全文获取类型
收费全文 | 438247篇 |
免费 | 3831篇 |
国内免费 | 1092篇 |
专业分类
化学 | 235587篇 |
晶体学 | 7226篇 |
力学 | 19079篇 |
综合类 | 19篇 |
数学 | 47582篇 |
物理学 | 133677篇 |
出版年
2020年 | 3588篇 |
2019年 | 3968篇 |
2018年 | 5039篇 |
2017年 | 5096篇 |
2016年 | 7505篇 |
2015年 | 4561篇 |
2014年 | 7316篇 |
2013年 | 18616篇 |
2012年 | 13640篇 |
2011年 | 16669篇 |
2010年 | 11898篇 |
2009年 | 11718篇 |
2008年 | 15354篇 |
2007年 | 15405篇 |
2006年 | 14393篇 |
2005年 | 13009篇 |
2004年 | 11963篇 |
2003年 | 10957篇 |
2002年 | 10653篇 |
2001年 | 12382篇 |
2000年 | 9527篇 |
1999年 | 7318篇 |
1998年 | 6161篇 |
1997年 | 6119篇 |
1996年 | 5779篇 |
1995年 | 5402篇 |
1994年 | 5443篇 |
1993年 | 5025篇 |
1992年 | 6042篇 |
1991年 | 5950篇 |
1990年 | 5855篇 |
1989年 | 5711篇 |
1988年 | 5869篇 |
1987年 | 5756篇 |
1986年 | 5445篇 |
1985年 | 7143篇 |
1984年 | 7401篇 |
1983年 | 6072篇 |
1982年 | 6233篇 |
1981年 | 6200篇 |
1980年 | 6025篇 |
1979年 | 6270篇 |
1978年 | 6572篇 |
1977年 | 6562篇 |
1976年 | 6470篇 |
1975年 | 5954篇 |
1974年 | 5975篇 |
1973年 | 6084篇 |
1972年 | 4266篇 |
1968年 | 3600篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
52.
The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques. 相似文献
53.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
54.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
55.
G. Dattoli 《Journal of Mathematical Analysis and Applications》2002,269(2):716-725
Bilateral generating functions are those involving products of different types of polynomials. We show that operational methods offer a powerful tool to derive these families of generating functions. We study cases relevant to products of Hermite polynomials with Laguerre, Legendre and other polynomials. We also propose further extensions of the method which we develop here. 相似文献
56.
K Kawasaki T Tsuji K Hirase M Miyano Y Imoto M Iwamoto 《Chemical & pharmaceutical bulletin》1991,39(3):584-589
N-Terminal tripeptide analogs of fibrin alpha-chain were synthesized and their inhibitory effect on fibrinogen/thrombin clotting was examined. A new water-soluble active ester, 3-pyridinium ester, was used for the synthesis. Among the synthetic peptides, H-Gly-Pro-Arg-hexamethyleneimine exhibited the highest inhibitory effect on fibrinogen-thrombin clotting. 相似文献
57.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991. 相似文献
58.
K. A. Bronnikov 《Annalen der Physik》1991,503(8):527-534
A multidimensional generalization of the Reissner-Nordström solution of general relativity is obtained for the case of n Ricci-flat internal spaces. A two-parameter family of black-hole solutions for an arbitrary dimensionality D is selected. Nontrivial black holes with D > 4 are shown to exist only with a nonzero electric charge. Observational consequences are discussed, in particular, a violation of Coulomb's law. 相似文献
59.
60.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献