全文获取类型
收费全文 | 343799篇 |
免费 | 2805篇 |
国内免费 | 991篇 |
专业分类
化学 | 187024篇 |
晶体学 | 4970篇 |
力学 | 14376篇 |
综合类 | 12篇 |
数学 | 37606篇 |
物理学 | 103607篇 |
出版年
2020年 | 2883篇 |
2019年 | 3227篇 |
2018年 | 4380篇 |
2017年 | 4285篇 |
2016年 | 6313篇 |
2015年 | 3686篇 |
2014年 | 5823篇 |
2013年 | 14723篇 |
2012年 | 11075篇 |
2011年 | 13675篇 |
2010年 | 9640篇 |
2009年 | 9538篇 |
2008年 | 12878篇 |
2007年 | 13014篇 |
2006年 | 12147篇 |
2005年 | 11049篇 |
2004年 | 9807篇 |
2003年 | 8820篇 |
2002年 | 8759篇 |
2001年 | 9479篇 |
2000年 | 7452篇 |
1999年 | 5612篇 |
1998年 | 4891篇 |
1997年 | 4886篇 |
1996年 | 4527篇 |
1995年 | 3964篇 |
1994年 | 4026篇 |
1993年 | 3942篇 |
1992年 | 4289篇 |
1991年 | 4484篇 |
1990年 | 4197篇 |
1989年 | 4187篇 |
1988年 | 4049篇 |
1987年 | 3944篇 |
1986年 | 3776篇 |
1985年 | 4980篇 |
1984年 | 5173篇 |
1983年 | 4192篇 |
1982年 | 4632篇 |
1981年 | 4367篇 |
1980年 | 4125篇 |
1979年 | 4468篇 |
1978年 | 4718篇 |
1977年 | 4641篇 |
1976年 | 4678篇 |
1975年 | 4433篇 |
1974年 | 4464篇 |
1973年 | 4578篇 |
1972年 | 3068篇 |
1967年 | 2777篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
J. Krause und F. Umland 《Fresenius' Journal of Analytical Chemistry》1989,335(7):791-795
Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
113.
We show that, in dimensions equal or greater than three, classical strings do not join or split. This is part of a no-interaction theorem that is also proved. The quantum theory is considered. 相似文献
114.
Summary The available laboratory data of turbulent boundary layer flow over two-dimensional obstacles have been examined in order
to identify the parameters (such as the aspect ratio or the surface roughness) driving the onset of separation. A comparison
with some linearized models suitable for atmospheric applications is also made. It results that i) the model response can
be highly sensitive to the detailed shape of the obstacle; ii) the ratio between obstacle length and boundary layer thickness
is relevant in determining the pressure perturbation near the surface; iii) the surface shear stress is poorly described in
most cases and in particular in the obstacle wake.
Riassunto I dati di laboratorio disponibili, relativi a strati limite turbolenti su ostacoli bidimensionali, sono stati esaminati al fine di identificare i parametri guida della separazione (quali la pendenza o la rugosità della superficie). Inoltre è stato fatto un confronto con i risultati di alcuni modelli linearizzati adatti per applicazioni atmosferiche. Ne risulta che i) la risposta del modello è molto sensibile alla forma dettagliata dell’ostacolo; ii) il rapporto fra la lunghezza dell’ostacolo e lo spessore dello strato limite turbolento incidente è importante nel determinare la perturbazione della pressione vicino alla superficie; iii) lo ?shear stress? superficiale non è riprodotto con accuratezza nella maggioranza dei casi, in particolare nella scia dell’ostacolo.
Резюме Анализируются имеющиеся лабораторные данные по турбулентному течению в пограничном слое над двумерными препятствиями, чтобы идентифицировать параметры (такие как аспектное отношение или шероховатость поверхности), определяющие возникновение отрыва. Проводится сравнение с некоторыми линеаризованными моделями, удобными для атмосферных приложений. Получены следующие результаты: 1) модельный отклик может быть очень чувствительным к детальной форме препятствия; 2) отношение между длиной препятствия и толщиной поверхностного слоя является существенным при определении возмущения давления вблизи поверхности; 3) напряжение поверхностного сдвига плохо описывается в большинстве случаев и, в частности, в спутной струе.相似文献
115.
116.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
117.
The semi‐iterative method (SIM) is applied to the hyper‐power (HP) iteration, and necessary and sufficient conditions are given for the convergence of the semi‐iterative–hyper‐power (SIM–HP) iteration. The root convergence rate is computed for both the HP and SIM–HP methods, and the quotient convergence rate is given for the HP iteration. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
118.
A mixed problem is considered for a system of partial differential equations modeling the process of adsorption dynamics. An existence and uniqueness theorem is proved for this problem, and the solution properties are investigated. The inverse problem is posed, involving the determination of the system coefficient given additional information about the solution. A uniqueness theorem is proved for the solution of the inverse problem.__________Translated from Prikladnaya Matematika i Informatika, No. 16, pp. 5 – 14, 2004. 相似文献
119.
In this paper the performances of inhomogeneous dielectric slabs as solar light collectors for both illumination and solar energy applications are analysed. 相似文献
120.
H E Cline W E Lorensen R J Herfkens G A Johnson G H Glover 《Magnetic resonance imaging》1989,7(1):45-54
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting. 相似文献