全文获取类型
收费全文 | 4236篇 |
免费 | 513篇 |
国内免费 | 161篇 |
专业分类
电工技术 | 37篇 |
综合类 | 217篇 |
化学工业 | 1416篇 |
金属工艺 | 266篇 |
机械仪表 | 50篇 |
建筑科学 | 76篇 |
矿业工程 | 619篇 |
能源动力 | 258篇 |
轻工业 | 128篇 |
水利工程 | 4篇 |
石油天然气 | 566篇 |
武器工业 | 3篇 |
无线电 | 193篇 |
一般工业技术 | 609篇 |
冶金工业 | 441篇 |
原子能技术 | 10篇 |
自动化技术 | 17篇 |
出版年
2024年 | 17篇 |
2023年 | 92篇 |
2022年 | 177篇 |
2021年 | 181篇 |
2020年 | 185篇 |
2019年 | 151篇 |
2018年 | 125篇 |
2017年 | 174篇 |
2016年 | 163篇 |
2015年 | 202篇 |
2014年 | 258篇 |
2013年 | 272篇 |
2012年 | 320篇 |
2011年 | 271篇 |
2010年 | 219篇 |
2009年 | 200篇 |
2008年 | 179篇 |
2007年 | 234篇 |
2006年 | 208篇 |
2005年 | 197篇 |
2004年 | 164篇 |
2003年 | 132篇 |
2002年 | 111篇 |
2001年 | 93篇 |
2000年 | 100篇 |
1999年 | 79篇 |
1998年 | 65篇 |
1997年 | 64篇 |
1996年 | 57篇 |
1995年 | 40篇 |
1994年 | 32篇 |
1993年 | 30篇 |
1992年 | 24篇 |
1991年 | 22篇 |
1990年 | 23篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有4910条查询结果,搜索用时 171 毫秒
61.
62.
主要介绍了几种聚芳硫醚类高性能树脂(聚苯硫醚、聚芳硫醚砜、聚芳硫醚酮、聚芳硫醚酰亚胺以及聚芳硫醚腈)的性能、研究动向以及产业化情况;并对今后聚芳硫醚类树脂的研究、发展趋势进行了预测。 相似文献
63.
Jiaqi Ren Gaoming Wu Zheng Xia Mingming Wang Jun Wei Bin Yang Yang Hou Lecheng Lei Di Wu Zhongjian Li 《American Institute of Chemical Engineers》2021,67(8):e17309
Low organic carbon-to-nitrogen ratio and existing sulfate (SO42−) in industrial wastewater limited nitrogen removal. Coupling SO42− reduction with sulfide autotrophic denitrification provides a novel strategy. Herein, bioelectrochemical sulfate reduction was coupled with heterotrophic sulfate reduction to drive sulfide autotrophic denitrification. In this coupled system, total nitrogen (TN) removal efficiency was increased from ~25% to ~85% by inputting −45 mA electricity. With the help of supplying electrons to denitrification through SO42− reduction, coulomb efficiency was improved to 61.5%. Also, bioelectrochemical sulfate reduction could improve sulfur recovery and thus increase TN removal efficiency. Furthermore, through tuning turnover numbers of SO42−, high TN removal efficiency can be obtained at various concentrations of SO42−. Moreover, main functional bacteria in this system were identified. Finally, ~75% TN removal efficiency was achieved with real wastewater in this system. Overall, this work offered a new approach for efficient nitrogen removal from industrial wastewater containing SO42−. 相似文献
64.
采用光电化学方法研究了模拟冷却水中硫离子对不锈钢钝化膜的破坏作用.结果表明,不锈钢钝化膜显示n-型光响应,最大吸收峰出现在310 nm处.不锈钢钝化膜在电位约-0.35 V开始出现光电流,随电位升高,光电流增大.钝化膜禁带宽度Eg随电位的升高而减小,并逐渐向铁氧化物的Eg靠近.模拟冷却水中加入硫离子使不锈钢钝化膜的光电流增大,Eg减小.硫离子的浓度越大,测得的光电流越大,而Eg越小,这可归因于钝化膜膜电阻的降低及钝化膜中氧化铬含量的减少. 相似文献
65.
The heap leaching of oxide copper ores with copper cathode recovery by solvent extraction and electrowinning is now well established as a low-cost method of copper recovery. This technology has recently been applied successfully to mixed oxide and chalcocite ores, notably in Chile at Cerro Colorado, Quebrada Blanca and Zaldivar.Currently, there are significant development efforts underway to try to extend heap leaching to chalcopyrite ores.The success of heap leaching/SX/EW has also led to a revival in the development of hydrometallurgical processes to recover copper from chalcopyrite and other copper concentrates. The current status of copper hydrometallurgy is reviewed and the most commercially attractive potential applications are explored. The advantages and disadvantages of the hydrometallurgical treatment of chalcopyrite concentrates and its preliminary economics are compared with those for the current best practices in copper smelting and refining. 相似文献
66.
The chemical composition, defect structure, and diffusion in nickel sulfide -Ni3S2 have been investigated in H2S-H2 mixtures containing between 1 and 65% H2S between 560 and 700°C. Gravimetric, density, and X-ray studies were carried out. In the thermodynamically stable compound the ratio of Ni/S varied between 1.3 and 1.75. The X-ray examination showed a step change in the lattice parameter at the Ni/S ratio 1.4. A linear dependence of the density values (between 5.5 and 6.2 g/cm3) on the composition was observed. On the basis of the chemical composition and density measurements the number of nickel and sulfur atoms in 1 cm3 were determined. It has been shown that the Ni3S2 phase is defected in both anion and cation sublattices and that its chemical formula may be described as follows: Ni3±yS2x, where y 2x. It has been found that in the mixture containing 10% H2S the process of defect formation is determined by their diffusion in the sulfide. The temperature dependence of the diffusion coefficient is described by the equation D = 13.15 exp(-30,000/RT) cm2/sec. No dependence of D on the sulfur partial pressure was observed, but this may be due to the relatively large uncertainties in the measurement of the diffusion coefficients. 相似文献
67.
68.
应用TGA、XRD、SEM/WDS技术研究了Fe50Mo合金在1kPa,700~900℃的硫蒸气中的高温硫化行为.发现在700℃时硫化遵从抛物线规律,800和900℃时则变为线性规律.Fe50Mo的硫化速度常数比纯Fe的低3~4个数量级,比Fe20Mo和Fe40Mo的抗硫化性能有了显著提高.热处理对合金硫化行为无显著影响.最初只出现FeS单一硫化产物层,合金中发生μ相晶界处α-Fe相的选择硫化.长时间硫化后,FeS层下出现MoS2内层,其晶体片层垂直于样品表面,有助于扩散传质.但MoS2层致密、微观缺陷少 相似文献
69.
70.