全文获取类型
收费全文 | 1485篇 |
免费 | 159篇 |
国内免费 | 151篇 |
专业分类
电工技术 | 151篇 |
综合类 | 193篇 |
化学工业 | 174篇 |
金属工艺 | 82篇 |
机械仪表 | 105篇 |
建筑科学 | 122篇 |
矿业工程 | 50篇 |
能源动力 | 46篇 |
轻工业 | 63篇 |
水利工程 | 43篇 |
石油天然气 | 37篇 |
武器工业 | 15篇 |
无线电 | 149篇 |
一般工业技术 | 139篇 |
冶金工业 | 89篇 |
原子能技术 | 20篇 |
自动化技术 | 317篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 46篇 |
2021年 | 50篇 |
2020年 | 36篇 |
2019年 | 44篇 |
2018年 | 40篇 |
2017年 | 42篇 |
2016年 | 46篇 |
2015年 | 64篇 |
2014年 | 102篇 |
2013年 | 87篇 |
2012年 | 98篇 |
2011年 | 107篇 |
2010年 | 106篇 |
2009年 | 97篇 |
2008年 | 90篇 |
2007年 | 107篇 |
2006年 | 89篇 |
2005年 | 68篇 |
2004年 | 52篇 |
2003年 | 59篇 |
2002年 | 51篇 |
2001年 | 39篇 |
2000年 | 45篇 |
1999年 | 43篇 |
1998年 | 25篇 |
1997年 | 21篇 |
1996年 | 13篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1980年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有1795条查询结果,搜索用时 15 毫秒
101.
102.
杨淑荣 《山东轻工业学院学报》1993,7(3):17-20
本文从镧系的电子结构和化学键参数分析了镧系元素性质遂变的双峰现象的本质。并探讨了它在稀土分离提取工艺方面应用的可能性。 相似文献
103.
Mitsuaki Nakano 《Electrical Engineering in Japan》1994,114(4):1-12
The contributions of the electrohydrodynamic (EHD) motion to the dc electric conduction in insulating oils are presented. The effects of solid/liquid interfaces on the EHD motion have been studied with a mineral oil-polypropylene mixed dielectric and a mineral oil single dielectric. The time dependence of current, schlieren images of EHD motion induced in the oil layer and response signals of density change in the vicinity of the electrode/oil interfaces after application of step voltage are observed. The results are as follows: (1) the EHD motion occurs at the positive electrode/oil interfaces when a voltage above critical voltage is applied; (2) a time delay exists between the application of step voltage and the onset of EHD motion. The time is inversely proportional to the applied voltage; (3) the EHD motion increases current and produces a peak phenomena in the current waveform; and (4) the time difference between peak current time and the delay time is inversely proportional to applied voltage. 相似文献
104.
105.
The single phase Hg-1223 cuprate superconductors have been successfully fabricated. The postannealing treatment under oxygen (O2) gas and argon (Ar) gas with different annealing time was performed in order to obtain various hole density samples. These samples were used to study the pseudogap phenomenon in the normal phase. With the plot of ln[1/(T) – 1/N(T)] against 1/T, three characteristic temperatures T*, T
S, and T
F were obtained, which describe the role of the pseudogap phenomenon. The magnitudes of the pseudogap were extracted from the slope of the stated plots. It is found that the three characteristic temperatures T*, T
S, and T
F change with the hole density linearly. The relationship between T* and T
C goes within T* = T*op+0 (1–TC/Tmax
C)
, where T*op and T
C
max are the pseudogap opening temperature and the critical temperature for the optimal sample. It is also found that the pseudogap phenomenon only exists below the optimal regime in the hole doping phase diagram. 相似文献
106.
Anne Gelb 《Journal of scientific computing》2007,30(3):409-440
Spectral series expansions of piecewise smooth functions are known to yield poor results, with spurious oscillations forming
near the jump discontinuities and reduced convergence throughout the interval of approximation. The spectral reprojection
method, most notably the Gegenbauer reconstruction method, can restore exponential convergence to piecewise smooth function
approximations from their (pseudo-)spectral coefficients. Difficulties may arise due to numerical robustness and ill-conditioning
of the reprojection basis polynomials, however. This paper considers non-classical orthogonal polynomials as reprojection
bases for a general order (finite or spectral) reconstruction of piecewise smooth functions. Furthermore, when the given data
are discrete grid point values, the reprojection polynomials are constructed to be orthogonal in the discrete sense, rather
than by the usual continuous inner product. No calculation of optimal quadrature points is therefore needed. This adaptation
suggests a method to approximate piecewise smooth functions from discrete non-uniform data, and results in a one-dimensional
approximation that is accurate and numerically robust.
相似文献
107.
基于MNF和SVM的高光谱遥感影像分类研究 总被引:3,自引:0,他引:3
通过分析高光谱遥感影像分类的现状及遇到的困难,以OMIS1高光谱数据为实验数据,提出了基于最小噪声分离(Minimum Noise Fraction-MNF)变换和支持向量机(Support Vector Machine-SVM)的高光谱遥感影像分类方法。分类实验结果表明:与传统的最大似然分类法(Maxi mum Likelihood Classification-MLC)比较,该方法克服了Hughes现象,分类速度得以提高,总体分类精度达到94.85%,从而表明了该方法用于高光谱遥感影像分类的实用性和优越性。 相似文献
108.
Varying-coefficient models are popular multivariate nonparametric fitting techniques. When all coefficient functions in a varying-coefficient model share the same smoothing variable, inference tools available include the F-test, the sieve empirical likelihood ratio test and the generalized likelihood ratio (GLR) test. However, when the coefficient functions have different smoothing variables, these tools cannot be used directly to make inferences on the model because of the differences in the process of estimating the functions. In this paper, the GLR test is extended to models of the latter case by the efficient estimators of these coefficient functions. Under the null hypothesis the new proposed GLR test follows the χ2-distribution asymptotically with scale constant and degree of freedom independent of the nuisance parameters, known as Wilks phenomenon. Further, we have derived its asymptotic power which is shown to achieve the optimal rate of convergence for nonparametric hypothesis testing. A simulation study is conducted to evaluate the test procedure empirically. 相似文献
109.
聚羟基丁酸酯球晶的微观结构及其对力学性能的影响 总被引:1,自引:0,他引:1
本文采用基于数字图像相关计算技术的显微数字分析系统,结合原子力显微镜等,实验研究了晶态高聚物聚羟基丁酸酯(PHB)的细观结构及对其力学性能的影响规律.结果发现:实验用的PHB球晶是台阶式生长或螺旋式生长,其生长台阶高度差在200nm~500nm之间;PHB球晶同心圆环随着结晶温度的提高,同心圆环的环间距增大.球晶结晶度、球晶尺寸对冲击强度、拉伸强度以及断裂伸长率的影响呈线性关系. 相似文献
110.