全文获取类型
收费全文 | 25458篇 |
免费 | 5086篇 |
国内免费 | 4839篇 |
专业分类
化学 | 18801篇 |
晶体学 | 482篇 |
力学 | 1663篇 |
综合类 | 485篇 |
数学 | 3159篇 |
物理学 | 10793篇 |
出版年
2024年 | 66篇 |
2023年 | 417篇 |
2022年 | 888篇 |
2021年 | 884篇 |
2020年 | 1032篇 |
2019年 | 1011篇 |
2018年 | 875篇 |
2017年 | 904篇 |
2016年 | 1140篇 |
2015年 | 1312篇 |
2014年 | 1617篇 |
2013年 | 1978篇 |
2012年 | 2264篇 |
2011年 | 2397篇 |
2010年 | 1841篇 |
2009年 | 1889篇 |
2008年 | 1982篇 |
2007年 | 1712篇 |
2006年 | 1690篇 |
2005年 | 1420篇 |
2004年 | 1200篇 |
2003年 | 885篇 |
2002年 | 888篇 |
2001年 | 821篇 |
2000年 | 704篇 |
1999年 | 554篇 |
1998年 | 387篇 |
1997年 | 381篇 |
1996年 | 343篇 |
1995年 | 289篇 |
1994年 | 281篇 |
1993年 | 203篇 |
1992年 | 168篇 |
1991年 | 160篇 |
1990年 | 150篇 |
1989年 | 103篇 |
1988年 | 116篇 |
1987年 | 93篇 |
1986年 | 62篇 |
1985年 | 53篇 |
1984年 | 39篇 |
1983年 | 41篇 |
1982年 | 36篇 |
1981年 | 30篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1959年 | 9篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 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.
DING Bin-Gang ZHANG Da-Li LU Ding-Hui 《理论物理通讯》2006,46(1):113-118
We calculate the binding energies of Ni, Cu, Xe, Cs, Pt, Au, Np, Pu isotope chains using two interaction parameter sets NL-3 and NL-Z, and compared the relative errors of the even-even nuclei with those of odd-even nuclei and odd-odd nuclei. We find that the errors of binding energy of odd-even and odd-odd nuclei are not bigger than the one of even-even nuclei. The result shows that comparing with even-even nuclei, there is no systematic error and approximation in the calculations of the binding energy of odd-even and odd-odd nuclei with relativistic mean-field theory. In addition, the result is explained theoretically. 相似文献
9.
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
10.
为了在亚临界到临界点这个大范围内保证制冷剂物性计算的快速、稳定、可逆,提出将整个数据区间划分成若干个子区间分别进行隐式拟合,并且保证相邻子区间连接点处的连续与光滑,以及通过求分析解从隐式方程中得到显式物性计算式的方法.以美国国家标准局开发的程序REFPROP6.01的计算结果作为数据源,以R410A为例对该方法做了验证.得出快速物性计算公式的应用范围为饱和温度-60℃至临界温度,与NIST REFPROP 6.01的计算结果进行比较表明,计算速度快1500倍,平均相对偏差小于0.01%. 相似文献