全文获取类型
收费全文 | 377篇 |
免费 | 18篇 |
国内免费 | 99篇 |
专业分类
化学 | 462篇 |
晶体学 | 5篇 |
综合类 | 3篇 |
物理学 | 4篇 |
综合类 | 20篇 |
出版年
2023年 | 1篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 14篇 |
2019年 | 6篇 |
2018年 | 16篇 |
2017年 | 16篇 |
2016年 | 23篇 |
2015年 | 16篇 |
2014年 | 26篇 |
2013年 | 59篇 |
2012年 | 20篇 |
2011年 | 33篇 |
2010年 | 11篇 |
2009年 | 20篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 60篇 |
2001年 | 8篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有494条查询结果,搜索用时 512 毫秒
431.
The title compounds were synthesized and characterized by IR,1H-NMR,Mass and elementary analysis and single-crystal X-ray diffraction.In 1a,intermolecular C-H…π interactions produce a three-dimensional network.In 1b,intermolecular C-H…O hydrogen bonds generate an R22(22) ring.The hydrogen bonding is supported by C-H…π interactions. 相似文献
432.
利用Vilsmeier-Haak反应得到活性中间体,取代-4-甲酰基吡唑;将其与芳氧乙酰肼反应,合成5个吡唑腙类化合物3,再经关环反应,制得5个吡唑类双杂环化合物4。所有新化合物的结构均经IR,1H NMR,MS和元素分析确证了结构。对新化合物3,4分别进行了棉花枯萎病菌、棉花黄萎病菌、棉花立枯病菌、瓜果腐霉病菌、番茄早疫病菌、向日葵菌核病菌等初步的抑菌活性测试,结果表明,吡唑类双杂环化合物4的抑菌效果明显高于吡唑腙化合物3。在质量浓度为50mg/L时,3d、3e对番茄早疫病菌、向日葵菌核病菌有较好的抑制效果(﹥80%);双杂环化合物4对6种病菌均有明显的抑制效果(﹥70%),其中4d、4e对棉花立枯病菌的抑制率大于95%。 相似文献
433.
Milan D. Joksovi? Violeta Markovi? Tatjana Stanojkovi? Ivan S. Damljanovi? Nina Todorovi? Rastko D. Vuki?evi? 《Journal of organometallic chemistry》2009,694(24):3935-3713
A series of new N-[(3-ferrocenyl-1-phenylpyrazol-4-yl)methyl] α-amino acids were prepared and characterized by a range of spectroscopic techniques and cyclic voltammetry. The in vitro antitumor activity of all synthesized compounds was investigated against cervix adenocarcinoma HeLa, melanoma Fem-x and myelogenous leukemia K562 cell lines using the MTT method. Tryptophan derivative 1l exhibited the highest cytotoxic activity in the cell growth inhibition of all three types of cell lines. 相似文献
434.
The title compound 7-ethoxycarbonyl-2-methyl-6-methylthio-1H-imidazo[1,2-b]-pyrazole (Mr = 239.29) was synthesized and structurally characterized by IR, 1H NMR and single-crystal X-ray diffraction. It belongs to the triclinic system, space group P1, with a = 8.0461(10), b = 8.5534(11), c = 9.5605(12) A, α = 64.804(2), β = 74.231(2), γ = 76.885(2)°, V= 568.27(12) A3, Z = 2, Dc = 1.398 g/cm3,μ= 0.274 mm-1, F(000) = 252, the final R.= 0.0454 and wR = 0.1261. A total of 3360 reflections were collected, of which 2466 were independent (Rint = 0.0138) and 2154 were observed with I > 2σ(Ⅰ). 相似文献
435.
The title Schiff base compound (C11H8N4O), a derivative of pyrazole, has been synthesized by the reaction of salicylaldehyde and 3-amino-4-cyanopyrazole in absolute ethanol and characterized by elemental analyses, IR, ^1H NMR and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P21/n, with a = 7.5594(7), b = 18.3342(19), c = 22.461(2) A^°, β = 98.419(2)°, V = 3079.5(5) A^°3, Mr = 212.21, Z = 12, F(000) = 1320, Dc = 1.373 g/cm^3, T = 298(2) K, 2 = 0.71073 A^°, the final R = 0.0571 and wR = 0.0493. A total of 5412 unique reflections were collected, of which 1612 with I 〉 2σ(I) were observed. The molecular structure adopts a trans configuration about the C=N double bond. The preliminary biological tests show that the compound has high antibacterial activities. 相似文献
436.
设计并合成了5种呋喃并[3’,4’:5,6]吡啶并[2,3-c]吡唑受体分子, 利用紫外-可见吸收光谱考察了其与F-, Cl-, Br-, AcO-, 等阴离子的作用. 结果表明该类受体分子与阴离子形成氢键配合物, 导致呋喃并吡啶并吡唑受体的光谱发生变化. 测定了配合物的结合比和稳定常数, 发现受体化合物对F-, AcO-离子具有良好的选择性, 对其它多种阴离子无影响. Job曲线表明受体分子与阴离子间形成1∶1型的配合物. 相似文献
437.
Zhiqiang Shi Ningning Ji Rengao Zhao Zhifeng Li 《International journal of quantum chemistry》2012,112(2):373-381
The title compound, 3,5‐Dimethyl‐pyrazole‐1‐carbodithioic acid benzyl ester, has been synthesized and structurally characterized by X‐ray single crystal diffraction, elemental analysis, IR spectra, and UV‐Vis spectrum. The crystal belongs to orthorhombic, space group P212121, with a = 5.3829(15), b = 11.193(3), c = 21.824(6) Å, V = 1315.0(6) Å3, and Z = 4. The molecules are connected via intermolecular C–H···N hydrogen bonds into 1D infinite chains. The crystal structure is consolidated by the intramolecular C–H···S hydrogen bonds. Furthermore, Density functional theory (DFT) calculations of the structure, stabilities, orbital energies, composition characteristics of some frontier molecular orbitals and Mulliken charge distributions of the title compound were performed by means of Gaussian 03W package and taking B3LYP/6‐31G(d) basis set. The time‐dependent DFT (TD‐DFT) calculations have been employed to calculate the electronic spectrum of the title compound, and the UV‐Vis spectra has been discussed on this basis. The results show that DFT method at B3LYP/6‐31G(d) level can well reproduce the structure of the title compound. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 相似文献
438.
《Journal of Coordination Chemistry》2012,65(15):2574-2585
AbstractThe coordination chemistry of (diphenyl((5-phenyl-1H-pyrazol-3-yl)methyl) phosphine oxide), 1, was explored. Reacting appropriate equivalents of this ligand and either cobalt perchlorate or MoO2Cl2 results in formation of [Co((C6H5)2POCH2(C3N2H2)(C6H5))2(C4H8O)2][ClO4]2, 2, and MoO2Cl2((C6H5)2POCH2(C3N2H2)(C6H5))(THF), 3. Complexes were characterized by FTIR, NMR, TGA and elemental analyses. Single crystal X-ray spectroscopy reveals octahedral geometries for both compounds. Complex 2 consists of two trans THF ligands in axial positions and two (diphenyl((5-phenyl-1H-pyrazol-3-yl)methyl) phosphine oxide) ligands occupying equatorial positions resulting in an overall octahedral geometry. Two perchlorate counter anions complete the structure. The Co ion resides on an inversion point. THF contains disorder with the four carbon atoms and the major orientation refined to an occupancy of 86.1(9)%. Complex 3 consists of the cis-dioxo MoO2 unit bonded with axial trans-chloride ligands and 1 in the equatorial plane completing the disordered octahedral geometry. A THF ligand is hydrogen bonded to the H-atom on the nitrogen of the pyrazole moiety in ligand 1. DFT calculations based on geometries obtained crystallographically were useful in assigning FTIR peaks and the UV-vis spectra. 相似文献
439.
The title compound ethyl 1-(2-bromoethyl)-3-(4-methoxyphenyl)-1H-pyrazole-5-carboxylate 1 has been synthesized and structurally characterized by single-crystal X-ray diffraction.The crystal is of monoclinic(C15H17BrN2O3,Mr = 353.22),space group C21 with a = 24.691(7),b = 6.7678(17),c = 17.884(5) ,β = 97.184(5)o,V = 2965.1(13) 3,Z = 8,Dc = 1.583 g.cm-3,F(000) = 1440,μ = 2.784 mm-1,the final R = 0.0260 and wR = 0.0596 for 2684 observed reflections with I > 2σ(I).All the carbon atoms in the molecule are nearly coplanar except C(15),with a large conjugated system among the carbonyl group,pyrazole ring and the benzene ring.Three non-classical intermolecular hydrogen bonds help to stabilize the crystal lattice.The regioselectivity was rationalized based on the coordination of potassium ion with the N-anion and the carbonyl oxygen atom. 相似文献
440.