全文获取类型
收费全文 | 196461篇 |
免费 | 17657篇 |
国内免费 | 9484篇 |
专业分类
电工技术 | 12401篇 |
技术理论 | 15篇 |
综合类 | 15297篇 |
化学工业 | 30990篇 |
金属工艺 | 11812篇 |
机械仪表 | 13287篇 |
建筑科学 | 15736篇 |
矿业工程 | 6021篇 |
能源动力 | 5625篇 |
轻工业 | 16233篇 |
水利工程 | 3696篇 |
石油天然气 | 12099篇 |
武器工业 | 1803篇 |
无线电 | 21050篇 |
一般工业技术 | 21416篇 |
冶金工业 | 8383篇 |
原子能技术 | 2091篇 |
自动化技术 | 25647篇 |
出版年
2024年 | 417篇 |
2023年 | 3119篇 |
2022年 | 5462篇 |
2021年 | 8129篇 |
2020年 | 6382篇 |
2019年 | 5048篇 |
2018年 | 5527篇 |
2017年 | 6346篇 |
2016年 | 5703篇 |
2015年 | 8204篇 |
2014年 | 10253篇 |
2013年 | 11961篇 |
2012年 | 13629篇 |
2011年 | 14765篇 |
2010年 | 13031篇 |
2009年 | 12392篇 |
2008年 | 12230篇 |
2007年 | 11514篇 |
2006年 | 11489篇 |
2005年 | 9547篇 |
2004年 | 6453篇 |
2003年 | 5754篇 |
2002年 | 5632篇 |
2001年 | 4911篇 |
2000年 | 4356篇 |
1999年 | 4355篇 |
1998年 | 3302篇 |
1997年 | 2678篇 |
1996年 | 2530篇 |
1995年 | 2041篇 |
1994年 | 1680篇 |
1993年 | 1104篇 |
1992年 | 950篇 |
1991年 | 669篇 |
1990年 | 502篇 |
1989年 | 431篇 |
1988年 | 306篇 |
1987年 | 207篇 |
1986年 | 164篇 |
1985年 | 92篇 |
1984年 | 60篇 |
1983年 | 61篇 |
1982年 | 61篇 |
1981年 | 48篇 |
1980年 | 53篇 |
1979年 | 25篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 10篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
A new aqueous slurry-based laminated object manufacturing process for porous ceramics is proposed: firstly, an organic mesh sheet is pre-paved as a pore-forming template before slurry layer scraping; secondly, the 2D pattern is built with laser outline cutting of the dried mesh–ceramic composite layer; finally, the pore structure is formed after degreasing and sintering. Alumina parts with porosities of 51.5 %, round hole diameters of 80 ± 5 μm were fabricated using 70 wt. % solid content slurry and 100 mesh nylon net. Using an organic mesh as the framework and template not only reduces the risk of damage of the green body but also ensures the regularity, uniformity and connectivity of the micron scaled pore network. The layer-by-layer drying method avoids the delamination phenomenon and improves the paving density. The new method can realize the flexible design of the pore structure by using various organic mesh templates. 相似文献
2.
我公司1#生产线的窑头使用布袋收尘器,型号:HMMC391-4×4,处理风量:1 350 000 m3/h,过滤风速<0.9 m/min,收尘器风室4 排×4 列。投入使用3个月后停机检查,发现第一排4 个风室的滤袋较多底部被磨穿,主要集中在灰斗四周的前3 环区域,前两排风室其他位置的滤袋也较多出现异常磨损,但后
两排风室的滤袋却完好无损。 相似文献
3.
Kun Yang Yachun Wang Penghui Lei Tiankai Yao Dong Zhao Jie Lian 《Journal of the European Ceramic Society》2021,41(12):6018-6028
Chemical durability of lanthanide zirconates (A2Zr2O7) (A = La-Yb) under near-field environments is important for evaluating their application as potential nuclear waste forms. In this work, A2Zr2O7 (A = La-Yb) are synthesized by spark plasma sintering with controlled microstructure and their chemical durability are evaluated in a nitric acid solution (pH = 1). Scanning transmission electron microscopy analysis reveals an amorphous passivation film either enriched with Zr or lanthanide. The complex chemistry of the passivation films can be correlated with a transition in corrosion mechanisms from a preferential release of lanthanide in La2Zr2O7 to a preferential release of Zr in Er2Zr2O7 and Yb2Zr2O7. These results suggest a dominant mechanism of incongruent dissolution and surface reorganization for the formation of passivation films. Strong correlations are identified between the leaching rates and cation ionic size, ionic potential, electronegativity differences between A-site cation and Zr, and bonding valence sum of oxygen, suggesting important impacts of structural and bonding characteristics in controlling chemical durability of lanthanide zirconates. 相似文献
4.
利用蒸馏分离—气相色谱法技术,建立了同时测定煤焦油中苊、氧芴和芴的分析方法。通过对色谱条件的优化,以甲苯为溶剂,正十二烷为内标物,将煤焦油馏分采用DB-5毛细管柱,对煤焦油中苊、氧芴和芴定量分析。分析结果表明:3种主要成分线性关系良好,相关系数均大于0.9995,加标回收率为95.4%~102.4%,相对标准偏差为2.89%~7.14%。该方法分离效果好,检测结果准确、可靠。 相似文献
5.
6.
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will... 相似文献
7.
In this study, chemically bonded phosphate ceramic coatings (CBPCCs) with different contents of aluminum phosphate (AP) are prepared on stainless steel (AISI 304L). Differential scanning calorimetry, X-ray diffraction, contact angle test, and a tribocorrosion experiment are carried out to clarify the role of AP in the tribocorrosion performance of CBPCCs. The results show that, with the increase in the AP content, the enthalpy of curing increases because of the greater formation of the bonding phase AlPO4. Both in static corrosion and in tribocorrosion, the corrosion current density of CBPCCs achieves the lowest value when the weight ratio of AP to polytetrafluoroethylene is about 0.78. Additionally, the influence mechanism of AP on tribocorrosion is clarified. AlPO4 from the reaction between AP and Al2O3 has excellent mechanical properties and can enhance the wear resistance of CBPCCs by reducing the mechanical wear and the increased wear due to corrosion. The alumina particles wrapped by AlPO4 can form a dense and smooth surface and change the direction of electrolyte propagation, which leads to the increase in the tribocorrosion resistance of CBPCCs. 相似文献
8.
Han Chen Shunzo Shimai Jin Zhao Xiaojian Mao Jian Zhang Guohong Zhou Shiwei Wang 《Journal of the European Ceramic Society》2021,41(6):3838-3843
Alumina platelets were arranged horizontally in submicron alumina particles by shear force in the flow of slurries during casting. The obtained alumina green bodies with platelets were pressureless-sintered in vacuum, producing ceramics with thoroughly oriented grains and high transmittance. The effects of sintering parameters on the densification, microstructure evolution, and orientation degree of alumina ceramics were investigated and discussed. The results showed that the densification, grain size, orientation degree, and in-line transmittance were increased with increasing sintering temperature. The enhancement of orientation degree was mainly coherent with grain growth. The grain-oriented samples exhibited a much higher in-line transmittance (at 600 nm) of 61 % than that of the grain random sample (29 %). Moreover, the transmission remained a high level in the ultraviolet range (<300 nm). 相似文献
9.
10.
Yi Qin Tao Xiong Ting Zhao Jianfeng Zhu Jun Yang Yi Liu Xingang Kong Xiaohan Li 《Ceramics International》2021,47(9):12641-12650
The strengthening method of multi-element M-site solid solution is a common approach to improve mechanical properties of MAX phase ceramic. However, the research on capability of multi-element A-site solid solution to improve mechanical properties has rarely been reported. Thereupon, quasi-high-entropy MAX phase ceramic bulks of Ti2(Al1?xAx)C and Ti3(Al1?xAx)C2 (A = Ga, In, Sn, x = 0.2, 0.3, 0.4) were successfully synthesized by in situ vacuum hot pressing via multi-elements solid solution. The multi-elements solid solution in single-atom thick A layer was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy as well as by energy dispersive X-ray spectroscopy mappings. Effects of doped multi-elements contents on the phase, microstructure, mechanical properties, and high temperature tribological behaviors were studied. Results demonstrated that the Vickers hardness, anisotropic flexural strength, fracture toughness, and tribological properties of Ti–Al–C based MAX ceramics could be remarkably improved by constitution of quasi-high-entropy MAX phase in A layers. Moreover, the strengthening and wear mechanisms were also discussed in detail. This method of multi-element solid solution at A-site provides new way to enhance mechanical properties of other MAX phase ceramics. 相似文献