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991.
Diosmetin, 3',5,7-trihydroxy-4'-methoxy flavone, is the aglycone of the flavonoid glycoside diosmin that occurs naturally in foods of plant origin. Diosmin exhibits antioxidant and anti-inflammatory activities, improves venous tone and it is used for the treatment of chronic venous insufficiency. Diosmin is hydrolyzed by enzymes of intestinal micro flora before absorption of its aglycone diosmetin. A specific, sensitive, precise, accurate and robust HPLC assay for the determination of diosmetin in human plasma was developed and validated. Diosmetin and the internal standard 7-ethoxycoumarin were isolated from plasma by liquid-liquid extraction and separated on a C8 reversed-phase column with methanol-water-acetic acid (55:43:2, v/v/v) as the mobile phase at 43 degrees C. Peaks were monitored at 344 nm. The method was linear in the 10-300 ng/mL concentration range (r > 0.999). Recovery for diosmetin and internal standard was greater than 89.7 and 86.8%, respectively. Intra-day and inter-day precision for diosmetin ranged from 1.6 to 4.6 and from 2.2 to 5.3%, respectively, and accuracy was better than 97.9%. 相似文献
992.
Makarova EA Fukuda T Luk Yanets EA Kobayashi N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(4):1235-1250
1,2-Naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2-naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), and the structure of each isomer was determined by (1)H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q-band splits into two intense components similarly to the 2,3-naphthalene-fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene-fused derivatives rather than the 2,3-naphthalene-fused derivatives. Molecular-orbital and configuration-interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations. 相似文献
993.
Summary. A series of 6- and 7-substituted derivatives of 1,3-diaminoisoquinoline were synthesized by the reaction of N,N-diethylarylacetamides with POCl3 and then with N,N-dimethylcyanamide. The products were identified by means of spectroscopic methods and their pK
a
dissociation constants were determined.
Corresponding author. E-mail: kudelkoa@zeus.polsl.gliwice.pl
Received July 7, 2002; accepted July 22, 2002 相似文献
994.
995.
Cure Degree Estimation of Photocurable Coatings by DSC and Differential Photocalorimetry 总被引:1,自引:0,他引:1
Ruiz C. S. B. Machado L. D. B. Vanin J. A. Volponi J. E. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):335-341
Radiation-curable coatings have acquired importance, because they are environmentally-friendly (no solvent emission)and require
low energy for curing, when compared to other conventional heat-curable products. UV-curable coatings performance depends
on the cure quality. Suitable methods were evaluated to estimate the degree of cure applying quantitative techniques, such
as differential scanning calorimetry (DSC) and differential photocalorimetry (DPC), in order to determine the residual heat
of curing in UV-cured films. The results of the DPC technique showed better sensibility than DSC technique, although the use
of suitable pans for the case of clear coats must be considered.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
Fukuda T Makarova EA Luk'yanets EA Kobayashi N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(1):117-133
Benzene- or 2,3-naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized by using tetramethylsuccinonitrile as a source of hydrogenated sites. The derived compounds were characterized by using NMR spectroscopy, X-ray crystallography, electronic and magnetic circular dichroism (MCD) spectroscopy, and electrochemical and spectroelectrochemical methods. X-ray analysis revealed that the benzene-fused TAiBC deviates slightly from planarity at the hydrogenated sites as a result of the presence of sp(3) carbons, which prefer a nonplanar tetrahedral conformation. The spectral data were analyzed by using a band deconvolution technique. In the electronic absorption spectra of TAC and TABC species, the Q band splits into two intense components and smaller splittings were observed for the 2,3-naphthalene-fused derivatives relative to the benzo-fused species. In contrast, in the case of TAiBCs, the Q band splitting was apparently not observed in absorption spectra, as expected from the C(2v) molecular symmetry. However, MCD signals of the Q band in TAiBCs showed Faraday B terms, implying that the accidental degeneracy of the LUMO and LUMO+1 was broken even for adjacently ring-fused species. Relative molecular orbital energies were estimated by using cyclic and differential pulse voltammetry. The first reduction potentials were close for TACs and TABCs, although those of TAiBCs shifted to more negative potentials. In contrast, although TABCs and TAiBCs exhibited similar first oxidation potentials, those of TACs appeared at more positive potentials. These properties were reproduced and rationalized by molecular orbital and configuration interaction calculations within the framework of the ZINDO/S Hamiltonian. DFT-level frequency calculations have succeeded in reproducing the IR spectra for low-symmetry tetraazaporphyrin (TAP) derivatives for the first time. The relationship between structures and spectral features is discussed. 相似文献
997.
荧光分光光度计的功能开发 总被引:2,自引:0,他引:2
固、液体吸收光谱测量的附件是由光阑、负透镜、全反射棱镜,吸收不也组成的光学系统,将它配置到进口荧光分光光度计上,可以扩展其功能,使其具有紫外分光光度计(UV)的功能,能够测量固体、液体样品的透射光谱和吸收光谱。 相似文献
998.
999.
Céline Chizallet Guylène Costentin Jean-Marc Krafft Hélène Lauron-Pernot Michel Che 《Chemphyschem》2006,7(4):904-911
Photoluminescence decay studies of emitting species on MgO nanocubes at room temperature provide evidence of three surface species characterized by an excitation and emission wavelength couple {lambda(exc);lambda(em)}. Species A corresponds to {lambda(exc)=240 nm; lambda(em)=380 nm}, whereas the couple {lambda(exc)=280 nm; lambda(em)=470 nm} is assigned to two species: B and B', the former is involved in energy transfer from excited state A* and the latter in direct emission from excited state B'*. A simple model for energy transfer from species A* to B is proposed. The numerical resolution of equations corresponding to this model is in good agreement with experimental data. This method quantifies the kinetics of intrinsic emission and energy transfer processes. Lifetime values indicate that phosphorescence is taking place, and species A, B and B' are identified as edge O(2-) (4 C), corner O(2-) (3 C) and kink O(2-) (3 C) oxide ions respectively. 相似文献
1000.
I. L. Eremenko M. A. Golubnichaya S. E. Nefedov A. A. Sidorov I. F. Golovaneva V. I. Burkov O. G. Ellert V. M. Novotortsev L. T. Ermenko A. Sousa M. R. Bermejo 《Russian Chemical Bulletin》1998,47(4):704-718
The reaction of NiCl2·6H2O with Me3CCOOH and KOH taken in a molar ratio of 1:2:2 in water afforded the nonanuclear antiferromagnetic complex Py2Ni2(Me3CCOOH)2(OOCCMe3)2(μ-OOCCMe3)2(μ-OH2), which apparently contains NiII and NiIII atoms. The complex was isolated by extraction with CH2Cl2, benzene, or hexane. The reactions of this complex with pyridine bases (pyridine (Py), 3,4-lutidine (Lut), and nicorandil
(Nic)) gave the adducts L4Ni2(OOCCMe3)2(μ-OOCCMe3)2(μ-OH) (L=Py, Lut, or Nic, respectively). According to magnetic measurements, intramolecular ferromagnetic exchange interactions
in these adducts are complemented by intermolecular antiferromagnetic interactions. Pyrolysis of the pyridine adduct in air
or under an inert atmosphere in xylene yielded the antiferromagnetic complex Py2Ni2(Me3CCOOH)2(OOCCMe3)2(μ-OOCCMe3)2(μ-OH2), which contains NiII atoms. The structures of all the complexes synthesized were established by X-ray diffraction analysis. The electronic absorption
spectra of these compounds are considered.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–738, April, 1998. 相似文献