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991.
We apply time-dependent density functional theory to study the valence electron excitations of molecules and generalize the typically used time-propagation scheme and Casida's method to calculate the full wavevector dependent response function. This allows the computational study of dipole-forbidden valence electron transitions and the dispersion of spectral weight as a function of the wavevector. The method provides a novel analysis tool for spectroscopic methods such as inelastic x-ray scattering and electron energy loss spectroscopy. We present results for benzene and CF(3)Cl and make a comparison with experimental results. 相似文献
992.
Hans J. Breunig Prof. Dr. Enno Lork Ovidiu Moldovan Ciprian I. Raţ 《无机化学与普通化学杂志》2010,636(6):1090-1094
The iron complexes [(Et2Sb)4Fe4(CO)14] ( 1 ), [(nPr2Sb)4Fe3(CO)10] ( 2 ), [{(Me3SiCH2)2Sb}4Fe2(CO)6] ( 3 ), and [2‐(Me2NCH2)C6H4SbFe2(CO)8] ( 4 ) were prepared by reactions of distibanes with Fe2(CO)9. Compounds 1 – 4 were characterized by X‐ray diffraction, 1H NMR and IR spectroscopy as well as mass spectrometry; complex 1 was additionally characterized by density functional calculations. 相似文献
993.
Ildikó Kriston Gábor Pénzes Gábor Szijjártó Pál Szabó Enik? Földes Béla Pukánszky 《Polymer Degradation and Stability》2010,95(9):1883-1893
The processing stabilising performance of various phosphorous antioxidants in polyolefins is affected significantly by their chemical composition. In order to explore the mechanism of stabilisation, the reactions of a hindered aryl phosphite [tris(2,4-di-tert-butylphenyl)phosphite (DTBPP), Hostanox PAR 24] were investigated at temperatures corresponding to polyethylene processing. The thermal and thermo-oxidative stability of the additive was determined by differential scanning calorimetric (DSC) and thermogravimetric methods. DTBPP was heat treated under argon and oxygen at 200 and 240 °C. The stabiliser was reacted at 200 °C with azobisisobutyronitrile (AIBN) in oxygen-free environment (carbon centred radicals) and under oxygen (peroxy radicals), with dicumyl peroxide (DCP) in oxygen atmosphere (oxy radicals), and with cumene hydroperoxide (CHP) under argon. The reaction products were identified by FT-IR, HPLC and HPLC-MS. The results revealed that besides the known reactions of hindered aryl phosphites, thermal decomposition and recombination reactions also take place above the melting point of the antioxidant. DTBPP does not react with molecular oxygen, but its decomposition is accelerated by oxygen and especially by radicals. Accordingly, the heat-stability of phosphorous stabilisers also has to be taken into account in their application, as it is one of the factors which influence the processing stabilisation of polyolefins. 相似文献
994.
Raúl A. Gil José A. Salonia José A. Gásquez Alejandro C. Olivieri Roberto Olsina Luis D. Martinez 《Microchemical Journal》2010,95(2):306-310
A novel method for the determination of Pb by on-line cloud point extraction coupled to inductively coupled plasma optical emission spectrometry with ultrasonic nebulization (USN–ICP OES) is presented. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) and was retained in a minicolumn filled with particles of PTFE. Since the micelles of PONPE were able to extract Pb from the solutions, the use of a complexing reagent was not necessary. Afterwards, the surfactant-rich phase containing the analyte was removed from the minicolumn with nitric acid and introduced into the ultrasonic nebulizer. A total enhancement factor of 150 was obtained for a preconcentration time of 3.3 min, with respect to the direct determination of Pb by conventional ICP OES. The values of the detection (3σ) and quantification (10σ) limits for the preconcentration of 10 mL of sample solution were 0.09 µg L− 1 and 0.2 µg L− 1 respectively. The precision, expressed as the relative standard deviation (RSD), for 10 replicate determinations at 5.0 µg L− 1 Pb level was 6.0%. Verification of the accuracy was carried out by analysis of two certified reference materials (NIST SRM 1640e and VKI QC Metal LL1). The method was successfully applied to the determination of Pb in drinking water samples. 相似文献
995.
Tomá? Gucky Eva ?ezní?ková Petr D?ubák Marián Hajdúch Vladimír Kry?tof 《Monatshefte für Chemie / Chemical Monthly》2010,55(7):709-714
Abstract
The deregulation of cell cycle components in cancer cells has provided a rationale for the development of small molecule inhibitors of cyclin-dependent kinases as novel anticancer drugs. A series of 1,5-diaryl-3-(3,4,5-trihydroxyphenyl)-1H-pyrazolo[4,3-e][1,2,4]triazines was synthesized and their kinase inhibitory activity and cytotoxicity against several cancer cell lines has been evaluated. Some of the compounds of the series exhibited induction of caspase-dependent cell death and inhibition of cyclin-dependent kinase 2 (CDK2). 相似文献996.
Cu(II) and Zn(II) complexes were synthesized from equimolar amounts of carboxamides; 1,8-bis(2-thiophenecarboxamido)-p-menthane (tkdam) and 1,8-bis(2-furancarboxamido)-p-menthane (furdam). The structure of the carboxamides were determined by elemental analysis; 1H NMR, 13C NMR, FT-IR and LC-MS spectra. The relative energies and the electronic properties (LUMO, HOMO, LUMO-HOMO gap) of the ligands
were investigated theoretically by performing Semi-empirical molecular orbital theory PM3 method in Hyperchem 7 (Release).
Carboxamide complexes having general formula as; monomeric, [ML]Cl2 and dimeric [Cu(tkdam)Cl]2Cl2 · 5H2O were synthesized and characterized by using element analysis; FT-IR, LC-MS spectra; magnetic susceptibility, molar conductivity
and thermal (TGA/DTA curve) studies. It was found that the coordination number of the monomeric complexes is four whereas
dimeric’s is six. The changes in the selected vibration bands in FT-IR indicate that, carboxamides behave as tetradentate
ligands and coordinate to metal ions from acyl ring (through S/O) and amide carbonyl (C=O). Molar conductivity measurements
indicate the 1: 2 ionic nature of the carboxamide complexes. 相似文献
997.
Miró P Pierrefixe S Gicquel M Gil A Bo C 《Journal of the American Chemical Society》2010,132(50):17787-17794
Uranyl-peroxide nanoclusters display different topologies based on square, pentagonal and hexagonal building blocks. Computed complexation energies of different cations (Li(+), Na(+), K(+), Rb(+), and Cs(+)) with [UO(2)(O(2))(H(2)O)](n) (n = 4, 5, and 6) macrocycles suggest a strong cation templating effect. The inherent bent structure of a U-O(2)-U model dimer is demonstrated and justified through the analysis of its electronic structure, as well as of the inherent curvature of the four-, five-, and six-uranyl macrocyles. The curvature is enhaced by cation coordination, which is suggested to be the driving force for the self-assembly of the nanocapsules. 相似文献
998.
Mario Ribeiro de Melo-Júnior Jorge Luiz Silva Araújo-Filho Consuelo Antunes Barreto Lins Nicodemos Teles de Pontes-Filho Luiz Bezerra de CarvalhoJr 《Applied biochemistry and biotechnology》2010,160(8):2198-2207
This work aimed to immobilize the antibody anti-galectin-3 onto polysiloxane–polyvinyl alcohol (POS-PVA) support, to evaluate
its capacity to capture the serum antigen galectin-3 and to quantify by ELISA the antigen levels in sera from patients with
prostatic adenocarcinoma (PA) and benign prostatic hyperplasia (BPH) and healthy individuals. Also, for comparative effect,
the galectin-3 expression in the prostate tissue through immunohistochemistry was evaluated. The optical density (galectin-3
level) values established for the sera from PA and BPH patients were lower compared with those found for the healthy individuals.
Galectin-3 immunohistochemically showed a significant increase and reduction of the cytoplasmatic protein expression in BPH
and PA, respectively, compared with the normal prostate. These results showed that POS-PVA disks could be used as solid phase
to immobilize serum galectins and in immunoassays procedures for the correspondent IgG anti-galectins detection in human sera. 相似文献
999.
Paula Santos Nunes Marília Santos Bezerra L. P. Costa Juliana Cordeiro Cardoso R. L. C. AlbuquerqueJr. M. O. Rodrigues Gabriela Borin Barin Francilene Amaral da Silva A. A. S. Araújo 《Journal of Thermal Analysis and Calorimetry》2010,99(3):1011-1014
The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based
(UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning
electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer.
In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation)
did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative
that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy
(SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and
CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film. 相似文献
1000.
In recent years, Mitogen-Activated Protein Kinase (MAPK) pathways have emerged as major regulators of cellular physiology. In the fungal pathogen Candida albicans, three different MAPK pathways have been characterized in the last years. The HOG pathway is mainly a stress response pathway that is activated in response to osmotic and oxidative stress and also participates regulating other pathways. The SVG pathway (or mediated by the Cek1 MAPK) is involved in cell wall formation under vegetative and filamentous growth, while the Mkc1-mediated pathway is involved in cell wall integrity. Oxidative stress is one of the types of stress that every fungal cell has to face during colonization of the host, where the cell encounters both hypoxia niches (i.e. gut) and high concentrations of reactive oxygen species (upon challenge with immune cells). Two pathways have been shown to be activated in response to oxidative stress: the HOG pathway and the MKC1-mediated pathway while the third, the Cek1 pathway is deactivated. The timing, kinetics, stimuli and functional responses generated upon oxidative stress differ among them; however, they have essential functional consequences that severely influence pathogenesis. MAPK pathways are, therefore, valuable targets to be explored in antifungal research. 相似文献