全文获取类型
收费全文 | 361594篇 |
免费 | 11623篇 |
国内免费 | 6585篇 |
专业分类
化学 | 207713篇 |
晶体学 | 5964篇 |
力学 | 15371篇 |
综合类 | 344篇 |
数学 | 36583篇 |
物理学 | 113827篇 |
出版年
2022年 | 3539篇 |
2021年 | 4078篇 |
2020年 | 4549篇 |
2019年 | 4610篇 |
2018年 | 4625篇 |
2017年 | 4625篇 |
2016年 | 7216篇 |
2015年 | 5699篇 |
2014年 | 7793篇 |
2013年 | 17220篇 |
2012年 | 14156篇 |
2011年 | 16458篇 |
2010年 | 11263篇 |
2009年 | 10812篇 |
2008年 | 13763篇 |
2007年 | 13306篇 |
2006年 | 12633篇 |
2005年 | 11616篇 |
2004年 | 10127篇 |
2003年 | 9119篇 |
2002年 | 8683篇 |
2001年 | 9872篇 |
2000年 | 7636篇 |
1999年 | 6389篇 |
1998年 | 5164篇 |
1997年 | 5040篇 |
1996年 | 4944篇 |
1995年 | 4662篇 |
1994年 | 4241篇 |
1993年 | 3989篇 |
1992年 | 4726篇 |
1991年 | 4596篇 |
1990年 | 4406篇 |
1989年 | 4351篇 |
1988年 | 4288篇 |
1987年 | 4320篇 |
1986年 | 4101篇 |
1985年 | 5314篇 |
1984年 | 5337篇 |
1983年 | 4314篇 |
1982年 | 4656篇 |
1981年 | 4557篇 |
1980年 | 4352篇 |
1979年 | 4680篇 |
1978年 | 4769篇 |
1977年 | 4803篇 |
1976年 | 4674篇 |
1975年 | 4372篇 |
1974年 | 4189篇 |
1973年 | 4364篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
M Lepère R Gobeille V.Malathy Devi M.A.H Smith B Aoaeh A.W Mantz 《Journal of Molecular Spectroscopy》2004,224(1):7-12
We have analyzed the methyl fluoride RQ(J,0)Q branch lines located near 1475 cm−1 using a simultaneous multi-spectrum fitting technique. In this analysis we have used previously recorded diode-laser data in which we collected many data points covering only one or two Q branch lines in a particular run. The analysis consists of simultaneously fitting 57 spectra collected with numerous pressure and path length conditions for all absorption lines. The data are concatenated to create one continuous spectrum of the Q branch. We have determined the intensity and self-broadened widths at 296 K for 23 RQ(J,0) lines. 相似文献
92.
93.
W. Hampe 《Fresenius' Journal of Analytical Chemistry》1885,24(1):588-590
Ohne Zusammenfassung 相似文献
94.
The rate constants k1 for the reaction of CF3CF2CF2CF2CF2CHF2 with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm3 reaction chamber with either CHF2Cl or CH2FCF3 as a reference compound. OH radicals were produced by UV photolysis of an O3–H2O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k1 (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10?15 cm3 molecule?1 s?1 (FP‐LIF method) and (1.72 ± 0.07) × 10?15 cm3 molecule?1 s?1 (LP‐LIF method), whereas the K1 (298 K) values determined by the relative method were (1.87 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CHF2Cl reference) and (2.12 ± 0.11) × 10?15 cm3 molecule?1 s?1 (CH2FCF3 reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K1 = (4.71 ± 0.94) × 10?13 exp[?(1630 ± 80)/T] cm3 molecule?1 s?1. Using kinetic data for the reaction of tropospheric CH3CCl3 with OH radicals [k1 (272 K) = 6.0 × 10?15 cm3 molecule?1 s?1, tropospheric lifetime of CH3CCl3 = 6.0 years], we estimated the tropospheric lifetime of CF3CF2CF2CF2CF2CHF2 through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004 相似文献
95.
A homologous series of azomesogens, 2″-[4-(4′-n-alkoxybenzoyloxy)-2-chlorophenylazo] naphthalenes, with lateral chloro groups was synthesised. All the homologues synthesized
exhibit enantiotropic nematic mesophase. The mesomorphic properties of the present series are compared with other structurally
related series to evaluate the effect of lateral chloro group and its position on mesomorphism
This paper was presented at the 10th National Conference on Liquid Crystals held at Bangalore, India during 9–11 October 2003. 相似文献
96.
Andrei K. Lerner 《Archiv der Mathematik》2005,85(6):538-543
We show that the Hardy-Littlewood maximal operator and a class of Calderón-Zygmund singular integrals satisfy the strong type
modular inequality in variable Lp spaces if and only if the variable exponent p(x) ∼ const.
Received: 15 September 2004 相似文献
97.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
98.
H E Cline W E Lorensen R J Herfkens G A Johnson G H Glover 《Magnetic resonance imaging》1989,7(1):45-54
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting. 相似文献
99.
The Iyengar Type Inequalities with Exact Estimations and the Chebyshev Central Algorithms of Integrals 总被引:3,自引:0,他引:3
Xing Hua WANG Shi Jun YANG 《数学学报(英文版)》2005,21(6):1361-1376
In this paper, both low order and high order extensions of the Iyengar type inequality are obtained. Such extensions are the best possible in the same sense as that of the Iyengar inequality. hzrthermore, the Chebyshev central algorithms of integrals for some function classes and some related problems are also considered and investigated. 相似文献
100.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc. 相似文献