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   745篇
  免费   19篇
  国内免费   2篇
化学   497篇
晶体学   8篇
力学   17篇
数学   32篇
物理学   212篇
  2020年   9篇
  2019年   12篇
  2018年   10篇
  2017年   9篇
  2016年   9篇
  2015年   7篇
  2014年   26篇
  2013年   41篇
  2012年   23篇
  2011年   33篇
  2010年   15篇
  2009年   18篇
  2008年   38篇
  2007年   35篇
  2006年   32篇
  2005年   34篇
  2004年   44篇
  2003年   29篇
  2002年   28篇
  2001年   20篇
  2000年   35篇
  1999年   14篇
  1998年   11篇
  1997年   8篇
  1996年   6篇
  1995年   7篇
  1994年   14篇
  1993年   3篇
  1992年   13篇
  1991年   10篇
  1990年   5篇
  1989年   4篇
  1987年   7篇
  1986年   7篇
  1985年   12篇
  1984年   12篇
  1983年   8篇
  1982年   6篇
  1981年   15篇
  1980年   14篇
  1979年   16篇
  1978年   11篇
  1977年   14篇
  1976年   10篇
  1975年   5篇
  1974年   6篇
  1973年   2篇
  1972年   3篇
  1971年   3篇
  1970年   2篇
排序方式: 共有766条查询结果,搜索用时 31 毫秒
71.
72.
Preferential sorptions and pervaporation selectivities in poly (vinyl chloride) (PVC) membrane for various binary liquid mixtures were investigated. Methanol/n-propanol, benzene/n-hexane, and ethanol/water mixtures were selected as the binary liquid mixture. In the methanol/n-propanol mixture, methanol was preferentially sorbed in the PVC membrane and predominantly permeated. In the benzene/n-hexane mixture, benzene was incorporated and permeated preferentially. In the ethanol/water mixture, ethanol was preferentially sorbed in the PVC membrane and water was preferentially permeated. The preferential sorptions were analyzed according to Mulder's model derived from Flory-Huggins thermodynamics. The pervaporation selectivity in these systems were discussed using a sorption selectivity and diffusion selectivity. © 1995 John Wiley & Sons, Inc.  相似文献   
73.
Based on the stratigraphically well sorted material from Japan and southern Sakhalin, the ammonoid species belonging to the genus Desmoceras are classified as follows in ascending order: D. latidorsatum (Michelin) (Middle to mid-Upper Albian), D. dawsoni shikokuense (Yabe and Shimizu) (Upper Albian), D. kossmati Matsumoto (uppermost Albian–Lower Cenomanian), D. japonicum Yabe (uppermost Albian–Cenomanian), and D. ezoanum Matsumoto (mid-Upper Cenomanian–mid-Lower Turonian). D. japonicum can be subdivided into the earlier and later subspecies. D. poronaicum Yabe is a junior synonym of D. japonicum. Despite the scarcely ornamented shell, each taxon can be defined by its own characters.  相似文献   
74.
A relationship between the structure and water purifying ability of waste glass prepared from household garbage and Fe2O3 was examined by 57Fe-Mössbauer and induced coupled plasma (ICP) measurements. From the Debye temperature of waste glass, FeII proved to be loosely bound in the glass network as a network modifier. Dissolution amount of FeIII into artificial drain can be controlled from 0.14 to 0.35 mg/l by changing the Fe2O3 content. It proved that chemical oxygen demand (COD) decreases in proportion to the content of FeIII, indicating that iron causes decomposition of organic and phosphorus compounds.  相似文献   
75.
Grazing-exit x-ray fluorescence (GE-XRF) and micro x-ray fluorescence (micro-XRF) methods were applied to chemical microchips as a detection method. Since an energy-dispersive x-ray detector was used, the simultaneous detection of multiple elements was possible. An analyzing region was especially designed on the microchip so that a sample solution could be dried and concentrated in a suitable area corresponding to the size of the primary x-ray beam. Finally, it was confirmed that both analytical methods could be combined well for use with a microchip. In GE-XRF, the background intensity in the XRF spectrum was reduced at grazing-exit angles. In addition, a good relationship between the x-ray fluorescence intensities and the concentrations of standard solutions that were introduced into the microchip was obtained. This indicates that the GE-XRF method is feasible for trace elemental analysis in chemical microchip systems. In micro-XRF, an attempt was made to concentrate and dry the analyte within a small analyzing region. The preliminary results indicated that the micro-XRF method could be applied for the analysis of microchips.  相似文献   
76.
77.
78.
A branch-and-bound algorithm to solve 0–1 parametric mixed integer linear programming problems has been developed. The present algorithm is an extension of the branch-and-bound algorithm for parametric analysis on pure integer programming. The characteristic of the present method is that optimal solutions for all values of the parameter can be obtained.  相似文献   
79.
The copper(II) complex with N,N-bis(2-benzimidazolylmethyl)benzylamine has been synthesized and its crystal structure was determined by X-ray diffraction methods.  相似文献   
80.
A technique for the blood volume measurement of newborns was established in which nonradioactive 50Cr was used in patients for whom radioactive labels were not advisable. The red blood cells (RBC) in the newborn's blood withdrawn from umbilical cord after birth were tagged with enriched stable isotope 50Cr (96%, normal abundance 4.3%) and reinjected into the newborn. Blood samples (0.5 ml) were withdrawn at 30 min and thereafter at 6, 12, 24, 48, 72 and 120 hours old. Samples were centrifugalized and portion of RBC was then freeze-dried, weighed and sealed into polyethylene sheet bag together with 50Cr standard. Neutron irradiation was performed in the reactors of the JAERI with thermal neutron flux 5 X 10(13), 2 X 10(13), 8 X 10(13) cm-2s-1 at JRR-2, -3 and -4 respectively for 20 min and samples were left for about two weeks after irradiation. Induced radioactivity (51Cr, 59Fe) of the sample was measured with a Ge(Li) gamma-ray detector system and 4096 channels pulse height analyzer. Analysis of activity data was carried out by BOB-76 code. The RBC and total blood volume of the newborn was calculated using an isotopic dilution technique. We have investigated on tagging efficiency of 50Cr to RBC, washing effect and dilution rate by 50Cr content or 51Cr/59Fe ratio. Significant difference was observed in the total blood volume of newborns depending on the delivery style and in addition, it changed dynamically along the time elapsed after birth.  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