全文获取类型
收费全文 | 43999篇 |
免费 | 4512篇 |
国内免费 | 2722篇 |
专业分类
电工技术 | 3146篇 |
综合类 | 3227篇 |
化学工业 | 6462篇 |
金属工艺 | 2908篇 |
机械仪表 | 2940篇 |
建筑科学 | 3546篇 |
矿业工程 | 1414篇 |
能源动力 | 1142篇 |
轻工业 | 3846篇 |
水利工程 | 926篇 |
石油天然气 | 2432篇 |
武器工业 | 500篇 |
无线电 | 5343篇 |
一般工业技术 | 4766篇 |
冶金工业 | 1820篇 |
原子能技术 | 493篇 |
自动化技术 | 6322篇 |
出版年
2024年 | 232篇 |
2023年 | 809篇 |
2022年 | 1537篇 |
2021年 | 2105篇 |
2020年 | 1579篇 |
2019年 | 1256篇 |
2018年 | 1335篇 |
2017年 | 1525篇 |
2016年 | 1312篇 |
2015年 | 1933篇 |
2014年 | 2411篇 |
2013年 | 2668篇 |
2012年 | 3242篇 |
2011年 | 3327篇 |
2010年 | 3077篇 |
2009年 | 2912篇 |
2008年 | 2738篇 |
2007年 | 2698篇 |
2006年 | 2609篇 |
2005年 | 2253篇 |
2004年 | 1511篇 |
2003年 | 1214篇 |
2002年 | 1166篇 |
2001年 | 947篇 |
2000年 | 928篇 |
1999年 | 817篇 |
1998年 | 585篇 |
1997年 | 557篇 |
1996年 | 447篇 |
1995年 | 370篇 |
1994年 | 297篇 |
1993年 | 187篇 |
1992年 | 152篇 |
1991年 | 105篇 |
1990年 | 100篇 |
1989年 | 89篇 |
1988年 | 62篇 |
1987年 | 35篇 |
1986年 | 24篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1959年 | 8篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
11.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献
12.
Weigang Liang Beibei Wang Guofeng Shen Suzhen Cao Bertrand Mcswain Ning Qin Liyun Zhao Dongmei Yu Jicheng Gong Shanshan Zhao Yawei Zhang Xiaoli Duan 《Indoor air》2020,30(2):264-274
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel. 相似文献
13.
14.
15.
16.
Yan Xiong Xianwu Du Mingyu Xiang Hao Wang Weimin Wang Zhengyi Fu 《Journal of the European Ceramic Society》2018,38(12):4167-4172
The densification behaviors of pure B4C and B4C-ZrO2 mixtures were compared during hot pressing. The results showed that in-situ formed ZrB2 effectively enhanced the densification process of B4C-ZrO2 mixtures, more significantly during the intermediate stage. Within the relative density ranging from 0.75 to 0.90, the B4C-15?wt%ZrO2 mixture (B15Z) achieved the maximum densification rate as twice much as that of pure B4C. The stress exponent n>3 indicated plastic deformation was the dominant densification mechanism of B15Z. The viscosities of plastic flow were evaluated using Murray-Rodger-William equation and the viscosity of B15Z was only a quarter of that in pure B4C. The sintering activation energy was calculated to be 305.9?kJ/mol for pure B4C and 197?kJ/mol for B15Z, respectively. It was proposed that the lower viscosity of plastic flow and activation energy accelerated the sliding and propagating motions of plastic flow, by which underlain the enhanced densification behaviors of B4C-ZrO2 mixtures. 相似文献
17.
18.
19.
在国家政策和市场需求的双重推动下,BIM技术在国内建筑领域迎来快速发展阶段,从最初的概念普及,到能够局部应用,再到现在能够全过程应用,其趋势是十分明确的,但是在其发展的过程中仍然存在着不少问题,如传统技术与BIM技术深入融合问题,BIM技术如何解决工程施工现场实际问题等.本文主要研究BIM技术在连云港民用机场迁建工程旅客过夜用房酒店项目中的综合应用,从协同建模、碰撞检查、管线综合、施工图深化出图及漫游展示等方面着手,着重解决BIM技术在施工过程中应用的落地问题,从而达到提高效率,缩短工期,降低成本,提升质量的目标. 相似文献
20.
针对流体输送埋地管道泄漏问题,设计了一种利用管道机器人携带封堵气囊进行快速应急封堵修复的埋地管道泄漏内封堵装置。采用矩阵变换方法建立了牵引系统驱动轮过弯方程,利用MATLAB软件对过弯方程进行了验证,同时利用ADAMS软件仿真分析过弯路径与驱动轮转角对牵引系统行走速度的影响。研究结果表明:由两个串联封堵器组成的应急封堵系统可满足复杂工况下的管道泄漏封堵要求;牵引系统驱动轮在弯管内部行走时,单轮速度呈周期性变化,但三个驱动轮整体周期运动特性一致;驱动轮转角在25°~40°时,牵引系统行走速度与驱动轮转角成正比,且转角为30°时驱动效果最好。该内封堵装置的结构设计可为管道泄漏应急封堵领域装备的研发提供重要参考。 相似文献