全文获取类型
收费全文 | 261136篇 |
免费 | 2561篇 |
国内免费 | 812篇 |
专业分类
化学 | 141906篇 |
晶体学 | 3878篇 |
力学 | 11099篇 |
综合类 | 12篇 |
数学 | 26700篇 |
物理学 | 80914篇 |
出版年
2018年 | 2033篇 |
2017年 | 1946篇 |
2016年 | 3596篇 |
2015年 | 2420篇 |
2014年 | 3583篇 |
2013年 | 10612篇 |
2012年 | 7846篇 |
2011年 | 10039篇 |
2010年 | 6669篇 |
2009年 | 6483篇 |
2008年 | 9092篇 |
2007年 | 9199篇 |
2006年 | 8894篇 |
2005年 | 8398篇 |
2004年 | 7402篇 |
2003年 | 6618篇 |
2002年 | 6553篇 |
2001年 | 7326篇 |
2000年 | 5614篇 |
1999年 | 4508篇 |
1998年 | 3927篇 |
1997年 | 3822篇 |
1996年 | 3585篇 |
1995年 | 3461篇 |
1994年 | 3257篇 |
1993年 | 3086篇 |
1992年 | 3552篇 |
1991年 | 3608篇 |
1990年 | 3363篇 |
1989年 | 3368篇 |
1988年 | 3318篇 |
1987年 | 3226篇 |
1986年 | 3075篇 |
1985年 | 4095篇 |
1984年 | 4304篇 |
1983年 | 3557篇 |
1982年 | 4005篇 |
1981年 | 3728篇 |
1980年 | 3730篇 |
1979年 | 3840篇 |
1978年 | 4095篇 |
1977年 | 3914篇 |
1976年 | 3979篇 |
1975年 | 3812篇 |
1974年 | 3737篇 |
1973年 | 3944篇 |
1972年 | 2489篇 |
1971年 | 2065篇 |
1968年 | 2030篇 |
1967年 | 2087篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
101.
We have investigated the low-lying collective states and electromagnetic transitions in 94Mo within the framework of the interacting boson model. The influence of model parameters on the energy levels and electromagnetic properties has been investigated. The analysis of the obtained results and the parameter values predict that the 23+state is the lowest mixed symmetry state with pure F = Fmax - 1 in this nucleus. The calculated results predicate that the 25+ (two-Q-phonon) mixed symmetry state is closed to the J = 2+ at 2.870 MeV in the experimental data, and the 2.965 MeV state is the lowest mixed symmetry with J = 3+. 相似文献
102.
This paper presents the development and laboratory evaluation of a PM10/2.5/1.0 trichotomous sampling inlet that consists of two main parts: a previously designed PM10 size‐selective inlet part and a PM2.5/1.0 two‐stage virtual impactor, which was newly fabricated and attached serially to the PM10 size selective inlet part. Particles are collected in three locations through the trichotomous sampling inlet to provide for not only particle concentration measurements of PM10, PM2.5 and PM1.0, but also those of PM2.5–10 and PM1.0–2.5. 相似文献
103.
104.
The low-temperature reaction of magnesium with fluorobenzene has been investigated. Joint condensation of magnesium and fluorobenzene vapours at low temperatures quantitatively gave phenylmagnesium fluoride in one stage. 相似文献
105.
106.
A. A. Berezhnoy F. L. Vladimirov I. Yu. Grodetskii Yu. L. Korzinin V. I. Sukhanov 《Optics and Spectroscopy》2002,93(5):777-780
The possibility of usage of the spontaneous electrooptical (EO) effect in strontium barium niobate (SBN) crystals for the creation of controlled electroholographic elements is studied. It is found that unipolar EO properties of these crystals with respect to switching their spontaneous polarization make it possible to devise field-controlled holographic elements with reversible energy-independent memory for spatial position of an optical beam. 相似文献
107.
108.
L. Pillier C. Moreau X. Mercier J.F. Pauwels P. Desgroux 《Applied physics. B, Lasers and optics》2002,74(4-5):427-434
Cavity ring-down spectroscopy (CRDS) is used to measure the NO mole fraction formed in the burnt gases of low-pressure premixed
flames. It is shown that the line-of-sight absorption is greatly increased by the contribution of the NO molecules surrounding
the burner. This contribution has been quantified by developing a mathematical procedure taking into account the spatial and
spectral features of the CRDS measurement. Calculations have been undertaken in the general case of a stable species not consumed
in the flame. The most sensitive parameter is the temperature both in the flame and outside the flame. Simulations allow the
selection of the best spectroscopic transitions for a given flame (i.e. a given temperature profile), ensuring the weakest
influence of the inaccuracy affecting the temperature determination. High quantum states belonging to the A–X (0–1) band of
NO have been found to be the most valuable and have led to a NO mole fraction determination with an accuracy of ±13%. NO absorption
in the flame was completely masked using the A–X (0–0) band. Finally, the prompt-NO mole fraction formed in a methane/air
flame stabilized at 33 Torr is obtained by combining CRDS and laser induced fluorescence techniques.
Received: 12 October / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
109.
The liquid chromatographic analysis of drugs in urine through direct injection without any sample pretreatment was extended to micellar chromatography with nonionic surfactants, the Pinkerton ISRP column and the shielded hydrophobic phase (Hisep) column. The feasibility of using each was demonstrated through the determination of the diuretic, hydrochlorothiazide, in urine. Good separation, recovery, precision and linearity, and adequate limits of detection were obtained for this analysis with all three techniques. The advantages and limitations of the mobile phase approach of micellar chromatography and the two stationary phase approaches are discussed for the direct injection of urine as well as other biological fluids. 相似文献
110.
V. Vittoria R. Russo F. De Candia P. L. Magagnini B. Bresci 《Journal of Polymer Science.Polymer Physics》1991,29(9):1163-1168
The transport properties of a side-chain liquid-crystalline polymer forming a smectic A phase have been investigated using dichloromethane as a permeant. Samples differing in the isotropization enthaoly were analyzed. A. Correlation between this thermal parameter and sorption has been found, while the diffusion coefficient is substantially the same in all samples. The results obtained can be explained in terms of a biphasis model in which a disordered permeable phase is present within the liquid-crystalline phase, which is impermeable to the diffusant molecules. 相似文献