全文获取类型
| 收费全文 | 612篇 |
| 免费 | 15篇 |
| 国内免费 | 1篇 |
专业分类
| 化学 | 377篇 |
| 晶体学 | 13篇 |
| 力学 | 14篇 |
| 综合类 | 1篇 |
| 数学 | 88篇 |
| 物理学 | 135篇 |
出版年
| 2024年 | 22篇 |
| 2023年 | 9篇 |
| 2022年 | 32篇 |
| 2021年 | 42篇 |
| 2020年 | 24篇 |
| 2019年 | 33篇 |
| 2018年 | 13篇 |
| 2017年 | 25篇 |
| 2016年 | 33篇 |
| 2015年 | 26篇 |
| 2014年 | 33篇 |
| 2013年 | 42篇 |
| 2012年 | 34篇 |
| 2011年 | 27篇 |
| 2010年 | 26篇 |
| 2009年 | 26篇 |
| 2008年 | 18篇 |
| 2007年 | 24篇 |
| 2006年 | 25篇 |
| 2005年 | 12篇 |
| 2004年 | 9篇 |
| 2003年 | 7篇 |
| 2002年 | 5篇 |
| 2001年 | 9篇 |
| 2000年 | 6篇 |
| 1999年 | 1篇 |
| 1998年 | 2篇 |
| 1996年 | 3篇 |
| 1995年 | 4篇 |
| 1994年 | 6篇 |
| 1993年 | 3篇 |
| 1992年 | 3篇 |
| 1991年 | 1篇 |
| 1990年 | 2篇 |
| 1989年 | 3篇 |
| 1988年 | 3篇 |
| 1987年 | 2篇 |
| 1986年 | 1篇 |
| 1985年 | 2篇 |
| 1984年 | 4篇 |
| 1983年 | 2篇 |
| 1982年 | 5篇 |
| 1981年 | 5篇 |
| 1980年 | 1篇 |
| 1977年 | 1篇 |
| 1975年 | 3篇 |
| 1974年 | 3篇 |
| 1973年 | 4篇 |
| 1970年 | 1篇 |
| 1966年 | 1篇 |
排序方式： 共有628条查询结果，搜索用时 15 毫秒
71.
72.
J. Bashir N. M. Butt M. Nasir Khan Q. H. Khan B. Zhang J. Yang Y. Ding C. Ye 《Journal of Applied Crystallography》1992,25(6):797-799
The Debye–Waller factor of molybdenum has been determined by the powder neutron diffraction technique with a double-axis neutron diffractometer. The B value after correction for thermal diffuse scattering (TDS) was 0.25 (1) Å2, which corresponds to a Debye temperature Θ of 385 (7) K. These values are in good agreement with the values determined by others using X-ray diffraction and inelastic neutron scattering techniques. 相似文献
73.
The starane herbicide was spectrophotometrically determined by the diazotization method in a flow injection assembly. Since starane is a substituted pyridyl compound the NH2 group at the p-position was exploited for diazotization. Starane was diazotized with nitrite and the diazotized product is coupled with beta-naphthol. The absorbance of the resulting azo dye was measured at 395 nm with a molar absorptivity of 1.5 x 10(4) L mol(-1) cm(-1). The calibration graph was linear over the range of 0.6 to 10 microg/mL, with a relative standard deviation (RSD) of 1.67% and a sampling through put of 60 samples h(-1). The % recovery for the determination of starane was found to be 96%. The method was successfully applied to the determination of the active ingredient of starane herbicide in its formulation as well as in food samples. 相似文献
74.
Dapeng Liu Binod R. Giri Milán Szőri Béla Viskolcz Et-touhami Es-sebbar Aamir Farooq 《Proceedings of the Combustion Institute》2021,38(1):967-976
NOx mitigation is a central focus of combustion technologies with increasingly stringent emission regulations. NOx can also enhance the autoignition of hydrocarbon fuels and can promote soot oxidation. The reaction between allyl radical (C3H5) and NOx plays an important role in the oxidation kinetics of propene. In this work, we measured the absolute rate coefficients for the redox reaction between C3H5 and NOx over the temperature range of 1000–1252 K and pressure range of 1.5–5.0 bar using a shock tube and UV laser absorption technique. We produced C3H5 by shock heating of C3H5I behind reflected shock waves. Using a Ti:Sapphire laser system with frequency quadrupling, we monitored the kinetics of C3H5 at 220 nm. Unlike low-temperature chemistry, the two target reactions, C3H5 + NO → products (R1) and C3H5 + NO2 → products (R2), exhibited a strong positive temperature dependence for this radical-radical type reaction. However, these reactions did not show any pressure dependence over the pressure range of 1.5–5.0 bar, indicating that the measured rate coefficients are close to the high-pressure limit. The measured values of the rate coefficients resulted in the following Arrhenius expressions (in unit of cm3/molecule/s):To our knowledge, these are the first high-temperature measurements of allyl + NOx reactions. The reported data will be highly useful in understanding the interaction of NOx with resonantly stabilized radicals as well as the mutual sensitization effect of NOx on hydrocarbon fuels. 相似文献
75.
Umer Farooq;Muhammad Irfan;Shaheer Khalid;Ahmed Jan;Muzamil Hussain; 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2024,104(4):e202300401
Nanofluids significantly influence modern life due to their vast usages in the modern era. Transport analysis of non-Newtonian fluids with nanoparticles (carbon nanotubes) over a stretching surface is the primary focus of the present investigation. Effects of viscous dissipation, porous medium, magnetic field, and heat source factors are also examined. Boundary layers approximation is used to simulate the underlying collection of partial differential equations (PDEs) that regulate the system. Using non-similarity transformation, the basic PDEs of the model are converted into dimensionless nonlinear PDEs. Up to the second level of truncation PDEs that can be treated as ordinary differential equations (ODEs) are generated from dimensionless PDEs utilizing local non-similarity approach. The resultant nonlinear differential equations are computationally solved using bvp4c code of MATLAB technique. In this study, we compile and compare the obtained findings with previous research. Graphs demonstrate how the velocity and temperature profiles depend entirely on a wide range of physical parameters. A rise in the second-grade fluid parameter upsurges the velocity distribution, while an increment in porosity and magnetic parameter declines the velocity distribution. As magnetic values, Eckert number, porosity parameter, and heat source increase, so does the temperature profile of the nanofluid. 相似文献
76.
77.
Mehwish Nawaz Haji Muhammad Shoaib Khan Naveed Akhtar Talha Jamshed Rubina Qaiser Hina Shoukat Mehrin Farooq 《Photochemistry and photobiology》2019,95(5):1243-1248
Solar radiations trigger the physiological alteration in skin which progress toward photoaging. Sunscreens are known to be effective against the photodamaging effects of sunlight. The purpose of this study was to evaluate the extent to which aging signs caused by real‐life sunlight exposure could be avoided by comparing various parameters between sun‐exposed and sun‐protected skin using noninvasive probes. Female volunteers (n = 11) after getting their consent were provided with marketed sunscreen product to apply onto their skin for 6 months. Measurements were scheduled every 15 days from the baseline reading for 6 months. Cutometer, Mexameter and Corneometer were used for evaluation of facial skin parameters. Clinical evaluations showed the effects of sunlight exposure on different skin parameters by comparing sun‐protected and unprotected skin, where Gross elasticity (R2), Net elasticity (R5), Viscoelasticity (R6) and Biological elasticity (R7) showed insignificant results, while Hydration, Melanin and Erythema showed significant results. Sun‐exposed skin presented 0.72%, 0.66%, 0.77%, 1.39%, 1.99%, 2.01% and 3.15% changes in R2, R5, R6 and R7, melanin, erythema and hydration, respectively, which were potentially prevented by sunscreen application. Premature aging is inhibited by following photoprotective regimen on routine basis, emphasizing the potential benefit of sunscreen against early aging signs. 相似文献
78.
Saddam Saqib Wajid Zaman Fazal Ullah Imran Majeed Asma Ayaz Muhammad Farooq Hussain Munis 《应用有机金属化学》2019,33(11)
The ever‐increasing resistance of plant microbes towards fungicides and bactericides has been causing serious threat to plant production in recent years. For the development of an effective antifungal agent, we introduce a novel hydrothermal protocol for synthesis of chitosan iron oxide nanoparticles (CH‐Fe2O3 NPs) using acetate buffer of low pH 5.0 for intermolecular interaction of Fe2O3 NPs and CH. The composite structure and elemental elucidation were carried out by using X‐ray power diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray (EDX), Transmission Electron Microscopy (TEM), Fourier Transformed Infrared Spectroscopy (FTIR) and Ultraviolet Visible Absorption Spectroscopy (UV–vis spectroscopy). Additionally, antifungal activity was evaluated both In vitro and In vivo against Rhizopus oryzae which is causing fruit rot disease of strawberry. We compared different concentrations (0.25%, 0.50%, 075% and 1%) of CH‐Fe2O3 NPs and 50% synthetic fungicide (Matalyxal Mancozab) to figure out suitable concentration for application in the field. XRD analysis showed a high crystalline nature of the NPs with average size of 52 nanometer (nm). SEM images revealed spherical shape with size range of 50–70 nm, whereas, TEM also revealed spherical shape, size ranging from 0 nm to 80 nm. EDX and FTIR results revealed presence of CH on surface of Fe2O3 NPs. The band gap measurement showed peak 317–318 nm for bare Fe2O3 NPs and CH‐Fe2O3 NPs respectively. Antifungal activity in both In vitro and In vivo significantly increased with increase in concentration. The overall results revealed high synergetic antifungal potential of organometallic CH‐Fe2O3 NPs against Rhizopus oryzae and suggest the use of CH‐Fe2O3 NPs against other Phyto‐pathological diseases due to biodegradable nature. 相似文献
79.
Shamsul Qamar Seemab Bashir Sadia Perveen Andreas Seidel-Morgenstern 《液相色谱法及相关技术杂志》2019,42(1-2):16-30
This article presents analytical solutions of the general rate model (GRM), the lumped kinetic model (LKM), and the simpler equilibrium dispersive model (EDM) for core-shell particles and linear adsorption isotherms. The solutions in the Laplace domain are applied to derive analytical expressions for the temporal moments of these models. The results provide relations between the model specific kinetic parameters by matching one or more of the temporal moments. Several case studies are considered for illustration. The results show that simpler models are in many cases as good as the most detailed GRM if their kinetic parameters fulfill the matching relations. Thus, it is possible to reliably predict elution profiles using the simpler models. The derived analytical expressions can also be utilized to efficiently estimate model parameters from experimentally observed elution profiles to further optimize core-shell particles and to identify suitable column sizes and operating conditions. 相似文献
80.
Recently it was proved in [9] that the nonlinear Schrödinger equation fails to predict accurately the dynamics of an original system because of unstable resonances. By extending the ideas in [9], we prove a similar result for the Four Wave Interaction System. 相似文献