全文获取类型
收费全文 | 3298篇 |
免费 | 127篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 36篇 |
综合类 | 14篇 |
化学工业 | 1070篇 |
金属工艺 | 61篇 |
机械仪表 | 41篇 |
建筑科学 | 184篇 |
矿业工程 | 4篇 |
能源动力 | 56篇 |
轻工业 | 320篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 177篇 |
一般工业技术 | 677篇 |
冶金工业 | 319篇 |
原子能技术 | 25篇 |
自动化技术 | 438篇 |
出版年
2023年 | 39篇 |
2022年 | 57篇 |
2021年 | 73篇 |
2020年 | 43篇 |
2019年 | 61篇 |
2018年 | 50篇 |
2017年 | 50篇 |
2016年 | 85篇 |
2015年 | 88篇 |
2014年 | 101篇 |
2013年 | 165篇 |
2012年 | 171篇 |
2011年 | 206篇 |
2010年 | 152篇 |
2009年 | 165篇 |
2008年 | 170篇 |
2007年 | 155篇 |
2006年 | 138篇 |
2005年 | 129篇 |
2004年 | 102篇 |
2003年 | 74篇 |
2002年 | 70篇 |
2001年 | 61篇 |
2000年 | 61篇 |
1999年 | 73篇 |
1998年 | 83篇 |
1997年 | 64篇 |
1996年 | 42篇 |
1995年 | 55篇 |
1994年 | 50篇 |
1993年 | 35篇 |
1992年 | 42篇 |
1991年 | 46篇 |
1990年 | 27篇 |
1989年 | 33篇 |
1988年 | 34篇 |
1987年 | 33篇 |
1986年 | 25篇 |
1985年 | 26篇 |
1984年 | 32篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1981年 | 24篇 |
1980年 | 18篇 |
1979年 | 20篇 |
1978年 | 17篇 |
1977年 | 16篇 |
1976年 | 28篇 |
1975年 | 19篇 |
1974年 | 16篇 |
排序方式: 共有3427条查询结果,搜索用时 15 毫秒
61.
Well-formed carbon nanocones at the ends of micrometer-diameter carbon fibers (CFs) were fashioned into functional tips for scanning tunneling microscopy (STM) and miniaturized voltammetric sensors. Sharpening of single graphite filaments was achieved by simple DC electrochemical etching in 0.1 N NaOH. Operated as STM tips, pointed CFs resolved in air the contour and surface morphology of a nanoscopic Au line pattern and imaged in vacuum a Si (1 1 1) surface with clear atomic resolution. Subjecting already etched CFs to tip-sparing insulation with electrodeposited paint produced conical carbon ultramicroelectrodes (UMEs) with effective radii down to about 900 nm. Comparative cyclic voltammetry trials in alkaline, neutral and acidic solutions showed that the conical carbon UME’s had a wider practical potential window for electroanalytic applications than, for instance, Pt disk UMEs. The CF-based conical sensors described here are exceptionally easy to make with simple laboratory equipment and perform well in STM topography imaging and voltammetry. The inherent simplicity of sensor production widens the field of potential users, and offers clear advantages over existing types of UMEs, in particular those based on carbon nanotubes, which are especially hard to handle in an optical microscope setting. 相似文献
62.
Nitrate radicals are being recognized as key intermediates in a growing list of important chemical processes in the atmosphere. Here, the role of nitrate radicals (NO3) in tropospheric chemistry is discussed, with special emphasis on results from field measurements, most of which have been made by differential optical absorption spectroscopy (DOAS), with matrix-isolation electron spin resonance being an alternative technique. Nitrate radicals were observed in the atmosphere at peak mixing ratios of 350 ppt. Long-term observation of NO3 shows that 24-h averages in rural air masses are closer to a few ppt. Nevertheless, the NO3 radical plays an important role in the non-photochemical conversion of NOx to HNO3. Also, NO3 is a strong oxidizing agent and initiates the night-time removal of atmospheric trace species such as olefins, aromatic hydrocarbons, and organic sulfur compounds. Finally, night-time peroxy radical production and release of reactive halogen species from sea salt aerosol might be initiated by NO3 reactions. 相似文献
63.
Gerd Scheying Ingrid Wührl Ulrich Eisele Ralf Riedel 《Journal of the American Ceramic Society》2004,87(3):358-364
Two ultrafine, undoped ZrO2 powders with median primary particle sizes of 9 and 25 nm were used to prepare ceramic suspensions for thermoplastic extrusion. The organic vehicle consisted of an industrial-grade poly(ethylene- co -vinyl acetate) (EVA) or polyethylene (PE-HD) and decanoic acid as a dispersing agent. The powder volume loadings achieved were 44% and 52% by volume for the two powders, respectively. The amount of dispersant needed was calculated from a new model based on available chemisorption sites on the powder surface. Mixing and extrusion were conducted using a conventional modular plastic processing unit. Green bodies were dewaxed up to 450°C in an inert atmosphere and sintered to full density in air at 1060° and 1100°C, respectively. Analysis of the ceramic phase content and the microstructure of the bodies is presented. 相似文献
64.
Kathrin Burghardt Karl-Georg Husler Michael Gerd Martl Klaus Hummel Ulrich Gebauer Klaus Gehrke 《大分子材料与工程》1992,194(1):133-148
The copolymerization of butadiene with a technical divinylbenzene fraction was investigated to study the modification of cis-1,4 polybutadiene. Beside the Ziegler-Natta-catalyst nickeloctanoate/bortrifluoride/aluminiumtriethyl, another catalytic system consisting of nickeloctanoate/titaniumtetrachloride/aluminiumtriethyl was used, which allows to polymerize more divinylbenzene because of its higher activity toward vinylaromates. With the help of spectroscopical, pyrolysis-gaschromatographical and thermoanalytical methods one can obtain relations between glass-, crystallization- and melting temperature and the microstructure of the polymer. It can be shown that not only the divinylbenzene but also the trans-1,4- and the 1,2-vinyl units are statistically distributed in the polymer. By this, beside the pyrolysis-gaschromatography, particularly the differential scanning calorimetry is a useful tool to characterize the structure of partially crosslinked polymers obtained from polymerization of technical fractions. 相似文献
65.
Summary: The influence of number‐average molecular weight ranging from 1.4 · 104 to 1.2 · 106 g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.
66.
Copper deposition in the presence of an organic additive (3-mercaptopropionic acid, MPA) was studied by cyclic voltammetry and in situ scanning tunneling microscopy (STM) and the results are compared to those for additive-free solutions. It is shown that underpotential deposition (upd) of copper onto a fully MPA-covered electrode produces a defect-rich substrate, but the defects are blocked by the dense organic film for bulk deposition, resulting in a low number of nuclei. A grain-refining effect of MPA, however, was found, when Cu deposition was initiated shortly after addition of MPA to the solution, i.e., for a low-coverage MPA adlayer. 相似文献
67.
Prof. Dr.-Ing. habil. Anette Müller Steffen Liebezeit Dr.-Ing. Ulrich Palzer 《化学,工程师,技术》2023,95(10):1647-1653
Heterogeneous construction waste such as masonry rubble has potential as a raw material for the production of lightweight aggregates similar to expanded clays or even pumice. In the present paper, the suitability of feedstocks with considerable gypsum contents was investigated in a pilot plant. Based on the results, initial technological statements could be made. According to these, energetic advantages can be expected in comparison with lightweight aggregates made from expanded clays. 相似文献
68.
Dr. Erik Strandberg Dr. Parvesh Wadhwani Dr. Jochen Bürck Dr. Patrick Anders Dr. Christian Mink Dr. Jonas van den Berg Raffaele A. M. Ciriello Dr. Manuel N. Melo Prof. Dr. Miguel A. R. B. Castanho Prof. Dr. Eduard Bardají Prof. Dr. Jakob P. Ulmschneider Prof. Dr. Anne S. Ulrich 《Chembiochem : a European journal of chemical biology》2023,24(4):e202200602
BP100 is a cationic undecamer peptide with antimicrobial and cell-penetrating activities. The orientation of this amphiphilic α-helix in lipid bilayers was examined under numerous conditions using solid-state 19F, 15N and 2H NMR. At high temperatures in saturated phosphatidylcholine lipids, BP100 lies flat on the membrane surface, as expected. Upon lowering the temperature towards the lipid phase transition, the helix is found to flip into an upright transmembrane orientation. In thin bilayers, this inserted state was stable at low peptide concentration, but thicker membranes required higher peptide concentrations. In the presence of lysolipids, the inserted state prevailed even at high temperature. Molecular dynamics simulations suggest that BP100 monomer insertion can be stabilized by snorkeling lysine side chains. These results demonstrate that even a very short helix like BP100 can span (and thereby penetrate through) a cellular membrane under suitable conditions. 相似文献
69.
Highly resistive dusts show markedly non‐ohmic properties. The property known as specific resistivity is strongly dependent on the dust layer thickness and on the polarity of the high voltage. The current transport occurs by excess charges of both polarities, which leads to high space charge densities and induces strong electrostatic fields. The theory of electrets provides a consistent explanation of the phenomena observed so far. To investigate the electrical properties, highly resistive dusts were exposed to an electrical field with interfering corona discharges within a tip‐plate arrangement. 相似文献
70.
Lena Arnold Gauthier Averlant Dr. Stefan Marx Mathias Weickert Ulrich Müller Jonathan Mertel Carsten Horch Mikulas Peksa Frank Stallmach 《化学,工程师,技术》2013,85(11):1726-1733
With the increasing demand for alternative fuels the storage of natural gas (NG) in adsorbents like metal organic frameworks (MOFs) will become more important. In order to use MOFs as storage media in fuel delivery systems, the optimization of mass and energy transfer of the system is crucial. For rapid NG filling of a tank, molecules need to reach the adsorption sites within a reasonable time while the heat of adsorption should be dissipated to the environment. In this article, mass transfer in shaped bodies of MOFs was determined by permeability measurements and pulsed field gradient (PFG) NMR spectroscopy. The heat dissipation was also experimentally measured and both data sets were used to set up a theoretical density function theory model to predict the behavior of MOFs for NG storage. 相似文献