全文获取类型
收费全文 | 8564篇 |
免费 | 564篇 |
国内免费 | 55篇 |
专业分类
电工技术 | 133篇 |
综合类 | 7篇 |
化学工业 | 1743篇 |
金属工艺 | 327篇 |
机械仪表 | 586篇 |
建筑科学 | 165篇 |
矿业工程 | 1篇 |
能源动力 | 371篇 |
轻工业 | 644篇 |
水利工程 | 30篇 |
石油天然气 | 13篇 |
武器工业 | 1篇 |
无线电 | 1750篇 |
一般工业技术 | 1827篇 |
冶金工业 | 623篇 |
原子能技术 | 149篇 |
自动化技术 | 813篇 |
出版年
2024年 | 7篇 |
2023年 | 109篇 |
2022年 | 112篇 |
2021年 | 281篇 |
2020年 | 216篇 |
2019年 | 181篇 |
2018年 | 246篇 |
2017年 | 271篇 |
2016年 | 318篇 |
2015年 | 227篇 |
2014年 | 337篇 |
2013年 | 543篇 |
2012年 | 556篇 |
2011年 | 671篇 |
2010年 | 486篇 |
2009年 | 501篇 |
2008年 | 470篇 |
2007年 | 370篇 |
2006年 | 331篇 |
2005年 | 306篇 |
2004年 | 277篇 |
2003年 | 239篇 |
2002年 | 252篇 |
2001年 | 212篇 |
2000年 | 206篇 |
1999年 | 198篇 |
1998年 | 310篇 |
1997年 | 183篇 |
1996年 | 140篇 |
1995年 | 94篇 |
1994年 | 99篇 |
1993年 | 80篇 |
1992年 | 44篇 |
1991年 | 55篇 |
1990年 | 38篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 29篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 5篇 |
排序方式: 共有9183条查询结果,搜索用时 789 毫秒
131.
Electrophoretic deposition of carbon nanotubes 总被引:1,自引:0,他引:1
Aldo R. Boccaccini Johann Cho Judith A. Roether Boris J.C. Thomas E. Jane Minay Milo S.P. Shaffer 《Carbon》2006,44(15):3149-3160
Electrophoretic deposition (EPD) has been gaining increasing interest as an economical and versatile processing technique for the production of novel coatings or films of carbon nanotubes (CNTs) on conductive substrates. The purpose of the paper is to present an up-to-date comprehensive overview of current research progress in the field of EPD of CNTs. The paper specifically reviews the preparation and characterisation of stable CNT suspensions, and the mechanism of the EPD process; it includes discussion of pure CNT coatings and CNT/nanoparticle composite films. A complete discussion of the EPD parameters is presented, including electrode materials, deposition time, electrode separation, deposition voltage and resultant electric field. The paper highlights potential applications of the resulting CNT and CNT/composite structures, in areas such as field emission devices, fuel cells, and supercapacitors. 相似文献
132.
A heating process for obtaining free-standing carbon nanotube emitters is presented with the aim of improving field-emission properties from the screen-printed multiwalled carbon nanotube (MWCNT) films. Using an atmosphere with an optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for a high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides a high reproducibility in emission current density which makes the films suitable for practical applications. 相似文献
133.
Jeong-Ho Cho In-Kil Park Ho-Gi Kim Hoon-Taek Chung 《Journal of the American Ceramic Society》1997,80(6):1523-1534
Substituting Cd2+ ions into the A and B sites in a Pb(Ni1/3 Nb2/3 )O3 PbZrO3 PbTiO3 (PNNPZPT) ternary perovskite material made it possible to determine the effects of the Cd2+ ion substitution site on sintering behavior. The substitution site of the Cd2+ ion was identified by using X-ray photoelectron spectroscopy spectra. Although Cd2+ ions were substituted into the A and B sites in PNNPZPT, the Cd2+ ions preferred the A site over the B site. When Cd2+ ions replaced Pb2+ ions, a weight gain was observed during sintering. On the other hand, replacing Ni2 ions with Cd2+ ions promoted weight loss. Those weight changes indicated that Cd2+ ions change the bonding strength between the B-site cations and the oxygen of the octahedron in a perovskite structure. Density was influenced by the Cd2+ ion substitution site, and the A-site-doped compositions had higher densities than the B-site-doped compositions. 相似文献
134.
Typical high dynamic range (HDR) imaging approaches based on multiple images have difficulties in handling moving objects and camera shakes, suffering from the ghosting effect and the loss of sharpness in the output HDR image. While there exist a variety of solutions for resolving such limitations, most of the existing algorithms are susceptible to complex motions, saturation, and occlusions. In this paper, we propose an HDR imaging approach using the coded electronic shutter which can capture a scene with row‐wise varying exposures in a single image. Our approach enables a direct extension of the dynamic range of the captured image without using multiple images, by photometrically calibrating rows with different exposures. Due to the concurrent capture of multiple exposures, misalignments of moving objects are naturally avoided with significant reduction in the ghosting effect. To handle the issues with under‐/over‐exposure, noise, and blurs, we present a coherent HDR imaging process where the problems are resolved one by one at each step. Experimental results with real photographs, captured using a coded electronic shutter, demonstrate that our method produces a high quality HDR images without the ghosting and blur artifacts. 相似文献
135.
Chang?Duk?Kang Sang?Jun?SimEmail author Young?Sang?Cho Woo?Sik?Kim 《Korean Journal of Chemical Engineering》2003,20(3):482-486
The removal of copper from wastewater by ferric/limestone coagulation followed by screen filtration was carried out at a laboratory
scale. The optimum coagulant (FeCl3) dose and working pH were 50 mg// of Fe(m) and pH 7.5, respectively, through jar tests. For the efficient removal of copper
from wastewater, we developed a novel process including the co-precipitation of copper with FeCl3, alkalization in a limestone aeration bed, and separation of precipitates in a sedimentation tank coupled with internal stainless
steel screen filter. The performance results showed that removal of copper from the solution was over 99.5%. The pH was effectively
maintained over 7.5 in limestone bed during the whole process. Ferric hydroxide/copper aggregates were removed over 99% by
stainless steel screen filter of 1,450 mesh. Periodic air backwashing alleviated fouling of the filter surface. 相似文献
136.
George Ting-Kuo Fey P. Muralidharan Cheng-Zhang Lu Yung-Da Cho 《Electrochimica acta》2006,51(23):4850-4858
An enhanced electrochemical performance LiCoO2 cathode was synthesized by coating with various wt.% of La2O3 to the LiCoO2 particle surfaces by a polymeric method, followed by calcination at 923 K for 4 h in air. The surface-coated materials were characterized by XRD, TGA, SEM, TEM, BET and XPS/ESCA techniques. XRD patterns of La2O3-coated LiCoO2 revealed that the coating did not affect the crystal structure, α-NaFeO2, of the cathode material compared to pristine LiCoO2. TEM images showed a compact coating layer on the surface of the core material that had an average thickness of about ∼15 nm. XPS data illustrated that the presence of two different environmental O 1s ions corresponds to the surface-coated La2O3 and core material. The electrochemical performance of the coated materials by galvanostatic cycling studies suggest that 2.0 wt.% coated La2O3 on LiCoO2 improved cycle stability (284 cycles) by a factor of ∼7 times over the pristine LiCoO2 cathode material and also demonstrated excellent cell cycle stability when charged at high voltages (4.4, 4.5 and 4.6 V). Impedance spectroscopy demonstrated that the enhanced performance of the coated materials is attributed to slower impedance growth during the charge-discharge processes. The DSC curve revealed that the exothermic peak corresponding to the release of oxygen at ∼464 K was significantly smaller for the La2O3-coated cathode material and recognized its high thermal stability. 相似文献
137.
Summary The cyclopolymerization of 1,8-diethynylnaphthalene(DEN) and its copolymerization with diethyl dipropargylmalonate(DEDPM) were carried out by various transition metal catalysts. MoCl5-based catalyst was found to be very effective and gave almost a quantitative polymer yield. The resulting dark-brown homopolymer(PDEN) was partially soluble in chloroform, tetrahydrofuran, and dimethyl sulfoxide, whereas copolymer (1:1) with number avaerage molecular weight
of 2.1x104 by GPC showed good solubility in those solvents. The structure of the polymers was analysed by IR, NMR, and UV-VIS spectroscopies. From the spectral and solubility data, it is proposed that cyclized products with the conjugated system are formed. Room temperature conductivities of the I2-doped homo and copolymer were found to be about 7.5x10-3 and 5.1x10-3 S/cm, respectively. 相似文献
138.
Sung-Yong Cho Seung-Shik Park Seung-Jai Kim Tae-Young Kim 《Korean Journal of Chemical Engineering》2006,23(4):638-644
Adsorption and desorption characteristics of the 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution onto the
activated carbon (GAC, F-400) were studied. Adsorption equilibrium capacities of the MCPA increased with decreasing pH and
temperature of the solution. Adsorption equilibrium of the MCPA could be represented by the Sips equation. The internal diffusion
coefficients were determined by comparing the experimental concentration decay curves with those predicted from surface diffusion
model and pore diffusion model. The adsorption model based on the linear driving force approximation (LDFA) was used for simulating
the adsorption behavior of the MCPA in a fixed bed. Over ninety five percent desorption of the MCPA could be obtained using
distilled water. 相似文献
139.
140.
Seong-Youl Bae Du-Hyon Cho Hee-Taik Kim Hidehiro Kumazawa 《Korean Journal of Chemical Engineering》1994,11(2):127-130
Sorption equilibria and permeation rates for oxygen and carbon dioxide in polycarbonate membrane were measured at different
temperature between 30 and 60°C and at pressures up to 2.5 MPa. The pressure dependence of mean permeability coefficient to
oxygen obeyed the conventional dual-mode mobility model, whereas that to carbon dioxide followed a modified dual-mode mobility
model with concentration-dependent diffusivities, as that of polystyrene to the same gas did. 相似文献