全文获取类型
收费全文 | 17959篇 |
免费 | 2662篇 |
国内免费 | 2258篇 |
专业分类
化学 | 13650篇 |
晶体学 | 280篇 |
力学 | 966篇 |
综合类 | 188篇 |
数学 | 1720篇 |
物理学 | 6075篇 |
出版年
2024年 | 36篇 |
2023年 | 274篇 |
2022年 | 531篇 |
2021年 | 578篇 |
2020年 | 626篇 |
2019年 | 630篇 |
2018年 | 506篇 |
2017年 | 511篇 |
2016年 | 817篇 |
2015年 | 809篇 |
2014年 | 956篇 |
2013年 | 1310篇 |
2012年 | 1600篇 |
2011年 | 1638篇 |
2010年 | 1168篇 |
2009年 | 1015篇 |
2008年 | 1187篇 |
2007年 | 1002篇 |
2006年 | 996篇 |
2005年 | 934篇 |
2004年 | 746篇 |
2003年 | 656篇 |
2002年 | 721篇 |
2001年 | 482篇 |
2000年 | 435篇 |
1999年 | 387篇 |
1998年 | 287篇 |
1997年 | 265篇 |
1996年 | 253篇 |
1995年 | 238篇 |
1994年 | 189篇 |
1993年 | 173篇 |
1992年 | 161篇 |
1991年 | 137篇 |
1990年 | 123篇 |
1989年 | 99篇 |
1988年 | 86篇 |
1987年 | 57篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 33篇 |
1983年 | 29篇 |
1982年 | 21篇 |
1981年 | 20篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1957年 | 6篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 4 毫秒
181.
The effect of a thermal annealing treatment on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C60) composites is investigated. Upon thermal annealing at 120 °C, short-circuit current and power conversion efficiency (η) are more than tripled, while a sharp rise by eight times in and η is found for the device annealed at 200 °C. It is concluded that the improved phase separation between MEH-PPV and C60 leads to the enhancement of and η at 120 °C, while thermodynamic molecule arrangement at the higher temperature of ∼200 °C induces a significant increase in all photovoltaic parameters of composite devices except the open-circuit voltage . 相似文献
182.
Guohai Deng Dr. Sudip Pan Dr. Jiaye Jin Prof. Dr. Guanjun Wang Prof. Lili Zhao Prof. Dr. Mingfei Zhou Prof. Gernot Frenking 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):412-418
Two structural isomers containing five second-row element atoms with 24 valence electrons were generated and identified by matrix-isolation IR spectroscopy and quantum chemical calculations. The OCBNO complex, which is produced by the reaction of boron atoms with mixtures of carbon monoxide and nitric oxide in solid neon, rearranges to the more stable OBNCO isomer on UV excitation. Bonding analysis indicates that the OCBNO complex is best described by the bonding interactions between a triplet-state boron cation with an electron configuration of (2s)0(2pσ)0(2pπ)2 and the CO/NO− ligands in the triplet state forming two degenerate electron-sharing π bonds and two ligand-to-boron dative σ bonds. 相似文献
183.
184.
185.
Ionics - A novel cobalt-free perovskite La0.6Ba0.4Fe0.8Ni0.2O3 − δ (LBFN) powder was synthesized using a combustion method. The phase composition, electrical conductivity, thermal... 相似文献
186.
187.
188.
Yan Guan Dayu Zhou Jin Xu Xiaohua Liu Fei Cao Xianlin Dong Johannes Müller Tony Schenk Uwe Schroeder 《固体物理学:研究快报》2015,9(10):589-593
A wealth of studies have confirmed that the low‐field hysteresis behaviour of ferroelectric bulk ceramics and thin films can be described using Rayleigh relations, and irreversible domain wall motion across the array of pining defects has been commonly accepted as the underlying micro‐mechanism. Recently, HfO2 thin films incorporated with various dopants were reported to show pronounced ferroelectricity, however, their microscopic domain structure remains unclear till now. In this work, the effects of the applied electric field amplitude, frequency and temperature on the sub‐coercive polarization reversal properties were investigated for 10 nm thick Si‐doped HfO2 thin films. The applicability of the Rayleigh law to ultra‐thin ferroelectric films was first confirmed, indicating the existence of a multi‐domain structure. Since the grain size is about 20–30 nm, a direct observation of domain walls within the grains is rather challenging and this indirect method is a feasible approach to resolve the domain structure. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
189.
Qualitative screening procedures have been developed for the rapid detection and identification of the metabolites of nerve agents in the urine samples and extracts using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The combination of negative electrospray ionization (ESI) using a C18 column and water-methanol mobile phase modified with ammonium formate provides a rapid screening procedure for nerve agent degradation products with limit of detection of 1 ng/mL in the precursor-ion analysis. Also, determination of the alkyl methylphosphonic acids was carried out by the SRM scan mode with the limit of detection of 0.1 ng/mL. These procedures will be applicable to the trace analysis of metabolites of nerve agents in human urine matrices in the Organisation for the Prohibition of Chemical Weapons (OPCW) proficiency test. 相似文献
190.
Meng Li Hong‐Ye Bai Zu‐Lin Da Xu Yan Chao Chen Jin‐Hui Jiang Wei‐Qiang Fan Wei‐Dong Shi 《Crystal Research and Technology》2015,50(3):244-249
CaFe2O4/MgFe2O4 nanowires with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X‐Ray diffraction (XRD), UV–Vis diffuse reflectance spectra (UV‐Vis DR) and Environment scanning electron microscopy (ESEM). The novel CaFe2O4/MgFe2O4 nanowires exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare CaFe2O4 or MgFe2O4 samples, the prepared CaFe2O4/MgFe2O4 (Ca:Mg:Fe = 3:2:10) composited nanowires show the best photocatalytic performance with a degradation efficiency of 40% after 150 min reaction time. This enhancement is attributed to the heterostructure of CaFe2O4/MgFe2O4 nanowires, which effectively repress the recombination of photo‐generated electrons and holes. Based on heterostructure and energy band positions, the enhancement of mechanism under visible‐light enhances the photocatalytic activity. 相似文献