全文获取类型
收费全文 | 132篇 |
免费 | 10篇 |
专业分类
化学 | 100篇 |
晶体学 | 1篇 |
力学 | 4篇 |
数学 | 7篇 |
物理学 | 30篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 3篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 265 毫秒
101.
The extension of pulsed laser deposition to the synthesis on Ti substrates of β-tricalcium phosphate (β-TCP) coatings doped with manganese is reported. Targets sintered from two crystalline Mn-doped β-TCP powders (with the composition Ca2.9Mn0.1(PO4)2 and Ca2.8Mn0.2(PO4)2) were ablated with an UV KrF* (λ = 248 nm, τ ∼ 7 ns) laser source. X-ray diffraction and energy dispersive X-ray spectroscopy investigations showed that the films, while prevalently amorphous, had a Ca/P ratio of about 1.50-1.52. Scanning electron microscopy analyses revealed a rather homogeneous aspect of the coatings which were molded to the relief of the chemically etched Ti substrate. Fluorescence microscopy was applied to test the proliferation of mesenchymal stem cells grown on the obtained biostructures. Our investigations found that, even 14 days after cultivation, the synthesized films were not cytotoxic. On the contrary, they showed excellent bioactivity, as demonstrated by the neat spread of the cells over the entire surface of Mn-doped β-TCP. When tested in osteoprogenitor cell culture, the Ca2.8Mn0.2(PO4)2 samples revealed a higher potential for proliferation and better viability compared with Ca2.9Mn0.1(PO4)2. 相似文献
102.
Em. Cincu I. Manea V. Manu D. Barbos O. Sima I. Gustavsson P. Vermaercke N. Vajda Zs. Molnar H. Polkowska-Motrenko 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):199-205
Samples of high alloy Stainless Steel SS 1 were analyzed by instrumental neutron activation analysis (INAA) at 5 research
institutes in 4 European countries within the frame of an Inter-Laboratory Comparison (ILC) exercise aiming at checking if
the results were independent of the standardization methods, and if INAA was accurate enough to contribute to certification.
The mean element concentration values yielded by INAA were also compared with mean values obtained by atomic emission spectroscopy
techniques at other laboratories that took part in the International Proficiency Testing organized by KIMAB Institute of Sweden,
producer of the SS 1. The performances of the nuclear and atomic techniques were compared in terms of the z-score values calculated for 11 element concentrations evaluated by the two analytical ways. Finally, consideration is given
to the ways in which highest accuracy and precision can be ensured for certifying stainless steels as CRMs. 相似文献
103.
Werner Uhl Frank Breher Sima Haddadpour Rainer Koch Madhat Matar 《无机化学与普通化学杂志》2004,630(12):1839-1845
The dialkylaluminum and dialkylgallium alkynides [R2E‐C≡C‐R′]2 (R = Me, CMe3; E = Al, Ga; R′ = Ph) containing C≡C triple bonds attached to their central aluminum or gallium atoms are easily obtained by the reactions of dialkylelement chlorides with lithium alkynides or by treatment of the corresponding alkyne R‐C≡C‐H with dialkylaluminum or dialkylgallium hydrides. The first reaction is favored by the precipitation of LiCl, the second one by the formation of elemental hydrogen. All products form dimers in which the carbanionic carbon atoms of the alkynido groups adopt bridging positions, but, interestingly, different types of molecular structures were observed depending on the steric demand of the substituents terminally attached to the aluminum or gallium atoms. The small methyl substituents gave structures in which the aluminum or gallium atoms seemed to be side‐on coordinated by the C≡C triple bonds of almost linear E‐C≡C groups. In contrast, the more bulky tert‐butyl groups forced an arrangement in which the C≡C triple bonds were perpendicular to the E‐E axis of the molecules. Different bonding modes result, which were analyzed by quantum‐chemical calculations. 相似文献
104.
Zahra Pezeshki-Nejad Mohammad Almasi-Kashi Sima Alikhanzadeh-Arani Abdolali Ramazani Masoud Salavati-Niasari 《Journal of Cluster Science》2016,27(3):1031-1039
Nanoparticles of Co2FeAl magnetic alloy was successfully fabricated in the presence of a well-known capping agent, polyvinyl alcohol, as a polymer template. The magnetic properties were studied using hysteresis curve and first-order reversal curve (FORC) measurements at room temperature. FORC diagrams demonstrated a wide distribution of the coercive field owing to the presence of different particle sizes in products. TEM image also showed that the synthesized samples are composed of some large clusters containing a few smaller particles. The maximum value of magnetization (~76 emu/g) and coercivity (573 Oe) were obtained in the annealed sample with 5 °C/min. A wider distribution of grain size with a smaller average of 20.5 nm as well as lower-degree of crystallinity was observed in the sample annealed with higher rate of 10 °C/min. 相似文献
105.
O. Sima 《Journal of Radioanalytical and Nuclear Chemistry》2000,244(3):669-673
The GESPECOR software, initially developed for the computation of efficiency of HPGe detectors in environmental -ray spectrometry, was applied to NAA. The software is useful for the computation of efficiency and of self-attenuation and coincidence-summing corrections for common experimental conditions. A new source subroutine was implemented in GESPECOR for solving the more complex case of non-uniform sources. In this way neutron self-shielding in the activation of samples of large volume is taken into account. The dependence of the detection efficiency on the flux distribution is discussed. 相似文献
106.
Entezari Hosein Almasi-Kashi Mohammad Alikhanzadeh-Arani Sima 《Journal of Cluster Science》2022,33(6):2689-2696
Journal of Cluster Science - Three EM wave absorbing (FeNi, CoNi, and FeCo)/ZnS nanocomposites were synthesized by simple and successful process. By comparison, it was demonstrated that the maximum... 相似文献
107.
Sima Sedghiniya Janet Soleimannejad Jan Janczak 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(4):412-421
At one extreme of the proton‐transfer spectrum in cocrystals, proton transfer is absent, whilst at the opposite extreme, in salts, the proton‐transfer process is complete. However, for acid–base pairs with a small ΔpKa (pKa of base ? pKa of acid), prediction of the extent of proton transfer is not possible as there is a continuum between the salt and cocrystal ends. In this context, we attempt to illustrate that in these systems, in addition to ΔpKa, the crystalline environment could change the extent of proton transfer. To this end, two compounds of salicylic acid (SaH) and adenine (Ad) have been prepared. Despite the same small ΔpKa value (≈1.2), different ionization states are found. Both crystals, namely adeninium salicylate monohydrate, C5H6N5+·C7H5O3?·H2O, I , and adeninium salicylate–adenine–salicylic acid–water (1/2/1/2), C5H6N5+·C7H5O3?·2C5H5N5·C7H6O3·2H2O, II , have been characterized by single‐crystal X‐ray diffraction, IR spectroscopy and elemental analysis (C, H and N) techniques. In addition, the intermolecular hydrogen‐bonding interactions of compounds I and II have been investigated and quantified in detail on the basis of Hirshfeld surface analysis and fingerprint plots. Throughout the study, we use crystal engineering, which is based on modifications of the intermolecular interactions, thus offering a more comprehensive screening of the salt–cocrystal continuum in comparison with pure pKa analysis. 相似文献
108.
Poullet JB Sima DM Van Huffel S 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,195(2):134-144
In this paper an overview of time-domain and frequency-domain quantitation methods is given. Advantages and drawbacks of these two families of quantitation methods are discussed. An overview of preprocessing methods, such as lineshape correction methods or unwanted component removal methods, is also given. The choice of the quantitation method depends on the data under investigation and the pursued objectives. 相似文献
109.
Zhibin Jiang Liqiang Sima Lisha Qi Xiaoguang Wang Jie Wang Zhenpeng Leng Tianpeng Zhao 《Molecules (Basel, Switzerland)》2021,26(17)
The penetration and displacement behavior of N2 molecules in porous interlayer structures containing a water/salt component with porosities of 4.29%, 4.73%, 5.17%, 7.22%, and 11.38% were explored using molecular dynamics simulations. The results demonstrated that the large porosity of the interlayer structures effectively enhanced the permeation and diffusion characteristics of N2. The water and salt in the interlayer structures were displaced during the injection of N2 in the porosity sequence of 4.29% < 4.73% < 5.17% < 7.22% < 11.38%. The high permeance of 7.12 × 10−6 indicated that the interlayer structures with a porosity of 11.38% have better movability. The strong interaction of approximately 15 kcal/mol between N2 and H2O had a positive effect on the diffusion of N2 and the displacement of H2O before it reached a stable equilibrium state. The distribution of N2 in porous interlayer structures and the relationship between the logarithm of permeability and breakthrough pressure were presented. This work highlighted the effects of porosity on the permeability and diffusion of N2/H2O in the interlayer, thus providing theoretical guidance for the development of petroleum resources. 相似文献
110.
In this study, we propose an efficient and accurate numerical technique that is called the rational Chebyshev collocation (RCC) method to solve the two dimensional flow of a viscous fluid in the vicinity of a stagnation point named Hiemenz flow. The Navier-Stokes equations governing the flow, are reduced to a third-order ordinary differential equation of a boundary value problem with a semi-infinite domain by using similarity transformation. The rational Chebyshev method reduces this nonlinear ordinary differential equation to a system of algebraic equations. This technique is a powerful type of the collocation methods for solving the boundary value problems over a semi-infinite interval without truncating it to a finite domain. We also present the comparison of this work with others and show that the present method is more accurate and efficient. 相似文献