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991.
The characteristics of lubricant film at head/disk interface(HDI) are essential to the stability of hard disk drives. In this study, the theoretical models of the lubricant flow and depletion are deduced based on Navier–Stokes(NS) and continuity equations. The air bearing pressure on the surface of the lubrication film is solved by the modified Reynolds equation based on Fukui and Kaneko(FK) model. Then the lubricant film deformations for a plane slider and double-track slider are obtained. The equation of lubricant film thickness is deduced with the consideration of van der Waals force, the air bearing pressure, the surface tension, and the external stresses. The lubricant depletion under heat source is simulated and the effects of different working conditions including initial thickness, flying height and the speed of the disk on lubricant depletion are discussed. The main factors that cause the lubricant flow and depletion are analyzed and the ways to reduce the film thickness deformation are proposed. The simulation results indicate that the shearing stress is the most important factor that causes the thickness deformation and other terms listed in the equation have little influence. The thickness deformation is dependent on the working parameter, and the thermal condition evaporation is the most important factor. 相似文献
992.
Yating Huang Xinchun Lu Guoshun Pan Bill Lee Jianbin Luo 《Applied Surface Science》2009,255(22):9100-9104
Scrub, ultrasonic and megasonic are widely used in industry as post-CMP (chemical mechanical polishing/planarization) cleaning procedure. In this paper experiments and results are described to analyze the particle contaminations of hard disk substrate after each process of post-CMP cleaning. A scatter spot method has been exploited to detect the location and characteristics of the particles. SEM with EDX is used to observe and analyze the particles’ shape and size as well as the elements. The results indicate that brush scrub process can remove 99% contaminations after CMP but not that efficient for submicron particle. Megasonic is a refined method for cleaning nano-particles. However, contaminations like metallic particles and bacteria from the equipment may cause pollution. The abrasive particles embedded in the plating pits cannot be removed by mechanical force. Pollution in the dryer is also discussed. 相似文献
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采用柱型粗糙元,以尖劈和机翼外形为基础,利用CFD数值模拟方法,研究机翼表面局部粗糙区域对其周围气动特性的影响。研究相同粗糙元高度下,粗糙元位于尖劈表面不同位置时局部边界层和气动特性的变化情况;基于流动分区理论,采用空气动力学理论分析与数值模拟结合的方法,分析F16机翼可接受的局部粗糙元高度;根据分析结果,在改进平板外形基础上,验证不同粗糙元高度对改进目标块区域气动特性的影响程度,并给出流经局部粗糙区域的流体发展状况。为了验证数值结果的准确性,采用S-A与SST湍流模型进行对比求解。本文工作对复杂大气环境引起的飞行器局部粗糙表面区域气动特性变化的研究具有指导意义。 相似文献
997.
以碳黑(Vulcan XC-72R)为载体, 硫酸钴(CoSO4 · 7H2O)和吡啶(Py)作为催化剂前躯体, 经溶剂分散及800℃热处理可制备出高效催化氧还原反应(ORR)的碳载钴吡啶复合催化剂(15%Co25%Py/C, 质量分数). 采用红外光谱(IR)和X射线光电子能谱(XPS)等对催化剂的结构进行表征. 运用旋转圆盘电极(RDE)技术研究了不同浓度的KOH溶液(0.05~12.0 mol/L)对CoPy/C催化氧还原活性的影响. 结果表明, 不同浓度的KOH溶液对CoPy/C催化剂催化氧还原反应(ORR)的性能影响很大, 在0.05和0.1 mol/L KOH溶液中催化剂活性最高. 以其制备的气体扩散电极在0.05 mol/L KOH溶液(O2气氛)中的半波电位为-0.138 V, 起峰电位为0.10 V, 同时表现出明显的极限扩散电流. 在-0.381 V时电流密度达到最大值(4.39 mA/cm2). 随着KOH溶液浓度的增加(pH值下降), 起始电压沿负方向移动, 同时动力学、 混合动力学和扩散区的电流密度均下降. RDE研究结果表明, 在0.05和0.1 mol/L KOH溶液中, O2在CoPy/C电极上的还原主要经4e-过程还原成H2O. XPS研究结果表明, 吡啶作为小分子富氮源对提高催化剂的活性具有重要作用, 所制备催化剂经800℃高温热处理形成了石墨N, 吡啶N以及部分氧化态的氮结构, 其中石墨N和吡啶N作为催化剂的活性中心, 提供氧还原活性位, 从而使该类催化剂对氧还原表现出很好的电催化性能和选择性. 相似文献
998.
针对现有微机械(Micromechanical,也称MEMS)圆盘谐振器串联动态电阻过大的问题,该文提出了电极移动法,将其它MEMS器件的可调性能引入MEMS圆盘谐振器,在现有最窄缝隙工艺条件下实现了电极-圆盘缝隙的进一步缩减,降低了串联动态电阻。该文给出了悬置电极的设计方法,推导了电极移动后有效缝隙宽度的表达式,提出了可防电极接触短路的微小圆孔状凹陷设计,并给出了加入凹陷后的有效缝隙宽度表达式。通过ANSYS仿真结果可知,分别加载2.10 V和66.38 V偏置电压后,0.1 m和1 m电极-圆盘缝隙缩小为0.0016 m和0.01 m。对于0.1~1.1 m缝隙谐振器,串联动态电阻变为原来的10-8倍以下。 相似文献
999.
D. Mercuri G. Leone R. Barbucci R. Favaloro A. Facchini F. Signori S. Bronco F. Ciardelli 《Macromolecular Symposia》2008,266(1):74-80
Summary: Degeneration of intervertebral discs is the most common cause of back pain. The first phase of this degenerative process involves the nucleus pulposus. A rapid recovery of this structure can prevent further degradation of the annulus fibrosus. Guar Gum is an hydrophilic polysaccharide extracted from the seed endosperm of a plant. Through a cross-linking procedure a Guar hydrogel was synthesized. The Guar hydrogel could be injected by a syringe and it is a good candidate as a nucleus pulposus substitute. For the preparation of the artificial fibrosus annulus, commercially available polymer materials are tuned to achieve suitable mechanical properties. To achieve this peculiar behaviour, the main strategy investigated is the dispersion of hollow polymer micro spheres in a thermoplastic polymer matrix. Processing conditions and particle content are finely tuned to get the target mechanical behaviour. 相似文献
1000.
Esad Tombarević & Igor Vu&scaron anović 《advances in applied mathematics and mechanics.》2011,3(3):354-369
Phase change in ice-water systems in the geometry of horizontal
cylindrical annulus with constant inner wall temperature and adiabatic
outer wall is modeled with an enthalpy-based mixture model. Solidification
and melting phenomena under different temperature conditions are
analyzed through a sequence of numerical calculations. In the case of freezing
of water, the importance of convection and conduction as well as the influence
of cold pipe temperature on time for the complete solidification is examined.
As for the case of melting of ice, the influence of the inner pipe wall
temperature on the shape of the ice-water interface, the flow and temperature
fields in the liquid, the heat transfer coefficients and the rate of melting
are analyzed. The results of numerical calculations point to good qualitative
agreement with the available experimental and other numerical results. 相似文献