全文获取类型
收费全文 | 12954篇 |
免费 | 351篇 |
国内免费 | 276篇 |
专业分类
化学 | 2049篇 |
晶体学 | 94篇 |
力学 | 69篇 |
综合类 | 27篇 |
数学 | 9989篇 |
物理学 | 1353篇 |
出版年
2023年 | 57篇 |
2022年 | 149篇 |
2021年 | 108篇 |
2020年 | 88篇 |
2019年 | 320篇 |
2018年 | 319篇 |
2017年 | 182篇 |
2016年 | 125篇 |
2015年 | 186篇 |
2014年 | 385篇 |
2013年 | 778篇 |
2012年 | 424篇 |
2011年 | 848篇 |
2010年 | 720篇 |
2009年 | 832篇 |
2008年 | 960篇 |
2007年 | 934篇 |
2006年 | 732篇 |
2005年 | 487篇 |
2004年 | 434篇 |
2003年 | 358篇 |
2002年 | 285篇 |
2001年 | 231篇 |
2000年 | 258篇 |
1999年 | 347篇 |
1998年 | 265篇 |
1997年 | 207篇 |
1996年 | 234篇 |
1995年 | 272篇 |
1994年 | 230篇 |
1993年 | 216篇 |
1992年 | 165篇 |
1991年 | 104篇 |
1990年 | 165篇 |
1989年 | 179篇 |
1988年 | 109篇 |
1987年 | 120篇 |
1986年 | 137篇 |
1985年 | 137篇 |
1984年 | 95篇 |
1983年 | 44篇 |
1982年 | 51篇 |
1981年 | 50篇 |
1980年 | 48篇 |
1979年 | 47篇 |
1978年 | 40篇 |
1977年 | 40篇 |
1976年 | 31篇 |
1975年 | 12篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
M.B. Pushkarsky M.E. Webber O. Baghdassarian L.R. Narasimhan C.K.N. Patel 《Applied physics. B, Lasers and optics》2002,75(2-3):391-396
An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO2 lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration
time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar
nature of ammonia. The minimum detectable fractional absorbance was 2.0×10-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10-7 W cm-1/z. The 9R(30) transition of the CO2 laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration
for simultaneous measurement in four cells.
Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com 相似文献
212.
Paolo?BoggiattoEmail author M. W.?WongEmail author 《Integral Equations and Operator Theory》2004,49(1):1-10
We give results on the boundedness and compactness of localization
operators with two admissible wavelets on
for the Weyl-Heisenberg
group. 相似文献
213.
Óscar Ciaurri 《Rendiconti del Circolo Matematico di Palermo》2004,53(2):231-234
A transference theorem for multipliers of Hermite expansions is proved. The result allows to transfer weightedL
2(ℝ
n
) estimates from lower to higher dimensions.
Research of the author supported by grant BFM2003-06335-603-03 of the D.G.I.. 相似文献
214.
G. Baszenski U. Schreiber G. Tasche 《Numerical Functional Analysis & Optimization》2013,34(1-2):25-46
In this paper we consider the numerical stability of fast algorithms for discrete cosine transform (DCT) of type III and II, respectively. We show that various fast DCTs can possess a very different behaviour of numerical stability. By matrix factorizations we find that a complex fast DCT which is based mainly on a fast Fouier transform has a better numerical stability than a real fast DCT despite its larger arithmetical complexity. Numerical tests illustrate our theoretical results. 相似文献
215.
It was founded using the magneto-optical technique that the domain wall in the iron-based amorphous ferromagnet in its movement experienced enhanced deceleration on the surface compared to the volume. The surface deceleration of the wall intensifies under water molecules adsorption on the sample surface. This effect is explained by the domain wall interaction with magnetic micro-defects observed on the sample surface using a magnetic force microscope. 相似文献
216.
Konstantinos Spiliopoulos Richard B. Sowers 《Stochastic Processes and their Applications》2011,121(12):2861-2898
We consider the effect of recovery rates on a pool of credit assets. We allow the recovery rate to depend on the defaults in a general way. Using the theory of large deviations, we study the structure of losses in a pool consisting of a continuum of types. We derive the corresponding rate function and show that it has a natural interpretation as the favored way to rearrange recoveries and losses among the different types. Numerical examples are also provided. 相似文献
217.
Igor Leite Freire Antonio Cândido Faleiros 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(11):3478-3486
Using the classical Lie method we obtain the full Lie point symmetry group of the Aronsson equation in two independent variables. Some group invariant solutions of this equation are found and a conjecture on the Lie point symmetry group of the Aronsson equation in Rn is presented. 相似文献
218.
219.
Dhruba R. Adhikari 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(14):4622-4641
Let X be an infinite dimensional real reflexive Banach space with dual space X∗ and G⊂X, open and bounded. Assume that X and X∗ are locally uniformly convex. Let T:X⊃D(T)→2X∗ be maximal monotone and strongly quasibounded, S:X⊃D(S)→X∗ maximal monotone, and C:X⊃D(C)→X∗ strongly quasibounded w.r.t. S and such that it satisfies a generalized (S+)-condition w.r.t. S. Assume that D(S)=L⊂D(T)∩D(C), where L is a dense subspace of X, and 0∈T(0),S(0)=0. A new topological degree theory is introduced for the sum T+S+C, with degree mapping d(T+S+C,G,0). The reason for this development is the creation of a useful tool for the study of a class of time-dependent problems involving three operators. This degree theory is based on a degree theory that was recently developed by Kartsatos and Skrypnik just for the single-valued sum S+C, as above. 相似文献
220.
Daniel Simson 《Journal of Pure and Applied Algebra》2011,215(1):13-34
Integral quadratic forms q:Zn→Z, with n≥1, and the sets Rq(d)={v∈Zn;q(v)=d}, with d∈Z, of their integral roots are studied by means of mesh translation quivers defined by Z-bilinear morsifications bA:Zn×Zn→Z of q, with Z-regular matrices A∈Mn(Z). Mesh geometries of roots of positive definite quadratic forms q:Zn→Z are studied in connection with root mesh quivers of forms associated to Dynkin diagrams An,Dn,E6,E7,E8 and the Auslander-Reiten quivers of the derived category Db(R) of path algebras R=KQ of Dynkin quivers Q. We introduce the concepts of a Z-morsification bA of a quadratic form q, a weighted ΦA-mesh of vectors in Zn, and a weighted ΦA-mesh orbit translation quiver Γ(Rq,ΦA) of vectors in Zn, where Rq?Rq(1) and ΦA:Zn→Zn is the Coxeter isomorphism defined by A. The existence of mesh geometries on Rq is discussed. It is shown that, under some assumptions on the morsification bA:Zn×Zn→Z, the set admit a ΦA-orbit mesh quiver , where ΦA:Zn→Zn is the Coxeter isomorphism defined by A. Moreover, splits into three infinite connected components , , and , where are isomorphic to a translation quiver Z⋅Δ, with Δ an extended Dynkin quiver, and has the shape of a sand-glass tube. 相似文献