全文获取类型
收费全文 | 6288篇 |
免费 | 238篇 |
国内免费 | 28篇 |
专业分类
化学 | 4414篇 |
晶体学 | 40篇 |
力学 | 176篇 |
数学 | 965篇 |
物理学 | 959篇 |
出版年
2024年 | 4篇 |
2023年 | 49篇 |
2022年 | 125篇 |
2021年 | 202篇 |
2020年 | 163篇 |
2019年 | 158篇 |
2018年 | 114篇 |
2017年 | 116篇 |
2016年 | 253篇 |
2015年 | 214篇 |
2014年 | 224篇 |
2013年 | 333篇 |
2012年 | 401篇 |
2011年 | 492篇 |
2010年 | 282篇 |
2009年 | 259篇 |
2008年 | 392篇 |
2007年 | 363篇 |
2006年 | 365篇 |
2005年 | 336篇 |
2004年 | 306篇 |
2003年 | 247篇 |
2002年 | 208篇 |
2001年 | 79篇 |
2000年 | 72篇 |
1999年 | 75篇 |
1998年 | 48篇 |
1997年 | 53篇 |
1996年 | 79篇 |
1995年 | 54篇 |
1994年 | 55篇 |
1993年 | 41篇 |
1992年 | 51篇 |
1991年 | 41篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1976年 | 8篇 |
1975年 | 4篇 |
排序方式: 共有6554条查询结果,搜索用时 15 毫秒
931.
We establish a theory of Q -valued functions minimizing a suitable generalization of the Dirichlet integral. In a second paper the theory will be used to approximate efficiently area minimizing currents mod(p) when p = 2Q , and to establish a first general partial regularity theorem for every p in any dimension and codimension . © 2020 Wiley Periodicals LLC. 相似文献
932.
Journal of Global Optimization - A highly influential ingredient of many techniques designed to exploit sparsity in numerical optimization is the so-called chordal extension of a graph... 相似文献
933.
A Quantitative Model for Alkane Nucleophilicity Based on C−H Bond Structural/Topological Descriptors
934.
Physics of Atomic Nuclei - I present an overview of searches for new physics with top and bottom quarks and top quark–antiquark pairs in the final state, using proton–proton collision... 相似文献
935.
Dr. Bozheng Sun Dr. Meagan S. Oakley Dr. Kota Yoshida Yanwen Yang Prof. Matteo Tommasini Dr. Chiara Zanchi Dr. Andrea Lucotti Dr. Michael J. Ferguson Dr. Frank Hampel Prof. Mariusz Klobukowski Prof. Rik R. Tykwinski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(38):e202200616
Cyclic tetraaryl[5]cumulenes ( 1 a–f ) have been synthesized and studied as a function of increasing ring strain. The magnitude of ring strain is approximated by the extent of bending of the cumulenic core as assessed by a combination of X-ray crystallographic analysis and DFT calculations. Trends are observed in 13C NMR, UV-vis, and Raman spectra associated with ring strain, but the effects are small. In particular, the experimental HOMO-LUMO gap is not appreciably affected by bending of the [5]cumulene framework from ca. 174° (λmax=504 nm) in 1 a to ca. 178° (λmax=494 nm) in 1 f . 相似文献
936.
Meccanica - The acoustic dispersion properties of monodimensional waveguide filters can be assessed by means of the simple prototypical mechanical system made of an infinite stack of periodic... 相似文献
937.
Stephanie M. Delgado Sam C. P. Norris Andrea M. Kasko 《Journal of polymer science. Part A, Polymer chemistry》2022,60(5):825-841
Hydrogels are attractive materials for generating 4D shapes due to their ability to undergo pronounced volume changes in response to several stimuli, including light. We previously reported shape-changing hydrogels actuated by long-wave UV and visible light in the presence of live cells using poly(ethylene glycol) macromers incorporating different photodegradable ortho-nitrobenzyl (o-NB) groups. In this comprehensive study, we determine the effect of chemical structure of different o-NB macromers (which influences molar absorptivity and rate constant of degradation), composition (macromer weight percent), fabrication design (initial gel thickness) and environment (ionic strength of solution) on light-induced hydrogel folding. We demonstrate successful photopolymerization and subsequent photodegradation of hydrogels, multistep folding, and live-cell encapsulation. This hydrogel system may be useful as new tool in stem cell differentiation and developmental biology research, facilitating the in vitro investigation of processes that are sensitive to both physical and temporal stimuli. 相似文献
938.
Susanna Gorrasi Andrea Franzetti Roberto Ambrosini Francesca Pittino Marcella Pasqualetti Massimiliano Fenice 《Molecules (Basel, Switzerland)》2021,26(5)
The “Saline di Tarquinia” salterns have been scarcely investigated regarding their microbiological aspects. This work studied the structure and composition of their bacterial communities along the salinity gradient (from the nearby sea through different ponds). The communities showed increasing simplification of pond bacterial diversity along the gradient (particularly if compared to those of the sea). Among the 38 assigned phyla, the most represented were Proteobacteria, Actinobacteria and Bacteroidetes. Differently to other marine salterns, where at the highest salinities Bacteroidetes dominated, preponderance of Proteobacteria was observed. At the genus level the most abundant taxa were Pontimonas, Marivita, Spiribacter, Bordetella, GpVII and Lentibacter. The α-diversity analysis showed that the communities were highly uneven, and the Canonical Correspondence Analysis indicated that they were structured by various factors (sampling site, sampling year, salinity, and sampling month). Moreover, the taxa abundance variation in relation to these significant parameters were investigated by Generalized Linear Models. This work represents the first investigation of a marine saltern, carried out by a metabarcoding approach, which permitted a broad vision of the bacterial diversity, covering both a wide temporal span (two years with monthly sampling) and the entire salinity gradient (from the nearby sea up to the crystallisation ponds). 相似文献
939.
Sebastián Martínez Fernando Igoa Ignacio Carrera Gustavo Seoane Nicolás Veiga Andrea S. S. De Camargo 《Journal of Coordination Chemistry》2018,71(6):874-889
AbstractA new mononuclear complex of zinc(II), [Zn(HL)2]?2DMF (H2L = (E)-N′-((E)-(hydroxyimino)butan-2-ylidene)salicyloylhydrazide, DMF = N,N-dimethylformamide), was prepared and characterized. Single-crystal X-ray crystallography revealed a six-coordinate zinc(II) surrounded by nitrogen of the oxime function and oxygen and distal nitrogens of the acylhydrazone group. This entity also exists in solution as demonstrated by 1H-NMR and potentiometric titrations. The computational analysis showed that the molecular orbitals involved in the main electronic transitions of the complex species in solution are centered on the ligand with negligible contribution of the metal ion. The photophysical properties of the complex were evaluated in solution and in the solid state. Luminescence studies showed that the solid has a strong emission at 550 nm with a large Stokes shift with respect to absorption. The solid state fluorescence emission is ascribed to ligand-centered and/or ligand-to-ligand charge transfer transitions, following the DFT results in solution. A comparison with a previously reported mononuclear [Zn(HL)2] allowed the investigation of the influence of DMF molecules in the structural packing and the luminescence properties. 相似文献
940.
Dr. Benjamin A. Chalmers Hui Xing Sevan Houston Dr. Charlotte Clark Dr. Sussan Ghassabian Dr. Andy Kuo Benjamin Cao Andrea Reitsma Cody‐Ellen P. Murray Dr. Jeanette E. Stok Dr. Glen M. Boyle Carly J. Pierce Stuart W. Littler Prof. David A. Winkler Prof. Paul V. Bernhardt Dr. Cielo Pasay Prof. James J. De Voss Prof. James McCarthy Prof. Peter G. Parsons Prof. Gimme H. Walter Prof. Maree T. Smith Prof. Helen M. Cooper Prof. Susan K. Nilsson Dr. John Tsanaktsidis Dr. G. Paul Savage Prof. Craig M. Williams 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(28):8491-8491