全文获取类型
收费全文 | 437190篇 |
免费 | 4878篇 |
国内免费 | 1235篇 |
专业分类
化学 | 234489篇 |
晶体学 | 6490篇 |
力学 | 18781篇 |
综合类 | 13篇 |
数学 | 50194篇 |
物理学 | 133336篇 |
出版年
2021年 | 3779篇 |
2020年 | 4204篇 |
2019年 | 4533篇 |
2018年 | 5862篇 |
2017年 | 5750篇 |
2016年 | 8854篇 |
2015年 | 5584篇 |
2014年 | 8575篇 |
2013年 | 20231篇 |
2012年 | 15689篇 |
2011年 | 19308篇 |
2010年 | 13547篇 |
2009年 | 13386篇 |
2008年 | 17704篇 |
2007年 | 17574篇 |
2006年 | 16291篇 |
2005年 | 14584篇 |
2004年 | 13550篇 |
2003年 | 11913篇 |
2002年 | 11750篇 |
2001年 | 13442篇 |
2000年 | 10102篇 |
1999年 | 7932篇 |
1998年 | 6579篇 |
1997年 | 6326篇 |
1996年 | 6099篇 |
1995年 | 5490篇 |
1994年 | 5407篇 |
1993年 | 5214篇 |
1992年 | 5852篇 |
1991年 | 5938篇 |
1990年 | 5679篇 |
1989年 | 5485篇 |
1988年 | 5501篇 |
1987年 | 5384篇 |
1986年 | 5102篇 |
1985年 | 6583篇 |
1984年 | 6715篇 |
1983年 | 5316篇 |
1982年 | 5407篇 |
1981年 | 5386篇 |
1980年 | 4974篇 |
1979年 | 5364篇 |
1978年 | 5515篇 |
1977年 | 5396篇 |
1976年 | 5339篇 |
1975年 | 4930篇 |
1974年 | 4904篇 |
1973年 | 4888篇 |
1972年 | 3464篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
W M Niessen M A de Kraa E R Verheij P J Bergers G F La Vos U R Tjaden J van der Greef 《Rapid communications in mass spectrometry : RCM》1989,3(1):1-4
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL. 相似文献
82.
We prove some new evaluations for multiple polylogarithms of arbitrary depth. The simplest of our results is a multiple zeta evaluation one order of complexity beyond the well-known Broadhurst–Zagier formula. Other results we provide settle three of the remaining outstanding conjectures of Borwein, Bradley, and Broadhurst. A complete treatment of a certain arbitrary depth class of periodic alternating unit Euler sums is also given. 相似文献
83.
84.
85.
O. Perru F. Ibrahim O. Bajeat C. Bourgeois F. Clapier E. Cottereau C. Donzaud M. Ducourtieux S. Galès D. Guillemaud-Mueller C. Lau H. Lefort F. Le Blanc A. C. Mueller J. Obert N. Pauwels J. C. Potier F. Pougheon J. Proust B. Roussière J. Sauvage O. Sorlin D. Verney 《Physics of Atomic Nuclei》2003,66(8):1421-1427
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time. 相似文献
86.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
87.
In basin modelling the thermodynamics of a multicomponent multiphase fluid flux are computationally too expensive when derived from an equation of state and the Gibbs equality constraints. In this article we present a novel implicit molar mass formulation technique using binary mixture thermodynamics. The two proposed solution methods, with and without cross derivative terms between components, are based on a preconditioned Newton‐GMRES scheme for each time‐step with analytical computation of the derivatives. These new algorithms reduce significantly the numerical effort for the computation of the molar masses, and we illustrate the behavior of these methods with numerical computations. Copyright © 2004 John Wiley & Sons Ltd. 相似文献
88.
A preconditioning approach based on the artificial compressibility formulation is extended to solve the governing equations for unsteady turbulent reactive flows with heat release, at low Mach numbers, on an unstructured hybrid grid context. Premixed reactants are considered and a flamelet approach for combustion modelling is adopted using a continuous quenched mean reaction rate. An overlapped cell‐vertex finite volume method is adopted as a discretisation scheme. Artificial dissipation terms for hybrid grids are explicitly added to ensure a stable, discretised set of equations. A second‐order, explicit, hybrid Runge–Kutta scheme is applied for the time marching in pseudo‐time. A time derivative of the dependent variable is added to recover the time accuracy of the preconditioned set of equations. This derivative is discretised by an implicit, second‐order scheme. The resulting scheme is applied to the calculation of an infinite planar (one‐dimensional) turbulent premixed flame propagating freely in reactants whose turbulence is supposed to be frozen, homogeneous and isotropic. The accuracy of the results obtained with the proposed method proves to be excellent when compared to the data available in the literature. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
89.
Oksengendler B. L. Karimov M. Yunusov M. C. Karakhodzhaev A. K. 《Russian Physics Journal》2004,47(7):790-791
Russian Physics Journal - 相似文献
90.