全文获取类型
收费全文 | 331674篇 |
免费 | 3047篇 |
国内免费 | 933篇 |
专业分类
化学 | 166382篇 |
晶体学 | 5376篇 |
力学 | 15531篇 |
综合类 | 7篇 |
数学 | 38480篇 |
物理学 | 109878篇 |
出版年
2021年 | 3134篇 |
2020年 | 3335篇 |
2019年 | 3760篇 |
2018年 | 5201篇 |
2017年 | 5442篇 |
2016年 | 7373篇 |
2015年 | 4146篇 |
2014年 | 7033篇 |
2013年 | 15925篇 |
2012年 | 12470篇 |
2011年 | 15069篇 |
2010年 | 11076篇 |
2009年 | 10939篇 |
2008年 | 13416篇 |
2007年 | 13374篇 |
2006年 | 12308篇 |
2005年 | 10695篇 |
2004年 | 9964篇 |
2003年 | 8791篇 |
2002年 | 8761篇 |
2001年 | 10443篇 |
2000年 | 7710篇 |
1999年 | 5978篇 |
1998年 | 4985篇 |
1997年 | 4819篇 |
1996年 | 4488篇 |
1995年 | 3872篇 |
1994年 | 3829篇 |
1993年 | 3706篇 |
1992年 | 4101篇 |
1991年 | 4313篇 |
1990年 | 4099篇 |
1989年 | 4011篇 |
1988年 | 3785篇 |
1987年 | 3920篇 |
1986年 | 3689篇 |
1985年 | 4631篇 |
1984年 | 4683篇 |
1983年 | 3888篇 |
1982年 | 3973篇 |
1981年 | 3698篇 |
1980年 | 3649篇 |
1979年 | 3913篇 |
1978年 | 3902篇 |
1977年 | 3907篇 |
1976年 | 3881篇 |
1975年 | 3675篇 |
1974年 | 3619篇 |
1973年 | 3650篇 |
1972年 | 2604篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
S. Ebel B. Reyer und A. Werner-Busse 《Fresenius' Journal of Analytical Chemistry》1987,327(2):193-197
Summary This paper describes a reliable working station for the in line-process control in chemical plants. Essential parts of the equipment (pump, column) are in duplicates and may be combined by computer control in different lines. One pump and column is in working position, the other is held in ready to work position by conditioning. While one column is in working position, the system is able to calibrate the other column and to switch to this column in the case of breakdown of the other column. By means of chromatographic data (as retention time, peak height of standards, data of separation) the working column is under control and the switching to the other column is down before a real breakdown. The status of the detector is followed by number and distance in time of the necessary auto-zero operations and by the noise of the lamp.
Herrn Prof. Dr. W. Fresenius aus Anlaß des 125jährigen Erscheinens der Fresenius Zeitschrift für Analytische Chemie gewidmet 相似文献
Herrn Prof. Dr. W. Fresenius aus Anlaß des 125jährigen Erscheinens der Fresenius Zeitschrift für Analytische Chemie gewidmet 相似文献
982.
Complex dielectric spectroscopy (frequency range 5 Hz-13 MHz) has been used to analyse the frequency, temperature and bias-field dependences of the molecular dynamics of a very high-spontaneous-polarization ferroelectric liquid crystalline material exhibiting SmA, SmC* and unknown SmX smectic phases. Different smectic phase transition temperatures have been observed from the study of the temperature dependence of the dielectric strength and the relaxation frequency. The phase transition temperatures (crystalline to isotropic phases) have also been described very accurately from the temperature-dependent symmetric and asymmetric shape parameters of the relaxation function and also the dc conductivity. In a planar aligned cell, two symmetric modes (Goldstone mode and domain mode) have been observed in both the SmX and SmC* phases. One asymmetric mode (X-mode) observed in the SmC* and SmA phases could be related to the interaction of dipoles of the ferroelectric liquid crystals being affected by the surface of the cell. The soft mode, which usually appears very close to the SmC*-SmA phase transition was not observed until the bias field was applied. The second order nature of the SmC*-SmA phase transition was revealed. 相似文献
983.
S.B. Lyubchik L.P. Tikhonova O.L. Galushko I.M. Fonseca 《Applied Surface Science》2006,252(17):6084-6088
Selective adsorption of platinum group metals (PMG) on activated carbons from a multi-component model and technological solutions was proposed for the preparation of heterogeneous-supported catalysts. Activated natural anthracites and a nitrogen-containing synthetic carbon are considered as carriers for Pd-supported catalysts. Their catalytic activity was studied in the Pd-catalyzed reactions of hydrogen peroxide decomposition and chloride ions oxidation by manganese(III). On the base of the obtained results, novel high sensitive analytical methods both for direct determination of supported-metal quantity and palladium oxidation states on the surface of spent adsorbents are suggested. 相似文献
984.
S. V. Usachev A. S. Osipov G. I. Kostrykina T. I. Irkhina N. B. Tantsova E. G. Fedorova 《Russian Journal of Applied Chemistry》2006,79(11):1890-1895
Variation of the molecular structure characteristics and properties of natural and 1,4-cis-polybutadiene rubbers (gel content, molecular weight, degree of branching of macromolecules, viscosity) in the course of their separate and joint mastication in the presence of dibenzoylaminodiphenyl sulfide as mastication accelerator or without it was studied. 相似文献
985.
M. Mahjour-Shafiei H.R. Amir-Ahmadi J.C.S. Bacelar R. Castelijns K. Ermisch E.D. van Garderen I. Gašparić M.N. Harakeh N. Kalantar-Nayestanaki M. Kiš H. Löhner O. Scholten 《Physics letters. [Part B]》2006
A series of nucleon–nucleon bremsstrahlung (NNγ) experiments at 190 MeV incident beam energy have been performed at KVI in order to gain more insight into the dynamics governing the bremsstrahlung reaction. After initial measurements wherein the bremsstrahlung process was studied far away from the elastic limit, a new study was used to probe the process nearer to the elastic limit by measuring at lower photon energies. Measured cross sections and analyzing powers are compared with the predictions of a microscopic model and those of two soft-photon models. The theoretical calculations overestimate the data by up to ≈30%, for some kinematics. 相似文献
986.
T. Geppert S.L. Schweizer U. Gösele R.B. Wehrspohn 《Applied Physics A: Materials Science & Processing》2006,84(3):237-242
We present a method to create at the same time trenches and ordered macropore arrays during photo-electrochemical etching of n-type silicon. This novel method allows in situ separation of single devices with a submicrometer precision. It also enables new device structures in macroporous silicon in the areas of photonics, sensing and electronics. The limits of this new process are simulated using electrostatic models and are verified experimentally. PACS 82.45.Yz; 81.16.-c 相似文献
987.
Yu. S. Denishchik 《Journal of Applied Spectroscopy》1989,51(5):1167-1170
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 5, pp. 777–781, November, 1989. 相似文献
988.
989.
990.
I. N. Flerov V. D. Fokina M. V. Gorev A. D. Vasiliev A. F. Bovina M. S. Molokeev A. G. Kocharova N. M. Laptash 《Physics of the Solid State》2006,48(4):759-764
Precision studies of the thermophysical properties and structure of an (NH4)2WO2F4 crystal have been performed. It was established reliably that there is a sequence of two phase transitions at T 1 = 201 K and T 2 = 160 K characterized by wedging out of an intermediate phase with an increase in pressure. The role of tetrahedral and octahedral ionic groups in the mechanism of the structural transitions was determined. 相似文献