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991.
An electrorheological (ER) response is defined as the dramatic change in rheological properties of a suspension of small particles
due to the application of a large electric field transverse to the direction of flow. ER fluids are typically composed of
nonconducting or semiconducting particles dispersed in a nonconducting continuous phase. A sufficiently large electric field
will cause ER fluids to solidify, giving rising to a yield stress. Many applications in torque and stress transfer devices
were proposed employing the reversible yielding behavior of ER fluids. Successful applications depend on a large yield stress
of ER fluids and therefore accurate measurements of the yield stress of ER fluids are required. Reported experimental yield
stresses of ER fluids have been dynamic yield stresses obtained by extrapolating the shear stress–shear rate data to zero-shear
rate. It would be very helpful to the understanding of ER behaviors and the applications of ER fluids to be able to measure
the static yield stress of ER fluids accurately. The slotted plate technique has been shown to be a successful method to determine
the static yield stress of suspensions. The values obtained via the slotted plate method are static yield stress as the platform
is designed for extremely low-speed motion. In this study, we modified the slotted plate device for the application of large
electric fields and measured the static yield stress of TiO2 ER fluids under various electric fields. The measured static yield stress values are also compared with the static yield
stress values from a commercial rheometer. 相似文献
992.
含局部焊接细节的钢桁架结构静动力响应实验研究 总被引:1,自引:0,他引:1
从考虑损伤的结构有限元模拟的研究需要出发,对考虑焊连接细节构造的钢桁架结构试样进行了结构动力特性及特定载荷下的静力响应实验研究。文中给出了对试样结构进行动力特性测试和结构整体与局部应力分布状态的测试结果及其分析,并将有限元计算的结果与测试结果进行了对比分析。研究结果表明:结构动力特性的计算结果和测试值比较接近,存在的误差主要来自于边界条件的不确定性和可能的材料不均匀性;边界约束的形式对结构名义应力的分布有明显的影响,但对于焊接细节处的热点应力分布的影响很小。实验中所关注部位的热点应力在均布载荷作用下随载荷级别的提高,应力值由下翼缘的中间向两边增大,在焊缝附近有应力突变。 相似文献
993.
采用数值模拟和实验测试技术对两种不同内固定法的腰椎模型进行应力和变形分析,基于CT图像建立L4-S1的三维数值模型,经ANSYS计算分析得出五种工况下的终板应力值;在实验中采用了一种薄膜压力测试传感器结合图像处理的方法,提高测试椎间盘压力分布的精度;同时采用数字图像相关技术对腰椎骨上下关节突在承载情况下的空间位移进行了测量,获得了腰椎间盘(L3-L4)在承受轴压、前屈后伸和侧弯情况下的压力分布,以及对应的关节突的位移迹线。结果表明:本研究采用的数值分析技术和实验开发的测试技术可操作性强,精度满足要求,有望在类似的生物力学分析中得到应用。 相似文献
994.
大攻角运动时的机翼摇滚问题研究综述 总被引:1,自引:0,他引:1
机翼摇滚是现代战斗机、导弹设计中普遍遇到的横向不稳定现象之一,属于典型的大攻角动态特性问题. 20多年来,机翼摇滚问题在国内外航空工业界、学术界都引起了极大的重视和兴趣,并在实(试)验、计算方面发表了许多文章,对机翼摇滚问题的认识也取得了较大的进展.本文对自1981年Nguyen、Yip及Chambers最早研究机翼摇滚现象以来,在该问题研究方面的近100多篇有代表性的论文进行了综述,内容涉及实(试)验研究、计算研究的各个方面,并对今后的发展趋势提出了自己的看法. 相似文献
995.
自动控制中弹性器件的弹力计算方法 总被引:1,自引:0,他引:1
基于能量守恒定律,推导出一种弹力的简单计算方法.该方法适用于电气自动控制过程中作为执行器件的线性和非线性弹性器件.考虑到自动控制过程中需要对器件能否产生弹力进行判断,特提出判定方法.举出实例对器件的弹力进行了分析和计算. 相似文献
996.
Dias Maristella A. Rosa Carlos A. Linardi Valter R. Conte Rosa A. De Castro Heizir F. 《Applied biochemistry and biotechnology》2001,91(1-9):413-422
A full factorial design leading to 20 sets of sorption runs was conducted to study the influence of four variables (bleaching
earth and biomass concentrations, pH, and sorption time) on the iron, nickel, and chromium removal from stainless steel effluent
using waste biomass from a beverage industry. Similar factor effects and interactions were found for each metalinvolved in
this biosorption study, and the main factors were pH (positive effect) and biomass concentration (negative effect). Response
surface methodology was adopted and an empirical linear polynomial model constructed on the basis of the specific uptake (mg
of metal/g of biomass as dry weight) for each metal species. Under optimized process conditions (pH 4.0, biomass concentration
of 2.0 g/L, absence of Celite), uptake values of 155 mg of Fe/g, 38 mg of Cr/g, and 0.4 mg of Ni/g were achieved after 3 h.
This corresponded to a reduction in heavy metals concentration of approx 94% for Cr, 57% for Fe, and 25% for Ni. 相似文献
997.
A solid state ionic device to titrate electrolytes in water was produced, and the performance of the device was examined. The device named the coulometric titration apparatus is a three-component electrochemical cell like an electrodialyzer. The central component, the analyzing room, is a container of the sample solution. The sample solution, 10−1 M H2SO4, NaOH, Na2SO4, or 10−7–10−2 M Na2SO4, is separated from the cathode and the anode room solutions, 10−2 M H2SO4, NaOH, or Na2SO4, by Nafion-117 and Tosflex IE-SF34 membranes working as the anion and the cation blocking electrodes, respectively. The quantity of electricity to extract whole electrolytes in the sample solution is evaluated from the peak area of the titration curve. The sample concentration is successfully determined by the calibration curve method, with the quantity of electricity and the sample volume (6 ml) in the range from 10−1 to 10−5 M. 相似文献
998.
用激光等离子体相互作用对天体物理过程进行模拟研究已成为当前世界物理和天文学家深感兴趣的重要前沿领域 .文章比较了强激光作用下产生的等离子体与天体物理条件下的等离子体之间在内部物理过程的相似性 ,论述了由前者模拟后者的物理依据 ,即相似性原则和定标规律 .在此基础上 ,回顾和评述了当前已经在高离化态光谱学、类天体等离子体状态方程和辐射不透明度以及流体动力学不稳定性等方面开展的强激光天体物理学的研究 ,这些研究对于理解超新星、白矮星、中子星以及巨行星、褐矮星等领域的天体物理过程起到了极大的作用 ,并正在成为联系天体物理理论模拟和观测的中间桥梁 相似文献
999.
M. Podt A. J. Mieog J. Flokstra H. Rogalla 《Physica C: Superconductivity and its Applications》2001,350(3-4):193-200
A digital superconducting quantum interference device (SQUID) has the potential for a very large dynamic range and a very high slew rate. Our concept of the digital SQUID consists of a double relaxation oscillation SQUID (DROS) with the complete flux locked loop (FLL) electronics on one single chip. The key element of the FLL circuitry is a superconducting up-down counter, which supplies the feedback flux to the DROS. In this paper we will concentrate on the numerical simulations of our new 100 MHz smart DROS. In this new design, the quantization unit of the feedback flux, δΦfb=52 mΦ0, was optimized with respect to the flux noise of the DROS. By doing so, the flux slew rate was maximized without compromising the sensitivity. The optimization resulted in a maximum flux slew rate of δΦsig/δt=5×106Φ0/s. 相似文献
1000.
K. Yu. Platov A. M. Klushin M. Yu. Kupriyanov M. Siegel 《Physica C: Superconductivity and its Applications》2001,350(3-4):302-308
A new coupling scheme of the external microwave signal for a digital-to-analog converter based on series arrays of high-temperature superconducting Josephson junctions has been proposed. It is suggested to couple the meander-like array inductively to a parallel microwave transmission line. Within the resistively shunted junction model different types of microwave coupling structures were analyzed with the goal to reduce the mutual phase locking and to achieve high output power and phase-locking stability. A harmonic balance technique was used to derive an analytic expression connecting the amplitudes of microwave voltages and currents in the array and the frequency of the external signal. Numerical simulations were performed to determine the boundaries of stable locking as a function of circuit parameters. 相似文献