全文获取类型
收费全文 | 1272篇 |
免费 | 163篇 |
国内免费 | 127篇 |
专业分类
化学 | 902篇 |
晶体学 | 9篇 |
力学 | 70篇 |
综合类 | 9篇 |
数学 | 185篇 |
物理学 | 387篇 |
出版年
2024年 | 7篇 |
2023年 | 26篇 |
2022年 | 59篇 |
2021年 | 39篇 |
2020年 | 41篇 |
2019年 | 45篇 |
2018年 | 40篇 |
2017年 | 31篇 |
2016年 | 69篇 |
2015年 | 49篇 |
2014年 | 57篇 |
2013年 | 74篇 |
2012年 | 95篇 |
2011年 | 116篇 |
2010年 | 75篇 |
2009年 | 81篇 |
2008年 | 80篇 |
2007年 | 66篇 |
2006年 | 77篇 |
2005年 | 46篇 |
2004年 | 48篇 |
2003年 | 41篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 31篇 |
1999年 | 39篇 |
1998年 | 22篇 |
1997年 | 25篇 |
1996年 | 20篇 |
1995年 | 10篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 3篇 |
排序方式: 共有1562条查询结果,搜索用时 15 毫秒
271.
S Fukuzumi K Ohkubo H Imahori J Shao Z Ou G Zheng Y Chen R K Pandey M Fujitsuka O Ito K M Kadish 《Journal of the American Chemical Society》2001,123(43):10676-10683
The photochemical and electrochemical properties of four chlorin-C60 or porphyrin-C60 dyads having the same short spacer between the macrocycle and the fullerene are examined. In contrast with all the previous results on porphyrin-fullerene dyads, the photoexcitation of a zinc chlorin-C60 dyad results in an unusually long-lived radical ion pair which decays via first-order kinetics with a decay rate constant of 9.1 x 10(3) x s(-1). This value is 2-6 orders of magnitude smaller than values reported for all other porphyrin or chlorin donor-acceptor of the molecule dyad systems. The formation of radical cations of the donor part and the radical anion of the acceptor part was also confirmed by ESR measurements under photoirradiation at low temperature. The photoexcitation of other dyads (free-base chlorin-C60, zinc porphyrin-C60, and free-base porphyrin-C60 dyads) results in formation of the ion pairs which decay quickly to the triplet excited states of the chlorin or porphyrin moiety via the higher lying radical ion pair states as is expected from the redox potentials. 相似文献
272.
本文对[4+ 3 ]环加成反应体系以及最近在合成中的应用进行了综述, 并对进一步研究的方向进行了讨论。 相似文献
273.
铁矿石经盐酸溶解后,用H2O2氧化,使Fe^2+氧化成Fe^3+。加入过量的VC还原Fe^3+,剩余VC用NBSM滴定。方便简便,快速,终点敏锐,精了,准确度高,RSD≤0.3%,相对误差〈0.4%,并可选择性地滴定矿石中的三价铁。 相似文献
274.
275.
Air-stable ambipolar organic field effect transistors with heterojunction of pentacene and N,N'-bis(4-trifluoromethylben-zyl)perylene-3,4,9,10-tetracarboxylic diimide
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fabrication of ambipolar organic field-effect transistors (OFETs) is
essential for the achievement of an organic complementary logic
circuit. Ambipolar transports in OFETs with heterojunction
structures are realized. We select pentacene as a P-type material and
N,N'-bis(4-trifluoromethylben-zyl)perylene-3,4,9,10-tetracarboxylic
diimide (PTCDI-TFB) as a n-type material in the active layer of the
OFETs. The field-effect transistor shows highly air-stable ambipolar
characteristics with a field-effect hole mobility of
0.18~cm2/(V.s) and field-effect electron mobility of
0.031~cm2/(V.s). Furthermore the mobility only slightly
decreases after being exposed to air and remains stable even for
exposure to air for more than 60 days. The high electron affinity of
PTCDI-TFB and the octadecyltrichlorosilane (OTS) self-assembly
monolayer between the SiO2 gate dielectric and the organic
active layer result in the observed air-stable characteristics of
OFETs with high mobility. The results demonstrate that using the OTS
as a modified gate insulator layer and using high electron affinity
semiconductor materials are two effective methods to fabricate OFETs
with air-stable characteristics and high mobility. 相似文献
276.
Three-dimensional size and orientation of the precipitates in AZ91 magnesium alloys measured by TEM techniques
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Knowledge of the microscopic structure, including three-dimensional
(3-D) size and orientation of the precipitates, is essential to
fully understand the mechanical properties of the magnesium
alloys and designing the alloys with better performance. Analytical
TEM with high spatial resolution offers the simultaneous
measurements of 3-D size, structure, orientation, composition of the
precipitates from one typical sample along an established
crystallographic axis. Besides popular Burgers orientation
relationship (OR), other ORs such as Pitsch--Schrader OR, Crawley
OR, Potter OR and a new OR with the form of [0001]α
1.0° from [311]γ and (11\bar 20)α
2.0° from (03\bar 3)γ between the magnesium
matrix and the precipitate γ -Mg17Al12 are
identified by TEM imaging and diffraction techniques. As a case study,
the thicknesses of the individual precipitates with Burgers OR are
further measured to be 100--200~nm through both electron energy-loss
spectroscopy and x-ray energy dispersive spectroscopy combining
differential x-ray absorption and extrapolation, which are in
agreement with the overall 3-D size statistic distribution results
obtained through analysing various samples along various directions.
Furthermore, the fabricated wedge-shape structure provides a
platform on which to study the dependence of the interfacial strain on the
variation of the thickness. 相似文献
277.
278.
279.
The study on the mechanism and kinetics of mRNA degradation provides a new vision for chemical intervention on protein expression. The AU enrichment element (ARE) in mRNA 3′-UTR can be recognized and bound by the ARE binding protein (AU-rich Element factor (AUF1) to recruit RNase for degradation. In the present study, we proposed a novel strategy for expression regulation that interferes with the AUF1-RNA binding. A small-molecule compound, JNJ-7706621, was found to bind AUF1 protein and inhibit mRNA degradation by screening the commercial compound library. We discovered that JNJ-7706621 could inhibit the expression of AUF1 targeted gene IL8, an essential pro-inflammatory factor, by interfering with the mRNA homeostatic state. These studies provide innovative drug design strategies to regulate mRNA homeostasis. 相似文献
280.
Leqing Lin Yu Zhong Haoyang Lin Chenglong Wang Zhifei Yang Qian Wu Di Zhang Wenguo Zhu Yongchun Zhong Yuwei Pan Jianhui Yu Huadan Zheng 《Molecules (Basel, Switzerland)》2022,27(13)
Spider silk is one of the hottest biomaterials researched currently, due to its excellent mechanical properties. This work reports a novel humidity sensing platform based on a spider silk-modified quartz tuning fork (SSM-QTF). Since spider silk is a kind of natural moisture-sensitive material, it does not demand additional sensitization. Quartz-enhanced conductance spectroscopy (QECS) was combined with the SSM-QTF to access humidity sensing sensitively. The results indicate that the resonance frequency of the SSM-QTF decreased monotonously with the ambient humidity. The detection sensitivity of the proposed SSM-QTF sensor was 12.7 ppm at 1 min. The SSM-QTF sensor showed good linearity of ~0.99. Using this sensor, we successfully measured the humidity of disposable medical masks for different periods of wearing time. The results showed that even a 20 min wearing time can lead to a >70% humidity in the mask enclosed space. It is suggested that a disposable medical mask should be changed <2 h. 相似文献