全文获取类型
收费全文 | 1219篇 |
免费 | 42篇 |
国内免费 | 4篇 |
专业分类
化学 | 924篇 |
晶体学 | 10篇 |
力学 | 39篇 |
数学 | 51篇 |
物理学 | 241篇 |
出版年
2023年 | 10篇 |
2022年 | 38篇 |
2021年 | 27篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 43篇 |
2017年 | 58篇 |
2016年 | 46篇 |
2015年 | 42篇 |
2014年 | 42篇 |
2013年 | 112篇 |
2012年 | 86篇 |
2011年 | 101篇 |
2010年 | 43篇 |
2009年 | 42篇 |
2008年 | 40篇 |
2007年 | 53篇 |
2006年 | 44篇 |
2005年 | 33篇 |
2004年 | 30篇 |
2003年 | 15篇 |
2002年 | 21篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有1265条查询结果,搜索用时 9 毫秒
41.
Amit M. Jabgunde Rahul S. Patil Swarup De Eveline Lescrinier Steven De Jonghe Leonid Beigelman Piet Herdewijn 《Tetrahedron》2019,75(8):1107-1114
The synthesis of 3′-fluoro-4′-amino-hexitol nucleosides with a uracil and cytosine nucleobase was performed. The synthesis started from 1,5:2,3-dianhydro-4,6-benzylidene-allitol and afforded the target compounds in 15 steps. These protected hexitol nucleosides are valuable building blocks for the preparation of a new class of oligonucleotides. 相似文献
42.
P. H. Salunkhe Y. S. Patil V. N. Kadam J. N. Mahindrakar V. P. Ubale 《高分子科学杂志,A辑:纯化学与应用化学》2019,56(4):299-305
Here we report a new five polyamides prepared via solution-phase polycondensation under Yamazaki-Higashi conditions to prove the suitability of this method. The synthesized polyamides were characterized by FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, inherent viscosity, solubility and wettability tests. These polyamides were amorphous in nature and they are completely soluble in many organic solvents and they could easily be solution-cast into transparent, flexible films. The as-prepaired polymers showed excellent thermal properties. The glass transition temperatures of these polymers are in the range of 251–274?°C under nitrogen atmosphere. The decomposition temperature in nitrogen for a 10% weight-loss temperature is more than 744?°C, and char yield at 900?°C ranged from 43 to 56% in nitrogen. Water contact angles were also tested to know the hydrophilicity of the polyamide films. As-synthesized polyamides showed smallest quantact angles indicating hydrophilic surface. 相似文献
43.
44.
P. V. Badadhe L. R. Patil S. S. Bhagat A. V. Chate D. W. Shinde M. D. Nikam C. H. Gill 《Journal of heterocyclic chemistry》2013,50(5):999-1004
The title compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h and 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h have been synthesized from β‐diketones and chromones, respectively, having 5‐methyl‐3‐phenylisoxazole moiety. Substituted 2‐acetylphenyl 5‐methyl‐3‐phenylisoxazole‐4‐carboxylate 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h were converted into 1‐(2‐hydroxyphenyl)‐3‐(5‐methyl‐3‐phenylisoxazole‐4‐yl)propane‐1,3‐dione 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h by Baker–Venketaraman transformation. Further, the cyclodehydration of diketone 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h with glacial acetic acid in conc. HCl at reflux gave corresponding substituted 2‐(5‐methyl‐3‐phenylisoxazole‐4‐yl)‐4H‐chromen‐4‐one 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h . The corresponding 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h react with hydrazine hydrate in presence of glacial acetic acid in ethanol at reflux to furnish 2‐(5‐5(5‐methyl‐3‐phenylisoxazole‐4‐yl)‐1H‐pyrazole‐3‐yl)phenol 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h . The structures of all newly synthesized compounds have been confirmed by IR, 1H NMR, mass spectral data, as well as elemental analysis. The synthesized compounds have been screened for their antimicrobial activity. Some of the compounds show better antimicrobial activity as compared with the reference drugs Streptomycin, Ampicillin, Gentamycin, Cefixime, and Ketoconazole. 相似文献
45.
A mild and efficient method has been developed for the chemoselective preparation of 1,1-diacetates (acylals) from aldehydes catalyzed in the presence of a catalytic amount (0.1 mmol) of anhydrous cobalt(II) bromide under solvent-free conditions. The remarkable selectivity under mild and neutral conditions, excellent yields, short reaction time, and easily available and inexpensive catalyst are important features of this method. 相似文献
46.
An efficient and convenient procedure has been developed for the oxidation of methylarenes to the corresponding benzoic acids using a bromide/bromate-based reagent system in water. Regeneration and reusability of the bromide/bromate reagent is demonstrated. 相似文献
47.
48.
Patil ST Bhoir IC Bhagwat AM Sundaresan M 《Fresenius' Journal of Analytical Chemistry》2000,367(1):91-93
Tolnaftate, an antifungal drug (TF) and related impurities arising from synthesis, viz., N-methyl-m-toluidine (NMmT) and beta-naphthol-1-chlorothio carbamate (beta-NCTC) can be determined by supercritical fluid chromatography. Even though it was possible to elute TF completely with neat SCF CO2, the peaks of the impurities were found to merge. The chromatographic figures of merit of the three analytes such as retention time (tR), capacity factor (k), selectivity factor (alpha), no. of theoretical plates (N), were optimized. The three compounds can be resolved in 5 min on a Hypersil (250 x 4.0 mm) 5 mu, C18 column with supercritical carbon dioxide, modified with 1.96% methanol as the mobile phase at 9.81 MPa and at 40 degrees C. Detection was carried out at 220 nm. The data as evaluated by the linear regression least squares fit method gave linearity ranges from 0.2 to 10.0 microg/mL for TF and NMmT and 0.3 to 10.0 microg/mL for beta-NCTC with correlation coefficients > 0.99. The method was successfully employed to estimate levels of 0.01% for NMmT and 0.02% for beta-NCTC with respect to TF. 相似文献
49.
Vivek W. Bhoyare Akash G. Tathe Prof. Vincent Gandon Dr. Nitin T. Patil 《Angewandte Chemie (International ed. in English)》2023,62(46):e202312786
The successful realization of gold-catalyzed chain-walking reactions, facilitated by ligand-enabled Au(I)/Au(III) redox catalysis, has been reported for the first time. This breakthrough has led to the development of gold-catalyzed annulation reaction of alkenes with iodoarenes by leveraging the interplay of chain-walking and π-activation reactivity mode. The reaction mechanism has been elucidated through comprehensive experimental and computational studies. 相似文献
50.
Rahul A. Patil Mohsen Talebi Leonard M. Sidisky Daniel W. Armstrong 《Chromatographia》2017,80(10):1563-1574
Dicationic ionic liquids (ILs) are widely used as gas chromatography (GC) stationary phases as they show higher thermal stabilities, variety of polarities, and unique selectivities towards certain compounds. An important aspect contributing to them is that they show multiple solvation interactions compared to the traditional GC stationary phases. Dicationic ILs are considered as combination of three structural moieties: (1) cationic head groups; (2) a linkage chain; and (3) the counter anions. Modifications in these structural moieties can alter the chromatographic properties of IL stationary phases. In this study, a series of nine thermally stable IL stationary phases were synthesized by the combination of five different cations, two different linkage chains, and two different anions. Different test mixtures composed of a variety of compounds having different functional groups and polarities were analyzed on these columns. A comparison of the separation patterns of these different compounds on nine different IL columns provided some insights about the effects of structural modifications on the selectivities and polarities of dicationic ILs. 相似文献