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101.
A new experimental approach is proposed for the evaluation of liquid junction potentials and single ion activities. Neither of these quantities can be experimentally measured without assumption. Furthermore, they are concentration dependent but without clearly defined functional relationships. Thus, a given assumption may be satisfactory to obtain these quantities at a given concentration, but will fail at another concentration. It is the intent of this paper to establish a functional relationship between the ratio of activity coefficients and the ionic strength, through which the liquid junction potentials may be computed, as well as the pH values at moderate ionic strengths (<1.0 m). Experimental results are presented and uncertainties are discussed. 相似文献
102.
A chemo-electro-mechanical multi-field model, termed the multi-effect-coupling pH-electric-stimuli (MECpHe) model, has been
developed to simulate the response behavior of smart hydrogels subject to pH and electric voltage coupled stimuli when the
hydrogels are immersed in a pH buffer solution subject to an externally applied electric field. The MECpHe model developed
considers multiphysics effects and formulates the fixed charge density with the coupled buffer solution pH and electric voltage
effects, expressed by a set of nonlinear partial differential governing equations. The model can be used to predict the hydrogel
displacement and the distributive profiles of the concentrations of diffusive ionic species and the electric potential and
the fixed charge density in both the hydrogels and surrounding solution. After validation of the model by comparison of current
numerical results with experiment data extracted from the literature, one-dimensional steady-state simulations were carried
out for equilibrium of the smart hydrogels subject to pH and electric coupled stimuli. The effects of several important physical
conditions, including the externally applied electric voltage, on the distributions of the concentrations of diffusive ionic
species, the electric potential, the fixed charge density, and the displacement of the hydrogel strip were studied in detail.
The effects of the ionic strength on the bending deformation of the hydrogels under the solution pH and electric voltage coupled
stimuli are also discussed. 相似文献
103.
用结晶紫选择性电极(自制)以催化电位法对测定微量锰进行了研究。该方法测定标的线性范围为7~74μg/L,对标准钢样中的锰含量测定结果满意,且操作方便。 相似文献
104.
An extract of crystal violet-tetrachloroferrate(III) in nitrobenzene was used to prepare a tetrachloroferrate(III)-selective liquid membrane electrode with a poly(vinyl chloride) support. The optimal conditions to determine 2.5 × 10–5 – 5.0 × 10–2
M iron(III) as tetrachloroferrate(III) (anionic slope 56 mV/decade, detection limit 7.9 × 10–6
M) were found to be 4.0–5.5.M total chloride in 0.75–1.5M hydrochloric acid. The electrode was reliably applied to determine iron in human blood, haematite and mineralized vitamin syrup by direct potentiometry, standard and sample additions as well as standard subtraction techniques. 相似文献
105.
Richard M. Kettler Donald A. Palmer David J. Wesolowski 《Journal of solution chemistry》1995,24(1):65-87
The first and second molal dissociation quotients of succinic acid were measured potentiometrically with a hydrogen-electrode, concentration cell. These measurements were carried out from 0 to 225°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The dissociation quotients from this and two other studies were combined and treated with empirical equations to yield the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: log K1a=–4.210±0.003; H
1a
0
=2.9±0.2 kJ-mol–1; S
1a
0
=–71±1 J-mol–1-K–1; and C
p1a
0
=–98±3 J-mol–1-K–1; and for the second acid dissociation equilibrium at 25°C: log K2a=–5.638±0.001; H
2a
0
= –0.5±0.1 kJ-mol–1; S
2a
0
=–109.7±0.4 J-mol–1-K–1; and C
p2a
0
= –215±8 J-mol–1-K–1. 相似文献
106.
Dr. Vinayak Adimule R. G. Revaiah Santosh S. Nandi Adarsha Haramballi Jagadeesha 《Electroanalysis》2021,33(3):579-590
In the present work, Cr doped tellurium dioxide nanostructures (CTO NS)(1 wt %, 6 wt %, 8 wt % and 12 wt %) synthesized by co precipitation method and characterized by CV, UV-Visible, SEM, XRD, XPS spectroscopic analysis. Electron beam deposited thin film of CTO NS having 12 wt % of Cr exhibited EGFET-pH sensitivity of 62.03 mV/pH at 250 °C in buffer solutions of pH 6–12, linearity 0.9345, drift rate of 1.12 mV/h and deviation of 0.01145 as compared with 1 wt %, 6 wt % and 8 wt % of CTO NS. 相似文献
107.
Nikola Saka
Dean Markovi Bojan arkanj Dubravka Maduni-a
i Krunoslav Hajdek Boo Smoljan Marija Jozanovi 《Molecules (Basel, Switzerland)》2021,26(5)
A novel, simple, low-cost, and user-friendly potentiometric surfactant sensor based on the new 1,3-dihexadecyl−1H-benzo[d]imidazol−3-ium-tetraphenylborate (DHBI–TPB) ion-pair for the detection of cationic surfactants in personal care products and disinfectants is presented here. The new cationic surfactant DHBI-Br was successfully synthesized and characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectrometry, liquid chromatography–mass spectrometry (LC–MS) and elemental analysis and was further employed for DHBI–TPB ion-pair preparation. The sensor gave excellent response characteristics for CTAB, CPC and Hyamine with a Nernstian slope (57.1 to 59.1 mV/decade) whereas the lowest limit of detection (LOD) value was measured for CTAB (0.3 × 10−6 M). The sensor exhibited a fast dynamic response to dodecyl sulfate (DDS) and TPB. High sensor performances stayed intact regardless of the employment of inorganic and organic cations and in a broad pH range (2−11). Titration of cationic and etoxylated (EO)-nonionic surfactant (NSs) (in Ba2+) mixtures with TPB revealed the first inflexion point for a cationic surfactant and the second for an EO-nonionic surfactant. The increased concentration of EO-nonionic surfactants and the number of EO groups had a negative influence on titration curves and signal change. The sensor was successfully applied for the quantification of technical-grade cationic surfactants and in 12 personal care products and disinfectants. The results showed good agreement with the measurements obtained by a commercial surfactant sensor and by a two-phase titration. A good recovery for the standard addition method (98–102%) was observed. 相似文献
108.
铅在铂电极上的还原电位溶出分析法 总被引:1,自引:0,他引:1
研究了以亚铁氰化钾为还原剂铅在铂电极上的还原电位溶出法;讨论了电极的预处理、阳极富集和随后的还原电位溶出及铅测定的干扰。 相似文献
109.
Liposome-Based Optochemical Nanosensors 总被引:2,自引:0,他引:2
This paper describes the optochemical pH and oxygen sensing properties of dye-encapsulating and fluorescently labeled nano-sized
unilamellar liposomes. To prepare the oxygen sensitive liposomes a lipid mixture consisting of dimyristoylphospatidylcholine,
cholesterol, and dihexadecyl phosphate (molar ratio 5:4:1) all dissolved in dry isopropyl alcohol is injected into a sensing
dye solution. The mixture is then sonicated with a liposome maker to form dye-encapsulating liposomes. A lipid mixture consisting
of dimyristoylphospatidylcholine, N-(fluorescein-5-thiocarbamoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (fluorescein DHPE),
cholesterol, and dihexadecyl phosphate (molar ratio 20:1:16:4) is used to prepare the pH sensitive liposomes by the same sonication
technique. Fluorescein labeled DHPE phospholipids are combined with DMPC phospholipids in a 1:20 ratio to incorporate the
sensing dye directly into the bilayer membrane, virtually eliminating any instability due to dye leakage. Oxygen sensing liposomes
are created by encapsulating the oxygen sensitive ruthenium tris(1,10)-phenanthroline complex [Ru(phen)3]. The dye is believed to exist both in free solution within the liposome, and as an adherent on the inner membrane of the
liposome. High uniformity of the liposomes is realized by extruding them back and forth through a 100 nm pore-size polycarbonate
membrane. TEM images of the liposomes, stained with uranyl acetate, show that the liposomes are unilamellar, spherical in
shape, maintain high structural integrity, and average 70 nm in diameter. The liposomes show high stability with respect to
dye leaking at room temperature for 8 days, and high photostability when exposed to the excitation light. Individual liposomes
are used to monitor the pH and oxygen level in their vicinity during the enzymatic oxidation of glucose by the enzyme glucose
oxidase. The newly prepared environmentally sensitive liposomes can be applied for non-invasive pH and oxygen determination
in tissues and single biological cells.
Received June 8, 1998. Revision November 10, 1998. 相似文献
110.
A. V. M. Chandramalar Y. Y. Lim Y. K. Leong 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,160(3):49-205
The effects of cis- and trans-1,2-, trans-1,4-cyclohexanedicarboxylic acid, 95% cis-1,3,5-cyclohexane tricarboxylic acid and cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid on the yield stress–pH behaviour of concentrated ZrO2 dispersions are reported. Adsorbed cis-1,2,3,4,5,6-cyclohexanehexacarboxylic acid imparts predominantly steric interactions. It forms a steric barrier keeping the interacting particles apart. Adsorbed cis- and trans-1,2 increase the maximum yield stress and this was attributed to a hydrophobic force resulting from the part of the cyclohexane ring sticking out into the solution which is devoid of charged or hydrophilic group. Adsorbed trans-1,4 increases the maximum yield stress by at least threefold and its configuration favours strong bridging interaction with an adjacent particle. Predominantly, cis-1,3,5 also increases the maximum yield stress but only by 60% at the same additive concentration. This was attributed to a smaller degree of bridging. 相似文献