首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   525篇
  免费   19篇
  国内免费   2篇
化学   410篇
晶体学   2篇
力学   8篇
数学   56篇
物理学   70篇
  2023年   5篇
  2022年   4篇
  2021年   13篇
  2020年   12篇
  2019年   6篇
  2018年   5篇
  2017年   7篇
  2016年   20篇
  2015年   14篇
  2014年   17篇
  2013年   37篇
  2012年   36篇
  2011年   39篇
  2010年   20篇
  2009年   17篇
  2008年   27篇
  2007年   31篇
  2006年   25篇
  2005年   26篇
  2004年   21篇
  2003年   15篇
  2002年   24篇
  2001年   6篇
  2000年   6篇
  1999年   7篇
  1998年   8篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   6篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   7篇
  1988年   3篇
  1987年   6篇
  1986年   4篇
  1985年   7篇
  1984年   2篇
  1982年   9篇
  1981年   2篇
  1980年   8篇
  1979年   8篇
  1978年   6篇
  1976年   2篇
  1975年   3篇
  1973年   1篇
  1970年   1篇
  1966年   1篇
排序方式: 共有546条查询结果,搜索用时 31 毫秒
1.
2.
Jiri Novak   《Optik》2003,114(2):63-68
The presented work offers new algorithms for phase evaluation in interferometric measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. These phase calculation algorithms need to measure five frames of the intensity of the interference field. The algorithms are similarly derived as so called Carré algorithm. The phase evaluation process then does not depend on the linear phase shift errors. Furthermore, the detailed analysis of the algorithms with respect to most important factors, which affect interferometric measurements, is carried out. It is also studied the dependency of the evaluation algorithms on the phase shift values, and the proposed phase calculation algorithms are compared with respect to the resulting phase errors. The influence of most important factors in the measurement and evaluation process was simulated as systematic and random errors using a proposed mathematical model.  相似文献   
3.
4.
5.
Zusammenfassung Es wurde eine theoretische Analyse der kontaktlosen Temperaturmessung des an der Spann-, Trocken- und Fixiermaschine bearbeiteten Gewebes vorgenommen. Der Einfluß der Trocknerwand ist durch die Korrektive Funktion ausgedrückt, zu deren Festlegung ein allgemein anwendbares Diagramm zusammengestellt wurde. Dabei wird die Tatsache berücksichtigt, daß die Messung in einem beschränkten Teil des Spektrums durchgeführt wird, welcher außerhalb der Wasserdampfabsorptionsbänder liegt.
Measuring temperature of textiles in driers with infrared thermometer
The paper undertakes a theoretical analysis of contactless temperature measurement of textiles processed on a stretching, drying and fixation machine. The effect of the drier wall is expressed through a corrective function for whose determination a universal diagram has been established. The measurements have been performed in a narrow part of the spectrum lying outside the water vapour absorption bands.

Formelzeichen B W· m–2 Effektive Wärmestromdichte durch Strahlung - K i Radiationskoeffizient für Oberflächei - q W · m–2 Wärmestromdichte durch Strahlung - T K Temperatur - t °C Temperatur - dtj Kroneckersches Symbol - Emissionsgrad der Oberfläche - m Wellenlänge - ij Radiationskoeffizient - T W·m –2 ·K –4 Koeffizient in der Gleichung (2) - Winkelkoeffizient für Strahlung zwischen Oberflächen 1, 2 - – Korrektionsfunktion - W·m –2 Wärmestromdichte des schwarzen Körpers Indizes c Gewebe - M Meßwert - w Trocknerwand  相似文献   
6.
Radiation-chemical transformations of chloride solutions in the presence of iodide additives were studied by pulse radiolysis. Radical anion Cl2 ⋅− oxidize I ion, while in the secondary reactions Cl2 reacts with I to form a mixed trihalide ion ICl2 . A reaction model that satisfactorily describes the experimental data was proposed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1336–1340, June, 2005.  相似文献   
7.
Uranium is determined via its 239U nuclide (74.0 keV, t12 = 23.5 min) in natural waters down to 0.03 ng U ml-1 after preconcentration with activated carbon and oxine; 30-min irradiation and counting times are used. No preconcentration is required for samples containing more than 4 ng U ml-1 with 10-min irradiation and counting times. Uranium in urine can be determined under a boron shield at the 5 ng ml-1 level after 30-min irradiation and counting.  相似文献   
8.
Summary. The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed. Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found at 135°C.  相似文献   
9.
Ab initio investigations at the RHF and CI levels have been carried out on a section of the potential energy surface of the Rydberg 3s3A″2 state of NH3 leading to dissociation into NH2(2B1) and H(2S). It was found that the barrier towards dissociation is due to a Rydberg-valence transformation. The barrier height calculated with the CI wavefunction is significantly smaller than at the RHF level The results may explain the difficulties associated with experimental observation of the 3s3A″2 state.  相似文献   
10.
Laser-pulse transient measurements have been performed at single crystalline n-PtS2 electrodes with the aim of understanding light-induced hydroxide, oxide and oxygen formation. Different detected time constants permit the identification of distinct reaction products. They form surface states which function both as centers for recombination and charge accumulation in the interface. The rate constants determined are influenced by the RC-constant of the measuring circuit and can be interpreted only qualitatively. In the presence of recombination processes time constants faster than RLCSC are found. Evidence is given that the reaction step leading to oxygen evolution is dependent on the building-up of an electric field in the Helmholtz layer. This result may be of importance for the development of materials for the photoelectrolysis of water.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号