全文获取类型
收费全文 | 349篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 272篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 23篇 |
物理学 | 54篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 30篇 |
2012年 | 42篇 |
2011年 | 34篇 |
2010年 | 22篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 17篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有367条查询结果,搜索用时 281 毫秒
231.
Bozorgmehri Babak Yu Xinxin Matikainen Marko K. Harish Ajay B. Mikkola Aki 《Nonlinear dynamics》2021,103(1):581-616
Nonlinear Dynamics - This paper introduces a procedure in the field of computational contact mechanics to analyze contact dynamics of beams undergoing large overall motion with large deformations... 相似文献
232.
Allene esters are unique not only as excellent electrophiles but also because of their ability for subsequent reactivity after the initial nucleophilic attack. A mechanistically inspired cyclization using ethyl-2,3-butadienoate and acyclic enones to provide dihydropyrans in excellent yields and enantioselectivity under solvent-free conditions at room temperature is reported. 相似文献
233.
Behrouz Shaabani Prof. Dr. Babak Mirtamizdoust Davide Viterbo Gianluca Croce Hassan Hammud 《无机化学与普通化学杂志》2010,636(8):1596-1600
. A novel 1D PbII coordination polymer [Pb(dmp)I2]n ( 1 ) (dmp = 2,9‐dimethyl‐1,10‐phenanthroline) containing a Pb2‐(μ‐I)2 unit was synthesized and characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopy and studied by thermal analysis as well as X‐ray crystallography. The single‐crystal X‐ray data show that the coordination number of PbII ions is six, i.e. PbN2I4, with “stereo‐chemically active” electron lone pairs, and the coordination sphere is asymmetrical. They also show that the chains interact with each other through π‐π stacking interactions, which create a 3D framework. The structure of the title complex has been optimized by density functional theory calculations. The calculated structural parameters and the IR spectra of the title complex are in agreement with the crystal structure. 相似文献
234.
Babak Karimi Prof. Dr. Dawood Elhamifar Dr. James H. Clark Prof. Dr. Andrew J. Hunt Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(27):8047-8053
The preparation of a novel palladium‐supported periodic mesoporous organosilica based on alkylimidazolium ionic liquid (Pd@PMO‐IL) in which imidazoilium ionic liquid is uniformly distributed in the silica mesoporous framework is described. Both Pd@PMO‐IL and the parent PMO‐IL were characterized by N2‐adsorption–desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), TEM, and solid‐state NMR spectroscopy. We have demonstrated that Pd@PMO‐IL is an efficient and reusable catalyst for the Suzuki–Miyaura coupling reaction of various types of iodo‐, bromo‐, and even deactivated aryl chlorides in water. It was also found that although the PMO‐IL nanostructure acts as reservoir for soluble Pd species, it can also operate as a nanoscaffold to recapture the Pd nanoparticles into the mesochannels thus preventing extensive agglomeration of Pd. This observation might be attributed to the isolated ionic liquid units that effectively control the reaction mechanism by preventing Pd agglomeration and releasing and recapturing Pd nanoparticles during the reaction process. The catalyst can be recovered and reused for at least four reaction cycles without significant loss of activity. 相似文献
235.
236.
Oxygenation of sulfides catalysed by SBA‐15‐immobilized molybdenum(VI) complex of a bis(phenol) diamine ligand using aqueous hydrogen peroxide as a green oxidant 下载免费PDF全文
A highly efficient and reusable molybdenum‐based catalyst has been synthesized by covalent grafting of a bis(phenol) diamine ligand, namely 2‐(((2‐bromoethyl)(2‐((3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)amino)ethyl)amino)methyl)‐4,6‐di‐tert‐butylphenol, onto functionalized ordered mesoporous silica (SBA‐15) followed by complexation with MoO2(acac)2. The resulting organic–inorganic hybrid material was found to be a highly effective catalyst for oxygenation of various sulfides to their corresponding sulfoxides or sulfones. The catalyst was characterized using transmission and scanning electron microscopies, X‐ray photoelectron, Fourier transform infrared and atomic absorption spectroscopies, Brunauer–Emmett–Teller surface area analysis and thermogravimetric analysis. Mild reaction conditions, high selectivity and easy recovery and reusability of the catalyst render the presented protocol very useful for addressing industrial needs and environmental concerns. 相似文献
237.
238.
Maria V. Babak Samuel M. Meier Anton A. Legin Mahsa S. Adib Razavi Alexander Roller Dr. Michael A. Jakupec Prof. Dr. Bernhard K. Keppler Prof. Dr. Christian G. Hartinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(13):4308-4318
With the aim of systematically studying fundamental structure–activity relationships as a basis for the development of RuII arene complexes (arene=p‐cymene or biphenyl) bearing mono‐, bi‐, or tridentate am(m)ine ligands as anticancer agents, a series of ammine, ethylenediamine, and diethylenetriamine complexes were prepared by different synthetic routes. Especially the synthesis of mono‐, di‐, and triammine complexes was found to be highly dependent on the reaction conditions, such as stoichiometry, temperature, and time. Hydrolysis and protein‐binding studies were performed to determine the reactivity of the compounds, and only those containing chlorido ligands undergo aquation or form protein adducts. These properties correlate well with in vitro tumor‐inhibiting potency of the compounds. The complexes were found to be active in anticancer assays when meeting the following criteria: stability in aqueous solution and low rates of hydrolysis and binding to proteins. Therefore, the complexes least reactive to proteins were found to be the most cytotoxic in cancer cells. In general, complexes with biphenyl as arene ligand inhibited the growth of tumor cells more effectively than the cymene analogues, consistent with the increase in lipophilicity. This study highlights the importance of finding a proper balance between reactivity and stability in the development of organometallic anticancer agents. 相似文献
239.
Abadie J Abbott BP Abbott R Abernathy M Accadia T Acernese F Adams C Adhikari R Ajith P Allen B Allen GS Ceron EA Amin RS Anderson SB Anderson WG Antonucci F Arain MA Araya MC Aronsson M Arun KG Aso Y Aston SM Astone P Atkinson D Aufmuth P Aulbert C Babak S Baker P Ballardin G Ballmer S Barker D Barnum S Barone F Barr B Barriga P Barsotti L Barsuglia M Barton MA Bartos I Bassiri R Bastarrika M Bauchrowitz J Bauer TS Behnke B Beker MG Belletoile A Benacquista M Bertolini A Betzwieser J 《Physical review letters》2011,107(27):271102
The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10(-50) strain(2)?Hz(-1) and 5-35×10(-49) strain(2)?Hz(-1)?sr(-1) for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10(-25) in the most sensitive frequency range near 160 Hz. 相似文献
240.
Dr. Behrouz Shaabani Babak Mirtamizdoust Davide Viterbo Gianluca Croce Hassan Hammud Pejman Hojati‐Lalemi Aliakbar Khandar 《无机化学与普通化学杂志》2011,637(6):713-719
A new nanostructured coordination polymer of divalent lead with the ligand 2,9‐dimethyl‐1,10‐phenanthroline (dmp), [Pb(dmp)(μ‐N3)(μ‐NO3)]n ( 1 ), was synthesized by sonochemical methods. The polymer was characterized by scanning electron microscopy, X‐ray powder diffraction, IR, 1H NMR, and 13C NMR spectroscopy, and elemental analyses. Compound 1 was structurally characterized by single‐crystal X‐ray diffraction. The single‐crystal analysis shows that the coordination number of PbII ions is seven, (PbN4O3) has a “stereo‐chemically active” electron lone pair, and the coordination sphere is hemidirected. The chains interact with each other through π–π stacking interactions to create a 3D framework. The structure of the title complex was optimized by density functional calculations. The calculated structural parameters and the IR spectrum of the title complex are in agreement with the crystal structure. 相似文献