全文获取类型
收费全文 | 1283996篇 |
免费 | 32021篇 |
国内免费 | 9027篇 |
专业分类
化学 | 642834篇 |
晶体学 | 20064篇 |
力学 | 73613篇 |
综合类 | 101篇 |
数学 | 238124篇 |
物理学 | 350308篇 |
出版年
2021年 | 13635篇 |
2020年 | 16726篇 |
2019年 | 17724篇 |
2016年 | 28027篇 |
2015年 | 21684篇 |
2014年 | 31551篇 |
2013年 | 75829篇 |
2012年 | 35311篇 |
2011年 | 29145篇 |
2010年 | 35902篇 |
2009年 | 38948篇 |
2008年 | 29895篇 |
2007年 | 24122篇 |
2006年 | 32515篇 |
2005年 | 23949篇 |
2004年 | 26419篇 |
2003年 | 25707篇 |
2002年 | 27688篇 |
2001年 | 24970篇 |
2000年 | 22910篇 |
1999年 | 21481篇 |
1998年 | 20558篇 |
1997年 | 20612篇 |
1996年 | 20900篇 |
1995年 | 19024篇 |
1994年 | 18440篇 |
1993年 | 17962篇 |
1992年 | 17466篇 |
1991年 | 17814篇 |
1990年 | 17043篇 |
1989年 | 17144篇 |
1988年 | 16683篇 |
1987年 | 16738篇 |
1986年 | 15618篇 |
1985年 | 22091篇 |
1984年 | 23479篇 |
1983年 | 19751篇 |
1982年 | 21500篇 |
1981年 | 20754篇 |
1980年 | 20079篇 |
1979年 | 20085篇 |
1978年 | 21506篇 |
1977年 | 21055篇 |
1976年 | 20715篇 |
1975年 | 19383篇 |
1974年 | 19011篇 |
1973年 | 19489篇 |
1972年 | 14014篇 |
1968年 | 11890篇 |
1967年 | 12269篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Lithium (10–150 ng ml?1) in wine is determined by atomic absorption spectrometry by direct nebulization and after digestion with mixed acids. The results of methods are similar. Thirty-four wines from various Spanish provinces are analysed. 相似文献
992.
993.
994.
Dr. H. Schmieg Prof. Dr. P. Vielsack 《Archive of Applied Mechanics (Ingenieur Archiv)》1987,57(6):446-458
Übersicht Betrachtet wird ein zwangserregtes Zweikörpersystem mit wechselnden Bindungen infolge trockener Reibung. Stationäre Bewegungen werden als Grenzfall instationärer Einschwingvorgänge berechnet. Abhängig von den Systemparametern ergeben sich drei typische Bewegungsformen. Ihnen entsprechen dauernde Haftzustände, wechselnde Haft-Gleitzustände oder dauernde Gleitzustände an der Berührfläche beider Körper.
Intermittant constraints in a two-body-system with dry friction
Summary An externally excited two-body-system with intermittant constraints due to dry friction is considered. Stationary motions are calculated as limit cases of instationary transients. Depending on the parameters of the system, three typical modes are of interest. These correspond to permanent sticking, slipstick behaviour, or to permanent slipping in the contact surface of the bodies, respectively.相似文献
995.
996.
997.
Capillary Electrophoresis Chiral Separation for Enantiomeric Purity Determination of a Basic Drug in Pharmaceutical Formulations 总被引:1,自引:0,他引:1
Capillary electrophoresis using a running buffer composed of β-cyclodextrin as the chiral selector and ethanolamine mesylate at pH 9.6 is being used to monitor the stereochemical stability of a hydrophobic drug, containing two chiral centers, in two different formulated self-emulsifying drug delivery system (SEDDS) products. The separation takes place in less than 25 min. Strategies for enhancing the method reproducibility and detection sensitivity in the lower potency formulation are presented. The results demonstrating the specificity, assay precision, recovery, linearity and range achieved during the method validation experiments are presented in this paper.Presented at: CE in the Biotechnology and Pharmaceutical Industries: 7th Symposium on the Practical Applications for the Analysis of Proteins, Nucleotides and Small Molecules, Montreal, Canada, August 12–16, 2005. 相似文献
998.
We study matter-wave solitons in Bose-Einstein condensates of ultracold gaseous atoms with spin degrees of freedom and present a class of exact solutions based on the inverse scattering method. The one-soliton solutions are classified with respect to the spin states. We analyze collisional effects between solitons in the same or different spin state(s), which reveals a very interesting possibility: we can manipulate the spin dynamics by controlling the parameters of colliding solitons. 相似文献
999.
1000.
The acoustic field inside a shell excited by a spatially inhomogeneous harmonic pressure field is studied. The shell is assumed
to have a finite length, a set of orthogonal stiffening ribs, two ends bounding the acoustic volume, and a sound-insulating
structure, which includes layers of sound-insulating material, resonant elements, and an interior panel. The shell is considered
to be orthotropic with boundary conditions corresponding to a free support. For the acoustic field in the closed volume, analytical
expressions are derived with allowance for the elastoacoustic interaction of the shell with the sound-insulating layers and
with the medium both inside the shell (with arbitrary impedance values at the ends) and outside it. These expressions are
used to investigate the effect of different types of resonant systems on the sound field inside the shell. 相似文献