全文获取类型
收费全文 | 17306篇 |
免费 | 1397篇 |
国内免费 | 999篇 |
专业分类
化学 | 2608篇 |
晶体学 | 94篇 |
力学 | 3209篇 |
综合类 | 74篇 |
数学 | 634篇 |
物理学 | 3817篇 |
综合类 | 9266篇 |
出版年
2024年 | 51篇 |
2023年 | 154篇 |
2022年 | 291篇 |
2021年 | 323篇 |
2020年 | 444篇 |
2019年 | 327篇 |
2018年 | 380篇 |
2017年 | 486篇 |
2016年 | 548篇 |
2015年 | 564篇 |
2014年 | 824篇 |
2013年 | 772篇 |
2012年 | 834篇 |
2011年 | 936篇 |
2010年 | 738篇 |
2009年 | 872篇 |
2008年 | 803篇 |
2007年 | 1070篇 |
2006年 | 986篇 |
2005年 | 882篇 |
2004年 | 883篇 |
2003年 | 808篇 |
2002年 | 705篇 |
2001年 | 632篇 |
2000年 | 559篇 |
1999年 | 554篇 |
1998年 | 448篇 |
1997年 | 393篇 |
1996年 | 364篇 |
1995年 | 323篇 |
1994年 | 289篇 |
1993年 | 249篇 |
1992年 | 184篇 |
1991年 | 223篇 |
1990年 | 185篇 |
1989年 | 180篇 |
1988年 | 131篇 |
1987年 | 86篇 |
1986年 | 51篇 |
1985年 | 37篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 21篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1977年 | 7篇 |
1971年 | 6篇 |
1957年 | 11篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 355 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.
建立了整车8-DOF系统动力学模型,考虑了主动悬架控制,并增设了主动座椅控制,设计了车辆主动悬架系统的LQG控制器。基于Matlab仿真平台建立了整车8-DOF系统动力学仿真模型,对所得最优控制策略下的动态响应进行了仿真验证。仿真结果表明:为了改善人椅系统质心及车身质心的跳振性能需要在一定程度上弱化各轮轮胎动位移性能。从控制效能上来看,该最优控制器能够满足各行驶状态下对悬架性能的要求,改善了车辆的行驶平顺性。 相似文献
4.
提出了一种测量金属细线线密度的新方法,并对测量原理、公式进行了较为详细的推导,将测量结果与标准值进行了比较.从测量结果可知,其相对误差较小,说明利用该方法测量细线的线密度确实可行. 相似文献
5.
某计算机系统核心部件的隔振包装技术 总被引:1,自引:0,他引:1
对某计算机系统核心部件的振动特性进行分析并推算出其脆值,重点介绍了采用多级隔振包装的设计思路.基于模拟实验取得的数据表明,该包装设计可以满足计算机系统核心部件的隔振要求. 相似文献
6.
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
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