全文获取类型
收费全文 | 498篇 |
免费 | 38篇 |
专业分类
化学 | 424篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 29篇 |
物理学 | 79篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 13篇 |
2020年 | 18篇 |
2019年 | 36篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 56篇 |
2011年 | 62篇 |
2010年 | 19篇 |
2009年 | 16篇 |
2008年 | 46篇 |
2007年 | 34篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有536条查询结果,搜索用时 434 毫秒
111.
A variant of the orthogonal gradient method of orbital optimization in the INDO-MCSCF framework has been used to study the
photochemical decomposition of the HNO molecule into H + NO in the lowest1.3A″ states. A complete geometry optimization has been carried out at all points of the reaction path which appears to be almost
barrierless. The one-electron density matrix extracted from the optimized wavefunction at each point has been used to generate
the relevant sets of quantum chemical valence parameters. A sharp transition is noted in the N-H bond order and hydrogen free
valence index when plotted as functions of rNH. This enables us to locate the transition region easily. 相似文献
112.
Lactols, which are insoluble or only sparingly soluble in most of the organic solvents that are generally employed for oxidation, are converted to lactones using o-iodoxybenzoic acid (IBX) in a facile manner under modified experimental conditions [EtOAc-DMSO (9:1) mixture at reflux] in good to excellent isolated yields (66-91%). 相似文献
113.
Naik GH Priyadarsini KI Maity DK Mohan H 《The journal of physical chemistry. A》2005,109(10):2062-2068
Reaction of one-electron oxidant (Br(2)(*-)) with tryptophol (TP) and 5-hydroxytryptophol (HTP) have been studied in aqueous solution in the pH range from 3 to 10, employing nanosecond pulse radiolysis technique and the transients detected by kinetic spectrophotometry. One-electron oxidation of TP has produced an indolyl radical that absorbs in the 300-600 nm region with radical pK(a) = 4.9 +/- 0.2, while the reaction with HTP has produced an indoloxyl radical with lambda(max) at 420 nm and radical pK(a) < 3. Hydroxyl radicals ((*)OH) react with these two compounds producing (*)OH radical adducts that undergo water elimination to give one-electron-oxidized indolyl and indoloxyl radical species, respectively. The indoloxyl radicals react with the parent compound to form dimer radicals with an average association constant of (6.7 +/- 0.4) x 10(4) M(-1). No such dimerization is observed with indolyl radical, indicating that the presence of the 5-hydroxy group markedly alters its ability to form a dimer. A possible explanation behind such a difference in reactivity has been supported with ab initio quantum chemical calculations. 相似文献
114.
A radiometric procedure for quantitative analysis of traces of silver in galena has been demonstrated. The mineral sample was dissolved in HNO3 (31) and silver present in the solution was precipitated as insoluble AgI by adding an excess amount of131I-labeled KI solution and was coprecipitated with zirconium hydrogen phosphate, Zr(HPO4)2, in 0.5N H2SO4 medium. The method of radiometric analysis of silver which was estimated from the knowledge of the loss of131I activity in solution, was found to be effective in determination of the element even below ppb level. Applicability of the radiometric procedure in routine analysis or preconcentration of traces of silver in galena has been stressed. 相似文献
115.
Polymerization of MMA was carried out in near-bulk and in fairly dilute solutions in DMF at 40° with (1) CPB-BZ2O2 combination as the redox initiator in the dark and (2) CPB as the sole photoinitiator in visible light. Rp was proportional to ([CPB] [BZ2O2])0.18 for the redox polymerization and to [CPB]0.35 for the photopolymerization both in near-bulk (10% DMF, v/v) and in high dilution (50% DMF, v/v). Polymerization was inhibited by hydroquinone in each case indicating a radical mechanism. Effect of several solvents/additives on the polymerization revealed that dimethyl formamide, acetonitrile and pyridine acted as rate enhancing solvents in the redox polymerization while in the photopolymerization they acted as normal diluents; benzene, methanol, acetone and chloroform exhibited inert nature while formamide and acetamide behaved as retarding additives in both types of polymerization. Initiator transfer of the degradative type reasonably explains kinetic nonidealities. 相似文献
116.
Nirmal Maity Amit Mandal Kaustuv Roy Arun K. Nandi 《Journal of Polymer Science.Polymer Physics》2019,57(4):189-201
Polymer‐based nanocomposites with good dielectric behavior have engrossed research devotion because of their distinctive benefits in electronic applications. An in situ synthetic process for the polybenzimidazole functionalized graphene oxide (GBI) and its nanocomposite with poly(vinylidene fluoride) (PVDF) is described. GBI shows good dispersion in the bulk PVDF matrix implying a strong interaction of polybenzimidazole with PVDF as evident from morphological and FTIR studies. A gradual increment of GBI in PVDF increases its piezoelectric β‐polymorph formation with a maximum of 73% for 10 wt % GBI in PVDF (GBF10) which also exhibits highest thermal stability. An exhaustive study of frequency dependent electrical properties of GBF10 indicates significantly higher dielectric constant (61), low dielectric loss (0.42), and low AC conductivity value of 1.17 × 10?10 S/cm at 100 Hz which are the key properties of a suitable capacitor. GBF10 also shows hydrophobic behavior (water uptake 2.89%) and low swelling ratio (1.143), providing an opportunity to use the composite film in fuel cell application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 189–201 相似文献
117.
118.
Santu Maity Dr. Krishnendu Aich Chandraday Prodhan Prof. Keya Chaudhuri Dr. Ajoy Kumar Pramanik Prof. Siddhartha Das Dr. Jhuma Ganguly 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(18):4856-4863
In the present study, the carbazole and 2,3,3-triphenylacrylonitrile (TPAN) nanostructures (2-CTPAN and 2,2′-CTPAN) have been designed and synthesized by Pd-catalyzed Sonogashira cross-coupling reaction. CTPAN exhibit aggregation-induced emission enhancement (AIEE) behavior in water with high fluorescence quantum yield. Both the compounds show tunable self-assembly in water as well as in N,N-dimethylformamide (DMF) by extended π–π stacking interactions. CTPAN can be self-assembled into spherical particles in water and the structures of these self-assemblies have been investigated using X-ray diffraction. Interestingly, 2-CTPAN and 2,2′-CTPAN form organogels with a critical gelation concentration (CGC) of 11 and 15 mg mL−1, respectively, in DMF and exhibit acicular and rod shaped morphology, respectively. The single-crystal structure of 2-CTPAN shows that the intermolecular C−H⋅⋅⋅π interactions lock the molecular conformation into a staircase-shaped supramolecular assembly. These AIEE active compounds reveal high water dispersibility, strong yellow fluorescence with high quantum yield, promising photostability and excellent biocompatibility, which make them potential bioimaging agents. 相似文献
119.
Dr. Kartik Maity Karabi Nath Dr. Michael A. Sinnwell Dr. Radha Kishan Motkuri Dr. Praveen K. Thallapally Prof. Kumar Biradha 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(64):14500-14505
The deliberate construction of isoreticular eea-metal–organic frameworks (MOFs) ( Cu-eea-1 , Cu-eea-2 and Cu-eea-3 ) and rtl-MOFs ( Co-rtl-1 and Co-rtl-2 ) has been accomplished based on the ligand-to-axial pillaring of supermolecular building layers. The use of different metal ions resulted in two types of supermolecular building layers (SBLs): Kagome (kgm) and square lattices (sql) which further interconnect to form anticipated 3D-MOFs. The isoreticular expansion of (3,6)-connected Cu-MOFs has been achieved with desired eea-topology based on kgm building layers. In addition, two (3,6)-connected Co-rtl-MOFs were also successfully constructed based on sql building layers. The Cu-eea-MOFs were shown to act as hydrogen storage materials with appreciable amount of hydrogen uptake abilities. Moreover Cu-eea-MOFs have also exhibited remarkable CO2 capture ability at ambient condition compared to nitrogen and methane, due to the presence of amide functionalities. 相似文献
120.
Cheng-Zong Kuo Li-Yun Hsu Yu-Shan Chen Dr. Kenta Goto Dr. Subhendu Maity Dr. Yi-Hung Liu Prof. Shie-Ming Peng Dr. Kien Voon Kong Prof. Teruo Shinmyozu Prof. Jye-Shane Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11511-11521
Anthracene–pentiptycene hybrid systems 1-Cn , where n refers to the number of carbon atoms in the linear alkyl chain, crystallize in three different polymorphs, denoted Y (yellow), G (green), and B (blue) forms in terms of the fluorescence color. While all Y-form crystals show the same yellow-to-blue fluorescence color response to the photomechanical stress generated by the anthracene [4+4] photodimerization reaction, the four G forms exhibit distinct photomechanofluorochromism (PMFC): from green to blue for G-1-C4 , to orange for G-1-C7 , to red for G-1-C8 , and to red then blue for G-1-C9 , and the B forms show no photochromic activity. The intriguing RGB three-color PMFC and abnormal topochemical reactivity of G-1-C9 are attributed to inherent softness of the crystal lattice. 相似文献