全文获取类型
收费全文 | 20936篇 |
免费 | 2832篇 |
国内免费 | 994篇 |
专业分类
电工技术 | 408篇 |
综合类 | 1216篇 |
化学工业 | 7533篇 |
金属工艺 | 487篇 |
机械仪表 | 602篇 |
建筑科学 | 396篇 |
矿业工程 | 2945篇 |
能源动力 | 726篇 |
轻工业 | 1751篇 |
水利工程 | 194篇 |
石油天然气 | 1274篇 |
武器工业 | 151篇 |
无线电 | 1072篇 |
一般工业技术 | 2839篇 |
冶金工业 | 1528篇 |
原子能技术 | 564篇 |
自动化技术 | 1076篇 |
出版年
2024年 | 107篇 |
2023年 | 397篇 |
2022年 | 623篇 |
2021年 | 849篇 |
2020年 | 834篇 |
2019年 | 726篇 |
2018年 | 681篇 |
2017年 | 777篇 |
2016年 | 894篇 |
2015年 | 892篇 |
2014年 | 1324篇 |
2013年 | 1464篇 |
2012年 | 1733篇 |
2011年 | 1533篇 |
2010年 | 1130篇 |
2009年 | 1146篇 |
2008年 | 997篇 |
2007年 | 1166篇 |
2006年 | 1110篇 |
2005年 | 995篇 |
2004年 | 772篇 |
2003年 | 814篇 |
2002年 | 632篇 |
2001年 | 523篇 |
2000年 | 454篇 |
1999年 | 385篇 |
1998年 | 340篇 |
1997年 | 270篇 |
1996年 | 230篇 |
1995年 | 197篇 |
1994年 | 171篇 |
1993年 | 118篇 |
1992年 | 91篇 |
1991年 | 77篇 |
1990年 | 59篇 |
1989年 | 41篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1974年 | 3篇 |
1959年 | 3篇 |
1955年 | 1篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
某难选铅锌矿石浮选分离新工艺试验研究 总被引:2,自引:0,他引:2
针对某难选铅锌矿的矿石性质,进行了较为系统的小型试验研究。结果表明:在铅循环中采用Bx SN—9^#组合捕收剂、石灰 ZL—01组合抑制剂,在锌循环中采用捕收剂磁处理浮选技术等措施,可以较好地解决该难选矿的浮选分离问题。 相似文献
62.
陈仕文 《北京印刷学院学报》1993,(1)
本文根据人眼视觉特性、孟塞尔方程及彩色复制理论,并结合实际工艺路线和工艺条件,推导出标准阶调复制曲线和标准电分工作曲线。它与德国Hell公司所绘的电分标准工作曲线基本一致。并做到了各工序有数据,有质量标准,使平印制版做到有规可循。 相似文献
63.
64.
Phase separation during polymerization was studied in a model system consisting of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA), variable amounts of ethylenediamine (EDA) and the mass of castor oil (CO) necessary to obtain a mass fraction equal to 0-15 in a final system where the stoichiometric ratio of amine to epoxy equivalents, r, was equal to 1. A two-step polymerization process was performed by curing first a system with r = 0-5, during variable times before phase separation, and then carrying the system to r = 1. Thermodynamic analysis of samples with different r values led to a linear relationship between the Flory-Huggins interaction parameter and r. The concentration (P) and average size (D?) of dispersed-phase particles followed opposite trends, i.e. P increased while D? decreased, when either r was increased or the time of curing in the first step of a two-step process was decreased. This was explained by assuming that the competition between nucleation and growth was determined by the viscosity at the cloud point, ηcp. Low values of ηcp favoured growth over nucleation and led to fewer but larger particles. 相似文献
65.
66.
Xiang Lu S. Sundar Kumar Iyer Jin Lee Brian Doyle Zhineng Fan Paul K. Chu Chenming Hu Nathan W. Cheung 《Journal of Electronic Materials》1998,27(9):1059-1066
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII)
for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high
cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation
of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous
buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique
is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant
in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen
induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure
combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force
which is sufficient to overcome the silicon fracture resistance. 相似文献
67.
68.
In the absence of a bulk diffusion effect, it is shown for the first time that the impedance spectra for the chlorine evolution reaction on a rotating thin ring electrode comprise three consecutive semicircles in the capacitive half of the complex plane. The first (highest frequency) semicircle is due to the charge-transfer resistance for chloride discharge and the simultaneous chlorine adsorption coupled to the double-layer capacitance. The second semicircle (around 5 Hz) is due to the adsorption and desorption of a chlorine intermediate. The third (lowest frequency, around 0.5 Hz) semicircle is due to the relaxation of surface oxygen species. The impedance data allow the steps of the overall reaction to be examined individually. On a Pt surface the rate of chloride discharge and simultaneous chlorine adsorption (the admittance of the first semicircle) is first order with respect to chloride concentration and has a potential-dependence close to 58 mV/decade. The rate of the adsorption and desorption process (the admittance of the second semicircle) is second order with respect to chloride concentration, and has a potential dependence close to 30 mV/decade. The time constant for the adsorption/desorption processes is ca 20 ms, independent of electrode potential in the range studied. These features are consistent with a mechanism in which a faster discharge reaction (Cl− Clad + e) is followed by a slower surface combination reaction (2Clad → Cl2), but inconsistent with mechanisms in which ion + atom desorption is predominant, the initial chloride discharge is slow, or a unipositively charged chlorine species is involved. 相似文献
69.
70.
Learning a sequence of target locations when the sequence is uncorrelated with a sequence of responses and target location is not the response dimension (pure perceptual-based sequence learning) was examined. Using probabilistic sequences of target locations, the author shows that such learning can be implicit, is unaffected by distance between target locations, and is mostly limited to first-order transition probabilities. Moreover, the mechanism underlying learning affords processing of information at anticipated target locations and appears to be attention based. Implications for hypotheses of implicit sequence learning are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献