearing vanadium–titanium magnetite sinter (CVTMS) by CO was investigated at 1123–1223?K. The reduction degree increased with increasing temperature. The isothermal reduction kinetics of CVTMS was analysed, according to Sharp analysis and ln–ln analysis, the kinetic mechanism of reduction process for all samples in different basicity can be represented as f(α)?=?1.61(1?α)[?ln(1?α)]1–1/1.61. The reaction activation energy of all samples (R?=?1.9, 2.1, 2.3, obtained according to the components of the materials burdening used in sintering process) at different reaction degrees were calculated by the model-free method. And the pre-exponential factors of reaction also were calculated by the mathematical method. The rate controlling step for the reduction process under the present reduction condition was chemical reaction. 相似文献
90.
以北方某钢厂100 t转炉为原型,建立顶吹转炉炉内流场的三维数学模型,采用Fluent软件研究了不同高马赫数氧气射流与熔池钢液速度流场分布之间的依赖关系。研究发现,高马赫数氧枪在Ma(马赫数)为2.0~2.3时,曲线平稳,为最佳供氧压力。在提高供氧压力的同时,氧气射流的最大速度、熔池钢液面的冲击直径及冲击深度也随之增加。模拟结果显示,氧气射流在设计工况氧压小于1.0 MPa时,射流之间相互干扰作用最弱;氧气射流在设计工况氧压力大于1.0 MPa后,冲击直径与冲击深度增幅较小。基于上述研究,在实际生产中应用了高马赫数氧枪后,并结合变枪变压操作工艺,可以改善熔池底部钢液流动状况、稳定转炉吹炼过程、控制炉渣喷溅。 相似文献