全文获取类型
收费全文 | 1778篇 |
免费 | 35篇 |
国内免费 | 8篇 |
专业分类
化学 | 1061篇 |
晶体学 | 4篇 |
力学 | 30篇 |
数学 | 339篇 |
物理学 | 387篇 |
出版年
2023年 | 18篇 |
2022年 | 15篇 |
2021年 | 24篇 |
2020年 | 31篇 |
2019年 | 24篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 43篇 |
2015年 | 35篇 |
2014年 | 43篇 |
2013年 | 90篇 |
2012年 | 64篇 |
2011年 | 94篇 |
2010年 | 79篇 |
2009年 | 57篇 |
2008年 | 81篇 |
2007年 | 72篇 |
2006年 | 80篇 |
2005年 | 69篇 |
2004年 | 64篇 |
2003年 | 45篇 |
2002年 | 33篇 |
2001年 | 32篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 14篇 |
1992年 | 22篇 |
1991年 | 11篇 |
1990年 | 19篇 |
1989年 | 26篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 17篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 24篇 |
1979年 | 14篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1975年 | 20篇 |
1974年 | 12篇 |
1968年 | 8篇 |
排序方式: 共有1821条查询结果,搜索用时 15 毫秒
1.
Dual-phase-lag equation for heat conduction is analyzed from the point of view of non-equilibrium thermodynamics. Its first-order Taylor series expansion is consistent with the second law as long as the two relaxation times are not negative. 相似文献
2.
3.
Dergez Timea Por Viktria Anditi Bernard Collins Knig-Pter Anik 《Journal of Analytical Chemistry》2022,77(4):513-518
Journal of Analytical Chemistry - Polycyclic aromatic hydrocarbons (PAHs) can be extremely hazardous to human health due to their carcinogenicity and toxicity. Following mother exposure, a part of... 相似文献
4.
5.
6.
Szilrd Varga Pter Angyal Gbor Martin Orsolya Egyed Tams Holczbauer Tibor Sos 《Angewandte Chemie (International ed. in English)》2020,59(32):13547-13551
We report 8‐step syntheses of (?)‐minovincine and (?)‐aspidofractinine using easily available and inexpensive reagents and catalyst. A key element of the strategy was the utilization of a sequence of cascade reactions to rapidly construct the penta‐ and hexacyclic frameworks. These cascade transformations included organocatalytic Michael‐aldol condensation, a multistep anionic Michael‐SN2 cascade reaction, and Mannich reaction interrupted Fischer indolization. To streamline the synthetic routes, we also investigated the deliberate use of steric effect to secure various chemo‐ and regioselective transformations. 相似文献
7.
Mihály V. Pilipecz Tamás R. Varga Péter Králl Zoltán Vincze Zoltán Mucsi Ruth Deme 《合成通讯》2020,50(11):1712-1723
AbstractThe novel push–pull alkene, the 2-(nitro-nitrosomethylene)-pyrrolidine with numerous aliphatic or aromatic amines as nucleophiles afforded amidoximes. Various substituted oxadiazaborole and oxadiazole derivatives were prepared starting from these amidoximes, widening the synthetic applicability of the push–pull alkenes. Acylation of the amidoximes was also examined. The mechanism of the amidoxime formation was investigated by computational methods. 相似文献
8.
Fabio Cameli Prof. Dr. Joop H. ter Horst Dr. René R. E. Steendam Dr. Ir. Christos Xiouras Prof. Dr. Georgios D. Stefanidis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(6):1344-1354
Herein, the pivotal role of secondary nucleation in a crystallization-enhanced deracemization process is reported. During this process, complete and rapid deracemization of chiral conglomerate crystals of an isoindolinone is attained through fast microwave-assisted temperature cycling. A parametric study of the main factors that affect the occurrence of secondary nucleation in this process, namely agitation rate, suspension density, and solute supersaturation, confirms that an enhanced stereoselective secondary nucleation rate maximizes the deracemization rate. Analysis of the system during a single temperature cycle showed that, although stereoselective particle production during the crystallization stage leads to enantiomeric enrichment, undesired kinetic dissolution of smaller particles of the preferred enantiomer occurs during the dissolution step. Therefore, secondary nucleation is crucial for the enhancement of deracemization through temperature cycles and as such should be considered in further design and optimization of this process, as well as in other temperature cycling processes commonly applied in particle engineering. 相似文献
9.
Dr. Gijs M. ter Huurne Dr. Pongphak Chidchob Dr. Augustin Long Prof. Alexandre Martinez Prof. Anja R. A. Palmans Dr. Ghislaine Vantomme 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9964-9970
The design and the characterization of supramolecular additives to control the chain length of benzene-1,3,5-tricarboxamide (BTA) cooperative supramolecular polymers under thermodynamic equilibrium is unraveled. These additives act as chain cappers of supramolecular polymers and feature one face as reactive as the BTA discotic to interact strongly with the polymer end, whereas the other face is nonreactive and therefore impedes further polymerization. Such a design requires fine tuning of the conformational preorganization of the amides and the steric hindrance of the motif. The chain cappers studied are monotopic derivatives of BTA, modified by partial N-methylation of the amides or by positioning of a bulky cyclotriveratrylene cage on one face of the BTA unit. This study not only clarifies the interplay between structural variations and supramolecular interactions, but it also highlights the necessity to combine orthogonal characterization methods, spectroscopy and light scattering, to elucidate the structures and compositions of supramolecular systems. 相似文献
10.
Eckhard Flter Till Wettlaufer Valentina Conty Maria Scharfe 《Molecules (Basel, Switzerland)》2021,26(6)
Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of the structuring systems studied. Examining a single composition decided upon by arbitrary methods does not stimulate progress in the research and technology area. A framework that gives much better guidance to product applications can easily be derived. For example, the incremental structure contribution concept is advocated as a parameter to compare the potency of structuring systems. These can straightforwardly be determined by combining solubility data and structural measurements in the recommended manner. The current method to determine the oil-binding capacity suffers from reproducibility and relevance. A newly developed method is suggested to overcome these shortcomings. The recommended new characterization of oleogels should contribute to a more comprehensive knowledge base necessary for product innovations. 相似文献