全文获取类型
收费全文 | 12687篇 |
免费 | 917篇 |
国内免费 | 735篇 |
专业分类
化学 | 2570篇 |
晶体学 | 74篇 |
力学 | 1646篇 |
综合类 | 70篇 |
数学 | 591篇 |
物理学 | 2634篇 |
综合类 | 6754篇 |
出版年
2024年 | 36篇 |
2023年 | 107篇 |
2022年 | 208篇 |
2021年 | 226篇 |
2020年 | 301篇 |
2019年 | 205篇 |
2018年 | 252篇 |
2017年 | 292篇 |
2016年 | 370篇 |
2015年 | 401篇 |
2014年 | 648篇 |
2013年 | 588篇 |
2012年 | 604篇 |
2011年 | 740篇 |
2010年 | 570篇 |
2009年 | 686篇 |
2008年 | 635篇 |
2007年 | 885篇 |
2006年 | 775篇 |
2005年 | 658篇 |
2004年 | 656篇 |
2003年 | 570篇 |
2002年 | 527篇 |
2001年 | 474篇 |
2000年 | 424篇 |
1999年 | 408篇 |
1998年 | 285篇 |
1997年 | 244篇 |
1996年 | 258篇 |
1995年 | 220篇 |
1994年 | 183篇 |
1993年 | 153篇 |
1992年 | 121篇 |
1991年 | 134篇 |
1990年 | 110篇 |
1989年 | 107篇 |
1988年 | 80篇 |
1987年 | 58篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1977年 | 5篇 |
1973年 | 6篇 |
1957年 | 6篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 32 毫秒
1.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device. 相似文献
2.
Wenpin Wang Qing Yao Jianhui Song Binbin Yao Hui Wang Zhibo Li 《Journal of Polymer Science.Polymer Physics》2019,57(11):662-669
The PeakForce Quantitative Nanomechanical Mapping based on atomic force microscope (AFM) is employed to first visualize and then quantify the elastic properties of a model nitrile rubber/poly(vinyl chloride) (NBR/PVC) blend at the nanoscale. This method allows us to consistently observe the changes in mechanical properties of each phase in polymer blends. Beyond measuring and discriminating elastic modulus and adhesion forces of each phase, we tune the AFM tips and the peak force parameters in order to reliably image samples. In view of viscoelastic difference in each phase, a three‐phase coexistence of an unmixed NBR phase, the mixed phase, and PVC microcrystallites is directly visualized in NBR/PVC blends. The nanomechanical investigation is also capable of recognizing the crosslinked rubber phase in cured rubber. The contribution of the mixed phase was quantified and it was found that the mechanical properties of blends are mainly determined by the homogeneity and stiffness of the mixed phase. This study furthers our understanding the structure–mechanical property relationship of thermoplastic elastomers, which is important for their potential design and applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 662–669 相似文献
3.
In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K+-Na+. atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent (ζ) and the correlation length (ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange. 相似文献
4.
关于高师院校计算机专业教学改革的几点建议 总被引:1,自引:0,他引:1
本文以高等师范院校计算机专业教学改革为例,从教育观念的更新、教学模式的转变、教学手段的更新、教学对象的再认识、教学中的教材教法等多个方面分析以网络为主的现代教育模式改革的思想,目的在于探索出一条以多媒体和网络为主体的教学环境下的教育新思路。 相似文献
5.
根据曲柄滑块机构的型式 ,建立了一个含有对心和偏置两种情况在内的 2 0 30 0组的基本尺寸型连杆转角函数的谐波成分数据库。通过模糊识别方法 ,在已建立的数据库中 ,寻找出能够近似实现给定刚体导引的多个曲柄滑块机构基本尺寸型 ;然后计算机构的实际尺寸及安装尺寸参数。文中还给出了综合算例和运动仿真。 相似文献
6.
7.
8.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
9.
介绍了原子力显微镜在生物物理领域的最新应用:蛋白质去折叠、DNA拉伸、生物膜受力,通过分析实验得到的力谱,可以获取关于蛋白质、DNA、生物膜结构信息.原子力显微镜不仅能反映测量体系的力学性质,由于其具有独特的时间、空间分辨及实时成像,因而能提供更多信息. 相似文献
10.
在中心势场中粒子运动轨道方程的基础上,进一步讨论粒子轨道的闭合性、稳定性. 相似文献