全文获取类型
收费全文 | 910篇 |
免费 | 103篇 |
国内免费 | 183篇 |
专业分类
化学 | 596篇 |
晶体学 | 8篇 |
力学 | 73篇 |
综合类 | 23篇 |
数学 | 169篇 |
物理学 | 327篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 37篇 |
2021年 | 38篇 |
2020年 | 23篇 |
2019年 | 27篇 |
2018年 | 32篇 |
2017年 | 27篇 |
2016年 | 40篇 |
2015年 | 45篇 |
2014年 | 39篇 |
2013年 | 90篇 |
2012年 | 74篇 |
2011年 | 76篇 |
2010年 | 62篇 |
2009年 | 57篇 |
2008年 | 54篇 |
2007年 | 46篇 |
2006年 | 61篇 |
2005年 | 54篇 |
2004年 | 51篇 |
2003年 | 27篇 |
2002年 | 26篇 |
2001年 | 33篇 |
2000年 | 40篇 |
1999年 | 25篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1965年 | 2篇 |
排序方式: 共有1196条查询结果,搜索用时 92 毫秒
21.
M. Salman Y. Girault N Balbi L. Elegant 《Journal of Thermal Analysis and Calorimetry》1991,37(10):2389-2394
The attack by formic acid on the nitrogen electron pairs of N,N,N,N-tetramethylethylenediamine leads to the stoichiometric salt or to many other complexes with different molar fractions. Physical and thermodynamic parameters of two adducts, obtained by calorimetric study, are discussed in terms of their use as potential phase change materials in thermal energy storage because of their large heat of fusion between 288 and 333 K.
Zusammenfassung Bei der Einwirkung von Ameisensäure auf die Elektronenpaare von N,N,N,N-Tetramethylethylendiamin entsteht ein stöchiometrisches Salz oder mehrere andere Komplexe mit unterschiedlichem Molenbruch. Es werden physikalische und thermodynamische Parameter zweier bei der kalorimetrischen Untersuchung erhaltenen Addukte hinsichtlich ihrer Verwendung als potentielle Phasenwechselsubstanzen bei der thermischen Energiespeicherung diskutiert, da sie im Bereich 288–333 K eine große Schmelz-wärme besitzen.相似文献
22.
Salman R. Salman Gazi A. W. Derwish Sabri M. H. Al-Marsoumi 《Journal of inclusion phenomena and macrocyclic chemistry》1995,23(3):175-179
The intermolecular charge transfer complexes (CT) of two crown ethers (CE), viz, B15C5 and DB18C6 (as donors), and tetracyanoethylene (TCNE), as acceptor, were studied in the UV-visible region in dichloroethane (DCE), at 298.2 K. The sequence of addition of the cation was varied in the case of B15C5 such that in one system the sequence was (CE+Cation)+TCNE and in the other (CE+TCNE)+cation. These two systems were found to be non-interchangeable, even under reflux conditions, giving differentK
c
values which were explained as being due to the different geometries of the CE. For the first sequence, the values most affected depended on the fit of the metal cation with the ether cavity, thus in B15C5, Na+ showed the greatest effect, while for DB18C6 it was K+. 相似文献
23.
A new activation method has been developed for electroless copper plating on silicon wafer based on palladium chemisorption on SAMs of APTS without SnCl2 sensitization and roughening condition.A closely packed electroless copper film with strong adhesion is successfully formed by AFM observation.XPS study indicates that palladium chemisorption occurred via palladium chloride bonding to the pendant amino group of the SAMs. 相似文献
24.
25.
In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise. 相似文献
26.
Rosenani A. Haque Abbas Washeel Salman Srinivasa Budagumpi Amirul Al‐Ashraf Abdullah Zena A. Abdul Hameed Al‐Mudaris Amin M. S. Abdul Majid 《应用有机金属化学》2013,27(8):465-473
A series of Ag(I) complexes ( 6 , 7 , 8 , 9 ) derived from imidazol‐2‐ylidenes was synthesized by reacting Ag2O with an o‐, m‐, p‐xylyl or 1,3,5‐triazine‐linked imidazolium salts ( 1 , 2 , 3 , 4 ) and then characterizing these using various spectro‐analytical techniques. Additionally, triazine‐linked bis‐imidazolium salt 5 was characterized using the single‐crystal X‐ray diffraction method. Complexes 6–9 were formed from the N‐heterocyclic carbene ligand precursors 1–3 as PF6‐ salts in good yields. Conversely, salt 5 does not form Ag(I) complex even under various reaction conditions. Using ampicillin as a standard, complexes 6–9 were tested against bacteria strains Escherichia coli and Staphylococcus aureus as Gram‐negative and Gram‐positive bacteria, respectively, showing potent antimicrobial activities against the tested bacteria even at minimum inhibition concentration and bacterial concentration levels. Furthermore, the potential anticancer activities of the reported complexes were evaluated against the human colorectal cancer (HCT 116) cell lines, using 5‐fluorouracil as a standard drug. The highest anticancer activities were observed for complex 8 with an IC50 value of 3.4 μm , whereas the lowest was observed for complex 9 with an IC50 value of 18.1 μm . Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
27.
Infra-Red spectra of a series of substituted salicylaldehyde and 2-hydroxy-naphthaldehyde Schiff bases were used to investigate enol-keto tautomeric equilibrium. Two model compounds, namely, salicylidinaniline and naphthylidinequinolineamine Schiff bases were used to represent the enol and keto forms, respectively. From the IR spectra of the model compounds it was possible to assign the IR absorption for the C=O and the C=N groups in both the keto and the enol form. It was also possible to assign other absorptions which were either specific to the keto or the enol forms. Specific pattern were observed for all the studied compounds. 相似文献
28.
A series of alkyl triazole glycoside surfactants, ATGs, differing in the length of the alkyl linker between the sugar and the triazole, was synthesized and investigated on their surfactant properties and phase behavior in water. The results indicate no significant impact of the linker on surface and interphase properties, whereas the phase behavior is affected. Higher affinity for the bicontinuous cubic phase potentially favors methylene-linked ATGs over higher homologs for drug-delivery applications. A comparison of glucose and xylose reveals a tendency for high Krafft points for propargyl xyloside based ATGs. This disfavors these surfactants with respect to both glucose analogs and higher homologs. 相似文献
29.