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111.
L. A. Wasserman M. Signorelli A. Schiraldi V. Yuryev G. Boggini S. Bertini D. Fessas 《Journal of Thermal Analysis and Calorimetry》2007,87(1):153-157
A suitable thermal treatment of gels of various
starch varieties was assessed to achieve the formation of resistant starch
(i.e. amylose crystals). On the basis of DSC data, the yield of amylose crystals
and their thermal stability did not seem correlated with the amylose content
of the starch. This last parameter may not therefore be referred to as the
only factor that defines a resistant starch promising starch variety. 相似文献
112.
Miranda Roesing Jason Howell David Boucher 《Journal of Polymer Science.Polymer Physics》2017,55(14):1075-1087
Solubility data for poly(3‐hexylthiophene) (P3HT) in 29 pure solvents are presented and discussed in detail. Functional solubility parameter (FSP) and convex solubility parameter (CSP) computations are performed and the CSP and FSP results are compared to previously reported Hansen solubility parameters (HSPs) and to the parameters calculated using additive functional group contribution methods. The empirical data reveals experimental solubility parameters with substantial polar (δP) and hydrogen‐bonding (δH) components, which are not intrinsic to the structure of the P3HT polymer. Despite these apparent irregularities, it is shown that the predictor method based on the solubility function, f, does provide a reliable way to quantitatively evaluate the solubility of P3HT in other solvents in terms of a given set of empirical solubility data. The solubility behavior is further investigated using linear solvation energy relationship (LSER) modeling and COSMO‐RS computations of the activity coefficients of P3HT. The LSER model reveals that (1) the cavity term, δT, is the dominant factor governing the solubility behavior of P3HT and (2) the solvent characteristics that dictate the structural order (crystallinity) of P3HT aggregates do not similarly influence the overall solubility behavior of the polymer. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1075–1087 相似文献
113.
Eckert F Leito I Kaljurand I Kütt A Klamt A Diedenhofen M 《Journal of computational chemistry》2009,30(5):799-810
The COSMO-RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for realistic solvation simulations, has been used for the prediction of pK(a) values in acetonitrile. For a variety of 93 organic acids, the directly calculated values of the free energies of dissociation in acetonitrile showed a very good correlation with the pK(a) values (r(2) = 0.97) in acetonitrile, corresponding to a standard deviation of 1.38 pK(a) units. Thus, we have a prediction method for acetonitrile pK(a) with the intercept and the slope as the only adjusted parameters. Furthermore, the pK(a) values of CH acids yielding large anions with delocalized charge can be predicted with a rmse of 1.12 pK(a) units using the theoretical values of slope and intercept resulting in truly ab initio pK(a) prediction. In contrast to our previous findings on aqueous acidity predictions the slope of the experimental pK(a) versus theoretical DeltaG(diss) was found to match the theoretical value 1/RT ln (10) very well. The predictivity of the presented method is general and is not restricted to certain compound classes. However, a systematic correction of -7.5 kcal mol(-1) is required for compounds that do not allow electron-delocalization in the dissociated anion. The prediction model was tested on a diverse test set of 129 complex multifunctional compounds from various sources, reaching a root mean square deviation of 2.10 pK(a) units. 相似文献
114.
115.
Our aim is to describe the behavior of non-linear scattering effects that arise in standard single mode fiber (SMF), specifically scattering effects that propagate optical power in the reverse direction of the source signal such as Rayleigh Scattering (RS) and Brillouin Scattering (BS). For this purpose, the effects of backscattering phenomena over a bidirectional data transmission in a passive optical network (PON) scheme have been assessed. The impact of these high optical power components over reception at the optical line terminal (OLT) side has been determined when both links use the same wavelength. Bit Error Rate (BER) measurements have been performed with different transmission rates, using several techniques to mitigate the influence of backscattering over the received signal and considering cases with filtered and unfiltered BS. 相似文献
116.
One phase transition in [Zn(NH3)4](ReO4)2 at Tc = 393.5 K (on heating) and 392.0 K (on cooling) was found. Thermal stability of this compound was investigated by thermal analysis methods. It decomposes in three main stages. The first two are connected with deamination process, whereas Re2O7 evaporates in the last step. The activation energy for NH3 loss processes was determined from thermogravimetric (TG) measurements. The vibrational and reorientational dynamics of NH3 ligands in the low-temperature phase was probed by various complementary techniques. It was found that at temperatures close to 150 K, NH⋯O hydrogen bond is formed. Temperature-dependent band shape analysis of properly chosen infrared (IR) band was performed, whose results showed that activation energy for NH3 reorientational motion (<300 K) is rather small and is approximately equal to 2 kJ mol−1. Neutron and X-ray powder diffraction patterns did not reveal any drastic change in the crystal structure in a wide temperature range. 相似文献
117.
Joanna Hetmaczyk ukasz Hetmaczyk Anna Migda‐Mikuli Edward Mikuli 《Journal of Raman spectroscopy : JRS》2016,47(5):591-601
[Ca(H2O)6]Cl2 between 93 and 300 K possesses two solid phases. One phase transition (PT) of the first‐order type at = 218.0 K (on heating) and = 208.0 K (on cooling) was determined by differential scanning calorimetry. Thermal hysteresis of this PT (10 K), as well as the heat flow anomaly sharpness, suggests that the detected PT is a first‐order one. The entropy change value [ΔS ≈ 8.5 J mol−1 K−1 ≈ Rln(2.8)] associated with the observed PT suggests a moderate degree of molecular dynamical disorder of the high‐temperature phase. The temperature dependencies of the full width at half maximum values of the infrared band are due to ρ(H2O)A2 mode (at 205 cm−1), and two Raman bands are arising from τ(H2O)E and τ(H2O)A1 modes (at ca. 410 and 682 cm−1, respectively), suggesting that the observed PT is associated with a sudden change of speed of the H2O reorientational motions. The estimated mean value of activation energy for the reorientation of the H2O ligands in the high‐temperature phase is ca. 11.4 kJ mol−1 from Raman spectroscopy and 11.9 kJ mol−1 from infrared spectroscopy. X‐ray single‐crystal diffraction measurement and spectroscopic studies (infrared, Raman and inelastic neutron scattering) also confirm that [Ca(H2O)6]Cl2 includes two sets of differently bonded H2O molecules. Ab initio calculations of the complete unit cell of one molecule of calcium chloride with a different number of water molecules (2, 4 and 6) have also been carried out. A comparison of Fourier Transform Infrared (FT‐IR), Fourier Transform Raman Scattering (FT‐RS) and inelastic neutron scattering spectroscopies results with periodic density functional theory calculations was used to provide a complete assignment of the vibrational spectra of [Ca(H2O)6]Cl2. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
118.
介绍了一种基于RS422数字接口的PCI总线的单通道数字视频采集系统,可实现30帧/s的1024×1024像元10bit的数字视频采集。系统的核心技术是利用高速数据采集卡进行实时数字图像信号采集,并持续的将采集来的信号数据记录到计算机硬盘上。采集部分可用于PCI总线的视频系统或独立的视频设备中。 相似文献
119.
任骏原 《浙江大学学报(理学版)》2011,38(2):177-181
提出555时基电路的输出信号与输入信号之间具有时序特征.根据反映时序特征的状态转换图及单稳态触发器的工作特点,系统地研究了555单稳态触发器的设计方法,分析了外加触发信号的输入方式、电平幅度、持续时间要求、RC电路定时单元的接法及电容的充放电过程,并发现了一些新的设计方案.Multisim仿真及实际硬件验证证明了所提出设计方案的正确性. 相似文献
120.
任骏原 《浙江大学学报(理学版)》2010,37(4):425-427
分析了JK触发器的激励函数和次态函数的关系并在卡诺图上建立二者的联系,提出了在触发器的次态卡诺图上直接求解最小化J、K激励函数的方法,讨论了无效状态的赋值问题及自启动设计方法,对简化时序逻辑电路的设计过程具有实用意义. 相似文献