全文获取类型
收费全文 | 58139篇 |
免费 | 3769篇 |
国内免费 | 2567篇 |
专业分类
化学 | 33582篇 |
晶体学 | 935篇 |
力学 | 2912篇 |
综合类 | 189篇 |
数学 | 5854篇 |
物理学 | 21003篇 |
出版年
2023年 | 466篇 |
2022年 | 814篇 |
2021年 | 1079篇 |
2020年 | 1142篇 |
2019年 | 1127篇 |
2018年 | 1203篇 |
2017年 | 1152篇 |
2016年 | 1694篇 |
2015年 | 1391篇 |
2014年 | 1830篇 |
2013年 | 3124篇 |
2012年 | 3292篇 |
2011年 | 3785篇 |
2010年 | 2598篇 |
2009年 | 2551篇 |
2008年 | 2945篇 |
2007年 | 2821篇 |
2006年 | 2554篇 |
2005年 | 2129篇 |
2004年 | 1879篇 |
2003年 | 1618篇 |
2002年 | 1542篇 |
2001年 | 1780篇 |
2000年 | 1405篇 |
1999年 | 1259篇 |
1998年 | 1015篇 |
1997年 | 990篇 |
1996年 | 948篇 |
1995年 | 828篇 |
1994年 | 818篇 |
1993年 | 659篇 |
1992年 | 711篇 |
1991年 | 695篇 |
1990年 | 619篇 |
1989年 | 545篇 |
1988年 | 559篇 |
1987年 | 524篇 |
1986年 | 468篇 |
1985年 | 524篇 |
1984年 | 527篇 |
1983年 | 387篇 |
1982年 | 423篇 |
1981年 | 402篇 |
1980年 | 349篇 |
1979年 | 417篇 |
1978年 | 388篇 |
1977年 | 402篇 |
1976年 | 396篇 |
1975年 | 349篇 |
1973年 | 345篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
93.
Comprehensive studies of X-ray diffraction, oxygen content, superconductivity and Mössbauer effect have been made on FexCu1−xBa2YCu2O7+y superconductors (0.00≤x≤0.70) synthesized by ambient (AM) and high pressure (HP). Results indicate that all the HP-samples have tetragonal structure, smaller lattice parameter c and unit-cell volume than the AM-samples. The studies of oxygen content, and Mössbauer spectroscopy indicate that the HP-samples have higher oxygen content, carrier concentration and average valence of Fe than the AM-samples. Moreover, for the HP-samples more Fe atoms located in CuOx chains have fivefold-oxygen coordination. These are important reasons for the enhancement of Tc in the HP-samples. 相似文献
94.
95.
I. A. Uspenskaya Z. S. Vakhovskaya M. M. Efremova M. L. Kovba A. L. Emelina Zh. V. Dobrokhotova Yu. V. Goryushkina L. A. Tiflova A. A. Popova A. S. Monaenkova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):529-534
The thermodynamic properties of the Ln2BaO4 phases (Ln = Dy, Ho, Sm) were studied by the electromotive force method with a fluoride electrolyte (890–1180 K), solution calorimetry in 1.07 N hydrochloric acid at 298.15 K, and differential scanning calorimetry (298–860 K). The experimental data were jointly processed, and the thermodynamic functions of the compounds over the temperature range 298–1200 K were calculated. 相似文献
96.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance. 相似文献
97.
Z. Karaoglanov 《Fresenius' Journal of Analytical Chemistry》1941,121(5-6):190-209
Ohne Zusammenfassung 相似文献
98.
A. Sanusi M. Z. A. Yahya S. Navaratnam W. J. Basirun Y. Alias N. S. Mohamed A. K. Arof 《Ionics》2003,9(3-4):253-257
In this study, lead sulphide (PbS) was prepared by the chemical bath deposition technique. The sample was characterized by
X-ray diffraction (XRD), Energy Dispersive Analysis of X-rays (EDAX) and cyclic voltammetry. EDAX spectrum shows peaks attributable
to lead and sulphur. The EDAX analysis also shows that the prepared sample is stoichiometric. Cyclic voltammetry experiments
were recorded at 100 mV·s−1 and 400 mV·s−1 scan rates. Results show that the rate controlling electrochemical reaction is electron transfer. The presence of redox waves
shows that the lithium intercalation and deintercalation can occur as a result of lattice expansion in PbS. There were no
differences in the PbS XRD data before and after the cyclic voltammetry experiments indicating that the PbS structure is not
modified upon lithium ion intercalation and deintercalation in PbS. The discharge characteristics for 35 cycles of the cell
using the LiCoO2/PbS couple is presented indicating the possible development of such materials as anode in lithium ion cells. 相似文献
99.
Haibo Peng Boyu Wu Qiong Song Fei Lu Shuyun Luo 《International Journal of Infrared and Millimeter Waves》2003,24(9):1587-1596
Hybrid electrode combined coplanar waveguide (CPW) and microstrip lines in ultra-broadband electro-optic modulators. The characteristics of the modulators with hybrid electrode is like that of the modulator with the microstrip lines, in which the microstrip electrode is loaded above only one arm of Mach-Zehnder (M-Z) optical waveguide, besides the problem of microstrip line to coaxial transition and corona polarization in polymer modulators have been best solved at the same time. By using finite element method (FEM), the characteristic parameters such as half-wave voltage, modulation bandwidth characteristic impedance, effective microwave refractive index of polymer modulators with microstrip line and hybrid electrode are analysed and compared in this paper. The results present that velocity match, impendence match and lower microwave propagating loss is easily realized in modulators with hybrid electrode. 相似文献
100.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献