全文获取类型
收费全文 | 2949篇 |
免费 | 82篇 |
国内免费 | 15篇 |
专业分类
化学 | 2366篇 |
晶体学 | 28篇 |
力学 | 29篇 |
数学 | 199篇 |
物理学 | 374篇 |
综合类 | 50篇 |
出版年
2023年 | 18篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 42篇 |
2019年 | 42篇 |
2018年 | 26篇 |
2017年 | 23篇 |
2016年 | 56篇 |
2015年 | 53篇 |
2014年 | 89篇 |
2013年 | 183篇 |
2012年 | 142篇 |
2011年 | 181篇 |
2010年 | 122篇 |
2009年 | 106篇 |
2008年 | 184篇 |
2007年 | 171篇 |
2006年 | 192篇 |
2005年 | 191篇 |
2004年 | 172篇 |
2003年 | 144篇 |
2002年 | 146篇 |
2001年 | 50篇 |
2000年 | 41篇 |
1999年 | 24篇 |
1998年 | 38篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 29篇 |
1993年 | 14篇 |
1992年 | 23篇 |
1991年 | 16篇 |
1989年 | 11篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 15篇 |
1985年 | 33篇 |
1984年 | 46篇 |
1983年 | 26篇 |
1982年 | 37篇 |
1981年 | 42篇 |
1980年 | 26篇 |
1979年 | 25篇 |
1978年 | 17篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 15篇 |
1974年 | 16篇 |
1973年 | 11篇 |
排序方式: 共有3046条查询结果,搜索用时 15 毫秒
11.
Toshikazu Kurosaki Osamu Takahashi Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1974,12(7):1407-1420
Polymers having stable pendant . radicals were synthesized through their precursor polymers by oxidizing them in air or by H2O2–Na2WO4. Hydrochlorides and sulfates of 4-methacryloylamino- and 4-methacryloyloxy-1-hydroxy-2,2,6,6-tetramethylpiperidines were synthesized as precursor monomers and polymerized by using α,α′-azobisisobutyronitrile under appropriate conditions to precursor polymers of high molecular weight: poly-4-methacryloylamino-/oxy-1-hydroxy-2,2,6,6-tetramethylpiperidinehydrochlorides and sulfates. The precursor polymers were converted to polymers having nitroxyl stable radicals, i.e., poly-4-methacryloylamino-/oxy-2,2,6,6-tetramethylpiperidine-1-oxyls, by oxidation in air or with H2O2–Na2WO4 without any main-chain scission. The structure of the resultant stable radical polymers was determined by infrared, ultraviolet, and ESR spectroscopy. Based on the results of spectroscopic analysis and Kjeldahl analysis, the transformation from precursors to nitroxyl stable radical polymers was found to be quantitative. Investigations on the applicability of polymeric nitroxyl radicals to oxidation-reduction reactions were attempted by means of polarography; the reduction half-wave potential was found to be ?1.16 V for the mercury pool. 相似文献
12.
The polymerization of isobutyl vinyl ether was studied in a heterogeneous system using iron (II) sulfate calcined in air at various temperatures as a catalyst. The maximum activity was shown by the catalyst calcined at 700°C, which effected the polymerization at room temperature in a few seconds, while the sulfate treated at 750°C was totally inactive. Poly(vinyl ethyl ether) was also obtained by the FeSO4 (700°C) catalyst at room temperature. This catalyst formed the crystalline polymer (melting temperature 135–138°C) when the reaction was performed in toluene as solvent at room temperature. Poisoning experiments with Hammett indicators were carried out with the FeSO4 (700°C) catalyst. The treatment with n-butylamine rendered it inactive in the reaction of isobutyl vinyl ether, while its catalytic activity was little affected by dicinnamalacetone. On the basis of the observed results, the nature of active sites of catalyst is discussed. 相似文献
13.
Post-biotinylation of the alkyl azide derivative of trifluoromethyl phenyldiazirine (TPD) was elucidated to apply a photoaffinity biotinylation technique. A photo-modified polyvinilidene difluoride (PVDF) membrane was used as a photolabeled component and we introduced biotin by Staudinger-Bertozzi ligation. The 15 pmol amount of biotinylated reagent was still effective for the visualization of cross-linked product on the matrix. The results show the potential utility of alkyl azide carrying TPD derivatives in the application of photoaffinity biotinylation, which could be useful for the ligands with tight structural requirements. 相似文献
14.
15.
Numerical Algorithms - In this paper, we propose an infeasible arc-search interior-point algorithm for solving nonlinear programming problems. Most algorithms based on interior-point methods are... 相似文献
16.
Sung Il Hong Toshikazu Kurosaki Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1972,10(11):3405-3419
Polyoxime-urethanes have been synthesized from dioximes and diisocyanates, and their structures have been ascertained by elemental analysis and infrared spectroscopy. They can be represented by the general formula: These polymer films were photolyzed by using a high-pressure 100-W mercury lamp, and the rate of decomposition of the N? O bond was determined by use of ultraviolet and infrared spectra, or comparing the photochemical behavior with that of corresponding model compounds. Upon irradiating these polymers in the presence or absence of sensitizers or a hydrogen donor, there were obtained photolyzed polymers of low molecular weight, of which the molecular weights were estimated by observing the viscosity changes. To deduce the mechanism of photodegradation of polyoxime-urethane, photolysis of benzophenone oxime-phenyl urethane was investigated as a model compound. 相似文献
17.
Yoko Nambu Takeshi Endo Makoto Okawara 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):1937-1943
Reductive S-monoacylation of lipoamide with some carboxylic acids and tri-n-butylphosphine was carried out in acetonitrile to obtain the corresponding S-monoacylated compounds in excellent yield. This method was applied to the preparation of S-monoacylated dihydrolipoyl polymer with a neighboring thiol group. The acyl transfer from the polymer to cyclohexylamine was enhanced as much as 64 times by adding silver perchlorate. 相似文献
18.
The proposed structures of patellamides B and C, cytotoxic lipophilic cyclic peptides from a marine tunicate, have been revised on the basis of the spectral data of their partial hydrolysates, and their revised structures have been synthetically confirmed by the use of diphenyl phosphorazidate(DPPA) and diethyl phosphorocyanidate(DEPC). 相似文献
19.
20.