全文获取类型
收费全文 | 236208篇 |
免费 | 6974篇 |
国内免费 | 4994篇 |
专业分类
化学 | 130392篇 |
晶体学 | 3587篇 |
力学 | 11445篇 |
综合类 | 325篇 |
数学 | 25110篇 |
物理学 | 77317篇 |
出版年
2022年 | 2127篇 |
2021年 | 2896篇 |
2020年 | 3355篇 |
2019年 | 3602篇 |
2018年 | 4302篇 |
2017年 | 4248篇 |
2016年 | 5756篇 |
2015年 | 3797篇 |
2014年 | 5607篇 |
2013年 | 10624篇 |
2012年 | 9589篇 |
2011年 | 10967篇 |
2010年 | 8151篇 |
2009年 | 8162篇 |
2008年 | 9836篇 |
2007年 | 9365篇 |
2006年 | 8890篇 |
2005年 | 8037篇 |
2004年 | 7238篇 |
2003年 | 6606篇 |
2002年 | 6607篇 |
2001年 | 7875篇 |
2000年 | 5828篇 |
1999年 | 4552篇 |
1998年 | 3547篇 |
1997年 | 3430篇 |
1996年 | 3241篇 |
1995年 | 2891篇 |
1994年 | 2943篇 |
1993年 | 2685篇 |
1992年 | 3155篇 |
1991年 | 3277篇 |
1990年 | 3120篇 |
1989年 | 2997篇 |
1988年 | 2865篇 |
1987年 | 2879篇 |
1986年 | 2662篇 |
1985年 | 3161篇 |
1984年 | 3178篇 |
1983年 | 2620篇 |
1982年 | 2584篇 |
1981年 | 2351篇 |
1980年 | 2323篇 |
1979年 | 2715篇 |
1978年 | 2806篇 |
1977年 | 2742篇 |
1976年 | 2803篇 |
1975年 | 2585篇 |
1974年 | 2589篇 |
1973年 | 2602篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
H. Glatzel R. Schneider T. Fauster V. Dose 《Zeitschrift für Physik B Condensed Matter》1992,88(1):53-61
Inverse photoemission spectra were taken for thin epitaxial iron films on Cu(100). For a film thickness of eight monolayers the observed electronic states are characteristic for a fcc(100) surface. Thed-bands of iron show a ferromagnetic exchange splitting of 1.1 eV, considerably smaller than the bulk value of 1.8 eV, which we observe for film thicknesses above 18 monolayers. 相似文献
992.
A. T. Barabanov G. A. Agranovich A. S. Golikov 《Journal of Mathematical Sciences》1992,60(2):1399-1402
A problem of constructing algorithms of optimal estimation of states of a discrete system accounting for deterministic and stochastic measurements is considered. A low order estimation algorithm is proposed in the form of a two-stage procedure for each instant of time obtained by direct application of the Kaiman optimal filtering algorithm.Translated from Dinamicheskie Sistemy, No. 4, pp. 85–89, 1985. 相似文献
993.
T. ISHITAKEY. MIYAZAKI R. NOGUCHIH. ANDO T. MATOBA 《Journal of sound and vibration》2002,253(1):31-36
The aim of this study was to investigate the effects of exposure to whole-body vibration (WBV) and the ISO 2631/1-1997 frequency weighting on gastric motility. The gastric motility was measured by electrogastrography (EGG) in nine healthy volunteers. Sinusoidal vertical vibration at a frequency of 4, 6·3, 8, 12, 16, 31·5, or 63 Hz was given to the subjects for 10 min. The magnitude of exposure at 4 Hz was 1·0m/s2 (r.m.s.). The magnitudes of the other frequencies gave the same frequency-weighted acceleration according to ISO 2631/1-1997. The pattern of the dominant frequency histogram (DFH) was changed to a broad distribution pattern by vibration exposure. Vibration exposure had the effect of significantly reducing the percentage of time for which the dominant component had a normal rhythm and increasing the percentage of time for which there was tachygastria (p<0·05). Vibration exposure generally reduced the mean percentage of time with the dominant frequency in normal rhythm component. There was a significant difference between the condition of no vibration and exposure to 4 and 6·3 Hz of vibration frequency (p<0·05). The frequency weighting curve given in ISO 2631/1-1997 was not adequate for use in evaluating the physiological effects of WBV exposure on gastric motility. 相似文献
994.
一类广义维里拉普拉斯,把在白噪声分析构架中通常定义的维里拉普拉斯作为特殊情形而包含。 相似文献
995.
A broad range echelle spectrograph with a CCD matrix detector is developed for different applications in atomic spectroscopy. The compact optical design in combination with a dispersive entrance slit illumination offers a low stray light level and high throughput in the UV spectral region comparable only with spectrographs of higher focal length. Ray tracing calculations for typical wavelengths and the multi-line spectrum of an iron arc show the excellent overall spectrum quality. The subtraction of two partial spectra of different steel alloys demonstrates the spectra evaluation possibilities of the CCD spectrograph. 相似文献
996.
997.
M. A. Yurovskaya I. G. Khamlova V. N. Nesterov O. V. Shishkin Yu. T. Struchkov 《Chemistry of Heterocyclic Compounds》1995,31(11):1339-1345
X-ray structural data has shown that condensation of sym-3-nitrocollidine with benzaldehyde occurs at the 6-methyl group. The presence of an acceptor group in the side chain of 2,6-dimethyl-4-cyanomethyl-3-nitropyridine causes condensation to occur at the activated methylene group in the 4-position.M. V. Lomonosov State University, Moscow 119899. A. N. Nesmeyanov Institute of Organoelemental Compounds, Moscow 117813. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11. pp. 1543–1550, November, 1995. Original article submitted June 10, 1995. 相似文献
998.
Yu. Dryagin N. Scalyga T. Geist 《International Journal of Infrared and Millimeter Waves》1996,17(7):1199-1204
The construction of a notch-filter for 140 GHz with very low passband insertion loss is described. It is based on a single-mode rectangular waveguide and cylindrical cavities matched to it. The typical transmission characteristic is also presented. 相似文献
999.
Minimax estimates for functionals of solutions of wave equations with time-periodic right-hand sides
L. T. Adzhubey O. G. Nakonechy Yu. K. Pidlypenko 《Journal of Mathematical Sciences》1995,77(5):3452-3457
Minimax mean-square estimates for the velocity potential in the steady regime, as well as for the intensities of harmonic
ponts sources, are obtained from the results of inaccurate measurements of the potential. Bibliography: 4 titles.
Translated fromObchyslyuval’na ta Prykladna Matematyka, No. 77, 1993, pp 87–96. 相似文献
1000.