全文获取类型
收费全文 | 287989篇 |
免费 | 5097篇 |
国内免费 | 2559篇 |
专业分类
化学 | 138058篇 |
晶体学 | 4141篇 |
力学 | 15621篇 |
综合类 | 71篇 |
数学 | 43790篇 |
物理学 | 93964篇 |
出版年
2021年 | 1526篇 |
2020年 | 1729篇 |
2019年 | 1704篇 |
2018年 | 10951篇 |
2017年 | 11867篇 |
2016年 | 7344篇 |
2015年 | 3564篇 |
2014年 | 3516篇 |
2013年 | 8933篇 |
2012年 | 12167篇 |
2011年 | 22200篇 |
2010年 | 13364篇 |
2009年 | 13450篇 |
2008年 | 19272篇 |
2007年 | 22771篇 |
2006年 | 8025篇 |
2005年 | 14609篇 |
2004年 | 10057篇 |
2003年 | 8983篇 |
2002年 | 6801篇 |
2001年 | 6503篇 |
2000年 | 5156篇 |
1999年 | 3831篇 |
1998年 | 2928篇 |
1997年 | 2863篇 |
1996年 | 3005篇 |
1995年 | 2634篇 |
1994年 | 2429篇 |
1993年 | 2245篇 |
1992年 | 2553篇 |
1991年 | 2519篇 |
1990年 | 2212篇 |
1989年 | 2176篇 |
1988年 | 2190篇 |
1987年 | 2106篇 |
1986年 | 1994篇 |
1985年 | 2900篇 |
1984年 | 2879篇 |
1983年 | 2321篇 |
1982年 | 2485篇 |
1981年 | 2371篇 |
1980年 | 2321篇 |
1979年 | 2277篇 |
1978年 | 2357篇 |
1977年 | 2228篇 |
1976年 | 2194篇 |
1975年 | 2168篇 |
1974年 | 2068篇 |
1973年 | 2190篇 |
1972年 | 1233篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse. 相似文献
53.
Nonlinear Dynamics - In this paper, the current-controlled DC–DC buck converter from a new perspective are studied through the switching theory of flow, and the analytical conditions of the... 相似文献
54.
55.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
56.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
57.
58.
59.
We report a spatially modulated polarimetry scheme by using a zero-order vortex half-wave retarder(ZVHR)and a spatial Fourier analysis method.A ZVHR is employed to analyze the input polarized light and convert it into a vectorial optical field,and an analyzer is set after the ZVHR to form an hourglass intensity pattern due to the spatial polarization modulation.Then,the input light’s Stokes parameters can be calculated by spatial Fourier analysis of the hourglass pattern with a single shot.The working principle of the polarimeter has been analyzed by the Stokes-Mueller formalism,and some quantitative measuring experiments of different polarization states have been demonstrated.The experimental results indicate that the proposed polarimeter is accurate,robust,and simple to use. 相似文献
60.
Thalia Tsiaka Panagiotis Zoumpoulakis Vassilia J. Sinanoglou Constantinos Makris Georgios A. Heropoulos Antony C. Calokerinos 《Analytica chimica acta》2015
High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE. 相似文献