全文获取类型
收费全文 | 6809篇 |
免费 | 906篇 |
国内免费 | 639篇 |
专业分类
化学 | 3489篇 |
晶体学 | 43篇 |
力学 | 228篇 |
综合类 | 47篇 |
数学 | 543篇 |
物理学 | 1708篇 |
综合类 | 2296篇 |
出版年
2024年 | 33篇 |
2023年 | 113篇 |
2022年 | 224篇 |
2021年 | 185篇 |
2020年 | 229篇 |
2019年 | 223篇 |
2018年 | 179篇 |
2017年 | 161篇 |
2016年 | 271篇 |
2015年 | 264篇 |
2014年 | 359篇 |
2013年 | 361篇 |
2012年 | 425篇 |
2011年 | 426篇 |
2010年 | 322篇 |
2009年 | 352篇 |
2008年 | 395篇 |
2007年 | 348篇 |
2006年 | 313篇 |
2005年 | 301篇 |
2004年 | 220篇 |
2003年 | 241篇 |
2002年 | 389篇 |
2001年 | 323篇 |
2000年 | 193篇 |
1999年 | 203篇 |
1998年 | 142篇 |
1997年 | 153篇 |
1996年 | 162篇 |
1995年 | 120篇 |
1994年 | 124篇 |
1993年 | 111篇 |
1992年 | 68篇 |
1991年 | 93篇 |
1990年 | 82篇 |
1989年 | 77篇 |
1988年 | 42篇 |
1987年 | 34篇 |
1986年 | 33篇 |
1985年 | 28篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1959年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有8354条查询结果,搜索用时 0 毫秒
841.
Wei Xiong Xiaohong Zhao Genxing Zhu Changyu Shao Yaling Li Weimin Ma Xurong Xu Ruikang Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(41):12129-12133
Photobiological hydrogen production is of great importance because of its promise for generating clean renewable energy. In nature, green algae cannot produce hydrogen as a result of the extreme sensitivity of hydrogenase to oxygen. However, we find that silicification‐induced green algae aggregates can achieve sustainable photobiological hydrogen production even under natural aerobic conditions. The core–shell structure of the green algae aggregates creates a balance between photosynthetic electron generation and hydrogenase activity, thus allowing the production of hydrogen. This finding provides a viable pathway for the solar‐driven splitting of water into hydrogen and oxygen to develop green energy alternatives by using rationally designed cell–material complexes. 相似文献
842.
843.
Structure Modification Function of g‐C3N4 for Al2O3 in the In Situ Hydrothermal Process for Enhanced Photocatalytic Activity 下载免费PDF全文
Prof. Fa‐tang Li Shao‐jia Liu Ya‐bin Xue Dr. Xiao‐jing Wang Dr. Ying‐juan Hao Dr. Jun Zhao Rui‐hong Liu Prof. Dishun Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10149-10159
Heterojunctions of g‐C3N4/Al2O3 (g‐C3N4=graphitic carbon nitride) are constructed by an in situ one‐pot hydrothermal route based on the development of photoactive γ‐Al2O3 semiconductor with a mesoporous structure and a high surface area (188 m2g?1) acting as electron acceptor. A structure modification function of g‐C3N4 for Al2O3 in the hydrothermal process is found, which can be attributed to the coordination between unoccupied orbitals of the Al ions and lone‐pair electrons of the N atoms. The as‐synthesized heterojunctions exhibit much higher photocatalytic activity than pure g‐C3N4. The hydrogen generation rate and the reaction rate constant for the degradation of methyl orange over 50 % g‐C3N4/Al2O3 under visible‐light irradiation (λ>420 nm) are 2.5 and 7.3 times, respectively, higher than those over pristine g‐C3N4. The enhanced activity of the heterojunctions is attributed to their large specific surface areas, their close contact, and the high interfacial areas between the components as well as their excellent adsorption performance, and efficient charge transfer ability. 相似文献
844.
Back Cover: Ultrafast Photoinduced Charge Separation in Wide‐Band‐Capturing Self‐Assembled Supramolecular Bis(donor styryl)BODIPY–Fullerene Conjugates (Chem. Eur. J. 45/2015) 下载免费PDF全文
845.
Understanding the thermal stability of the proteins in human serum is essential since human serum is the important source of pharmaceutical proteins. Near-infrared (NIR) spectroscopy was applied to the investigation of thermal changes in secondary structure and hydration of human serum proteins. However, as a multicomponent system, the overlap of the broad NIR bands makes the structural analysis very difficult directly using the spectra of serum samples. Therefore, continuous wavelet transform (CWT) was used to improve the resolution of NIR spectra, and Monte Carlo-uninformative variable elimination (MC-UVE) method was applied to the selection of the variables associated with the proteins for the structural analysis. The variables (5956, 5867, 5815, 5747, 4525, 4401, 4359 and 4328 cm-1) related to protein secondary structures and those (7074, 6951, 6827 and 6700 cm-1) connected with water species were selected. Then, the thermal stability was analyzed through the intensity variations of the selected variables with temperature from 30 ℃ to 80 ℃. It was found that the variation of the spectral variables related to both α-helix and β-sheetchanges apparently around 60 ℃, indicating the beginning of the thermal denaturation and the transition from α-helix to β-sheet. Moreover, an obvious change was found around 60 ℃ for the content of the water specie S3, i.e., the water cluster containing three hydrogen bonds. The result demonstrates that MC-UVE can identify the protein-related NIR spectral variables, and the water species may be a marker for investigation of the structural change of proteins in biochemical systems. 相似文献
846.
847.
Ge Liu Jie Shao Youjun Gao Zheng Chen Qunting Qu 《Journal of Solid State Electrochemistry》2017,21(9):2593-2600
Sandwich-structured C@Fe3O4@C hybrids with Fe3O4 nanoparticles sandwiched between two conductive carbon layers have attracted more and more attention owing to enhanced synergistic effects for lithium-ion storage. In this work, an environment-friendly procedure is developed for the fabrication of sandwich-like C@Fe3O4@C dodecahedrons. Zeolitic imidazolate framework (ZIF-8)-derived carbon dodecahedrons (ZIF-C) are used as the carbon matrix, on which iron precursors are homogeneously grown with the assistance of a polyelectrolyte layer. The subsequent polydopamine (PDA) coating and calcination give rise to the formation of sandwiched ZIF-C@Fe3O4@C. When being evaluated as the anode material for lithium-ion batteries, the obtained hybrid manifests a high reversible capacity (1194 mAh g?1 at 0.05 A g?1), good high-rate behavior (796 mAh g?1 at 10 A g?1), and negligible capacity loss after 120 cycles. 相似文献
848.
Mengmeng Zhu Weishuo Li Panpan Xu Jingjing Shi Shan Shao Xiaosi Zhu Yitong Guo Yaowu He Zhao Hu Hongtao Yu Yanan Zhu Igor F. Perepichka Hong Meng 《中国科学:化学(英文版)》2017,60(1):63-76
Thieno[3,2-b]thiophene (TT) monomers end-capped with 3,4-ethylenedioxythiophene (EDOT) moieties are electropolymerized to form π-conjugated polymers with distinct electrochromic (EC) properties. Steric and electronic factors (electron donor and acceptor substituents) in the side groups of the TT core, as well as the structure of the polymer backbone strongly affect the electrochemical and optical properties of the polymers and their electrochromic characteristics. The studied polymers show low oxidation potentials, tunable from–0.78 to +0.30 V (vs. Fc/Fc+) and the band gaps from 1.46 to 1.92 eV and demonstrate wide variety of color palettes in polymer films in different states, finely tunable by structural variations in the polymer backbone and the side chains. EC materials of different colors in their doped/dedoped states have been developed (violet, deep blue, light blue, green, brown, purple-red, pinkish-red, orange-red, light gray, cyan and colorless transparent). High optical contrast (up to 79%), short response time (0.57–0.80 s), good cycling stability (up to 91% at 2000 cycles) and high coloration efficiency (up to 234.6 cm2 C–1) have been demonstrated and the influence of different factors on the above parameters of EC polymers have been discussed. 相似文献
849.
850.
This paper is concerned with a generalized Arzela–Ascoli's lemma, which has been extensively applied in almost periodic problems by the continuation theorem of degree theory. We give a counter example to show that this lemma is incorrect, and there is a gap in the proof of some existing literature, where the addressed generalized Arzela–Ascoli's lemma was used. Moreover, we make some final comments and introduce an open problem. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献