全文获取类型
收费全文 | 361篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 214篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 42篇 |
物理学 | 100篇 |
出版年
2023年 | 2篇 |
2022年 | 10篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 6篇 |
2017年 | 13篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 26篇 |
2012年 | 16篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 14篇 |
2007年 | 13篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 15篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1962年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有371条查询结果,搜索用时 15 毫秒
11.
12.
13.
Jai Devi Suman Kumari R. Malhotra 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):587-597
Abstract The Schiff bases derived from the condensation of 2-aminobenzothiazole derivatives and 2-hydroxy-3-methoxybenzaldehyde and their silicon(IV) complexes with the general formula R2Si(L)Cl (R = Et, Bu, Ph, L = 2-(2-hydroxy-3-methoxy) benzylideneaminobenzo-thiazole) have been synthesized. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including IR and NMR (1H, 13C, and 29Si) spectroscopy. The analytical data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Staphylococcus aureus, Bacillus subtilis, and Escherichia coli) and fungi (Aspergillus niger and Candida albicans). The complexes were found to be more potent as compared to the ligands. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
14.
Reductive cleavage of acetals/ketals with zirconium tetrachloride-sodium borohydride leading to the formation of ether alcohols is described. 相似文献
15.
Organotin complexes of Schiff bases (derived from the condensation of hydrazides with salicylaldehyde derivatives) were prepared and their characterization was done using several spectroscopic techniques like FTIR, NMR (1H, 13C, and 119Sn) and mass spectrometry. The spectroscopic data of the ligands and their corresponding complexes revealed that the Schiff bases chelated to the tin metal in a tridentate manner through –ONO atoms (oxygen atom of the hydroxyl group of the salicylaldehydic derivatives, the nitrogen atom of azomethine group, and the oxygen atom of enolic group present in the carboxylic acid hydrazides). Around tin atom pentacoordinated geometry was exhibited. The synthesized ligands and their complexes have been assessed for their biological potency (antibacterial, antifungal and antioxidant using Ciprofloxacin, Fluconazole and Ascorbic acid as reference compounds) and few of the compounds showed optimistic activity. The ligands having electron withdrawing group attached showed greater antimicrobial activity as compared to the other ligands. The complexes showed the better activity than the ligands. The general trend followed by the complexes was diphenyl ?> ?dibutyl ?> ?dimethyl substituted complexes. Compound 11 was the most active against microbes. The antioxidant activity increased with electron donating group. The phenyl substituted complexes showed better activity as compared to the dibutyl and dimethyl substituted complexes. Compound 20 was the best antioxidant. 相似文献
16.
Lakshminarayanan Gowtham Das Ujjalkumar Laxmi Moksha Tapas Kumar Roy Nabanita Halder Thirumurthy Velpandian 《Journal of separation science》2022,45(6):1210-1221
4-Hydroxy isoleucine is one of the potent hypoglycemic active constituents of fenugreek seeds. A method capable of reducing biological interferences is required for bioavailability studies. An isocratic separation of 4-hydroxy isoleucine from endogenous interferences was achieved in ZIC-cHILIC column using 0.1% formic acid in water and acetonitrile (20:80, % v/v) pumped at 0.5 ml/min. Quantification was performed in multiple reaction monitoring mode using the transitions of m/z 148.1→102.1 and m/z 276.1→142.2 for 4-hydroxy isoleucine and homatropine (as internal standard), respectively. After full method validation, 4-hydroxy isoleucine levels in human plasma and commercial fenugreek formulations were determined. This method showed good linearity in the range of 50–2000 ng/mL. Intra- and interday accuracies were in the range of 90.64–109.0% and precision was <4.82% CV. The mean (SD) plasma concentration of 4-hydroxy isoleucine in healthy individuals at 2 h after oral administration of fenugreek tablet was found to be 1590 (260) ng/mL. Half of marketed formulations were found to contain <0.05% of 4-hydroxy isoleucine content. We developed a rapid hydrophilic interaction liquid chromatography–tandem mass spectrometry method for analysis of 4-hydroxy isoleucine in human plasma. This method can be applied directly to conduct the clinical pharmacokinetics studies of 4-hydroxy isoleucine in human population. 相似文献
17.
Michael Koch Karthikeyan Perumal Dr. Olivier Blacque Dr. Jai Anand Garg Dr. Ramanathan Saiganesh Dr. Senthamaraikannan Kabilan Prof. Dr. Kallupattu Kuppusamy Balasubramanian Dr. Koushik Venkatesan 《Angewandte Chemie (International ed. in English)》2014,53(25):6378-6382
Design of highly efficient phosphorescent emitters based on metal‐ and heavy atom‐free boron compounds has been demonstrated by taking advantage of the singlet fission process. The combination of a suitable molecular scaffold and appropriate electronic nature of the substituents has been utilized to tailor the phosphorescence emission properties in solution, neat solid, and in doped PMMA thin films. 相似文献
18.
Laxmi Banjare Sant Kumar Verma Akhlesh Kumar Jain Suresh Thareja 《Journal of heterocyclic chemistry》2020,57(9):3483-3492
Aromatase is a crucial enzyme for the catalysis of aromatization reaction at the last and rate-limiting step involved in the conversion of androgenic substrates to an estrogenic substrate. A hormone-dependent breast cancer in postmenopausal woman can be cured by inhibition of estrogen biosynthesis by the help of aromatase inhibitors (AIs). The mode of interactions of flavonones with the active site of aromatase has been studied in search of potent and selective AIs as a substitute of the natural steroidal ligand. Structure-based computational approach namely, molecular docking simulations were performed to investigate the structural features of the docked complex of aromatase and flavonoid ligands. A nonsteroidal flavonoid pharmacophore showing electrostatic and steric features for selective binding within the main pocket of the catalytic active site of aromatase has been identified as an outcome of the study. The binding affinity of quercetin and isoflavone were predicted within aromatase. Isoflavone was used as a negative control to compare its binding affinities with the selected dataset. The predicted binding affinity of negative control isoflavone was in accordance with its in vitro AI efficacy. Isoflavone showed poor binding affinity and ranked last in terms of MolDock score (−86.309 kcal/molÅ) compared to dataset molecules. The generated pharmacophoric information will be helpful for the synthetic chemist to design and synthesize selective AIs with comparable binding affinity to the natural steroidal ligand. 相似文献
19.
Tripathi Jai Prakash Jana Debaldev Vyshnavi Devi N. S. N. V. K. Tiwari Vandana Abbas Syed 《Nonlinear dynamics》2020,102(1):511-535
Nonlinear Dynamics - In this present study, we systematically explore the periodicity (almost periodic nature) of a dynamical system in time-varying environment, which portrays a special case of... 相似文献
20.
Jai Prakash Jaiswal 《Acta Mathematica Hungarica》2011,132(4):358-366
The object of the present work is to obtain a necessary condition for the existence of weakly symmetric and weakly Ricci-symmetric
Sasakian manifolds admitting a quarter-symmetric metric connection. 相似文献