全文获取类型
收费全文 | 21668篇 |
免费 | 4042篇 |
国内免费 | 3199篇 |
专业分类
化学 | 15710篇 |
晶体学 | 299篇 |
力学 | 1336篇 |
综合类 | 302篇 |
数学 | 2589篇 |
物理学 | 8673篇 |
出版年
2024年 | 55篇 |
2023年 | 386篇 |
2022年 | 749篇 |
2021年 | 779篇 |
2020年 | 910篇 |
2019年 | 893篇 |
2018年 | 768篇 |
2017年 | 730篇 |
2016年 | 1014篇 |
2015年 | 1092篇 |
2014年 | 1327篇 |
2013年 | 1634篇 |
2012年 | 1971篇 |
2011年 | 2062篇 |
2010年 | 1485篇 |
2009年 | 1497篇 |
2008年 | 1595篇 |
2007年 | 1388篇 |
2006年 | 1307篇 |
2005年 | 1088篇 |
2004年 | 910篇 |
2003年 | 695篇 |
2002年 | 704篇 |
2001年 | 601篇 |
2000年 | 470篇 |
1999年 | 420篇 |
1998年 | 328篇 |
1997年 | 332篇 |
1996年 | 287篇 |
1995年 | 241篇 |
1994年 | 224篇 |
1993年 | 161篇 |
1992年 | 113篇 |
1991年 | 129篇 |
1990年 | 110篇 |
1989年 | 76篇 |
1988年 | 75篇 |
1987年 | 64篇 |
1986年 | 46篇 |
1985年 | 33篇 |
1984年 | 29篇 |
1983年 | 28篇 |
1982年 | 27篇 |
1981年 | 18篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1959年 | 5篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF. 相似文献
3.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors 下载免费PDF全文
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
4.
5.
6.
7.
8.
Yan WANG Rong Quan FENG 《数学学报(英文版)》2005,21(4):773-778
A Cayley map is a Cayley graph embedded in an orientable surface such that. the local rotations at every vertex are identical. In this paper, balanced regular Cayley maps for cyclic groups, dihedral groups, and generalized quaternion groups are classified. 相似文献
9.
Current methodologies used for the inference of thin film stress through curvature measurement are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single layer of thin film deposited on a substrate subjected to the non-uniform misfit strain in the thin film. Such methodologies are further extended to multi-layer thin films deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain. We derive relations between the stresses in each thin film and the change of system curvatures due to the deposition of each thin film. The interface shear stresses between the adjacent films and between the thin film and the substrate are also obtained from the system curvatures. This provides the basis for the experimental determination of thin film stresses in multi-layer thin films on a substrate. 相似文献
10.
ZhenFengZHANG 《数学学报(英文版)》2005,21(1):155-168
In this paper, we extend a classical result of Hua to arithmetic progressions with large moduli. The result implies the Linnik Theorem on the least prime in an arithmetic progression. 相似文献