全文获取类型
收费全文 | 1826篇 |
免费 | 60篇 |
国内免费 | 10篇 |
专业分类
化学 | 1146篇 |
晶体学 | 31篇 |
力学 | 65篇 |
数学 | 283篇 |
物理学 | 371篇 |
出版年
2021年 | 15篇 |
2020年 | 22篇 |
2019年 | 14篇 |
2016年 | 40篇 |
2015年 | 39篇 |
2014年 | 26篇 |
2013年 | 76篇 |
2012年 | 72篇 |
2011年 | 96篇 |
2010年 | 36篇 |
2009年 | 37篇 |
2008年 | 60篇 |
2007年 | 85篇 |
2006年 | 87篇 |
2005年 | 86篇 |
2004年 | 68篇 |
2003年 | 78篇 |
2002年 | 72篇 |
2001年 | 47篇 |
2000年 | 49篇 |
1999年 | 34篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 33篇 |
1995年 | 20篇 |
1994年 | 31篇 |
1993年 | 28篇 |
1992年 | 35篇 |
1991年 | 42篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1986年 | 20篇 |
1985年 | 28篇 |
1984年 | 32篇 |
1983年 | 21篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 17篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1976年 | 13篇 |
1975年 | 22篇 |
1974年 | 18篇 |
1973年 | 15篇 |
1972年 | 11篇 |
1971年 | 15篇 |
1969年 | 11篇 |
1968年 | 11篇 |
排序方式: 共有1896条查询结果,搜索用时 15 毫秒
161.
Periodic vertical modulations of the sulphur concentration have been observed in epitaxial layers of ZnSe1? x S x grown by metal-organic vapour-phase epitaxy. High-spatial-resolution microanalysis has shown that the sulphur variation is of the order of 1 at.% with a period of about 44 ± 0.1 nm. A detailed analysis of the possible causes of this modulation is presented which shows that periodic temperature fluctuations of the substrate are the most likely source. 相似文献
162.
Gloria Dion Anne Harvey Carol Jackson Patricia Klag Jinghua Liu Craig Wright 《School science and mathematics》2001,101(8):427-438
This survey investigated the current status of calculator use in classrooms and schools. The results indicated that the prevailing policy in the sample of high schools is to allow the use of calculators during classroom learning activities and tests. Scientific calculators are more frequently used than graphing calculators in algebra I and geometry; whereas, graphing calculators are more frequently used in algebra II and precalculus/trigonometry. At the time of this survey, school policies regarding the use of graphing calculators with symbolic algebra capabilities were still not determined. 相似文献
163.
164.
Peter R. Griffiths Kenneth W. Van Every Norman A. Wright 《Fresenius' Journal of Analytical Chemistry》1986,324(6):571-578
Summary Two techniques for measuring the infrared spectra of adsorbed species on surfaces of different types are described. Diffuse reflectance spectra of species adsorbed on powdered substrates with a high surface area can be measured with an exceptionally high signal-to-noise ratio. The technique is illustrated by the adsorption of carbon monoxide on rhodium supported on alumina at metal loadings between 0.1 and 10%. Some doubt is cast on previous band assignments for adsorbed CO molecules. Grazing incidence reflection-absorption spectrometry can be used to measure the spectra of molecules on flat metallic substrates of very low surface area. Attempts to develop a technique for observing the intermolecular vibration between the adsorbate and the substrate using a unique triple modulation approach are discussed.
FT-IR-Spektrometrie mit diffuser Reflexions- und Polari-sations-Modulation von Adsorbaten an Oberflächen
Zusammenfassung Zwei Techniken zur Messung von Infrarot-Spektren von Adsorbaten verschiedener Art werden beschrieben. Diffuse Reflexionsspektren von Adsorbaten an pulverförmigen Substraten mit einer großen Oberfläche können mit einem außerordentlich großen Signal-zu-RauschVerhältnis gemessen werden. Als Beispiel dient die Adsorption von Kohlenstoffmonoxid an Rhodium auf Aluminiumoxid bei Metallgehalten von 0,1 bis 10%. Einige Zweifel an früheren Bandzuweisungen für adsorbierte CO-Moleküle werden geäußert. Reflexions-Absorptions-Spektrometrie mit streifendem Einfall kann zur Messung der Spektren von Molekülen an flachen metallischen Substraten mit sehr geringer Oberfläche benutzt werden. Versuche zur Entwicklung einer Technik für die Beobachtung der intermolekularen Schwingungen zwischen dem Adsorbaten und dem Substrat mittels einer einzigartigen Dreifach-Modulationstechnik werden diskutiert.相似文献
165.
166.
A. Panchaud C. Reichard N. A. Orlow E. Gabutti Anton Altan Wald Hille H. M. Gordin W. Bickern Albert Beitter Georg Heyl H. F. Moschkowitsch Léger Farr Wright Barral Garsed Ed. Dowzard E. Rupp O. Schweissinger Busse Fränkel und Karl Dieterich 《Fresenius' Journal of Analytical Chemistry》1907,46(6-7):463-476
Ohne Zusammenfassung 相似文献
167.
Wm. Lerch R. H. Bogue E. S. Shepherd G. A. Rankin F. E. Wright F. Ferrari J. Stanton Pierce W. C. Setzer F. Strumpf und R. H. H. Stanger 《Fresenius' Journal of Analytical Chemistry》1930,81(12):476-480
Ohne Zusammenfassung 相似文献
168.
S. Banerjee S. N. Ganguli A. Gurtu R. Raghavan K. Shankar Y. Goldschmidt-Clermont R. T. Ross S. Squarcia K. Dziunikowska T. Haupt P. Girtler D. Kuhn G. Koul Devanand P. V. K. S. Baba Gian Singh K. W. J. Barnham J. Wells P. R. S. Wright F. Mandl M. Markytan M. Bardadin-Otwinowska M. Szczekowski 《Zeitschrift fur Physik C Particles and Fields》1986,31(3):409-416
Results are presented on inclusive production of ∑+(1385) and ∑?(1385) inK ? p interactions at 110 GeV/c. The inclusive and topological cross sections have been estimated and compared with published results at lower energies. The inclusive cross section of ∑+(1385) seems to decrease with c.m. energy, while that of the ∑?(1385) is nearly constant. The mean charged multiplicity associate to Σ(1385) increases with c.m. energy. The ∑+(1385) is produced both in the target fragmentation region and in the central region where ∑?(1385) is predominantly produced in the central region. Approximately 16% of the Λ's stem from the decay of ∑±(1385) and the kinematic distributions of these Λ's are not very different from the inclusive Λ's. 相似文献
169.
The coagulation frequency is the key ingredient in the population balance (Smoluchowski) equation of coagulation kinetics. An inverse problem is formulated to extract the coagulation frequency from transient size distributions when these distributions are self-similar. Two numerical examples illustrate the procedure. The first demonstrates the inverse problem for the recovery of singular coagulation frequencies, while the second shows the procedure when self-similarity is approximate. Transient droplet coagulation experiments in a turbulent flow field have been performed. The resulting size distributions are observed to be self-similar. The inverse problem is used to determine the drop coagulation frequency. This frequency shows significant deviation from the coagulation frequencies derived from simple models of drop-drop interactions in a turbulent flow field. 相似文献
170.