全文获取类型
收费全文 | 2068篇 |
免费 | 102篇 |
国内免费 | 12篇 |
专业分类
化学 | 1444篇 |
晶体学 | 2篇 |
力学 | 61篇 |
数学 | 281篇 |
物理学 | 394篇 |
出版年
2023年 | 19篇 |
2022年 | 36篇 |
2021年 | 59篇 |
2020年 | 67篇 |
2019年 | 64篇 |
2018年 | 44篇 |
2017年 | 36篇 |
2016年 | 90篇 |
2015年 | 76篇 |
2014年 | 74篇 |
2013年 | 127篇 |
2012年 | 123篇 |
2011年 | 166篇 |
2010年 | 81篇 |
2009年 | 103篇 |
2008年 | 136篇 |
2007年 | 130篇 |
2006年 | 121篇 |
2005年 | 106篇 |
2004年 | 72篇 |
2003年 | 53篇 |
2002年 | 62篇 |
2001年 | 24篇 |
2000年 | 31篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 15篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1981年 | 7篇 |
1979年 | 10篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1942年 | 6篇 |
1940年 | 3篇 |
1931年 | 3篇 |
1912年 | 4篇 |
1896年 | 3篇 |
排序方式: 共有2182条查询结果,搜索用时 31 毫秒
991.
An integrated microstructural and optical model for carbonaceous mesophases is developed and used to explain the principles that govern the formation and stability of experimentally observed disclination lattices. The model is able to capture the orientation features of disclination lattices, including the type and location of disclination lines, and the orientation field in the mesophase matrix. The optical model based on reflection polarized optical microscopy is able to replicate all the details observed in actual observations. The typical brush figures have the proper distribution, orientation, and intensity. The computational predictions offer science-based routes to create and control desirable material architectures based on carbonaceous mesophase-carbon fiber composites. 相似文献
992.
993.
- Download : Download high-res image (181KB)
- Download : Download full-size image
994.
Xue Dong Said Jalife Alejandro Vásquez‐Espinal Estefanía Ravell Dr. Sudip Pan Dr. José Luis Cabellos Wei‐yan Liang Prof. Dr. Zhong‐hua Cui Prof. Dr. Gabriel Merino 《Angewandte Chemie (International ed. in English)》2018,57(17):4627-4631
An intriguing structural transition from the quasi‐planar form of B12 cluster upon the interaction with lithium atoms is reported. High‐level computations show that the lowest energy structures of LiB12, Li2B12, and Li3B12 have quasi‐planar (Cs), tubular (D6d), and cage‐like (Cs) geometries, respectively. The energetic cost of distorting the B12 quasi‐planar fragment is overcompensated by an enhanced electrostatic interaction between the Li cations and the tubular or cage‐like B12 fragments, which is the main reason of such drastic structural changes, resulting in the smallest tubular (Li2B12) and cage‐like (Li3B12) boron structures reported to date. 相似文献
995.
Alejandro Maass Servet Martí nez 《Proceedings of the American Mathematical Society》1998,126(4):1219-1230
Let , be mixing one-sided subshifts of finite type such that . We show a necessary and sufficient condition for the existence of mixing Markov shifts , , , and a conjugacy with , such that the sets of letters appearing in both systems are the same, more precisely, .
996.
Computational modeling of texture formation in coupled phase separation-phase ordering processes in polymer/liquid crystal mixtures is performed using a unified model based on the nematic tensor order parameter and gradient orientation elasticity. The computational methods are able to resolve defect nucleation, defect-defect interactions, and defect-particle interactions, as well as global and local morphological features in the concentration and order parameter spatiotemporal behavior. Biphasic structures corresponding to polymer dispersed liquid crystals (PDLCs), crystalline filled nematic (CFNs), and random filled nematics (RFNs) are captured and analyzed using liquid crystal defect physics and structure factors. Under spinodal decomposition due to concentration fluctuations, the PDLC structure emerges, and the nucleation and repulsive interaction of defects within nematic droplets leads to bipolar nematic droplets. Under spinodal decomposition due to ordering fluctuations, the CFNs structure emerges, and the stable polymer droplet crystal is pinned by a lattice of topological defects. For intermediate cases, where the mixture is unstable to both concentration and nematic order fluctuations, the RFN structure emerges, and polymer droplets and fibrils are pinned by a defect network, whose density increases with the curvature of the polymer-liquid crystal interface. The simulations provide an information of the role of topological defects on phase separation-phase ordering processes in polymer-liquid crystal mixtures. 相似文献
997.
Lidia Montero Elena Ibáñez Mariateresa Russo Rosa di Sanzo Luca Rastrelli Anna Lisa Piccinelli Rita Celano Alejandro Cifuentes Miguel Herrero 《Analytica chimica acta》2016
Profiling of the main metabolites from several licorice (Glycyrrhiza glabra) samples collected at different locations is carried out in this work by using comprehensive two-dimensional liquid chromatography (LC × LC) coupled to diode array (DAD) and mass spectrometry (MS) detectors. The optimized method was based on the application of a HILIC-based separation in the first dimension combined with fast RP-based second dimension separation. This set-up was shown to possess powerful separation capabilities allowing separating as much as 89 different metabolites in a single sample. Identification and grouping of metabolites according to their chemical class were achieved using the DAD, MS and MS/MS data. Triterpene saponins were the most abundant metabolites followed by glycosylated flavanones and chalcones, whereas glycyrrhizic acid, as expected, was confirmed as the main component in all the studied samples. LC × LC-DAD-MS/MS was able to resolve these complex licorice samples providing with specific metabolite profiles to the different licorice samples depending on their geographical origin. Namely, from 19 to 50 specific compounds were exclusively determined in the 2D-chromatograms from the different licorice samples depending on their geographical origin, which can be used as a typical pattern that could potentially be related to their geographical location and authentication. 相似文献
998.
SIMPRE1.2: Considering the hyperfine and quadrupolar couplings and the nuclear spin bath decoherence
下载免费PDF全文
![点击此处可从《Journal of computational chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Salvador Cardona‐Serra Luis Escalera‐Moreno José J. Baldoví Alejandro Gaita‐Ariño Juan M. Clemente‐Juan Eugenio Coronado 《Journal of computational chemistry》2016,37(13):1238-1244
SIMPRE is a fortran77 code which uses an effective electrostatic model of point charges to predict the magnetic behavior of rare‐earth‐based mononuclear complexes. In this article, we present SIMPRE1.2, which now takes into account two further phenomena. First, SIMPRE now considers the hyperfine and quadrupolar interactions within the rare‐earth ion, resulting in a more complete and realistic set of energy levels and wave functions. Second, and to widen SIMPRE's predictive capabilities regarding potential molecular spin qubits, it now includes a routine that calculates an upper‐bound estimate of the decoherence time considering only the dipolar coupling between the electron spin and the surrounding nuclear spin bath. Additionally, SIMPRE now allows the user to introduce the crystal field parameters manually. Thus, we are able to demonstrate the new features using as examples (i) a Gd‐based mononuclear complex known for its properties both as a single ion magnet and as a coherent qubit and (ii) an Er‐based mononuclear complex. © 2016 Wiley Periodicals, Inc. 相似文献
999.
Boris I. Kharisov Alejandro Vázquez Dimas Idalia Gómez De La Fuente Yolanda Peña Méndez 《Journal of Coordination Chemistry》2016,69(7):1125-1151
Recent advances in the functionalization of graphene (G) and graphene oxide (GO) using classical coordination complexes, as well as σ- and π-organometallic compounds as precursors, are discussed. Graphene can form hybrids via covalent or non-covalent interactions with metal complexes of carboxylates, amines, polypyridine compounds, a host of N,O-containing ligands, porphyrins, phthalocyanines, carbonyls, cyclopentadienyls, pyrene-containing moieties, and other aromatic structures. The hybrid constructs are interesting for applications in catalysis, energy storage, and corrosion inhibition and present interesting possibilities of modulating the electronic structure of graphene. 相似文献
1000.