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   145篇
  免费   5篇
化学   95篇
晶体学   1篇
力学   1篇
数学   19篇
物理学   34篇
  2023年   2篇
  2022年   4篇
  2021年   1篇
  2020年   3篇
  2019年   7篇
  2018年   9篇
  2017年   6篇
  2016年   9篇
  2015年   1篇
  2014年   9篇
  2013年   12篇
  2012年   15篇
  2011年   10篇
  2010年   9篇
  2009年   4篇
  2008年   12篇
  2007年   2篇
  2006年   4篇
  2005年   2篇
  2004年   2篇
  2003年   5篇
  2001年   1篇
  1999年   3篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
排序方式: 共有150条查询结果,搜索用时 15 毫秒
71.
Molecular interactions have been studied for adsorption of certain biomolecules in aqueous solutions using two different types of polymeric resins as adsorbents. Molecular modeling study is based on molecular orbital theory. Adsorption affinity expresses as the slope of the linear region of the isotherm for a solute is found to be different for different adsorbents, and this difference can be interpreted from the differences in sorbent surface chemistry and morphological structure. The adsorptive interaction on the polymeric resins computed on the basis of frontier orbital theory seems to correlate well with the experimentally measured adsorption affinity. Electronic states of adsorbent and adsorbate were calculated using the semiempirical molecular orbital (MO) method from which energy of adsorption in aqueous solution was estimated. It was found that charge transfer interaction plays an important role in the adsorption of certain biomolecules on aqueous solution. The experimentally measured enthalpy of adsorption seems to correlate well with the adsorptive interaction energy computed from molecular orbital theory.  相似文献   
72.
The reaction of 16-DPA with P4S10 in refluxing benzene afforded a novel adduct 16-DPA-P2S5 instead of the expected thione. The adduct undergoes [4+2]cycloaddition with alkyne dienophiles to afford steroidal (17,16-c)pyrans.  相似文献   
73.
JPC – Journal of Planar Chromatography – Modern TLC - A sensitive and reliable high-performance thin-layer chromatography (HPTLC) method has been developed to simultaneously estimate...  相似文献   
74.
The ability of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2‐cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS‐b‐PVDM and PMA‐b‐PVDM well‐defined block copolymers can be prepared either by polymerization of VDM from PS‐ and PMA‐macroCTAs, respectively, or polymerization of S and MA from a PVDM‐macroCTA. In contrast, PMMA‐b‐PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010  相似文献   
75.
An alloyed complex of zinc, sulphur and selenium was synthesized in a controlled fashion using 3-mercaptopropionic acid (MPA) surfactant to obtain a new class of biocompatible, highly luminescent imaging probes. These ZnSe(S) alloyed quantum dots (QDs) exhibited a five fold enhancement in photoluminescence over the native ZnSe nanocrystals. The enhancement in photoluminescence was brought about without any post-preparative surface treatments, under ambient conditions. 3-mercaptopropionic acid (MPA) was found to optimally stabilize the ZnSe(S) alloyed system. The incorporation of S2? from MPA after prolonged refluxing time enabled the formation of ZnSe(S) alloyed QDs with low cytotoxicity. The in vitro assays revealed the synergistic enhancement of photoluminescence with enhancement in dispersibility and high biocompatibility for the ZnSe(S) system. The experimental findings give us a novel range of blue-emitting, Zn-based high luminescence QDs for development of nano-probes for bioimaging applications.  相似文献   
76.
In this paper, we establish several theorems for the explicit evaluations of Ramanujan-G?llnitz-Gordon continued fraction by using some parameterizations of Ramanujan’s theta-functions. Nayandeep Deka Baruah, Corresponding author. Research partially supported by grant SR/FTP/MA-02/2002 from DST, Govt. of India. Authors’ address: Nayandeep Deka Baruah and Nipen Saikia, Department of Mathematical Sciences, Tezpur University, Napaam-784028, Assam, India  相似文献   
77.
Tetrahydrothiopyrans have been efficiently synthesized in good yields with excellent diastereoselectivity from aldehydes and substituted 5-methylhex-4-ene-1-thiol via (3,5)-thionium-ene cyclization reaction mediated by boron trifluoride etherate.  相似文献   
78.
Hydrolysis of ZnO in acidic pH provides a facile route for synthesis of layered double hydroxides (LDH) bearing Zn2+ with Cr3+ and Al3+ without having carbonate ion in the inter-layer position. The thermal decomposition of the prepared LDH show that with the increase of Cr3+ content in the system there is an increase in the thermal stability of the compounds. In case of Zn-Cr LDH there is a non-mass loss transition around 420°C. Segregation of parent LDH structure to a bivalent oxide and a spinel takes place in both Zn-Cr and Zn-Al LDH only at temperatures above 550°C.Authors are grateful to Director R. R. L. Jorhat for his kind permission to publish the work, as well as acknowledgement is due to Prof. Herbert Poellmann of University of Halle, Germany for some powder XRD runs. Also, acknowledgement is due to Ministry of Environment and Forests, Govt. of India for some financial assistance.  相似文献   
79.
A. Saikia 《Pramana》1999,52(3):257-267
We present a brief analysis on the approximate methods for the determination of gluon distribution from the scaling violation of proton structureF 2 p in the low-x limit. In the leading order, a general low-x approximated relation is presented having more accuracy than the previous methods. Next-to-leading order correction is presented incorporating double-log-approximation. The proposed method is found to give good agreement with data. It may also be used to discriminate between the sets of gluon distributions in the low-x.  相似文献   
80.
The acid base equilibria of the sulfonephthalein dye bromophenol blue (BPB) in aqueous nonionic micellar solutions of Tween 20, Tween 40, Tween 60, and Tween 80 have been investigated spectroscopically using a partition equilibrium method. A visible red shift in the absorbance of the basic form of the dye with increase in surfactant concentration was observed at and above pH 6.98. This has been attributed to the stabilization of the acid form of the dye by the POE groups on the head of the surfactant monomers. Such stabilization effect was found to decreases with decrease in the number of carbon atom in the hydrophobic tail and with the increase in the hydrophile-lipophile balance (HLB) of the surfactant molecule. The equilibrium constant of the partition of the dyes between micellar and aqueous pseudophases (Kass) was found to increase with the surfactants in the order Tween 80 < Tween 60 < Tween 40 < Tween 20. The pKa2 of the dyes were predicted and found to be in good agreement with the experimental values.  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