全文获取类型
收费全文 | 338篇 |
免费 | 7篇 |
国内免费 | 3篇 |
专业分类
化学 | 149篇 |
晶体学 | 3篇 |
力学 | 12篇 |
数学 | 21篇 |
物理学 | 163篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 8篇 |
2014年 | 14篇 |
2013年 | 26篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 17篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 1篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1998年 | 6篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 14篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有348条查询结果,搜索用时 15 毫秒
321.
Monte Carlo calculations have been performed using MCNP code to study the optimization of photo-neutron yield for different
electron beam energies impinging on Pb, W and Ta cylindrical targets of varying thickness. It is noticed that photo-neutron
yield can be increased for electron beam energies ≥100 MeV for appropriate thickness of the target. It is also noticed that
it can be maximized by further increasing the thickness of the target. Further, at higher electron beam energy heat gradient
in the target decreases, which facilitates easier heat removal from the target. This can help in developing a photoneutron
source based on electron LINAC by choosing appropriate electron beam energy and target thickness to optimize the neutron flux
for ADS, transmutation studies and as high energy neutron source etc. Photo-neutron yield for different targets, optimum target
thickness and photo-neutron energy spectrum and heat deposition by electron beam for different incident energy is presented.
相似文献
322.
Soni Mehul N. Kumar Sivakumar Prasanth Johar SR Kaid Pandya Himanshu A. 《Structural chemistry》2019,30(4):1323-1334
Structural Chemistry - Rheumatoid arthritis (RA) is an autoimmune disorder that causes chronic inflammation with periodic bursts of activity in multiple synovial joints which lead to irreversible... 相似文献
323.
Shaikh SR Cherezov V Caffrey M Soni SP LoCascio D Stillwell W Wassall SR 《Journal of the American Chemical Society》2006,128(16):5375-5383
The major mammalian plasma membrane lipids are phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and cholesterol. Whereas PC-cholesterol interactions are well studied, far less is known about those between PE and cholesterol. Here, we investigated the molecular organization of cholesterol in PEs that vary in their degree of acyl chain unsaturation. For heteroacid sn-1 saturated (palmitoyl), sn-2 unsaturated (various acyl chain) PEs, cholesterol solubility determined by X-ray diffraction was essentially identical with 1 (oleoyl, 51 +/- 3 mol %) and 2 (linoleoyl, 49 +/- 2 mol %) double bonds before decreasing progressively with 4 (arachidonyl, 41 +/- 3 mol %) and 6 (docosahexaenoyl, 31 +/- 3 mol %) double bonds. With 6 double bonds in each chain, cholesterol solubility was further reduced to 8.5 +/- 1 mol %. However, (2)H NMR experiments established that the orientation of cholesterol in the same heteroacid PE membranes was unaffected by the degree of acyl chain unsaturation. A tilt angle of 15 +/- 1 degrees was measured when equimolar [3alpha-(2)H(1)]cholesterol was added, regardless of the number of double bonds in the sn-2 chain. The finding that solubility of cholesterol in sn-1 saturated PEs depends on the amount of polyunsaturation in the sn-2 chain of PE differs from the equivalent PCs that universally incorporate approximately 50 mol % sterol. Unlike PCs, a differential in affinity for cholesterol and tendency to drive lateral segregation is inferred between polyunsaturated PEs. This distinction may have biological implications reflected by the health benefits of dietary polyunsaturated fatty acids that are often taken up into PE > PC. 相似文献
324.
Shahrouz Aliabadi Christopher Bigler Erdal Yilmaz Sridhar Palle Bela Soni 《International Journal of Computational Fluid Dynamics》2013,27(4):175-189
An implicit hybrid finite element (FE)/volume solver has been extended to incompressible flows coupled with the energy equation. The solver is based on the segregated pressure correction or projection method on staggered unstructured hybrid meshes. An intermediate velocity field is first obtained by solving the momentum equations with the matrix-free implicit cell-centred finite volume (FV) method. The pressure Poisson equation is solved by the node-based Galerkin FE method for an auxiliary variable. The auxiliary variable is used to update the velocity field and the pressure field. The pressure field is carefully updated by taking into account the velocity divergence field. Our current staggered-mesh scheme is distinct from other conventional ones in that we store the velocity components at cell centres and the auxiliary variable at vertices. The Generalized Minimal Residual (GMRES) matrix-free strategy is adapted to solve the governing equations in both FE and FV methods. The presented 2D and 3D numerical examples show the robustness and accuracy of the numerical method. 相似文献
325.
The paper presents structural, electronic and optical properties of boron-group V hexagonal nanowires (h-NW) within the framework of density functional theory. The h-NW of boron-group V compounds with an analogous diameter of 12 Å have been designed in (1 1 1) plane. Stability analysis performed through formation energies reveal that, the stability of these structures decreases with increasing atomic number of the group V element. The band nature predicts that these nanowires are good electrical conductors. Optical behaviour of the nanowires has been analysed through absorption coefficient, reflectivity, refractive index, optical conductivity and electron energy loss spectrum (EELS), that are computed from the frequency-dependent complex dielectric function. The analysis reveals high reactivity of BP and BAs h-NWs to the incident light especially in the IR and visible ranges, and the optical transparency of BN h-NW in the visible and UV ranges. 相似文献
326.
Madhusudanan KP Kumar B Tiwari P Madhusudan SK Misra AK 《Rapid communications in mass spectrometry : RCM》2005,19(4):470-476
Electrospray ionization mass spectra of some glycosyl dithioacetals recorded in the presence of transition-metal chlorides, XCl2 (where X = Co, Mn and Zn), give abundant adduct ions such as [M+XCl]+ and [2M-H+X]+ and minor ions such as [M-H+X]+ and [2M+XCl]+. The tandem mass spectra of these adducts show characteristic elimination of neutral molecules such as H2O, HCl, EtSH, CH2O, C2H4O2/C2H4O. [M+XCl]+ ions fragment readily and the fragmentation appears to be stereochemically controlled as the relative abundances of the fragments are different for three stereoisomers. The added metal is lost as neutral molecules in the form of XCl(OH) and XCl(SEt). This is a predominant pathway in the ZnCl+ adducts. [2M+XCl]+ ions fragment preferentially by elimination of HCl, indicating strong metal interactions in the resulting dimeric [2M-H+X]+ ion. As there are several electron-rich centers in the molecule, the dimeric complex [2M-H+X]+ can have several structures and the observed fragmentations may reflect the sum of those of all these structures. The dimeric complexes fragment by elimination of neutral molecules leaving the dimeric interactions intact. The extent of fragmentation varies for the stereoisomers, leading to stereochemical differentiation. 相似文献
327.
Chandrika Prasad Raj Krishan Jain Som Raj Soni 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1972,23(6):941-948
Summary Free axisymmetric vibrations of circular plates of linearly varying thickness have been studied on the basis of classical theory of plates. The differential equation governing the motion of such plates have been solved by Frobenius method. The transverse displacement has been expressed as an infinite power series in the radial coordinate. Frequency parameters have been computed for the first three modes of vibration for clamped as well as simply supported circular plates corresponding to different values of taper constant.
Zusammenfassung Auf Grund der klassischen Scheibentheorie werden die freien axialsymmetrischen Schwingungen der Kreisscheibe mit linear veränderlicher Dicke studiert. Die Differentialgleichung der Bewegung wird mit Hilfe der Methode von Frobenius gelöst. Die transversale Verschiebung wird als eine Reihe der radialen Koordinaten ausgedrückt. Die Schwingungsparameter werden für die ersten drei Eigenschwingungen sowohl für die eingespannte als auch für die aufgelegte Kreisscheibe für verschiedene Werte des Anzugs berechnet.相似文献
328.
Shailendra Kumar G Ravikumar P K Mishra P Chaddah B A Dasannacharya Ram Prasad N C Soni 《Pramana》1990,34(4):279-287
We have studied the variation of low field magnetization hysteresis in YBa2Cu3O7 as a function of the maximum magnetic field applied during a hysteresis cycle (1 G<H
max<7.3 G) and also as a function of temperature (77 K<T<95 K). The remnant magnetization is studied as a function ofH
max andT and the measured dependences are explained using the extended critical state model. The potential of this technique as a
contactless method of probing the temperature dependence ofJ
c is discussed. 相似文献
329.
Applied Biochemistry and Biotechnology - Continuous acetone-butanol fermentation was investigated for solvent production. After approximately 11–15 d of continuous operation, the nutrient... 相似文献
330.
Pandey JD Sanguri V Tripathi SB Mishra RK Soni NK 《Journal of colloid and interface science》2004,274(1):331-333
The surface tension of a ternary liquid mixture of nitrogen, oxygen, and argon has been calculated by a new approach using critical constants Pc, Vc, and Tc at temperatures ranging from 90 to 110 K and pressure up to 865 kPa. New formalism has been made by modifying the Brock-Bird relation. The computed values are compared with the experimental findings. Satisfactory results have been obtained. 相似文献