全文获取类型
收费全文 | 1010篇 |
免费 | 26篇 |
国内免费 | 6篇 |
专业分类
化学 | 707篇 |
晶体学 | 6篇 |
力学 | 24篇 |
数学 | 120篇 |
物理学 | 185篇 |
出版年
2022年 | 9篇 |
2021年 | 12篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 28篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 70篇 |
2012年 | 55篇 |
2011年 | 59篇 |
2010年 | 33篇 |
2009年 | 39篇 |
2008年 | 58篇 |
2007年 | 42篇 |
2006年 | 41篇 |
2005年 | 36篇 |
2004年 | 38篇 |
2003年 | 30篇 |
2002年 | 31篇 |
2001年 | 15篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1995年 | 11篇 |
1994年 | 18篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 13篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1969年 | 6篇 |
排序方式: 共有1042条查询结果,搜索用时 296 毫秒
81.
J.?VermantEmail author G.?Cioccolo K.?Golapan Nair P.?Moldenaers 《Rheologica Acta》2004,43(5):529-538
The effect of nanometer sized silica particles (R16 nm) on the flow-induced morphology of immiscible polymer blends is studied. Polydimethylsiloxane (PDMS) and polyisobutylene (PIB) are chosen as model components. A stable droplet/matrix microstructure is obtained for blends of 30% PIB in 70% PDMS or vice versa. Rheological measurements are used to show that the silica particles alter the sensitivity of the of dispersed phase/matrix microstructure to shear flow. Coalescence is suppressed or at least slowed down on a practical time scale, especially when PDMS is the matrix phase. The effect of mixing conditions, pre-shear rate and particle concentration on the blend morphology are studied. Cryo-SEM is used to observe the accumulation of the particles at the interface. Blends stabilized by solid particles could provide an interesting alternative to blends compatibilized by block-copolymers.This paper was presented at the first Annual European Rheology Conference (AERC) held in Guimarães, Portugal, September 11-13, 2003. 相似文献
82.
Nair VA Mustafa SM Mohler ML Fisher SJ Dalton JT Miller DD 《Tetrahedron letters》2004,45(51):9475-9477
A series of optically active nonsteroidal selective androgen receptor modulators with structures analogous to bicalutamide was prepared by replacing the trifluoromethyl group with iodine and the sulfonyl linker by oxygen. 相似文献
83.
[reaction: see text] Lewis acid-promoted addition of allyltri-n-butylstannane to o-quinonediimines afforded tetrahydroquinoxaline derivatives or allylated amides depending on the nature of the substituent on imine nitrogen. 相似文献
84.
Pemen A. J. M. Nair S. A. Yan K. van Heesch E. J. M. Ptasinski K. J. Drinkenburg A. A. H. 《Plasmas and Polymers》2003,8(3):209-224
To supply combustion engines or gasturbines with fuel gas obtained from biomass gasification, it is necessary to clean the fuel gas. Also the production of chemicals by processes such as Fisher-Tropsch requires a high gas quality. Especially heavy aromatic hydrocarbons (tars) must be removed. In this work, we give an overview of our investigations on tar removal by pulsed corona discharges as an alternative approach to catalytic or thermal tar cracking. Experimental results (at a gas temperature of 200°C) are reported for the removal of various model tar components in synthetic fuel gas. In order to identify the major reaction pathways, experiments were also done on tars in individual fuel gas components. The results show that tar removal by pulsed corona processing is possible. The process for tar removal is mainly via oxidation. Also termination reactions by CO play an important role. 相似文献
85.
P. Santhana Raman K.G.M. Nair R. Kesavamoorthy B.K. Panigrahi S. Dhara V. Ravichandran 《Applied Physics A: Materials Science & Processing》2007,87(4):709-713
Indium nanoclusters are synthesized in an amorphous silica matrix using an ion-implantation technique. Indium ions (In2+) with energy of 890 keV are implanted on silica to fluences in the range of 3×1016–3×1017 cm-2. The formation of indium nanoclusters is confirmed by optical absorption spectrometry and glancing incidence X-ray diffraction
studies. A low frequency Raman scattering technique is used to study the growth of embedded indium nanoclusters in the silica
matrix as a function of fluence and post-implantation annealing duration. Rutherford backscattering spectrometry studies show
the surface segregation of implanted indium. Photoluminescence studies indicate the formation of a small quantity of indium
oxide phase in the ion-implanted samples.
PACS 85.40.Ry; 78.67.Bf; 73.20.Mf; 82.75.Fq 相似文献
86.
Transient analysis of finite state birth and death process with absorbing barriers is carries out. Closed form expression for state probabilities and density functions of time of absorption and first passage time for each case is obtained along with the moments. The results are expressed in terms of eigenvalues of symmetric triadiagonal matrix which can be easily computed 相似文献
87.
The electric field gradient (EFG) at57Fe in titanium is measured using Mössbauer spectroscopy in the temperature range 80°–380°K. The value of EFG obtained at room temperature is 0.53(4)×1017 V/cm2. The value of EFG obtained is compared with the conduction electron charge shift model. 相似文献
88.
Poly(methyl methacrylate)-supportedβ-diketone-linked palladium complexes on refluxing with olefins at 70°C in methanol-water medium for 10 h afforded carbonyl
compounds. The course of the reaction was found to be influenced by the degree of cross-linking of the polymer matrix and
the structural environment of the ligand. The reaction is assumed to proceed through a hydroxy palladation intermediate. A
suitable mechanism is also suggested. 相似文献
89.
The addition-cured blends of diallyl bisphenol A formaldehyde resin (ABPF) with various bismaleimides (BMIs) were evaluated for thermal stability and degradation behavior by thermogravimetric analysis (TGA). TGA of the blend of ABPF and 2,2-bis 4-[(4-maleimido phenoxy) phenyl] propane (BMIP) with varying maleimide to allylphenol stoichiometry indicated that the thermal stability of the system was only marginally improved by the increase in BMI stoichiometry in the blend. The effect of BMI structure on thermal stability was studied using four different BMIs, viz. bis (4-maleimido phenyl) methane (BMIM), bis (4-maleimido phenyl) ether (BMIE), bis (4-maleimido phenyl) sulfone (BMIS) and BMIP. TGA showed a two stage decomposition pattern for BMIS system and a single stage for all the other three. The thermograms of BMIM and BMIE were identical and superior to that of BMIS; the latter showing a relatively poor performance at lower temperatures. Compared to the BMI-adduct of monomeric diallyl bisphenol A (DABA), the polymeric analog viz. ABPF system exhibited better thermal stability. Non-isothermal kinetic analyses of the different systems showed the decomposition occurring in at least two kinetic steps. The computed activation energy exhibited a direct correlation to the relative thermal stability of the systems. 相似文献
90.
A high‐order element‐based Galerkin method is developed to solve the non‐divergent barotropic vorticity equation (BVE). The solution process involves solving a conservative transport equation for the vorticity fields and a Poisson equation for the stream function fields. The discontinuous Galerkin method is employed for solving the transport equation and a spectral element method (continuous Galerkin) is used for the Poisson equation. A third‐order strong stability preserving explicit Runge–Kutta scheme is used for time integration. A series of tests have been performed to validate the model, which include the evolution of an idealized tropical cyclone and interaction of dual vortices in close proximity. The numerical convergence study is performed by solving the BVE on the sphere where the analytic solution is known. The test results are consistent with physical observations, and the model exhibits exponential convergence. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献