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151.
The transient switching delay in a micro/nano-scale circuit containing resistive and reactive elements are sternly affected by the surge in the resistance arising from sub-linear current-voltage (I-V) characteristics limited by the velocity and current saturation. The saturation arises due to the realignment of randomly oriented velocity vectors to the unidirectional streamlined ones in a high electric field when voltage applied across a resistor exceeds its decreasing critical value with reduced channel length. The frequency response f = 1/2πτt is affected by a transit time delay τt is lower than that predicted from the application of Ohm’s law. The resistance surge dramatically boosts the RC time constant and switching delay and attenuates the L/R time constant and switching delay. 相似文献
152.
我公司加工刚挠产品时,需用到不流胶与低流胶PP;为保证刚挠产品不缺胶,我们需用缓冲垫以实现压力均匀化。但缓冲垫的使用,会给升温速率及叠层高度带来负面的影响。通过不同缓冲垫的性能比较,选出了一种升温速率快、操作更方便、价格更便宜的缓冲垫;在不影响产品的填胶效果及可靠性能的情况下,将刚挠产品的叠层大幅度提高。 相似文献
153.
154.
In this paper, the mechanical behavior of the scarf lap joints (SLJs) bonded with adhesive (Vinylester Atlac 580) under a tensile load was analyzed. The effects of scarf angle at the interface strain distributions of SLJs were examined. The stress analyses were performed via three dimensional Finite Element Method (3D-FEM). The 3D-FEM code employed was Ansys (12.0). Experimental results were compared with the 3D-FEM results and were found quite reasonable. The results indicated that the maximum values of the normalized εx strain values were determined at θ = 60° in all joints. 相似文献
155.
The paper details the stress characteristics in eccentrically loaded aircraft spliced joints. It is shown that the hoop stress (σθθ) around each rivet is characterized by two peak values located at θ = (0°, 90°). The magnitude of (σθθ) is then reduced to a minimum value between these two peaks. A sharp increase in the axial stress component (σxx) along the vertical splice lines occurs in the vicinity of the rivet centerlines followed by a rapid decrease in the areas between the rivets. It is shown that stresses along the first interior rivet row is the most critical. The axial stress (σxx) profile along horizontal rivet lines has a “sinusoidal” pattern. It is observed that the transverse stress profile (σyy), along the horizontal lines, has different peak and minimum values between the rivets. The magnitude of the peak/minimum values depends upon the line location within the splice region. It is also shown the bending stress component varies significantly and must be accounted for the analysis of the eccentric aircraft joints. Experimental comparisons are made along several lines in the splice region. The numerical model is utilized for analysis of a full frame-bay/splice of aircraft fuselage. The paper provides valuable information that can be utilized by practicing engineers for analysis and design of joints with large number of rivets. 相似文献
156.
Dielectric-breakdown-like forming process in the unipolar resistance switching of Ta2O5−x thin films
Moon Jee YoonShin Buhm Lee Hyang Keun YooSoobin Sinn Bo Soo Kang 《Current Applied Physics》2012,12(3):846-848
We report unipolar resistance switching (URS) in Ta2O5−x thin films. The current increased suddenly when we applied voltages up to 5-7 V to the pristine state of Pt/Ta2O5−x/Pt, Ni/Ta2O5−x/Pt, and Ti/Ta2O5−x/Pt cells. Just after this forming process, we observed a repetitive URS occurring independently of the electrodes. We found that the required voltages for the forming process did not depend on the top electrode type, but on the film thickness. These results suggest that the forming process is driven by a dielectric-breakdown-like phenomenon, and that URS occurs due to the formation and rupture of conducting channels inside the Ta2O5−x thin film. 相似文献
157.
158.
Understanding crack growth in fuselage lap joints 总被引:1,自引:1,他引:0
The problem of multi-site damage and multiple interacting cracks is one experienced by many aircraft manufacturers and operators. This paper focuses on understanding the phenomena, and on developing a predictive capability that can form the engineering framework for maintaining continued airworthiness. To this end the present paper uses a simple formulation based on the Frost–Dugdale crack growth law to study the problem of cracking at fastener holes in fuselage lap joints and shows that the predicted crack growth history is in good agreement with both experimental results and with fleet data. 相似文献
159.
On prestress stiffness analysis of bolt-plate contact assemblies 总被引:1,自引:0,他引:1
Niels Leergaard Pedersen Pauli Pedersen 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(2):75-88
Bolt connections are among the most important connections used in structures. The stiffnesses of the bolt and of the connected
members are the primary qualities that control the lifetime of the connection. The stiffness of the bolt can be estimated
rather easily, in contrast to the member stiffness, but with finite element (FE) and contact analysis, it is possible to find
the stiffness of the member. In the case of many connections and for practical applications, it is not suitable to make a
full FE analysis. The purpose of the present paper is to find simplified expressions for the stiffness of the member, including
the case when the width of the member is limited. The calculation of the stiffness is based on the FE, including the solution
to the contact problem, and we express the stiffness as a function of the elastic energy in the structure, whereby the definition
of the displacements related to the stiffness is circumvented. The contact analysis is performed using a method where iterations
are not necessary, and the results are compared to alternative available results. New practical formulas for the stiffnesses
are suggested. 相似文献
160.
镀金层电子线路用特种焊料应用研究 总被引:1,自引:0,他引:1
概述了镀金层电子线路用特种低温焊料9701型SnPbIn的应用研究和应用效果,该焊料主要解决软钎料对军用电子线路镀金层的焊接溶蚀,即“吃金”问题,同时保证焊料工作温度为-40-120℃,焊接点的抗拉强度≥40Mpa,焊接次数≥10等指标,经大量工艺实验及某产品电子线路镀金层的焊接应用,表明该焊料满足使用要求。 相似文献