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991.
Ventilation system design for a church pipe organ using numerical simulation and on-site measurement
Since old churches have had heating installed, more complaints have arisen of organs sounding out of tune. Sound frequency of organ pipes is dependent on air temperature. Old churches tend to have very large volumes, so are typically heated just before and during services in wintertime, in order to reduce energy usage. Warm air plumes rise at radiators and spread out into the room, finally reaching the cold organ casing where they cause a non-uniform temperature distribution within. If pipes standing in different temperature zones are played at the same time the organ sounds out of tune due to clearly audible beats (interference between two slightly different frequencies). The purpose of this study was to design a ventilation system inside the organ casing, able to create a uniform temperature distribution around the pipes. A computational fluid dynamic (CFD) model was developed for the St. Martin church in Oberesslingen, Germany. It was validated by on-site measurements that had been carried out in the organ casing of the church. Four organ divisions containing 300–500 pipes were represented by equivalent porous material zones. Their properties were determined using an auxiliary two-dimensional model of a staggered array consisting of 392 pipes. The effect of different ventilation system settings on the temperature field in the organ casing was examined. Best results were achieved by a system consisting of two ventilation lines together with a thin, synthetic net placed at the open interface between church and organ casing in order to reduce warm air inflow. 相似文献
992.
Stephan R. Larrick James R. Clark Donald S. Cherry John Cairns Jr 《Water research》1981,15(7):875-880
Heterotrophic bacterial populations were sampled at 9 sites around a fossil fuel power plant to assess the ecological impact of the resulting effluents on naturally occurring heterotrophic microbes. The total colony forming units (CFU) remained relatively high at all stations, ranging from 13,804 CFU ml−1 in the heavy ash basin to 2630 CFU ml−1 in an uninfluenced station, Adair Run—upstream. The percent of the total colony counts which were chromagenic was correlated with physico/chemical stresses and varied from a high of 59.0% at the reference New River station to 13.2% in the heavy ash basin. A Sequential Comparison procedure (SCI) produced diversity indices which ranged from 8.21 in upstream New River to 6.23 in the ash-influenced Adair Run station. Assimilation of [3H]glucose was used to assess the functional status of the organisms and was reduced 86.0% in the heavy ash basin and 65.5% in the fly ash basin. The structure and function of bacterial communities in the ash basins were significantly different from the same parameters of populations inhabiting reference environments; however, the basin effluents had a lesser effect on New River bacteria. 相似文献
993.
Oxidation and removal of arsenic (III) from aerated groundwater by filtration through sand and zero-valent iron 总被引:1,自引:0,他引:1
Removing arsenic from contaminated groundwater in Bangladesh is challenging due to high concentrations of As(III), phosphate and silicate. Application of zero-valent iron as a promising removal method was investigated in detail with synthetic groundwater containing 500 microg/L As(III), 2-3mg/L P, 20mg/L Si, 8.2mM HCO3-, 2.5mM Ca2+, 1.6mM Mg2+ and pH 7.0. In a series of experiments, 1L was repeatedly passed through a mixture of 1.5 g iron filings and 3-4 g quartz sand in a vertical glass column (10mm diameter), allowing the water to re-aerate between each filtration. At a flow rate of 1L/h, up to 8 mg/L dissolved Fe(II) was released. During the subsequent oxidation of Fe(II) by dissolved oxygen, As(III) was partially oxidized and As(V) sorbed on the forming hydrous ferric oxides (HFO). HFO was retained in the next filtration step and was removed by shaking of the sand-iron mixture with water. Rapid phosphate removal provided optimal conditions for the sorption of As(V). Four filtrations lead to almost complete As(III) oxidation and removal of As(tot) to below 50 microg/L. In a prototype treatment with a succession of four filters, each containing 1.5 g iron and 60 g sand, 36 L could be treated to below 50 microg/L in one continuous filtration, without an added oxidant. 相似文献
994.
Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability 总被引:6,自引:1,他引:6
Activated sludges are becoming more difficult to degrade in anaerobic digesters, due to the implementation of stricter nitrogen limits, longer sludge ages, and removal of primary sedimentation units. Thermal hydrolysis is a popular method to enhance degradability of long-age activated sludge, and involves pressure and heat treatment of the process fluid (150-160 degrees C saturated steam). However, as documented in this study, in a full-scale system, the use of thermal hydrolysis produces coloured, recalcitrant compounds that can have downstream impacts (e.g., failure of UV disinfection, and increased effluent nitrogen). The coloured compound formed during thermal hydrolysis was found to be melanoidins. These are coloured recalcitrant compounds produced by polymerisation of low molecular weight intermediates, such as carbohydrates and amino compounds at elevated temperature (Maillard reaction). By decreasing the THP operating temperature from 165 degrees C to 140 degrees C, THP effluent colour decreased from 12,677 mg-PtCo L(-1) to 3837 mg-PtCo L(-1). The change in THP operating temperature from 165 degrees C to 140 degrees C was shown to have no significant impact on anaerobic biodegradability of the sludge. The rate and extent of COD biodegradation remained largely unaffected by the temperature change with an average first order hydrolysis rate of 0.19 d(-1) and conversion extent of 0.43 g-COD(CH4)g-COD(-1). 相似文献
995.
Lenz K Hann S Koellensperger G Stefanka Z Stingeder G Weissenbacher N Mahnik SN Fuerhacker M 《The Science of the total environment》2005,345(1-3):141-152
Platinum originating from the excreted cancerostatic platinum compounds (CPC) cisplatin, carboplatin and oxaliplatin was monitored over a period of 28 days in the wastewater of the oncologic ward of the Vienna University Hospital. Concentration levels ranging from 4.7 to 145 microg L(-1) were measured by inductively coupled plasma mass spectrometry (ICP-MS). An average ratio of weekly drug emission/drug consumption of 0.27+/-0.12 was assessed. Model studies were carried out for fundamental understanding of CPC interaction with the solid phases present at different stages of the water cycle. Wastewater and activated sludge were spiked with CPC at concentration levels as found in the sewer of the oncologic ward. The platinum concentration remaining in the tested solution was measured after 24 h of incubation. Depending on pH, the three substances exhibited considerably different adsorption rates in wastewater. At pH 7, cisplatin was adsorbed by 88%, whereas only 26% of carboplatin and 54% of oxaliplatin were removed from the aqueous phase. Adsorption by activated sludge was higher, less affected by pH variation and comparable for all investigated CPC (96% for cisplatin, 70% for carboplatin and 74% for oxaliplatin at pH 6.8). In a next step, the dependence of CPC adsorption was tested for wastewater and activated sludge of different sampling sites. Strong variations were found only for wastewater, whereas activated sludge showed more consistent elimination rates (average values: cisplatin 92%, carboplatin 72%, and oxaliplatin 78%). These findings indicate that the major part of the excreted CPC is adsorbed by the solid phase in the water cycle and is thus expected to be removed from the wastewater by sewage treatment plants. 相似文献
996.
James F. Rohan Bernadette M. Ahern Stephan Crowley Fernando M.F. Rhen 《Electrochimica acta》2009,54(6):1851-1812
Electroless magnetic thin films have been deposited from borane-based baths suitable for use in integrated magnetics on Si applications. The baths were developed for compatibility with standard photoresist for microfabrication of integrated magnetics on Si. The specific formulations, which differ from those reported previously, yield uniform, high saturation magnetisation (up to 2.15 T) deposits with low coercivity (<2 Oe). The resistivity of the film can be increased to minimise eddy current losses by using higher dimethylamine borane (DMAB) content or the inclusion of a second reducing agent, hypophosphite, to facilitate phosphorus codeposition of up to 7 at.%. The Ni content in the plating bath has been shown to exert significant influence over the composition, deposition rate and coercivity. XRD analysis suggests that the deposits consist of nanocrystalline phase with grains <20 nm. Such small grains are consistent with the observed low coercivity of the deposits. 相似文献
997.
Gold nanoparticles on highly oriented pyrolytic graphite (HOPG) electrodes are synthesized. They are stabilized in nanosized pits of well defined depth in the graphite surface. These pits are created by energetic cluster impact followed by etching under a well controlled oxygen atmosphere. We succeeded in the preparation of highly dispersed and stable Au electrodes with gold particles with a mean diameter smaller than 5 nm. The stability of the gold nanostructures for electrochemical applications has been tested by performing cyclic voltammetric measurements in 0.5 M H2SO4. While conventionally prepared sputter deposited electrodes show highly unstable structures in this size range, Au clusters stabilized in the nanosized containers are stable. 相似文献
998.
Stephan Laske Milan Kracalik Michael Gschweitl Michael Feuchter Günther Maier Gerald Pinter Ralf Thomann Walter Friesenbichler Günter Rüdiger Langecker 《应用聚合物科学杂志》2009,111(5):2253-2259
Structural characterization in polymer nanocomposites is usually performed using X‐ray scattering and microscopic techniques, whereas the improvements in processing and mechanical properties are commonly investigated by rotational rheometry and tensile testing. However, all of these techniques are time consuming and require quite expensive scientific equipment. It has been shown that a fast and efficient way of estimating the level of reinforcement in polymer nanocomposites can be performed by melt extensional rheology, because it is possible to correlate the level of melt strength with mechanical properties, which reflect both the 3D network formed by the clay platelets/polymer chains as well as final molecular structure in the filled system. The physical network made of silicate filler and polymer matrix has been evaluated by X‐ray diffraction and transmission electron microscopy. Extensional rheometry and tensile testing have been used to measure efficiency of the compatibilizer amount in a polypropylene‐nanoclay system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
999.
Thomas Böttcher Stephan A. Sieber Dr. 《Chembiochem : a European journal of chemical biology》2009,10(4):663-666
Disarmed forces : Inhibition of the central virulence regulator ClpP by structurally refined β‐lactones resulted in dramatically reduced production of devastating virulence factors, including pyrogenic toxin superantigens derived from pathogenic multiresistant Staphylococcus aureus strains. Targeting of this virulence regulator could present an attractive strategy for neutralizing the harmful effects of bacterial pathogens, and help the host immune response to eliminate the disarmed bacteria.
1000.
Peter Bihari Minnamari Vippola Stephan Schultes Marc Praetner Alexander G Khandoga Christoph A Reichel Conrad Coester Timo Tuomi Markus Rehberg Fritz Krombach 《Particle and fibre toxicology》2008,5(1):1-14