全文获取类型
收费全文 | 3918篇 |
免费 | 649篇 |
国内免费 | 451篇 |
专业分类
化学 | 1898篇 |
晶体学 | 45篇 |
力学 | 270篇 |
综合类 | 26篇 |
数学 | 284篇 |
物理学 | 1139篇 |
无线电 | 1356篇 |
出版年
2024年 | 8篇 |
2023年 | 88篇 |
2022年 | 110篇 |
2021年 | 144篇 |
2020年 | 149篇 |
2019年 | 142篇 |
2018年 | 132篇 |
2017年 | 130篇 |
2016年 | 181篇 |
2015年 | 194篇 |
2014年 | 209篇 |
2013年 | 247篇 |
2012年 | 377篇 |
2011年 | 379篇 |
2010年 | 296篇 |
2009年 | 248篇 |
2008年 | 264篇 |
2007年 | 275篇 |
2006年 | 262篇 |
2005年 | 203篇 |
2004年 | 152篇 |
2003年 | 129篇 |
2002年 | 75篇 |
2001年 | 64篇 |
2000年 | 72篇 |
1999年 | 77篇 |
1998年 | 49篇 |
1997年 | 55篇 |
1996年 | 51篇 |
1995年 | 32篇 |
1994年 | 33篇 |
1993年 | 39篇 |
1992年 | 33篇 |
1991年 | 24篇 |
1990年 | 19篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 17篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有5018条查询结果,搜索用时 890 毫秒
101.
Acta Mathematicae Applicatae Sinica, English Series - A graph is NIC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share at... 相似文献
102.
103.
Jia Mo Zhaofeng Ma Yixian Yang Xinxin Niu 《International Journal of Theoretical Physics》2013,52(11):3813-3819
This paper presents a Bell-dual-basis-based quantum watermarking protocol composed of three major algorithms: watermark embedding and extracting and the intercepting test. The first two are completed by using the entanglement swapping property of Bell dual basis and the test is accomplished through IBF protocol to guarantee its bottom security. The watermarking protocol is mainly designed for the protection of digital copyright in the existence of classical information. This design finds that the quality of digital contents is not damaged with its zero-watermark attributes when embedding watermarks. 相似文献
104.
105.
Yi Niu Xiaolin Wu Xiangjun Zhang Guangming Shi 《Journal of Visual Communication and Image Representation》2012,23(7):1144-1157
Resolution upconversion of a degraded image is an ill-posed inverse problem that is even harder than video superresolution due to lack of redundant observations from reference frames. To overcome this difficulty an adaptive 2D piecewise autoregressive (PAR) model is used to strengthen the constraints on the solution of the inverse problem. The PAR model can be fit to local image waveforms by adjusting its parameters. But estimating the model parameters needs the knowledge of the very original high-resolution pixels to be estimated by the model. We resolve this chicken-and-egg dilemma by adaptive nonlinear least-squares joint estimation of both model parameters and original pixels. This non-linear estimation problem is solved by the method of structured total least-squares, constrained by the degradation function (e.g., the point spread function of a camera plus noises) that forms the observed low-resolution image. As such, this work offers a unified general framework for joint upsampling, deconvolution, and denoising. Moreover, the upsampling can be carried out at an arbitrary scale rather than power of two. Experiments show that the proposed NEARU technique outperforms current methods in both PSNR and subjective visual quality, and its advantage becomes greater for larger scaling factors. 相似文献
106.
107.
108.
109.
110.