全文获取类型
收费全文 | 104203篇 |
免费 | 10656篇 |
国内免费 | 5935篇 |
专业分类
电工技术 | 7788篇 |
技术理论 | 4篇 |
综合类 | 7793篇 |
化学工业 | 15901篇 |
金属工艺 | 5658篇 |
机械仪表 | 6737篇 |
建筑科学 | 9012篇 |
矿业工程 | 3199篇 |
能源动力 | 3010篇 |
轻工业 | 7267篇 |
水利工程 | 2337篇 |
石油天然气 | 5230篇 |
武器工业 | 1311篇 |
无线电 | 12619篇 |
一般工业技术 | 11118篇 |
冶金工业 | 4880篇 |
原子能技术 | 1381篇 |
自动化技术 | 15549篇 |
出版年
2024年 | 558篇 |
2023年 | 1760篇 |
2022年 | 3566篇 |
2021年 | 4857篇 |
2020年 | 3571篇 |
2019年 | 2798篇 |
2018年 | 3106篇 |
2017年 | 3530篇 |
2016年 | 3143篇 |
2015年 | 4517篇 |
2014年 | 5572篇 |
2013年 | 6714篇 |
2012年 | 7717篇 |
2011年 | 8074篇 |
2010年 | 7136篇 |
2009年 | 6876篇 |
2008年 | 6712篇 |
2007年 | 6160篇 |
2006年 | 5884篇 |
2005年 | 5095篇 |
2004年 | 3430篇 |
2003年 | 2570篇 |
2002年 | 2517篇 |
2001年 | 2154篇 |
2000年 | 2063篇 |
1999年 | 1890篇 |
1998年 | 1511篇 |
1997年 | 1291篇 |
1996年 | 1234篇 |
1995年 | 1026篇 |
1994年 | 776篇 |
1993年 | 677篇 |
1992年 | 510篇 |
1991年 | 354篇 |
1990年 | 335篇 |
1989年 | 234篇 |
1988年 | 204篇 |
1987年 | 139篇 |
1986年 | 114篇 |
1985年 | 75篇 |
1984年 | 61篇 |
1983年 | 43篇 |
1982年 | 45篇 |
1981年 | 35篇 |
1980年 | 35篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Kelin Hu Feipeng Wang Yuyang Yan Hongcheng Liu Zijia Shen 《Ceramics International》2021,47(11):15228-15236
In this paper, a novel hybrid structure of Pd doped ZnO/SnO2 heterojunction nanofibers with hexagonal ZnO columns was one step synthesized from electrospun precursor nanofibers. Due to the synergistic effect of hexagonal ZnO, SnO2 and Pd, the structure exhibited excellent hydrogen (H2) gas sensing properties. At low-temperature of 120 °C, the response (Ra/Rg) to 100 ppm H2 gas exceeded 160, the response/recovery time was only 20 s and 6 s respectively and the limit of detection was only 0.5 ppm. Meanwhile, it also had good selectivity for H2 gas and excellent linearity. In addition, the materials were characterized by XRD, FESEM, HRTEM, XPS, and the synthesis mechanism and gas sensing mechanism were proposed. 相似文献
2.
3.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
4.
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
5.
Tao Feng Mingde Tong Shuotian Yao Hejun Li Shifeng Wen Hongjiao Lin 《Journal of the European Ceramic Society》2021,41(1):158-166
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. 相似文献
6.
7.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
8.