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101.
To improve the reproducibility, stability, and sensitivity of bismuth film electrode (BiFE), we studied the performances of a mixed coating of two cation‐exchange polymers, Nafion (NA) and poly(sodium 4‐styrenesulfonate) (PSS), modified glassy carbon BiFE (GC/NA‐PSS/BiFE). The characteristics of GC/NA‐PSS/BiFE were investigated by scanning electron microscopy and cyclic voltammetry. Various parameters were studied in terms of their effect on the anodic stripping voltammetry (ASV) signals. Under optimized conditions, the limits of detection were 71 ng L?1 for Cd(II) and 93 ng L?1 for Pb(II) with a 10 min preconcentration. The results exhibited that GC/NA‐PSS/BiFE can be a reproducible and robust tool for monitor of trace metals by ASV rapidly and environmentally friendly, even in the presence of surface‐active compounds. 相似文献
102.
A protocol has been developed for the reliable titration of aqueous sulfite solutions which minimizes photodecomposition effects.
This procedure has been used to measure the protonation constants of the sulfite ion in aqueous solution by glass electrode
potentiometry at 25.0‡C and ionic strengths (I) from 0.1 to 5.0M in NaCI media and atI = 1.0M in KC1 and Me4NCl media. These measurements provided evidence of weak but significant ionpairing between SO2/3 -and Na+ with a formation constant of logK
Na = 0.431 in 1.0M Me4NCl. This was in very good agreement with the value logK
Na = 0.410 measured directly by Na+ ion-selective electrode potentiometry. Evidence is also presented for an extremely weak association of K+ and SO
2
3
-with logK
k
= 0.22 in 1.0M Me4NCl. 相似文献
103.
The electrical conductivities of aqueous solutions of NaCF3SO3, KCF3SO3, and Ni(CF3SO3)2 have been measured at 25‡C in the concentration range 1 to 25X 10-3 mol-dm-3 The data approach the Onsager limiting law at low concentrations, leading to a limiting molar ion conductivity for the CF3SO
3
−
ion of 44.5±0.2 S-cm2-mol-1, based on standard values for the cations. Using a simple size parameter for unsymmetrical polyatomic ions, based on the
ion geometry, it is shown that the well known empirical relation between the molar conductivities of symmetrical ions and
their radii can be extended to include certain polyatomic anions including CF3SO
3
−
. The results suggest that the CF3SO
3
−
ion is either a weak structure breaker in aqueous solution or neutral in this respect. 相似文献
104.
J. L. Oscarson R. M. Izatt P. R. Brown Z. Pawlak S. E. Gillespie J. J. Christensen 《Journal of solution chemistry》1988,17(9):841-863
The aqueous reactions,
相似文献
105.
106.
Efficient synthesis of cyclic -alkyl--dicarbonyl compounds of the cyclopentane, cyclohexane, tetronic acid, and -pyrone series from the corresponding cyclic -acyl--dicarbonyl compounds under the action of NaBH3(CN) in a THF--HCl system is described. 相似文献
107.
108.
Novel meander with Co3+ und Au3+: Na4[AuCoO5] = Na8 1∞ [(O2/2 (CoO)O2AuO2/2)2] By “reaction with the wall” we obtained for the first time transparent brown single crystals of Na4[AuCoO5] while heating intimate mixtures of Co3O4, Na2O2, and K2O2 (Co: Na: K = 1.00:4.91:2.20; 650°C/44d) in a sealed gold-tube: monoclinic, P21/m, with a = 555.69(4) pm, b = 1042.11 (8) pm, c = 555.69(4) pm, β = 117.387(5)°, Z = 2. Characteristic features of Na4[AuCoO5] are meandric chains [(O2/2 (CoO)O2AuO2/2)2]. The structure has been determined by four-circle diffractometer data (Siemens AED 2; Mo? Kα , graphite, 881 I0(hkl), R = 0.0366, Rw = 0.0316), parameters as given in the text. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, these via Mean Fictive Ionic Radii, and Charge-distribution, CHARDI, are calculated and discussed. 相似文献
109.
P. Ekwall 《Colloid and polymer science》1988,266(3):279-282
Previous studies of the occurrence of acid soaps in systems containing a longchain sodium soap and the corresponding fatty acid, and the study of phase equilibria in the system sodium octanoate — octanoic acid — water, performed by our group at the beginning of the 1960s, show that the isotropic liquidL
2-phase of the last mentioned system in its whole region of existence is situated in that part in which acid soaps occur. This provides an explanation for the fact that theL
2-phase itself contains acid sodium octanoates in all regions. TheL
2-phase has its origin in the water-free melt of fatty acid and neutral soap in which these components react with each other under the formation of an acid soap. When water is added to the system, this water-free acid soap is transformed into different hydrated acid soaps. In a large region of concentration, there is an extremely close relation between theL
2-phase and the liquid-crystalline lamellarD-phase, which itself consists of hydrated acid soaps. At its outermost water-rich tip, theL
2-phase is in equilibrium with theL
1-phase of the system, just above the+LAC, that is, with the most dilute aqueous soap solution in which acid soap still may be formed in aqueous environment. Formation of acid soap is a fundamental requirement for the existence of this isotropic liquidL
2-phase. 相似文献
110.
J. G. Dunn A. C. Chamberlain N. G. Fisher J. Avraamides 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1399-1408
The thermal decomposition of SEX in a nitrogen atmosphere was studied by coupled thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The TG curve exhibited two discrete mass losses of 45.8% and 17.8% respectively, at 200 and 257–364°C. The evolved gases identified as a result of the first mass loss were carbonyl sulfide (COS), ethanol (C2H5OH), ethanethiol (C2H5SH), carbon disulfide (CS2), diethyl sulfide ((C2H5)2S), diethyl carbonate ((C2H5O)2CO), diethyl disulfide ((C2H5)2S2), and carbonothioic acid, O, S, diethyl ester ((C2H5S)(C2H5O)CO). The gases identified as a result of the second mass loss were carbonyl sulfide, ethanethiol, and carbon disulfide. Hydrogen sulfide was detected in both mass losses by py-GC-MS, but not detected by FTIR. The solid residue was sodium hydrogen sulfide (NaSH).SEX was adsorbed onto activated carbon, and heated in nitrogen. Two discrete mass losses were still observed, but in the temperature ranges 100–186°C (7.8%) and 186–279°C (11.8%). Carbonyl sulfide and carbon disulfide were now the dominant gases evolved in each of the mass losses, and the other gaseous products were relatively minor. It was demonstrated that water adsorbed on the carbon hydrolysed the xanthate to cause the first mass loss, and any unhydrolysed material decomposed to give the second mass loss.Mr. N. G. Fisher would like to thank the A. J. Parker CRC for Hydrometallurgy for the provision of a PhD scholarship. 相似文献
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