全文获取类型
收费全文 | 10408篇 |
免费 | 2158篇 |
国内免费 | 1765篇 |
专业分类
化学 | 5115篇 |
晶体学 | 99篇 |
力学 | 754篇 |
综合类 | 161篇 |
数学 | 1220篇 |
物理学 | 6982篇 |
出版年
2024年 | 20篇 |
2023年 | 106篇 |
2022年 | 222篇 |
2021年 | 257篇 |
2020年 | 318篇 |
2019年 | 234篇 |
2018年 | 231篇 |
2017年 | 288篇 |
2016年 | 343篇 |
2015年 | 413篇 |
2014年 | 553篇 |
2013年 | 832篇 |
2012年 | 603篇 |
2011年 | 756篇 |
2010年 | 673篇 |
2009年 | 754篇 |
2008年 | 819篇 |
2007年 | 852篇 |
2006年 | 742篇 |
2005年 | 679篇 |
2004年 | 507篇 |
2003年 | 572篇 |
2002年 | 507篇 |
2001年 | 426篇 |
2000年 | 391篇 |
1999年 | 369篇 |
1998年 | 287篇 |
1997年 | 246篇 |
1996年 | 219篇 |
1995年 | 161篇 |
1994年 | 159篇 |
1993年 | 116篇 |
1992年 | 112篇 |
1991年 | 101篇 |
1990年 | 55篇 |
1989年 | 77篇 |
1988年 | 47篇 |
1987年 | 46篇 |
1986年 | 21篇 |
1985年 | 48篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Joseph R. Sootsman Duck Young Chung Dr. Mercouri G. Kanatzidis Prof. 《Angewandte Chemie (International ed. in English)》2009,48(46):8616-8639
Herein we cover the key concepts in the field of thermoelectric materials research, present the current understanding, and show the latest developments. Current research is aimed at increasing the thermoelectric figure of merit (ZT) by maximizing the power factor and/or minimizing the thermal conductivity. Attempts at maximizing the power factor include the development of new materials, optimization of existing materials by doping, and the exploration of nanoscale materials. The minimization of the thermal conductivity can come through solid‐solution alloying, use of materials with intrinsically low thermal conductivity, and nanostructuring. Herein we describe the most promising bulk materials with emphasis on results from the last decade. Single‐phase bulk materials are discussed in terms of chemistry, crystal structure, physical properties, and optimization of thermoelectric performance. The new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted. 相似文献
992.
Xiaochang Sun Yanbo Liu Qi Chen Bing Liu Dunru Zhu Yan Xu Prof. Dr. 《无机化学与普通化学杂志》2009,635(15):2596-2600
A new organic‐templated aluminogermanate [C4H12N][AlGe3O8] ( 1 ) has been prepared under solvothermal conditions by using 2‐propanol as solvent. The structure of the title compound was characterized by IR spectroscopic, elemental analysis, TG, single‐crystal X‐ray diffraction and powder X‐ray diffraction. Compound 1 crystallizes in the tetragonal space group I41/a, a = b = 10.7754(8) Å, c = 9.9116(14) Å, V = 1150.8(2) Å3, Z = 4. The structure of the title compound shows eight‐membered ring channels along a and b axes with a typical GIS topology, and – most importantly – the structure of the inorganic framework is retained when the organic amine is removed by calcination. 相似文献
993.
Gaël Zucchi Dr. Olivier Maury Dr. Pierre Thuéry Dr. Frédéric Gumy Jean‐Claude G. Bünzli Prof. Dr. Michel Ephritikhine Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9686-9696
Treatment of Ln(NO3)3?nH2O with 1 or 2 equiv 2,2′‐bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO3)3(bpm)2] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO3)3(bpm)2]?THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO3)3(bpm)2]?THF (Ln=Nd, Sm) from THF, or [Ln(NO3)3(bpm)(MeOH)2]?MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO2(NO3)2?6H2O with 1 equiv BPM in THF afforded the monoadduct [UO2(NO3)2(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid‐state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the YbIII ion emitting in the near‐IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air. 相似文献
994.
A new selective, sensitive, and rapid response microelectrode for microamount chromium(III) determination was developed. For the electrode preparation, fuchsin basic was electropolymerized onto a carbon microdisk electrode, and then diethylenetriamminepentaacetic acid (DTPA) was self‐assembled on the electrode surface by the reaction between DTPA and poly(fuchsin basic). The determination conditions were optimized. The electrode showed a linear response to Cr3+ ions in the concentration range of 1.0×10?6?1.0×10?4 M and exhibits a super‐Nernstian slope of 32.5±0.4 mV per decade. The detection limit is 3.6×10?7 M. The response time of the electrode is less than 10 s, and it can be used for at least 2 months with limited considerable divergences in its potentials. The proposed electrode was applied for monitoring the chromium ion level in wastewater of chromate industries. 相似文献
995.
Chunyan Du Shanghui Ye Jianming Chen Yunlong Guo Yunqi Liu Prof. Dr. Kun Lu Ying Liu Ting Qi Dr. Xike Gao Dr. Zhigang Shuai Prof. Dr. Gui Yu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8275-8282
A series of novel asymmetrical fused compounds containing the backbone of fluorene[2,3‐b]benzo[d]thiophene (FBT) were effectively synthesized and fully characterized. Single‐crystal X‐ray studies demonstrated that the length of the substituent side chains greatly affects the solid‐state packing of the obtained fused compounds. DFT, photophysical, and electrochemical studies all showed that the FBTs have large band gaps, low‐lying HOMO energy levels, and therefore good stability toward oxidation. Moreover, the substituents strongly influence the fluorescence properties of the resulting FBT derivatives. The di‐n‐hexyl compound exhibits intense fluorescence in solution with the highest quantum yield of up to 91 %. Solution‐processed green phosphorescent organic light‐emitting diodes with the di‐n‐butyl derivative as the host material exhibited a maximum brightness of 14 185 cd m?2 and a luminescence efficiency of 12 cd A?1. 相似文献
996.
Andrzej Maączyński Marian Góral Barbara Wiśniewska-Gocłowska Adam Skrzecz David Shaw 《Monatshefte für Chemie / Chemical Monthly》2003,134(5):633-653
Summary. The evaluation of mutual solubility data for systems water with n-alkanes, isoalkanes, and cycloalkanes along the three phase line is reported and a formula for the prediction of solubility
of alkanes in water is developed. Then a cubic equation of state with an added term, which accounts for hydrogen bonding is
used for correlation of liquid–liquid equilibrium data and for prediction of solubility of water in hydrocarbons using alkane
in water solubility data. Comparison of the predicted and experimental solubilities is performed using all accessible experimental
data. With this approach it is possible to predict the solubilities of water in alkanes with good accuracy over the temperature
range up to about 20 K below critical temperature. Solubility of alkanes in water can also be calculated using experimental
data for solubility of water in alkanes but results of these calculations are more sensitive to experimental errors of the
data.
Corresponding author: E-mail: macz@ichf.edu.pl
Received August 5, 2002; accepted (revised) September 13, 2002
Published online March 13, 2003
RID="a"
ID="a" Dedicated to Prof. Dr. H. Gamsj?ger on the occasion of his 70th birthday anniversary 相似文献
997.
Synthesis and Structure of Ag_3PSe_4 总被引:1,自引:0,他引:1
The title compound Ag3PSe4 was synthesized by the reaction of Ag powder,P2Se5 and Se in a molar ratio of 1:1:1 at 500℃ and structurally characterized by X-ray crystallography.The crystal belongs to orthorhombic,space group Pmn21 with cell parameters:a=7.689(4),b=6.660(3),c=6.379(4)A,V=326.7(3)A^3,Z=2,Dc=6.816g/cm^3,Mr=670.42,F(000)=584,μ=31.302mm^-1,R=0.0606,wR=0.1289 and S=1.012,The 3-D structure can be regarded as constructed from the stacking of puckered Ag-P-Se honeycomb-like sheets along the c direction,in which the Ag,P and Se atoms are bonded to each other to form a chair-like six-membered ring,and the rings then build the sheets by sharing edges. 相似文献
998.
An algebraic method that includes Gibbs minimization for performing phase equilibrium calculations for any number of components or phases 总被引:1,自引:0,他引:1
Gustavo A. Iglesias-Silva Adrin Bonilla-Petriciolet Philip T. Eubank James C. Holste Kenneth R. Hall 《Fluid Phase Equilibria》2003,210(2):229-245
The most widely used technique for performing phase equilibria calculations is the K-value method (equality of chemical potentials). This paper proposes a more efficient algorithm to achieve the results that includes Gibbs minimization when we know the number of phases. Using the orthogonal derivatives, the tangent plane equation and mass balances, it is possible to reduce the Gibbs minimization procedure to the task of finding the solution of a system of non-linear equations. Such an operation is easier and faster than finding tangents or areas, and appears to converge as fast as the K-value method. Examples illustrate application of the new technique to two and three phases in equilibrium for binary and ternary mixtures. 相似文献
999.
纳米晶钛酸铅表面态对介电性能的影响 总被引:3,自引:0,他引:3
将醋酸铅、钛酸四丁酯和硬脂酸在熔融状态下混合均匀后置于冷水浴中,使其凝固成凝胶,经不同温度焙烧,制成纳米晶PbTiO3.用X射线衍射光谱、红外光谱对产物进行表征.采用X射线光电子能谱和表面光电压谱对纳米晶PbTiO3表面状态分析,发现材料表面的不完整性主要是由氧空位造成.暴露在粒子表面的主要是金属离子.随着晶粒尺寸的减小,材料表面氧空位缺陷浓度增加,表面光伏效应增强,谱带变宽.纳米晶PbTiO3材料的表面状态对其极化性质有着重要的影响,使其静态介电常数远大于常规材料的静态介电常数. 相似文献
1000.
将钛酸四丁酯和硬脂酸在熔融状态下混合均匀后置于冷水浴中,使其凝固成凝胶,通过控制烧结过程中氧气的含量,成功地制备出粒度均匀、介电性能好的纳米晶TiO2.通过采用X射线光电子能谱和表面光电压谱对纳米晶TiO2表面状态的分析发现,材料表面存在大量的氧空位缺陷,暴露在粒子表面上的主要是一些金属Ti4+.纳米材料的这种表面状态对其极化性质具有重要的影响,使其在接近静态条件下的低频介电常数远大于常规材料的介电常数. 相似文献