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181.
Influence of rheological additives on char formation and fire resistance of intumescent coatings 总被引:1,自引:0,他引:1
Styrene-butyl acrylate copolymer based fire retardant coatings were prepared using intumescent flame-retardant additives and mineral clay type rheological additives. Three different widely used nanoclays, organic-modified montmorillonite, palygorskite and sepiolite were applied in order to determine their effect on the flame retardancy. Significant differences were found when their heat-shielding activities were evaluated. It was observed that the addition of different clay particles in amount of 0.25 w% changes the char formation process; the height, the morphology, the structure and also the mechanical resistance of the protecting shield. The different geometry and composition of the additives induced different changes in fire performance. In case of palygorskite the catalytic effect of Fe accelerated mainly the thermal decomposition, therefore the fire resistance decreased. The plate-like montmorillonite reduced the extent of the intumescent char, whereas also improved the mechanical and sustained heat resistance of the fire protecting shield. The fibrous sepiolite of low Fe content assisted the development of efficient protecting shield, which exhibited optimal cell structure, suitable thickness, and thus ensured better heat-insulating performance. Consequently, fire retardant effect of sepiolite was found to be better than the other studied clay types. 相似文献
182.
Hunter HN Hadei N Blagojevic V Patschinski P Achonduh GT Avola S Bohme DK Organ MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(28):7845-7851
Negishi cross-coupling reactions were analyzed in solution by mass spectrometry and NMR spectroscopy to identify both the effect of LiBr as an additive as well as the purpose of 3-dimethyl-2-imidazolidinone (DMI) as a co-solvent. The results suggest that the main role of DMI is to facilitate a higher order bromozincate formation during the addition of LiBr. 相似文献
183.
184.
离子色谱法测定液体乳制品中硫氰酸盐 总被引:2,自引:0,他引:2
提出了离子色谱法测定液体乳中硫氰酸盐的方法。鲜奶或酸奶样品经乙腈提取和C18固相萃取柱净化后,再经Ion Pac AG11-HG保护柱及Dionex ICS-3000分离柱分离,由70 mmol.L-1氢氧化钾溶液洗脱,利用电导检测器检测。硫氰酸盐的质量浓度在0.20~10.0 mg.L-1范围内呈线性,方法的检出限(3S/N)为0.08 mg.L-1。方法用于鲜奶和酸奶样品分析,回收率在92.5%~104.5%之间,相对标准偏差(n=6)小于4.5%。 相似文献
185.
Akito Kobayashi Yoshiaki
no Tamifusa Matsuura Yoshihiro Kuroda 《Physica C: Superconductivity and its Applications》1998,300(3-4):287-300
Dynamical spin susceptibility χs(q,ω) of the d–p model in the over doping region is investigated by using the auxiliary boson technique. It includes higher order terms of the 1/N-expansion within the random phase approximation (RPA) of the local vertex, where frequency dependence of the quasi-particle interaction is taken into account. The incommensurate spin fluctuation is obtained due to the nesting effect in the low energy region (ωω*), whereas the commensurate one in the high energy region (ωω*), the characteristic energy ω* is estimated to be about 30 meV. Both of the spin–lattice relaxation rate 1/T1 and the spin–spin relaxation rate 1/Tg monotonically increase as T decreases, while the spin Knight shift K is almost independent of T. 相似文献
186.
Ricardo Jimnez 《Solid State Ionics》1996,90(1-4):233-244
The a.c. electrical response of an electrically isotropic solid electrolyte pressed powder pellet, has been calculated using the Percolation Effective Medium Theory (P.E.M.T.) approximation. The pressed powder pellet is represented by a mixture of a conducting phase (solid electrolyte) and an isolation one (air). The physical meaning of the derived results is discussed in reference to a real solid electrolyte pellet response. The pellet response calculated by the P.E.M.T. equation should correspond to the usual ‘bulk’ one. The influence of the microstructure on the pellet response, derived from the model, can be used to improve the ‘bulk’ ionic conductivity, in pressed powder pellets of solid electrolytes with isotropic conductivity, and to obtain its real electrical characteristics. 相似文献
187.
用EHMO/CO方法计算了高取向顺式聚乙炔及其碘掺杂物的二维能带结构,并据此讨论了它们导电性能的各向异性问题,结果表明平行于分子链方向的导电率与垂直于该方向的电导率之比(σ‖/σ⊥)取决于这两个方向上的价带宽和导带宽。碘掺杂后σ‖/σ⊥下降的原因是链间耦合增加。碘掺杂后的顺式聚乙炔是一个链间相互作用微弱的的二维或三维体系。计算结果与实验较好地吻合。 相似文献
188.
Possible errors in the widely used 1972–1973 macroscopic original-electric-modulus formalism are identified, corrected, and their consequences considered. These errors include misidentification of the high-frequency-limiting dielectric constant arising entirely from mobile charges, εC1∞, and the failure to treat properly the high-frequency-limiting dielectric constant associated with bulk dipolar and vibrionic effects, εD∞. It is shown that the corrected modulus formalism, which describes dispersed mobile-charge effects, is isomorphic in form with the 1973 microscopic continuous-time random-walk hopping model of Scher and Lax after a minor but significant correction is made to the latter's response function. This firmly established correction, which nevertheless could not be determined by Kronig–Kramers transformation, involved inversion of synthetic frequency-response data to determine a distribution of relaxation times and led to extension of the real part of the Scher–Lax dielectric response to higher frequencies by the inclusion of a nonzero limiting value. This isomorphism, along with excellent data fitting using the corrected modulus formalism, suggests that since the Scher–Lax stochastic model involves no explicit Coulomb interactions, cation motion in glasses is dominated by short-range interactions. Finally, two very-high-frequency processes, which each lead to a limiting plateau value of the real part of the conductivity at sufficiently high frequencies, are discussed in detail. 相似文献
189.
Summary Glass layers of (V2O5)1−x
(P2O5)
x
were prepared by melting appropriate mixtures of V2O5 and P2O5 powders. The measurements ofI–V characteristic curves show three regions of conduction, namely high-resistance state, turnover point with zero-differential
resistance region (∂V/∂I=0) and differential negative-resistance region. The turnover point is strongly dependent on composition, sample thickness
and temperature. It is found that the increase of the ratio of phosphorus/vanadium reduces conductance as well as it raises
the field required to produce turnover behaviour. The data in the range up to the turnover point are discussed on the basis
of an electrothermal process. Results of the negative-resistance state could be explained in terms of a hopping mechanism. 相似文献
190.
Summary The dielectric and electronic properties of thianthren (C6H4(S)2H4C6) are determined by means of optical reflectivity, absorption measurements and reflection electron energy loss spectroscopy.
The experimental results are interpreted on the basis of a Complete Neglect of Differential Overlap (CNDO) calculation used
in three different parametrization schemes. Emphasis is laid on the discussion of the problems which generally affect the
analysis of electron energy loss spectra, and a procedure to obtain the complex dielectric function from electron energy loss
measurements performed in the reflection mode is suggested.
Work partially supported by the MURST through the GNSM. 相似文献