全文获取类型
收费全文 | 348160篇 |
免费 | 3630篇 |
国内免费 | 1296篇 |
专业分类
化学 | 180296篇 |
晶体学 | 5823篇 |
力学 | 16746篇 |
综合类 | 58篇 |
数学 | 40279篇 |
物理学 | 109884篇 |
出版年
2021年 | 3055篇 |
2020年 | 3278篇 |
2019年 | 3887篇 |
2018年 | 5312篇 |
2017年 | 5335篇 |
2016年 | 7512篇 |
2015年 | 4090篇 |
2014年 | 7047篇 |
2013年 | 15309篇 |
2012年 | 11914篇 |
2011年 | 14006篇 |
2010年 | 10729篇 |
2009年 | 10866篇 |
2008年 | 13193篇 |
2007年 | 12987篇 |
2006年 | 11952篇 |
2005年 | 10602篇 |
2004年 | 9946篇 |
2003年 | 9049篇 |
2002年 | 8909篇 |
2001年 | 10020篇 |
2000年 | 7455篇 |
1999年 | 5719篇 |
1998年 | 4833篇 |
1997年 | 4771篇 |
1996年 | 4475篇 |
1995年 | 4074篇 |
1994年 | 4151篇 |
1993年 | 3969篇 |
1992年 | 4504篇 |
1991年 | 4549篇 |
1990年 | 4399篇 |
1989年 | 4393篇 |
1988年 | 4298篇 |
1987年 | 4311篇 |
1986年 | 4070篇 |
1985年 | 5285篇 |
1984年 | 5367篇 |
1983年 | 4592篇 |
1982年 | 4666篇 |
1981年 | 4484篇 |
1980年 | 4262篇 |
1979年 | 4719篇 |
1978年 | 4729篇 |
1977年 | 4860篇 |
1976年 | 4900篇 |
1975年 | 4644篇 |
1974年 | 4556篇 |
1973年 | 4793篇 |
1972年 | 3463篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566 相似文献
3.
4.
Kai Cheng Xiao-Shuai Zhang Jie An Cheng Li Ruo-Yun Zhang Run Ye Prof. Dr. Bang-Jiao Ye Prof. Dr. Bo Liu Prof. Dr. Yuan-Di Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7553-7560
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA. 相似文献
5.
The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry 下载免费PDF全文
6.
Dr. Yulia Y. Enakieva Dr. Anna A. Sinelshchikova Prof. Mikhail S. Grigoriev Prof. Vladimir V. Chernyshev Dr. Konstantin A. Kovalenko Prof. Irina A. Stenina Prof. Andrey B. Yaroslavtsev Prof. Yulia G. Gorbunova Prof. Aslan Y. Tsivadze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10552-10556
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity). 相似文献
7.
8.
9.
10.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling. 相似文献