首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15067篇
  免费   455篇
  国内免费   500篇
教育   10578篇
科学研究   2359篇
各国文化   110篇
体育   776篇
综合类   922篇
文化理论   24篇
信息传播   1253篇
  2024年   9篇
  2023年   106篇
  2022年   162篇
  2021年   326篇
  2020年   461篇
  2019年   400篇
  2018年   335篇
  2017年   339篇
  2016年   394篇
  2015年   456篇
  2014年   513篇
  2013年   1095篇
  2012年   1107篇
  2011年   1093篇
  2010年   607篇
  2009年   733篇
  2008年   1006篇
  2007年   1186篇
  2006年   1253篇
  2005年   1054篇
  2004年   892篇
  2003年   689篇
  2002年   515篇
  2001年   352篇
  2000年   278篇
  1999年   147篇
  1998年   98篇
  1997年   88篇
  1996年   80篇
  1995年   47篇
  1994年   42篇
  1993年   44篇
  1992年   33篇
  1991年   23篇
  1990年   15篇
  1989年   21篇
  1988年   4篇
  1987年   6篇
  1985年   5篇
  1984年   2篇
  1983年   2篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1957年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
211.
Radar cross section (RCS) of non-spherical raindrops is calculated by using the software CST based on finite integral method and compared with RCS of spherical raindrops. The revised factor of non-spherical raindrops is obtained. The radar reflectivity with precipitation change of four distribution models of M-P, Gamma, JD and JT combining the revised factor is gotten using trapezoidal integration. When the influence of non-spherical raindrops is considered, the accuracy of precipitation measurement of four distribution models can be separately improved 8.77%, 8.47%, 10.53% and 8.04% in the case of rain intensity is 100 mm/h.  相似文献   
212.
Amorphous InGaZnO (a-IGZO) films were deposited on the corning eagle XG (EXG) glass substrates using magnetron sputtering method. The structure, surface morphology, electrical and optical properties of these films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), semiconductor parameter analyzer and spectrophotometry, respectively. The influence of oxygen flow on the electrical properties of IGZO thin films was studied, showing that increasing oxygen flow changes the resistivity with six orders of magnitude. The contact resistance of ITO/IGZO is 7.35×10−2 Ω·cm2, which suggests that a good ohmic contact exists between In2O3: Sn (ITO) and IGZO film.  相似文献   
213.
This work investigated the microwave dielectric properties of A-site substitution by rare earth La3+in(Pb0.5Ca0.5)(Fe0.5Ta0.5)O3(PCFT) system.A single perovskite phase was obtained only when the doping content was 2%.Suitable La3+ doping improved microwave dielectric performances.Excessive La3+doping caused the formation of secondary phase,which resulted in the decreasing of permittivity εrand quality factor Qfvalues.Especially,when the doping content is 2%-5%,permittivity εrwas above 75 and Qfvalues were 6...  相似文献   
214.
A novel flat-top and low-dispersion optical interleaver using ring cavities (RCs) in a Mach-Zehnder interferometer (MZI) is proposed. It is composed of eight mirrors and two nested prism pairs. Each prism and the two mirrors behave as a RC. Phase shift of RC is a periodic function of the frequency of the input light which acts as a phase dispersive mirror. The two phase shifts needed to achieve a flat-top spectral passband are provided by Fresnel reffectivities at the prism-air interface of the two RCs. The...  相似文献   
215.
Depth maps are used for synthesis virtual view in free-viewpoint television (FTV) systems.When depth maps are derived using existing depth estimation methods,the depth distortions will cause undesirable artifacts in the synthesized views.To solve this problem,a 3D video quality model base depth maps (D-3DV) for virtual view synthesis and depth map coding in the FTV applications is proposed.First,the relationships between distortions in coded depth map and rendered view are derived.Then,a precisely 3DV quali...  相似文献   
216.
In this paper an overall scheme of the task management system of ternary optical computer (TOC) is proposed, and the software architecture chart is given. The function and accomplishment of each module in the system are described in general. In addition, according to the aforementioned scheme a prototype of TOC task management system is implemented, and the feasibility, rationality and completeness of the scheme are verified via running and testing the prototype.  相似文献   
217.
The core of smoothed particle hydrodynamics (SPH) is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.  相似文献   
218.
Hilbert-Huang transform method has been widely utilized from its inception because of the superiority in varieties of areas. The Hilbert spectrum thus obtained is able to reflect the distribution of the signal energy in a number of scales accurately. In this paper, a novel feature called ECC is proposed via feature extraction of the Hilbert energy spectrum which describes the distribution of the instantaneous energy. The experimental results conspicuously demonstrate that ECC outperforms the traditional short-term average energy. Combination of the ECC with mel frequency cepstral coefficients (MFCC) delineates the distribution of energy in the time domain and frequency domain, and the features of this group achieve a better recognition effect compared with the feature combination of the short-term average energy, pitch and MFCC. Afterwards, further improvements of ECC are developed. TECC is gained by combining ECC with the teager energy operator, and EFCC is obtained by introducing the instantaneous frequency to the energy. In the experiments, seven status of emotion are selected to be recognized and the highest recognition rate 83.57% is achieved within the classification accuracy of boredom reaching 100%. The numerical results indicate that the proposed features ECC, TECC and EFCC can improve the performance of speech emotion recognition substantially.  相似文献   
219.
In this paper, equivalent surface impedance boundary condition (ESIBC), which takes fractal parameters (D, G) into SIBC, is implemented in the 4-component 2-D compact finite difference frequency domain (2-D CFDFD) method to an- alyze the propagation characteristics of lossy circular waveguide with fractal rough surface based on Weierstrass-Mandelbrot (W-M) function. Fractal parameters’ effects on attenuation constant are presented in the 3 mm lossy circular waveguide, and the attenuation constants of the fi...  相似文献   
220.
MV10 is an MCU which consists of PWM,ADC,CAN and some other function blocks.It is designed for car body's control.Advanced peripheral bus (APB) is a low speed AMBA bus connecting low-power peripherals.This paper presents an implementation of APB interface for MV10 MCU.After that,MV10 can be integrated into any AMBA system on chips (SoCs) easily.We have built a multi-core system with ABMA to verify this design.In this system ARM9 is a main processor mounted on AHB and MV10 acts as a low-power and low-speed slaver on APB.Before building this system,some operations are encapsulated into a task with dedicated ID.MV10 works as a co-processor with ARM by acquiring task ID from ARM.The result of simulation indicates that MCU can work well as expected.Based on our design,MV10 can be mounted on any AMBA system from now on.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号