全文获取类型
收费全文 | 2022篇 |
免费 | 72篇 |
国内免费 | 4篇 |
专业分类
化学 | 1578篇 |
晶体学 | 26篇 |
力学 | 19篇 |
数学 | 88篇 |
物理学 | 387篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 24篇 |
2019年 | 33篇 |
2018年 | 26篇 |
2017年 | 17篇 |
2016年 | 45篇 |
2015年 | 49篇 |
2014年 | 53篇 |
2013年 | 72篇 |
2012年 | 117篇 |
2011年 | 144篇 |
2010年 | 95篇 |
2009年 | 77篇 |
2008年 | 90篇 |
2007年 | 113篇 |
2006年 | 126篇 |
2005年 | 122篇 |
2004年 | 92篇 |
2003年 | 101篇 |
2002年 | 88篇 |
2001年 | 51篇 |
2000年 | 31篇 |
1999年 | 37篇 |
1998年 | 13篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 30篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1984年 | 29篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 7篇 |
排序方式: 共有2098条查询结果,搜索用时 31 毫秒
1.
2.
3.
We developed two DNA-conjugated polymers, one based on polyallylamine and the other on polyacrylic acid, for use in DNA chips. A 30-mer single-stranded DNA probe and thioctic acid were covalently attached to polyallylamine as sidechains. The same single-stranded DNA and 3-(pyridyldithio)propionyl hydrazide were covalently attached to polyacrylic acid as sidechains. Both DNA-conjugated polymers could be specifically immobilized onto a gold sensor substrate by a self-assembly technique. The interactions between fully matched DNA and each DNA-conjugated polymer were investigated by surface plasmon resonance. A gold surface modified with either DNA-conjugated polymer recognized fully matched DNA much better than unmatched DNA. The hybridization selectivity and efficiency of DNA-conjugated polyallylamine was optimized by adjusting the pH so as to reduce the effects of cationic polymer sidechains. The hybridization selectivity and efficiency of DNA-conjugated polymers were higher than those of a conventional immobilized thiol-based DNA. The coating of DNA-conjugated polymers reduced nonspecific adsorption of DNA by the gold substrate. DNA-conjugated polyacrylic acid was more selective toward fully matched DNA than was DNA-conjugated polyallylamine. Therefore, DNA-conjugated polymers show promise for application in novel DNA chips. 相似文献
4.
5.
We fabricated high-quality InAlN/GaN heterostructures by metal–organic vapor phase epitaxy (MOVPE). X-ray diffraction measurements revealed that InAlN/GaN heterostructures grown under optimal conditions have flat surfaces and abrupt heterointerfaces. Electron mobility from 1200 to 2000 cm2/V s was obtained at room temperature. To our knowledge, this mobility is the highest ever reported for InAlN/GaN heterostructures. We also investigated the relationship between the Al composition and sheet electron density (Ns) for the first time. Ns increased from 1.0×1012 to 2.7×1013 cm−2 when the Al composition increased from 0.78 to 0.89. 相似文献
6.
XPS measurement revealed that the original state of TiO2 was changed to Ti2O3 and TiO by ion bombardment. TiO2 decreased and Ti2O3 increased at the initial stage. TiO increased at a later stage than Ti2O3. Each of them saturated after enough sputtering time.A formulation was proposed in order to explain the change of XPS spectra for oxides as a function of ion sputtering time. This formulation was based on reaction equations that contain two reduction processes (from TiO2 to Ti2O3 and from Ti2O3 to TiO), and sputtering effects. Using four fitting parameters (two reduction coefficients, sputtering yield and information depth), the present formula was fitted to the experimental results. The fitting results agree satisfactorily with the experimental results. The calculation shows that the reduction coefficient from TiO2 to Ti2O3 is about ten times larger than that from Ti2O3 to TiO. This calculation predicts that surface composition of an oxide that is changed by ion bombardment will reach a different value depending on its bulk composition. Moreover, the present formulation can determine the chemical states of compounds changed by ion bombardment. 相似文献
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.
Masayuki Kuzuya Akihiro Noguchi Hideki Ito Shin-Ichi Kondo Nahoko Noda 《Journal of polymer science. Part A, Polymer chemistry》1991,29(1):1-7
Plasma-induced polystyrene radicals were first studied by electron spin resonance (ESR). The room temperature ESR spectrum was compared with those obtained by γ-irradiation, UV-irradiation, and mechanical fracture. It was found that even less than a few seconds of plasma-irradiation gave rise to a large amount of polystyrene radicals and the ESR spectrum consisted of two types of spectra, a triplet and a single broad line. The spectral feature of the triplet was nearly identical with that of γ-irradiated polystyrene. Thus, it was assigned to the structure of a cyclohexadienyl-type radical formed by a nearly random addition of a hydrogen atom to the aromatic ring. The single broad line, thought to be an outline of multicomponent spectrum, was assigned to an immobilized dangling-bond sites at the plasma-induced crosslinked portion of the polystyrene surface. 相似文献
9.
The anti-tumor agent, tamoxifen, is easily synthesized by the successive allylation of benzaldehyde and the Friedel-Crafts alkylation reaction of anisole with the intermediary homoallyl silyl ethers, followed by the migration of the double bond to form the desired tetra-substituted ethylenes. Several derivatives of tamoxifen are also produced according to a similar synthetic strategy. 相似文献
10.
We developed DNA-conjugated polymer for DNA chip fabrication. A 30 mer probe DNA and disulfide bridges were covalently attached to the polymer side chain. The DNA-conjugated polymer can be specifically adsorbed on a gold substrate surface by a self-assembly technique. The interaction between fully matched DNA and DNA-conjugated polymer was investigated by surface plasmon resonance (SPR) technique. The DNA-conjugated polymer-modified gold surface highly recognized fully matched DNA, rather than unmatched DNA. Therefore, DNA-conjugated polymer can be used for novel DNA chip fabrication. 相似文献