全文获取类型
收费全文 | 378081篇 |
免费 | 7288篇 |
国内免费 | 5237篇 |
专业分类
化学 | 189939篇 |
晶体学 | 5332篇 |
力学 | 19889篇 |
综合类 | 328篇 |
数学 | 56250篇 |
物理学 | 118868篇 |
出版年
2021年 | 3424篇 |
2020年 | 3976篇 |
2019年 | 4408篇 |
2018年 | 12475篇 |
2017年 | 12902篇 |
2016年 | 10454篇 |
2015年 | 5081篇 |
2014年 | 6883篇 |
2013年 | 13526篇 |
2012年 | 14901篇 |
2011年 | 23417篇 |
2010年 | 15506篇 |
2009年 | 15581篇 |
2008年 | 20822篇 |
2007年 | 23624篇 |
2006年 | 11043篇 |
2005年 | 14990篇 |
2004年 | 11362篇 |
2003年 | 10837篇 |
2002年 | 9145篇 |
2001年 | 8219篇 |
2000年 | 6684篇 |
1999年 | 4938篇 |
1998年 | 4399篇 |
1997年 | 4184篇 |
1996年 | 4112篇 |
1995年 | 3381篇 |
1994年 | 3524篇 |
1993年 | 3492篇 |
1992年 | 3588篇 |
1991年 | 3697篇 |
1990年 | 3593篇 |
1989年 | 3513篇 |
1988年 | 3348篇 |
1987年 | 3277篇 |
1986年 | 3185篇 |
1985年 | 3893篇 |
1984年 | 4099篇 |
1983年 | 3345篇 |
1982年 | 3585篇 |
1981年 | 3371篇 |
1980年 | 3140篇 |
1979年 | 3466篇 |
1978年 | 3639篇 |
1977年 | 3567篇 |
1976年 | 3652篇 |
1975年 | 3427篇 |
1974年 | 3418篇 |
1973年 | 3602篇 |
1972年 | 2546篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml−1 chloride. For solutions below this concentration, the relation is linear. 相似文献
242.
E. N. Yurchenko G. E. Kramareva N. G. Zubritskaya T. P. Gaidei 《Reaction Kinetics and Catalysis Letters》1995,55(2):425-432
In the Russian Scientific Center Applied Chemistry catalysts have been developed for the gas-phase fluorination of organics, including chlorine-containing substances, hydrogenation and reductive amination of organic substances, decomposition of liquid substances to gases, complete oxidation and reduction, suitable for environment at protection. 相似文献
243.
V. A. Nebol'sin B. M. Darinskii E. E. Popova A. A. Shchetinin 《Russian Physics Journal》1995,38(10):1023-1026
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995. 相似文献
244.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2]
n
·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993. 相似文献
245.
Summary This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when
viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms
whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential
equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration
process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using
the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order
algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions”
defined by nonvanishing Lie brackets. 相似文献
246.
A. E. Dorokhov 《Czechoslovak Journal of Physics》2002,52(3):C79-C90
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed. 相似文献
247.
We investigate the replica symmetry breaking (RSB) in a neighborhood of the instability point of the replica-symmetric solution in the axial quadrupolar glass model. We show that the solution with the first-stage RSB is stable against the subsequent RSB. Although there is no reflection symmetry, the first-stage RSB solution continuously bifurcates from the replica-symmetric one. This implies that our model does not belong to either of the two classes into which spin glasses are usually divided. 相似文献
248.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed. 相似文献
249.
We consider the inverse problem for the identification of the coefficient in a parabolic equation. The model is applied to describe the functioning of a hierarchical structure [1]; it is also relevant for heat-conduction theory [2]. Unique solvability of the inverse problem is proved. 相似文献
250.
Mathematical Notes - 相似文献