全文获取类型
收费全文 | 70577篇 |
免费 | 12559篇 |
国内免费 | 7198篇 |
专业分类
化学 | 49049篇 |
晶体学 | 625篇 |
力学 | 4645篇 |
综合类 | 310篇 |
数学 | 8183篇 |
物理学 | 27522篇 |
出版年
2024年 | 77篇 |
2023年 | 1537篇 |
2022年 | 1591篇 |
2021年 | 2353篇 |
2020年 | 3071篇 |
2019年 | 2850篇 |
2018年 | 2476篇 |
2017年 | 2265篇 |
2016年 | 3464篇 |
2015年 | 3317篇 |
2014年 | 3968篇 |
2013年 | 5152篇 |
2012年 | 6593篇 |
2011年 | 6737篇 |
2010年 | 4472篇 |
2009年 | 4260篇 |
2008年 | 4597篇 |
2007年 | 4114篇 |
2006年 | 3756篇 |
2005年 | 3132篇 |
2004年 | 2422篇 |
2003年 | 1888篇 |
2002年 | 1651篇 |
2001年 | 1413篇 |
2000年 | 1292篇 |
1999年 | 1484篇 |
1998年 | 1277篇 |
1997年 | 1254篇 |
1996年 | 1255篇 |
1995年 | 1034篇 |
1994年 | 916篇 |
1993年 | 759篇 |
1992年 | 669篇 |
1991年 | 578篇 |
1990年 | 501篇 |
1989年 | 382篇 |
1988年 | 332篇 |
1987年 | 271篇 |
1986年 | 249篇 |
1985年 | 204篇 |
1984年 | 143篇 |
1983年 | 102篇 |
1982年 | 79篇 |
1981年 | 67篇 |
1980年 | 65篇 |
1979年 | 32篇 |
1978年 | 30篇 |
1977年 | 40篇 |
1976年 | 30篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Two new Zn2Dy2 complexes were constructed from Zn (II) salen‐type Schiff base complex fragment and 2,6‐pyridinedimethanol (H2pdm) or its Br‐substituted analogue (4‐bromopyridine‐2,6‐diyl)dimethanol (H2Brpdm); their molecular formulas are [Zn2Dy2(L)2(pdm)2(MeOH)2](ClO4)2 [ 1 , H2L = N, N′‐ bis(3‐methoxysalicylidene)‐1,3‐diaminopropane] and [Zn2Dy2(L)2(Brpdm)2(MeOH)2](ClO4)2 [ 2 ], the Dy (III) ions of which have a NO7 triangular dodecahedral coordination sphere. The two complexes show not only ferromagnetic interaction but also field‐induced single‐molecule magnet (SMM) behavior, which are rare Dy (III)‐containing cluster complexes with the NO7 triangular dodecahedral coordination sphere that can show good magnetic relaxation. The energy barrier value of complex 2 is higher than those of complex 1 and the Dy (III) complexes with the DyNO7 triangular dodecahedral coordination configuration reported in the literature. 相似文献
82.
Mengjie Hu Haiquan Chen Mengxia Wang Gang Liu Chunhai Chen Guangtao Qian Youhai Yu 《Journal of polymer science. Part A, Polymer chemistry》2021,59(4):329-339
Polyimides (PI's) with low-dielectric constant and excellent organic solubility have broad application prospects in the electronic field. Herein, this study designed a series of novel, low dielectric, organic soluble PI films by creatively introducing fluorene and pyridine ring into diamine monomers. Because of the noncoplanar structure of fluorenyl and the polarization of pyridine ring, PI films achieved a low-dielectric constant (2.22–3.09 at 10 MHz) and excellent organic solubility. Even in some organic solvents with low-boiling points, these PI films still exhibited outstanding solubility. In addition, all the films possessed high-tensile strength (≈120 MPa) and excellent optical transparency (>70%, 450 nm). It was worth noting that the glass transition temperature of films was all above 280°C and 5% weight loss temperature (T5%) was at 486–553°C. In general, the novel high-performance low-dielectric PI films are expected to be used in the field of microelectronics. 相似文献
83.
84.
Wei Yuting Wang Qihua Liu Wei 《Annals of the Institute of Statistical Mathematics》2021,73(3):535-553
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the... 相似文献
85.
Periodica Mathematica Hungarica - Subsets with “good” properties in finite fields are widely applied in coding and cryptography. In this paper we introduce pseudorandom measures for... 相似文献
86.
A novel tiled Ti:sapphire(Ti:S)amplifier was experimentally demonstrated with>1 J amplified chirped pulse output.Two Ti:S crystals having dimensions of 14 mm×14 mm×25 mm were tiled as the gain medium in a four-pass amplifier.Maximum output energy of 1.18 J was obtained with 2.75 J pump energy.The energy conversion efficiency of the tiled Ti:S amplifier was comparable with a single Ti:S amplifier.The laser pulse having the maximum peak power of 28 TW was obtained after the compressor.Moreover,the influence of the beam gap on the far field was discussed.This novel tiled Ti:S amplifier technique can provide a potential way for 100 PW or EW lasers in the future. 相似文献
87.
Yunliang Liu Peiji Deng Ruqiang Wu Ramadan A. Geioushy Yaxi Li Yixian Liu Fengling Zhou Haitao Li Chenghua Sun 《Frontiers of Physics》2021,16(5):53503
The large-scale production of ammonia mainly depends on the Haber–Bosch process, which will lead to the problems of high energy consumption and carbon dioxide emission. Electrochemical nitrogen fixation is considered to be an environmental friendly and sustainable process, but its efficiency largely depends on the activity and stability of the catalyst. Therefore, it is imperative to develop highefficient electrocatalysts in the field of nitrogen reduction reaction (NRR). In this paper, we developed a BiVO4/TiO2 nanotube (BiVO4/TNT) heterojunction composite with rich oxygen vacancies as an electrocatalytic NRR catalyst. The heterojunction interface and oxygen vacancy of BiVO4/TNT can be the active site of N2 dynamic activation and proton transition. The synergistic effect of TiO2 and BiVO4 shortens the proton transport path and reduces the over potential of chemical reaction. BiVO4/TNT has high ammonia yield of 8.54 μg·h−1·cm−2 and high Faraday efficiency of 7.70% in −0.8 V vs. RHE in 0.1 M Na2SO4 solution. 相似文献
88.
Acta Mathematica Sinica, English Series - In this paper, we give some sufficient conditions for extended neighborhood coronas to have Laplacian perfect state transfer. We also give some conditions... 相似文献
89.
原子系综中的Duan-Lukin-Cirac-Zoller(DLCZ)过程是产生光与原子(量子界面)量子关联和纠缠的重要手段.当一束写光与原子发生作用时,将会产生斯托克斯(Stokes)光子的自发拉曼散射,并同时产生一个自旋波(spin-wave)存储在原子系综中,上述过程即为DLCZ量子记忆产生过程.这一过程被广泛地研究.本文将87Rb原子系综放入驻波腔,并使Stokes光子与光学腔共振,我们观察到有腔且锁定的情况下Stokes光子产生概率比无腔时增大了8.7倍.在此条件下研究了Stokes光子产生概率和写光功率的关系,Stokes光子产生概率随写光功率线性增大. 相似文献
90.
In recent years, clapping synchronization between individuals has been widely studied as one of the typical synchronization phenomena. In this paper, we aim to reveal the synchronization mechanism of clapping interactions by observing two individuals’ clapping rhythms in a series of experiments. We find that the two synchronizing clapping rhythm series exhibit long-range cross-correlations(LRCCs);that is, the interaction of clapping rhythms can be seen as a strong-anticipation process. Previous studies have demonstrated that the interactions in local timescales or global matching in statistical structures of fluctuation in long timescales can be sources of the strong-anticipation process. However, the origin of the strong anticipation process often appears elusive in many complex systems. Here, we find that the clapping synchronization process may result from the local interaction between two clapping individuals and may result from the more global coordination between two clapping individuals. We introduce two stochastic models for mutually interacting clapping individuals that generate the LRCCs and prove theoretically that the generation of clapping synchronization process needs to consider both local interaction and global matching. This study provides a statistical framework for studying the internal synchronization mechanism of other complex systems. Our theoretical model can also be applied to study the dynamics of other complex systems with the LRCCs, including finance, transportation, and climate. 相似文献