全文获取类型
收费全文 | 226篇 |
免费 | 7篇 |
专业分类
化学 | 156篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 24篇 |
物理学 | 46篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 13篇 |
2010年 | 11篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 22篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 1篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1965年 | 1篇 |
1956年 | 1篇 |
1951年 | 1篇 |
1941年 | 1篇 |
1892年 | 1篇 |
排序方式: 共有233条查询结果,搜索用时 15 毫秒
11.
Cotton FA Liu CY Murillo CA Villagrán D Wang X 《Journal of the American Chemical Society》2003,125(44):13564-13575
Reactions of Mo(2)(O(2)CCH(3))(DAniF)(3), DAniF = N,N'-di-p-anisylformamidinate, with oxamidate dianions [ArNC(O)C(O)NAr](2-), Ar = C(6)H(5) and p-anisyl, give pairs of isomeric compounds where the [Mo(2)] units are bridged by the oxamidate anions. For the alpha isomers, the C-C unit of the dianion is nearly perpendicular to the Mo-Mo bonds, and these are essentially perpendicular to each other. For the beta isomers, the corresponding C-C unit and the Mo-Mo bonds are essentially parallel to each other. Each type of isomer is stable in solution. The electronic communication as measured by the DeltaE(1/2) for the oxidation of each of the Mo(2) units is significantly better for the beta isomers. This is supported also by the appearance of what is conventionally called an intervalence charge-transfer band in the near infrared region upon oxidation of the beta isomers but not the alpha isomers. Molecular mechanics and DFT calculations help explain the relative conformations in the alpha isomers and the relative energy differences between the alpha and beta isomers. 相似文献
12.
A route to annulated indoles via a palladium-catalyzed tandem alkylation/direct arylation reaction 总被引:1,自引:0,他引:1
A norbornene-mediated palladium-catalyzed tandem alkylation/C-H functionalization sequence is described, in which an alkyl-aryl bond and a heteroaryl-aryl bond are formed in one pot. A variety of highly substituted six- and seven-membered ring annulated indoles were synthesized in good yields from bromoalkyl indoles and aryl iodides. 相似文献
13.
Dino L. Pisaniello Peter J. Nichols Yves Ducommun Andr E. Merhach 《Helvetica chimica acta》1982,65(3):1025-1028
The temperature- and pressure-dependent equilibria for the addition of an extra N, N-dimethylforrnamide (DMF) or trimethylphosphate (TMP) ligand onto [Nd (DMF)8]3+- and [Nd(TMP)6]3+-species respectively have been measured by visible spectrophotometry. Complementary NMR. studies on other lanthanide ions show a gradual shift in preference for the lower coordination number across the lanthanide series. 相似文献
14.
Dino Berthold Arne G. A. Geissler Sabrina Giofr Bernhard Breit 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):10099-10102
The rhodium‐catalyzed asymmetric intramolecular hydroamination of sulfonyl amides with terminal allenes is reported. It provides selective access to 5‐ and 6‐membered N‐heterocycles, scaffolds found in a large range of different bioactive compounds. Moreover, gram scale reactions, as well as the application of suitable product transformations to natural products and key intermediates thereof are demonstrated. 相似文献
15.
Andrea Giuntoli Nicola Calonaci Sebastiano Bernini Dino Leporini 《Journal of Polymer Science.Polymer Physics》2017,55(23):1760-1769
The relation between elasticity and yielding is investigated in a model polymer solid by Molecular‐Dynamics simulations. By changing the bending stiffness of the chain and the bond length, semicrystalline and disordered glassy polymers — both with bond disorder — as well as nematic glassy polymers with bond ordering are obtained. It is found that in systems with bond disorder the ratio τY/G between the shear yield strength τY and the shear modulus G is close to the universal value of the atomic metallic glasses. The increase of the local nematic order in glasses leads to the increase of the shear modulus and the decrease of the shear yield strength, as observed in experiments on nematic thermosets. A tentative explanation of the subsequent reduction of the ratio τY/G in terms of the distributions of the per‐monomer stress is offered. © 2017 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2017 , 55, 1760–1769 相似文献
16.
Haewon Song Dino Wu Dimitry Mazunin Sizhou M. Liu Yoshikatsu Sato Nicolas Broguiere Marcy Zenobi-Wong Jeffrey W. Bode 《Helvetica chimica acta》2020,103(11):e2000172
Chemical ligation reactions of functional groups that can be masked with two-photon labile protecting groups provide a powerful technology for the three-dimensional patterning of molecules – including proteins – onto hydrogel scaffolds. In order to utilize readily prepared hydrogels constructed by the potassium acyltrifluoroborate (KAT)-hydroxylamine amide formation ligation for two-photon patterning, we have developed a unique post-polymerization protecting group strategy through the reaction of KATs and dithiols in water and deprotection by two-photon excitation. After precise 3D spatially confined light irradiation, the unprotected KATs undergo ligations with hydroxylamine-functionalized superfolder GFP and sulforhodamine B for the composition of three-dimensional patterns. 相似文献
17.
Youte JJ Barbier D Al-Mourabit A Gnecco D Marazano C 《The Journal of organic chemistry》2004,69(8):2737-2740
Potassium ferricyanide oxidation of salt 1 gave isoquinolinone 7 whose treatment with Grignard reagents resulted in a high-yield formation of substituted isoquinolinium salts 5. The selectivity of the reduction of these salts to give derivatives 6 has been studied. Particularly good selectivities (82-84%) were observed when R is a benzylic group. On the basis of these results, a practical and enantioselective synthesis of the natural alkaloid (-)-argemonine is presented. 相似文献
18.
Cotton FA Liu CY Murillo CA Villagrán D Wang X 《Journal of the American Chemical Society》2004,126(45):14822-14831
Very strong electronic communication, manifested in a K(C) value of ca. 10(9), has been found in a system of three compounds separated by one electron oxidation where each compound contains two metal-metal bonded Mo(2)(n+) units linked by a dimethyloxamidate anion, CH(3)N(O)C-C(O)NCH(3)(2)(-). The Mo-Mo distances increase as the oxidation state increases and the bond order decreases, while the diamagnetic, doubly oxidized species becomes essentially planar and resembles a naphthalene molecule. Calculations at the DFT level indicate that a strong transition in the near-IR region, shown by the singly oxidized and paramagnetic species, is best described as a HOMO-1 --> SOMO transition. 相似文献
19.
Maria Luisa Dalla Chiara Roberto Giuntini Antonio Ledda Roberto Leporini Giuseppe Sergioli 《Foundations of Physics》2010,40(9-10):1494-1518
The characteristic holistic features of the quantum theoretic formalism and the intriguing notion of entanglement can be applied to a field that is far from microphysics: logical semantics. Quantum computational logics are new forms of quantum logic that have been suggested by the theory of quantum logical gates in quantum computation. In the standard semantics of these logics, sentences denote quantum information quantities: systems of qubits (quregisters) or, more generally, mixtures of quregisters (qumixes), while logical connectives are interpreted as special quantum logical gates (which have a characteristic reversible and dynamic behavior). In this framework, states of knowledge may be entangled, in such a way that our information about the whole determines our information about the parts; and the procedure cannot be, generally, inverted. In spite of its appealing properties, the standard version of the quantum computational semantics is strongly “Hilbert-space dependent”. This certainly represents a shortcoming for all applications, where real and complex numbers do not generally play any significant role (as happens, for instance, in the case of natural and of artistic languages). We propose an abstract version of quantum computational semantics, where abstract qumixes, quregisters and registers are identified with some special objects (not necessarily living in a Hilbert space), while gates are reversible functions that transform qumixes into qumixes. In this framework, one can give an abstract definition of the notions of superposition and of entangled pieces of information, quite independently of any numerical values. We investigate three different forms of abstract holistic quantum computational logic. 相似文献
20.
Low-coordinate first-row metal complexes of d(0) [vanadium(V)], d(1) [chromium(V)], and d(2) [chromium(IV)] assume the unusual ligand field of a pseudotetrahedron when supported by a tripodal tBu(2)(Me)CO(-) alkoxide framework. Structural, spectroscopic, and reactivity studies, supported by density functional theory calculations, indicate that the d electrons in the chromium(V) and -(IV) oxo complexes reside in metal-oxygen antibonding orbitals, engendering disparate reactivity of the metal-oxo, depending on the number of d electrons present. 相似文献