全文获取类型
收费全文 | 100735篇 |
免费 | 4379篇 |
国内免费 | 3085篇 |
专业分类
化学 | 40804篇 |
晶体学 | 1041篇 |
力学 | 7935篇 |
综合类 | 234篇 |
数学 | 34448篇 |
物理学 | 23737篇 |
出版年
2024年 | 75篇 |
2023年 | 506篇 |
2022年 | 892篇 |
2021年 | 866篇 |
2020年 | 992篇 |
2019年 | 960篇 |
2018年 | 11035篇 |
2017年 | 10830篇 |
2016年 | 7168篇 |
2015年 | 1991篇 |
2014年 | 1646篇 |
2013年 | 2060篇 |
2012年 | 5809篇 |
2011年 | 12615篇 |
2010年 | 7096篇 |
2009年 | 7446篇 |
2008年 | 8072篇 |
2007年 | 10111篇 |
2006年 | 1522篇 |
2005年 | 2346篇 |
2004年 | 2382篇 |
2003年 | 2661篇 |
2002年 | 1676篇 |
2001年 | 776篇 |
2000年 | 750篇 |
1999年 | 599篇 |
1998年 | 595篇 |
1997年 | 505篇 |
1996年 | 503篇 |
1995年 | 426篇 |
1994年 | 345篇 |
1993年 | 311篇 |
1992年 | 250篇 |
1991年 | 212篇 |
1990年 | 201篇 |
1989年 | 169篇 |
1988年 | 133篇 |
1987年 | 117篇 |
1986年 | 112篇 |
1985年 | 92篇 |
1984年 | 71篇 |
1983年 | 73篇 |
1982年 | 66篇 |
1981年 | 51篇 |
1980年 | 65篇 |
1979年 | 47篇 |
1978年 | 44篇 |
1914年 | 45篇 |
1912年 | 42篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
2.
Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
3.
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis... 相似文献
4.
Cui Shisheng Shanbhag Uday Staudigl Mathias Vuong Phan 《Computational Optimization and Applications》2022,82(2):465-498
Computational Optimization and Applications - We develop a globalized Proximal Newton method for composite and possibly non-convex minimization problems in Hilbert spaces. Additionally, we impose... 相似文献
5.
Mathematical Programming - Convergence analysis of accelerated first-order methods for convex optimization problems are developed from the point of view of ordinary differential equation solvers. A... 相似文献
6.
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
7.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers. 相似文献
8.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
9.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant. 相似文献
10.