全文获取类型
收费全文 | 2103篇 |
免费 | 52篇 |
国内免费 | 4篇 |
专业分类
化学 | 1291篇 |
晶体学 | 17篇 |
力学 | 41篇 |
数学 | 197篇 |
物理学 | 613篇 |
出版年
2024年 | 7篇 |
2023年 | 16篇 |
2022年 | 53篇 |
2021年 | 39篇 |
2020年 | 42篇 |
2019年 | 55篇 |
2018年 | 50篇 |
2017年 | 58篇 |
2016年 | 80篇 |
2015年 | 41篇 |
2014年 | 85篇 |
2013年 | 159篇 |
2012年 | 119篇 |
2011年 | 128篇 |
2010年 | 94篇 |
2009年 | 90篇 |
2008年 | 129篇 |
2007年 | 116篇 |
2006年 | 76篇 |
2005年 | 59篇 |
2004年 | 51篇 |
2003年 | 40篇 |
2002年 | 42篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 33篇 |
1992年 | 26篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 12篇 |
1987年 | 29篇 |
1986年 | 20篇 |
1985年 | 21篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 6篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1965年 | 7篇 |
排序方式: 共有2159条查询结果,搜索用时 15 毫秒
61.
62.
Mishra SR Leung WC Arroyo C Bachmann KT Blair RE Foudas C King BJ Lefmann WC Oltman E Quintas PZ Rabinowitz SA Sciulli FJ Seligman WG Shaevitz MH Merritt FS Oreglia MJ Schumm BA Bernstein RH Borcherding F Fisk HE Lamm MJ Marsh W Merritt KW Schellman H Yovanovitch DD Bodek A Budd HS de Barbaro P Sakumoto WK Sandler PH Smith WH 《Physical review letters》1992,69(24):3499-3502
63.
A. Ghosh K. S. Patel R. K. Mishra 《Journal of Radioanalytical and Nuclear Chemistry》1991,152(1):243-249
A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·104 1·mol–1·cm–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml–1. The system obeys Beer's law in the range of 0–5 g U·ml–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures. 相似文献
64.
The removal of Ce(III) from aqueous solutions by hydrous manganese oxide (HMO) and hydrous stannic oxide (HSO) was studied
as a function of concentrations (10−2−10−7 mol·dm−3) and pH (1.2–10.0) by using the radiotracer technique. The effects of co-ions and irradiation of HMO and HSO were also studied.
The uptake of Ce(III) fitted well with the Freundlich adsorption isotherm. No significant desorption of pre-adsorbed Ce(III)
in the studied temperature range (303–333 K) indicates that both the solids may be good adsorbents for the removal of Ce(III). 相似文献
65.
A 1,4-β-d-glucan cellobiohydrolase (EC 3.2.1.91) and l,4-β-d-glucan glucanohydrolase (EC 3.2.1.4) were purified from the culture filtrates ofPenicillium funiculosum by using preparative isoelectric focusing. Both the enzymes were homogeneous on polyacrylamide gel with and without sodium
dodecyl sulphate. The mol wt of the cellobiohydrolase and endoglucanase were 14,400 and 25,000 respectively. The purified
enzymes were free of β-glucosidase activity. Acting in isolation, the cellobiohydrolase had little capacity for solubilizing
Avicel or Walseth cellulose, but showed increased rates of hydrolysis when combined with endoglucanase. Cellobiose inhibition
(50%) was observed in the initial rate of the hydrolysis of Walseth cellulose. It was also observed that cellobiohydrolase
initiates the attack on crystalline cellulose.
† NCL communication no. 3898. 相似文献
66.
Rina Chun Saegun Kim Sang Hoon Han Ashok Kumar Pandey Neeraj Kumar Mishra In Su Kim 《Tetrahedron letters》2018,59(43):3848-3852
The site-selective C–H nitration reaction of 7-azaindoles with t-butyl nitrite under palladium catalysis is described. This protocol provides an efficient method for the construction of ortho-nitrated N-aryl-7-azaindoles with excellent site-selectivity and functional group compatibility. The formed 7-azaindole derivatives can be readily transformed into 7-azaindoles containing an aniline functional group under palladium-catalyzed hydrogenation conditions. 相似文献
67.
Graft copolymerization of methyl methacrylate onto wool was investigated in aqueous solution using the potassium peroxy-diphosphate-thiourea redox system as the initiator. The rate of grafting was determined by varying the monomer, peroxydi-phosphate ion, temperature, and solvent. The graft yield increases with increasing peroxydiphosphate ion up to 80 × 10?-4 mol/L, and with further increase of peroxydiphosphate ion the graft yield decreases. The graft yield increases with increasing monomer concentration. The percentage of grafting decreases with increasing thiourea concentration. The rate of grafting increases with an increase of temperature. The effect of acid and water-soluble solvent and certain salts on graft yield has been investigated and a suitable rate expression has been derived. 相似文献
68.
Someshwarnath Pandey Balakrishna Kolli Sarada P. Mishra Asit B. Samui 《Journal of polymer science. Part A, Polymer chemistry》2012,50(6):1205-1215
Three new types of siloxane‐based photoactive liquid crystalline polymers containing azo side groups were synthesized through the click chemistry route. The polymers having molecular weight range of 14,000–34,000 g mol?1 were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, and dichloromethane. The photoresponsive trans–cis photoisomerization under UV radiation and cis–trans relaxation process in dark for the polymers were studied. The isomerization rate constants were found to be 0.01–0.04 sec?1 and 1.16*10?4–4.67*10?4 sec?1, respectively. It has been noted that the polymers showed high intensity absorption for n‐π* in chloroform. Both trans and cis forms of azide monomers having azo moiety exhibited molar extinction coefficient ( ? max) in the range of 22,000–33,000 L mol?1 cm?1. The thermotropic behavior of the polymers was studied by polarizing optical microscope (POM) and differential scanning calorimetry (DSC) experiments. Polymer P1 showed liquid crystalline textures of nematic droplets, whereas P2 showed smectic focal conic texture and nematic droplets. Polymer P1 was also studied for photomechanical bending on exposure to UV radiation. The polymers showed initial degradation temperature in the range of 210–275°C. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
69.
Balakrishna Kolli Sarada P. Mishra M. P. Joshi S. Raj Mohan T. S. Dhami A. B. Samui 《Journal of polymer science. Part A, Polymer chemistry》2012,50(8):1572-1578
Four linear polymers containing pendant azo moiety were synthesized through click chemistry for second‐order nonlinear optical study. The polymers were found soluble in most of the polar organic solvents such as tetrahydrofuran (THF), chloroform, and dimethyl formamide (DMF). The polymers showed thermal stability up to 300 °C and glass transition temperatures (Tg) in the range of 120–140 °C. The molecular weights (Mw) of these polymers (measured by gel permeation chromatography) were in the range 37,900–55,000 g/mol. The polymers were found to form optically transparent films by solution casting from THF solution. Order parameters were calculated from UV–vis absorption spectra. The morphology changes in the films after poling were characterized by atomic force microscopy. The angular dependence, temperature dependence, and time dependence of second harmonic generation (SHG) intensity were obtained by using 1064 nm Nd:YAG laser. The SHG intensity remained unchanged up to 95 °C. At room temperature, it remained stable up to 8 days after initial drop of about 14%. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
70.