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61.
We consider the problem of navigation and guidance of a wheeled mobile robot towards a maneuvering target based on the measurements concerning only the distance from the robot to the target. We propose a sliding mode controller that drives the robot to the predefined distance from the target and makes the robot follow the target at this distance. Mathematically rigorous proof of convergence and stability of the proposed guidance law is presented. Simulation results confirm the applicability and performance of the proposed guidance approach. 相似文献
62.
Alexey M. Gurin 《Journal of Low Temperature Physics》2000,119(3-4):491-495
In Ref. 1 the principle of the adequacy between the stability of the structure of amorphous metals and the completeness of the set of configuration vacancies has been introduced. The principle of adequacy is valid for all the methods of amorphous solid metals production described in Ref. 2. This principle is the basis of the proposed novel technology of production of stable amorphous films sputtered on the cold substrate. The technology proposed takes into account the geometry of microgravity in the film structure and thus excludes the effect of the film burst crystallization. 相似文献
63.
Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to induce latent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C, and upon heating to 85 °C gave complete conversion of monomer to polymer in less than 2 hours. All of the complexes were very stable to air, moisture, and elevated temperatures up to at least 90 °C, and exhibited a long catalyst lifetime in solution at elevated temperatures. 相似文献
64.
Vladimir Ivanovich Lysenko Sergey Bardakhanov Alexey Korchagin Nikolay Kuksanov Alexander Lavrukhin Rustam Salimov Sergey Fadeev Vladislav Cherepkov Mikhail Veis Andrey Nomoev 《Bulletin of Materials Science》2011,34(4):677-681
Electron-beam evaporation of various natural and industrial materials in the atmosphere of different gases at atmospheric
pressure can be used for the synthesis of nanosize powders. These powders are characterized by high purity and may exhibit
unusual properties. In particular, nanopowders of silicon dioxide and oxide (SiO2, SiO), magnesia (MgO), alumina (Al2O3), titania (TiO2), gadolinium oxide (Gd2O3), various metals (tantalum, molybdenum, nickel, aluminium, copper, silver), semiconductor (Si), nitrides (AlN, TiN), and
some other substances had been produced. The process of nanopowder synthesis is highly effective; in particular, the yield
of oxides can exceed ten kilograms per hour. 相似文献
65.
The study concerns steady configurations of a perfectly wetting liquid in contact with its pure vapor and a superheated substrate/wall
maintained at a constant temperature. Despite the perfect wetting, the system is characterized by a finite apparent contact
angle formed at a microscale, within a steady microstructure of the contact line, the finiteness owing itself to an actually
dynamic situation caused by the evaporation process. The angle is assumed to be small here, which is the case for sufficiently
small superheats. When macroscopically treating a steady meniscus, one typically implies that the wall is met at the contact
angle given by the microstructure. This remains somewhat an intuitive, heuristic approach unless a more rigorous asymptotic
matching is carried out between the meniscus and the microstructure, which is accomplished in the present paper by studying
an intermediate zone connecting these two regions. The analysis, based upon a standard one-sided planar model of an evaporating
liquid layer in the lubrication approximation, confirms the validity of the mentioned approach. A possible uncertainty in
the definition of the contact angle is shown to be small given that the macroscopic curvature (i.e. that of the meniscus and
of the wall) is small on the scale of the contact line microstructure. 相似文献
66.
Shevchenko Alexey V. Dudnik Elena V. Ruban Alexey K. Red'ko Viktor P. Lopato Lidiya M. 《Powder Metallurgy and Metal Ceramics》2002,41(11-12):558-563
An 80 mass% ZrO2 ― 20 mass% Al2O3 powder was produced using a complex method which integrates sol-gel technology and hydrothermal synthesis. The specific surface areas of the powder varied from 39 to 5.3 m2/g depending on the thermal treatment conditions. Metastable F-ZrO2 formed after powder annealing at 400°C. The phase transformation F-ZrO2 → T-ZrO2 (traces of M-ZrO2) occurred under powder thermal treatment from 700 to 1000°C. Only Θ-Al2O3 was detected under experimental conditions. The powder was characterized by sintering activity. Operating the processes under powder thermal treatment in the ZrO2 ― Y2O3 ― CeO2 ― Al2O3 system will allow one to produce a variety of ceramic microstructures from fine-grained to “self-reinforced.” These powders can be used in manufacturing surgical cutting tools as well as in ceramic passive bioimplants and solid electrolytes for fuel elements. 相似文献
67.
Yiyang Liu Kelly E. Kim Myles B. Herbert Alexey Fedorov Robert H. Grubbs Brian M. Stoltz 《Advanced Synthesis \u0026amp; Catalysis》2014,356(1):130-136
A highly efficient palladium‐catalyzed decarbonylative dehydration reaction of carboxylic acids is reported. This method transforms abundant and renewable even‐numbered natural fatty acids into valuable and expensive odd‐numbered alpha olefins. Additionally, the chemistry displays a high functional group tolerance. The process employs a low loading of palladium catalyst and proceeds under solvent‐free and relatively mild conditions.
68.
Naureen Akhtar Alexey O. Polyakov Aisha Aqeel Pavlo Gordiichuk Graeme R. Blake Jacob Baas Heinz Amenitsch Andreas Herrmann Petra Rudolf Thomas T. M. Palstra 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(23):4912-4919
Perovskite‐based organic–inorganic hybrids hold great potential as active layers in electronics or optoelectronics or as components of biosensors. However, many of these applications require thin films grown with good control over structure and thickness—a major challenge that needs to be addressed. The work presented here is an effort towards this goal and concerns the layer‐by‐layer deposition at ambient conditions of ferromagnetic organic–inorganic hybrids consisting of alternating CuCl4‐octahedra and organic layers. The Langmuir‐Blodgett technique used to assemble these structures provides intrinsic control over the molecular organization and film thickness down to the molecular level. Magnetic characterization reveals that the coercive field for these thin films is larger than that for solution‐grown layered bulk crystals. The strategy presented here suggests a promising cost effective route to facilitate the excellently controlled growth of sophisticated materials on a wide variety of substrates that have properties relevant for the high density storage media and spintronic devices. 相似文献
69.
Georgy Terentyuk Elizaveta Panfilova Vitaly Khanadeev Daniil Chumakov Elina Genina Alexey Bashkatov Valery Tuchin Alla Bucharskaya Galina Maslyakova Nikolai Khlebtsov Boris Khlebtsov 《Nano Research》2014,7(3):325-337
Nanocomposites (NCs) consisting of a gold nanorod core and a mesoporous silica shell doped with hematoporphyrin (HP) have been fabricated in order to improve the efficiency of cancer treatment by combining photothermal and photodynamic therapies (PDT + PTT) in vivo. In addition to the long-wavelength plasmon resonance near 810-830 nm, the fabricated NCs exhibited a 400-nm absorbance peak corresponding to bound HP, generated singlet oxygen under 633-nm excitation near the 632.5-nm Q-band, and produced heat under a 808-nm near-infrared (NIR) laser irradiation. These modalities were used for a combined PDT + PTT treatment of large (about 3 cm3) solid tumors in vivo with a xenorafted tumor rat model. NCs were directly injected into tumors and irradiated simultaneously with 633-nm and 808-nm lasers to stimulate the combined photodynamic and photothermal activities of NCs. The efficiency of the combined therapy was evaluated by optical coherence tomography, histological analysis, and by measurements of the tumor volume growth during a 21-day period. The NC-mediated PDT led to weak changes in tissue histology and to a moderate 20% decrease in the tumor volume. In contrast, the combined PDT + PTT treatment resulted in the large-area tumor necrosis and led to dramatic decrease in the tumor volume. 相似文献
70.
The quantification of a virus plays an important role in vaccine development, clinical diagnostics, and environmental contamination assays. In all these cases, it is essential to calculate the concentration or number of intact virus particles (ivp) and estimate the degree of degradation and contamination of virus samples. In this work, we propose a cost-efficient, robust method for the quantification and characterization of intact viruses based on capillary zone electrophoresis. This separation method is demonstrated on vaccinia virus (VV) with oncolytic properties. After virus sample preparation, the solution contains intact VV as well as broken viruses and residual DNA from the host cell used for preparation. Regulatory requirements limit the amount of the host cell DNA that can be present in vaccines or human therapeutics. We apply capillary electrophoresis to separate intact virus particles and the residual DNA and to measure the level of virus contamination with DNA impurities. Intercalating YOYO-1 dye is used to detect the encapsulated and free DNA by laser-induced fluorescence. After soft lysis of VV with proteinase K, all encapsulated DNA is dissolved to the free DNA. The change in peak areas and a DNA calibration curve help determine the initial concentration of intact viruses. This viral quantitative capillary electrophoresis (Viral qCE) is able to quantify the oncolytic vaccinia virus in the range of 10(6) to 10(12) ivp/mL. 相似文献