全文获取类型
收费全文 | 172篇 |
免费 | 16篇 |
专业分类
化学 | 158篇 |
力学 | 2篇 |
数学 | 8篇 |
物理学 | 20篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2013年 | 1篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 1篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 4篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
1940年 | 2篇 |
1933年 | 1篇 |
排序方式: 共有188条查询结果,搜索用时 15 毫秒
1.
Kellie R. England Dr. Sang Ho Lim Lucy M. C. Luong Prof. Marilyn M. Olmstead Prof. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):874-878
The mono- and di-chloroform solvates of [Au2(μ-1,2-bis(diphenylarsino)ethane)2](AsF6)2 undergo single-crystal-to-single-crystal transformations that result in gain (over 12 hours) or slow loss (over five years) of only one chloroform molecule. The change in solvation results in changes in the structure and luminescence of the digold cation. The cation consists of a pair of slightly bent As-Au-As units that are connected through the two bridging dpae ligands and by aurophilic interactions with Au⋅⋅⋅Au contacts of 3.05152(15) Å in the disolvate or 2.9570(5) Å in the monosolvate. 相似文献
2.
Nabil N. AL‐Hashimi Rand O. Shahin Aqeel N. AL‐Hashimi Ajeal M. Al Ajeal Lubna H. Tahtamouni Chanbasha Basheer 《Biomedical chromatography : BMC》2019,33(2)
A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs. 相似文献
3.
Dr. Amineh Aghabali Sharon Jun Prof. Dr. Marilyn M. Olmstead Prof. Dr. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18908-18915
The photochemical reaction of piperazine with C70 produces a mono‐adduct (N(CH2CH2)2NC70) in high yield (67 %) along with three bis‐adducts. These piperazine adducts can combine with various Lewis acids to form crystalline supramolecular aggregates suitable for X‐ray diffraction. The structure of the mono‐adduct was determined from examination of the adduct I2N(CH2CH2)2NI2C70 that was formed by reaction of N(CH2CH2)2NC70 with I2. Crystals of polymeric {Rh2(O2CCF3)4N(CH2CH2)2NC70}n?nC6H6 that formed from reaction of the mono‐adduct with Rh2(O2CCF3)4 contain a sinusoidal strand of alternating molecules of N(CH2CH2)2NC70 and Rh2(O2CCF3)4 connected through Rh?N bonds. Silver nitrate reacts with N(CH2CH2)2NC70 to form black crystals of {(Ag(NO3))4(N(CH2CH2)2NC70)4}n?7nCH2Cl2 that contain parallel, nearly linear chains of alternating (N(CH2CH2)2NC70 molecules and silver ions. Four of these {Ag(NO3)N(CH2CH2)2NC70}n chains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non‐polar C70 cages encircling that core. Of the three bis‐adducts, one was definitively identified through crystallization in the presence of I2 as 12{N(CH2CH2)2N}2C70 with addends on opposite poles of the C70 cage and a structure with C2v symmetry. In 12{I2N(CH2CH2)2N}2C70, individual 12{I2N(CH2CH2)2N}2C70 units are further connected by secondary I2???N2 interactions to form chains that occur in layers within the crystal. Halogen bond formation between a Lewis base such as a tertiary amine and I2 is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize. 相似文献
4.
Inside Back Cover: Isolation of CeLu2N@Ih‐C80 through a Non‐Chromatographic,Two‐Step Chemical Process and Crystallographic Characterization of the Pyramidalized CeLu2N within the Icosahedral Cage (Chem. Eur. J. 29/2015) 下载免费PDF全文
5.
Ebraheem Abdu Musad Saleh Abdullah Mohammed AL Dawsari Kakul Husain Ismail Hassan Kutty K.M.Lokanatha Rai 《Molecules (Basel, Switzerland)》2021,26(2)
A novel synthesis of thiazolo[2,3-b]quinazolines 4(a–e), pyrido[2′,3′:4,5]thiazolo[2,3-b]quinazolines {5(a–e), 6(a–e), and 7(a–e)}, pyrano[2′,3′:4,5]thiazolo[2,3-b]quinazolines 8(a–e), and benzo[4,5]thiazolo[2,3-b]quinazoloine9(a–e) derivatives starting from 2-(Bis-methylsulfanyl-methylene)-5,5-dimethyl-cyclohexane-1,3-dione 2 as efficient α,α dioxoketen dithioacetal is reported and the synthetic approaches of these types of compounds will provide an innovative molecular framework to the designing of new active heterocyclic compounds. In our study, we also present optimization of the synthetic method along with a biological evaluation of these newly synthesized compounds as antioxidants and antibacterial agents against the bacterial strains, like S. aureus, E. coli, and P. aeruginosa. Among all the evaluated compounds, it was found that some showed significant antioxidant activity at 10 μg/mL while the others exhibited better antibacterial activity at 100 μg/mL. The results of this study showed that compound 6(c) possessed remarkable antibacterial activity, whereas compound 9(c) exhibited the highest efficacy as an antioxidant. The structures of the new synthetic compounds were elucidated by elemental analysis, IR, 1H-NMR, and 13C-NMR. 相似文献
6.
Prof. Dr. Steven Stevenson Amanda J. Rothgeb Katelyn R. Tepper Prof. Dr. James Duchamp Prof. Dr. Harry C. Dorn Xian B. Powers Mrittika Roy Prof. Dr. Marilyn M. Olmstead Prof. Dr. Alan L. Balch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(54):12545-12551
Purified samples of Ho3N@C2(22010)-C78 and Tb3N@C2(22010)-C78 have been isolated by two distinct processes from the rich array of fullerenes and endohedral fullerenes present in carbon soot from graphite rods doped with Ho2O3 or Tb4O7. Crystallographic analysis of the endohedral fullerenes as cocrystals with Ni(OEP) (in which OEP is the dianion of octaethylporphyrin) shows that both molecules contain the chiral C2(22010)-C78 cage. This cage does not obey the isolated pentagon rule (IPR) but has two sites where two pentagons share a common C−C bond. These pentalene units bind two of the metal ions, whereas the third metal resides near a hexagon of the cage. Inside the cages, the Ho3N or Tb3N unit is planar. Ho3N@C2(22010)-C78 and Tb3N@C2(22010)-C78 use the same cage previously found for Gd3N@C2(22010)-C78 rather than the IPR-obeying cage found in Sc3N@D3h-C78. 相似文献
7.
Inside Back Cover: Synthesis and Isolation of the Titanium–Scandium Endohedral Fullerenes—Sc2TiC@Ih‐C80, Sc2TiC@D5h‐C80 and Sc2TiC2@Ih‐C80: Metal Size Tuning of the TiIV/TiIII Redox Potentials (Chem. Eur. J. 37/2016) 下载免费PDF全文
8.
In this paper,we study the surface instability of a cylindrical pore in the absence of stress. This instability is called the Rayleigh-Plateau instabilty. We consider the model developed by Spencer et ... 相似文献
9.
Shabi Abbas Zaidi Seung Mi Lee Zeid A. AL Othman Abdullah M. AL Majid Won Jo Cheong 《Chromatographia》2011,73(5-6):517-525
Some acidic chiral templates were used to prepare open tubular (OT) molecule imprinted polymer (MIP) capillary columns to explore the effects of molecular structures of templates on chiral recognition capabilities and to verify the feasibility of the general MIP preparation protocol introduced in the previous study. The templates are phenyl carboxylic acids and their derivatives. Optimization was carried out for chiral separation of template enantiomers for each MIP column through varying pH and composition of eluent. It was found that the preparation protocol can be successfully applied for the appropriate templates with functional groups fulfilling the three-points interaction rule. The chiral separation performances were quite satisfactory for MIPs of such templates although they are yet inferior to the separation performances of the MIP columns fabricated with the templates of profen drugs (2-arylpropionic acids with a large substituent on the phenyl ring). Subtle variations of the template molecular structures have been found to be critical to enhance chiral recognition ability of the resultant MIP column. 相似文献
10.
SEC proton prediction model: verification and analysis. 总被引:4,自引:0,他引:4
C C Balch 《Radiation measurements》1999,30(3):231-250
This paper describes a model that has been used at the NOAA Space Environment Center since the early 1970s as a guide for the prediction of solar energetic particle events. The algorithms for proton event probability, peak flux, and rise time are described. The predictions are compared with observations. The current model shows some ability to distinguish between proton event associated flares and flares that are not associated with proton events. The comparisons of predicted and observed peak flux show considerable scatter, with an rms error of almost an order of magnitude. Rise time comparisons also show scatter, with an rms error of approximately 28 h. The model algorithms are analyzed using historical data and improvements are suggested. Implementation of the algorithm modifications reduces the rms error in the log10 of the flux prediction by 21%, and the rise time rms error by 31%. Improvements are also realized in the probability prediction by deriving the conditional climatology for proton event occurrence given flare characteristics. 相似文献