全文获取类型
收费全文 | 6834篇 |
免费 | 820篇 |
国内免费 | 214篇 |
专业分类
化学 | 5453篇 |
晶体学 | 96篇 |
力学 | 189篇 |
综合类 | 2篇 |
数学 | 107篇 |
物理学 | 2021篇 |
出版年
2023年 | 78篇 |
2022年 | 95篇 |
2021年 | 216篇 |
2020年 | 353篇 |
2019年 | 244篇 |
2018年 | 168篇 |
2017年 | 178篇 |
2016年 | 299篇 |
2015年 | 315篇 |
2014年 | 351篇 |
2013年 | 456篇 |
2012年 | 410篇 |
2011年 | 376篇 |
2010年 | 274篇 |
2009年 | 377篇 |
2008年 | 425篇 |
2007年 | 508篇 |
2006年 | 373篇 |
2005年 | 298篇 |
2004年 | 245篇 |
2003年 | 273篇 |
2002年 | 213篇 |
2001年 | 188篇 |
2000年 | 149篇 |
1999年 | 125篇 |
1998年 | 113篇 |
1997年 | 69篇 |
1996年 | 75篇 |
1995年 | 76篇 |
1994年 | 51篇 |
1993年 | 56篇 |
1992年 | 46篇 |
1991年 | 43篇 |
1990年 | 38篇 |
1989年 | 36篇 |
1988年 | 34篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1974年 | 10篇 |
1973年 | 6篇 |
排序方式: 共有7868条查询结果,搜索用时 15 毫秒
61.
Molecular dynamic study of dielectric polarization and ferroelectricity in a model polar polymer 下载免费PDF全文
Jeffrey P. Calame 《Journal of Polymer Science.Polymer Physics》2015,53(10):740-759
Molecular dynamics simulations are used to explore the polarization response of a lamellar crystal consisting of folded chains of a highly simplified model polar polymer. The system is based on a united atom model of polyethylene with constrained bond lengths and bond angles, and it is endowed with artificial partial charges placed on the united atoms to give it a simple polar character. Simulations performed with various temperatures, electric field directions, and electric field application histories reveal a complicated sequence of reorientation processes, including pronounced ferroelectric behavior. The sequence includes a weak, temperature‐independent prompt response, and a slow‐rising delay regime with stretched exponential behavior and thermally‐activated reorientation parameters consistent with trans‐gauche (TG) barrier crossings in the amorphous phase. When the delay regime has progressed sufficiently, a primary large‐amplitude response due to organized rotation of large subsegments in the crystalline phase occurs in a rapid manner that requires relatively few TG barrier crossings. A final, extremely slow rise in residual polarization completes the sequence. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 740–759 相似文献
62.
Back Cover: Spontaneous Stepwise Self‐Assembly of a Polyoxometalate–Organic Hybrid into Catalytically Active One‐Dimensional Anisotropic Structures (Chem. Eur. J. 31/2014) 下载免费PDF全文
63.
Dr. N. Kodiah Beyeh Dr. Fangfang Pan Dr. Sandip Bhowmik Toni Mäkelä Prof. Robin H. A. Ras Acad. Prof. Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1355-1361
N‐Alkyl ammonium resorcinarene salts (NARYs, Y=triflate, picrate, nitrate, trifluoroacetates and NARBr) as tetravalent receptors, are shown to have a strong affinity for chlorides. The high affinity for chlorides was confirmed from a multitude of exchange experiments in solution (NMR and UV/Vis), gas phase (mass spectrometry), and solid‐state (X‐ray crystallography). A new tetra‐iodide resorcinarene salt (NARI) was isolated and fully characterized from exchange experiments in the solid‐state. Competition experiments with a known monovalent bis‐urea receptor ( 5 ) with strong affinity for chloride, reveals these receptors to have a much higher affinity for the first two chlorides, a similar affinity as 5 for the third chloride, and lower affinity for the fourth chloride. The receptors affinity toward chloride follows the trend K1?K2?K3≈ 5 >K4, with Ka=5011 m ?1 for 5 in 9:1 CDCl3/[D6]DMSO. 相似文献
64.
Neal P. Mankad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5822-5829
An emerging area of homogeneous catalysis is the use of catalysts featuring two closely associated metal sites. This approach complements the traditional focus on single‐site catalysts and makes available new parameters with which to optimize catalytic behavior. Single‐site catalysts are optimized through changing 1) the identity of the metal, and 2) the steric and electronic properties of the ligands. Bimetallic catalysts introduce new optimization parameters such as 3) catalyst nuclearity (mononuclear vs. binuclear), and 4) bimetallic pairing (relative compatibility of two metal sites). In order to harness these new optimization parameters in developing systems, it is necessary to first understand the origin of bimetallic selectivity effects that already have been documented. This Concept article highlights bimetallic effects on the chemo‐, regio‐, and stereoselectivity of catalytic transformations, using selected case studies from the recent literature as illustrative examples. 相似文献
65.
Highly Phosphorescent Crystals of Square‐Planar Platinum Complexes with Chiral Organometallic Linkers: Homochiral versus Heterochiral Arrangements,Induced Circular Dichroism,and TD‐DFT Calculations 下载免费PDF全文
Dr. Hugo Sesolis Dr. Julien Dubarle‐Offner Dr. Carmen K. M. Chan Emmanuel Puig Geoffrey Gontard Pierre Winter Prof. Andrew L. Cooksy Prof. Vivian W. W. Yam Dr. Hani Amouri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8032-8037
A novel class of chiral luminescent square‐planar platinum complexes with a π‐bonded chiral thioquinonoid ligand is described. Remarkably the presence of this chiral organometallic ligand controls the aggregation of this square planar luminophor and imposes a homo‐ or hetero‐chiral arrangement at the supramolecular level, displaying non‐covalent Pt–Pt and π–π interactions. Interestingly these complexes are highly luminescent in the crystalline state and their photophysical properties can be traced to their aggregation in the solid state. A TD‐DFT calculation is obtained to rationalize this unique behavior. 相似文献
66.
67.
68.
Back Cover: Constrained Peptides with Target‐Adapted Cross‐Links as Inhibitors of a Pathogenic Protein–Protein Interaction (Angew. Chem. Int. Ed. 9/2014) 下载免费PDF全文
69.
Mahdi Muhammad Moosa Dr. Allan Chris M. Ferreon Prof. Dr. Ashok A. Deniz 《Chemphyschem》2015,16(1):90-94
Intrinsically disordered proteins (IDPs) are involved in diverse cellular functions. Many IDPs can interact with multiple binding partners, resulting in their folding into alternative ligand‐specific functional structures. For such multi‐structural IDPs, a key question is whether these multiple structures are fully encoded in the protein sequence, as is the case in many globular proteins. To answer this question, here we employed a combination of single‐molecule and ensemble techniques to compare ligand‐induced and osmolyte‐forced folding of α‐synuclein. Our results reveal context‐dependent modulation of the protein′s folding landscape, suggesting that the codes for the protein′s native folds are partially encoded in its primary sequence, and are completed only upon interaction with binding partners. Our findings suggest a critical role for cellular interactions in expanding the repertoire of folds and functions available to disordered proteins. 相似文献
70.
Experimental Charge Density Evidence for Pnicogen Bonding in a Crystal of Ammonium Chloride 下载免费PDF全文
Dr. Yulia V. Nelyubina Prof. Alexander A. Korlyukov Prof. Konstantin A. Lyssenko 《Chemphyschem》2015,16(3):676-681
Chemical binding in crystalline ammonium chloride, a simple inorganic salt with an unexpectedly complex bonding pattern, was studied by using a topological analysis of electron density function derived from high‐resolution X‐ray diffraction. Supported by periodic quantum chemical calculations, it provided experimental evidence for weak σ‐hole bonds (1.5 kcal mol?1) that involve ammonium cations in a crystal. Our results show this type of supramolecular interaction to be more numerous than has been found to date by using gas‐phase calculations or statistical analysis of CSD. 相似文献