全文获取类型
收费全文 | 611篇 |
免费 | 12篇 |
国内免费 | 61篇 |
专业分类
化学 | 643篇 |
晶体学 | 15篇 |
综合类 | 2篇 |
物理学 | 24篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 25篇 |
2013年 | 74篇 |
2012年 | 50篇 |
2011年 | 29篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 54篇 |
2007年 | 53篇 |
2006年 | 37篇 |
2005年 | 52篇 |
2004年 | 27篇 |
2003年 | 26篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有684条查询结果,搜索用时 15 毫秒
1.
Henry Insuasty Braulio Insuasty Edison Castro Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(9):908-911
In the title compound, C15H12N4OS2, the bond distances in the fused heterocyclic system show evidence for aromatic‐type delocalization in the pyrazole ring with some bond fixation in the triazine ring. The thiophenyl substituent is slightly disordered over two sets of atomic sites having occupancies of 0.934 (4) and 0.066 (4). The non‐H atoms in the entire molecule are nearly coplanar, with the planes of the furanyl substituent and the major orientation of the thiophenyl substituent making dihedral angles of 5.72 (17) and 1.8 (3)°, respectively, with that of the fused ring system. Molecules are linked into centrosymmetric R22(10) dimers by C—H...O hydrogen bonds and these dimers are further linked into chains by a single π–π stacking interaction. Comparisons are made with some related 4,7‐diaryl‐2‐(ethylsulfanyl)pyrazolo[1,5‐a][1,3,5]triazines which contain variously substituted aryl groups in place of the furanyl and thiophenyl substituents in the title compound. 相似文献
2.
Saskia Menzel Konstantinos D. Demadis Christoph Janiak 《Phosphorus, sulfur, and silicon and the related elements》2020,195(10):830-835
AbstractThe fully deprotonated anion of 1,3,5-benzene-triphosphonic acid 1,3,5-C6H3[PO32?]3 gives rise to deceptively simple 1H and 31P NMR spectra due to a corresponding [AX]3 spin system. The 13C{1H} NMR spectrum reveals two 13C isotopomers which are identified via AXX′2 systems. Results from analysis and iteration are described. 相似文献
3.
Emmanuel Blas Patricio-Rangel Margarita Tlahuextl Hugo Tlahuext Antonio Rafael Tapia-Benavides 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(4):322-327
The synthesis and characterization of two new 1,3,5‐triazines containing 2‐(aminomethyl)‐1H‐benzimidazole hydrochloride as a substituent are reported, namely, 2‐{[(4,6‐dichloro‐1,3,5‐triazin‐2‐yl)amino]methyl}‐1H‐benzimidazol‐3‐ium chloride, C11H9Cl2N6+·Cl? ( 1 ), and bis(2,2′‐{[(6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(azanediyl)]bis(methylene)}bis(1H‐benzimidazol‐3‐ium)) tetrachloride heptahydrate, 2C19H18ClN92+·4Cl?·7H2O ( 2 ). Both salts were characterized using single‐crystal X‐ray diffraction analysis and IR spectroscopy. Moreover, the NMR (1H and 13C) spectra of 1 were obtained. Salts 1 and 2 have triclinic symmetry (space group P) and their supramolecular structures are stabilized by hydrogen bonding and offset π–π interactions. In hydrated salt 2 , the noncovalent interactions yield pseudo‐nanotubes filled with chloride anions and water molecules, which were modelled in the refinement with substitutional and positional disorder. 相似文献
4.
A rapid and efficient method for preparation of C2-symmetrical 1,3,5-triazine polycarboxylate ligands was developed. The reactions included either selective mono- or di-substitution of 2,4,6-trichloro-1,3,5-triazine with various nucleophiles containing carboxyl group(s), followed by nucleophilic displacement of the remained chloride(s) in aqueous media under microwave irradiation. Novel C2-symmetrical tripodal ligands were afforded in good yields and purities under short reaction time with simple work-up, which are potentially useful as structural directing units in metal-organic frameworks. 相似文献
5.
《中国化学会会志》2018,65(5):554-560
Some less hindered 2,4,6‐tri‐aryloxy‐s‐triazines were synthesized through the reaction of the corresponding phenols as a starting materials with cyanogen bromide (BrCN) to obtain the corresponding arylcyanates and then trimerized. Unexpectedly, 2,4‐di‐tert‐butyl‐1‐cyanatobenzene derived from 2,4‐di‐tert‐butylphenol did not trimerize but, indeed, yielded bis(2,4‐di‐tert‐butylphenyl) carbonate. The structures of 2,4,6‐tri‐aryloxy‐s‐triazines and bis(2,4‐di‐tert‐butylphenyl) carbonate were characterized by means of IR, 1H, and 13C NMR spectroscopies. Also the structure of the latter compound was studied by X‐ray crystallography. 相似文献
6.
Novel core-shell molecularly imprinted polymers were prepared based on zinc oxide quantum dots for the determination of 2,4,6-trichlorophenol by fluorescence. Principally, ZnO quantum dots and 2,4,6-trichlorophenol were chosen as the core substrate and the template molecule, respectively. The specific recognition sites for 2,4,6-trichlorophenol were obtained during the polymerization process in presence of 3-aminopropyltriethoxysilane and tetraethylorthosilicate. Molecularly imprinted ZnO quantum dots were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy and the optical properties were evaluated by spectrofluorometry. Under the optimal conditions, molecularly imprinted ZnO quantum dots were successfully applied to the sensitive determination and selective recognition of 2,4,6-trichlorophenol in water. A linear relationship was obtained to cover the concentration range of 0–160?µmol?L?1 with a correlation coefficient of 0.9931 calculated by the Stern–Volmer equation. The products were used for the determination of 2,4,6-trichlorophenol in the water from local rural areas and the results strongly supported that the molecularly imprinted ZnO quantum dots were suitable for the determination of 2,4,6-trichlorophenol in real examples. 相似文献
7.
《应用有机金属化学》2018,32(5)
Hierarchical IRMOF‐3 nanosheets were firstly fabricated by a simple reflux strategy and were then characterized through Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and X‐ray photoelectron spectroscopy. They revealed a high fluorescence quantum yield (13.2%) and showed excellent selectivity and sensitivity for 2,4,6‐trinitrophenol (TNP) over a concentration range of 1–29 μM in aqueous solution. This work demonstrates that the facile fabrication method for hierarchical IRMOF‐3 nanosheets with favorable selectivity and sensitivity for TNP could produce a new point of view on novel metal–organic framework nanomaterials for on‐line detection of organic pollutants in water. 相似文献
8.
Chong Wu Jiang-Lin Zhao Xue-Kai Jiang Xin-Long Ni Xi Zeng Carl Redshaw Takehiko Yamato 《Analytica chimica acta》2016
A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV–vis and fluorescence spectroscopy studies. 1H NMR titration analysis verified that CH?O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer. 相似文献
9.
设计并制备了用于检测2,4,6-三氯苯酚的荧光分子印迹。由于铕配合物对模板分子的荧光淬灭作用,可用于荧光检测工具。荧光分子印迹在模板分子浓度范围0~70 nmol·L~(-1)内具有良好的荧光线性响应,相关系数为0.996 28。荧光分子印迹展现出了良好的灵敏度,其最低检出限为3.12 nmol·L~(-1)。荧光分子印迹具有较好的热稳定性,同时选择性检测实验证明荧光分子印迹对2,4,6-三氯苯酚具有良好的特异选择性。实验结果说明荧光分子印迹可用于选择性荧光检测低浓度氯酚类物质。 相似文献
10.
Mara Mirasoli Angela Buragina Luisa Stella Dolci Massimo Guardigli Patrizia Simoni Angel Montoya Elisabetta Maiolini Stefano Girotti Aldo Roda 《Analytica chimica acta》2012
Simple, rapid and highly sensitive assays, possibly allowing on-site analysis, are required in the security and forensic fields or to obtain early signs of environmental pollution. Several bioanalytical methods and biosensors based on portable devices have been developed for this purpose. Among them, Lateral Flow ImmunoAssays (LFIAs) offer the advantages of rapidity and ease of use and, thanks to the high specificity of antigen–antibody binding, allow greatly simplifying and reducing sample pre-analytical treatments. However, LFIAs usually employ colloidal gold or latex beads as labels and they rely on the formation of colored bands visible by the naked eye. With this assay format, only qualitative or semi-quantitative information can be obtained and low sensitivity is achieved. Recently, the use of enzyme-catalyzed chemiluminescence detection in LFIA has been proposed to overcome these problems. In this work, we describe the development of a quantitative CL-LFIA assay for the detection of 2,4,6-trinitrotoluene (TNT) in real samples. Thanks to the use of a portable imaging device for CL signal measurement based on a thermoelectrically cooled CCD camera, the analysis could be performed directly on-field. A limit of detection of 0.2 μg mL−1 TNT was obtained, which is five times lower than that obtained with a previously described colloidal gold-based LFIA developed employing the same immunoreagents. The dynamic range of the assay extended up to 5 μg mL−1 TNT and recoveries ranging from 97% to 111% were obtained in the analysis of real samples (post blast residues obtained from controlled explosion). 相似文献