全文获取类型
收费全文 | 49332篇 |
免费 | 1671篇 |
国内免费 | 26篇 |
专业分类
化学 | 31733篇 |
晶体学 | 233篇 |
力学 | 1576篇 |
数学 | 7556篇 |
物理学 | 9931篇 |
出版年
2023年 | 376篇 |
2022年 | 307篇 |
2021年 | 503篇 |
2020年 | 680篇 |
2019年 | 648篇 |
2018年 | 1004篇 |
2017年 | 818篇 |
2016年 | 1533篇 |
2015年 | 1410篇 |
2014年 | 1410篇 |
2013年 | 2903篇 |
2012年 | 3414篇 |
2011年 | 3493篇 |
2010年 | 2087篇 |
2009年 | 1709篇 |
2008年 | 2984篇 |
2007年 | 2993篇 |
2006年 | 2636篇 |
2005年 | 2549篇 |
2004年 | 2198篇 |
2003年 | 1771篇 |
2002年 | 1543篇 |
2001年 | 912篇 |
2000年 | 766篇 |
1999年 | 542篇 |
1998年 | 406篇 |
1997年 | 368篇 |
1996年 | 466篇 |
1995年 | 297篇 |
1994年 | 349篇 |
1993年 | 353篇 |
1992年 | 377篇 |
1991年 | 327篇 |
1990年 | 312篇 |
1989年 | 307篇 |
1988年 | 248篇 |
1987年 | 250篇 |
1986年 | 220篇 |
1985年 | 380篇 |
1984年 | 351篇 |
1983年 | 238篇 |
1982年 | 326篇 |
1981年 | 319篇 |
1980年 | 275篇 |
1979年 | 270篇 |
1978年 | 251篇 |
1976年 | 265篇 |
1975年 | 242篇 |
1974年 | 249篇 |
1973年 | 241篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
E. Liénard G. Ban C. Couratin P. Delahaye D. Durand X. Fabian B. Fabre X. Fléchard P. Finlay F. Mauger A. Méry O. Naviliat-Cuncic B. Pons T. Porobic G. Quéméner N. Severijns J. C. Thomas Ph. Velten 《Hyperfine Interactions》2015,234(1-3):1-7
The experimental achievements and the results obtained so far with the LPCTrap device installed at GANIL are presented. The apparatus is dedicated to the study of the weak interaction at low energy by means of precise measurements of the β ? ν angular correlation parameter in nuclear β decays. So far, the data collected with three isotopes have enabled to determine, for the first time, the charge state distributions of the recoiling ions, induced by shakeoff process. The analysis is presently refined to deduce the correlation parameters, with the potential of improving both the constraint deduced at low energy on exotic tensor currents (6He1+) and the precision on the V u d element of the quark-mixing matrix (35Ar1+ and 19Ne1+) deduced from the mirror transitions dataset. 相似文献
953.
In this paper we give the precise index growth for the embedded hypersurfaces of revolution with constant mean curvature
(cmc) 1 in (Delaunay unduloids). When n=3, using the asymptotics result of Korevaar, Kusner and Solomon, we derive an explicit asymptotic index growth rate for finite
topology cmc 1 surfaces with properly embedded ends. Similar results are obtained for hypersurfaces with cmc bigger than 1
in hyperbolic space.
Received: 6 July 2000; in final form: 10 September 2000 / Published online: 25 June 2001 相似文献
954.
Wen Wang Yuqing Qiao Li He Ludovic Dumée Lingxue Kong Minshou Zhao Weimin Gao 《Ionics》2015,21(8):2119-2125
LiFe1???x Sm x PO4/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp2-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO4 Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively. 相似文献
955.
Let D
N
, G
M
be two open sets, E D and F G two compact sets which satisfy the condition (H) (that is a harmonic condition similar to Leja"s condition). We find an open set
N+M
such that each separately harmonic function f : X : = (D× F) (E × G) (i.e.: for all x in E, f(x,.) is harmonic on G; for all y in F, f(., y) is harmonic on D) extends to a harmonic function on . 相似文献
956.
Lucas C. Céleri Rafael M. Gomes Radu Ionicioiu Thomas Jennewein Robert B. Mann Daniel R. Terno 《Foundations of Physics》2014,44(5):576-587
We describe a new class of experiments designed to probe the foundations of quantum mechanics. Using quantum controlling devices, we show how to attain a freedom in temporal ordering of the control and detection of various phenomena. We consider wave–particle duality in the context of quantum-controlled and the entanglement-assisted delayed-choice experiments. Then we discuss a quantum-controlled CHSH experiment and measurement of photon’s transversal position and momentum in a single set-up. 相似文献
957.
Classical invariants of General Relativity can be used to approximate the entropy of the gravitational field. In this work, we study two proposed estimators based on scalars constructed out from the Weyl tensor, in Kerr spacetime. In order to evaluate Clifton, Ellis and Tavakol’s proposal, we calculate the gravitational energy density, gravitational temperature, and gravitational entropy of the Kerr spacetime. We find that in the frame we consider, Clifton et al.’s estimator does not reproduce the Bekenstein–Hawking entropy of a Kerr black hole. The results are compared with previous estimates obtained by the authors using the Rudjord–Gr \(\varnothing \) n–Hervik approach. We conclude that the latter represents better the expected behaviour of the gravitational entropy of black holes. 相似文献
958.
Summary In this note we present new properties of cliques induced constraints straintsX(C
r
+
)-X(C
r
-
) ≤ 1 - |C
r
-
| for λ εS, whereS is the set of cliques that are implied by 0–1 mixed integer programs. These properties allow to further fixing of 0–1 variables,
to detect instance's infeasibility and to imply new cliques. 相似文献
959.
Christian Brackmann Odd Hole Bo Zhou Zhongshan S. Li Marcus Aldén 《Applied physics. B, Lasers and optics》2014,115(1):25-33
Two-photon laser-induced fluorescence (LIF) of ammonia (NH3) with excitation of the C′-X transition at 304.8 nm and fluorescence detection in the 565 nm C′-A band has been investigated, targeting combustion diagnostics. The impact of laser irradiance, temperature, and pressure has been studied, and simulation of NH3-spectra, fitted to experimental data, facilitated interpretation of the results. The LIF-signal showed quadratic dependence on laser irradiance up to 2 GW/cm2. Stimulated emission, resulting in loss of excited molecules, is induced above 10 GW/cm2, i.e., above irradiances attainable for LIF imaging. Maximum LIF-signal was obtained for excitation at the 304.8 nm bandhead; however, lower temperature sensitivity over the range 400–700 K can be obtained probing lines around 304.9 nm. A decrease in fluorescence signal was observed with pressure up to 5 bar absolute and attributed to collisional quenching. A detection limit of 800 ppm, at signal-to-noise ratio 1.5, was identified for single-shot LIF imaging over an area of centimeter scale, whereas for single-point measurements, the technique shows potential for sub-ppm detection. Moreover, high-quality NH3-imaging has been achieved in laminar and turbulent premixed flames. Altogether, two-photon fluorescence provides a useful tool for imaging NH3-detection in combustion diagnostics. 相似文献
960.
J. A. Jiménez 《Applied Physics A: Materials Science & Processing》2014,114(4):1369-1376
Prospective applications of plasmonic nanocomposites in photonic and optoelectronic devices demand innovative means of material syntheses, as well as a comprehensive understanding of the influence of material composition and processing on resulting properties. In this work, it is shown that a phosphate glass matrix prepared with stoichiometric amounts of CuO and SnO dopants by the melting technique may well be effective for the precipitation of Cu nanoparticles (NPs) upon heat treatment (HT). Optical absorption and photoluminescence (PL) spectroscopy, including emission decay dynamics, are employed in the characterization of the melt-quenched glass, and for investigating the influence of HT on material optical properties. The as-prepared material appeared highly luminescent; the data suggests contributions from both twofold-coordinated tin centers and Cu+ ions to light emission. The PL depends strongly on excitation wavelength; e.g. excitation at 260 nm shows a blue–white emission for which a significant contribution from tin is indicated, whereas excitation at 360 nm produces an orange emission in association with Cu+ ions. Thermal processing results in the chemical reduction of ionic copper via Sn2+ ultimately producing Cu NPs in the matrix, as evidenced by the appearance of the surface plasmon resonance around 574 nm. As a result, Cu+ PL decreases and the emission band shows a dip due to reabsorption by Cu NPs in resonance. 相似文献