全文获取类型
收费全文 | 3814篇 |
免费 | 86篇 |
国内免费 | 24篇 |
专业分类
化学 | 2323篇 |
晶体学 | 16篇 |
力学 | 113篇 |
数学 | 574篇 |
物理学 | 898篇 |
出版年
2023年 | 25篇 |
2021年 | 82篇 |
2020年 | 45篇 |
2019年 | 55篇 |
2018年 | 60篇 |
2017年 | 53篇 |
2016年 | 73篇 |
2015年 | 75篇 |
2014年 | 72篇 |
2013年 | 175篇 |
2012年 | 192篇 |
2011年 | 236篇 |
2010年 | 124篇 |
2009年 | 114篇 |
2008年 | 197篇 |
2007年 | 224篇 |
2006年 | 186篇 |
2005年 | 173篇 |
2004年 | 142篇 |
2003年 | 118篇 |
2002年 | 112篇 |
2001年 | 52篇 |
2000年 | 65篇 |
1999年 | 43篇 |
1998年 | 39篇 |
1997年 | 32篇 |
1996年 | 46篇 |
1995年 | 39篇 |
1994年 | 32篇 |
1993年 | 65篇 |
1992年 | 48篇 |
1991年 | 48篇 |
1990年 | 27篇 |
1989年 | 37篇 |
1988年 | 32篇 |
1987年 | 51篇 |
1986年 | 32篇 |
1985年 | 44篇 |
1984年 | 44篇 |
1983年 | 31篇 |
1982年 | 45篇 |
1981年 | 44篇 |
1980年 | 26篇 |
1979年 | 38篇 |
1978年 | 42篇 |
1977年 | 26篇 |
1976年 | 35篇 |
1975年 | 40篇 |
1974年 | 46篇 |
1973年 | 34篇 |
排序方式: 共有3924条查询结果,搜索用时 15 毫秒
21.
Glow Discharge Yuan Mei Douglas C. Duckworth Paula R. Cable R. Kenneth Marcus 《Journal of the American Society for Mass Spectrometry》1994,5(9):845-851
Collision-induced dissociation (CID) of polyatomic ions sampled from an rf-powered glow discharge is examined by using three target gases including atomic (Ar and Xe) and molecular species (N2). Collisions with these targets in the first quadrupole of the double quadrupole system result in the loss of discharge species by dissociation, symmetric and asymmetric charge exchange, and scattering, each to varying degrees. These processes are seen to be a function of the relative mass, size... and ionization potentials of the target species, as well as the collision center-of-mass energies. In light of the comparisons, xenon appears to be the best collision target for both CID and charge exchange because of its relatively low ionization potential and high dissociation efficiency of polyatornic species. Evidence for both symmetric and asymmetric charge exchange is presented for Ar and Xe target gases. 相似文献
22.
An asymptotic formula is obtained for the number of representations of an element of a finite field as a weighted sum of two prescribed powers of primitive elements. This generalises previous work on sums of primitive elements, including that relating to some conjectures of Golomb. 相似文献
23.
24.
Albert Cohen Sidi Mahmoud Kaber Siegfried Mü ller Marie Postel. 《Mathematics of Computation》2003,72(241):183-225
The use of multiresolution decompositions in the context of finite volume schemes for conservation laws was first proposed by A. Harten for the purpose of accelerating the evaluation of numerical fluxes through an adaptive computation. In this approach the solution is still represented at each time step on the finest grid, resulting in an inherent limitation of the potential gain in memory space and computational time. The present paper is concerned with the development and the numerical analysis of fully adaptive multiresolution schemes, in which the solution is represented and computed in a dynamically evolved adaptive grid. A crucial problem is then the accurate computation of the flux without the full knowledge of fine grid cell averages. Several solutions to this problem are proposed, analyzed, and compared in terms of accuracy and complexity.
25.
M. A. Cohen Stuart G. J. Fleer B. H. Bijsterbosch 《Journal of colloid and interface science》1982,90(2)
The adsorption of the flexible, linear, and nonionic homopolymer poly(vinyl pyrrolidone) from water and from 1,4-dioxane onto pyrogenic silica was studied. Results are reported for the adsorbed amount as a function of adsorption time, molecular mass, and molecular mass distribution (polydispersity). It is found that the adsorption of fractionated samples can be qualitatively explained by the recent theory of Scheutjens and Fleer. However, the influence of the solvent type is larger than predicted by this theory, and an extension of the model to account for this influence is suggested. The polydispersity effects encountered in adsorption isotherms are satisfactorily accounted for by a theory published by Cohen Stuart, Scheutjens, and Fleer. 相似文献
26.
Summary The evolution of radiochemistry at the National Atomic Energy Commission (CNEA) in Argentina is analyzed. The antecedents
of the establishment, in 1998, of the Master Programme in Radiochemistry, jointly organized by CNEA and the Buenos Aires Regional
Faculty of the National Technological University are revised, and the structure of the Programme is described. On the basis
of the thesis works, the initial trends are discussed. Finally, the institutional results of the Programme are described. 相似文献
27.
The exterior of a cross-linked polymer gel resembles a polymer brush. Such gel including its brush can be swollen by a good solvent. The detachment of the solvent–vapor (L–V) interface from the brush is controlled by the adsorption of polymer segments onto this interface and is to a very good approximation not influenced by long-range van der Waals contributions. A wetting transition in this system coincided with the adsorption–desorption transition for chains onto such L–V interface and has various unusual features. There are several indications that in practice this system should feature a second-order wetting transition. 相似文献
28.
29.
Stephen D. Cohen 《Monatshefte für Mathematik》1989,107(4):291-301
Chambers andSmeets [3] have designed a windmill arrangement of linear feedback shift registers (LFSRs) to generate pn-sequences overGF(2) with high speed. When the windmill hasv vanes, the associated minimal feedback polynomial (having degreen, relatively prime tov) can be taken to have the shapef
1(x
v
)+x
n
f
2(x
–v
), where the polynomialsf
1 andf
2 have degree [n/v]. Their numerical evidence, whenv is divisible by 4, suggests that, surprisingly, there areno such windmill polynomials which are irreducible ifn±3 (mod 8), while about twice as many irreducible and primitive windmill polynomials as they expected occur ifn±1 (mod 8). A discussion of this behaviour is presented here with proofs. The brief explanation is that the Galois group of the underlying generic windmill polynomial overGF (4) is equal to the alternating groupA
n
. 相似文献
30.