全文获取类型
收费全文 | 809篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
化学 | 393篇 |
晶体学 | 11篇 |
力学 | 22篇 |
数学 | 56篇 |
物理学 | 340篇 |
出版年
2024年 | 8篇 |
2022年 | 14篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 29篇 |
2013年 | 69篇 |
2012年 | 42篇 |
2011年 | 49篇 |
2010年 | 41篇 |
2009年 | 32篇 |
2008年 | 41篇 |
2007年 | 35篇 |
2006年 | 25篇 |
2005年 | 30篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1971年 | 5篇 |
1959年 | 5篇 |
排序方式: 共有822条查询结果,搜索用时 15 毫秒
81.
M. K. Pandey R. K. Dubey D. N. Tripathi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):275-279
The Classical Trajectory Monte Carlo (CTMC) Method has
been used to calculate the differential, partial and total single electron
capture cross sections for the collision of H+/D+ with Ca and Mg
atoms in the energy range of 1–100 keV. The differential cross sections
at angles near the diffraction limit (<0.1○) in both systems
show a forward peak followed by an asymptotic fall at higher angles. Total
and partial capture cross sections are found to be in good agreement with
the experimental observations. Oscillations in the partial capture cross sections have been explained due to the swapping
of the field electron.
Isotope effect in the electron transfer is reported to be negligible. 相似文献
82.
Photoluminescence (PL) properties of swift heavy ions-induced F2 and F3+ color centers in nano-granular lithium fluoride (LiF) thin film were studied. LiF films were deposited on glass and silica substrates and irradiated with various ion species (Ag, Ni and Au) at different irradiation temperatures. The role of ion species, their fluence and the irradiation temperature on the PL intensity of color centers induced in LiF thin films is discussed. 相似文献
83.
84.
Using filament stretching rheometry to predict strand formation and “processability” in adhesives and other non-Newtonian fluids 总被引:1,自引:0,他引:1
The spinning of polymeric fibers, the processing of numerous foodstuffs and the peel and tack characteristics of adhesives
are all associated with the formation, stability and, ultimately, the longevity of thin fluid `strands'. This tendency to
form strands is usually described in terms of the tackiness of the fluid or by heuristic concepts such as `stringiness' (Lakrout
et al. J Adhesion 1999). The dynamics of such processes are complicated due to spatially and temporally non-homogeneous growth
of extensional stresses, the action of capillary forces and the evaporation of volatile solvents. We describe the development
and application of a simple instrument referred to as a microfilament rheometer (MFR) that can be used to readily differentiate
between the dynamical response of different pressure-sensitive adhesive fluid formulations. The device relies on a quantitative
observation of the rate of extensional thinning or `necking' of a thin viscous or viscoelastic fluid filament in which the
solvent is free to evaporate across the free surface. This high-resolution measurement of the radial profile provides a direct
indication of the ultimate time to break up of the fluid filament. This critical time is a sensitive function of the rheological
properties of the fluid and the mass transfer characteristics of the solvent, and can be conveniently reported in terms of
a new dimensionless quantity we refer to as a processability parameter P. We demonstrate the usefulness of this technique by presenting our results in the form of a case study in which we measure
the visco-elasto-capillary thinning of slender liquid filaments for a number of different commercial polymer/solvent formulations
and relate this to the reported processing performance of the materials. We also compare the MFR observations with the prediction
of a simple 1D theory derived from the governing equations that model the capillary thinning of an adhesive filament.
Received: 22 December 1999/Accepted: 4 January 2000 相似文献
85.
We study projective curvature tensor in K-contact and Sasakian manifolds. We prove that (1) if a K-contact manifold is quasi projectively flat then it is Einstein and (2) a K-contact manifold is ξ-projectively flat if and only if it is Einstein Sasakian. Necessary and sufficient conditions for a K-contact manifold to be quasi projectively flat and φ-projectively flat are obtained. We also prove that for a (2n + 1)-dimensional Sasakian manifold the conditions of being quasi projectively flat, φ-projectively flat and locally isometric to the unit sphere S
2n+1 (1) are equivalent. Finally, we prove that a compact φ-projectively flat K-contact manifold with regular contact vector field is a principal S
1-bundle over an almost Kaehler space of constant holomorphic sectional curvature 4. 相似文献
86.
The steady state and time domain spectroscopy of 9-aminoacridinium hydrochloride have been studied. 9-aminoacridine (I), 9-aminoacridinium
(II) and the double protonated ion (III) follow Waterman’s principle with respect to their spectra and lifetimes. It is established
that the excimer formation in (II) is from the ground state dimers which undergo either thermally-activated radiationless
excimer conversion or a geometrical rearrangement in the excited state at room temperature. The quenching of monomer emission
by dimers or foreign quenchers (KI) is found to be of transient nature as suggested by the continuum model.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
87.
88.
Tavorite‐structured oxyphosphates, fluorophosphates, oxysulfates, and fluorosulfates are evaluated for use as cathode materials in lithium ion batteries and activation energies for lithium diffusion through LiVO(PO4), LiV(PO4)F, and LiFe(SO4)F are calculated. 相似文献
89.
A rapid and semi-quantitative immunochromatographic strip (ICS) test for cortisol analysis in serum was developed. The test strip was based on a competitive assay format. Colloidal gold nanoparticles were synthesized and coupled with cortisol-3-carboxymethyloxime-adipic acid dihydrazide-bovine serum albumin (F-3-CMO-ADH-BSA) antigen to directly compete with cortisol in human serum samples. F-3-CMO-ADH-BSA-gold label and uncoupled colloidal gold nanoparticles were appropriately characterized using UV-vis spectroscopy, transmission electron microscopy and atomic force microscopy. Anticortisol antibody raised against F-3-CMO-BSA immunogen in New Zealand white rabbits was coated on the NC membrane as test line. Anti-BSA antibody was used as control line. The lower detection limit of the ICS test was 30 ngmL(-1) with visual detection and was completed in 10 min. About 30 human serum samples were also analyzed by the developed strip test and their range of cortisol concentration was established. The developed ICS test is rapid, economic and user friendly. 相似文献
90.
Munish Puri Aneet Kaur Ram Sarup Singh Anubhav Singh 《Applied biochemistry and biotechnology》2010,162(1):181-191
Response surface methodology was used to optimize the fermentation medium for enhancing naringinase production by Staphylococcus xylosus. The first step of this process involved the individual adjustment and optimization of various medium components at shake
flask level. Sources of carbon (sucrose) and nitrogen (sodium nitrate), as well as an inducer (naringin) and pH levels were
all found to be the important factors significantly affecting naringinase production. In the second step, a 22 full factorial
central composite design was applied to determine the optimal levels of each of the significant variables. A second-order
polynomial was derived by multiple regression analysis on the experimental data. Using this methodology, the optimum values
for the critical components were obtained as follows: sucrose, 10.0%; sodium nitrate, 10.0%; pH 5.6; biomass concentration,
1.58%; and naringin, 0.50% (w/v), respectively. Under optimal conditions, the experimental naringinase production was 8.45 U/mL. The determination coefficients
(R
2) were 0.9908 and 0.9950 for naringinase activity and biomass production, respectively, indicating an adequate degree of reliability
in the model. 相似文献