全文获取类型
收费全文 | 17726篇 |
免费 | 622篇 |
国内免费 | 302篇 |
专业分类
化学 | 7163篇 |
晶体学 | 377篇 |
力学 | 1175篇 |
综合类 | 9篇 |
数学 | 1717篇 |
物理学 | 8209篇 |
出版年
2023年 | 105篇 |
2022年 | 224篇 |
2021年 | 218篇 |
2020年 | 183篇 |
2019年 | 167篇 |
2018年 | 284篇 |
2017年 | 242篇 |
2016年 | 385篇 |
2015年 | 323篇 |
2014年 | 468篇 |
2013年 | 858篇 |
2012年 | 1033篇 |
2011年 | 1307篇 |
2010年 | 944篇 |
2009年 | 913篇 |
2008年 | 1024篇 |
2007年 | 1020篇 |
2006年 | 1031篇 |
2005年 | 816篇 |
2004年 | 717篇 |
2003年 | 562篇 |
2002年 | 557篇 |
2001年 | 970篇 |
2000年 | 657篇 |
1999年 | 540篇 |
1998年 | 373篇 |
1997年 | 376篇 |
1996年 | 296篇 |
1995年 | 237篇 |
1994年 | 227篇 |
1993年 | 180篇 |
1992年 | 195篇 |
1991年 | 170篇 |
1990年 | 158篇 |
1989年 | 121篇 |
1988年 | 98篇 |
1987年 | 91篇 |
1986年 | 75篇 |
1985年 | 83篇 |
1984年 | 64篇 |
1983年 | 40篇 |
1982年 | 31篇 |
1981年 | 31篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1975年 | 28篇 |
1974年 | 22篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Gérard D Berguiga L de Fornel F Salomon L Seassal C Letartre X Rojo-Romeo P Viktorovitch P 《Optics letters》2002,27(3):173-175
We report a study of the optical near field of an active integrated component operating near the 1.55-mum telecommunications wavelength. The device is based on a two-dimensional photonic crystal etched in a suspended InP membrane. Topographic as well as optical information is collected by use of a scanning near-field optical microscope in collection mode, providing information about the local distribution of the losses. 相似文献
982.
Kuzmann E. Nath A. Chechersky V. Li S. Wei Y. Chen X. Li J. Homonnay Z. Gál M. Garg V. K. Klencsár Z. Vértes A. 《Hyperfine Interactions》2002,139(1-4):631-639
57Fe transmission Mössbauer spectroscopy and X-ray diffractometry were used to study - and -polymorphs of iron phthalocyanines (FePc) to get information about their oxygenation in connection with controlled pyrolysis of flat layered phthalocyanines initiated by radicals at relatively low temperatures, to form acicular carbide particles encaged in carbon. Mössbauer spectroscopy and XRD revealed that the oxygenation of both - and -polymorphs of FePc was successfully achieved. New Mössbauer spectral components (doublets) appeared upon the oxygenation in both and FePc. This can be attributed to iron microenvironments containing oxygen between the layers of iron phthalocyanines. 相似文献
983.
Wang X. Yang S. Wang J. Li M. Jiang X. Du G. Liu X. Chang R.P.H. 《Optical and Quantum Electronics》2002,34(9):883-891
High quality ZnO film was deposited by plasma-assisted metal-organic chemical vapor deposition (MOCVD). We observed a dominant peak at 34.6° due to (0 0 2) ZnO, which indicated that the growth of ZnO film was strongly C-oriented. The full-width at half-maximum (FWHM) of the -rocking curve was 0.56° indicating relatively small mosaicity. Photoluminescence (PL) measurement was performed at both room temperature and low temperature. Ultraviolet (UV) emission at 3.30 eV was found with high intensity at room temperature while the deep level transition was weakly observed at 2.513 eV. The ratio of the intensity of UV emission to that of deep level emission was as high as 193, which implied high quality of ZnO film. From PL spectrum at 10 K, we observed A-exciton emission at 3.377 eV and D°X bound exciton transition at 3.370 eV. The donor–acceptor transition and LO phonon replicas were observed at 3.333 and 3.241 eV respectively. Raman scattering was performed in back scattering at room temperature. The E2, A1(LO) and A1(TO) mode was seen at 437.6, 575.8 and 380 cm–1 respectively. In comparison with Raman spectrum of ZnO powder, we found that ZnO film was nearly free of strain, which indicated high crystal quality. 相似文献
984.
Tang L.C. Chang C.C. Chen T.C. Yau H.F. Ye P.X. 《Optical and Quantum Electronics》2002,34(12):1241-1249
We propose a novel geometry for a self-pumped phase conjugator that uses a +c-face incident configuration in a photorefractive pentagon-shaped 0°-cut BaTiO3 crystal for obtaining fast response in phase conjugation. A steady phase-conjugate output with a fast response time 0.4 s is obtained when the incident beam has a 4 W/cm2 intensity. The influences of position and angle on the temporal phase-conjugate response are also investigated. The advantage of this phase conjugator using this novel configuration is improved resolution of a phase-distorted image with a value as high as 128 lp/mm. 相似文献
985.
B. Duan X. -Y. Gu Z. -Q. Ma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(1):9-12
The energies of some excited states with the total angular momentum L=0, 1 and 2. the total spin of two electrons S=0 and 1, and the even and odd parities are precisely calculated directly from the Schrödinger equation where the mass of the helium nucleus is finite. Moreover, we find that the solutions to the equation for the excited states have some more nodes, which can be used to distinguish the states with the same spectral term. 相似文献
986.
Silver ion-selective electrodes were prepared with polymeric membranes based on two calix[4]arene derivatives functionalized by two hydroxy and two benzothiazolylthioethoxy groups. The electrodes all gave a good Nernstian response of 58mV decade(-1) for silver in the activity range 5 x 10(-6)-10(-1) M, the limits of detection reached 10(-5.8) M and exhibited high selectivity towards alkali, alkaline earth and some transition metal ions. The electrode was used as indicator electrode in titrations of Ag+ with Cl- ion. 相似文献
987.
Asensio JL Cañada FJ Cheng X Khan N Mootoo DR Jiménez-Barbero J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(6):1035-1041
The conformational behavior of alpha-O-Man-(1-->1)-beta-Gal (1) and its C-analogue (2) has been studied using J/NOE NMR data, molecular mechanics, molecular dynamics, and ab initio calculations. The population distribution around the glycosidic linkages of 1 and 2 is rather different, especially for the alpha-Man linkage. A lower limit for the exo-anomeric effect in water has been experimentally determined. 相似文献
988.
Tamura S Fukamiya N Mou XY Mukainaka T Tokuda H Nishino H Tagahara K Koike K Lee KH Okano M 《Chemical & pharmaceutical bulletin》2000,48(6):876-878
Introduction of a senecioyl group into shinjulactones B and C, and esterification of the diosphenol moiety in brusatol and brucein A enhanced inhibitory effect against Epstein-Barr virus early antigen activation. 相似文献
989.
990.
Capillary zone electrophoresis is employed for the determination of caffeine using end-column amperometric detection with a carbon fiber microdisk array electrode at a constant potential of 1.45 V versus a saturated calomel electrode. The optimum conditions of separation and detection are 0.1 52mM NaH2PO4-0.648mM Na2HPO4 for the buffer solution, 20 kV for the separation voltage, 5 kV for the injection voltage, and 10s for the injection time. The limit of detection is 2.9 x 10(-4)mM or 1.2 fmol (signal-to-noise ratio = 2). The relative standard deviation is 0.68% for the migration time and 2.3% for the electrophoretic peak current. The method is applied to determining caffeine in human serum and a cola drink. 相似文献