全文获取类型
收费全文 | 337篇 |
免费 | 14篇 |
专业分类
化学 | 210篇 |
晶体学 | 9篇 |
力学 | 26篇 |
数学 | 30篇 |
物理学 | 76篇 |
出版年
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 35篇 |
2012年 | 24篇 |
2011年 | 30篇 |
2010年 | 15篇 |
2009年 | 8篇 |
2008年 | 14篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1980年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有351条查询结果,搜索用时 31 毫秒
71.
Ghalib RM Hashim R Sulaiman O Mehdi SH Anis Z Rahman SZ Ahamed BM Abdul Majid AM 《Natural product research》2012,26(22):2155-2158
The leaves of Cinnamomum iners (Reinw. ex Blume-Lauraceae) have been refluxed successively with chloroform and alcohol to get chloroform extract and alcoholic extract. Both the extracts have been assayed for cytotoxicity against human colorectal tumour cells. The chloroform extract exhibited significant cytotoxicity with IC(50) 31?μg mL(-1) (p?0.01). However, ethanol extract was found to be much less cytotoxic with IC(50)?>?200?μg mL(-1). The chloroform extract has been further proceeded for chemical analysis by GC-TOFMS and 178 components were identified including acids, amines, amides, aldehydes, alcohols, esters, benzene derivatives, bicyclic compounds, terpenes, hydrocarbons, naphthalene derivatives, furan derivatives, azulenes, etc. Nine components representing 51.73% of the total chloroform extract were detected as major components. Caryophyllene (14.41%) and Eicosanoic acid ethyl ester (12.17%) are the most prominent components of the chloroform extract. β-Caryophyllene (14.41%) as most abundant compound supports potent cytotoxicity as shown by chloroform extract. 相似文献
72.
Muhammad Bisyrul Hafi Othman Rafiza Ramli Zulkifli Mohamad Ariff Hazizan Md Akil Zulkifli Ahmad 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1515-1523
The influence of the structure properties relationships of silicone incorporated polyimide (PI) on thermal stability was investigated by using single scan thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) in nitrogen. Four systems have been synthesized based on monomer 4-(4-(1-(4-(4-aminophenoxy) phenyl)-1-methylethyl) phenoxy) aniline (BAPP)/3,3??,4,4??-Biphenyltetracarboxylic dianhydride including parent PI (S-1), PI siloxane copolymer (S-2 and S-3), and PI siloxane hybrid (S-4). The derivative thermogravimetric analysis (DTG) and DSC curves indicate a double and single stage decomposition process and glass transition temperature (T g), respectively. While the PI, PIS, and PSH showed distinctive features towards thermal analysis, it was found that the rate of degradation (???/??t) was influenced by the flexibility of Si?CO?CSi in the backbone and in Si?CO?CSi itself. These results revealed that the presence of Si?CO?CSi in either the backbone or matrix indicates its stability with regard to high thermal service applications. 相似文献
73.
Bhawani Showkat A. Hena Sufia Ibrahim Mohamad N. Mohamad Sulaiman Othman Hashim Rokiah San Kok L. 《平面色谱法杂志一现代薄层色谱法》2012,25(4):355-357
JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic separation of three metal cations was performed on high-performance thin-layer plates (silica gel 60F254) with... 相似文献
74.
The aim of this brief report is to study the behaviour of sheath structure in a multi-component plasma with dust-neutral collisions.
The plasma consists of electrons, ions, micron size negatively charged dust particles and neutrals. The sheath-edge potential
and sheath width are calculated for collisionally dominated sheath. Comparison of collisionless and collisionally dominated
sheath are made. 相似文献
75.
Abdul Hamid Othman Yang‐Yi Yang Xiao‐Ming Chen Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):e318-e319
The three‐coordinate Ag atom in the title compound, [Ag(C7H3N2O6)(C18H15P)2], shows trigonal–planar coordination [P—Ag—P = 147.1 (1)° and ΣAg = 359.0 (3)°]. Adjacent molecules are linked through the O atoms of adjacent nitro groups [Ag?O = 3.205 (3) and 3.302 (4) Å] into a zigzag chain running parallel to the c axis. 相似文献
76.
Hawsar Othman Mohammed Attila Almsi Szilrd Molnr Pl Perjsi 《Molecules (Basel, Switzerland)》2022,27(13)
Hyperglycemia is reported to be associated with oxidative stress. It can result in changes in the activities of drug-metabolizing enzymes and membrane-integrated transporters, which can modify the fate of drugs and other xenobiotics; furthermore, it can result in the formation of non-enzyme catalyzed oxidative metabolites. The present work aimed to investigate how experimental hyperglycemia affects the intestinal and biliary appearance of the oxidative and Phase II metabolites of ibuprofen in rats. In vivo studies were performed by luminal perfusion of 250 μM racemic ibuprofen solution in control and streptozotocin-treated (hyperglycemic) rats. Analysis of the collected intestinal perfusate and bile samples was performed by HPLC-UV and HPLC-MS. No oxidative metabolites could be detected in the perfusate samples. The biliary appearance of ibuprofen, 2-hydroxyibuprofen, ibuprofen glucuronide, hydroxylated ibuprofen glucuronide, and ibuprofen taurate was depressed in the hyperglycemic animals. However, no specific non-enzymatic (hydroxyl radical initiated) hydroxylation product could be detected. Instead, the depression of biliary excretion of ibuprofen and ibuprofen metabolites turned out to be the indicative marker of hyperglycemia. The observed changes impact the pharmacokinetics of drugs administered in hyperglycemic individuals. 相似文献
77.
We have investigated the viscoelastic behaviour exhibited by chiral smectic C* phases in homeotropic orientation. For an appropriate scattering geometry and using the light scattering technique, the orientational diffusivities associated with the Goldsone mode in ferro- and antiferroelectric phases of C11thiobenzoate and C8tolane compounds have been measured. (SmCA*) is about 100 times weaker than (SmC*). This divergence may be largely attributed to the mode of the molecular arrangement in ferro- and antiferroelectric phases, in spite of the same helical structure observed in the two phases. 相似文献
78.
79.
The retention profile of uranyl ions from aqueous thiocyanate media by polyether-type based polyurethane foams (PUFs) has been studied to gain more information regarding the mechanism of extraction. The effect of pH, shaking time, surfactant type, extraction media, temperature and analyte concentration on the retention of uranyl ions onto PUFs has been studied. It has been found that, the sorption of uranyl ions involved in the formation of a ternary complex ion associate of uranyl ion, thiocyanate and PUFs is highly dependent on these parameters. The kinetics and thermodynamics of the uranyl ions sorption have been studied in more detail. The dependency of the extraction on the parameters can be explained via a “solvent extraction,” mechanism. However, owing to the complex nature of the PUFs a dual-mode sorption mechanism involving both absorptions related to “solvent extraction” and an added component for “surface adsorption” may be operated simultaneously. Attempts for quantitative retention and recovery of the uranyl ions in tap and industrial waste water samples by the proposed PUFs columns has been carried out and satisfactory results have been obtained. The cellular structure of the PUF sorbent offer unique advantages over a conventional bulk type sorbents in rapid, versatile effective separation and/or preconcentration of uranyl ions. 相似文献
80.
l-Arabinose was reduced to l-arabinitol and condensed with formaldehyde to give two bis(di-0-methylene-l-arabityloxymethane and two di-O-methylene-l-arabinitol derivatives. Cis-fused 1,3:2,4-Di-O-methylene-l-arabinitol and trans-fused 2,4:3,5-Di-O-methylene-l-arabinitol were also isolated; only the former was affected by the oxidation to give the corresponding aldehyde, which was converted successively to the hydroxy amide, the ethyl hydroxy ester, the corresponding keto ester and vitamin C. 相似文献