全文获取类型
收费全文 | 2460篇 |
免费 | 287篇 |
国内免费 | 152篇 |
专业分类
化学 | 727篇 |
晶体学 | 24篇 |
力学 | 312篇 |
综合类 | 97篇 |
数学 | 446篇 |
物理学 | 1293篇 |
出版年
2024年 | 4篇 |
2023年 | 20篇 |
2022年 | 53篇 |
2021年 | 56篇 |
2020年 | 54篇 |
2019年 | 37篇 |
2018年 | 51篇 |
2017年 | 77篇 |
2016年 | 101篇 |
2015年 | 71篇 |
2014年 | 112篇 |
2013年 | 153篇 |
2012年 | 95篇 |
2011年 | 136篇 |
2010年 | 123篇 |
2009年 | 150篇 |
2008年 | 164篇 |
2007年 | 178篇 |
2006年 | 187篇 |
2005年 | 166篇 |
2004年 | 129篇 |
2003年 | 114篇 |
2002年 | 94篇 |
2001年 | 80篇 |
2000年 | 68篇 |
1999年 | 58篇 |
1998年 | 57篇 |
1997年 | 47篇 |
1996年 | 43篇 |
1995年 | 33篇 |
1994年 | 34篇 |
1993年 | 23篇 |
1992年 | 19篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1969年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有2899条查询结果,搜索用时 328 毫秒
161.
162.
Anil Kumar 《Journal of Chemical Sciences》1986,97(1):1-7
The distribution of nickel and cobalt species has been computed, based on the pH-dependent model of Zirino and Yamamoto. The
media used in the pH range of 7 to 9 are natural waters like fresh water, sea water and a mixture of them at different compositions,
at 25°C temperature and 1 atm pressure. In fresh water, both nickel and cobalt dominate as free cations at lower pH, and as
carbonato complexes at higher pH. In sea water, chloro complexes are significant. In mixtures of the two kinds of water, as
might be found in a totally mixed estuary, chloro complexes are important, varying slowly with pH. Sea water plays an important
role in complexation. The present results are in excellent agreement with experimental data obtained by the resin exchange
method. 相似文献
163.
164.
Quantised phase filters with binary low and high pass amplitude response: the effect of quantisation for scale and rotation input distortions 总被引:1,自引:0,他引:1
Triantafillos Koukoulas Rupert C.D. Young Chris R. Chatwin 《Optics and Lasers in Engineering》2005,43(9):963
In the field of optical pattern recognition, there are a large number of filters that possess identification capabilities for certain kinds of input distortions. The resolution of the spectral components plays an important role in the overall processing time of a correlator that may employ such filters. In this paper, two different techniques are discussed: low pass phase filtering and high pass phase filtering. This is achieved by binarizing the amplitude information which then allows certain frequencies to pass and others to be blocked. Their response to different kinds of input distortions is presented and the effect of phase quantisation is considered in detail. 相似文献
165.
Peter R. Cromwell 《Geometriae Dedicata》2008,137(1):63-84
We extend the classification of pattern types by Grünbaum and Shephard to the 2-sided plane to include patterns having layered
or interlaced motifs. Such patterns may have symmetries that turn the plane over. There are 17 infinite families of pattern
types for 2-sided rosettes (twelve 1-parameter families and five 2-parameter families), 68 types of 2-sided frieze pattern,
and 264 types of 2-sided periodic pattern. The definition of ‘henomeric’ is clarified to ensure that two of the periodic patterns
are distinguished.
相似文献
166.
P. Bot I. Mutabazi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):141-155
The dynamics of defects in a pattern of traveling inclined rolls has been investigated. Two regimes were identified in the
neighborhood of defects: a diffusive regime, with a negative phase diffusion coefficient, and a coalescence regime in which
the phase gradient diverges in time following a power law behavior. The observed periodic nucleation of defects is related
to the frequency inhomogeneity induced by the disymmetry of the wave amplitude. Amplitude holes have been observed in the
secondary modulated pattern.
Received 23 February 1999 and Received in final form 26 May 1999 相似文献
167.
Ulrike Bücking 《Geometriae Dedicata》2008,137(1):163-197
A circle pattern is a configuration of circles in the plane whose combinatorics is given by a planar graph G such that to each vertex of G corresponds a circle. If two vertices are connected by an edge in G, the corresponding circles intersect with an intersection angle in (0, π). Two sequences of circle patterns are employed to approximate a given conformal map g and its first derivative. For the domain of g we use embedded circle patterns where all circles have the same radius decreasing to 0 and with uniformly bounded intersection
angles. The image circle pattern has the same combinatorics and intersection angles and is determined from boundary conditions
(radii or angles) according to the values of g′ (|g′| or arg g′). For quasicrystallic circle patterns the convergence result is strengthened to C
∞-convergence on compact subsets.
相似文献
168.
A monomer design having a bulky terminal tricyclodecane (TCD) unit linked via hydrogen bondable urethane to an ethyleneoxy methacrylate unit, and capable of generating three‐dimensional honeycomb patterns upon solvent casting has been investigated. Random copolymers as well as a diblock copolymer Poly(Sty42‐b‐TCD18) of this monomer with styrene were prepared by free‐radical polymerization route and atom transfer radical polymerization (ATRP) route. Morphology characterization was carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Particle size was measured by dynamic light scattering measurements (DLS). Irrespective of the wide differences in molecular weight and polydispersity index values, the random copolymers having TCD content >30 mol % were found to form microporous films upon solvent casting from a THF/water 9:1 solvent combination. The amount of TCD in the copolymer was found to have an influence on the pore size formed. The diblock copolymer formed microspheres ~200 nm in diameter. The thermal properties of all the polymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the copolymers were found to have good thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1278–1288, 2008 相似文献
169.
Uniaxial tension tests of semihard copper sheets were studied by means of electronic spekle pattern interferometry (ESPI).
The setup allowed the authors to analyze in detail the transitions from elastic to plastic behavior and from homogeneous to
inhomogeneous plastic deformation. In agreement with the conventional definition of the yield point for copper fully plastic
behavior starded at permanent strains close to 0.005. The strain-hardening coefficient was very low at the early stage of
plastic flow (“easy glide”), increasing progressively until values on the order of 0.13 to 0.14 were reached at maximum load.
A this point, the appearance of unequally spaced fringes signaled the beginning of inhomogeneous deformation. With ESPI, this
occurrence may thus serve as a criterion to establish the forming limit of the material. 相似文献
170.
Porosity, mechanical properties, residual stresses of supersonic plasma-sprayed Ni-based alloy coatings prepared at different powder feed rates 总被引:1,自引:0,他引:1
The aim of this paper was to investigate the effect of powder feed rate (PFR) on the microstructure and mechanical properties of the supersonic plasma-sprayed Ni-Cr-B-Si-C coatings. The microstructure, porosity and mechanical properties of the coatings and the residual stresses at the coating surfaces were experimentally determined. Results showed that the variations of porosity, elastic moduli and micro-hardness of the coatings followed Weibull distribution. From the statistical trend, the porosity of the coating increased with increasing PFR. However, the elastic modulus and the micro-hardness of the coating decreased and reached local minima and then increased with increasing PFR. Elastic modulus could be generally considered to be an increasing function of micro-hardness. The mean value of the elastic modulus of the coating calculated from Weibull plot was almost proportional to the square root of the mean value of the micro-hardness of the coating. Moreover, with increasing PFR, the residual stress at the coating surface, which was mainly governed by the elastic modulus of the coating, decreased to a local minimum and then increased. 相似文献