全文获取类型
收费全文 | 1882篇 |
免费 | 24篇 |
国内免费 | 8篇 |
专业分类
化学 | 1021篇 |
晶体学 | 16篇 |
力学 | 65篇 |
数学 | 253篇 |
物理学 | 559篇 |
出版年
2018年 | 18篇 |
2016年 | 20篇 |
2015年 | 23篇 |
2014年 | 22篇 |
2013年 | 70篇 |
2012年 | 53篇 |
2011年 | 46篇 |
2010年 | 31篇 |
2009年 | 35篇 |
2008年 | 36篇 |
2007年 | 54篇 |
2006年 | 53篇 |
2005年 | 64篇 |
2004年 | 44篇 |
2003年 | 37篇 |
2002年 | 39篇 |
2001年 | 48篇 |
2000年 | 49篇 |
1999年 | 43篇 |
1998年 | 34篇 |
1997年 | 33篇 |
1996年 | 24篇 |
1995年 | 34篇 |
1994年 | 37篇 |
1993年 | 28篇 |
1992年 | 25篇 |
1991年 | 33篇 |
1990年 | 23篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 30篇 |
1986年 | 29篇 |
1985年 | 30篇 |
1984年 | 35篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1980年 | 18篇 |
1979年 | 30篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1975年 | 28篇 |
1974年 | 19篇 |
1973年 | 24篇 |
1972年 | 22篇 |
1970年 | 21篇 |
1968年 | 31篇 |
1967年 | 56篇 |
1966年 | 61篇 |
1965年 | 19篇 |
排序方式: 共有1914条查询结果,搜索用时 15 毫秒
71.
The influence of impurity scattering is studied theoretically in a two-layer model for the high-T
c
superconductor Y1Ba2Cu3O7– with intra- and inter-layer pairing. Two types of impurities are considered: (I) impurities which conserve the reflection symmetry of the two layers and (II) impurities which break it. Impurities of type (I) have no influence on the critical temperature. Type (II) impurities have strong influence onT
c
as well as onH
c2
if there is a pairing interaction between carriers of different layers. The treatment of type (II) impurities is generalized to a periodic layer model appropriate for La2–x
Ba
x
CuO4. Available experiments on impurities in Y1Ba2Cu3O7– and La2–x
Ba
x
CuO4 are interpreted with our theory. 相似文献
72.
We report the observation of Absorption Line Narrowing (A.L.N.) in a Doppler-broadened three-level system of neon under interaction with two quasi-resonant single-mode lasers. The resonance signals are obtained with the laser beams propagating either in the same direction or in opposite direction. The resonance width is found to be smaller in the latter case. The isotopic shifts 22Ne-20Ne of the lines λ = 1.15μ, λ = 6096 Å and λ = 5945 Å have been measured using the A.L.N. method. 相似文献
73.
A fundamental attribute of raft formation in cell membranes is lateral separation of lipids into coexisting liquid phases. Using fluorescence microscopy, we observe spontaneous lateral separation in free-floating giant unilamellar vesicles. We record coexisting liquid domains over a range of composition and temperature significantly wider than previously reported. Furthermore, we establish correlations between miscibility in bilayers and in monolayers. For example, the same lipid mixtures that produce liquid domains in bilayer membranes produce two upper miscibility critical points in the phase diagrams of monolayers. 相似文献
74.
Douglas L. Costa Gordon E. Keller 《Transactions of the American Mathematical Society》1999,351(12):5051-5088
We give a characterization theorem for the -normalized subgroups of , where is any commutative ring. This is the last of the simple Chevalley-Demazure group-schemes for which such a theorem is lacking.
75.
M.-E. Herrmann H. Brösicke M. Keller E. Mönch H. Helge 《Isotopes in environmental and health studies》2013,49(1):34-35
It is essential to establish whether and how environmental factors affect the reliability of [13C]methacetin breath test (13C-MBT). In 12 healthy volunteers (smokers), a standard 13C-MBT with 75 mg [13C]methacetin was performed twice in random order: on a control day without smoking and on another day with smoking two cigarettes antecedently. A considerable flattening of the curve of the momentary 13C recovery within the expiratory air was observed when the 13C-MBT was performed after smoking. The maximum of the momentary 13C recovery, D max, decreased from 37.20±2.58 to 25.39±2.29% dose/h (p=0.00052). Moreover, the time to reach D max was prolonged after cigarette smoking (26.5±3.1 vs. 16.5±1.9 min, p=0.0199). The curve of the cumulative 13C recovery on the cigarette smoking day appeared to be shifted downwards, and statistically significant differences relative to the control situation were found between the 24th and 75th minute following [13C]methacetin administration. Smoking cigarettes immediately prior to the 13C-MBT diminishes the ability of the liver to handle methacetin, and hence a possibility of such an interaction should be excluded in order to interpret the results of the test correctly. 相似文献
76.
Gerhard Keller 《Israel Journal of Mathematics》1994,86(1-3):301-310
We prove exponential weak Bernoulli mixing for invariant measures of certain piecewise monotone interval maps studied in [BK]
and [KN]. In particular we prove this for unimodal maps with negative Schwarzian derivative satisfying lim
, wherec is the unique critical point ofT. 相似文献
77.
In this note, we prove a duality theorem for the Tate–Shafarevich group of a finite discrete Galois module over the function field K of a curve over an algebraically closed field: there is a perfect duality of finite groups Open image in new window for F a finite étale Galois module on K of order invertible in K and with \(F' = {{\mathrm{Hom}}}(F,\mathbf{Q}/\mathbf {Z}(1))\). Furthermore, we prove that \(\mathrm {H}^1(K,G) = 0\) for G a simply connected, quasisplit semisimple group over K not of type \(E_8\). 相似文献
78.
Let HD d (p, q) denote the minimal size of a transversal that can always be guaranteed for a family of compact convex sets in Rd which satisfy the (p, q)-property (p ≥ q ≥ d + 1). In a celebrated proof of the Hadwiger–Debrunner conjecture, Alon and Kleitman proved that HD d (p, q) exists for all p ≥ q ≥ d + 1. Specifically, they prove that \(H{D_d}(p,d + 1)is\tilde O({p^{{d^2} + d}})\).We present several improved bounds: (i) For any \(q \geqslant d + 1,H{D_d}(p,d) = \tilde O({p^{d(\frac{{q - 1}}{{q - d}})}})\). (ii) For q ≥ log p, \(H{D_d}(p,q) = \tilde O(p + {(p/q)^d})\). (iii) For every ? > 0 there exists a p0 = p0(?) such that for every p ≥ p0 and for every \(q \geqslant {p^{\frac{{d - 1}}{d} + \in }}\) we have p ? q + 1 ≤ HD d (p, q) ≤ p ? q + 2. The latter is the first near tight estimate of HD d (p, q) for an extended range of values of (p, q) since the 1957 Hadwiger–Debrunner theorem.We also prove a (p, 2)-theorem for families in R2 with union complexity below a specific quadratic bound. 相似文献
79.
J. Tripathi J.M. Keller K. Das S. Tripathi T. Shripathi 《Journal of Physics and Chemistry of Solids》2012,73(8):1026-1033
Contribution of Rhodamine B doping on the structural and optical properties of PVA is investigated here. With increasing doping wt%, Raman spectra show the disappearance of main PVA peaks revealing a decrease in crystallinity and breaking of bonds, which also results in modified surface morphology as seen from corresponding SEM measurements. Optical absorption measurements show the possibility of both direct and indirect transitions, also indicating strong modifications in optical properties as a result of doping fluorescent dye in the polymer host. 相似文献
80.
G. J. Spühler K. J. Weingarten R. Grange L. Krainer M. Haiml V. Liverini M. Golling S. Schön U. Keller 《Applied physics. B, Lasers and optics》2005,81(1):27-32
We present two novel semiconductor saturable absorber mirror (SESAM) designs which can exhibit more than ten times lower saturation
fluence than classical SESAM devices. Design considerations and characterization data are presented. These devices are particularly
suited for passively mode-locked lasers with ultra-high repetition rates. 相似文献