全文获取类型
收费全文 | 1130篇 |
免费 | 128篇 |
国内免费 | 79篇 |
专业分类
化学 | 470篇 |
晶体学 | 19篇 |
力学 | 30篇 |
综合类 | 4篇 |
数学 | 90篇 |
物理学 | 724篇 |
出版年
2024年 | 3篇 |
2023年 | 81篇 |
2022年 | 25篇 |
2021年 | 21篇 |
2020年 | 58篇 |
2019年 | 41篇 |
2018年 | 19篇 |
2017年 | 48篇 |
2016年 | 37篇 |
2015年 | 27篇 |
2014年 | 54篇 |
2013年 | 100篇 |
2012年 | 71篇 |
2011年 | 76篇 |
2010年 | 60篇 |
2009年 | 67篇 |
2008年 | 65篇 |
2007年 | 72篇 |
2006年 | 44篇 |
2005年 | 56篇 |
2004年 | 44篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有1337条查询结果,搜索用时 15 毫秒
1.
We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5 ns laser pulses at 532 nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3 J cm−2, and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices. 相似文献
2.
Prof. Jen-Shyang Ni Tianliang Min Yaxi Li Menglei Zha Dr. Pengfei Zhang Prof. Chun Loong Ho Prof. Kai Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(25):10265-10271
Planar luminogens have encountered difficulties in overcoming intrinsic aggregation-caused emission quenching by intermolecular π-π stacking interactions. Although excited-state double-bond reorganization (ESDBR) can guide us on designing planar aggregation-induced emission (AIE) luminogens (AIEgens), its mechanism has yet been elucidated. Major challenges in the field include methods to efficiently restrict ESDBR and enhance AIE performance without using bulky substituents (e.g., tetraphenylethylene and triphenylamine). In this study, we rationally developed fluoro-substituent AIEgens with stronger intermolecular H-bonding interaction for restricted molecular motions and increased crystal density, leading to decreased nonradiative decay rate by one order of magnitude. The adjusted ESDBR properties also show a corresponding response to variation in viscosity. Furthermore, their aggregation-induced reactive oxygen species (ROS) generations have been discovered. The application of such planar AIEgen in treating multidrug-resistant bacteria has been demonstrated in a mouse model. The relationship between ROS generation and distinct E/Z-configurational stacking behaviors have been further understood, providing a design principle for synthesizing planar AIEgen-based photosensitizers. 相似文献
3.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity.
PACS 47.80.Jk, 47.40.Ki, 47.60.+i 相似文献
4.
5.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
6.
7.
本文考察了以微波等离子体炬(MPT)为光源,电热钽丝环进样时,溶液中共存元素对发射信号的影响。 相似文献
8.
卡尔曼滤波法用于ICP-AES分析时,在白色噪音情况下能给出准确的分析结果,当试样的某些组分未知时,测量噪音将不是白色的,分析结果将不准确。本文提出了一种加权增量卡尔曼滤波法来解决这个问题。 相似文献
9.
10.