全文获取类型
收费全文 | 558篇 |
免费 | 27篇 |
国内免费 | 2篇 |
专业分类
化学 | 386篇 |
晶体学 | 12篇 |
力学 | 16篇 |
数学 | 55篇 |
物理学 | 118篇 |
出版年
2024年 | 2篇 |
2022年 | 21篇 |
2021年 | 25篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 38篇 |
2012年 | 22篇 |
2011年 | 47篇 |
2010年 | 24篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 36篇 |
2006年 | 24篇 |
2005年 | 36篇 |
2004年 | 16篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有587条查询结果,搜索用时 15 毫秒
101.
Suneela Arif Iftikhar Ahmad Bin Amin 《International journal of quantum chemistry》2012,112(3):882-888
Results of Co and Ni substituted AlN in the zinc blende phase are presented. For spin up states, the hybridized N‐2p and Co/Ni‐3d states form the valance bands with a bandgap around the Fermi level for both materials, while in the case of the spin down states, the hybridized states cross the Fermi level and hence show metallic nature. It is found that, Al0.75Co0.25N and Al0.75Ni0.25N are ferromagnetic materials with magnetic moments of 4 μB and 3 μB, respectively. The integer magnetic moments and the full spin polarization at the Fermi level make these compounds half‐metallic semiconductors. Furthermore it is also found that the interaction with the N‐2p state splits the 5‐fold degenerate Co/Ni‐3d states into t2g and eg states. The t2g states are located at higher energies than the eg states caused by the tetrahedral symmetry of these compounds. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
102.
James K. Harper Atta M. Arif David M. Grant 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):451-452
cis‐Verbenol (alternative name: 4,6,6‐trimethylbicyclo[3.1.1]hept‐3‐en‐2‐ol), C10H16O, forms an orthorhombic P212121 crystal that contains three molecules per asymmetric unit. These three molecules form hydrogen‐bonded helices parallel to the shortest axis of the lattice. The O?O distances associated with the hydrogen bonds are 2.760 (3), 2.760 (3) and 2.766 (3) Å. 相似文献
103.
The laser short pulse heating initiates nonequilibrium heating of the substrate material, which in turn results in the thermal stresses developing in the region below the surface. The surface temperature can be measured possibly through the monitoring of the resulting surface displacement. This requires in detail investigation into the surface displacement and surface temperature rises across the heated spot during the laser short pulse heating process. In the present study, the laser short pulse heating of gold surface is considered and the temperature rise at the surface and elastic displacement of the surface are investigated. The spatial and temporal distributions of surface displacement and surface temperature are predicted and the elastic response of the substrate material due to temperature rise is explored. It is found that the temporal and spatial distributions of the surface displacement do not follow the temperature rise at the surface. Consequently, care should be taken when measuring the temperature rise at the surface by means of monitoring the surface displacement during a laser short pulse heating process. 相似文献
104.
Wafa Arif Nosheen Fatima Rana Iqra Saleem Tahreem Tanweer Muhammad Jawad Khan Sohad Abdulkaleg Alshareef Huda M. Sheikh Fatima S. Alaryani Manal Othman AL-Kattan Hanan Ali Alatawi Farid Menaa Aroosa Younis Nadeem 《Molecules (Basel, Switzerland)》2022,27(21)
Resin composites have been widely used in dental restoration. However, polymerization shrinkage and resultant bacterial microleakage are major limitations that may lead to secondary caries. To overcome this, a new type of antibacterial resin composite containing ciprofloxacin-loaded silver nanoparticles (CIP-AgNPs) were synthesized. The chemical reduction approach successfully produced CIP-AgNPs, as demonstrated by FTIR, zeta potential, scanning electron microscopy, and ultraviolet-visible (UV-vis) spectroscopy. CIP-AgNPs were added to resin composites and the antibacterial activity of the dental composite discs were realized against Enterococcus faecalis, Streptococcus mutans, and the Saliva microcosm. The biocompatibility of modified resin composites was assessed and mechanical testing of modified dental composites was also performed. The results indicated that the antibacterial activity and compressive strength of resin composites containing CIP-AgNPs were enhanced compared to the control group. They were also biocompatible when compared to resin composites containing AgNPs. In short, these results established strong ground application for CIP-AgNP-modified dental composite resins. 相似文献
105.
Muhammad Ahsan Iqbal Xiaoliang Weng Chenxu Kang Nayab Arif Kewen Wu Wei Tang Sichao Dai Xueqian Fang Houzhi Cai Yu-Jia Zeng 《Laser \u0026amp; Photonics Reviews》2024,18(2):2300612
Photoinduced charge-trapping is a promising strategy for boosting the photosensitivity of organic photodetectors at the expense of their response time. In addition, they have a low carrier extraction yield due to the formation of low-energy triplet excitons through the recombination of a photogenerated hole–electron pair. Materials with thermally activated delayed fluorescence (TADF) exhibit a long-lived (≈µs) excited spin-triplet nearly iso-energetically aligned with that of an excited spin-singlet, which results in suppressed exciton losses and is widely used in organic light-emitting diodes. The extraction and population of triplet state excitons in TADFs is a sought-after but underexplored aspect of photoinduced gating in photodetectors. A 1,2,3,5-tetrakis(carbazol-9-yl)4,6-Dicyanobenzene (4CzIPN) TADF blend with a high-mobility Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) polymer via bulk type-II offset can increase free carrier extraction yield (fast response) and retain trapped electrons in TADF triplet states (high gain). The PBTTT-C14/4CzIPN ultraviolet photodetector device maintains a trade-off between high photogain (≈103) and fast response time (79 ms) at 300 nm while operating at a shallow dark current (≈pA). Furthermore, the device shows high external quantum efficiency (≈104 %) and detectivity (≈1011 Jones) for low light power (<pW). The innovative application of TADF material can lead to exciting new developments in organic-based high-performance photodetection. 相似文献
106.
Arif Uzma Nawaz M. Alharbi Sayer Obaid Saleem S. 《Journal of Thermal Analysis and Calorimetry》2021,144(3):729-737
Journal of Thermal Analysis and Calorimetry - This article explores the role of hybrid nano-particles in enhancing the thermal performance of Sutterby fluid over a two-dimensional body of variable... 相似文献
107.
Arif Rafiq Nazir Ahmad Mir Farooq Ahmad .Mathematics Department COMSATS Institute of Information Technology Islamabad Pakistan .Centre for Advanced Studies in Pure Applied Mathematics Bahauddin Zakariya University Multan Pakistan 《应用数学和力学(英文版)》2007,(7)
In account of the famous ebyev inequality,a rich theory has appeared in the literature.We establish some new weighted ebyev type integral inequalitíes.Our proofs are of independent interest and provide new estimates on these types of inequalities. 相似文献
108.
S. Pervez A. Mushtaq N. Arif Z. H. Chohan 《Journal of Radioanalytical and Nuclear Chemistry》2003,257(2):417-420
Bone seeking radiopharmaceuticals such as ethylenediaminetetramethylene phosphonate (EDTMP) complexes of 153Sm and 166Ho are receiving considerable attention for therapeutic treatment of bone metastases. Rhenium-188 has both beta-particle emissions for a therapeutic effect and gamma-emissions for imaging and it is available from an in-house generator system similar to the current 99mTc generator, which makes it convenient for clinical use. The preparation of 188Re-EDTMP is described using 188Re, which was obtained from the alumina-based 188W/188Re generator. Dependence of the radiolabeling yield of 188Re-EDTMP on reducing agent concentration, EDTMP concentration, incubation time, pH and addition of carrier was examined. In the case of optimum conditions, the radiolabeling yields of 188Re-EDTMP were ~98% for carrier-free as well as carrier-added 188Re. The addition of ascorbic acid plays an important role in the stability of carrier-free as well as carrier-added 188Re-EDTMP preparations. The biodistribution of carrier-free and carrier-added 188Re-EDTMP compounds in rats was also studied. The results show that 188Re (carrier-added)-EDTMP is a potential bone pain palliation radiopharmaceutical due to its high skeletal uptake, rapid blood clearance and relatively low soft tissue absorption. 相似文献
109.
M. Arshad A. H. Qureshi K. Masud N. K. Qazi 《Journal of Thermal Analysis and Calorimetry》2007,89(2):595-600
The production of bulk high T
c superconducting phase (2223) by EDTA-gel (ethylenediaminetetraacetic acid) techniques has been investigated. It is shown
that close control of pH is necessary for the production of a well-complexed precursor which allows subsequent decomposition
in two stages at 300 and 800°C. The problem of carbonate formation was investigated experimentally and solved. Precursors
are characterised by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) and the sintering behaviour
was monitored by dilatometry. At least three different phases Bi2Sr2Cax−1CuxO8+y (BSCCO); where x=1, 2, 3 were identified within superconducting pellets using XRD, named as Bi2Sr2CuO7 (2201), Bi2Sr2CaCu2O9 (2212) and Bi2Sr2Ca3O10 (2223). The superconducting properties of the sintered samples were studied by vibrating sample magnetometer (VSM). Transition
to a superconducting state around 80 K appeared in samples (sintered at 845°C) containing the Bi2Sr2Ca1Cu2Oy (2212) phase. Liquid phase sintering of the samples aided the formation of Bi2Sr2Ca2Cu3Ox (2223) phase at high temperature (860°C), which showed a superconducting transition temperature of 108 K. 相似文献
110.
Zekeriyya Bahadır Volkan Numan Bulut Arif Mermer Neslihan Demirbaş Celal Duran Mustafa Soylak 《Journal of the Iranian Chemical Society》2018,15(6):1347-1354
A selective separation and preconcentration method for the determination of gold ions in water and ore samples has been developed using dispersive liquid–liquid microextraction, followed by flame atomic absorption spectrometry. 4-Ethyl-1(2-(4-(4-nitrophenyl)piperazin-1-yl)acetyl)thiosemicarbazide) (NPPTSC) has been used for the first time as new chelating reagent. A mixture of ethanol (dispersive solvent) and carbon tetrachloride (extraction solvent) was used. Some parameters affecting the extraction procedure including the type and volume of the extracting and dispersive solvents, HNO3 concentration, the chelating agent amount, volume of sample, and foreign ions have optimized. Also, the complex formation between gold ions and the ligand has been investigated in a methanol–water solution (1:1) using UV–visible spectrometry. The spectrophotometric titration data showed that of Au–NPPTSC complex composition was found to be 3:2. After optimizing the instrumental and experimental parameters, we achieved a detection limit of 1.5 µg L?1, a preconcentration factor of 50, and a linear dynamic range of 10.0–400.0 µg L?1. The relative standard deviation obtained 2.1% at 50 µg L?1 for gold ions (n = 10). The proposed method was successfully performed for the determination of gold in certified reference material, environmental water, and ore samples. 相似文献