全文获取类型
收费全文 | 389篇 |
免费 | 27篇 |
专业分类
化学 | 215篇 |
晶体学 | 8篇 |
力学 | 9篇 |
数学 | 13篇 |
物理学 | 117篇 |
无线电 | 54篇 |
出版年
2024年 | 3篇 |
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 25篇 |
2015年 | 13篇 |
2014年 | 27篇 |
2013年 | 32篇 |
2012年 | 30篇 |
2011年 | 33篇 |
2010年 | 27篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 19篇 |
2006年 | 13篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有416条查询结果,搜索用时 0 毫秒
1.
The halohydrin reaction of chiral N-enoyl-2-oxazolidinones 1 by halogen (Br2/I2) and water were efficiently carried out in aqueous organic solvent promoted by silver(I) with high anti- and regioselectivity and moderate to good diastereoselectivities. The alkenoyl, cinnamoyl and electron-deficient cinnamoyl substrates smoothly underwent bromohydrin reaction in aqueous acetone but no iodohydrin reaction, where as electron-rich cinnamoyl substrates preferred to undergo iodohydrin reaction in aqueous acetone with moderate diastereoselectivity and enhanced diastereoselectivity was observed in aqueous THF. 相似文献
2.
3.
Chloramphenicol and thiamphenicol have been enantioselectively synthesized using an asymmetric halohydrin reaction as a key step. In particular, halomethoxylation reaction was used, where O-methyl functions as a hydroxyl protecting group and eliminates an additional protection step. 相似文献
4.
Conductive films of gold were assembled on flexible polymer substrates such as Kapton and polyethylene using a solution-based process. The polymer substrates were modified by using argon plasma and subsequent coupling of silanes with amino- or mercapto- terminal groups. These modified surfaces were examined by X-ray photoelectron spectroscopy and contact angle measurements. Colloidal gold was assembled onto the silane-modified surface from solution. The gold particles are attached to the surface by covalent interactions with the thiol or amine group. Formation of a conductive film is achieved by increasing the coverage of gold by using a "seeding" method to increase the size of the attached gold particles. Field emission scanning electron microscopy was used to follow the growth of the film. The surface resistance of the films, measured using a four-point probe, was about 1 Omega/sq. 相似文献
5.
Vigneshwaran N Bijukumar G Karmakar N Anand S Misra A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):163-170
This article describes the analysis of autofluorescence of advanced glycation end products of hemoglobin (Hb-AGE). Formed as a result of slow, spontaneous and non-enzymatic glycation reactions, Hb-AGE possesses a characteristic autofluorescence at 308/345 nm (lambda(ex)/lambda(em)). Even in the presence of heme as a quenching molecule, the surface presence of the glycated adduct gave rise to autofluorescence with the quantum yield of 0.19. The specificity of monoclonal antibody developed against common AGE structure with Hb-AGE was demonstrated using reduction in fluorescence polarization value due to increased molecular volume while binding. The formation of fluorescent adduct in hemoglobin in the advanced stage of glycation and the non-fluorescent HbA(1c) will be of major use in distinguishing and to know the past status of diabetes mellitus. While autofluorescence correlated highly with HbA(1c) value under in vivo condition (r = 0.85), it was moderate in the clinical samples (r = 0.55). The results suggest a non-linear relation between glycemia and glycation, indicating the application of Hb-AGE as a measure of susceptibility to glycation rather than glycation itself. 相似文献
6.
3,4-Diaroylfuroxans 1 react with various dipolarophiles 3 under microwave activation to afford the cycloadduct 4 instead of the expected isoxazole 5 in good yields in the absence of solvent. 相似文献
7.
Stacey M. Frumm Zi Peng Fan Kenneth N. Ross Jeremy R. Duvall Supriya Gupta Lynn VerPlank Byung-Chul Suh Edward Holson Florence F. Wagner William B. Smith Ronald M. Paranal Christopher F. Bassil Jun Qi Giovanni Roti Andrew L. Kung James E. Bradner Nicola Tolliday Kimberly Stegmaier 《Chemistry & biology》2013,20(5):713-725
8.
9.
This paper focuses on developing an area efficient hyperbolic Coordinate Rotation Digital Computer (CORDIC) algorithm with performance improvement. The algorithm eliminates the need of scale factor calculation in the Range of Convergence (ROC). At the same time the range of convergence offered is higher than the conventional CORDIC ROC in the hyperbolic rotation mode. Being the only kind of algorithm in hyperbolic rotation with sign sequence μ?=?1 always, one complete operation requires just 5 iterations. Thus the pipelined implementation has 5 stages which provides a 50% increase in throughput in comparison to conventional CORDIC. As far as the area improvement is considered, 16-bit processor can be realized using 56% less number of full adders required by Flat-CORDIC. The x and y datapath are based on series expansion of hyperbolic functions. The complete algorithm design along with pipelined architecture implementation is detailed. 相似文献
10.
Fabrication and Circuit Modeling of NMOS Inverter Based
on Quantum Dot Gate Field-Effect Transistors
Supriya Karmakar John A. Chandy Mukesh Gogna Faquir C. Jain 《Journal of Electronic Materials》2012,41(8):2184-2192
This paper presents the fabrication of a negative-channel metal–oxide–semiconductor (NMOS) inverter based on quantum dot gate field-effect transistors (QDG-FETs). A QDG-FET produces one intermediate state in its transfer characteristic. NMOS inverters based on a QDG-FET produce three states in their transfer characteristic. The generation of the third state in the inverter characteristic makes this a promising circuit element for multivalued logic implementation. A circuit simulation result based on the Berkley simulation (BSIM) circuit model of the QDG-FET is also presented in this paper, predicting the fabricated device characteristic. 相似文献