全文获取类型
收费全文 | 792篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
化学 | 525篇 |
晶体学 | 16篇 |
力学 | 17篇 |
数学 | 75篇 |
物理学 | 200篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 32篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 17篇 |
2014年 | 40篇 |
2013年 | 54篇 |
2012年 | 58篇 |
2011年 | 78篇 |
2010年 | 35篇 |
2009年 | 32篇 |
2008年 | 29篇 |
2007年 | 48篇 |
2006年 | 41篇 |
2005年 | 27篇 |
2004年 | 18篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 3篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1973年 | 6篇 |
1961年 | 2篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1941年 | 2篇 |
排序方式: 共有833条查询结果,搜索用时 546 毫秒
641.
In this paper we give some integer programming formulations for the Steiner tree problem on undirected and directed graphs and study the associated polyhedra. We give some families of facets for the undirected case along with some compositions and extensions. We also give a projection that relates the Steiner tree polyhedron on an undirected graph to the polyhedron for the corresponding directed graph. This is used to show that the LP-relaxation of the directed formulation is superior to the LP-relaxation of the undirected one.Corresponding author. 相似文献
642.
Deepak Kumar 《Pramana》2002,59(2):329-336
Quantum aspects of optical polarization are discussed for waves traveling in anisotropic dielectric media with a view to relate
the dynamics of polarization with that of photon spin and its manipulation by classical polarizers. 相似文献
643.
D. Chopra H.W. Axe T.K. Hatwar 《Journal of Electron Spectroscopy and Related Phenomena》1984,33(2):141-152
Spectral characteristics representing the distribution of unoccupied conduction-band states in the 3d transition-series metals Fe, Co, Ni and Cu, obtained using soft X-ray absorption (SXA), bremsstrahlung isochromat (BI) and characteristic isochromat (CI) methods, are related mathematically to those found in soft X-ray appearance-potential Spectroscopy (SXAPS) on the basis of the one-electron band approximation. These mathematical relationships are used to compute SXAPS spectra from reported experimental data obtained by the SXA, BI and CI methods. For the metals considered, the correlations between the computed and experimental SXAPS spectra are found to be good. The observed discrepancies are attributed to differences in the selection rules of the excitation processes, to the effect of the core vacancy on the final state, and to many-body phenomena which are not included in the simplified one-electron band model. 相似文献
644.
用N-(2-甲基)苯基甘氨酸合成了几种(硼、铝、铁、砷和锑)及四价(硅、钛和硒)金属/非金属衍生物。合成是在苯溶液中采用了金属/非金属的异丙氧基化合物和N-(2-甲基)苯基甘氨酸按1∶1和1∶2的配比完成的。一般情况下,合成的产物均为有色固体,以及在产物中有异丙氧基基团残留而显吸湿性。对所制成的衍生物均采用了共沸混合物分析、元素分析和光谱测定等进行了表征。 相似文献
645.
In view of potent antimicrobial and anti-inflammatory activities exhibited by 5-substituted imidazolones, a variety of novel imidazolone analogs 3a-l were synthesized by the condensation of different substituted oxazolones 1 with various aromatic amines 2. All the synthesized compounds were screened for in vitro activities against a panel of Gram-positive and Gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans. Several analogs produced good or moderate activities particularly against the tested Gram-positive bacteria Micrococcus luteus and Gram-negative bacteria Pseudomonas aeruginosa and. Meanwhile, compounds 3b and 3c displayed marked antifungal activity against C. albicans. In addition, the in vivo anti-inflammatory activity of the synthesized compounds was determined using the carrageenin-induced paw oedema method in rats. Two of 5-substituted imidazolone derivatives, 3k and 3d show good anti-inflammatory activity. The structures of all the newly synthesized compounds were elucidated using IR, 1H NMR and 13C NMR. 相似文献
646.
647.
Penicillic acid was isolated from Aspergillus sclerotiorum and converted into 6-iodo-α-pyran-2,5-diones using iodolactonization, a key intermediate for the synthesis of pectinolide F. Structures of penicillic acid and its iodolactonized product were confirmed by using NMR experiments. 相似文献
648.
Gold‐catalyzed Intermolecular Oxidations of 2‐Ketonyl‐1‐ethynyl Benzenes with N‐Hydoxyanilines to Yield 2‐Aminoindenones via Gold Carbene Intermediates
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)
Bhanudas Dattatray Mokar Dr. Deepak B. Huple Prof. Dr. Rai‐Shung Liu 《Angewandte Chemie (International ed. in English)》2016,55(39):11892-11896
Gold‐catalyzed oxidations of 2‐ketonyl‐1‐ethynyl benzenes with N‐hydroxyanilines yield 2‐aminoindenone derivatives efficiently. Experimental data suggests that this process involves an α‐oxo gold carbene intermediate, generated from the attack of N‐hydroxyaniline on furylgold carbene intermediate, rather than the typical attack of oxidants on π‐alkynes. 相似文献
649.
Let be drawn uniformly from all m‐edge, k‐uniform, k‐partite hypergraphs where each part of the partition is a disjoint copy of . We let be an edge colored version, where we color each edge randomly from one of colors. We show that if and where K is sufficiently large then w.h.p. there is a rainbow colored perfect matching. I.e. a perfect matching in which every edge has a different color. We also show that if n is even and where K is sufficiently large then w.h.p. there is a rainbow colored Hamilton cycle in . Here denotes a random edge coloring of with n colors. When n is odd, our proof requires for there to be a rainbow Hamilton cycle. © 2015 Wiley Periodicals, Inc. Random Struct. Alg., 48, 503–523, 2016 相似文献
650.