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   957篇
  免费   7篇
  国内免费   1篇
电工技术   52篇
化学工业   232篇
金属工艺   21篇
机械仪表   12篇
建筑科学   12篇
能源动力   39篇
轻工业   47篇
水利工程   1篇
石油天然气   4篇
无线电   95篇
一般工业技术   142篇
冶金工业   206篇
原子能技术   19篇
自动化技术   83篇
  2024年   3篇
  2023年   7篇
  2022年   9篇
  2021年   18篇
  2020年   11篇
  2019年   15篇
  2018年   13篇
  2017年   13篇
  2016年   8篇
  2015年   12篇
  2014年   32篇
  2013年   36篇
  2012年   25篇
  2011年   39篇
  2010年   31篇
  2009年   39篇
  2008年   40篇
  2007年   29篇
  2006年   28篇
  2005年   30篇
  2004年   22篇
  2003年   27篇
  2002年   17篇
  2001年   18篇
  2000年   22篇
  1999年   23篇
  1998年   81篇
  1997年   52篇
  1996年   47篇
  1995年   20篇
  1994年   26篇
  1993年   25篇
  1992年   10篇
  1991年   7篇
  1990年   12篇
  1989年   13篇
  1988年   8篇
  1987年   4篇
  1986年   11篇
  1985年   10篇
  1984年   10篇
  1983年   6篇
  1982年   10篇
  1981年   8篇
  1980年   6篇
  1979年   4篇
  1978年   4篇
  1977年   5篇
  1976年   7篇
  1975年   5篇
排序方式: 共有965条查询结果,搜索用时 0 毫秒
91.
Kolmogorov introduced the concept of -entropy to analyze information in classical continuous systems. The fractal dimension of a geometric set was introduced by Mandelbrot as a new criterion to analyze the geometric complexity of the set. The -entropy and the fractal dimension of a state in a general quantum system were introduced by one of the present authors (MO) in order to characterize chaotic properties of general states.In this paper, we show that -entropy of a state includes Kolmogorov's -entropy, and that the fractal dimension of a state describes fractal structure of Gaussian measures.  相似文献   
92.
Recently, the simulated annealing has been applied to several combinatorial optimization problems. In this paper, the simulated annealing method for continuous functions is reviewed, and it is applied to an economic model having multiple optimal solutions, in which all optimal solutions cannot be simultaneously obtained by Scarf's algorithm.  相似文献   
93.
The implementation on the vector processor of Incomplete LU factorization in the Preconditioned Conjugate Gradient method and other Preconditioned CG-like methods for the numerical solutions of the partial differential equations is discussed. For sufficient vectorization, a variant of the standard 5-point difference scheme for 2-dimensional problems is introduced. The convergence property of ILU factorization for this variant is examined in comparison with that vectorized with the usual hyperplane ordering method for the standard 5-point difference scheme on the vector processor. The efficiency and effectiveness of this factorization for the variant of the difference scheme is demonstrated through several computational experiments.  相似文献   
94.
Bit-patterned media (BPM) consisting of land parts for read/writing and grooves, which are almost filled with non-magnetic materials to prevent magnetic interference between recording bits, are considered to be promising media for achieving ultrahigh density recording. A flying head slider flying over a BPM disk suffers from variations in both the spacing and van der Waals (vdW) attractive forces, which induce slider vibrations and spacing fluctuations. In the present study, we considered that BPM disks not only have a groove depth distribution, but that they also have a distribution of material properties (e.g., refractive index), which gives rise to a distribution in the vdW force. In the dynamic responses of sliders with small groove depths and a small variation in the refractive index, spacing fluctuations are found to be a superposition of fluctuations due to slider behaviors (1) over a disk with transverse grooves in a uniform material with a uniform refractive index (Case 1) and (2) over a flat disk with a refractive index distribution (Case 2). When the effects of Cases 1 and 2 cancel each other, the spacing fluctuations for the two cases cancel each other, reducing the total spacing fluctuation.  相似文献   
95.
Thermocapillary deformations of an ultra-thin liquid film caused by temperature distribution were three-dimensionally analyzed using the unsteady and linearized long wave equation considering the temperature and film thickness dependence of surface tension. The temperature and film thickness dependence equation for the surface tension of a liquid was firstly established. The temperature dependence of the surface tension was obtained experimentally using a surface tensiometer and the film thickness dependence was obtained theoretically from the corrected van der Waals pressure equation for a symmetric multilayer system. Time evolutions of depression and groove of the ultra-thin liquid film caused by local heating were obtained quantitatively.  相似文献   
96.
Microsystem Technologies - The interaction stresses (pressure and shear stress) for the (001) surface between a half-space consisting of a homogeneous material and a half-space with a spatially...  相似文献   
97.
Consumer's acceptance of tomato juice depends on its sourness to sweetness ratio and measuring this is important for quality control and marketing. Traditional methods destroy the samples, are time consuming and cannot be used in continuous packing or bottling systems. A non‐destructive method of quality evaluation, using near infrared (NIR) techniques, was tested, by using a portable NIR measuring unit. Spectra of tomato juice of known acid and brix values were determined and, in the wavelength range 703–1124 nm (NIR), a calibration model for acid–brix ratio (ABR) was developed, by using unscrambler software. When used to predict ABR of tomato juice statistical analysis showed minimal standard error (0.009) and satisfactorily high correlation coefficients (0.92) over the wavelength range 1059.5–1124.8 nm, for both calibration and prediction. These values were hardly different from analytical results and the NIR model has potential for non‐destructive prediction of ABR of tomato juice.  相似文献   
98.
High-density polyethylene films 50 μm thick were exposed to the downstream plasma flow of RF glow discharges in argon, hydrogen, or oxygen. It was found that many transvinylene and unreacted radicals remain after the argon or hydrogen plasma treatment, and that carbonyl groups are formed in the oxygen plasma treatment. The conduction current was smaller in the hydrogen-plasma treated samples and the samples exposed to oxygen or ozone after hydrogen-plasma treatment than in the untreated samples. Thermal pulse current measurements indicate that the treated surface layer traps electrons or holes and reduces the field strength at the electrode surface, thus suppressing further injection of electrons or holes.  相似文献   
99.
Maru K  Fujiwara T  Ikeuchi R 《Applied optics》2011,50(32):6121-6127
A transverse scanning laser Doppler velocimeter (LDV) that does not require any moving mechanism in its sensor probe is proposed, and the scanning function is demonstrated theoretically and experimentally. In the proposed scanning LDV, the measurement position is transversely scanned on the basis of a wavelength change induced by a tunable laser and a combination of a grating and a Dove prism. To demonstrate the scanning function in the transverse direction, an experiment was carried out using a setup of the sensor probe consisting of bulk optical components. The experimental results indicate that a transverse scanning function was successfully obtained. The scanning range in the vertical direction is estimated to be 11.3 mm over wavelengths of 1520 to 1570 nm.  相似文献   
100.
    
Li–S batteries have attracted attention as the next-generation secondary batteries. While substantial progress is made in understanding Li–S chemistry at a fundamental level, only a limited number of studies are dedicated to achieving high energy density at the practical pouch cell level. The challenge lies in attaining high-energy-density Li–S batteries under harsh conditions, which involve a minimal amount of electrolyte and a relatively high areal S-loading cathode. This discrepancy creates a substantial gap between fundamental material research and comprehensive cell-level investigations. In this study, it is investigated how the morphology and properties of two carbon materials, namely Ketjen black (KB) and mesoporous carbon nano-dendrites (MCND), influence the composite cathode architecture and determine the performance of Li–S batteries. Unlike KB, MCND allows for a higher sulfur-loading cathode without evident cracks in the composite cathode. This achievement can be attributed to the high porosity, excellent wettability, and high conductivity exhibited during an identical electrode preparation procedure. Furthermore, large-format Li–S pouch cells incorporating MCND/S cathodes are successfully fabricated. These cells demonstrate an energy density surpassing 250 Wh kg−1 and an initial discharge capacity of 3.7 Ah under challenging conditions (S-loading > 5 mg cm−2 and E/S < 3.5 µL mg−1).  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