全文获取类型
收费全文 | 1281篇 |
免费 | 50篇 |
国内免费 | 2篇 |
专业分类
化学 | 1101篇 |
晶体学 | 7篇 |
力学 | 14篇 |
数学 | 73篇 |
物理学 | 138篇 |
出版年
2023年 | 13篇 |
2022年 | 110篇 |
2021年 | 98篇 |
2020年 | 33篇 |
2019年 | 27篇 |
2018年 | 24篇 |
2017年 | 36篇 |
2016年 | 68篇 |
2015年 | 53篇 |
2014年 | 74篇 |
2013年 | 98篇 |
2012年 | 116篇 |
2011年 | 96篇 |
2010年 | 62篇 |
2009年 | 56篇 |
2008年 | 66篇 |
2007年 | 68篇 |
2006年 | 47篇 |
2005年 | 51篇 |
2004年 | 33篇 |
2003年 | 27篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有1333条查询结果,搜索用时 15 毫秒
91.
Piotr Jeleń Magdalena Szumera Magdalena Gawęda Elżbieta Długoń Maciej Sitarz 《Journal of Thermal Analysis and Calorimetry》2017,129(1):103-108
Heat capacity of single-crystal samples of five chalcogenides (LiInS2, LiInSe2, LiGaS2, LiGaSe2, and LiGaTe2) was measured with DSC in a temperature range from 180 to 460 K. The data for LiInS2 and LiInSe2 were compared with the literature data and shown to agree with the results of adiabatic calorimetry (Gmelin and Hönle in Thermochimica Acta 269: 575–590, 1995) better than with other DSC data (Kühn et al. in Cryst Res Technol 22: 265–269, 1987). Besides, the high-temperature fitting polynomial for C P(T) published about 30 years ago for LiInS2 is wrong. LiGaS2, LiGaSe2, and LiGaTe2 were measured for the first time. 相似文献
92.
Magdalena Leśniak Marcin Gajek Janusz Partyka Maciej Sitarz 《Journal of Thermal Analysis and Calorimetry》2017,130(1):165-176
In this work, the structure and thermal properties of aluminosilicate fritted glazes in SiO2–Al2O3–CaO–MgO–Na2O–K2O–ZnO system with (4.0 mol%) and without addition of ZnO were examined by GIXRD, FTIR, MAS-NMR and thermal methods (DTA, DIL). It has been found that the all experimental glazes are amorphous material (transparent glazes). On the base of spectroscopic investigations, it was found that zinc ions exist in the network glazes in the octahedral coordination—Zn2+ ions play a network modifier role in structure of glazes. An analysis of the data obtained from thermal tests showed that addition of ZnO into chemical composition results in decrease in glass transition temperature value (T g) for all glazes (DTA, DIL). The coefficient of thermal expansion (α) is decreased as the whole measurement range for one series of fritted glazes. 相似文献
93.
New thermoplastic segmented polyurethanes were obtained by a one-step melt polyaddition using 40, 50 and 60 mol% poly(hexane-1,6-diyl carbonate) diol of \(\bar{M}_{n} = 860\) g mol?1, 1,1′-methanediylbis(4-isocyanatobenzene) and 2,2′-[sulfanediylbis(benzene-1,4-diyloxy)]diethanol, 2,2′-[oxybis(benzene-1,4-diylsulfanediyl)]diethanol or 2,2′-[sulfanediylbis(benzene-1,4-diylsulfanediyl)]diethanol as a chain extender. FTIR, atomic force microscopy, differential scanning calorimetry and thermogravimetry were used to examine the polyurethanes’ structure and thermal properties. Moreover, their Shore A/D hardness, tensile, adhesive and optical attributes were determined. They were transparent high-molar-mass materials showing good tensile strength (up to 51.9 MPa). The polyurethanes exhibited improved adhesion to copper taking into consideration that of conventional ones, and middle or high refractive index values (1.57–1.60), and both these parameters increased with an increase of the content of sulfur atoms in the polyurethane chain. The newly obtained polyurethanes can be considered as materials for numerous medical and optical appliances. 相似文献
94.
Agata Górska Karolina Szulc Ewa Ostrowska-Ligęza Joanna Bryś Magdalena Wirkowska-Wojdyła 《Journal of Thermal Analysis and Calorimetry》2017,128(1):177-183
Epoxy-based nanocomposites containing different concentrations (0–3%) of surface-modified graphene nanosheets (GNS) with 3-aminopropyltriethoxysilane were prepared and their thermal and mechanical properties including dynamic mechanical analysis, tensile strength, hardness, and abrasion tests were evaluated in order to have a database for thermo-mechanical properties of epoxy nanocomposites. The main aim of this study was to understand the optimum percentage of GNS which would perform the best reinforcing influence on mechanical and physical performance of an epoxy nanocomposite. The results explain how applying the analysis of variance (ANOVA) method as a useful tool in optimization of GNS concentration in preparation of high-performance epoxy-based nanocomposites. 相似文献
95.
Magdalena Graczyk-Zajac Maximilian Wimmer Yeping Xu Gerd Buntkowsky Christian Neumann Ralf Riedel 《Journal of Solid State Electrochemistry》2017,21(1):47-55
Within this work, we analyze the lithium storage sites within carbon/silicon carbonitride (SiCN) composites. Commercial carbons, HD3 (hard carbon) and LD1N and LD2N (soft carbons), of varying porosity are impregnated with polysilazane (HTT 1800) and pyrolysed at 1100 °C. It is found in the first part of this study (Graczyk-Zajac et al. J Solid State Electrochem 19:2763–2769, 2015) that the initial porosity of the carbon phase plays an important role in determining the lithium insertion capacity and rate capability of the composite material. By applying Raman spectroscopy and solid-state 7Li MAS NMR on pristine, lithiated, and delithiated samples, we investigate the lithium storage sites within the composite materials. By means of Raman spectroscopy, it has been found that lithium storage in hard carbon-derived composites occurs in a significant extent via adsorption-like process within unorganized carbon, whereas for the soft carbon composites, storage in turbostratic carbon is identified. 7Li solid-state NMR confirms these findings revealing that more than 33 % of lithium stored in HD3/SiCN is adsorbed in ionic form at the surface and in pores of the composite, while around 38 % is stored between carbon layers. LD1N and LD2N composites store more than 50 % of lithium in the intercalation-type sites. 相似文献
96.
Dr. Minh T. Nguyen Dr. Matthew D. Krzyaniak Dr. Magdalena Owczarek Dr. Daniel P. Ferris Prof. Michael R. Wasielewski Prof. J. Fraser Stoddart 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5889-5894
We report the synthesis of a tetracationic macrocycle which contains two N,N′-bis(methylene)naphthalenediimide units inserted in between the pyridinium rings of the bipyridinium units in cyclobis(paraquat-p-phenylene) (CBPQT4+ or “blue box”) and describe the investigation of its potential use in materials for organic electronics. The incorporation of the two naphthalenediimide (NDI) units into the constitution of CBPQT4+, not only changes the supramolecular properties of the tetracation in the solid state, but also has a profound influence on the electrochemical and electronic behavior of the resulting tetracationic macrocycle. In particular, the solid-state (super)structure, investigated by single-crystal X-ray diffraction, reveals the formation of a three-dimensional (3D) supramolecular framework with ca. 2.8 nm diameter one-dimensional (1D) hexagonal channels. Electrochemical studies on solid-state thin films of the macrocycle show that they exhibit semiconducting properties with a redox-conductivity of up to 7.6×10−4 S m−1. Moreover, EPR and ENDOR spectroscopies show that charge is equally shared between the NDIs within the one-electron reduced state of the NDI-based macrocycle on the time scale of these techniques. 相似文献
97.
Dental calculus analysis can be a valuable source of archaeological knowledge, since it preserves not only microbial and host biomolecules but also dietary and environmental debris, as well as metabolic products likely originating from dietary and craft activities. Here we described GC-MS analysis of a set of historic dental calculus samples from the front teeth of the mandibles of seven individuals found in 17th- and 18th-century graves in the city of Rzeszow, located in South-eastern Poland. We have found that only saturated fatty acids, which are characteristic for fats of animal origin, were present in the tested samples. Our preliminary results indicate that the diet of modern-period inhabitants of Rzeszow was rich in animal products, such as meat and dairy products. 相似文献
98.
Anna Pawlik Magdalena Jarosz Robert P. Socha Grzegorz D. Sulka 《Molecules (Basel, Switzerland)》2021,26(6)
In implantable materials, surface topography and chemistry are the most important in the effective osseointegration and interaction with drug molecules. Therefore, structural and surface modifications of nanostructured titanium dioxide (TiO2) layers are reported in the present work. In particular, the modification of annealed TiO2 samples with —OH groups and silane derivatives, confirmed by X-ray photoelectron spectroscopy, is shown. Moreover, the ibuprofen release process was studied regarding the desorption-desorption-diffusion (DDD) kinetic model. The results proved that the most significant impact on the release profile is annealing, and further surface modifications did not change its kinetics. Additionally, the cell adhesion and proliferation were examined based on the MTS test and immunofluorescent staining. The obtained data showed that the proposed changes in the surface chemistry enhance the samples’ hydrophilicity. Moreover, improvements in the adhesion and proliferation of the MG-63 cells were observed. 相似文献
99.
100.
David Ramírez Melissa Mejia-Gutierrez Braulio Insuasty Susanne Rinn Aytug K. Kiper Magdalena Platzk Thomas Müller Niels Decher Jairo Quiroga Pedro De-la-Torre Wendy Gonzlez 《Molecules (Basel, Switzerland)》2021,26(13)
TASK channels belong to the two-pore-domain potassium (K2P) channels subfamily. These channels modulate cellular excitability, input resistance, and response to synaptic stimulation. TASK-channel inhibition led to membrane depolarization. TASK-3 is expressed in different cancer cell types and neurons. Thus, the discovery of novel TASK-3 inhibitors makes these bioactive compounds very appealing to explore new cancer and neurological therapies. TASK-3 channel blockers are very limited to date, and only a few heterofused compounds have been reported in the literature. In this article, we combined a pharmacophore hypothesis with molecular docking to address for the first time the rational design, synthesis, and evaluation of 5-(indol-2-yl)pyrazolo[3,4-b]pyridines as a novel family of human TASK-3 channel blockers. Representative compounds of the synthesized library were assessed against TASK-3 using Fluorometric imaging plate reader—Membrane Potential assay (FMP). Inhibitory properties were validated using two-electrode voltage-clamp (TEVC) methods. We identified one active hit compound (MM-3b) with our systematic pipeline, exhibiting an IC50 ≈ 30 μM. Molecular docking models suggest that compound MM-3b binds to TASK-3 at the bottom of the selectivity filter in the central cavity, similar to other described TASK-3 blockers such as A1899 and PK-THPP. Our in silico and experimental studies provide a new tool to predict and design novel TASK-3 channel blockers. 相似文献