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161.
Silica (SiO2)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO2 (diameter = 20 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. The particle sizes of such core–shell structures [number‐average particle diameter (Dn) = 35–40 nm] were controlled by the variation of the feed amounts of the monomers and surfactant, or emulsion system. The size distributions were relatively narrow (weight‐average particle diameter/Dn ≈ 1.05). These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brush encapsulated SiO2 particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by SiO2‐crosslinked PS particles as a macroinitiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
162.
用呋喃树脂砂生产薄壁铸钢件热裂纹成因的分析 总被引:3,自引:0,他引:3
将呋喃树脂砂工艺铸钢件上出现的热裂纹分为“缩裂纹”和“拉裂纹”。对两种裂纹的和观形貌微区成分做了分析,深入探讨了两种裂纹具有的不同形成原因和形成过程,为采取有效对策解决裂提供了技术依据。 相似文献
163.
The new chiral salen complexes were synthesized and supported on mesoporous MCM‐41 through the condensation of 3‐aminopropyltrimethoxysilane
and 2,6‐diformyl‐4‐tert‐butylphenol by the multi‐grafting method. The immobilized optically active Co(II) salen complexes
showed a very high enantioselectivity in the asymmetric borohydride reduction of aromatic ketones. The chiral salen Co(II)
complexes immobilized over MCM‐41 were stable during the reaction and exhibited a relatively high enantioselectivity for the
reduction of ketones as compared with the homogeneous salen catalysts.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
164.
Extraction of unbound materials from carbon‐black‐filled natural rubber (NR) vulcanizates with different cure systems was studied using various solvents with different dielectric constants of n‐hexane, toluene, THF, acetone, and acetonitrile. The extraction was performed at room temperature and 40°C for 2 days and in the boiling solvent for 8 h. Amounts of extracted materials from the NR vulcanizates increase by increasing the temperature. Amounts of extracted materials from the NR vulcanizates with n‐hexane, toluene, and THF are more than those with acetone and acetonitrile. Amounts of extracted materials from the NR vulcanizate with a high crosslink density are less than those from the NR vulcanizate with a low one. Thermogravimetric analysis of the NR vulcanizates before and after the extraction were carried out to investigate components of the extracted materials. It was found that there were polymer components and metal complexes, as well as organic matters with a low molecular weight in the extracted materials. Abilities of the solvents to extract unbound materials from the NR vulcanizates were discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1995–2005, 1999 相似文献
165.
Formation of the adiabatic shear band in sheet metal is investigated with experiments for high strength steel sheets, 60 C
and 60 TRIP. Since the adiabatic shear band is formed as a result of adiabatic shear failure with a narrow band of concentrated
shear strain, the adiabatic shear band plays an important role in the analysis of high speed deformation phenomena. For shear
band experiments with a tension split Hopkinson bar, specimens are designed to induced large shear strain. The experimental
results show that the shear deformation modes of two sheet metals, 60 TRIP and 60 C, are quite different from each other in
that the adiabatic shear band is observed only in 60 C. The shear deformation in 60 TRIP is restrained by the abrupt increase
of strength due to the plastic strain, which interferes with propagation of the shear crack. Instead, a tensile crack developed
at the corner where the shear crack should have been initiated. As a result, the load-displacement curves show that the tensile
load of 60 TRIP specimens becomes higher than that of 60 C at the same displacement. 相似文献
166.
利用Gleelbe热模拟实验以及有限元分析了高应变速率对690合金热变形行为以及挤压可行性的影响,并根据实验和有限元结果进行挤压。结果表明:690合金的流变应力对应变速率均较敏感;大于10 s-1 的高应变速率下,变形温升显著上升;再结晶晶粒尺寸在低应变速率下,随应变速率的升高而降低,高应变速率则随应变速率的增加而增大;挤压时,最大挤压力随着应变速率的上升先降低再升高;根据实验以及有限元计算结果,成功挤出了合格的690管材。 相似文献
167.
Byung-Kook Hwang Hyuk-Soo Son Jae-Hyuk Kim Chang Hoon Ahn Chung-Hak Lee Jae-Yoon Song Young-Hyun Ra 《Journal of Industrial and Engineering Chemistry》2010,16(4):602-608
We have investigated the decomposition of excess sludge generated in a membrane bioreactor using a turbulent jet flow ozone contactor (TJC), which induced both hydrodynamic cavitation and ozonation reactions. We monitored the effects of various TJC operating parameters on the properties of the sludge, including the particle sizes, the particle size distribution, and the levels of soluble COD, total COD, and mixed liquor suspended solids. The TJC enhanced the degree of sludge reduction while consuming less energy, relative to conventional ozonation treatment systems, because of the synergic effects of hydrodynamic cavitation and ozonation. The hydrodynamic cavitation generated in the TJC increased the ozone mass transfer efficiency, which in turn promoted the rate of disintegration and solubilization of the sludge particles. 相似文献
168.
An aerosol dynamics equation for the below-cloud scavenging process considering phoretic and electric charging effects in addition to the conventional mechanisms (the Brownian diffusion, interception, and impaction) is developed by using the moment method. Then, the dynamics of particle size distribution by the below-cloud scavenging process is calculated by using the developed equation and verified with the measurement data. The calculated particle size distribution changes are quite small compared to the measured changes. The calculated removal rate is smaller by 10?2–10?3 than the measured data when only the conventional mechanisms are considered. With the extended mechanisms, the scavenging coefficient increases upto 20 times, mainly for the particle size range of 0.1 μm<dp<3.0 μm. However, the difference between the calculated and measured scavenging coefficient is still large, especially, for dp<0.1 μm. Other possible scavenging mechanisms that might affect the below-cloud scavenging process such as coagulation and condensational growth of hygroscopic particles, turbulence, and updraft into cloud are discussed. It is recommended that further studies on wet scavenging process are needed. 相似文献
169.
Jae Hong Park Ki Young Yoon Kwang Chul Noh Jeong Hoon Byeon Jungho Hwang 《Journal of aerosol science》2010,41(10):935-943
This study evaluated the charging characteristics of a carbon fiber ionizer for PM2.5 and carried out particle capture laboratory tests after an ionizer was installed upstream of the media of an electret cabin air filter. When the ion concentration per particle (Ni) of the carbon fiber charger was 106 ions/cm3, the average charge numbers for each particle were 1.54, 0.88, and 0.49 at 0.6, 1.2, and 1.8 m/s of face velocity, respectively (the particle charging times, τ, were 167, 83, and 56 ms, respectively). For these face velocities, the PM2.5 removal efficiencies of the filter media were 69.3%, 65.2% and 62.2%, respectively, but increased to 80.4%, 71.2% and 65.5%, respectively, when the ionizer was turned on. The carbon fiber ionizer was then installed in front of an electret cabin filter in the air conditioning system of an automobile, after which field tests were performed at a roadside area. For the same Niτ used in the lab-scale tests, the effects of the carbon fiber ionizer on increasing PM2.5 %Reduction were mild as 9.4%, 4.0%, and 2.8% when the flow rates were at the second, fourth, and sixth levels, respectively (the face velocities were 0.6, 1.2, and 1.8 m/s, respectively). The PM2.5 %Reduction can be substantially increased by 20–21%, for a higher value of Niτ (=1.0×108 ions s/cm3), which is realized by increasing the power consumption of the carbon fiber ionizer. 相似文献
170.
The migration of particles in free surface flows using the diffusive flux model was investigated. As the free‐surface flows, a planar jet flow and a slot coating flow were chosen. The suspension was assumed to be a Newtonian fluid with a particle concentration dependent viscosity. The governing equations were solved numerically by the finite volume method, and the free‐surface problem was handled by the volume of the fraction model. The result shows that even though the velocity profile is fully developed and becomes flat, the particle distribution never reaches the uniform distribution for both of the cases. It is also shown that the die swell of the free jet is reduced compared to the Newtonian fluid and when the particle loading is 0.5, die contraction is observed. The change in die swell characteristics is purely due to particle migration since the suspension model does not show normal stress differences. © 2010 American Institute of Chemical Engineers AIChE J, 2010 相似文献