全文获取类型
收费全文 | 1432篇 |
免费 | 49篇 |
国内免费 | 3篇 |
专业分类
化学 | 918篇 |
晶体学 | 14篇 |
力学 | 65篇 |
数学 | 126篇 |
物理学 | 361篇 |
出版年
2024年 | 11篇 |
2023年 | 13篇 |
2022年 | 33篇 |
2021年 | 25篇 |
2020年 | 47篇 |
2019年 | 44篇 |
2018年 | 46篇 |
2017年 | 37篇 |
2016年 | 63篇 |
2015年 | 31篇 |
2014年 | 53篇 |
2013年 | 117篇 |
2012年 | 124篇 |
2011年 | 152篇 |
2010年 | 71篇 |
2009年 | 60篇 |
2008年 | 83篇 |
2007年 | 69篇 |
2006年 | 68篇 |
2005年 | 58篇 |
2004年 | 44篇 |
2003年 | 26篇 |
2002年 | 39篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1989年 | 6篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1968年 | 3篇 |
1959年 | 2篇 |
1934年 | 3篇 |
排序方式: 共有1484条查询结果,搜索用时 15 毫秒
961.
Paul A Hull JF Norris MR Chen Z Ess DH Concepcion JJ Meyer TJ 《Inorganic chemistry》2011,50(4):1167-1169
Significant rate enhancements are found for benzyl alcohol oxidation by the Ru(V)═O(3+) form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH(2))](2+) [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to Ru(IV)═O(2+) and for the Ru(IV)═O(2+) form with added bases due to a new pathway, concerted hydride proton transfer (HPT). 相似文献
962.
Richard H. Holm Edward I. Solomon Amit Majumdar Adam Tenderholt 《Coordination chemistry reviews》2011,255(9-10):993-1015
The similarities and differences in the fundamental coordination chemistry of molybdenum and tungsten mainly in physiological oxidation states MIV–VI are examined in relation to the properties of enzyme sites that catalyze oxygen atom transfer reactions. The comparative aspects of dithiolene complexes, which as synthetic analogues simulate structural and electronic features of these sites, are emphasized. Analogue reaction systems of enzymes are summarized. The mechanism of reduction of the biological substrate Me2SO in one such system as elucidated with density functional calculations is presented as a case study. 相似文献
963.
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na(3) cluster and present the adiabatic PESs for the electronic states 2(2)E' and 1(2)A(1)', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for the states 2(2)E' and 1(2)A(1)' demonstrate the numerical validity of so called "Curl Condition," such states closely form a sub-Hilbert space. For this subspace, we employ the NAC terms to solve the "adiabatic-diabatic transformation (ADT)" equations to obtain the functional form of the transformation angles and pave the way to construct the continuous and single valued diabatic potential energy surface matrix by exploiting the existing first principle based theoretical means on beyond Born-Oppenheimer treatment. Nuclear dynamics has been carried out on those diabatic surfaces to reproduce the experimental spectrum for system B of Na(3) cluster and thereby, to explore the numerical validity of the theoretical development on beyond Born-Oppenheimer approach for adiabatic to diabatic transformation. 相似文献
964.
Amit K. Chakraborty Tiia Plyhm Michel Barbezat Adly Necola Giovanni P. Terrasi 《Journal of nanoparticle research》2011,13(12):6493-6506
A systematic investigation of the dispersion of carbon nanotubes (CNTs), 1–6 nm in diameter and a few microns in length, in
a bisphenol F-based epoxy resin has been presented. Several dispersing techniques including high-speed dissolver, ultrasonic
bath/horn, 3-roll mill, etc. have been employed. Optical microscopy has been extensively used to systematically characterise
the state of CNT dispersion in the epoxy resin during the entire processing cycle from mixing CNT with resin to adding and
curing with hardener. Complimentary viscosity measurements were also performed at various stages of nanocomposite processing.
A method to produce a good CNT dispersion in resin was established, but the state of CNT dispersion was found to be extremely
sensitive to its physical and chemical environments. The cured nanocomposites were further tested for their thermo-mechanical
properties by dynamic mechanical thermal analysis (DMTA), and for flexural and compressive mechanical properties. The measured
properties of various nanocomposite plates were then discussed in view of the corresponding CNT dispersion. 相似文献
965.
Sharma N Sharma A Shard A Kumar R Saima Sinha AK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10350-10356
Tandem reactions that involve chemoselective Knoevenagel/Perkin condensation-decarboxylation-Heck/Suzuki coupling or Heck-aldol sequences have been achieved. This enabled the first concise and efficient synthesis of several important hydroxy-functionalized compound classes, such as stilbene-cinnamoyl hybrids (potent protein tyrosine phosphatase1B inhibitors), cinnamoyl-cinnamic acid hybrids, asymmetric distyrylbenzenes, and biarylstyrenes. Previously reported synthesis require multiple steps and protection/deprotection manipulations. 相似文献
966.
Different Heterocycles Functionalized s‐Triazine Analogues: Design,Synthesis and In Vitro Antimicrobial,Antituberculosis, and Anti‐HIV Assessment
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Paresh K. Patel Rahul V. Patel Dharmesh H. Mahajan Parimal A. Parikh Girish N. Mehta Christophe Pannecouque Erik De Clercq Kishor H. Chikhalia 《Journal of heterocyclic chemistry》2014,51(6):1641-1658
Some new quinolone condensed s‐triazine derivatives endowed with different heterocycles and 4‐aminobenzonitrile moiety has been synthesized and examined for their bioactivities against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, and Shigella flexneri), two fungi (Aspergillus niger, Candida albicans) by using agar streak dilution method, and Mycobacterium tuberculosis H37Rv by using Lowenstein and Jensen MIC method. Upon preliminary biological screening, it was observed that the majority of the compounds were found to possess a significant broad spectrum antimicrobial (MICs: 6.25–25 µg/mL) and antitubercular (MIC: 12.5 µg/mL) potential. Hence, anti‐HIV activity against two types of HIV viral strains [HIV‐1 (IIIB) and HIV‐2 (ROD)] has been carried out using the MTT assay. From this bioassay, we have identified some potent inhibitors acting as anti‐HIV‐1 agents (IC50: 4.45 µg/mL) with promising therapeutic index of 16 for analogue 7 h. The structural assignments of the new products were carried out on the basis of IR, 1H NMR, 13C NMR spectroscopy, and elemental analysis. 相似文献
967.
A flexible protocol for the synthesis of three lipophilic α-amino acid components of some novel cyclic peptides having important histone deacetylase inhibiting properties has been developed from a common source, which featured a cross-metathesis reaction between two unhindered terminal olefins as the key step. 相似文献
968.
The reaction of 2,5-bis-(α-arylhydroxymethyl)thiophenes with 5-aryldipyrromethanes in the presence of acidic ionic liquid gives 21-thia-5,10,15,20-tetraarylporphyrins in 30% yield whereas the reaction of 2,5-bis-(α-arylhydroxymethyl)thiophenes with 5,10-diaryltripyrromethane or pyrrole gives 21,23-dithia-5,10,15,20-tetraarylporphyrins in 35% yield. Acidic ionic liquids are better catalyst and reaction media than acid catalysed reaction in organic solvents for the synthesis of core modified porphyrins. 相似文献
969.
Yogesh Kumar Bilash Kuila Dinesh Mahajan Prabhpreet Singh Balaram Mohapatra Gaurav Bhargava 《Tetrahedron letters》2014
A metal-free diastereoselective synthesis of novel 4-halo-3,6-di-aryl-2,6-diaza-bicyclo[3.2.0]heptan-7-one by intramolecular endo-trig haloamination of 3-amino-2-azetidinone is reported. The amidiolytic ring opening of diaza-bicyclo[3.2.0]heptan-7-one with sodium methoxide provides an easy access to previously unknown 4-halo-3-aryl amino-pyrrolidine-2-carboxylic acid methyl esters in good yields. 相似文献
970.
We report the synthesis of azobenzene template based sulfonamides 1 and 2 for capture of Human Carbonic Anhydrase II (HCAII). Out of these, 1 showed successful capturing of the protein, only when it is photo-isomerized to the Z form thus demonstrating the importance of spatial proximity of the reactive and selective functionalities. 相似文献