全文获取类型
收费全文 | 412347篇 |
免费 | 4909篇 |
国内免费 | 1301篇 |
专业分类
化学 | 227152篇 |
晶体学 | 6335篇 |
力学 | 16336篇 |
综合类 | 13篇 |
数学 | 45955篇 |
物理学 | 122766篇 |
出版年
2019年 | 3570篇 |
2018年 | 4757篇 |
2017年 | 4620篇 |
2016年 | 7158篇 |
2015年 | 4562篇 |
2014年 | 6699篇 |
2013年 | 17737篇 |
2012年 | 12968篇 |
2011年 | 15766篇 |
2010年 | 11025篇 |
2009年 | 10676篇 |
2008年 | 14728篇 |
2007年 | 14804篇 |
2006年 | 13930篇 |
2005年 | 12564篇 |
2004年 | 11339篇 |
2003年 | 10221篇 |
2002年 | 9851篇 |
2001年 | 11358篇 |
2000年 | 8898篇 |
1999年 | 6807篇 |
1998年 | 5638篇 |
1997年 | 5706篇 |
1996年 | 5547篇 |
1995年 | 4827篇 |
1994年 | 4879篇 |
1993年 | 4794篇 |
1992年 | 5401篇 |
1991年 | 5206篇 |
1990年 | 5038篇 |
1989年 | 5102篇 |
1988年 | 4915篇 |
1987年 | 4915篇 |
1986年 | 4644篇 |
1985年 | 6251篇 |
1984年 | 6325篇 |
1983年 | 5199篇 |
1982年 | 5613篇 |
1981年 | 5431篇 |
1980年 | 5161篇 |
1979年 | 5533篇 |
1978年 | 5816篇 |
1977年 | 5712篇 |
1976年 | 5544篇 |
1975年 | 5252篇 |
1974年 | 5198篇 |
1973年 | 5287篇 |
1972年 | 3534篇 |
1968年 | 3461篇 |
1967年 | 3926篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
971.
I. A. Anoshko V. S. Ermachenko L. E. Sandrigailo 《Journal of Applied Spectroscopy》2007,74(1):102-106
We present the results of a spectroscopic study of a nonequilibrium plasma in a Hall accelerator, in particular for such an
important parameter as the electron temperature. For the studied conditions, we used the semicoronal equilibrium model, which
relates the intensity ratios for two successive ionization steps for the same element.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 93–96, January–February, 2007. 相似文献
972.
973.
The phase transitions and phase state of hydroxypropylcellulose mixtures with ethanol and acetic acid under static conditions and in the shear field have been studied by the turbidity-point method and polarization microscopy with the use of a polarization-photoelectric setup and a modified plastoviscometer. The deformation of solutions leads to a decrease in the temperature of mesomorphic phase formation and to a change in the type of liquid crystals from cholesteric to nematic. 相似文献
974.
Bahattin Gümgüm Nermin Biricik Feyyaz Durap Ismail Özdemir Nevin Gürbüz Wee Han Ang Paul J. Dyson 《应用有机金属化学》2007,21(8):711-715
Palladium(II) complexes with N,N‐bis(diphenylphosphino)aniline ligands catalyse the Heck reaction between styrene and aryl bromides, affording stilbenes in good yield. The structures of two of the complexes used as pre‐catalysts have been determined by single‐crystal X‐ray diffraction. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
975.
Vlasov Yu. G. Murzina Yu. G. Legin A. V. Ermolenko Yu. E. Schubert J. Schüoning M. J. Lut H. 《Russian Journal of Applied Chemistry》2002,75(3):351-356
Methods of silicon planar technology and pulsed laser deposition were applied to fabricate fully solid-state chemical sensors for determining ions of copper, lead, cadmium, thallium, and also sulfide and chloride ions on the basis of thin chalcogenide films as ion-sensitive membranes. 相似文献
976.
N. H. Abu-Hamdeh 《Heat and Mass Transfer》2002,38(7-8):687-693
The analytical solutions of equations describing the dynamics of distributed parameter systems are usually complicated in
form and derivations and inconvenient to use for simulation and control system design. The liquid–liquid counter flow heat
exchanger is an example of these disturbed parameter systems. An analytical solution of the dynamics of a symmetrically operated
counter flow heat exchanger in the form of transfer function matrix is investigated in open-loop and close-loop conditions.
The resulting non-linear model was linearized using perturbation approach. A feed-forward path controller to counteract at
any disturbances in the boundary temperature and a non-interactive controller to decouple the outputs were implemented.
Received on 22 February 2001 / Published online: 29 November 2001 相似文献
977.
E. V. Ermanyuk 《Experiments in fluids》2002,32(2):242-251
This paper presents a study on affine similitude for the force coefficients of an arbitrary body oscillating in a uniformly
stratified fluid. A simple formula is derived that gives a relation between the force coefficients for a body oscillating
in homogeneous and uniformly stratified ideal fluids. In particular, it implies the existence of a universal nondimensional
similitude criterion for a family of affinely similar bodies, namely, the bodies that can be transformed into each other by
vertical dilation of the initial coordinate system. Theoretical results are verified by experiments with a set of spheroids
having different length-to-diameter ratios. The experimental technique for evaluation of the frequency-dependent force coefficients
is based on Fourier analysis of the time-history of damped oscillation tests.
Received: 25 September 2000 / Accepted: 6 July 2001 Published online: 29 November 2001 相似文献
978.
979.
T Yamakawa H Matsukura Y Nomura M Yoshioka M Masaki H Igata S Okabe 《Chemical & pharmaceutical bulletin》1991,39(7):1746-1752
A series of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines (3) was synthesized and evaluated for its biological activity against gastric H+/K(+)-ATPase prepared from rabbit stomach and gastric acid secretions in Heidenhain pouch dogs. Monoalkyl substituents on the nitrogen atom of the aniline moiety markedly inhibited the enzyme activity to the same degree as omeprazole, a representative H+/K(+)-ATPase inhibitor. Most of these compounds, administered at 3 mg/kg i.v. inhibited histamine-stimulated gastric acid secretion. The inhibitory activity of these derivatives on the enzymes at pH 6.0 was more potent than that at pH 7.4, and was distinctly correlated to stability in aqueous solution at pH 5.0. 相似文献
980.
Pál Sohár Gábor Bernáth Géza Stájer Angela E. Szabo 《Magnetic resonance in chemistry : MRC》1989,27(9):872-876
Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments. 相似文献