全文获取类型
收费全文 | 11902篇 |
免费 | 118篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 336篇 |
综合类 | 10篇 |
化学工业 | 1087篇 |
金属工艺 | 383篇 |
机械仪表 | 115篇 |
建筑科学 | 84篇 |
能源动力 | 183篇 |
轻工业 | 318篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 422篇 |
一般工业技术 | 705篇 |
冶金工业 | 153篇 |
原子能技术 | 162篇 |
自动化技术 | 8070篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 38篇 |
2021年 | 53篇 |
2020年 | 34篇 |
2019年 | 43篇 |
2018年 | 57篇 |
2017年 | 51篇 |
2016年 | 60篇 |
2015年 | 54篇 |
2014年 | 302篇 |
2013年 | 391篇 |
2012年 | 892篇 |
2011年 | 2481篇 |
2010年 | 1253篇 |
2009年 | 1115篇 |
2008年 | 844篇 |
2007年 | 729篇 |
2006年 | 578篇 |
2005年 | 697篇 |
2004年 | 628篇 |
2003年 | 675篇 |
2002年 | 370篇 |
2001年 | 69篇 |
2000年 | 53篇 |
1999年 | 45篇 |
1998年 | 38篇 |
1997年 | 45篇 |
1996年 | 38篇 |
1995年 | 33篇 |
1994年 | 52篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 20篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 23篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Shingo Urata Hiroyuki Hijiya Kazuhiko Niwano Jun Matsui 《Journal of the American Ceramic Society》2022,105(6):4200-4207
To theoretically explore amorphous materials with a sufficiently low dielectric loss, which are essential for next-generation communication devices, the applicability of a nonequilibrium molecular dynamics simulation employing an external alternating electric field was examined using alkaline silicate glass models. In this method, the dielectric loss is directly evaluated as the phase shift of the dipole moment from the applied electric field. This method enabled us to evaluate the dielectric loss in a wide frequency range from 1 GHz to 10 THz. It was observed that the dielectric loss reaches its maximum at a few THz. The simulation method was found to qualitatively reproduce the effects of alkaline content and alkaline type on the dielectric loss. Furthermore, it reasonably reproduced the effect of mixed alkalines on the dielectric loss, which was observed in our experiments on sodium and/or potassium silicate glasses. Alkaline mixing was thus found to reduce the dielectric loss. 相似文献
2.
3.
Navab SinghAuthor Vitae Moitreyee Mukherjee-RoyAuthor VitaeSohan Singh MehtaAuthor Vitae 《Microelectronics Journal》2003,34(4):237-245
The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging. 相似文献
4.
Reduction of flash generated in a gas vent is of great concern for manufacturers of electronic parts. The present study proposes a theoretical model for flash generation through consideration of flow characteristics in a gas vent. The model predicts the factors controlling flash, i.e., material parameters such as zero‐shear viscosity, crystallization temperature, thermal conductivity, and heat capacity, and process parameters such as injection and mold wall temperatures, packing pressure, and the clearance of a gas vent. On the other hand, we measure the amount of flash generated in the molding of poly(phenylene sulfide) (PPS) composites containing glass fiber and spherical fillers (CaCO3 or Al2O3). Flash reduces with decreasing size of spherical fillers. These experimental data are successfully interpreted using the flash model. Polym. Eng. Sci., 45:198–206, 2005. © 2005 Society of Plastics Engineers 相似文献
5.
In this paper, we present a control methodology for a class of discrete time nonlinear systems that depend on a possibly exogenous scheduling variable. This class of systems consists of an interpolation of nonlinear dynamic equations in strict feedback form, and it may represent systems with a time-varying nonlinear structure. Moreover, this class of systems is able to represent some cases of gain scheduling control, Takagi-Sugeno fuzzy systems, as well as input-output realizations of nonlinear systems which are approximated via localized linearizations. We present two control theorems, one using what we call a “global” approach (akin to traditional backstepping), and a “local” approach, our main result, where backstepping is again used but the control law is an interpolation of local control terms. An aircraft wing rock regulation problem with varying angle of attack is used to illustrate and compare the two approaches. 相似文献
6.
Takeshi Kondo Hiroyuki Ito Kazuhide Kusakabe Kazuhiro Ohkawa Kensuke Honda Yasuaki Einaga Akira Fujishima Takeshi Kawai 《Diamond and Related Materials》2008,17(1):48-54
The effect of CF4 plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)63−/4− was also found to be significantly modified after 10 s of CF4 plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (Cdl) of the electrolyte/CF4 plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF4 plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage. 相似文献
7.
The paper is devoted to the first order delayed linear system with relay output controlled by the proportional-integral (PI) regulator. The deterministic system exhibits stable oscillations, and, since the system itself is stable, it can be suitable to switch off the controller if there are no disturbances during a long time interval. In the present work, the random disturbances are modelled by a Poisson stream of impulses, and the goal is to determine the instants of switching on (off) of the PI controller. After several assumptions and quantization of the time axis, we construct the new optimal control problem which is successfully solved with the help of the dynamic programming approach. 相似文献
8.
9.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
10.
Reset controllers are linear controllers that reset some of their states to zero when their input is zero. We are interested in their feedback connection with linear plants, and in this paper we establish fundamental closed-loop properties including stability and asymptotic tracking. This paper considers more general reset structures than previously considered, allowing for higher-order controllers and partial-state resetting. It gives a testable necessary and sufficient condition for quadratic stability and links it to both uniform bounded-input bounded-state stability and steady-state performance. Unlike previous related research, which includes the study of impulsive differential equations, our stability results require no assumptions on the evolution of reset times. 相似文献