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41.
PURPOSE: To evaluate the accuracy of measuring intraocular pressure by handheld non-contact applanation tonometer. METHOD: 58 patients' (113 eyes) intraocular pressure were measured by Keeler, non-contact tonometer and R 900 Goldmann applanation tonometer and the results of measurement of intraocular pressure by the two kinds of tonometers were compared. RESULT: The mean intraocular pressure measured by non-contact is 16.31 +/- 5.59 mmHg and 17.49 +/- 6.13 mmHg (1 mmHg = 0.1333 kPa) by Goldmann applanation tonometer, respectively. There was no statistical significance to be found (P > 0.05) between the two methods. By linear correlation and regression analysis, a positive correlation was found between the two methods (r = 0.8942, b = 0.8154). CONCLUSION: The handheld non-contact tonometer has the same accuracy and reliability of measurement of intraocular pressure comparing with Goldmann applanation tonometer, and it can be used in glaucoma clinic and screening. 相似文献
42.
Four monoalkyl esters of isoalkylphosphonic acids have been studied for the chromatographic separation ofrare earths (RE).The relationship between distribution ratios and acid concentration of the eluants forsamarium and ytterbium has been explored.The characteristics of these extractants loaded onto macroreticularpoly (methyl methacrylate) resin beads for the separation of lanthanum,cerium,praseodymium and neodymiumhave been compared.Among the extractants studied,mono(1-methylheptyl) ester of isooctylphosphonic acidwas found to be the best for RE separation.The acidity for separation is lower than any known P-containingextractants for the same purpose.For instance,with 1.73 mol·L~(-1) nitric acid as eluent,thulium,ytterbium andlutetium can be separated quantitatively.The extractant-loaded resins possess high column efficiency with goodkinetic characteristics.The extraction mechanism was also explored. 相似文献
43.
44.
Yueqi Zhong 《Computer aided design》2006,38(10):1062-1073
This paper introduces a new method of generating 2D flat patterns from a 3D triangulated surface by opening the bending configuration of each winged triangle pair. The flattening can be divided into four steps. First, a 3D triangulated surface is modeled with a mass-spring system that simulates the surface deformation during the flattening. Second, an unwrapping force field is built to drive the mass-spring system to a developable configuration through the numerical integration. Third, a velocity redistribution procedure is initiated to average velocity variances among the particles. Finally, the mass-spring system is forced to collide with a plane, and the final 2D pattern is generated after all the winged triangle pairs are spread onto the colliding plane. To retain the size and area of the original 3D surface, a strain control mechanism is introduced to keep the springs from over-elongation or over-shrinkage at each time step. 相似文献
45.
Sodium sulfonate‐terminated dendritic poly(ester‐amine) (SPEA) was synthesized by sulfonation of acrylic double bond‐terminated dendritic poly(ester‐amine) (APEA) with sodium hydrogen sulfite (NaHSO3) in mixture of diglycol and 2‐butanone under normal pressure. The structure of SPEA was characterized by IR, 1H‐NMR, and elemental analysis. SPEA was water‐soluble. 1.0–40.0% (mass) SPEA aqueous solutions appeared as dilatant fluid. When pH value varied from 1.5 to 12.0, the viscosity of 1–5% (mass) SPEA aqueous solutions changed very small, and the electric conductivity almost kept stable within pH 3.0–10.0. The relationship between the viscosity and the concentration of SPEA water solutions was similar to that of NaCl water solutions. The surface tension of SPEA water solutions was lower than that of polyethylene glycol 2000 water solutions with the same concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
46.
If a low weight percentage of crude fine fillers can improve properties of polymer materials directly without complicated chemical treatment process involved, it will be significant for many industrial applications. Our previous study indicated that a kind of Cancun natural sand could be an effective filler material for polymer composites. In this current work, the epoxy composites reinforced by this kind of natural sand particles were prepared and thermal and mechanical properties of the composites containing up to 5 wt % of the sand particles were characterized. Results showed that the highest flexural strength appears in the epoxy composite containing 1 wt % sand particles. A damage model was used to interpret the flexural properties, which showed an acceptable agreement with the experimental results. The glass transition temperature, high temperature storage modulus, and dimensional stability of the sand/epoxy composites monotonically increased with the addition of the sand particles. The sand particle/epoxy composites also displayed a noticeable enhancement in thermal conductivity. Theoretical analysis showed that in addition to conduction, other heat transport mechanisms played roles in the improved heat transmission through the composites. As a natural porous micron-scale material, Cancun sand has the potential for applications in cost-effective composites with enhanced mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
47.
The effect of current stressing on the reliability of 63Sn37Pb solder joints with Cu pads was investigated at temperatures
of −5 °C and 125 °C up to 600 h. The samples were stressed with 3 A current (6.0 × 102 A/cm2 in the solder joint with diameter of 800 μm and 1.7 × 104 A/cm2 in the Cu trace with cross section area of 35 × 500 μm). The temperatures of the samples and interfacial reaction within
the solder joints were examined. The microstructural change of the solder joints aged at 125 °C without current flow was also
evaluated for comparison. It was confirmed that the current flow could cause the temperature of solder joints to rise rapidly
and remarkably due to accumulation of massive Joule heat generated by the Cu trace. The solder joints stressed at 125 °C with
3 A current had an extensive growth of Cu6Sn5 and Cu3Sn intermetallic compounds (IMC) at both top and bottom solder-to-pad interfaces. It was a direct result of accelerated aging
rather than an electromigration or thermomigration effect in this experiment. The kinetic is believed to be bulk diffusion
controlled solid-state reaction, irrespective of the electron flow direction. When stressed at −5 °C with 3 A current, no
significant change in microstructure and composition of the solder joints had occurred due to a very low diffusivity of the
atoms as most Joule heat was eliminated at low temperature. The IMC evolution of the solder joints aged at 125 °C exhibited
a subparabolic growth behavior, which is presumed to be a combined mechanism of grain boundary diffusion and bulk diffusion.
This is mainly ascribed to the retardant effect against the diffusion course by the sufficiently thick IMC layer that was
initially formed during the reflow soldering. 相似文献
48.
49.
Piezoelectric Nanogenerators for Self-Powered Nanodevices 总被引:1,自引:0,他引:1
A novel approach converts nanoscale mechanical energy into electric energy for self-powering nanodevices.In our own work, we've used piezoelectric zinc-oxide nanowire (ZnO NW) arrays to demonstrate a novel approach for converting nanoscale mechanical energy into electric energy. Here, we review the fundamental principle behind the nanogenerator, present an approach for improving its performance, and discuss some of the challenges we face in pushing this technology to reach its potential. 相似文献
50.
以塔河减压渣油(简称塔河减渣)为原料,在实验室小型试验装置和中型连续试验装置上,对在较高温度条件下催化临氢热转化加工塔河减渣的工艺操作条件及改质效果进行了系统研究。采用高分散的油溶性催化剂,在高压釜反应器中考察了反应温度、反应压力、催化剂添加量、溶剂油添加量、反应时间以及助剂添加量对塔河减渣催化临氢热转化反应的转化率和缩合率的影响,优化了操作参数。在优化的操作条件下,进行了塔河减渣催化临氢热转化中型试验,得到初馏点大于524 ℃组分的裂化率为85.2%,馏分油收率为80%,金属(Ni+V)和沥青质脱除率均大于90%。 相似文献