全文获取类型
收费全文 | 127503篇 |
免费 | 14488篇 |
国内免费 | 8353篇 |
专业分类
电工技术 | 10345篇 |
技术理论 | 3篇 |
综合类 | 12526篇 |
化学工业 | 16512篇 |
金属工艺 | 8007篇 |
机械仪表 | 8127篇 |
建筑科学 | 8726篇 |
矿业工程 | 5054篇 |
能源动力 | 3575篇 |
轻工业 | 12877篇 |
水利工程 | 3735篇 |
石油天然气 | 4522篇 |
武器工业 | 1851篇 |
无线电 | 12079篇 |
一般工业技术 | 11099篇 |
冶金工业 | 12626篇 |
原子能技术 | 1886篇 |
自动化技术 | 16794篇 |
出版年
2024年 | 368篇 |
2023年 | 2008篇 |
2022年 | 4467篇 |
2021年 | 5863篇 |
2020年 | 4299篇 |
2019年 | 3154篇 |
2018年 | 3441篇 |
2017年 | 3687篇 |
2016年 | 3457篇 |
2015年 | 5373篇 |
2014年 | 6638篇 |
2013年 | 8026篇 |
2012年 | 9675篇 |
2011年 | 9909篇 |
2010年 | 9510篇 |
2009年 | 8677篇 |
2008年 | 8764篇 |
2007年 | 8418篇 |
2006年 | 7472篇 |
2005年 | 5948篇 |
2004年 | 4458篇 |
2003年 | 3760篇 |
2002年 | 4009篇 |
2001年 | 3593篇 |
2000年 | 2542篇 |
1999年 | 1580篇 |
1998年 | 3268篇 |
1997年 | 2011篇 |
1996年 | 1369篇 |
1995年 | 924篇 |
1994年 | 757篇 |
1993年 | 718篇 |
1992年 | 275篇 |
1991年 | 256篇 |
1990年 | 209篇 |
1989年 | 190篇 |
1988年 | 151篇 |
1987年 | 115篇 |
1986年 | 102篇 |
1985年 | 74篇 |
1983年 | 21篇 |
1982年 | 54篇 |
1981年 | 50篇 |
1980年 | 95篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 164篇 |
1976年 | 287篇 |
1959年 | 40篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
1.
Fiber production from inorganic industrial solid wastes is an effective waste management strategy. Because of cost considerations, most enterprises generally use local solid wastes as raw materials to produce fibers. In this study, we explored the feasibility of producing fibers using fly ash and magnesium slag. The results show that the melting temperature of the blends composed of fly ash, magnesium slag, and a small amount of calcined dolomite first decreased and then increased with an increase in acidity coefficient (Mk) from 1.0 to 2.4. The samples could form a eutectic system in the Mk range of 1.4–1.8, and therefore have a relatively low melting temperature in this Mk range. Fly ash could react with magnesium slag and calcined dolomite to form akermanite, gehlenite-magnesium, and anorthite at temperatures close to the melting temperature; therefore, these crystalline phases were the main reaction products formed in the samples with Mk values lower than 1.80. Anorthite reacted further with some Na-containing and Si-containing spieces to produce labradorite. Thus, the content of anorthite and labradorite rapidly increased and they became the major crystal phases in the blend samples with Mk values greater than 1.80. MAS-NMR spectroscopic analysis revealed that the network structure of the melts depended on the ratio of bridging oxygen to non-bridging oxygen; a high ratio of bridging oxygen to non-bridging oxygen could lead to the formation of a dense network structure in the melt. The blends of fly ash and magnesium slag can be used to produce wool fibers and continuous fibers. In addition, the suitable temperature ranges for the production of both types of fibers were determined. The drawing temperature for continuous fiber production depended on the degree of polymerization and structure of the melt. 相似文献
2.
3.
For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Cu metallic glasses were prepared by copper mold injection methods. In the present work, the effect of Cu doping on mechanical properties, corrosion behavior, and glass-forming ability of Mg66Zn30Ca4 alloy was studied. The experimental findings demonstrated that the incorporation of Cu decreases the corrosion resistance of alloys, but increases the microhardness and degradation rate slightly. However, the addition of a trace amount of Cu can make the samples have antibacterial properties. Therefore, Mg–Zn–Ca–Cu has great advantages in clinical implantation and is the potential implant material. 相似文献
4.
5.
采用溶胶-凝胶法制备CuO-SiO2复合气凝胶,通过在气凝胶孔道内填充TiCl4,然后将其气相水解,得到了在CuO-SiO2气凝胶表面生长了高结晶度的TiO2纳米纤维(CuO-SiO2@TiO2),纤维直径~16 nm.通过XPS、UPS、UV-Vis DRS、荧光光谱(PL)等表征了材料的结构及光电性能.结果表明,制备的CuO-SiO2@TiO2对可见光有明显吸收,且荧光强度较商用TiO2(P25)大幅降低,光生电子-空穴对更加稳定.再在纳米纤维上负载CuO,所得CuO-SiO2@TiO2/CuO在可见光区的荧光强度进一步增强.以300 W氙灯为光源,分别以CuO-SiO2@TiO2及CuO-SiO2@TiO2/CuO为催化剂,无牺牲剂条件下光催化还原CO2,4 h后甲醇产率分别为1304.0及1589.0μmol/g-cat,转换频率(TOF)分别为0.038及0.046 h–1.循环实验表明,纳米纤维具有较好的光催化稳定性,经过4次光催化循环实验后,CuO-SiO2@TiO2/CuO的保留率~94%,甲醇产率可达1472.0μmol/g-cat,TOF为0.042 h–1. 相似文献
6.
7.
针对动态非刚性在线重建存在的重建漂移问题,提出了一种基于单个RGB-D传感器的稠密变形场在线融合策略,实现了对非刚性几何形状的动态重建.通过局部平滑和输入约束处理,将空间的最优变形转换为非线性正则变分优化问题,并使用数据并行闪存优化策略,以摄像机捕获速率,实现对非刚性场景的在线跟踪重建.通过实验表明,本文方法实现了对非刚性场景的鲁棒跟踪,减少了在线重建过程中的漂移现象,适用于快速运动和缺乏几何特征的场景重建. 相似文献
8.
在公交时间表下给定起始和目标站点,路径规划查询返回一组到达时间早和换乘次数少的帕雷托最优路径.现有的索引方法需要大量运行时内存.本文提出主存空间高效的索引方法(a-)PAINT.(a-)PAINT对每个站点v预计算一组标签,使得对于从站点s到站点d的查询可以通过匹配s和d相关的标签高效地生成查询结果的一条路径.PAINT对任意查询返回最优路径.a-PAINT只需要很小的预处理开销,但可能返回多一趟换乘的次优路径.用真实的公交时间表与模拟查询测试,PAINT具有合理的预处理开销.a-PAINT需要更少量的预处理开销,在大规模公交网络下准确率达90%. 相似文献
9.
10.
Fanbo Meng Mingchang Zhang Jin Huang Wen Feng Lu Jun Min Xue Hao Wang 《Advanced functional materials》2021,31(9):2008280
The development of the Internet of things has prompted an exponential increase in the demand for flexible, wearable devices, thereby posing new challenges to their integration and conformalization. Additive manufacturing facilitates the fabrication of complex parts via a single integrated process. Herein, the development of a multinozzle, multimaterial printing device is reported. This device accommodates the various characteristics of printing materials, ensures high-capacity printing, and can accommodate a wide range of material viscosities from 0 to 1000 Cp. Complete capacitors, inclusive of the current collector, electrode, and electrolyte, can be printed without repeated clamping to complete the preheating, printing, and sintering processes. This method addresses the poor stability issue associated with printed electrode materials. Furthermore, after the intercalation of LiFePO4 with Na ions, X-ray photoelectron spectroscopy and X-ray diffraction results reveal that the Na ions permeate the interlayer structure of LiFePO4, enhancing the ion migration channels by increasing the ion transmission rate. A current rate of 2.5 mAh ensures >2000 charge/discharge cycles, while retaining a charge/discharge efficiency of 96% and a discharge capacity of 91.3 mAh g−1. This manufacturing process can provide conformal power modules for a diverse range of portable devices with various shapes, improving space utilization. 相似文献