全文获取类型
收费全文 | 622篇 |
免费 | 15篇 |
国内免费 | 6篇 |
专业分类
化学 | 387篇 |
晶体学 | 17篇 |
力学 | 7篇 |
数学 | 31篇 |
物理学 | 201篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 26篇 |
2021年 | 23篇 |
2020年 | 20篇 |
2019年 | 24篇 |
2018年 | 24篇 |
2017年 | 18篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 32篇 |
2013年 | 54篇 |
2012年 | 44篇 |
2011年 | 54篇 |
2010年 | 33篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 15篇 |
2004年 | 13篇 |
2003年 | 4篇 |
2002年 | 12篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1944年 | 1篇 |
排序方式: 共有643条查询结果,搜索用时 15 毫秒
631.
Nagaraju M. Patro Azmi Sultana Keiji Terao Daisuke Nakata Ayako Jo Akihito Urano Yoshiyuki Ishida Raghu N. Gorantla Vinay Pandit Kshama Devi Shishir Rohit Baljinder K. Grewal Elizabeth M. Sophia Anand Suresh Vineeth K. Ekbote Sarasija Suresh 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):471-483
In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection. 相似文献
632.
An efficient synthesis of 4-benzyl cinnolines from aryl phenylallylidene hydrazone is described. In this report aluminium chloride as a Lewis acid catalyst and toluene as a solvent are used for the synthesis. This method is expected to more advantageous than the other reported methods of synthesis of the cinnoline rings because of its low cost, better yield, and benign reaction conditions.
[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] 相似文献
633.
The four-component domino reactions of (E)-3-(dimethylamino)-1-arylprop-2-en-1-ones with anilines, aromatic aldehydes, and 1,3-cyclohexanediones in an equimolar ratio in acetic acid afforded functionalized tetrahydroquinolones in good yields. This one-pot transformation involves the formation of two C–C and two C–N bonds in a single synthetic operation. 相似文献
634.
S. Banerjee A. Kumar P. Sujatha Devi 《Journal of Thermal Analysis and Calorimetry》2011,104(3):859-867
This paper reports preparation of nanoparticles of oxides by the citrate–nitrate process and the effect of metal ions on the
thermal decomposition characteristics of the corresponding citrate–nitrate gel precursors. In order to understand the effect
of metal ions on the thermal decomposition characteristics of the precursors, we have prepared a series of single component
oxides such as MO, where M = Zn, MO2, where M = Sn, Ce, Zr, and M2O3 where M = Al, Fe, Bi. In all the cases the citrate to nitrate ratio was fixed at 0.3. In order to ascertain the decomposition
characteristics of the gel samples, TG/DTA studies were performed on the dried gel samples. After complete physico-chemical
characterization of the precursors and the calcined products, it could be concluded that the nature of decomposition of the
precursors depends largely on the nature of the metal ions. Finally, the advantages of the citrate–nitrate process such as
its high degree of reproducibility, its potential for large-scale production of nano-crystalline ceramic oxide powders and
its lower cost could be established based on a series of experiments and examples. 相似文献
635.
Research on Chemical Intermediates - N-(3-oxo-3-morpholino-1-phenyl-propyl) benzo sulfonamide (BMS) (C19H22N2O4S) has been synthesized and characterized by FT-IR, 1H and 13C NMR, and ESI-mass... 相似文献
636.
KHSO4-assisted Michael addition–elimination reactions of 2-methylindoles and 1,2-dimethylindoles with 3-dimethylamino-1-phenylprop-2-en-1-ones (2) in water, leading to the formation of 3-(2-methyl-1H-indol-3-yl)-1-arylpropenones (3a–e) and 3-(1,2-dimethy-1H-lindol-3-yl)-1-arylpropenones (3f–j) respectively in good to excellent yields have been reported. However, cyclodehydration of adducts 3a–f to give carbazoles 4 failed to take place under the reaction conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
637.
Rajasekaran Sruthi Reghunath B. Shalini K. R. Sunaja Devi Saravanakumar B. Johnson William J. Pinheiro Dephan Arumugam Madan Kumar 《Journal of Solid State Electrochemistry》2023,27(4):911-925
Journal of Solid State Electrochemistry - In the recent years, the whole world is looking for better energy storage devices. Supercapacitors are among the most promising high-capacity... 相似文献
638.
The incorporation of difluoromethylated (CF2) moiety into potentially useful parent molecules lead to significant changes in metabolic stability, lipophilicity, and solubility of the molecules. Over the past several years, with the advent of new difluoromethylating reagents, great progress has been made in the development of a protocol for the direct incorporation of the CF2H group into organic molecules. Among them, difluroalkylation induced by visible light has emerged as an efficient strategy over the past few years. In particular, this protocol provides a more sustainable alternative to other traditional radical‐triggered reactions in terms of environment, energy, step‐economy, health, and safety. The present review mainly focuses on the development of the photocatalytic difluoroalkylation to olefinic moiety using transition‐metal complexes, organic dyes as the photocatalyst; and some organic compounds as a medium of photocatalysis. 相似文献
639.
Koji Ishizu Usha Devi G. Prabhu Dan Draney Byung H. Lee C. S. Marvel 《Journal of polymer science. Part A, Polymer chemistry》1982,20(10):2851-2862
A series of acetylene-terminated quinoxaline oligomers was synthesized for testing as possible adhesives for airplane manufacturing. 相似文献
640.
The technique of generalised quasilinearization is developed, using the method of lower and upper solutions and the monotone iterative technique (MIT), to prove the existence of unique solutions for functional differential equations (FDE) with retardation and anticipation. 相似文献