全文获取类型
收费全文 | 481345篇 |
免费 | 57629篇 |
国内免费 | 39481篇 |
专业分类
电工技术 | 44603篇 |
技术理论 | 2篇 |
综合类 | 52263篇 |
化学工业 | 58633篇 |
金属工艺 | 34166篇 |
机械仪表 | 33613篇 |
建筑科学 | 36174篇 |
矿业工程 | 21204篇 |
能源动力 | 12606篇 |
轻工业 | 55270篇 |
水利工程 | 17092篇 |
石油天然气 | 17587篇 |
武器工业 | 7290篇 |
无线电 | 49519篇 |
一般工业技术 | 40023篇 |
冶金工业 | 20698篇 |
原子能技术 | 7644篇 |
自动化技术 | 70068篇 |
出版年
2024年 | 3210篇 |
2023年 | 8238篇 |
2022年 | 19112篇 |
2021年 | 24145篇 |
2020年 | 17620篇 |
2019年 | 12276篇 |
2018年 | 12979篇 |
2017年 | 15181篇 |
2016年 | 13898篇 |
2015年 | 21880篇 |
2014年 | 27478篇 |
2013年 | 32208篇 |
2012年 | 40110篇 |
2011年 | 42046篇 |
2010年 | 39808篇 |
2009年 | 38069篇 |
2008年 | 39318篇 |
2007年 | 38204篇 |
2006年 | 32564篇 |
2005年 | 26323篇 |
2004年 | 18970篇 |
2003年 | 12709篇 |
2002年 | 12014篇 |
2001年 | 10908篇 |
2000年 | 8655篇 |
1999年 | 3447篇 |
1998年 | 1187篇 |
1997年 | 993篇 |
1996年 | 812篇 |
1995年 | 689篇 |
1994年 | 482篇 |
1993年 | 440篇 |
1992年 | 348篇 |
1991年 | 294篇 |
1990年 | 261篇 |
1989年 | 235篇 |
1988年 | 155篇 |
1987年 | 131篇 |
1986年 | 132篇 |
1985年 | 78篇 |
1984年 | 59篇 |
1983年 | 65篇 |
1982年 | 52篇 |
1981年 | 100篇 |
1980年 | 141篇 |
1979年 | 78篇 |
1977年 | 41篇 |
1976年 | 78篇 |
1959年 | 86篇 |
1951年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献
62.
63.
分别使用AutoCAD、StruCAD 3D及Solid Works软件在石油井架、底座校核中进行强度分析,AutoCAD软件的主要优势在工程制图领域,兼具强度分析功能,适用于单个形状比较规则的型材强度分析;StruCAD 3D是专门针对大型钢结构进行强度校核的分析软件,具有强大的计算处理功能,兼具风载处理能力,在处理大型、复杂结构的时候应优先考虑应用该软件;当遇到需要进行实体造型、模拟实际情况进行校核时,SolidWorks软件较为方便,可以直观地看到应变情况。 相似文献
64.
Dongdong Ji Zheng Liu Bailing Jiang Xiaofei Luo 《International Journal of Hydrogen Energy》2021,46(27):13960-13970
The evaluation of cell's weatherability is of practical interest. To further improve the soluble lead flow battery's weatherability, physiochemical properties of electrolytes containing fluoborate, perchlorate, methanesulfonate and trifluoromethanesulfonate are investigated from ?60 to 50 °C. Activities of CF3SO3H and HClO4 are poor in trifluoromethanesulfonate and perchlorate solutions due to common anion effect. The solubility of lead salt can be improved by increasing temperature, but worsened by increasing acid's content. With the temperature increasing, the conductivity is enhanced, and the viscosity is lowered for four solutions. The same results have been found by increasing acid's content except for CF3SO3H. The high energy efficiency can be achieved for cells over ?40–0 °C using fluoborate and perchlorate solutions, 73.2% at ?40 °C and 78.1% at ?30 °C respectively. Over the temperature range of 20–50 °C, the cells with methanesulfonate and trifluoromethanesulfonate solutions have good performance, 77.4% and 73.7% at 50 °C respectively. 相似文献
65.
66.
设备前期翻料钩摆臂角度设计错误,导致该处液压缸事故频繁,经改造后,将过渡篦条和中间过渡装置拆除。整体标高再次进行定位,实现穿孔出来的毛管直接过渡到轧机入口,无需中间翻料钩装置,以保证设备的正常运转和生产连续性。 相似文献
67.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
68.
69.
大气污染物排放清单是空气质量模拟和空气污染治理的重要依据.本研究比较分析了两套覆盖江苏省的2017年大气污染物排放清单,即分别由上海市环境科学研究院、江苏省环境科学研究院编制的"长三角清单"和"江苏省清单",并结合区域空气质量模型CMAQ评估不同清单对长三角地区2017年1、4、7、10月的空气质量模拟的影响.清单比较结果表明,除二氧化硫(SO2)以外,江苏省清单估算的各污染物排放量较长三角清单低.通过与观测数据比较,发现两套清单对SO2、氮氧化物(NOx)、臭氧(O3)和细颗粒物(PM2.5)的模型模拟性能均较好.江苏省清单与长三角清单两者的模拟结果空间分布接近,其中江苏省清单模拟的PM2.5和O3在长三角多数地区略低于长三角清单的模拟结果(1月O3除外).江苏省清单与长三角清单均能够用于空气质量模式模拟,可为江苏地区的细颗粒物和光化学烟雾污染的控制策略制定提供参考. 相似文献
70.
Yude Ji Yanping Guo Yuejuan Liu Yun Tian 《International Journal of Adaptive Control and Signal Processing》2020,34(3):283-297
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results. 相似文献