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   40篇
  免费   0篇
化学   33篇
晶体学   1篇
物理学   6篇
  2023年   1篇
  2017年   1篇
  2016年   1篇
  2013年   5篇
  2012年   3篇
  2011年   3篇
  2009年   2篇
  2008年   2篇
  2005年   3篇
  2004年   3篇
  2003年   4篇
  2000年   1篇
  1991年   1篇
  1989年   1篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1973年   1篇
  1970年   1篇
排序方式: 共有40条查询结果,搜索用时 15 毫秒
1.
In the recycling of poly(vinyl chloride) (PVC), it is required to discriminate every plasticizer for quality control. For this purpose, the near-infrared spectra were measured for 41 kinds of PVC samples with different plasticizers (DINP, DOP, DOA, TOTM and Polyester) and different plasticizer contents (0-49%). A neural-network analysis was applied to the near-infrared spectra pretreated by second-derivative processing. They were discriminated from one another. The neural-network analysis also allowed us to propose a calibration model which predicts the contents of plasticizers in PVC. The correlation coefficient (R) and the root-mean-square error of prediction (RMSEP) for the DINP calibration model were found to be 0.999 and 0.41 wt%, respectively. In comparison, a partial least-squares regression analysis was carried out. The R and RMSEP of the DINP calibration model were calculated to be 0.993 and 1.27 wt%, respectively. It is found that a near-infrared spectra measurement combined with a neural-network analysis is useful for plastic recycling.  相似文献   
2.
Wetting phenomena play important roles in several technological applications and in many physical and biological thin‐film phenomena, such as wetting, adhesion and friction. One of key issues of these studies is to control the surface energy (or wettability) dynamically for liquid transportation. We have developed a liquid crystal (LC) surface for use as a transport substrate since we expected that the surface energy of an LC surface can be controlled rapidly using an electric field. The rapid control of the polarisability (or wettability) of a liquid crystalline surface by an electric field has been demonstrated, together with the transportation of a liquid microdroplet.  相似文献   
3.
A systematic perturbation theory is developed for the ESR shift and is applied to the spin-1/2 Heisenberg antiferromagnetic chain with a general anisotropic exchange interaction. Using the Bethe ansatz technique, the resonance shift is obtained exactly for the whole range of temperature and magnetic field in the first order of the anisotropy. The obtained g shift strongly depends on magnetic fields at low temperature, showing a significant deviation from the previous classical result.  相似文献   
4.
Low density lipoprotein-cholesterol (LDL-c) concentration measured by a homogeneous enzymatic assay was reported to correlate well with the modified beta-quantification assay, especially in samples with high triglyceride (TG) concentration. In this study, we evaluated a homogeneous enzymatic assay, Cholestest-LDL assay system, in hypertriglycemic patient samples, and found that 56% (9/16) of serum samples with intermediate TG concentrations (2.27-4.52 mmol/L) showed more than 10% discrepancy with concentration by the modified beta-quantification assay. Such serum samples originated from patients with hyperglycemia of type II a (three cases), type II b (two cases), type III (one case), and type IV (six cases). Differential staining of cholesterol and triglyceride after agarose gel electrophoresis revealed that these serum samples contained significant amounts of intermediate fractions between pre-beta- and beta-lipoproteins. Since lipoprotein (a), which migrates between pre-beta- and beta-lipoproteins, is not correlated with the discrepancy, we believe the intermediate fraction consists of intermediate density lipoprotein (IDL) and a chylomicron remnant. A part of IDL and chylomicron remnant, which contain a significant amount of triglyceride, might be measured as LDL-c by the homogeneous enzymatic assay, but not by the modified beta-quantification assay.  相似文献   
5.
We synthesized the DNA oligonucleotide containing a new cross-linkable 4-amino-2-oxo-6-vinyltriazine (AOVT) nucleobase analogue (Et-AOVT) and evaluated these properties. Our results of the cross-link assay and thermal denaturing assay of duplexes containing AOVT demonstrated that the additional aza of AOVT has an impact on the duplex stability and crosslink properties. Our data suggests that the additional 5-aza of AOVT is involved in the hydrogen bonding with the complementary guanine, and this hydrogen bonding system successfully flipped the reactive vinyl group out to the major groove of the duplex demonstrating a new paradigm of a “cross-linkable duplex”.  相似文献   
6.
Introducing the fermionic R-operator and solutions of the inverse scattering problem for local fermion operators, we derive a multiple integral representation for zero-temperature correlation functions of a one-dimensional interacting spinless fermion model. Correlation functions particularly considered are the one-particle Green's function and the density–density correlation function both for any interaction strength and for arbitrary particle densities. In particular for the free fermion model, our formulae reproduce the known exact results. Form factors of local fermion operators are also calculated for a finite system.  相似文献   
7.
Iodine and nylon-6 form adducts containing 70–90 wt-% of iodine on heating at 115–145°C. The adducts have electrical conductivities ranging from 10?7 to 10?3 S cm?1 at 25°C, and the electrical conductivity increases with increasing content of iodine of the adduct. The activation energies of the electrical conduction for the adducts prepared at 115°C and containing 69.2, 81.8, 87.1, and 90.0 wt-% of iodine are 94.6, 67.0, 52.9, and 46.1 kJ/mol, respectively. Polyamides other than nylon-6 also form similar semiconducting adducts with iodine. IR and NMR spectroscopic analyses of the iodine—nylon-6 adducts indicate profound changes in the structure of nylon-6 on adduct formation and suggest the formation of a ?CN+H species. The iodine-nylon-6 adducts prepared at 115°C and containing more than 82 wt-% of iodine serve as good active materials of positive electrodes in lithium-iodine solid electrolyte galvanic cells (outer diameter = 11.6 mm; outer thickness = 2.0 mm). The current efficiencies of the galvanic cells at 500 kΩ load are about 50% based on the iodine added. Discharge at 100 kΩ load gives lower current efficiencies. The galvanic cell has an internal resistance of about 5 kΩ at 25°C before discharge, and the internal resistance increases to about 100 kΩ at about 40% discharge. The dependence of the internal resistance during discharge have been determined.  相似文献   
8.
In order to clarify the propagation reaction, vinyl ether was copolymerized with the corresponding alkenyl ether under various conditions. cis-Propenyl ether (cis-PE) was several times more reactive than trans-PE and the corresponding vinyl ether in the copolymerization catalyzed by BF3 · O(C2H5)2 in toluene. However, the reactivity of cis-PE relative to trans-PE and the vinyl ether was found to be greatly decreased with increasing polarity of the solvent and to be very close to unity in such polar solvents as nitroethane. On the other hand, the reactivity of trans-IBPE relative to IBVE was scarcely changed by polymerization conditions. Also, the nature of the initiator and polymerization temperature affect the reactivity of cis-PE relative to the vinyl ether. These phenomena were explained by the relative stability of the bridged and open car bonium ions based on the polarity of the solvent and steric hindrance due to substituents in the trans isomer.  相似文献   
9.
10.
Abstract

Some phosphanyl sugar derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen, were synthesized from 2- and 3-phospholenes as starting materials. Catalytic cis-dihydroxylation of 2-phospholene or 3-phospholene 1-oxide derivatives with osmium(VIII) oxide in the presence of a cooxidant afforded 3-deoxy- or 1-deoxy-tetrofuranose-type phosphanyl sugar derivatives, respectively. cis- Dihydroxylation of 4-acyloxy-2-phospholene 1-oxide derivatives gave tetrofuranose type phosphanyl sugar derivatives. Some of these derivatives of phosphanyl sugars were subjected to structural analyses using 1H NMR and X-ray crystallography.

  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