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1.
《Thermochimica Acta》2004,411(1):53-60
The aim of this work was to understand the crystallization process of terfenadine in solution.Cooling of saturated solutions prepared at 50 °C at different temperatures, evaporating the solvent from nearly saturated solutions at a certain temperature, and exposing ethanol solutions of terfenadine to water vapour atmosphere were the techniques used for obtaining terfenadine specimens. The characterization of these specimens was carried out by thermal microscopy, differential thermal analysis, thermogravimetry and powder X-ray diffraction. Crystalline phases, amorphous solids, and solvates were identified. For the solvents used in the present study, the crystallinity degree of terfenadine decreases from ethanol-water to ethanol and from this to methanol. Decreasing the temperature promotes the formation of amorphous solid material; at low temperatures, methanol and ethanol solvates are also formed.Desolvation, following the terfenadine aggregation process in solution accounts for the different behaviour found for the solvents and for the effect of temperature on the structure. The role of the solvent as structure-mediator is explained on the grounds of the values previously published for the enthalpy of solution of terfenadine in the solvents under study. 相似文献
2.
Two insect colonies of Elasmopalpus lignosellus were reared in our laboratory, the first being initiated from pupae obtained from a cornfield in the region of Sete Lagoas, Minas Gerais and the second from a cornfield in the region of Goiania, Goiás. From the two colonies, two extracts were prepared from the pheromone glands of virgin E. lignosellus females. The extract obtained from the first colony was designated as extract 1 while the extract obtained from the second colony was designated as extract 2. Extract 1 was analyzed by gas chromatography-mass spectrometry (GC-MS) with (Z)-9-hexadecenyl acetate [(Z)-9-HDA] and (Z)-11-hexadecenyl acetate [(Z)-11-HDA] being identified and confirmed by the formation of DMDS derivatives. In addition, a third acetate, which could be either (E)-8-hexadecenyl acetate [(E)-8-HDA] or (E)-9-hexadecenyl acetate [(E)-9-HDA] was detected by GC-MS. Extract 2 was analyzed by gas chromatography (GC) and gas chromatography-electroannetography (GC-EAD) revealing the presence of (Z)-11-HDA and (Z)-9-TDA. In addition, the same compounds elicited a response with the E. lignosellus male antenna obtained from the second insect colony. Electroantennography (EAG) screening with the male E. lignosellus antenna (obtained from the second insect colony) was conducted with the 23 possible tetradecenyl acetates (TDA) and 22 hexadecenyl acetates (HDA) as standards. Out of the 23 TDA isomers evaluated, only (Z)-9-TDA elicited a response and out of the 22 HDA [(Z) and (E) isomers gamma2 to delta13] evaluated only (Z)-11-HDA elicited a response. The acetate compositions of two extracts obtained from insects originating from the two states (Minas Gerais and Goiás) of Brazil were different from one another as well as from that obtained from insects in Tifton, GA, USA. The bioactivity data (GC-EAD) of the extract 2 differed from those reported for the Tifton, GA, USA population. These data suggest polymorphism in relation to the insect populations found in Brazil and in the USA. The possibility of the existence of an E. lignosellus sub-species cannot be ruled out. 相似文献
3.
A new polymorph of the iminophosphorane Ph2P(CH2Py)(NSiMe3), ( 1 ), is compared to a just recently published. The reaction of the starting material, the phosphane Ph2P(CH2Py) with N3SiMe3 in the presence of water gives [Ph2P(CH2Py)(NH2)][N3], ( 2 ). A comparison of the structural and NMR parameters of 2 with previously reported derivatives of 1 , suggests that 2 is best described as a phosphonium salt in which the negatively charged imino nitrogen atom is protonated, according to [Ph2(CH2Py)P+—NH2][N3]—, rather than as an iminiumphosphane salt [Ph2(CH2Py)P=+NH2][N3]—. 相似文献
4.
Matthias Weil 《Journal of solid state chemistry》2003,172(1):35-44
Mercury(I) selenite(IV) is polymorphic and crystallizes at least in three modifications, named α-, β-and γ-Hg2SeO3. Polycrystalline β-Hg2SeO3 was prepared by precipitation of a concentrated mercurous nitrate solution with selenous acid. Hydrothermal treatment of the colorless β-Hg2SeO3 powder in demineralized water at 250°C (10 days) yields light-yellow single crystals of α-Hg2SeO3 which show the highest density of the three modifications. Colorless needle-shaped single crystals of β-Hg2SeO3 and very few single crystals of γ-Hg2SeO3 co-crystallize from strongly diluted Hg2(NO3)2 and H2SeO3 solutions and were grown by a diffusion technique. All crystal structures were solved and refined from single crystal diffractometer data sets and are based on Hg22+ dumbbells and trigonal pyramidal SeO32− anions as the main building units. A common structural feature of all modifications is the formation of open channels extending parallel to the shortest crystallographic axis. The non-bonding orbitals of the SeIV atoms are stereochemically active and protrude into the channels. Upon heating in an open system under N2 atmosphere, both α- and β-Hg2SeO3 decompose in a well-separated three-step mechanism. The first step (T > 250°C) involves disproportionation into elementary mercury and α-HgSeO3 which at ca. 400°C subsequently transforms into β-HgSeO3. The second step between T = 400 and 500°C is accompanied by a loss of Hg and SeO2 and the formation of the basic salt Hg3SeO6. In the third step, at temperatures between T = 500° and 600°C, this material decomposes completely. Upon heating in a closed system (sealed silica capillaries), β-Hg2SeO3 transforms between 320-340°C into the more dense α-Hg2SeO3 which on further heating likewise converts into elementary mercury and β-HgSeO3. 相似文献
5.
A method to analyze human plasma proteins without fractionation, directly applying a plasma-matrix mixture on the target plate of a matrix-assisted laser desorption/ionization-time of flight-mass spectrometer (MALDI-TOF-MS), has been described. Peaks of ionized plasma proteins could not be detected applying a mixture of an undiluted plasma sample and a matrix solution, but they appeared when the plasma was diluted before mixing with the matrix. Tenfold diluted plasma provided well-resolved protein peaks in the m/z range from 4000 to 30,000. The addition of a simple post-crystallization washing procedure performed on the target plate further improved the quality of mass spectra. We numbered 58 peaks in the range of 4-160 kDa and 32 out of which were assigned to the plasma protein species which have been reported. Especially high sensitivity and resolution were obtained in the region < 30 kDa, where multiple isoforms of apolipoprotein A-I, apolipoprotein A-II, apolipoprotein C-I, apolipoprotein C-II, apolipoprotein C-III, and transthyretin could be assigned. Various post-translational modifications are involved in the isoforms, e.g., proteolytic cleavage, glycosylation and chemical modifications. This method will become complementary with the present electrophoretic techniques, especially for the analysis of low-molecular-mass proteins. 相似文献
6.
The thermal properties of two polymorphs of the drug carbamazepine, Forms I and III, were studied using high-speed differential scanning calorimetry (DSC). Previously, accurate determination of the heat enthalpy of fusion of Form III has not been possible using DSC at typical heating rates, due to concurrent exothermic recrystallisation to the higher-melting Form I. Here, it is demonstrated that heating rates of 250° C/min altered the kinetics of the melting transition of Form III such that this concurrent exothermic recrystallisation was inhibited. This allowed direct measurement of the enthalpy of the melting endotherm for Form III from a single transition. The enthalpy of this transition was found to be 109.5 J/g. Further investigations were then performed to test the utility of this technique in quantifying relative amounts of Forms I and III in mixtures of the two polymorphs. It was demonstrated that a limit of detection of 1% (w/w) was possible in this system. However, accurate quantification was not possible due to seeding effects initiating recrystallisation to Form I in these mixtures, even at these elevated heating rates. The utility of this novel technique as a fast analytical tool for studying the polymorphic behaviour of metastable polymorphs has been successfully demonstrated. 相似文献
7.
Samples in the system Lu2−xYxSi2O7 (0?x?2) have been synthesized following the sol-gel method and calcined to 1300 °C, a temperature at which the β-polymorph is known to be the stable phase for the end-members Lu2Si2O7 and Y2Si2O7. The XRD patterns of all the compositions studied are compatible with the structure of the β-polymorph. Unit cell parameters are calculated as a function of composition from XRD patterns. They show a linear change with increasing Y content, which indicates a solid solubility of β-Y2Si2O7 in β-Lu2Si2O7 at 1300 °C. 29Si MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the 29Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict 29Si chemical shifts in silicates is applied here to obtain the theoretical variation in 29Si chemical shift values in the system Lu2Si2O7-Y2Si2O7 and the results compare favorably with the values obtained experimentally. 相似文献
8.
From solutions of chromium(III) perchlorate and periodic acid, single crystals of γ‐HIO3 were obtained and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy and thermal analysis. The compound crystallizes in the orthorhombic crystal system, space group Pbca (a = 563.92, b = 611.10, c = 1507.16 pm). The structure is built up by dimers (HIO3)2, which are formed by hydrogen bonds. The crystals are metastable and transform into the stable modification, α‐HIO3, within a couple of weeks. 相似文献
9.
The crystal and molecular structures of three sydnone derivatives are reported. The compound 3-cyclohexylsydnone crystallizes in space group C2/c of the monoclinic system with sixteen molecules in a cell of dimensions a = 19.326 (3), b = 9.471 (2), c = 20.005 (4)Å, β = 106.85(1)°. The structure has been refined to a final value of 0.0581 for the conventional R-factor based on 2222 independent observed intensities. Form I of 3-(3-pyridyl)sydnone crystallizes in space group P2/n of the monoclinic system with eight molecules in a cell of dimensions a = 7.317(2), b = 9.283 (2), c = 20.891 (6) Å, β = 99.61(2)°. The structure has been refined to a final value of 0.0514 for the conventional R-factor based on 1208 independent observed intensities. Form II of 3-(3-pyridyl)sydnone crystallizes in space group P21/c of the monoclinic system with eight molecules in a cell of dimensions a=9.073 (2), b = 22.267 (5). c = 7.494(2)Å, β = 112.15 (2)°. The structure has been refined to a final value of 0.0462 for the conventional R-factor based on 1330 independent observed intensities. Each of the three structures contains two crystallographically independent molecules in the cell. In the case of 3-cyclohexylsydnone, one of the independent molecules exhibits disorder around the exocyclic bond at N(3). A comparison of bond lengths indicates that the (electron donating) cyclohexyl group brings about enhanced electron density in the N(3)-C(4) bond, and possibly in the N(3)-N(2) bond. All three structures studied here exhibit intermolecular hydrogen bonding involving C(4)-H(4)…O(6) interactions. Although there are no stacking interactions in the cyclohexyl derivative, there is evidence for such interactions in the 3-pyridyl derivatives. 相似文献
10.
目的 探讨钙蛋白酶-10 基因(CAPN-10)单核苷酸多态性-19(SNP-19)与多囊卵巢综合征(PCOS)的相关性。
方法 采用聚合酶链反应- 限制性片段长度多态性(PCR-RFLP)技术,对107 例PCOS患者(PCOS 组)及111 例健康体检者(对照组)的CAPN-10 SNP-19 进行分析,并测定其性激素和生化指标。PCOS组再根据BMI与胰岛素抵抗(IR)稳态模型指数(HOMA-IR)分为肥胖组与非肥胖组、IR 组与非IR 组,分析CAPN-10 SNP-19 与其关系。结果 与对照组相比,PCOS 组BMI、空腹血糖(FPG)、TG、TC、LDL、黄体生成素(LH)、黄体生成素/ 卵泡刺激素(LH/FSH)、睾酮(T)均升高(均P<0.01)。PCOS 组CAPN-10 SNP-19 1等位基因及1/2基因型频率均高于对照组(均P<0.05);且CAPN-10 SNP-19 1/2基因型PCOS 发病风险较1/1、2/2 基因型增加约2倍(OR=1.9,95%CI=1.1~3.3,P<0.05)。CAPN-10 SNP-19 1、2等位基因频率PCOS 肥胖组与非肥胖组、IR 组与非IR组比较均无统
计学差异(均P>0.05);PCOS 肥胖组和IR组CAPN-10 SNP-19 1/2基因型频率分别高于非肥胖组和非IR 组,但差异均无统计学意义(均P>0.05)。结论 CAPN-10 SNP-19 与PCOS 遗传易感性有关,可能与PCOS 肥胖及IR 无关。 相似文献