全文获取类型
收费全文 | 12454篇 |
免费 | 1936篇 |
国内免费 | 1552篇 |
专业分类
化学 | 9836篇 |
晶体学 | 474篇 |
力学 | 1285篇 |
综合类 | 45篇 |
数学 | 287篇 |
物理学 | 4015篇 |
出版年
2024年 | 14篇 |
2023年 | 160篇 |
2022年 | 319篇 |
2021年 | 463篇 |
2020年 | 777篇 |
2019年 | 528篇 |
2018年 | 465篇 |
2017年 | 499篇 |
2016年 | 741篇 |
2015年 | 760篇 |
2014年 | 781篇 |
2013年 | 1032篇 |
2012年 | 734篇 |
2011年 | 879篇 |
2010年 | 785篇 |
2009年 | 783篇 |
2008年 | 844篇 |
2007年 | 861篇 |
2006年 | 768篇 |
2005年 | 620篇 |
2004年 | 587篇 |
2003年 | 561篇 |
2002年 | 340篇 |
2001年 | 310篇 |
2000年 | 257篇 |
1999年 | 186篇 |
1998年 | 171篇 |
1997年 | 112篇 |
1996年 | 104篇 |
1995年 | 65篇 |
1994年 | 73篇 |
1993年 | 51篇 |
1992年 | 49篇 |
1991年 | 43篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1971年 | 6篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Hexametaphosphate‐Capped Silica Mesoporous Nanoparticles Containing CuII Complexes for the Selective and Sensitive Optical Detection of Hydrogen Sulfide in Water 下载免费PDF全文
Sameh El Sayed Dr. Michele Milani Prof. Maurizio Licchelli Prof. Ramón Martínez‐Máñez Dr. Félix Sancenón 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7002-7006
CuII‐macrocycle functionalized hexametaphosphate‐capped silica mesoporous nanoparticles have been prepared and used for the selective and sensitive detection of hydrogen sulfide in aqueous environments. The possibility of using different metal complexes combined with different capping anions and choice of different dyes or other sensing molecules as indicators makes this new protocol highly appealing for the preparation of new sensing systems for sulfide detection in different environments. 相似文献
42.
Highly Efficient Copper(II) Ion Sorbents Obtained by Calcium Carbonate Mineralization on Functionalized Cross‐Linked Copolymers 下载免费PDF全文
Dr. Marcela Mihai Dr. Ion Bunia Florica Doroftei Dr. Cristian‐Dragos Varganici Prof. Bogdan C. Simionescu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5220-5230
A new type of CuII ion sorbents is presented. These are obtained by CaCO3 mineralization from supersaturated solutions on gel‐like cross‐linked polymeric beads as insoluble templates. A divinylbenzene–ethylacrylate–acrylonitrile cross‐linked copolymer functionalized with weakly acidic, basic, or amphoteric functional groups has been used, as well as different initial inorganic concentrations and addition procedures for CaCO3 crystal growth. The morphology of the new composites was investigated by SEM and compared to that of the unmodified beads, and the polymorph content was established by X‐ray diffraction. The beads, before and after CaCO3 mineralization, were tested as sorbents for CuII ions. The newly formed patterns on the bead surface after CuII sorption were observed by SEM, and the elemental distribution on the composites and the chemical structure of crystals after interaction with CuII were investigated by EDAX elemental mapping and by FTIR‐ATR spectroscopy, respectively. The sorption capacity increased significantly after CaCO3 crystals growth on the weak anionic bead surface (up to 1041.5 mg CuII/g sample) compared to that of unmodified beads (491.5 mg CuII/g sample). 相似文献
43.
Back Cover: Porous Mn2O3: A Low‐Cost Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media with Comparable Activity to Pt/C (Chem. Eur. J. 29/2016) 下载免费PDF全文
Wenhai Wang Jing Geng Long Kuai Min Li Prof. Dr. Baoyou Geng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):10256-10256
44.
Shuang-Shuang Yang Ming-Jiang Xie Yu Shen Yong-Zheng Wang Xue-Feng Guo Bin Shen 《中国化学快报》2016,27(4):507-510
Chemical doping of nickel hydroxide with other cations(e.g. Al~(3+)) is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion(Ni~(2+)and AlO_2) double hydrolysis method was developed toward the synthesis of nickel–aluminum(Ni–Al) composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area(121 m~2/g) and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances(specific capacitance of 1670F/g and rate capability of 87% from 0.5 A/g to 20 A/g) to doping-free nickel hydroxide(specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g). Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability. 相似文献
45.
New dicarboxylate-functionalized pillared materials with a general formula of λ-ZrPO4(OH)1-x(OOC(CH2)nCOO)x/2(dmso) (n=6, 8 and 10) have been prepared by post-synthesis modification of the inorganic layers of λ-zirconium phosphate (λ-ZrP), where the superficial Chloride monovalent anionic ligands of λ-layer are partially exchanged with the divalent anionic ligands of a series of long-chain aliphatic dicarboxylic acids, namely octanedioic acid, decanedioic acid and dodecanedioic acid. The synthesized materials are characterized by X-ray diffractometry, FT-IR spectrophotometry, elemental and thermogravimetric analyses. The X-ray diffraction patterns show that the obtained solid phases are pure. Furthermore, the interlayer distance of λ-ZrP systematically increases from 1.02 to 1.59 nm as a result of the incorporation of the mentioned acids inside the interlayer gallery. 相似文献
46.
l‐Proline‐functionalized Fe3O4 nanoparticles as a novel magnetic chiral catalyst for the direct asymmetric Mannich reaction 下载免费PDF全文
l ‐Proline has been successfully anchored on the surface of magnetic nanoparticles and characterized using powder X‐ray diffraction, scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy. These nanoparticles as a chiral catalyst have been employed to promote the direct asymmetric Mannich reaction. The corresponding products are obtained in high yields with high level of diastereoselectivity (up to 99:1 dr) in the presence of Fe3O4– l ‐proline. Also this heterogeneous catalyst can be recovered easily and reused many times without significant loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
47.
Inside Cover: Selective Transformation of Syngas into Gasoline‐Range Hydrocarbons over Mesoporous H‐ZSM‐5‐Supported Cobalt Nanoparticles (Chem. Eur. J. 5/2015) 下载免费PDF全文
48.
Host–Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18‐Crown‐6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity 下载免费PDF全文
P. Lasitha Prof. Dr. Edamana Prasad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10558-10564
Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation‐induced quenching of emission from the system. Host–guest chemistry is one of the best‐known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18‐crown‐6 (18‐C‐6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18‐C‐6 formed complexes with amino‐substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI ? 18‐C‐6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60–70 %) from the PDI derivatives. More importantly, the host–guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self‐assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10?5 S cm?1. 相似文献
49.
The paper summarizes and discusses the recent advances of proteins as functional interlayers in organic field-effect transistors (OFETs). Specific focus is given on the proteins integrated into the device structure, either to act as dielectric materials or to perform as the functional interlayer between the dielectric and the organic semiconductor (OSC). The main emphasis is give to the location and the specific effect of protein layers in the structure of OFETs. Besides, the possibility of amyloid serving as useful building blocks for OFET is discussed. 相似文献
50.
Rational Design and Application of a Redox‐Active,Photoresponsive, Discrete Metallogelator 下载免费PDF全文
Dr. Rouzbeh Afrasiabi Prof. Dr. Heinz‐Bernhard Kraatz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(21):7695-7700
A photoresponsive discrete metallogelator was rationally designed by incorporating a photochromic azobenzene subunit in the structure of a redox‐active ferrocene–peptide conjugate. The target molecule was purposefully equipped with a dipeptide unit capable of self‐assembly in response to sonication. The designed molecule was shown to undergo supramolecular self‐assembly and achieve organogelation in response to ultrasound, light, heat, and redox signals. The sol–gel phase transition of the designed gelator was found to be sensitive to a plethora of input stimuli, allowing the application of the sol–gel transition behavior in basic logic gate operations. A gel‐based NOT logic gate operation was realized when the redox‐active property of the organogel was examined by using different oxidizing agents. The smart response of the gelator was further exploited in designing XOR operations under oxidizing or non‐oxidizing conditions. 相似文献