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991.
Jian Guo Li Fang Jiao HuaTang Yuan Li Qin Wang Hai Xia Li Ming Zhang Yong Mei Wang 《Electrochimica acta》2006,51(28):6275-6280
Layered Li[Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Crx]O2 materials with x = 0, 0.01, 0.02, 0.03, 0.05 are prepared by a solid-state pyrolysis method. The oxide compounds were calcined with various Cr-doped contents, which result in greater difference in morphological (shape, particle size and specific surface area) and the electrochemical (first charge profile, reversible capacity and rate capability) differences. The Li[Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Crx]O2 powders were characterized by means of X-ray diffraction (XRD), charge/discharge cycling, cyclic voltammetry, and SEM. XRD experiment revealed that the Li[Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Crx]O2 (x = 0, 0.01, 0.02, 0.03, 0.05) were crystallized to well layered -NaFeO2 structure. The first specific discharge capacity and coulombic efficiency of the electrode of Cr-doped materials were higher than that of pristine material. When x = 0.02, the sample showed the highest first discharge capacity of 241.9 mAh g−1 at a current density of 30 mA g−1 in the voltage range 2.3–4.6 V, and the Cr-doped samples exhibited higher discharge capacity and better cycleability under medium and high current densities at room temperature. 相似文献
992.
Laura Pascual 《Electrochimica acta》2006,51(16):3193-3201
Lithium-deficient LiYMn2O4 spinels (LD-LiYMn2O4) with nominal composition (0.9 ≤ Y < 1) have been synthesized by melt impregnation from Mn2O3 and LiNO3 at temperatures ranging from 700 °C to 850 °C. X-ray diffraction data show that LD-LiYMn2O4 spinels are obtained as single phases in the range Y = 0.975-1 at 700 °C and 750 °C. Morphological characterization by transmission electron microscopy shows that the particle size of LD-LiYMn2O4 spinels increases on decreasing the Li-content. The influence of the Li-content and the synthesis temperature on the thermal and electrochemical behaviours has been systematically studied. Thermal analysis studies indicate that the temperature of the first thermal effect in the differential thermal analysis (DTA)/thermogravimetric (TG) curves, TC1, linearly increases on decreasing the Li-content. The electrochemical properties of LD-LiYMn2O4 spinels, determined by galvanostatic cycling, notably change with the synthesis conditions. So, the first discharge capacity, Qdisch., at C rate increases on rising the Li-content and the synthesis temperature. The sample Li0.975Mn2O4 synthesized at 700 °C has a Qdisch. = 123 mAh g−1 and a capacity retention of 99.77% per cycle. This LD-LiYMn2O4 sample had the best electrochemical characteristics of the series. 相似文献
993.
Yuji Tatemoto Masaya Tsunekawa Shuji Yano Takenari Takeshita Katsuji Noda 《Chemical engineering science》2007,62(8):2187-2197
A relatively large wet material was immersed in a fluidized bed of hygroscopic porous particle (silica gel beads) under reduced pressure. And then the drying characteristics were compared with those in the case of inert particle (glass beads). The comparison of drying characteristics is performed experimentally and theoretically. In calculation, the water transfer from the sample to the fluidized bed was considered. The calculation results are in good agreement with the experimental data. The effects of the operational conditions (the pressure in the drying chamber and the temperature of the drying gas) on the drying characteristics were also examined in both fluidizing particles.The drying finishes earlier in the case of hygroscopic porous particle than in the case of inert particle regardless of pressure in the drying chamber, since the water transfer from the sample facilitates the drying in the case of hygroscopic porous particles. The temperature decrement in drying appears in the case of inert particle. This phenomenon is also observed in the case of hygroscopic porous particle, but the decrement degree of the temperature is much smaller than that in the case of inert particle. The difference of the minimum temperature in the sample in drying between the cases of hygroscopic porous particle and inert particle is very slight for different pressures in the drying chamber. 相似文献
994.
Kazuhiko Takeuchi Taka-aki Hanaoka Takehiko Matsuzaki Matti Reinikainen Yoshihiro Sugi 《Catalysis Letters》1991,8(2-4):253-261
Vapor phase hydroformylation of ethylene was studied with silica-supported metal catalysts. A cobalt metal catalyst derived from Co2(CO)8 gave propanal and its derivatives in as high selectivity of about 36% as Rh/SiO2 catalyst under the reaction conditions of 1.1 MPa of a gas-mixture of ArCOC2H4H2 = 1333 at 423–503 K. On the other hand, conventional cobalt catalysts derived from cobalt nitrate, chloride, or acetate, and other noble metal catalysts (Pd/SiO2 and Ir/SiO2) produced mainly ethane. 相似文献
995.
Interaction of a High‐Velocity Steel Projectile with a High‐Porous Copper–Duralumin Two‐Layer Bumper
P. V. Lavrukhov A. V. Plastinin V. V. Sil'vestrov 《Combustion, Explosion, and Shock Waves》2004,40(3):328-337
The impact of a steel sphere 2 mm in diameter flying with a velocity of 2–7.3 km/sec on a twolayer bumper is considered. The first layer of the bumper is made of finely disperse copper powder with a density of 2.8 g/cm3, and the second layer is made of Duralumin. For identical impact velocities of 3–5 km/sec and identical thicknesses and areal densities of the bumpers, the twolayer bumper leads to better failure of the steel projectile than the Duralumin bumper. In the case of the twolayer bumper used, the maximum penetration depth of fragments into the witness plate and the number of the largest craters are smaller. The order of the bumper layers does not exert any noticeable effect on projectile failure. With the impact velocity increased to 7 km/sec, the difference in shielding properties of the bumpers almost vanishes. 相似文献
996.
Synthesis of highly crystalline spinel LiMn2O4 by a soft chemical route and its electrochemical performance 总被引:1,自引:0,他引:1
Highly crystalline spinel LiMn2O4 was successfully synthesized by annealing lithiated MnO2 at a relative low temperature of 600 °C, in which the lithiated MnO2 was prepared by chemical lithiation of the electrolytic manganese dioxide (EMD) and LiI. The LiI/MnO2 ratio and the annealing temperature were optimized to obtain the pure phase LiMn2O4. With the LiI/MnO2 molar ratio of 0.75, and annealing temperature of 600 °C, the resulting compounds showed a high initial discharge capacity of 127 mAh g−1 at a current rate of 40 mAh g−1. Moreover, it exhibited excellent cycling and high rate capability, maintaining 90% of its initial capacity after 100 charge-discharge cycles, at a discharge rate of 5 C, it kept more than 85% of the reversible capacity compared with that of 0.1 C. 相似文献
997.
Henri Berthiaux Antonio Guttierrez Lavin Julio Bueno De Las Heras Marisol Muñiz Alvarez 《加拿大化工杂志》2007,85(2):158-170
Despite of its general use in industry, particle sedimentation is still a not well understood unit operation. Hydrodynamics is complex in essence, mainly because the possible volumes are depending on the operating conditions, which in turn has consequences on the stability of the equipment in unsteady state conditions. 相似文献
998.
G. Nelissen B. Van Den Bossche J. Deconinck A. Van Theemsche C. Dan 《Journal of Applied Electrochemistry》2003,33(10):863-873
Laminar and turbulent mass transfer in a parallel plate reactor at high Schmidt number obtained from numerical simulation is compared with literature data. In a first step, the fluid flow is determined numerically in the reactor by solving the Navier–Stokes equations. For turbulent flow, a low Reynolds number k— model is used to calculate the turbulent viscosity. Using the obtained flow field and turbulent viscosity, the current density distribution is calculated for different flow velocities by solving the equations describing the transport of multiple ions due to diffusion, convection and migration. For the laminar case, a very good agreement with literature data is obtained. For turbulent flow, different numerical models for turbulent mass transfer are proposed in the literature. A detailed study of the behaviour close to the wall of these different turbulence models is presented, together with a comparison of the calculated results with literature correlations. This allows identification of the benefits and disadvantages of each of the turbulence models for the numerical calculation of mass transfer at high Schmidt numbers in a parallel plate reactor. 相似文献
999.
ABSTRACT Cadmium as a highly toxic metal is released into the environment through paper production, metal processing, phosphate fertilizers, insecticides, and treatment of wastewater. Cadmium also inhibits the body activities and is very toxic for kidney and other organisms. In the current study, zinc-based metal–organic framework, zeolitic imidazolate framework (ZIF)-8, was synthesized and modified by dimethylethylenediamine (ZIF-8-mmen) for the removal of cadmium. To optimize the experiments, response surface methodology was applied with three variables including pH, adsorbent dosage, and contact time using central composite design. The optimum conditions for pH, dosage, and time were 2, 0.1 g, and 89 min, respectively, with removal efficiency of 85.38%. The Langmuir isotherm (q m = 1000 mg/g) indicates the monolayer adsorption. The kinetic studies reveal that the Lagergren model was predominant and cadmium was not chemisorbed. Thermodynamic parameters show spontaneous, endothermic, and physisorption processes. 相似文献
1000.
模拟原子跃迁反演法源于原子物理学,它模拟了物理学中原子从激发态向基态跃迁的物理过程。模拟原子跃迁反演算法的基本思想是:将地球物理反演理论中的反演目标函数生成目标能级函数,然后通过能级跃迁过程使模拟的系统最终达到系统能级最小值的过程。模拟原子跃迁反演法是利用了地球物理反演问题求解过程与原子中能级跃迁过程的相似性建立的一种新的地球物理反演方法。本讲座概要地介绍了模拟原子跃迁法的基本原理、目标能级化过程、能级跃迁、模型搜索及解的接受准则及模拟原子跃迁法的实现过程,并给出了模拟原子跃迁法对典型测试函数和大地电磁资料反演,最后总结和归纳了模拟原子跃迁法的特点。 相似文献