全文获取类型
收费全文 | 3883篇 |
免费 | 192篇 |
国内免费 | 2篇 |
专业分类
化学 | 2358篇 |
晶体学 | 12篇 |
力学 | 81篇 |
综合类 | 1篇 |
数学 | 481篇 |
物理学 | 1144篇 |
出版年
2023年 | 40篇 |
2022年 | 46篇 |
2021年 | 40篇 |
2020年 | 70篇 |
2019年 | 51篇 |
2018年 | 54篇 |
2017年 | 38篇 |
2016年 | 152篇 |
2015年 | 132篇 |
2014年 | 140篇 |
2013年 | 191篇 |
2012年 | 208篇 |
2011年 | 220篇 |
2010年 | 144篇 |
2009年 | 121篇 |
2008年 | 204篇 |
2007年 | 201篇 |
2006年 | 177篇 |
2005年 | 175篇 |
2004年 | 151篇 |
2003年 | 132篇 |
2002年 | 73篇 |
2001年 | 85篇 |
2000年 | 69篇 |
1999年 | 67篇 |
1998年 | 42篇 |
1997年 | 35篇 |
1996年 | 36篇 |
1995年 | 32篇 |
1994年 | 41篇 |
1993年 | 43篇 |
1992年 | 43篇 |
1991年 | 46篇 |
1990年 | 39篇 |
1989年 | 29篇 |
1988年 | 25篇 |
1987年 | 25篇 |
1986年 | 23篇 |
1985年 | 35篇 |
1984年 | 38篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 32篇 |
1980年 | 31篇 |
1979年 | 27篇 |
1978年 | 25篇 |
1977年 | 31篇 |
1976年 | 34篇 |
1975年 | 25篇 |
1973年 | 21篇 |
排序方式: 共有4077条查询结果,搜索用时 15 毫秒
11.
Brandau C. Bartsch T. Böhm S. Böhme C. Hoffknecht A. Kieslich S. Knopp H. Schippers S. Shi W. Müller A. Grün N. Scheid W. Steih T. Bosch F. Franzke B. Kozhuharov C. Krämer A. Mokler P. H. Nolden F. Steck M. Stöhlker T. Stachura Z. 《Hyperfine Interactions》2003,146(1-4):41-45
Hyperfine Interactions - An overview of measurements of dielectronic recombination (DR) with the heaviest lithiumlike ions is presented. The experiments have been carried out at the heavy ion... 相似文献
12.
13.
Jerzy Król 《Foundations of Physics》2006,36(7):1070-1098
We analyse the proposition that the spacetime structure is modified at short distances or at high energies due to weakening of classical logic. The logic assigned to the regions of spacetime is intuitionistic logic of some topoi. Several cases of special topoi are considered. The quantum mechanical effects can be generated by such semi-classical spacetimes. The issues of: background independence and general relativity covariance, field theoretic renormalization of divergent expressions, the existence and definition of path integral measures, are briefly discussed in the proposal. The connection with some problems in foundations of mathematics and differential topology are also discussed. 相似文献
14.
E. Possenriede P. Jacobs H. Kröse O. F. Schirmer 《Applied Physics A: Materials Science & Processing》1992,55(1):73-81
On the basis of a previous identification of paramagnetic defects in nominally undoped as grown BaTiO3 single crystals, we have investigated the changes of the concentrations of these centers and their optical absorptions under illumination with light of varying wavelengths. The most pronounced charge transfers occur by hole ionization of Fe4+ and — to a lesser extent — of Cr5+ and Cr4+. At low temperatures the created holes are trapped in the form of O–-ions next to Al3+ or unknown acceptor defects. Corresponding Fe4+ and O– absorptions have been identified. 相似文献
15.
Solichová D Melichar B Klejna M Jurašková B Královská L Bláha V Zd'ánský P Zadák Z 《Talanta》2003,60(2-3):459-465
Twelve self-sustaining nonagenarians, 10 women and two men, aged 94+/-3 years, and eight institutionalised nonagenarians, eight women, aged 91+/-1 year as well as 11 control subjects, seven women and four men, aged 84+/-5 years entered the study. Urinary neopterin, an indicator of systemic immune activation, and serum thiobarbituric acid reactive substances (TBARS), a marker of lipoperoxidation, were determined initially, and collection of the blood and urine samples was repeated at 3-month interval. Neopterin was measured in the urine specimens by reversed-phase high performance liquid chromatography. A C(18) reversed-phase column 3.3x150 mm, 5 mum-diameter packing Separon SGX was used. Potassium phosphate buffer (15 mmol l(-1), pH 6.4) at flow rate of 0.8 ml min(-1) was used as mobile phase. After centrifugation (5 min, 1300xg) and diluting 100 mul of urine specimens with 1.0 ml of mobile phase containing 2 g of disodium-EDTA per litre, a 20 mul sample was injected on a column. Neopterin was identified by its native fluorescence (353 nm excitation, 438 nm emission). Creatinine was determined by Jaffé kinetic reaction after dilution of sample 1:50 (v/v). The concentration of neopterin in urine was expressed as neopterin/creatinine ratio (mumol mol(-1) creatinine). TBARS were determined spectrofluorometrically using LS-5 spectrofluorimeter (excitation wavelength 528 nm, emission wavelength 558 nm) after extraction with n-butanol treatment with thiobarbituric acid. The significance of differences between nonagenarians and control group was examined by ANOVA-Kruskal-Wallis tests, using statistical software NCSS 6.0.21 (Kaysville, UT, 1996). The decision on significance was based on P=0.05. Urinary neopterin was significantly higher in institutionalised compared to self-sustaining subjects and controls (625+/-565 vs. 203+/-63 mumol mol(-1) creatinine, and 198+/-128 mumol mol(-1) creatinine, respectively, P=0.006). The serum TBARS were higher in both groups of nonagenarians (3.23+/-1.16 mumol l(-1) and 2.69+/-0.39 vs. 2.12+/-0.83 mumol l(-1) for the self-sustaining, institutionalised and controls, respectively, P=0.023). We conclude that the fluorimetric determinations of urinary neopterin and serum TBARS can be useful for the monitoring health status in the elderly patients. 相似文献
16.
A calibration technique for the constant-temperature hot-wire anemometer is presented, which is based on traversing the probe
through the boundary layer of a flat plate while simultaneously performing fluctuation measurements. The free stream Mach
number was M = 2.54, and the Reynolds number Red, based on wire diameter, ranged from 9 to 23. A comparison of the sensitivity values obtained with the aid of such a calibration
procedure — under the condition of neglecting low temperature loadings (t<0.6) — agrees well with sensitivities determined with free-stream data-The use of a modified transfer function for correcting
the power spectra of flow perturbations revealed a conformity of wide parts of the corrected spectra with the Kolmogorov decay.
The fluctuation levels of total temperature and mass flux were computed for the boundary layer of a flat plate.
This work was presented at the International Conference on the Methods of Aerophysical Research ICMAR 2007, which was held
in Novosibirsk on 5–10 February 2007. 相似文献
17.
P. Bonville M. Rams K. Królas J.-P. Sanchez P. C. Canfield O. Trovarelli C. Geibel 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):77-84
We have examined the magnetic properties of the heavy electron compounds
YbAgGe and YbPtIn by 170Yb M?ssbauer spectroscopy down to 0.1 K, and
the crystal field properties of YbAgGe by Perturbed Angular Correlations
(PAC) measurements up to 900 K. In YbAgGe, we show that each of the two
magnetically ordered phases below 0.8 K involves a specific incommensurate
modulation of the Yb moment. An analysis of existing low temperature specific
heat data suggests the
persistence of fluctuations of the correlated Yb spins down to 0.1 K.
The PAC data allow to discriminate among proposed Yb3+ crystal field
level schemes. In YbPtIn, we show that the low temperature magnetic order
phase has an antiferro-para structure, where zero moment Yb ions coexist with
large moment ones, and that a 90° moment reorientation occurs at
1.4 K. 相似文献
18.
19.
Bernhard Krötz 《Japanese Journal of Mathematics》2007,2(2):303-311
In this paper we raise a question about the boundary of the crown domain of a Riemannian symmetric space X. In case X is of Hermitian type we give an affirmative answer. 相似文献
20.
M. Procop A. Klein I. Rechenberg D. Krüger 《Analytical and bioanalytical chemistry》1997,358(1-2):358-360
An ion beam technique has been developed which allows the preparation of bevels from semiconducting heteroepitaxial structures
with smooth surfaces and very flat angles in the order of 0.1°. The bevels are used for AES depth profiling of heterostructures
by the line scan technique. Measured and calculated line scans from (Al,Ga)As/GaAs and SiGe/Si test structures are compared
to estimate the contributions of the electron escape depth and the ion beam mixing to the depth resolution.
Received: 21 August 1996 / Revised: 14 January 1997 / Accepted: 18 January 1997 相似文献