全文获取类型
收费全文 | 771篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
化学 | 341篇 |
晶体学 | 27篇 |
力学 | 17篇 |
数学 | 206篇 |
物理学 | 208篇 |
出版年
2023年 | 4篇 |
2022年 | 28篇 |
2021年 | 34篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 4篇 |
2016年 | 22篇 |
2015年 | 19篇 |
2014年 | 22篇 |
2013年 | 33篇 |
2012年 | 34篇 |
2011年 | 26篇 |
2010年 | 30篇 |
2009年 | 33篇 |
2008年 | 39篇 |
2007年 | 38篇 |
2006年 | 29篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 20篇 |
2001年 | 13篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1937年 | 3篇 |
1873年 | 6篇 |
排序方式: 共有799条查询结果,搜索用时 0 毫秒
741.
C. M. Kinart K. Nowak A. Ćwiklińska W. J. Kinart A. Bald 《Journal of Thermal Analysis and Calorimetry》2005,79(1):79-84
Relative permittivities () and densities () of numerous binary mixtures of dipropylene glycol monomethyl ether (1)+propylene glycol mono n-butyl ether (2) and dipropylene glycol monomethyl ether (1)+dipropylene glycol mono n-butyl ether (2) at five temperatures, between (293.15 and 313.15) K, are reported. The excess molar volumes (V
E) and the relative permittivity deviations () were calculated from these experimental data. The results are discussed in terms of intermolecular interactions in the bulk of studied the binary mixtures. 相似文献
742.
K.M. Nowak H.J. Baker D.R. Hall 《Applied Physics A: Materials Science & Processing》2006,84(3):267-270
We report a novel “cold” self-cleaning technique for processing low temperature co-fired ceramic (LTCC) in the “green” state at high resolution and high speed, using a low power carbon dioxide laser. A particle ejection process involving both the ceramic grains and the organic binder produces material removal rates of >100 μm per pulse with lateral processing resolution of 50 μm and depth resolution comparable to ceramic grain size with no heat-effected zone or other deleterious thermal effects. The process has been used to drill microvias and to machine arbitrary shapes with high resolution. PACS 79.20.Ds; 42.62.Cf; 42.55.Lt; 81.20.Wk 相似文献
743.
The dielectric polarization and its change in an external electric field were measured for dioxane—water diluted solutions up to 0.3 molar fraction of water. The results were found to be qualitatively similar to those previously observed for dioxane—alcohols mixtures. 相似文献
744.
Laser-induced wet chemical etching of stainless steel 304 and Ti in phosphoric acid, sulfuric acid and aqueous KOH has been investigated using cw Ar and cw Nd : YAG lasers. Two different phases of laser-induced etching of Ti in phosphoric acid were found by electrochemical investigations. Laser-enhanced electrochemical dissolution of stainless steel was observed in the passivation and transpas sivation region. In the latter case, laser heating accelerates the metal dissolution. In the passivation region, laser heating results in a breakthrough of the passivation layer near the Flade potential. By multiple scanning microstructures of high quality and an aspect ratio > 10 have been produced. By EDX analysis the laser-etching process was found to be practically free of chemical residues on etched surfaces. 相似文献
745.
A. Rogalski J. Rutkowski K. Jóźwikowski J. Piotrowski Z. Nowak 《Applied Physics A: Materials Science & Processing》1990,50(4):379-384
This paper considers the Hg1–x
Zn
x
Te alloy system as a potential material for the fabrication of infrared photodiodes. The influence of different junction current components (diffusion, tunneling and depletion layer currents) on the R
0
A product of n+-pHg1–x
Zn
x
Te photodiodes is analysed. The upper theoretical limits of the R
0
A product and detectivity are determined. Results of calculations are compared with experimental data reported by other authors and those measured in our laboratory. Preliminary results on related technology and the properties of Hg1–x
Zn
x
Te prepared by the ion-etching technique are presented. 相似文献
746.
Generation of difluoromethylene phosphorus ylides in the presence of aldehydes and ketones results in Wittig-type reactions to give gem-difluoroalkenes. Subsequent in situ addition of difluorocarbene (carbenoid) can occur (increased with triphenylphosphine and decreased with tributylphosphine) to give tetrafluorocyclopropanes. [Reaction: see text] 相似文献
747.
[reaction: see text] Generation of difluorocarbene(carbenoid) in the presence of enamines derived from cyclic ketones results in overall insertion of CF2 to produce bicyclic difluorocyclopropylamines. These adducts are very weakly basic, and their thermal stabilities vary markedly with their structures. 相似文献
748.
High-resolution solid-state 119Sn and 195Pt NMR studies of MPtSn semiconductors (M = Ti, Zr, Hf, Th)
Solid-state 119Sn and 195Pt magic-angle spinning (MAS) NMR spectra are reported on a series of MPtSn compounds (M = Ti, Zr, Hf, Th). In favorable cases (TiPtSn and ZrPtSn) the spectra reveal expected J-coupling patterns originating from indirect spin coupling between Pt and Sn nuclei. MAS has no effect on the broad and asymmetric spectra of either 119Sn and 195Pt nuclei in HfPtSn. 相似文献
749.
Michaelsen C Wiesmann J Bormann R Nowak C Dieker C Hollensteiner S Jäger W 《Optics letters》2001,26(11):792-794
La/B(4)C multilayers have been fabricated by magnetron sputtering for use as x-ray mirrors at energies below 190 eV, particularly for detection of boron K and alpha x rays at 183 eV, their performance has been compared with that of Mo/B(4)C multilayers, which are currently the best-performing multilayers for this energy range. Transmission electron microscopy and synchrotron soft-x-ray reflectometry were used to study the structural quality of the multilayers and their performance as x-ray mirrors. The results show a significant improvement of the peak reflectivity and the spectral purity, indicating that La/B(4)C has a high potential to replace Mo/B(4)C in many x-ray optical applications below 190 eV. 相似文献
750.
W. G. Nowak 《Archiv der Mathematik》2002,78(3):241-248
For a convex planar domain D \cal {D} , with smooth boundary of finite nonzero curvature, we consider the number of lattice points in the linearly dilated domain t D t \cal {D} . In particular the lattice point discrepancy PD(t) P_{\cal {D}}(t) (number of lattice points minus area), is investigated in mean-square over short intervals. We establish an asymptotic formula for¶¶ òT - LT + L(PD(t))2dt \int\limits_{T - \Lambda}^{T + \Lambda}(P_{\cal {D}}(t))^2\textrm{d}t ,¶¶ for any L = L(T) \Lambda = \Lambda(T) growing faster than logT. 相似文献