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排序方式: 共有373条查询结果,搜索用时 62 毫秒
121.
Tatyana Lyubimova Dmitriy Lyubimov Yanina Parshakova Andrey Ivantsov 《Microgravity science and technology》2011,23(2):143-150
The onset of thermal convection in a system of two horizontal layers of immiscible liquids of similar densities is studied under low gravity conditions. A constant heat flux is prescribed
at both rigid boundaries. A generalized Boussinesq approach that allows correct accounting for the interface deformation is used. The long-wave perturbations emerge under low-gravity
conditions; either monotonic or oscillatory modes are critical depending on the problem. Moreover, two different modes of
the monotonic instability exist. For the first instability mode, the convection dominates, whereas the interface remains nearly
undeformable. The second monotonic instability mode is substantially related to interface deformations. The system of non-linear
amplitude equations describing the behavior of long-wave regimes at finite-amplitude interface deflection and finite supercriticalities
is obtained. The analytical and numerical investigations of these equations show that the stable non-trivial stationary solutions
are absent, and after a transient at least one of the layers is split into the areas not connected to each other. The nonlinear
regimes of cellular convection are studied numerically by the Level Set method. 相似文献
122.
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124.
Technology for the production of new materials based on the heat-resistant powder metallurgy nickel alloy ÉP975 was developed, and the mechanical and tribological properties of these investigated. The formation features of the metallographic structure of the materials was studied. Recommendations for the practical use of the new composites are given. 相似文献
125.
Decomposition of toxic pollutants in landfill leachate by ozone after coagulation treatment 总被引:4,自引:0,他引:4
Poznyak T Bautista GL Chaírez I Córdova RI Ríos LE 《Journal of hazardous materials》2008,152(3):1108-1114
This study deals with evaluation of organic matter from Mexico City waste sanitary landfill leachate of Bordo Poniente (including domestic and industrial) by ozonation after a coagulation treatment with Fe2(SO4)(3) (2.5 g/L at pH 4-5). The content of humic substances after the coagulation treatment decreases up to 70%. Then leachate obtained from a solid with initial COD=1511 mg/L and the pH 8.5 was treated by ozone. The aqueous samples by a UV-vis and HPLC technique were analyzed. The partial identification of the initial composition of the organic matter as well as of intermediates and final products was carried out after the extraction of the initial and ozonated leachate with benzene, chloroform:methanol (2:1) and hexane. Then the extracts with a gas chromatograph with mass detector and FID were analyzed. In the HPLC results we identify malonic and oxalic acids. The initial concentrations of these acids were 19 mg/L and 214 mg/L, respectively. The oxalic acid is formatted and accumulated in ozonation. The obtained results show that the color disappears (visually) at 100% during 5 min of ozonation. The organic substances, extracted with chloroform-methanol, may be destructed during 15 min of ozonation; the organic matter, extracted with benzene, destructs completely by ozone during 5 min, and the organic compounds extracted with hexane have a low ozonation rate. The toxic compounds presented in leachate decompose completely during 15 min of ozonation. The ozonation rate constants for each group of organics (as observed constants) were calculated applying simplified mathematical model and the recurrent least square method using the program MATLAB 6.5. 相似文献
126.
Asiya E. Turgambaeva Galina Zharkova Petr Semyannikov Vladislav V. Krisyuk Tatyana Koretskaya Sergey Trubin Boris Kuchumov Igor Igumenov 《Gold bulletin》2011,44(3):177-184
Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH3)2AuS2CN(C2H5)2 (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition
to elemental gold were studied. Saturated vapor pressure was found to be ~10−3–10−1 Torr at 50–90°C. Decomposition of the vapor on the surface starts at T = 210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique,
it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them
result in the formation of elemental gold, saturated C2–C4 alkanes and (1) protonated ligand or (2) methylated ligand. The
third one results in elemental gold and gaseous products: C2–C3 alkylmercaptanes and CH3SCN(C2H5)2. The formation of gold as a sole solid product within the temperature range 210–240°C was confirmed by X-ray photoelectron
spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability
among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition. 相似文献
127.
Mikhail A. Matsko Ludmila G. Echevskaya Marina P. Vanina Marina I. Nikolaeva Tatyana B. Mikenas Vladimir A. Zakharov 《应用聚合物科学杂志》2012,126(6):2017-2023
Separation into narrow MWD fractions (liquid–liquid fractionation) and preparative TREF (temperature rising elution fractionation) with subsequent analysis of fractions by GPC, FTIR, and 13C NMR spectroscopy were used to study the comonomer distribution of ethylene/1–hexene copolymers produced over highly active supported titanium‐ and vanadium‐magnesium catalysts (TMC and VMC) and a supported zirconocene catalyst. These catalysts produce PE with different MWD: Mw/Mn values vary from 2.9 for zirconocene catalyst, 4.0 for TMC, and 15 for VMC. 1‐Hexene increases polydispersity to 25 for copolymer produced over VMC and hardly affects MWD of the copolymer produced over TMC and zirconocene catalysts. The most broad short chain branching distribution (SCBD) was found for ethylene/1–hexene copolymers produced over TMC. VMC and supported zirconocene catalyst produce copolymers with uniform profile of SCB content vs. molecular weight in spite of great differences in Mw/Mn values (22 and 2.5 respectively). TREF data showed that majority of copolymer produced over supported zirconocene catalyst was eluted at 70–90°C (about 85 wt %). In the case of VMC copolymer's fractions were eluted in the broad temperature interval (40–100°C). Accordingly, TREF data indicate a more homogeneous SCBD in copolymer, produced over supported zirconocene catalyst. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
128.
Tatyana V. Sukhareva 《Journal of Superconductivity and Novel Magnetism》2013,26(5):2021-2025
The objective of the work is to establish the contribution of superconductive granules and grain boundaries (weak links) in magnetoresistance ρ value of YBa2Cu3O7?δ granular high-temperature superconductor (HTS) at T<T c. The current-voltage characteristics (CVCs) $E(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ of YBa2Cu3O6.95 ceramic samples were measured in H ext (0≤H ext≤≈500 Oe) magnetic fields. The CVCs $E(j)_{H_{\mathrm{trap}} = \mathrm{const}}$ of the samples magnetized in H treat magnetic fields were measured at H ext=0. Based on the CVCs, $\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ , ρ(H ext) j=const and $\rho(j)_{H_{\mathrm{treat}} = \mathrm{const}}$ dependences were reestablished. The comparative analysis of $\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}$ and ρ(H ext) j=const dependences indicates the magnetic field redistribution between grain boundaries and superconductive granules influence on transport and galvanomagnetic properties of granular HTS. The superconductive grain magnetoresistance ρ g was established to be significantly lower than ρ J value of Josephson medium. 相似文献
129.
Tatyana V. Laurinavichene Kestutis S. Laurinavichius Anatoly A. Tsygankov 《International Journal of Hydrogen Energy》2014
Purple non-sulfur bacteria Rhodobacter sphaeroides N7 was integrated into the heterotrophic starch-hydrolyzing consortium containing Clostridium butyricum as the main component. The resulting light-dependent consortium with Bchl ∼9 μg/ml was maintained during 12 months of regular transfers. The protein content in this consortium was four-fold higher compared to the heterotrophic consortium, suggesting that purple bacteria became its important component. Under illumination, the starch hydrolysis by the light-dependent consortium (as opposed to heterotrophic consortium) resulted in the absence of VFAs, hydrogen production being quite similar and residual hexose higher. Fermentation of glucose (unlike to starch) by the light-dependent consortium or Rb. sphaeroides alone resulted in ∼3 fold increase of hydrogen production compared to the heterotrophic consortium. Apparently, hydrolysis of starch to hexose was the bottleneck in H2 photoproduction by the light-dependent consortium. Availability of residual hexose after photofermentation of starch/glucose by the light-dependent consortium or Rb. sphaeroides is discussed. 相似文献
130.
Tatyana V. Bandos Álvaro Montero Esther Fernández Juan Luis G. Santander José María Isidro Jezabel Pérez Pedro J. Fernández de Córdoba Javier F. Urchueguía 《Geothermics》2009
A solution to the three-dimensional finite line-source (FLS) model for borehole heat exchangers (BHEs) that takes into account the prevailing geothermal gradient and allows arbitrary ground surface temperature changes is presented. Analytical expressions for the average ground temperature are derived by integrating the exact solution over the line-source depth. A self-consistent procedure to evaluate the in situ thermal response test (TRT) data is outlined. The effective thermal conductivity and the effective borehole thermal resistance can be determined by fitting the TRT data to the time-series expansion obtained for the average temperature. 相似文献