全文获取类型
收费全文 | 21833篇 |
免费 | 1419篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 402篇 |
综合类 | 72篇 |
化学工业 | 4741篇 |
金属工艺 | 704篇 |
机械仪表 | 520篇 |
建筑科学 | 1003篇 |
矿业工程 | 137篇 |
能源动力 | 344篇 |
轻工业 | 3049篇 |
水利工程 | 164篇 |
石油天然气 | 28篇 |
无线电 | 1359篇 |
一般工业技术 | 5618篇 |
冶金工业 | 1603篇 |
原子能技术 | 177篇 |
自动化技术 | 3348篇 |
出版年
2023年 | 273篇 |
2022年 | 179篇 |
2021年 | 467篇 |
2020年 | 398篇 |
2019年 | 365篇 |
2018年 | 736篇 |
2017年 | 723篇 |
2016年 | 824篇 |
2015年 | 693篇 |
2014年 | 831篇 |
2013年 | 1647篇 |
2012年 | 1078篇 |
2011年 | 1275篇 |
2010年 | 1063篇 |
2009年 | 943篇 |
2008年 | 1112篇 |
2007年 | 1051篇 |
2006年 | 753篇 |
2005年 | 594篇 |
2004年 | 512篇 |
2003年 | 510篇 |
2002年 | 512篇 |
2001年 | 422篇 |
2000年 | 360篇 |
1999年 | 307篇 |
1998年 | 549篇 |
1997年 | 390篇 |
1996年 | 341篇 |
1995年 | 271篇 |
1994年 | 235篇 |
1993年 | 198篇 |
1992年 | 155篇 |
1991年 | 138篇 |
1990年 | 120篇 |
1989年 | 124篇 |
1988年 | 101篇 |
1987年 | 110篇 |
1986年 | 92篇 |
1985年 | 195篇 |
1984年 | 191篇 |
1983年 | 142篇 |
1982年 | 136篇 |
1981年 | 145篇 |
1980年 | 129篇 |
1979年 | 111篇 |
1978年 | 105篇 |
1977年 | 108篇 |
1976年 | 149篇 |
1975年 | 99篇 |
1973年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The cost of lime/limestone for neutralisation is the second largest operating cost in bioleaching. Therefore, these studies have been conducted with the aim to investigate the possibilities for use of by-products such as mesalime and electric arc furnace (EAF) dust for neutralisation during biooxidation of a refractory gold concentrate. Experiments were carried out using a retention time of 57 h in a one-stage reactor and the influence of two industrial by-products on the biooxidation performance was evaluated. The neutralising capacity of EAF dust was lower, while the mesalime was similar to the Ca(OH)2 reference. The arsenopyrite oxidation in experiments ranged from 85% to 90%, whereas the pyrite oxidation was 63–74%. In subsequent cyanidation, final gold recoveries of 90% were achieved in bioresidues from mesalime and Ca(OH)2, while the EAF dust bioresidue had a recovery of 85%. A comparatively high elemental sulphur content in EAF dust probably encapsulates part of the gold, which explains the lower recovery for the EAF dust bioresidue despite a longer residence time. Cyanide consumption was relatively high and ranged from 8.1 to 9.2 kg/ton feed after 24 h of cyanidation. Overall, the by-products tested here have proved to be feasible options as neutralising agents in bioleaching operations. 相似文献
992.
993.
Hisashi Kaga Ellen M. Heian Zuhair A. Munir Clemens Schmalzried Rainer Telle 《Journal of the American Ceramic Society》2001,84(12):2764-2770
The synthesis of solid solutions of (Ti,W,Cr)B2 from elemental reactants using the field-activated, pressure-assisted synthesis method and employing the SPS apparatus was investigated. The nature of the products depended on temperature; they were nearly pure solid solutions at 1900°C with minor amounts of β-WB. The product density and microhardness depended on the temperature of synthesis for the same value of applied pressure (64 MPa). Samples with the highest density (94%) corresponded to a hardness of 22.7 GPa. When annealed at 1500°C, the solid solutions decomposed, precipitating a (W,Ti,Cr)B2 phase in a spinodal form. In addition, β-WB precipitates in the form of thin (0.4–5.3 nm) layers were observed. They existed in a 60°/120° orientation to the (Ti,W,Cr)B2 matrix, in agreement with previous observations. Highly faceted, small (nanosized) pores associated with the β-WB precipitates were also observed. 相似文献
994.
Daniel Kleine Manfred Mürtz Jörg Lauterbach Hannes Dahnke Wolfgang Urban Peter Hering Karl Kleinermanns 《Israel journal of chemistry》2001,41(2):111-116
Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser absorption method. It can be used for quantitative analysis of molecular species at the sub-ppb level. The absorption cell (cavity) is sealed by two high-reflective mirrors on each side, which results in an effective absorption path-length of some kilometers. Our experiments for atmospheric gas analysis have been carried out so far with an Excimer pumped dye laser in the UV-VIS and a CO overtone sideband laser in the wavelength region around 3 μm. Experiments with an all solid-state difference frequency laser system will follow. In the UV-VIS region, we measured trace gas molecules like SO2, NO2, and CH2O. In the mid-infrared, around 3 μm, we measured hydrocarbons like CH4, C2H6, and C2H4 with a detection limit of less than 1 ppb. The noise equivalent absorption coefficients in the MIR are in the order of 1.7·10−9 cm−1. Due to the high data acquisition rate and the high sensitivity, CRDS enables real-time detection of trace gases in ambient air. 相似文献
995.
996.
Aysel Kantürk Figen Evren Terzi Nural Yilgör Saip Nami Kartal Sabriye Pişkin 《Korean Journal of Chemical Engineering》2013,30(4):878-890
hermal degradation characteristics of Tetra Pak panel boards (TPPB) can be useful to improve usage of such panels as an alternative to wood-based products such as plywood, fiberboard, and particleboard. In the study, samples from the TPBBs manufactured from waste Tetra Pak packages (WTPP) were heated in a nitrogen atmosphere at different heating rates (10, 15 and 20 °C/min) using a thermal analysis system. The Coats-Redfern kinetic model was applied to calculate kinetic parameters. The degradation rate equations were then established. In addition, the kinetic compensation effect (KCE) was used to correlate the pre-exponential factor (k o ) with activation energy (E a ) and the existence of the KCE was accepted. TG-FT/IR analyses were applied to the TPPB degradation and then the FT-IR stack plot was used to analyze gas products (CO2, CH4, HCOOH, and CH3OH). Infrared vibrational frequencies and the micro, crystal structure of the TPPBs were investigated by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and X-Ray diffraction analysis (XRD), respectively. 相似文献
997.
998.
A new approach to manufacture a complete thermal barrier coating system in a single step is studied in the frame of the European FP7 project PARTICOAT. Spherical μm-Al particles are deposited on different substrate alloys. During the sintering process in air, the μm-Al particles are oxidized and converted into hollow alumina spheres forming a ceramic “foam” (top coat), and simultaneously an Al rich diffusion layer (bond coat) is formed in the subsurface zone of the substrate.The “green” coatings deposited by air brush on IN738, René80 and CM247 nickel based alloys were cured at 300 °C and then isothermally exposed at 800 and 1000 °C in air for up to 1000 h. The oxide formation and the microstructure of the coatings were studied by thermo gravimetrical analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX).The coatings were adherent for all the substrates and temperatures tested. René80 shows the lowest mass gain whereas IN738 and CM247 show higher mass gains at the temperatures studied. Additionally, the use of reactive element oxides in the coating was investigated, demonstrating the flexibility and viability of this low cost coating concept. 相似文献
999.
The resulting surface quality after 5-axis ball end milling is of superior importance because finish milling is often the last process step determining the functional performance of a component. However, the prediction of surface topography is still a challenging task. Especially in ball end milling with the characteristic sickle shaped chip cross section, ploughing effects in the area of low chip thickness result in plastic deformation and surface defects (also known as burr). This paper provides a new approach to predict those surface defects by considering the minimum chip thickness for complex milling engagement conditions within a virtual process design. This allows the choice of suitable process parameters without extensive experimental efforts. 相似文献
1000.
Thomas Veltzke Lars Kiewidt Jorg Thöming 《American Institute of Chemical Engineers》2015,61(4):1404-1412
In many technical processes gas, multicomponent diffusion takes place in confinements that are rarely uniform in direction of their long axis (e.g., catalysts pores). Here, we show that in conical tubes multicomponent diffusion is hindered. This effect increases with ratio of inlet to outlet cone radius Λ, indifferent of the orientation of the tube. Based on the Maxwell–Stefan equations, predictive analytical solution for ideal multicomponent diffusion in slightly tapered ducts is developed. In two‐bulb diffusion experiments on a uniform tube, the results of Duncan and Toor (1962) were reproduced. Comparison of model and experiment shows that the solution presented here provides a reliable quantitative prediction of the temporal change of H2, N2, and CO2‐concentration for both tube geometries, uniform and slightly conical. In the demonstrated case (Λ = 3.16), mass diffusion is 68% delayed. Thus, for gaseous diffusion in “real,” typically tapered pores the transport limitation is more serious than considered so far. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1404–1412, 2015 相似文献