全文获取类型
收费全文 | 6542篇 |
免费 | 505篇 |
国内免费 | 409篇 |
专业分类
化学 | 1013篇 |
晶体学 | 10篇 |
力学 | 1497篇 |
综合类 | 102篇 |
数学 | 2468篇 |
物理学 | 2366篇 |
出版年
2023年 | 56篇 |
2022年 | 70篇 |
2021年 | 115篇 |
2020年 | 158篇 |
2019年 | 138篇 |
2018年 | 127篇 |
2017年 | 136篇 |
2016年 | 181篇 |
2015年 | 187篇 |
2014年 | 286篇 |
2013年 | 444篇 |
2012年 | 263篇 |
2011年 | 329篇 |
2010年 | 251篇 |
2009年 | 367篇 |
2008年 | 399篇 |
2007年 | 465篇 |
2006年 | 394篇 |
2005年 | 343篇 |
2004年 | 294篇 |
2003年 | 280篇 |
2002年 | 241篇 |
2001年 | 213篇 |
2000年 | 253篇 |
1999年 | 220篇 |
1998年 | 157篇 |
1997年 | 160篇 |
1996年 | 110篇 |
1995年 | 101篇 |
1994年 | 91篇 |
1993年 | 97篇 |
1992年 | 77篇 |
1991年 | 72篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 39篇 |
1987年 | 46篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 19篇 |
1981年 | 19篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 18篇 |
排序方式: 共有7456条查询结果,搜索用时 17 毫秒
1.
Aimed at the internal short circuit problem due to large deformation of the prismatic lithium-ion battery cell under impact loadings, a simplified battery model was first established. Then the motion equations of velocity and displacement based on the membrane factor method were proposed. With the effects of the face-sheet thickness and the densification region on the normalized final deflection, impact response characteristics of prismatic battery cells were investigated in detail. The results show that, the improved motion equations involving the membrane factor can reflect the dynamic response mechanisms of the prismatic battery cell under impact loadings, and the large deflection under high-speed impact can be predicted. With the increase of the face-sheet thickness, the deflection of the battery cell’s lower part decreases obviously. However, the densification region expands with the face-sheet thickness. The deflection and the densification region of the cell’s lower part both increase with the inner core density of the battery. This proposed impact model provides a theoretical guidance for the multi-functional integrated dynamic design of prismatic battery cells. © 2022 Editorial Office of Applied Mathematics and Mechanics. All rights reserved. 相似文献
2.
Sujie Yang Xiuyu Liu Gang Tang Hongming Long Bibo Wang Hao Zhang Yilong Ji Yadong Yang 《先进技术聚合物》2022,33(1):452-463
A series of FR-RPUF composites were prepared by a one-step water foaming process with ammonium polyphosphate (APP) and steel slag (SS) as flame retardants. Thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical combustion test, microscale combustion calorimetry (MCC), TG-Fourier transform infrared spectrometry (TG-FTIR), scanning electron microscopy (SEM), Raman spectra and FTIR were used to investigate the thermal stability, flame retardancy, combustion performance, gas phase products, and char residue morphology of FR-RPUF composites. TG test results showed that the initial decomposition temperature (T-5wt%) and char residue rate at 700°C of RPUF/APP/SS composites were significantly enhanced by the addition of APP and SS, and the thermal stability of the composites was improved. Flame retardant test results confirmed the significantly increased LOI values of RPUF/APP/SS composites with V-0 rating. TG-FTIR also confirmed the obviously decreased release of toxic gases and flammable gases in the combustion of RPUF/APP/SS composites. SEM and Raman spectra of char residues for the composites suggested that APP/SS system improved the compactness and graphitization degree of char layer for RPUF/APP/SS composite. The above researches provide a new strategy for the utilization of SS in fire safety engineering. 相似文献
3.
4.
5.
《Arabian Journal of Chemistry》2022,15(7):103933
In this study, a fingerprint-activity relationship modeling between chemical fingerprints and antirheumatic activity was established, and multivariate statistical analysis was used to evaluate the quality of Taxilli Herba (TH) from different hosts. Characteristic fingerprints of 20 batches of TH samples were generated by high-performance liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (HPLC-Triple TOF-MS/MS), and the similarity analysis was calculated based on thirteen common characteristic peaks by hierarchical clustering analysis (HCA). Subsequently, nine efficacy markers were discovered by combining fingerprints and antirheumatic activity through grey correlation analysis (GCA) and bivariate correlation analysis (BCA). Meanwhile, the content of 5 constituents in 9 markers was determined by high-performance liquid chromatography coupled with triple quadrupole-linear ion trap tandem mass spectrometry (HPLC-QTRAP-MS/MS). The comprehensive quality of TH was assessed using multivariate statistical analysis, including principal components analysis (PCA) and technique for order preference by similarity to ideal solution (TOPSIS). The results showed that a high dose of TH extract could markedly ameliorate arthritis damage compared to other doses, with flavonoids playing an important role in the antirheumatic activity. The comprehensive quality of samples from Morus alba L. (SS) was superior to those from Liquidambar formosana Hance (FXS). The present study will demonstrate the markers associated with efficacy, and provide an applicable strategy for more comprehensive quality control and evaluation of TH. 相似文献
6.
The Regularity of Stochastic Convolution Driven by Tempered Fractional Brownian Motion and Its Application to Mean-field Stochastic Differential Equations 下载免费PDF全文
In this paper, some properties of a stochastic convolution driven by tempered fractional Brownian motion are obtained. Based on this result, we get the existence and uniqueness of stochastic mean-field equation driven by tempered fractional Brownian motion. Furthermore, combining with the Banach fixed point theorem and the properties of Mittag-Leffler functions, we study the existence and uniqueness of mild solution for a kind of time fractional mean-field stochastic differential equation driven by tempered fractional Brownian motion. 相似文献
7.
《Journal of Pure and Applied Algebra》2022,226(8):107024
We solve a combinatorial question concerning eigenvalues of the universal intertwining endomorphism of a subset representation. 相似文献
8.
《Mathematical Methods in the Applied Sciences》2018,41(12):4465-4479
In this paper, stochastic operational matrix of integration based on delta functions is applied to obtain the numerical solution of linear and nonlinear stochastic quadratic integral equations (SQIEs) that appear in modelling of many real problems. An important advantage of this method is that it dose not need any integration to compute the constant coefficients. Also, this method can be utilized to solve both linear and nonlinear problems. By using stochastic operational matrix of integration together collocation points, solving linear and nonlinear SQIEs converts to solve a nonlinear system of algebraic equations, which can be solved by using Newton's numerical method. Moreover, the error analysis is established by using some theorems. Also, it is proved that the rate of convergence of the suggested method is O(h2). Finally, this method is applied to solve some illustrative examples including linear and nonlinear SQIEs. Numerical experiments confirm the good accuracy and efficiency of the proposed method. 相似文献
9.
Dr. Zhenbo Mo Dr. Takanori Shima Prof. Dr. Zhaomin Hou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(22):8713-8722
Studies on N2 activation and transformation by transition metal hydride complexes are of particular interest and importance. The synthesis and diverse transformations of a dinitrogen dititanium hydride complex bearing the rigid acridane-based acriPNP-pincer ligands {[(acriPNP)Ti]2(μ2-η1:η2-N2)(μ2-H)2} are presented. This complex enabled N2 cleavage and hydrogenation even without additional H2 or other reducing agents. Furthermore, diverse transformations of the N2 unit with a variety of organometallic compounds such as ZnMe2, MgMe2, AlMe3, B(C6F5)3, PinBH, and PhSiH3 have been well established at the rigid acriPNP-ligated dititanium framework, such as reversible bonding-mode change between the end-on and side-on/end-on fashions, diborylative N=N bond cleavage, the formal insertion of two dimethylaluminum species into the N=N bond, and the formal insertion of two silylene units into the N=N bond. This work has revealed many unprecedented aspects of dinitrogen reaction chemistry. 相似文献
10.
《Wave Motion》2018
The evolution of surface gravity waves is driven by nonlinear interactions that trigger an energy cascade similarly to the one observed in hydrodynamic turbulence. This process, known as wave turbulence, has been found to display anomalous scaling with deviation from classical turbulent predictions due to the emergence of coherent and intermittent structures on the water surface. In the ocean, waves are spread over a wide range of directions, with a consequent attenuation of the nonlinear properties. A laboratory experiment in a large wave facility is presented to discuss the sensitivity of wave turbulence on the directional properties of model wave spectra. Results show that the occurrence of coherent and intermittent structures become less likely with the broadening of the wave directional spreading. There is no evidence, however, that intermittency completely vanishes. 相似文献