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   157篇
  免费   1篇
化学   115篇
晶体学   5篇
力学   7篇
数学   17篇
物理学   14篇
  2022年   2篇
  2021年   5篇
  2020年   3篇
  2019年   3篇
  2018年   1篇
  2017年   3篇
  2016年   3篇
  2015年   3篇
  2014年   4篇
  2013年   14篇
  2012年   4篇
  2011年   4篇
  2010年   4篇
  2009年   4篇
  2008年   6篇
  2007年   5篇
  2006年   5篇
  2005年   1篇
  2004年   4篇
  2003年   8篇
  2002年   8篇
  2001年   2篇
  1999年   3篇
  1998年   2篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   4篇
  1990年   3篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1983年   4篇
  1982年   2篇
  1981年   3篇
  1979年   1篇
  1975年   1篇
  1971年   1篇
  1969年   1篇
  1967年   3篇
  1961年   1篇
排序方式: 共有158条查询结果,搜索用时 15 毫秒
21.
A paper spray ion source was combined with a drift tube operating at ambient pressure for mobility measurements of ions derived from pharmaceutical solutions. Paper spray ionization with solvent alone resulted in a mixture of ions convolved to a single peak with a reduced mobility of 2.19 cm2/Vs in the mobility spectrum. These were mass-identified principally as m/z 157, (MeOH)2(HCOOH)2H+ and m/z 129, (MeOH)4(H2O)H+ while pharmaceuticals with nitrogen bases formed MH+ product ions. The duration of response was governed by the volume of liquid added to the paper source and was limited by evaporation of solvent in gas at 58 °C venting the drift tube. Quantitative variation was attributed in part to morphologic changes in the tip of the paper spray source. This was associated with mass flow in the electrical discharge and not due alone to cycles of wetting and drying of the paper. Mobility spectra of chlorpromazine in urine, exhibited a single product ion peak and linear response was 30 to 500 ng with an estimated limit of detection of 1.5 ng. Ion flux could be prolonged by continuous addition of liquid and findings portend a combination of paper spray ionization IMS with paper chromatography.  相似文献   
22.
Quadrupole coupling constants of Co59 has been measured in several octahedral cobaltic complexes. The compounds are diamagnetic and polycrystalline in nature. The magnitudes of the coupling constants were evaluated assumingη as zero. The temperature variation of the coupling constants are correlated with the nature of Co-ligand bond and molecular motions in the solid.  相似文献   
23.
The preparation and initial in vitro evaluation of a series of potent arachidonate epoxygenase inhibitors and heteroatom analogues of epoxyeicosatrienoic acid are described.  相似文献   
24.
Polycrystalline ceramic YIG has been synthesized with submicron microstructure. The log-log plot of FMR linewidth versus average grain size gives a power law dependence α-10 where α0 is the average grain size. The instability threshold hcrit for increasing magnetic field vector of the microwave parallel pump shows a linear log-log dependence with average grain size.  相似文献   
25.
In this article, we construct a commutative unital Banach algebra, in which the property 6a26=6a62 is true for the invertible elements, but cannot be extended to the whole algebra.  相似文献   
26.
Synthetic dyes are released into the environment from textile industrial effluents. The discharge of this colored wastewater into rivers and lakes leads to a reduction in sunlight penetration in natural water bodies, which, in turn, decreases both photosynthetic activity and dissolved oxygen concentration and is toxic to living beings. Bacterial isolates are optimized for growth and biomass production before using them for decolorizing dye effluent. The bacterial isolates Bacillus sp. 1 and Bacillus sp. 2 were employed at different percentages by volume with standard nutrient concentration. Of these bacterial isolates Bacillus sp. 2 recorded maximum color reduction. The pH and electrical conductivity (EC) were reduced in the decolorized effluent, and a reduction in biologic oxygen demand, chemical oxygen demand, total suspended solids, and total dissolved solids (TDS) were also observed.  相似文献   
27.
Methylene blue sensitized photopolymerization of acrylamide (AM) and methyl methacrylate (MMA) using triethanolamine or the sodium salt of EDTA as a reducing agent has been investigated under the influence of a magnetic field (0–7.3 kG). There was no effect of the magnetic field (MF) on the polymerization of AM and MMA in aqueous medium. However, in the water–methanol mixture (1 : 1) the yield of polymer decreases and the molecular weight increases in both cases under MF. This has been explained on the basis of the triplet mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1509–1513, 1998  相似文献   
28.
The FeCl3-promoted oxidative cyclization/coupling of acetamidostilbenes possessing 3-methoxy, 4-methoxy and 3,5-methoxy substitutions (21), (22) and (23) is described. Only 3,5-substitution gave rise to novel indolostilbenes, each possessing two stereogenic axes (axially chiral but racemic dimers (39) and (40)). The 4-methoxy substituted acetamidostilbenes, by contrast, yielded the bisindoline dimer (36).  相似文献   
29.
In this paper, we present an efficient algorithm to find next-to-shortest path between any pair of vertices u,v on permutation graphs with n vertices which runs in O(n 2) time.  相似文献   
30.
The formation and dissociation of methane gas hydrate at an interface between synthetic seawater (SSW) and methane gas have been experimentally investigated in the present work. The amount of gas consumed during hydrate formation has been calculated using the real gas equation. Induction time for the formation of hydrate is found to depend on the degree of subcooling. All the experiments were conducted in quiescent system with initial cell pressure of 11.14 MPa. Salinity effects on the onset pressure and temperature of hydrate formation are also observed. The dissociation enthalpies of methane hydrate in synthetic seawater were determined by Clausius-Clapeyron equation based on the measured phase equilibrium data. The dissociation data have been analyzed by existing models and compared with the reported data.  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