全文获取类型
收费全文 | 3165篇 |
免费 | 116篇 |
国内免费 | 10篇 |
专业分类
化学 | 2506篇 |
晶体学 | 31篇 |
力学 | 58篇 |
数学 | 129篇 |
物理学 | 567篇 |
出版年
2023年 | 17篇 |
2022年 | 29篇 |
2021年 | 32篇 |
2020年 | 51篇 |
2019年 | 54篇 |
2018年 | 40篇 |
2017年 | 20篇 |
2016年 | 73篇 |
2015年 | 56篇 |
2014年 | 61篇 |
2013年 | 137篇 |
2012年 | 172篇 |
2011年 | 178篇 |
2010年 | 101篇 |
2009年 | 132篇 |
2008年 | 185篇 |
2007年 | 144篇 |
2006年 | 175篇 |
2005年 | 196篇 |
2004年 | 151篇 |
2003年 | 126篇 |
2002年 | 109篇 |
2001年 | 55篇 |
2000年 | 73篇 |
1999年 | 50篇 |
1998年 | 32篇 |
1997年 | 39篇 |
1996年 | 42篇 |
1995年 | 27篇 |
1994年 | 41篇 |
1993年 | 27篇 |
1992年 | 44篇 |
1991年 | 23篇 |
1990年 | 30篇 |
1989年 | 28篇 |
1988年 | 29篇 |
1987年 | 43篇 |
1986年 | 30篇 |
1985年 | 37篇 |
1984年 | 34篇 |
1983年 | 29篇 |
1982年 | 40篇 |
1981年 | 37篇 |
1980年 | 39篇 |
1979年 | 37篇 |
1978年 | 26篇 |
1977年 | 33篇 |
1976年 | 26篇 |
1975年 | 20篇 |
1973年 | 17篇 |
排序方式: 共有3291条查询结果,搜索用时 15 毫秒
1.
Jigneshkumar P. Patel Zou Guo Xiang Shaw Ling Hsu Andrew B. Schoch Sena Ada Carleen Dean Matsumoto 《Journal of Polymer Science.Polymer Physics》2015,53(21):1519-1526
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1519–1526 相似文献
2.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
3.
4.
Takanori MiyashitaNoritake Matsumoto Tomohisa MoriguchiKazuo Shinozuka 《Tetrahedron letters》2003,44(40):7399-7402
A novel phosphoramidite synthon of a dinucleoside phosphotriester unit bearing an intercalative moiety at its internucleotide linkage in a stereospecific manner was prepared and successfully incorporated into the middle portion of α-β chimeric oligoDNA. One of the resulting stereoisomeric chimera DNAs strongly enhances the thermal stability of an alternate-stranded triplex formed between the chimera and a double-stranded DNA. 相似文献
5.
Tetsuro Saeki Takahiro Tamesue Shizuma Yamaguchi Kazuya Sunada 《Applied Acoustics》2004,65(2):203-210
This paper focuses on masking speech with meaningless steady noise as a way of realizing a comfortable sound environment. As a basis for research, meaningless steady noise at minimum sound pressure levels for masking of male or female meaningful speech is considered, based on psychological experiments using a method of adjustment. From the results, band-limited pink noise can be selected as the most effective noise for masking of speech. In the case of speech with a lower sound pressure level, the sound pressure level of the meaningless steady noise needs to be a little higher. 相似文献
6.
7.
We have recently reported on dodecamer peptides (HPPMDFHKAMTR, CHPQPLKSRNPL) which recognize 52-58th and 197-203rd amino acid sequences of glucose oxidase (GOx) by screening via a phage random peptide library. In this study, a side-chain protected peptide monomer (PPM) was synthesized using two peptides (HPPMDFHKAMTR, SHPQPLKSRNPL) and acryloyl chloride. The peptide-conjugated polymer (PCP) was copolymerized with PPMs and N,N-diethylacrylamide (DEAA). The affinity of PCPs to GOx was estimated using surface plasmon resonance detection. This study suggests that PCP is a valuable molecular recognition biomolecule. 相似文献
8.
Y Watanabe M Suda Y Matsumoto K Takayama M Matsumoto W Zhao 《Chemical & pharmaceutical bulletin》1991,39(9):2391-2394
The dissolution behavior of the aspirin enteric granule prepared using acylglycerols, glyceryl monostearate (GMS) and glyceryl trilaurate (GTL), was investigated in vitro and in human subjects in a fasting or non-fasting state. Aspirin was slowly released from the granule in vitro at pH 1.2. No acceleration of the aspirin dissolution rate in the medium without lipase and cholic acid was observed when the pH level of the medium increased to a neutral region (pH 6.4). However, the dissolution of aspirin was significantly increased by increasing the concentrations of lipase and cholic acid in the medium. Lipase appears to play an essential role in the dissolution process of aspirin granules. In human subjects, the average levels of the cumulative amount of total salicylate excreted in a urine-time curve, and the mean residence time (MRT) obtained after oral administration of a granule in the fasting state were markedly delayed in comparison with the results observed using an aqueous solution and a crystalline form of aspirin. In comparing the fasting condition with the non-fasting condition (after food ingestion), no significant difference was recognized in the total amount of salicylate excreted in urine to an infinite time (Ae(infinity)), whether the MRT was obtained by granule, crystalline form or aqueous solution. It can be concluded that aspirin granule prepared by GMS and GTL has a property of pancreatic lipase-sensitive dissolution, and its bioavailability is unaffected by food intake. 相似文献
9.
10.