全文获取类型
收费全文 | 2397篇 |
免费 | 49篇 |
国内免费 | 8篇 |
专业分类
化学 | 1741篇 |
晶体学 | 8篇 |
力学 | 24篇 |
数学 | 240篇 |
物理学 | 441篇 |
出版年
2021年 | 17篇 |
2020年 | 32篇 |
2019年 | 24篇 |
2016年 | 39篇 |
2015年 | 32篇 |
2014年 | 26篇 |
2013年 | 86篇 |
2012年 | 73篇 |
2011年 | 85篇 |
2010年 | 52篇 |
2009年 | 45篇 |
2008年 | 77篇 |
2007年 | 70篇 |
2006年 | 80篇 |
2005年 | 93篇 |
2004年 | 59篇 |
2003年 | 53篇 |
2002年 | 68篇 |
2001年 | 55篇 |
2000年 | 42篇 |
1999年 | 37篇 |
1998年 | 23篇 |
1997年 | 22篇 |
1996年 | 28篇 |
1995年 | 23篇 |
1994年 | 25篇 |
1993年 | 25篇 |
1992年 | 37篇 |
1991年 | 21篇 |
1989年 | 25篇 |
1988年 | 32篇 |
1987年 | 23篇 |
1986年 | 36篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 26篇 |
1982年 | 17篇 |
1981年 | 33篇 |
1980年 | 32篇 |
1979年 | 23篇 |
1978年 | 28篇 |
1977年 | 25篇 |
1976年 | 31篇 |
1975年 | 27篇 |
1974年 | 23篇 |
1973年 | 20篇 |
1967年 | 17篇 |
1932年 | 17篇 |
1928年 | 17篇 |
1900年 | 16篇 |
排序方式: 共有2454条查询结果,搜索用时 15 毫秒
111.
Edgar Uhl Peter Mayer Henry Dube 《Angewandte Chemie (International ed. in English)》2020,59(14):5730-5737
Light‐driven molecular motors possess immense potential as central driving units for future nanotechnology. Integration into larger molecular setups and transduction of their mechanical motions represents the current frontier of research. Herein we report on an integrated molecular machine setup allowing the transmission of potential energy from a motor unit onto a remote receiving entity. The setup consists of a motor unit connected covalently to a distant and sterically encumbered biaryl receiver. By action of the motor unit, single‐bond rotation of the receiver is strongly accelerated and forced to proceed unidirectionally. The transmitted potential energy is directly measured as the extent to which energy degeneration is lifted in the thermal atropisomerization of this biaryl. Energy degeneracy is reduced by more than 1.5 kcal mol?1, and rate accelerations of several orders of magnitude in terms of the rate constants are achieved. 相似文献
112.
113.
114.
Electrochemiluminescence Bioassays with a Water‐Soluble Luminol Derivative Can Outperform Fluorescence Assays 下载免费PDF全文
Michael Mayer Prof. Dr. Shigehiko Takegami Michael Neumeier Simone Rink Prof. Dr. Axel Jacobi von Wangelin Silja Schulte Moritz Vollmer Prof. Dr. Axel G. Griesbeck PD Dr. Axel Duerkop Prof. Dr. Antje J. Baeumner 《Angewandte Chemie (International ed. in English)》2018,57(2):408-411
The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy)3]2+, and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water‐soluble m‐carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four‐fold ECL signal increase (vs. luminol). Entrapment in DNA‐tagged liposomes enabled a DNA assay with a detection limit of 3.2 pmol L?1, which is 150 times lower than the corresponding fluorescence approach. This remarkable sensitivity gain and the low excitation potential establish m‐carboxy luminol as a superior ECL probe with direct relevance to chemiluminescence and enzymatic bioanalytical approaches. 相似文献
115.
Photoelectrochemical Hydrogen Production in Alkaline Solutions Using Cu2O Coated with Earth‐Abundant Hydrogen Evolution Catalysts 下载免费PDF全文
Carlos G. Morales‐Guio Laurent Liardet Dr. Matthew T. Mayer Dr. S. David Tilley Prof. Dr. Michael Grätzel Prof. Dr. Xile Hu 《Angewandte Chemie (International ed. in English)》2015,54(2):664-667
The splitting of water into hydrogen and oxygen molecules using sunlight is an attractive method for solar energy storage. Until now, photoelectrochemical hydrogen evolution is mostly studied in acidic solutions, in which the hydrogen evolution is more facile than in alkaline solutions. Herein, we report photoelectrochemical hydrogen production in alkaline solutions, which are more favorable than acidic solutions for the complementary oxygen evolution half‐reaction. We show for the first time that amorphous molybdenum sulfide is a highly active hydrogen evolution catalyst in basic medium. The amorphous molybdenum sulfide catalyst and a Ni–Mo catalyst are then deposited on surface‐protected cuprous oxide photocathodes to catalyze sunlight‐driven hydrogen production in 1 M KOH. The photocathodes give photocurrents of ?6.3 mA cm?2 at the reversible hydrogen evolution potential, the highest yet reported for a metal oxide photocathode using an earth‐abundant hydrogen evolution reaction catalyst. 相似文献
116.
A Flexible Photoactive Titanium Metal–Organic Framework Based on a [TiIV3(μ3‐O)(O)2(COO)6] Cluster 下载免费PDF全文
Bart Bueken Dr. Frederik Vermoortele Dr. Danny E. P. Vanpoucke Dr. Helge Reinsch Dr. Chih‐Chin Tsou Dr. Pieterjan Valvekens Dr. Trees De Baerdemaeker Prof. Dr. Rob Ameloot Prof. Dr. Christine E. A. Kirschhock Prof. Dr. Veronique Van Speybroeck Prof. Dr. James M. Mayer Prof. Dr. Dirk De Vos 《Angewandte Chemie (International ed. in English)》2015,54(47):13912-13917
The synthesis of titanium–carboxylate metal–organic frameworks (MOFs) is hampered by the high reactivity of the commonly employed alkoxide precursors. Herein, we present an innovative approach to titanium‐based MOFs by the use of titanocene dichloride to synthesize COK‐69, the first breathing Ti MOF, which is built up from trans‐1,4‐cyclohexanedicarboxylate linkers and an unprecedented [TiIV3(μ3‐O)(O)2(COO)6] cluster. The photoactive properties of COK‐69 were investigated in depth by proton‐coupled electron‐transfer experiments, which revealed that up to one TiIV center per cluster can be photoreduced to TiIII while preserving the structural integrity of the framework. The electronic structure of COK‐69 was determined by molecular modeling, and a band gap of 3.77 eV was found. 相似文献
117.
Dr. Christin Kirst Jonathan Tietze Dr. Peter Mayer Prof. Dr. Hans-Christian Böttcher Prof. Dr. Konstantin Karaghiosoff 《ChemistryOpen》2022,11(3):e202100224
The different coordination behavior of the flexible yet sterically demanding, hemilabile P,N ligand bis(quinoline-2-ylmethyl)phenylphosphine ( bqmpp ) towards selected CuI, AgI and AuI species is described. The resulting X-ray crystal structures reveal interesting coordination geometries. With [Cu(MeCN)4]BF4, compound 1 [Cu2(bqmpp)2](BF4)2 is obtained, wherein the copper(I) atoms display a distorted square planar and square pyramidal geometry. The steric demand and π-stacking of the ligand allow for a short Cu⋅⋅⋅Cu distance (2.588(9) Å). CuI complex 2 [Cu4Cl3(bqmpp)2]BF4 contains a rarely observed Cu4Cl3 cluster, probably enabled by dichloromethane as the chloride source. In the cluster, even shorter Cu⋅⋅⋅Cu distances (2.447(1) Å) are present. The reaction of Ag[SbF6] with the ligand leads to a dinuclear compound ( 3 ) in solution as confirmed by 31P{1H} NMR spectroscopy. During crystallization, instead of the expected phosphine complex 3 , a tris(quinoline-2-ylmethyl)bisphenyl-phosphine ( tqmbp ) compound [Ag2(tqmbp)2](SbF6)2 4 is formed by elimination of quinaldine. The Au(I) compound [Au2(bqmpp)2]PF6 ( 5 ) is prepared as expected and shows a linear arrangement of two phosphine ligands around AuI. 相似文献
118.
119.
K. Schmale J. Barthel M. Bernemann M. Grünebaum S. Koops M. Schmidt J. Mayer H. -D. Wiemhöfer 《Journal of Solid State Electrochemistry》2013,17(11):2897-2907
In this work, fresh and CO2-exposed specimens of Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) are examined by atomic force microscopy (AFM) using amplitude-modulated Kelvin probe force microscopy (KPFM) and also electrostatic force microscopy (EFM) to characterize the early stages of the formation of reaction products due to reaction with gaseous CO2. A comparison is made with results from electron microscopy on the same samples. BSCF specimens exposed for 24 and 240 h to an atmosphere of 99.9 % CO2 at 900 °C, respectively, were analyzed and compared with non-exposed specimens. The observation of interconnected carbonate islands on BSCF forming a continuous carbonate layer after some exposure to CO2 indicates a Stranski–Krastanov or Volmer–Weber growth mechanism of the carbonate layer. Our results demonstrate that the measurement of surface potential variations by means of KPFM and EFM constitutes a very sensitive technique to detect the formation of reaction layers on gas permeation membranes such as BSCF. In contrast to electron microscopy techniques, scanning probe techniques permit the investigation of the topography and of electrochemical characteristics of the sample surface as received and without further preparation. 相似文献
120.
A model of heterogeneous medium taking into account the friction between the particles and liquid, as well as the relaxation
of the small-size particles to the equilibrium on the stress, has been proposed to describe the propagation of the elastic
waves in a suspension. A system of wave equations describing the propagation of a plane longitudinal wave has been formulated
for the components of the medium. Analytical expressions for the sound velocity in a suspension has been obtained in the approximation
in which the particles are completely carried away by liquid in the limiting cases in which the particles are in equilibrium
under stress with the liquid or equilibrium is absent. The dependence of the sound velocity in the medium on the volumetric
portion and the size of the inclusions has been studied. The obtained results agree with the experimental data and obtained
analytical expressions for the sound velocity. The dynamics of the components of the medium at the propagation of the plane
longitudinal monochromatic wave has been studied. 相似文献