全文获取类型
收费全文 | 5970篇 |
免费 | 1230篇 |
国内免费 | 598篇 |
专业分类
化学 | 3323篇 |
晶体学 | 110篇 |
力学 | 919篇 |
综合类 | 31篇 |
数学 | 223篇 |
物理学 | 3192篇 |
出版年
2024年 | 17篇 |
2023年 | 41篇 |
2022年 | 175篇 |
2021年 | 184篇 |
2020年 | 275篇 |
2019年 | 192篇 |
2018年 | 150篇 |
2017年 | 185篇 |
2016年 | 336篇 |
2015年 | 258篇 |
2014年 | 405篇 |
2013年 | 513篇 |
2012年 | 367篇 |
2011年 | 397篇 |
2010年 | 338篇 |
2009年 | 365篇 |
2008年 | 393篇 |
2007年 | 367篇 |
2006年 | 373篇 |
2005年 | 312篇 |
2004年 | 331篇 |
2003年 | 267篇 |
2002年 | 258篇 |
2001年 | 198篇 |
2000年 | 169篇 |
1999年 | 121篇 |
1998年 | 130篇 |
1997年 | 107篇 |
1996年 | 96篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 58篇 |
1992年 | 45篇 |
1991年 | 46篇 |
1990年 | 24篇 |
1989年 | 37篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有7798条查询结果,搜索用时 265 毫秒
71.
Klaus Ziegler 《Journal of multivariate analysis》1997,62(2):233-272
Functional central limit theorems for triangular arrays of rowwise independent stochastic processes are established by a method replacing tail probabilities by expectations throughout. The main tool is a maximal inequality based on a preliminary version proved by P. Gaenssler and Th. Schlumprecht. Its essential refinement used here is achieved by an additional inequality due to M. Ledoux and M. Talagrand. The entropy condition emerging in our theorems was introduced by K. S. Alexander, whose functional central limit theorem for so-calledmeasure-like processeswill be also regained. Applications concern, in particular, so-calledrandom measure processeswhich include function-indexed empirical processes and partial-sum processes (with random or fixed locations). In this context, we obtain generalizations of results due to K. S. Alexander, M. A. Arcones, P. Gaenssler, and K. Ziegler. Further examples include nonparametric regression and intensity estimation for spatial Poisson processes. 相似文献
72.
Eu^2+:BaFCl光激励发光过程中紫外线的激发与漂白效应 总被引:1,自引:1,他引:0
通过改变紫外线的辐射照能量范围,研究了Eu^2+:BaFCl的光激励发光性质。发现紫外线能量大于Eu^2+的最低激发态能量及紫外线的能量小于Eu^2+最低激发态的能量两种情况下,光激励发光具有明显的差异,分析了产生差异的原因,给出了紫外线的辐照能量发生转时所对应的能级位置。 相似文献
73.
Hong Chen 《Queueing Systems》1989,5(4):281-293
We study a mixed problem of optimal scheduling and input and output control of a single server queue with multi-classes of customers. The model extends the classical optimal scheduling problem by allowing the general point processes as the arrival and departure processes and the control of the arrival and departure intensities. The objective of our scheduling and control problem is to minimize the expected discounted inventory cost over an infinite horizon, and the problem is formulated as an intensity control. We find the well-knownc is the optimal solution to our problem.Supported in part by NSF under grant ECS-8658157, by ONR under contract N00014-84-K-0465, and by a grant from AT&T Bell Laboratories.The work was done while the author was a postdoctoral fellow in the Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138. 相似文献
74.
0 Introduction Recently, a considerable effort on crystal engi- neering has been devoted to the research of supramolecular assemblies because they show abun- dant topologic structures and offer possibilities for po- tential applications of functional mate… 相似文献
75.
T. S. Martins J. R. Matos G. Vicentini P. C. Isolani 《Journal of Thermal Analysis and Calorimetry》2005,82(1):77-82
Summary Rare earth picrate (RE) complexes with L-lysine (Lys) were synthesized and characterized. Elemental analysis (CHN), EDTA titrations and thermogravimetry data suggest
a general formula RE(pic)3·2Lys·2H2O, where RE=La-Lu (without Pm) and Y, pic=picrate). IR spectra suggest that Lys is coordinated to the central ion through the nitrogen of the α-amino group. Parameters
obtained from the absorption spectrum of the Nd compound indicated that the metal-ligand bonds are essentially electrostatic.
Emission spectrum and biexponential behavior of the luminescence decay of the Eu compound suggest the existence of polymeric
species. Thermogravimetric/derivative thermogravimetric (TG/DTG) and differential scanning calorimetry (DSC) curves of all
complexes are very similar, with five events. The final products are the corresponding rare earth oxides and their X-ray diffraction
patterns are identical to the calcinated oxides.</o:p> 相似文献
76.
E. L. Kristallovich A. G. Eshimbetov V. M. Promyslov N. D. Chuvylkin L. I. Belen'kii L. V. Molchanov Kh. M. Shakhidoyatov 《Chemistry of Heterocyclic Compounds》2003,39(11):1516-1520
Quantum-chemical calculations and IR spectroscopy were used to study the conformations as well as the energy and spectral characteristics of 2,3-trimethylene- and 2,3-pentamethylene-3,4-dihydro-4-quinazolinones. The shift of -electron density from the heterocyclic system to the carbonyl group and, thus, the proton affinity of the oxygen atom of this group increase with expansion of the bond angle at the nitrogen atom in going from a five-membered to seven-membered ring. 相似文献
77.
A. E. Raevskaya A. L. Stroyuk S. Ya. Kuchmii Yu. M. Azhnyuk V. M. Dzhagan M. Ya. Valakh 《Theoretical and Experimental Chemistry》2006,42(3):162-168
The optical characteristics of CdSe nanoparticles, produced in aqueous solutions and polymer films in the reaction of cadmium
chloride and sodium selenosulfate, were studied. The main parameters that make it possible to vary the forbidden band width
were identified. The absorption, photoluminescence, Raman, and nonstationary decolorization spectra of CdSe nanoparticles
of various sizes were analyzed. It was demonstrated that under the conditions of pulsed irradiation the CdSe nanoparticles
are capable of accumulating excess electrons and inducing redox transformations in components of the solution (oxygen, methylviologen,
and sulfite ions).
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 150–155, May–June, 2006. 相似文献
78.
The association constant K of mono-acetato complex of Tb3+ has been determined at normal p and T conditions by measurement of its luminescence lifetime in aqueous solution containing increasing concentrations of acetate. Two experimental arrangements used for the measurement are described. 相似文献
79.
80.