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51.
N. Ouerfelli 《Physics and Chemistry of Liquids》2018,56(3):412-415
Expressions of Redlich–Kister (RK) excess function using polynomials on difference of molar composition are used. Calculated values of excess properties from experimental values are well presented in some curves as a function of mole fraction (x2) of the second pure component of the studied binary liquid mixture. Nevertheless, the authors presented values of adjustable parameters, not for the polynomial of the popular RK equation (i.e. vs. x2–x1), but for globally the excess property YE as an overall three degree polynomial on (x2) including implicitly the molar fraction product (x1·x2) in their nonlinear regression, which can then induces some readers to probable confusion. 相似文献
52.
连续变化法测定络合物组成和稳定常数是大学化学中的经典学生实验。但针对1:2和1:3的络合反应,实验教科书的设计中可能出现数据点过少也就是溶液配制过少的问题。如果按照要求配制溶液,由于没有完全反应的混合溶液,而其他混合溶液给出的数据又都呈良好的线性,就缺少了用来估算曲线的数据点,结果是,将没有足够的数据对稳定常数进行估算。对这种可能出现的数据点过少的实验设计的原因、结果和解决方法进行了探讨。 相似文献
53.
54.
Shamsuddeen A. Haladu Shaikh A. Ali 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5130-5142
A new zwitterionic monomer 3‐[diallyl{3‐(diethoxyphosphoryl)propyl}ammonio]propane‐1‐sulfonate has been synthesized and cyclopolymerized to give the corresponding polyzwitterion (±) (PZ) bearing both phosphonate and sulfonate functionalities on each repeating unit. phosphonate ester hydrolysis in PZ gave a pH‐responsive dibasic polyzwitterionic acid (±) (PZA) bearing ? PO3H2 units. The PZA under pH‐induced transformation was converted into polyzwitterion/anion (± ?) (PZAN) and polyzwitterion/dianion (± =) (PZDAN) having respective ? PO3H? and ? PO32? units. The polymers′ interesting solubility and viscosity behaviors have been investigated in detail. The apparent protonation constants in salt‐free water and 0.1 M NaCl of the ? PO32? in (± =) (PZDAN) and ? PO3H– in (± ?) (PZAN) as well as in their corresponding monomeric units have been determined. Evaluation of antiscaling properties of the PZA using supersaturated solution of CaSO4 revealed ≈100% scale inhibition efficiency at a meager concentration of 20 ppm for a duration of 45 h at 40 °C. The PZA has the potential to be used effectively as an antiscalant in reverse osmosis plant. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5130–5142 相似文献
55.
Deep level transient spectroscopy has been used to observe the reduced concentrations of vacancy-related defects in γ-irradiated n-type Si containing hydrogen atoms. Data are presented on the efficiency and depth of this damage reduction as a function of the duration and temperature of the exposure to the plasma used to introduce the atomic hydrogen. A 3-hour exposure in an H plasma at 300°C prior to irradiation reduced the concentrations of the O-V, V-V and P-V centres by half or more to a depth of ~20 μm, compared to the control samples. 相似文献
56.
F.A. Mikailov E. Başaran E. Şentürk L. Tümbek T.G. Mammadov V.P. Aliev 《Phase Transitions》2013,86(12):1057-1064
The results of measurements of the dielectric constant of TlGaSe2 in temperature range of successive phase transitions are presented. An anomaly in the temperature dependence of the real part of dielectric constant in TlGaSe2 has been observed at about 242?K in addition to anomalies at 115, 108, and also near 65?K as reported in previous publications. The presence of temperature hysteresis effects in temperature interval between 115 and 242?K allowed making a conclusion about possible existence of an incommensurate phase in the mentioned temperature range. A model of succession of the structural phase transitions in TlGaSe2 has been suggested. 相似文献
57.
《Composite Interfaces》2013,20(3):167-178
In this study, a modified binary polymer blend made up of polycarbonate and polystyrene blend has been prepared by loading of aluminum oxide (Al2O3) as a dopant. The role of alumina with polymer blend system was addressed in view of interfacing criteria. The filler concentration of modified blend was taken as 5, 10, and 15%. The morphological, thermal, and electrical properties were characterized by various techniques. Optical microscopy confirms the homogenous dispersion of Al2O3 in blend. The presence of alumina was detected by subatomic level using atomic force microscope (both two and three dimensional approach). The differential scanning calorimetric thermographs demonstrate decreasing softing point as function of alumina loading. The dielectric properties such as dielectric constant, loss, and electrical modulus were studied under DC bias. The effect of DC bias exhibits significant changes at low amount of Al2O3. The dielectric polarization supports Maxwell Wagner (MW) theory due to low frequency response. 15% Al2O3 gives the highest dielectric constant (ε′) value (3.5?×?105) at 10 Hz. The polymer modified blend with Al2O3 may be used as a one of the best dielectric medium. 相似文献
58.
Apparent correlations are found between the N-H chemical shifts of congeneric series of compounds and the dipole moments of the molecules, such as lactams and thiolactams, cyclic ureas and thioureas. When there is a high degree of correlation, either the N-H chemical shift or the dipole moment of the molecule can be used as an electronic parameter in correlating the biological activity with the chemical structure. In a series of substituted salicylaldehydes the Hammett σ constant gives better correlation with the biological activity than the O-H chemical shift. This is probably due to the anisotropic effect of the substituent besides the electronic effect. Other factors affecting the N-H chemical shift, e.g. intramolecular hydrogen-bonding of nitrosoureas and the deshielding effect of a benzene ring, in o-phenyleneureas are also presented. In spite of the limitations, the chemical shifts of many compounds can be obtained very easily, therefore, their uses in structure-activity correlations deserve further investigation. 相似文献
59.
Dr. Oumaïma Gharbi Dr. Mai T. T. Tran Prof. Mark E. Orazem Dr. Bernard Tribollet Dr. Mireille Turmine Dr. Vincent Vivier 《Chemphyschem》2021,22(13):1371-1378
The different contributions of the interfacial capacitance are identified in the case of passive materials or thin protective coatings deposited on the electrode surface. The method is based on a graphical analysis of the EIS results to determine both the passive-film capacitance in the high-frequency domain and the double-layer capacitance in the low-frequency domain. The proposed analysis is shown to be independent of the physicochemical origins of the frequency dispersion of the interfacial capacitances which results, from an analysis point of view of the experimental results, in the use of a constant-phase element However, for a correct evaluation of the thin-film properties such as its thickness, the high-frequency data must be corrected for the double-layer contribution. In particular, it is shown that if the double-layer capacitance gives a frequency-dispersed response, it is necessary to correct the high-frequency part for the double-layer constant-phase elements. This is first demonstrated on synthetic data and then used for the determination of the thickness of thin oxide film formed on Al in neutral pH solution. 相似文献
60.
From aqueous NaOH/Ca(OH)2/NaAl(OH)4 mixtures, after allowing short reaction times we observed the precipitation of Ca(OH)2(s) at lower, and a mixture of Ca(OH)2(s) and a layered double hydroxide, hydrocalumite (HC) at higher aluminate concentrations. From the maximum aluminate concentration, at which the equilibrium solid phase is still portlandite (i.e., further increase in the aluminate concentration results in HC appearing in the precipitate beside the portlandite), the concentration based solubility products of two polymorphs of HC with the formula of [Ca2Al(OH)6]OH·nH2O (differing in n) has been estimated and was found to be log LHC=−11.4 at 25 °C and −12.1 at 75 °C, respectively (where LHC=[Ca2+]2[Al(OH)4−][OH−]3) and at constant ionic strength (I=1 M NaCl). To the best of our knowledge, this is the first published estimate for the solubility product of hydrocalumite. Additionally, from the composition obtained for NaOH/Ca(OH)2/NaAl(OH)4 mother liquors in equilibrium with Ca(OH)2(s), attempts were made to extract the formation constant of the ion pair CaAl(OH)4+. It was found, that the effects caused by the supposed formation of this solution species are too small to be reliably determined, which allowed an upper estimate for its formation constant, K, to be suggested in the temperature range of 25–75 °C (K<200 and 40 M−1 at 25 and 75 °C, respectively). 相似文献