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91.
The optical behavior of a four-level tripod-type atomic system in a ring resonator driven by a cavity field and two external coherent fields is studied. It is shown that the atomic response exhibits an ultra-sensitive switch from high absorption to nearly transparency by changing the value of one of the control fields. The optical bistable response can be controlled by means of the external fields. The system can flip from the lower to the upper branch of the hysteresis curve without changing the incident probe. Switching and information storage of a light signal are predicted under appropriate triggering of the auxiliary external optical signals. 相似文献
92.
Structural Chemistry - 相似文献
93.
信号源内阻在模拟电路中的作用 总被引:1,自引:0,他引:1
本文从单级放大电路、多级放大电路、负反馈放大电路三个方面,分析了信号源内阻对电路的影响。指出多级放大器输入阻抗应尽量高,输出阻抗应尽量低;串联负反馈信号源内阻越小越好,并联负反馈信号源内阻越大越好。 相似文献
94.
Deposition features of Ni on self-assembled microtubule template from biolipid by electroless method 总被引:1,自引:0,他引:1
FU Yubin ZHANG Lide ZHENG Jiyong FU Shangang & ZHU Mingwei . Institute of Solid State Physics Chinese Academy of Sciences Hefei China . Luoyang Ship Material Research Institute Luoyang China . College of Life Science Henan Normal University Xinxiang China 《中国科学B辑(英文版)》2004,47(3):228-234
The self-assembly of lipid molecules is in close relationship with the structure and function of a cell membrane. A cell membrane has a variety of lipid molecules. Lipid molecules have their amphiphile na-tures, and their self-assembly can form a variety of thermodynamically stable microstructures, such as single-bilayer or multi-bilayer spherical and ellipsoidal liposome, microcylindrical and microtubular struc-tures[1]. These microstructures exhibit different bio-logical functions in living … 相似文献
95.
多电平PWM控制技术发展 总被引:1,自引:0,他引:1
多电平PWM控制技术一直是多电平变换器研究的核心内容之一。基于传统两电平PWM技术研究的经验,经过近十几年的发展,多电平PWM控制技术已形成了儿类不同的实现方法,同时新的控制方法还在涌现。与两电平相比,多电平PWM方法需要面对一些新出现的问题,并拓展PWM控制的内涵,进而形成新的PWM控制思路。按照目前的发展情况,多电平PWM控制方法一般有多电平载波PWM方法、多电平空间矢量PWM方法,以及其他优化的PWM方法。本文对已有多电平PWM控制技术进行了归纳和分析,最后指出多电平空间矢量法和载波调制法在一定条件下具有内在的一敛性。 相似文献
96.
B. Goertzel 《Journal of Optimization Theory and Applications》1992,75(2):423-432
A new approach to the global optimization of functions with extremely rugged graphs is introduced. This multilevel search method is both an algorithm and a meta-algorithm, a logic for regulating optimization done by other algorithms. First, it is examined in the one-dimensional case theoretically and through simple examples. Then, to deal with higher dimensions, multilevel search is combined with the Monte Carlo method; this hybrid algorithm is tested on standard problems and is found to perform extremely well for a derivative-free method. 相似文献
97.
Chien-Sheng Huang Jenq-Gong Duh Yen-Ming Chen Jyh-Hwa Wang 《Journal of Electronic Materials》2003,32(2):89-94
Flip-chip interconnection technology plays a key role in today’s electronics packaging. Understanding the interfacial reactions
between the solder and under-bump metallization (UBM) is, thus, essential. In this study, different thicknesses of electroplated
Ni were used to evaluate the phase transformation between Ni/Cu under-bump metallurgy and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure for the flip-chip technology. Interfacial reaction products varied with reflow times. After the first
reflow, layered (Ni1−x,Cux)3Sn4 was found between solder and Ni. However, there were two interfacial reaction products formed between solders and the UBM
after three or more times reflow. The layered (Ni1−x,Cux)3Sn4 was next to the Ni/Cu UBM. The islandlike (Cu1−y,Niy)6Sn5 intermetallic compound (IMC) could be related to the Ni thickness and reflow times. In addition, the influence of Cu contents
on phase transformation during reflow was also studied. 相似文献
98.
D. N. Kouvatsos V. Ioannou-Sougleridis S. Tsevas F. Christoforou D. Davazoglou C. Boukouras 《Microelectronic Engineering》2003,70(2-4):501-505
MOS diodes having double layer Cu/W, W, or Al gates were fabricated using tungsten chemical vapor deposition, copper evaporation and lift-off and were characterized before and after thermal anneals. The breakdown field statistics were determined for all kinds of devices, while the high field conduction and charge trapping in the oxide were investigated. The W gate devices exhibited high performance and very low degradation even after annealing at 650 °C. In Cu/W gate diodes good barrier action of our LPCVD tungsten films against copper penetration after annealing at 510 °C was observed, while reduced breakdown integrity and degradation due to copper diffusion occurred after annealing at 650 °C. 相似文献
99.
A. P. Schwarzenberger C. A. Ross J. E. Evetts A. L. Greer 《Journal of Electronic Materials》1988,17(5):473-478
Electromigration has reappeared as an important failure mechanism in integrated circuits as metallisation linewidths have
decreased. Electromigration damage forms at sites of atom-flux divergence, of which the two main sources are microstructural
inhomogeneities and local temperature variations (caused for example by track width changes or by nearby active circuits).
We present a study of electromigration in sputter-deposited aluminum test structures with imposed temperature gradients using
two test geometries. One enables the electromigration behaviour of the metallisation to be quickly characterised as a function
of temperature, giving an activation energy; the other allows investigation of the changes in electromigration behaviour for
different imposed temperature gradients. The results obtained are compared with computer modelling of the stress build-up
during electromigration. 相似文献
100.
Wire-Arc Spray Modeling 总被引:5,自引:0,他引:5
A model is presented describing the details of the wire-arc spray process. The model consists of several submodels each treating a different part of the process. A compressible flow model describes the supersonic nozzle flow upstream of the wire tips. The arc is described by a 3-D arc in cross-flow model using different boundary conditions for the cathode and the anode boundary. The resulting temperature and velocity contours serve as upstream boundary for a 2-D turbulent jet model. Particle generation and acceleration is described by treating the initial droplet formation for the anode and the cathode wire separately and then using the resulting particle size and velocity distributions in a secondary break-up model. Comparison with some experimental results show acceptable agreement. This modeling approach may be used for optimization of wire-arc spray equipment. 相似文献