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471.
S. S. Tahir Rauf Naseem Anwar ul Haq Khalid Saeed 《Accreditation and quality assurance》2005,10(7):362-368
This inter-laboratory comparison study was arranged for 28 laboratories from different public and private sector organizations
in Pakistan having wastewater testing capabilities aimed at improving the quality and comparability of test results. This
national inter-laboratory study was started in December 2003 and completed in July 2004. Laboratories were invited to analyze
the wastewater collected from printed circuit board (PCB) industry for lead and copper contamination. The samples fulfill
the criteria for homogeneity and stability as done by the reference laboratory. The results obtained from participating laboratories
were analyzed in terms of Hampel Test for outliers, while the performance evaluation of the participating laboratories was
done on the basis of Z-score. An assigned value derived from the participant's results was compared with a reference value provided by a reference
laboratory. Overall >50% of the participating laboratories have shown good performance in this PT-program 相似文献
472.
Hai‐Liang Zhu Xiu‐Ying Liu Xian‐Jiang Wang Feng Yang Anwar Usman Hoong‐Kun Fun 《无机化学与普通化学杂志》2003,629(11):1986-1990
Three polymeric silver(I) complexes with terephthalate anions as counterions or ligands, [Ag(pren)]2(tp)·2H2O ( 1 ), [Ag(en)][Ag(μ2‐tp)]·H2O ( 2 ), and [Ag2(μ4‐tp)(apy)2] ( 3 ) (where pren = 1, 2‐propylenediamine, tp =terephthalate dianion, en = ethylenediamine, and apy = 2‐aminopyridine) were synthesized and characterized by X‐ray single crystal analysis and infrared spectroscopy. 1 crystallizes in the monoclinic space group P211/c with a = 11.3221(5), b = 7.1522(3), c = 14.8128(5)Å, V = 1015.77(7)Å3, β = 122.132(2), and Z = 2. 2 crystallizes in the orthorhombic space group Pnma with a = 9.6144(6), b = 11.3465(7), c = 11.4810(7)Å, V = 1252.5(1)Å3, and Z = 4. 3 crystallizes in the monoclinic space group P21/n with a = 8.2003(5), b = 5.8869(4), c = 18.3769(11)Å, β = 92.593(1), V = 886.2(1)Å3, and Z = 4. Terephthalate dianions are not coordinated to the metal atoms in 1 , but act as a μ2‐bridging ligand in 2 and as a μ4‐bridging ligand in 3 . 相似文献
473.
Blazina D Duckett SB Halstead TK Kozak CM Taylor RJ Anwar MS Jones JA Carteret HA 《Magnetic resonance in chemistry : MRC》2005,43(3):200-208
We describe a number of studies used to establish that parahydrogen can be used to prepare a two-spin system in a pure state, which is suitable for implementing NMR quantum computation. States are generated by pulsed and continuous-wave (CW) UV laser initiation of a chemical reaction between Ru(CO)(3)(L(2)) [where L(2) = dppe = 1,2-bis(diphenylphosphino)ethane or L(2) = dpae = 1,2-bis(diphenylarsino)ethane] with pure parahydrogen (generated at 18 K). This process forms Ru(CO)(2)(dppe)(H)(2) and Ru(CO)(2)(dpae)(H)(2) on a sub-microsecond time-scale. With the pulsed laser, the spin state of the hydride nuclei in Ru(CO)(2)(dppe)(H)(2) has a purity of 89.8 +/- 2.6% (from 12 measurements). To achieve comparable results by cooling would require a temperature of 6.6 mK, which is unmanageable in the liquid state, or an impractical magnetic field of 0.44 MT at room temperature. In the case of CW initiation, reduced state purities are observed due to natural signal relaxation even when a spin-lock is used to prevent dephasing. When Ru(CO)(3)(dpae) and pulsed laser excitation are utilized, the corresponding dihydride product spin state purity was determined as 106 +/- 4% of the theoretical maximum. In other words, the state prepared using Ru(CO)(3)(dpae) as the precursor is indistinguishable from a pure state. 相似文献
474.
John RP Sreekanth A Prathapachandra Kurup MR Usman A Ibrahim AR Fun HK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(6):1349-1358
The spectral studies and structure of a ternary complex of copper(II) with 2-hydroxyacetophenone 3-hexamethyliminylthiosemicarbazonate (L(2-)) and 1,10-phenanthroline (phen) are reported. The thiosemicarbazone binds to the metal as a dianionic ONS-donor (L(2-)) ligand, and forms a complex of the stoichiometry [CuLphen]. The copper(II) complex was characterized by IR and UV/Vis spectroscopies, as well as by solid state room-temperature magnetic susceptibility. Spin Hamiltonian and bonding parameters of the compound are calculated from the EPR spectra. Computer simulation of EPR spectrum in DMF at 77 K aided the calculation of magnetic and bonding parameters of the compound. The structure of the compound is solved by single crystal X-ray diffraction. The geometry around copper is distorted square pyramidal. 相似文献
475.
Chloride was determined at nanogram levels by adding excess of indium to the sample introduced into a graphite furnace and measuring the laser induced molecular fluorescence of indium chloride. The diatomic molecules of indium chloride were excited by a pulsed dye laser at 267 nm and fluorescence was measured at 359 nm. The effects of various parameters including amount of indium added, furnace thermal conditions and presence of concomitants were also studied. A linear calibration in the range of 0.025-1.25 ng and a detection limit of 17 pg of chloride were obtained under optimum conditions. The analytical usefulness of the method was checked by determining the chloride content in National Institute of Standards and Technology, Standard Reference Materials 1571a and 1571b Orchard Leaves. 相似文献
476.
Zhang Ze Liu Qing-Liang Yang Jia-Xiang Wu Jie-Ying Tian Yu-Peng Jin Bao-kang Fun Hoong-Kun Chantrapromma Suchada Usman Anwar 《Transition Metal Chemistry》2003,28(8):930-934
The title complex [Mn2(phen)4(FCA)2](ClO4)2·H2O (1) (FCA = dianion of 3-ferrocenyl-2-crotonic acid, phen = 1,10-phenanthroline) has been prepared, and its structure determined by single crystal X-ray diffraction analysis. The structure consists of a dinuclear cation [Mn2(phen)4(FCA)2]2+, non-coordinated perchlorate anions and a water molecule. The two MnII ions are separated by 4.374 Å in the cation and are dicarboxylate-bridged by carboxylate ligands containing ferrocenyl units. Each FCA is bound to two MnII ions through carboxylate oxygens with the syn–anti bridging mode. The MnII ion is coordinated in an octahedral N4O2 geometry by two chelate phen ligands and two -carboxylate oxygen atoms. Electrochemical properties of (1) are discussed. 相似文献
477.
Steam distilled oils of some species of the genus Citrus and Cymbopogon citratus were analyzed by GC-MS. It is observed that citral b was the most common constituent of the oils, which could be a good inhibitor of beta-glucuronidase as all the tested essential oils showed significant inhibition of beta-glucuronidase. IC50 values of a mixture of citral a and b also proved the hypothesis. The same oils also exhibited positive response against tested microbes. 相似文献
478.
479.
The densities, ρ, and ultrasonic speeds, u, have been measured in the binary liquid mixtures of acetonitrile (ACN) with 1‐hexanol, 1‐octanol and 1‐decanol, and in the pure components, as a function of composition at 25, 30, 35, 40 and 45 °C. The deviations in isentropic compressibility, Δκs, excess molar volume, VE, deviations in ultrasonic speed, Δu, apparent molar compressibility, K?2, apparent molar volume, V?2, partial molar compressibility, $ {\rm \bar K}^\circ _{\phi,2} $, and partial molar volume, $ {\rm \bar V}^\circ _2 $, of 1‐alkanols in ACN have been calculated from the experimental data of densities and ultrasonic speeds. The variations of these parameters with composition of the mixtures indicate that the structure‐breaking effect dominates over that of the hydrogen‐bonding effect between unlike molecules, suggesting that ACN‐alkanol interaction is weaker than ACN‐ACN and alkanol‐alkanol interactions, and that the interaction (ACN‐alkanol) follows the order: 1‐hexanol > 1‐octanol > 1‐decanol. The excess molar volume data have been analysed by using Flory and Prigogine‐Flory‐Patterson theories. Further, the ultrasonic speeds in these mixtures were theoretically calculated with the help of several theories and empirical relations using the pure component data. The validity and relative merits of these theories and relations have been discussed. 相似文献
480.
In this paper free acid and uranium present together in the range of 0.05–3.0 meq and 20–250 mg, respectively, have been determined by potentiometric titration, using Na2SO4 and (NH4)2SO4 complexants and NaOH and Na2CO3 as titrants. The results are presented as percentage recovery of free acidity and uranium over the range studied. It has been shown that percentage recovery of free acidity suggests a bias which varied from –5% to +74% at different free acidity and uranium concentrations for the Na2SO4–NaOH, Na2SO4–Na2CO3 and (NH4)2SO4–NaOH complexant — titrant combinations. The percentage recovery of uranium always showed a positive bias which could be up to +8% for extreme free acidity — uranium ratios in the case of Na2SO4–Na2CO3 complexant — titrant combination. For the other Na2SO4–NaOH and (NH4)2SO4–NaOH complexant — titrant combinations a positive bias of up to only +4% has been noticed. 相似文献