全文获取类型
收费全文 | 191篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 123篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 32篇 |
物理学 | 37篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 1篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 21篇 |
2012年 | 10篇 |
2011年 | 7篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 10篇 |
2006年 | 1篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
排序方式: 共有197条查询结果,搜索用时 760 毫秒
31.
Tadeusz Inglot Anna Gumieniczek Łukasz Komsta Agata Kasińska 《Chromatographia》2008,68(11-12):977-983
Seven sartans have been chromatographed with acetonitrile-buffer and methanol–buffer in different proportions as mobile phases. The retention values, log k or R M were extrapolated to zero organic modifier content to obtain the log k w or R MW values. Calibration equations were obtained for standards of known lipophilicity. A simple method employing a gradient procedure of 10–100% acetonitrile or methanol in 60 min and standards of the extreme lipophilicity was also elaborated. Chromatographic log P values were compared to those calculated by use of different software products. Finally, principal component analysis was performed to explore and visualize similarities and differences among the drugs and among the methods. 相似文献
32.
Zinc oxide nanoparticles were synthesized using chemical method in alcohol base. During synthesis three capping agents, i.e. triethanolamine (TEA), oleic acid and thioglycerol, were used and the effect of concentrations was analyzed for their effectiveness in limiting the particle growth. Thermal stability of ZnO nanoparticles prepared using TEA, oleic acid and thioglycerol capping agents, was studied using thermogravimetric analyzer (TGA). ZnO nanoparticles capped with TEA showed maximum weight loss. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for structural and morphological characterization of ZnO nanoparticles. Particle size was evaluated using effective mass approximation method from UV-vis spectroscopy and Scherrer's formula from XRD patterns. XRD analysis revealed single crystal ZnO nanoparticles of size 12-20 nm in case of TEA capping. TEA, oleic acid and thioglycerol capped synthesized ZnO nanoparticles were investigated at room temperature photoluminescence for three excitation wavelengths i.e. 304, 322 and 325 nm, showing strong peaks at about 471 nm when excited at 322 and 325 nm whereas strong peak was observed at 411 for 304 nm excitation. 相似文献
33.
We study Lusztig?s t-analog of weight multiplicities, or affine Kostka–Foulkes polynomials, associated to level one representations of twisted affine Kac–Moody algebras. We obtain an explicit closed form expression for the unique t-string function, using constant term identities of Macdonald and Cherednik. This extends previous work on t-string functions for the untwisted simply-laced affine Kac–Moody algebras. 相似文献
34.
An equation of state for a real fluid is presented and compared with the existing models such as the Carnathan-Starling equation of state. The proposed equation is used in computing enthalpies of vaporization of benzene from boiling point to a temperature of 0.95 TC. It has also been used to compute ΔHV for several hydrocarbons at 298.15K. The present model for calculating ΔHV has been compared with other models due to Yosim-Owens, Wilhelm-Battino, Reiss and co-workers, Carnahan-Starling, and Muller-Prausnitz. 相似文献
35.
Caterina Riccardi Shelby McCormick Rajeswari Kasi Challa Kumar 《Angewandte Chemie (International ed. in English)》2018,57(32):10158-10162
A potentially universal approach is presented for enzyme attachment to cellulose that significantly enhances enzyme stability while retaining high activity, and involves no chemical functionalization of cellulose. Bovine serum albumin (BSA) was interlocked in cellulose to form a protein‐friendly surface (named BSA‐Paper), while also providing COOH and NH2 groups for subsequent attachment of enzymes. The desired enzyme is then mixed with additional BSA and interlocked on BSA‐Paper. The second BSA layer dilutes and crosslinks the enzyme for improved stability. Laccase was tested as a model enzyme for interlocking on BSA‐Paper, and was found to retain over 100 % activity and was 240 times more stable at 25 °C (half life=180 d) than laccase. This new approach was also tested with a few other enzymes with encouraging results, thus providing a potentially universal method for stabilization of enzymes on cellulose with retention of high activities. 相似文献
36.
Antimony(V) in the range 24–240 μg can be determined very selectively in 8–10 M hydrochloric acid solutions by precipitation of its complex with ferroin; after dissolution in nitrobenzene, absorbances are measured at 510 nm. Antimony(III) and (V) can be determined successively in mixtures. 相似文献
37.
Leung MK Viswanath MB Chou PT Pu SC Lin HC Jin BY 《The Journal of organic chemistry》2005,70(9):3560-3568
[structure: see text] Anti-[2.2](1,4)biphenylenophane (4) was synthesized from de Meijere's tetrabromo[2.2]paracyclophane (5) through a four-step reaction sequence. Although an average separation of 3.09 A between the inner ring of the biphenylene units is normal for [2.2]paracyclophanes, a bond distance of 1.54 Afor the ethano C-C bridge at room temperature is shorter than usual. In addition, trimethylsilyl-substituted anti-[2.2](1,4)biphenylenophane 8 sublimes at 220 degrees C under a pressure lower than 1 x10(-5) Torr without decomposition or thermal isomerization. The high thermal stability of 8 suggested that the ethano bridges of the biphenylenophanes are less strained than those of [2.2]paracyclophane. Bathochromic shifts are observed in their UV-vis absorption spectra. The phane state interactions of 4 and 8 were evidenced by the weak structureless fluorescent emission maximized at 537 and 550 nm in CH(2)Cl(2) along with longer relaxation lifetimes of 229 and 292 ps, respectively. 相似文献
38.
Subramanian Annalakshmi Kasi Pitchumani 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):403-408
The effect of cyclodextrin inclusion complex formation on the intramolecular charge transfer (ICT) of the included 4-N,N-dimethylamino-2-strylquinoline (2-StQ-NMe2) has been studied in detail. 2-StQ-NMe2 in presence of α-, β-, γ- and HP-α- and Hp-β-CDs predominantly exhibits ICT fluorescence predominantly than the emission
from locally excited state, whereas in presence of HP-γ-CD the later is observed. In presence of α-CD, 2:1 complexation of
the 2-StQ-NMe2 is observed in addition to 1:1 complexation. The observed results are explained by the CD cavity size and an active role
for the secondary hydroxyl groups present in the wider rim of the CD cavity and also which finds support from absorption,
emission, lifetime and molecular modeling studies.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
39.
Maheswara M Koteswara Rao Y Siddaiah V Venkata Rao C Somayajulu KV Tyan Lin F 《Chemical & pharmaceutical bulletin》2004,52(8):974-975
Two new 5-deoxyflavonoids, 7,2',3',4'-tetramethoxyflavone (1) and 7,2',3',4'-tetramethoxyflavanone (2) together with a known flavone 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the whole plant of Calliandra inermis. The structures of these new compounds were elucidated by high resolution electron impact mass spectrometry (HR-EI-MS) and 1D and 2D-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY). 相似文献
40.
Chockalingam Venkatachalapathy Muniappan Thirumalaikumar Shanmugam Muthusubramanian Kasi Pitchumani Shunmugaperumal Sivasubramanian 《合成通讯》2013,43(23):4041-4047
Abstract: The first clean and the facile clay catalysed synthesis of á,N-diarylnitrones in good yield is reported. 相似文献