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991.
A feasibility study was carried out on the utilization of Alkanolamide (ALK) on silica reinforcement of natural rubber (NR) by using a semi-efficient cure system. The ALK was incorporated into the NR compound at 1.0, 3.0, 5.0, 7.0 and 9.0 phr. An investigation was carried out to examine the effect of ALK on the cure characteristics and properties of NR compounds. It was found that ALK gave shorter scorch and cure times for silica-filled NR compounds. ALK also exhibited higher torque differences, tensile modulus, tensile strength, hardness and crosslink density of up to 5.0 phr of ALK loading, and then decreased with further increases of ALK loading. The resilience increased with increased ALK loading. Scanning electron microscopy (SEM) micrographs proved that 5.0 phr of ALK in the silica-filled NR compound exhibited the greatest matrix tearing line and surface roughness due to higher reinforcement level of the silica, as well as better dispersion and cure enhancement. 相似文献
992.
We have measured electronic and Raman scattering spectra of 1,1',3,3'-tetraethyl-5,5',6,6'-tetrachloro-benzimidazolocarbocyanine iodide (TTBC) in various environments, and we have calculated the ground state geometric and spectroscopic properties of the TTBC cation in the gas and solution phases (e.g., bond distances, bond angles, charge distributions, and Raman vibrational frequencies) using density functional theory. Our structure calculations have shown that the ground state equilibrium structure of a cis-conformer lies ~200 cm(-1) above that of a trans-conformer and both conformers have C(2) symmetry. Calculated electronic transitions indicate that the difference between the first transitions of the two conformers is about 130 cm(-1). Raman spectral assignments of monomeric- and aggregated-TTBC cations have been aided by density functional calculations at the same level of the theory. Vibrational mode analyses of the calculated Raman spectra reveal that the observed Raman bands above 700 cm(-1) are mainly associated with the in-plane deformation of the benzimidazolo moieties, while bands below 700 cm(-1) are associated with out-of-plane deformations of the benzimidazolo moieties. We have also found that for the nonresonance excited experimental Raman spectrum of aggregated-TTBC cation, the Raman bands in the higher-frequency region are enhanced compared with those in the nonresonance spectrum of the monomeric cation. For the experimental Raman spectrum of the aggregate under resonance excitation, however, we find new Raman features below 600 cm(-1), in addition to a significantly enhanced Raman peak at 671 cm(-1) that are associated with out-of-plane distortions. Also, time-dependent density functional theory calculations suggest that the experimentally observed electronic transition at ~515 nm (i.e., 2.41 eV) in the absorption spectrum of the monomeric-TTBC cation predominantly results from the π → π? transition. Calculations are further interpreted as indicating that the observed shoulder in the absorption spectrum of TTBC in methanol at 494 nm (i.e., 2.51 eV) likely results from the ν(") = 0 → ν' = 1 transition and is not due to another electronic transition of the trans-conformer-despite the fact that measured and calculated NMR results (not provided here) support the prospect that the shoulder might be attributable to the 0-0 band of the cis-conformer. 相似文献
993.
Namik Özdemi̇r Bi̇lge Eren Muharrem Di̇nçer Yunus Bekdemi̇r 《International journal of quantum chemistry》2011,111(12):3112-3124
The title molecule, 2‐(4‐chlorophenyl)‐1‐methyl‐1H‐benzo[d]imidazole (C14H11ClN2), was prepared and characterized by 1H NMR, 13C NMR, IR, and single‐crystal X‐ray diffraction. The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of the title compound in the ground state have been calculated by using the Hartree‐Fock (HF) and density functional theory (DFT/B3LYP) method with 6‐31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies and GIAO 1H and 13C NMR chemical shifts show good agreement with experimental values. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6‐31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, and nonlinear optical (NLO) properties of the title compound were investigated by theoretical calculations. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
994.
A new ion source has been developed for rapid, noncontact analysis of materials at ambient conditions. The method provides desorption of analytes under ambient conditions directly from different surfaces with little or no sample preparation. The new method, termed electrode‐assisted desorption electrospray ionization (EADESI), is on the basis of the ionization of molecules on different surfaces by highly charged droplets produced on a sharp‐edged high voltage tip, and ions produced are introduced into the mass spectrometer through a capillary. The EADESI technique can be applied to various samples including amino acids, peptides, proteins, drugs and human fluids such as urine and blood. EADESI is promising for routine analyses in different fields such as forensic, environmental and material sciences. EADESI interface can be fit to a conventional ion‐trap mass spectrometer. It can be used for various types of samples with a broad mass range. EADESI can also provide real‐time analysis which is very valuable for biomedical applications. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
995.
F. Yurt P. Ünak H. Özkiliç I. Tuĝlular 《Journal of Radioanalytical and Nuclear Chemistry》1995,200(1):75-83
Diazepam, which aims at benzodiazepine receptors and can be used as a specific SPECT agent has been labeled with [131I]2-iododiazepam (2-IDZ) was obtained in 50% HCl medium and [131I]2-iododiazepam (2-IDZ) was prepared by the iodogen method. The products were purified by passing through a Dowex-1 anion-exchange column. 相似文献
996.
Direct catalytic enantioselective aza-Diels-Alder reactions 总被引:1,自引:0,他引:1
Sundén H Ibrahem I Eriksson L Córdova A 《Angewandte Chemie (International ed. in English)》2005,44(31):4877-4880
997.
Khalid A. Al-Farhan Ismail Warad Saud I. Al-Resayes Moustafa M. Fouda Mohamed Ghazzali 《Central European Journal of Chemistry》2010,8(5):1127-1133
Borneol is a monoterpene that is a part of traditional Chinese and Japanese medicine. (−) borneol reacted with methanesulfonyl
chloride in THF/pyridine to afford the new 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl methane sulfonate derivative in excellent
yield. The product is characterized by H1NMR, C13NMR, mass spectroscopy as well as elemental analysis and its structure was identified by X-ray single crystal diffraction.
The packing of 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl methanesulfonate exhibits the non-classical C-H···O hydrogen bonding
in C(4) and R2
2(8) chain and ring motifs as structural determinants. This was also confirmed by the analysis of Hirshfeld surfaces. The 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl
methane sulfonate antimicrobial activity was tested and compared with its parent (−) borneol against three different pathogens.
Particularly, 1,7,7-trimethylbicyclo[2.2.1]hept-2-yl methane sulfonate showed high sensitivity, compared to Chloramphenicol
reference material, against Escherichia coli.
相似文献
998.
Fyaz M. D. Ismail Michael G. B. Drew Suppiah Navaratnam Roger H. Bisby 《Research on Chemical Intermediates》2009,35(4):363-377
Free radicals from one-electron oxidation of the antimalarial drug pyronaridine have been studied by pulse radiolysis. The
results show that pyronaridine is readily oxidised to an intermediate semi-iminoquine radical by inorganic and organic free
radicals, including those derived from tryptophan and acetaminophen. The pyronaridine radical is rapidly reduced by both ascorbate
and caffeic acid. The results indicate that the one-electron reduction potential of the pyronaridine radical at neutral pH
lies between those of acetaminophen (707 mV) and caffeic acid (534 mV). The pyronaridine radical decays to produce the iminoquinone,
detected by electrospray mass spectrometry, in a second-order process that density functional theory (DFT) calculations (UB3LYP/6-31+G*)
suggest is a disproportionation reaction. Important calculated dimensions of pyronaridine, its phenoxyl and aminyl radical,
as well as the iminoquinone, are presented.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
999.
Comparison of detection limits, for two metallic matrices, of laser-induced breakdown spectroscopy in the single and double-pulse configurations 总被引:4,自引:0,他引:4
Ismail MA Cristoforetti G Legnaioli S Pardini L Palleschi V Salvetti A Tognoni E Harith MA 《Analytical and bioanalytical chemistry》2006,385(2):316-325
Limits of detection have been studied for several elements in aluminium and steel alloys, at atmospheric pressure in air,
by use of the single and collinear double-pulse configurations of laser-induced breakdown spectroscopy. For this purpose,
calibration plots were constructed for Mg, Al, Si, Ti, Cr, Mn, Fe, Ni, and Cu using a set of certified aluminium alloy samples
and a set of certified steel samples. The investigation included optimization of the experimental conditions to furnish the
best signal-to-noise ratio. Inter-pulse delay, gate width, and acquisition delay were studied. The detection limits for the
elements of interest were calculated under the optimum conditions for the double-pulse configuration and compared with those
obtained under the optimum conditions for single-pulse configuration. Significantly improved detection limits were achieved,
for all the elements investigated, and in both aluminium and steel, by use of the double-pulse configuration. The experimental
findings are discussed in terms of the measured plasma conditions (particle and electron density, and temperature). 相似文献
1000.
The high-molecular-weight polynuclear aromatic hydrocarbon (PAC) fraction of a carbon black extract was isolated with a backflush technique, and applied to an amino-bonded stationary phase for HPLC. This fraction was further separated into 44 sub-fractions by means of reversed-phase HPLC, on an ODS column. Low-temperature fluorescence, utilizing the Shpol'skii effect, was then applied to each fraction. By this method, quasilinear spectra were recorded from mostly peri- condensed PACs with molecular weights up to 400 daltons. Nine compounds with molecular weights exceeding 300 daltons were identified. 相似文献