全文获取类型
收费全文 | 1191篇 |
免费 | 36篇 |
国内免费 | 7篇 |
专业分类
化学 | 694篇 |
晶体学 | 30篇 |
力学 | 17篇 |
数学 | 95篇 |
物理学 | 226篇 |
无线电 | 172篇 |
出版年
2024年 | 5篇 |
2023年 | 11篇 |
2022年 | 43篇 |
2021年 | 30篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 24篇 |
2017年 | 33篇 |
2016年 | 50篇 |
2015年 | 23篇 |
2014年 | 35篇 |
2013年 | 75篇 |
2012年 | 66篇 |
2011年 | 60篇 |
2010年 | 55篇 |
2009年 | 45篇 |
2008年 | 53篇 |
2007年 | 44篇 |
2006年 | 58篇 |
2005年 | 56篇 |
2004年 | 52篇 |
2003年 | 34篇 |
2002年 | 36篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 22篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 22篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1969年 | 4篇 |
1959年 | 4篇 |
排序方式: 共有1234条查询结果,搜索用时 31 毫秒
1.
Chetan Bhadaliya Bala Krishna Panigrahy Dipanjan Goswami Sovan Maiti Sanjay Jagannath Gurule Arshad H. Khuroo 《Biomedical chromatography : BMC》2022,36(4):e5337
A selective, highly sensitive, precise, and novel bioanalytical method has been developed and validated to quantify sinococuline, an active constituent present in the phytopharmaceutical drug product containing Cocculus hirsutus plant extract, in vivo. Chromatographic separation was achieved on a Luna Omega Polar-C18 bonded analytical column maintained at 45°C. The isocratic mobile phase consisted of methanol and ammonium formate buffer (60:40, v/v) at acidic pH with a low flow rate of 0.250 mL/min. Detection was performed on an API 4000 mass spectrometer using electrospray ionization in positive polarity and multiple reaction monitoring mode to achieve a lower limit of quantification of 1.50 ng/mL. Excellent accuracy and precision were obtained after extracting the analyte from plasma samples using a chemical analogue as an internal standard in the absence of an isotope-labeled compound. The extraction efficacy was evidenced from recovery study, and the analyte was found to be stable in plasma. Validation study demonstrated linearity with coefficient of correlation, r ≥ 0.99, and minimal matrix effect. This bioanalytical method was successfully applied to evaluate pharmacokinetic parameters of sinococuline from a phase I clinical trial of an aqueous extract of C. hirsutus in healthy human volunteers. 相似文献
2.
S. Venkatesan S. Suresh P. Ramu M. Kandasamy J. Arumugam S. Thambidurai K.M. Prabu N. Pugazhenthiran 《印度化学会志》2022,99(5):100436
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications. 相似文献
3.
Simon G. Bott Alan P. Marchand Dongxia Xing Rajesh Shukla Stephen James Obrey K. Venkatesan J. Narasimha Moorthy 《Journal of chemical crystallography》1997,27(11):661-665
NaBH4 reduction of a cage dione proceeds in a stereospecific fashion to give theendo,endo-diol. This reactivity is related to the crystal structure. 相似文献
4.
5.
Structural and electrical properties of brush plated ZnTe films 总被引:1,自引:0,他引:1
Zinc telluride thin films were deposited by the brush plating technique at a potential of −0.90 V (SCE) on conducting glass and titanium substrates at different temperatures in the range 30–90 °C. The films were polycrystalline in nature with peaks corresponding to the cubic phase. Direct band gap of 2.30 eV was observed. XPS studiers indicated the formation of ZnTe. Depth profiling studies indicated a uniform distribution of Zn and Te throughout the entire thickness. EDAX measurements were made on the films and it was found that there was a slight excess of Te. The carrier concentration was found to vary from 1014–1015 cm−3 with increase of substrate temperature. The mobility was found to vary from 5 to 60 cm2 V−1 s−1. 相似文献
6.
V. Murali 《Journal of Applied Mathematics and Computing》2006,20(1-2):409-420
7.
Wave propagation in a piezoelectric human bone of arbitrary cross section with a circular cylindrical cavity 总被引:1,自引:0,他引:1
A theoretical study of wave propagation in a piezoelectric cylinder of infinite length of arbitrary cross section with a circular cylindrical cavity of class 6 is investigated. The frequency equations are obtained by using the Fourier expansion collocation method and are analyzed numerically. The frequencies are evaluated for circular, elliptic, and cardioidal sections of bone and are tabulated. A plot of frequency spectrum is also presented for the cardioidal cross-section bar. 相似文献
8.
Sharmin Kharrazi S.W. Gosavi T. Venkatesan J. Urban S.-W. Cheong 《Solid State Communications》2006,138(8):395-398
We report on the synthesis of TbMnO3 nanoparticles by chemical co-precipitation route and their structural, chemical bonding, magnetic and dielectric properties. It is shown that the interesting multiferroic properties of this system as reflected by the concurrent occurrence of magnetic and dielectric transitions are retained in the nanoparticles (size∼40 nm). However, the nanoparticle constitution and properties are seen to depend significantly on the calcination temperature. While the nanoparticles obtained by calcination at 800 °C correspond very well with the reported properties of single phase TbMnO3 (all the key magnetic and dielectric features near 7, 27 and 41 K, albeit with reduced dielectric constant) the nanoparticles obtained by calcination at 900 °C develop a Tb deficient skin which softens the transitions, reducing the dielectric constant further. 相似文献
9.
10.