全文获取类型
收费全文 | 101774篇 |
免费 | 8664篇 |
国内免费 | 7046篇 |
学科分类
工业技术 | 117484篇 |
出版年
2024年 | 374篇 |
2023年 | 1856篇 |
2022年 | 4414篇 |
2021年 | 4901篇 |
2020年 | 3174篇 |
2019年 | 2834篇 |
2018年 | 2580篇 |
2017年 | 3216篇 |
2016年 | 3568篇 |
2015年 | 3688篇 |
2014年 | 5269篇 |
2013年 | 5751篇 |
2012年 | 6545篇 |
2011年 | 8145篇 |
2010年 | 5972篇 |
2009年 | 6671篇 |
2008年 | 5924篇 |
2007年 | 6737篇 |
2006年 | 6046篇 |
2005年 | 5070篇 |
2004年 | 4016篇 |
2003年 | 3523篇 |
2002年 | 2865篇 |
2001年 | 2186篇 |
2000年 | 2073篇 |
1999年 | 1737篇 |
1998年 | 1361篇 |
1997年 | 1127篇 |
1996年 | 1066篇 |
1995年 | 890篇 |
1994年 | 815篇 |
1993年 | 603篇 |
1992年 | 483篇 |
1991年 | 410篇 |
1990年 | 320篇 |
1989年 | 250篇 |
1988年 | 172篇 |
1987年 | 135篇 |
1986年 | 154篇 |
1985年 | 88篇 |
1984年 | 83篇 |
1983年 | 53篇 |
1982年 | 71篇 |
1981年 | 47篇 |
1980年 | 60篇 |
1979年 | 48篇 |
1978年 | 17篇 |
1977年 | 22篇 |
1976年 | 21篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
透视图象的三维实体几何复原 总被引:1,自引:0,他引:1
昂海松 《计算机辅助设计与图形学学报》1995,7(1):17-24
对于未知透视参数的图象,如何获得较精确的原实体三维几何构形,本文推导了几个线段逆变换关系式,给出一个有效的方法,实现复杂组合体透视图象的三维重建,文中给出几个实例。 相似文献
72.
在顺丁橡胶后处理生产线上,用处行开发的新型交替运输取代原有运输机。试用结果表明,采用新型交替运输机后,胶块的导向到位率由70%提高到98%;减轻了劳动强度,提出了生产开工率,运行周期可达1a以上。 相似文献
73.
主要研究了CDMA蜂窝通信系统的工作原理,且以基于IS-95标准的前向链路为主。利用MATLAB软件建立了前向链路中各器件的模块,实现了CDMA基带信号发生器,并在时域及频内进行了测量。 相似文献
74.
Preparation and Properties of Sintering Additives Coated Si3N4 from Heterogeneous Nucleation Processing 总被引:1,自引:0,他引:1
The sintering additives such as Al2O3 and /or Y2O3 were coated on the surfaces of Si3N4 particles via heterogeneous nucleation processing using a buffered pH solution as the precipitation reagent .They nucleated and grew only on the surfaces of Si3N4 and did not form sol particles in solution by TEM observation .The isoelectric point(IEP) of coated Si3N4 was different from that of as-received Si3N4.The IEP of Al(OH)3-coated Si3N4 occurred at pH8.4, which is close to that of alumina .When Al(OH)3-coated Si3N4 particles were coated with Y(OH)3,the IEP of coated Si3N4 powder shifted from pH8.4 to pH9.2 ,similar to that of yttria.In addition ,the rheological data showed that Al2O3 and /or Y2O3 coated Si3N4 suspension is nearly Newtonian and that added Si3N4 suspension shows a shear rate thinning behavior. 相似文献
75.
76.
Dimitrios Tzovaras Nikos Grammalidis Michael G. Strintzis 《Signal Processing: Image Communication》1998,11(3):205-230
In the present paper techniques are examined for the coding of the depth map and disparity fields for stereo or multiview image communication applications. It is assumed that both the left and right channels of the multiview image sequence are coded using block- or object-based methods. A dynamic programming algorithm is used to estimate a disparity field between each stereo image pair. Depth is then estimated and occlusions are optionally detected, based on the estimated disparity fields. Spatial interpolation techniques are examined based on the disparity/depth information and the detection of occluded regions using either stereoscopic or trinocular camera configurations. It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver. Various disparity field and depth map coding techniques are then proposed and evaluated, with emphasis given to the quality of the resulting intermediate images at the receiver site. Block-based and wireframe modeling techniques are examined for the coding of isolated depth or disparity map information. Further, 2D and 3D motion compensation techniques are evaluated for the coding of sequences of depth or disparity maps. The motion fields needed may be available as a byproduct of block-based or object-based coding of the intensity images. Experimental results are given for the evaluation of the performance of the proposed coding and spatial interpolation methods. 相似文献
77.
78.
We cloned the Saccharomyces kluyveri HIS3 homolog, k-HIS3, and made a partial deletion of the gene. The k-HIS3 gene complemented a HIS3 deletion in S. cerevisiae. The DNA sequences of the open reading frames (ORFs) of the HIS3 homologs are 70% identical at the DNA level and 83% identical at the deduced amino acid level. The ORF upstream of the k-HIS3 gene is related to the PET56 gene of S. cerevisiae found upstream of the HIS3 gene of S. cerevisiae. The ORF downstream from the k-HIS3 gene is not related to the DED1 gene found downstream of the HIS3 gene in S. cerevisiae. 相似文献
79.
Let us consider n data measurements of a univariate process that have been altered by random errors. We assume that an underlying model function has a substantially smaller number of turning points than the observed ones. We propose algorithms that make least the sum of the moduli of the errors by requiring k monotonic sections, alternately increasing and decreasing, in the sequence of the smoothed values. The main difficulty in this calculation is that the optimal positions of the joins of the monotonic sections have to be found automatically among so many combinations that it is impossible to test each one separately. Moreover, the calculation seems to be very intractable to general optimization techniques because O(nk ) local minima can occur. It is shown that dynamic programming can be used for separating the data into optimal disjoint sections of adjacent data, where each section requires a single L1 monotonic calculation. This procedure is highly efficient, requiring at most O(kn2 ) computer operations and O(n) best L1 monotonic calculations to subranges of data for a global minimum. 相似文献
80.