全文获取类型
收费全文 | 752篇 |
免费 | 31篇 |
国内免费 | 8篇 |
专业分类
化学 | 539篇 |
晶体学 | 4篇 |
力学 | 24篇 |
数学 | 82篇 |
物理学 | 142篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 23篇 |
2020年 | 31篇 |
2019年 | 30篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 31篇 |
2015年 | 8篇 |
2014年 | 28篇 |
2013年 | 37篇 |
2012年 | 77篇 |
2011年 | 66篇 |
2010年 | 41篇 |
2009年 | 33篇 |
2008年 | 48篇 |
2007年 | 58篇 |
2006年 | 59篇 |
2005年 | 32篇 |
2004年 | 18篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有791条查询结果,搜索用时 953 毫秒
71.
Mauricio Arias Javier Concepción Irma Crivelli Alvaro Delgadillo Ramiro Díaz Angélica Francois Francisco Gajardo Rosa López Ana María Leiva Bárbara Loeb 《Chemical physics》2006
Different strategies to improve the excited state properties of polypyridinic complexes by varying ligand structure and molecular geometry are described. Bidentate and tetradentate ligands based on fragments as dipyrido[3,2-a:2′,3′-c]phenazine, dppz, and pyrazino[2,3-f][1,10]-phenanthroline, ppl, have been used. Quinonic residues were fused to these basic units to improve acceptor properties. Photophysical studies were performed in order to test theoretical predictions. 相似文献
72.
73.
The classification of the equilibrium shapes that a self-gravitating fluid can take in a Riemannian manifold is a classical problem in Mathematical Physics. In this paper it is proved that the equilibrium shapes are isoparametric submanifolds. Some geometric properties of them are also obtained, e.g. classification and existence for some Riemannian spaces and relationship with the isoperimetric problem and the group of isometries of the manifold. Our approach to the problem is geometrical and allows to study the equilibrium shapes on general Riemannian spaces. 相似文献
74.
Walter Ferrer Santos Alvaro Rittatore 《Proceedings of the American Mathematical Society》2007,135(4):961-968
In this paper we axiomatize some constructions and results due to Cayley and Hilbert. We define the concept of -process for an arbitrary affine algebraic monoid with zero and unit group . In our situation we show how to produce from the process and for a linear rational representation of a number of elements of the ring of -invariants that is large enough to guarantee its finite generation. Moreover, using complete reducibility, we give an explicit construction of all -processes for reductive monoids.
75.
Corrigendum: Crowdsourcing Natural Products Discovery to Access Uncharted Dimensions of Fungal Metabolite Diversity
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
76.
Dr. Desmond MacLeod Carey Dr. Tatiana Gomez Dr. Cesar Morales-Verdejo Dr. Alvaro Muñoz-Castro 《ChemistryOpen》2015,4(5):651-655
The complexation of metal cations into a host–guest situation is particularly well exemplified by [2.2.2]paracyclophane and AgI, which leads to a strong cation–π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation–π interaction in a host–guest scenario. From an analysis of certain components of the induced magnetic field and the 13C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host–guest pairs involving both inorganic and organic hosts. 相似文献
77.
A numerical investigation was conducted to analyze the unsteady laminar flow field and heat transfer characteristics in a
plane channel with two square bars mounted side by side to the approaching flow. A finite volume technique is applied with
a fine grid and time resolution. The transverse separation distance between the bars (G/d) is varied from 0 to 5, whereas
the bar height to channel height is d/H=1/8, and the channel length is L=5H. Different flow regimes develop in the channel
due the interaction between the two mounted square bars, steady flow, flow with vortex shedding synchronization either in
phase or in anti-phase, or biased flow with low frequency modulation of vortex shedding are found. Results show that the pressure
drop increase and heat transfer enhancement are strongly dependent of the transverse separation distance of the bars and the
channel Reynolds number. 相似文献
78.
Demesa Balderrama G Meneses EP Hernández Orihuela L Villa Hernández O Castro Franco R Pando Robles V Ferreira Batista CV 《Rapid communications in mass spectrometry : RCM》2011,25(8):1017-1027
Immobilized metal ion affinity chromatography (IMAC) has been widely used for the enrichment of phosphopeptides, whereas no report exists describing the use of IMAC columns for the enrichment of sulfopeptides. In this study, we used IMAC-Ga microcolumns for the enrichment of sulfopeptides from a complex mixture of peptides, extracted from skin secretions of the Pachymedusa dacnicolor frog. The enriched fraction obtained by IMAC-Ga was analyzed by liquid chromatograpy/electrospray ionization mass spectrometry (LC/ESI-MS) in an Orbitrap XL and by matrix-assisted laser desorption/ionization time-of-flight time-of-flight (MALDI-TOF/TOF) in an ABI 4800 instrument. From this fraction, different sulfated and non-sulfated peptides belonging to the caerulin and bradykinin families were structurally characterized. Other interesting negatively charged groups, such as phosphate adducts of dermaseptins and pyridoxal phosphate attached to a protease inhibitor, were also characterized. Unexpectedly, some dermaseptin antimicrobial peptides were also enriched by IMAC-Ga and a Sauvatine-like peptide was also fully sequenced. Furthermore, neutral loss of sulfated peptides and their fragmentation patterns in the gas phase were also compared using collision-induced dissociation (CID) and high-energy collision dissociation (HCD). Our present study provides evidence that IMAC-Ga enrichment is a fast, useful and promising method for high-throughput analysis of sulfated-peptides, since high-resolution mass spectrometers can be used for this purpose. 相似文献
79.
Valdés A Prosmiti R Villarreal P Delgado-Barrio G 《The Journal of chemical physics》2011,135(24):244309
Benchmark, full-dimensional calculations on the ground and excited vibrational states for the tetra-, and penta-atomic weakly bound He(2,3)ICl complexes are reported. The representation of the potential energy surfaces includes three-body HeICl potentials parameterized to coupled-cluster singles, doubles, and perturbative triples ab initio data. These terms are important in accurately describing the interactions of such highly floppy systems. The corresponding 6D/9D computations are performed with the multi-configuration time dependent Hartree method, using natural potential fits, and a mode combination scheme to optimize the computational effort in the improved relaxation calculations. For these complexes several low-lying vibrational states are computed, and their binding energies and radial/angular probability density distributions are obtained. We found various isomers which are assigned to different structural models related with combinations of the triatomic isomers, like linear, T-shaped, and antilinear ones. Comparison of these results with recent experimental data is presented, and the quantitative deviations found with respect to the experiment are discussed. 相似文献
80.
José O. Valderrama Alvaro Toro Roberto E. Rojas 《The Journal of chemical thermodynamics》2011,43(7):1068-1073
A simple and accurate group contribution method to estimate the heat capacity of ionic liquids is presented. The method considers groups previously defined for a successful method used to estimate critical properties of ionic liquids. Additionally a structural parameter known as mass connectivity index recently defined by the authors has been incorporated to define the model equation. To better define the values of the groups, heat capacity data at 298 K for 126 organic substances were used with the 469 heat capacity data for 32 ionic liquids. The results were compared with experimental data and with values reported by other available estimation methods. Results show that the new group contribution method gives low deviations and can be used with confidence in thermodynamic and engineering calculations. 相似文献