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51.
Summary A 15-thia- and a 15-nor hexapyrrin derivative were prepared. Their structural features were analyzed by1H-NMR and absorption spectroscopy. All-(Z) configurations and all-syn conformations were found throughout. Carrier mediated transport efficiencies of these compounds in bulk membranes were studied and compared with those of a recently synthesized pentapyrrin-dione and their tripyrrinone partial structure. The pentapyrrin-dione derivative turned out to be one of the most efficient Hg(II) carriers known so far. 相似文献
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干涉型光纤传感器相位生成载波技术研究与改进 总被引:3,自引:3,他引:0
对干涉型光纤传感器的相位生成载波解调技术进行了研究.对PGC算法进行了数学推导和仿真计算,对数字低通滤波器进行了详细分析,给出了其影响PGC解调性能的原因及数字滤波器的设计方法.讨论了传感器干涉光强对PGC算法输出结果的影响,提出了改进的PGC算法,该算法可以有效的实现自动增益控制,消除干涉光强漂移对解调的影响,并大大减小由干涉光强引入的系统噪音;还可以在有限阶数低通滤波器的情况下,极大的增加系统可解调的大信号幅度,提高系统动态范围12 dB以上. 相似文献
54.
Ping Sun 《Optics Communications》2007,275(2):305-310
A fringe carrier method for separating out-of-plane displacement from in-plane components based on large image-shearing electronic speckle pattern interferometry (ESPI) is presented. If the test object is respectively illuminated by two expanded symmetric illuminations in large image-shearing ESPI, two interferometers are formed. Carrier fringe patterns can be introduced by tilting reference surface a small angle. The carrier fringe patterns are demodulated after deformation of the object. Two phase maps, which include out-of-plane and in-plane displacement, can be obtained by using Fourier transform. Then out-of-plane displacement can be easily separated from in-plane displacement by simple operation between two unwrapped phase distributions. The principle of spatial carrier frequency modulation in large image-shearing ESPI is discussed. A typical three-point-bending experiment is completed. Experimental results are offered. The results show that the method offers high visibility of carrier fringes. And the system presented does not need a special beam as a reference light and has simple optical setup. 相似文献
55.
We investigate theoretically the dynamics of three low-order transverse modes in a small-area vertical cavity surface emitting laser. We demonstrate the spontaneous breaking of axial symmetry of the transverse field distribution in such a device. In particular, we show that if the linewidth enhancement factor is sufficiently large dynamical regimes with broken axial symmetry can exist up to very high diffusion coefficients ~ 10 μm2/ns. 相似文献
56.
G. Tamulaitis J. Mickevi
ius P. Vitta A.
ukauskas M.S. Shur Q. Fareed R. Gaska 《Superlattices and Microstructures》2006,40(4-6):274
Results on time-resolved study of GaN photoluminescence (PL) in a power density range from 0.5 mW/cm2 under CW excitation by ultraviolet light emitting diode (UV LED) to 1 GW/cm2 under pulsed excitation by YAG:Nd laser in the temperature range from 8 to 300 K are presented. Measurements of PL response in the frequency domain by using amplitude-modulated emission of a UV LED as well as time-resolved PL measurements using a streak camera and light-induced transient grating technique have been used in the study. Yellow luminescence (YL) intensity increases with increasing temperature up to 120 K and faster components in YL decay switch to slower components with increasing temperature under UV LED excitation. At low carrier densities, the trapping decreases the carrier lifetime below 250 ps, while the carrier lifetime in the same GaN sample under excitation ensuring saturation of the traps equals 2 ns. 相似文献
57.
Sul Lee Sunho Jeong Dongjo Kim Bong Kyun Park Jooho Moon 《Superlattices and Microstructures》2007,42(1-6):361
We have fabricated a solution-processed ZnO thin-film transistor without vacuum deposition. ZnO nanoparticles were prepared by the polyol method from zinc acetate, polyvinyl pyrrolidone, and diethyleneglycol. The solution-processable semiconductor ink was prepared by dispersing the synthesized ZnO in a solvent. Inverted stagger type thin-film transistors were fabricated by spin casting the ZnO ink on the heavily doped Si wafer with 200 nm thick SiO2, followed by evaporation of Cr/Au source and drain electrodes. After the drying and heat treatment at 600 C, a relatively dense ZnO film was obtained. The film characteristics were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). In order to obtain the electrical properties of the solution-derived transistor, the on–off ratio, threshold voltage, and mobility were measured. 相似文献
58.
The transitional isoelectric focusing (IEF) process (the course of pH gradient formation by carrier ampholytes (CAs) and the correlation of the focusing time with CA concentration) were investigated using a whole-column detection capillary isoelectric focusing (CIEF) system. The transitional double-peak phenomenon in IEF was explained as a result of migration of protons from the anodic end and hydroxyl ions from the cathodic end into the separation channel and the higher electric field at both acidic and basic sides of the separation channel. It was observed that focusing times increase logarithmically with CA concentration under a constant applied voltage. The correlation of focusing time with CA concentration was explained by the dependence of the charge-transfer rate on the amount of charged CAs within the separation channel during focusing. 相似文献
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