全文获取类型
收费全文 | 5790篇 |
免费 | 205篇 |
国内免费 | 20篇 |
专业分类
化学 | 3446篇 |
晶体学 | 20篇 |
力学 | 136篇 |
数学 | 1021篇 |
物理学 | 1392篇 |
出版年
2023年 | 34篇 |
2021年 | 40篇 |
2020年 | 82篇 |
2019年 | 69篇 |
2018年 | 71篇 |
2017年 | 60篇 |
2016年 | 144篇 |
2015年 | 131篇 |
2014年 | 164篇 |
2013年 | 268篇 |
2012年 | 315篇 |
2011年 | 376篇 |
2010年 | 196篇 |
2009年 | 171篇 |
2008年 | 323篇 |
2007年 | 357篇 |
2006年 | 335篇 |
2005年 | 314篇 |
2004年 | 275篇 |
2003年 | 197篇 |
2002年 | 185篇 |
2001年 | 135篇 |
2000年 | 98篇 |
1999年 | 71篇 |
1998年 | 51篇 |
1997年 | 74篇 |
1996年 | 55篇 |
1995年 | 62篇 |
1994年 | 60篇 |
1993年 | 50篇 |
1992年 | 53篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 40篇 |
1987年 | 32篇 |
1986年 | 48篇 |
1985年 | 59篇 |
1984年 | 67篇 |
1983年 | 58篇 |
1982年 | 78篇 |
1981年 | 64篇 |
1980年 | 59篇 |
1979年 | 62篇 |
1978年 | 63篇 |
1977年 | 66篇 |
1976年 | 44篇 |
1975年 | 48篇 |
1974年 | 55篇 |
1973年 | 60篇 |
排序方式: 共有6015条查询结果,搜索用时 15 毫秒
21.
22.
Björn Wängler Carmen Beck Esther Schirrmacher Frank Rösch Michael Eisenhut 《Tetrahedron letters》2006,47(33):5985-5988
The synthesis of tris-allyl-DOTA starting from cyclen and its application in the preparation of DOTA-peptide conjugates is reported. Clinically important conjugates such as DOTA-Tyr3-octreotide (DOTA-TOC), DOTA-Tyr3-octreotate (DOTA-TATE) as well as a DOTA-RGD peptide were synthesized in high yields with Fmoc solid phase peptide synthesis. The final, extremely reliable de-allylation was achieved on solid phase by different methods identifying morpholine/Pd(0) as the most suitable one obtaining all DOTA peptide conjugates in high yields. All DOTA-peptides were purified by reversed phase HPLC and structural identity was proved using MALDI-TOF mass spectrometry. 相似文献
23.
An acoustic pulse propagating on a two-mode fiber can act as a beam splitter in a scanning interferometer. When this device
is employed in white-light interferometry, the effects of distributed coupling and dispersive interferometer arms need to
be considered. A theory suitable for treating acousto-optic interaction of partially coherent light in a moving interaction
region was developed. It was found that differential optical dispersion should be negligible and the acoustic pulse length
short. Also the coherence time should be short but long compared to the intermodal group delay difference over a pulse length.
Experiments with long acoustic pulses were performed, and fairly good agreement with theory was obtained. 相似文献
24.
25.
Steen Mørup 《Hyperfine Interactions》1994,90(1):171-185
Interactions between magnetic nanoparticles can lead to superferromagnetic ordering, i.e. ordering of their magnetic moments at low temperatures. The use of a simple mean field theory, describing the temperature dependence of the order parameter is discussed. This model is found to give excellent fits to experimental results. In systems of particles with pure dipole interactions, the degree of ordering depends critically on the geometrical configuration of the particles. The application of superferromagnetic nanostructures for magnetic refrigeration is also discussed. 相似文献
26.
Martin E. V. Pedersen Lars S. Rishøj Henrik Steffensen Sanshui Xiao Niels Asger Mortensen 《Optical and Quantum Electronics》2007,39(10-11):903-911
Slow-light enhanced optical detection in liquid-infiltrated photonic crystals is theoretically studied. Using a scattering-matrix approach and the Wigner–Smith delay time concept, we show that optical absorbance benefits both from slow-light phenomena as well as a high filling factor of the energy residing in the liquid. Utilizing strongly dispersive photonic crystal structures, we numerically demonstrate how liquid-infiltrated photonic crystals facilitate enhanced light–matter interactions, by potentially up to an order of magnitude. The proposed concept provides strong opportunities for improving existing miniaturized absorbance cells for optical detection in lab-on-a-chip systems. 相似文献
27.
Valery A. Khoze Torbjörn Sjöstrand 《Zeitschrift fur Physik C Particles and Fields》1996,70(4):625-635
The process ${? e}^{+}{? e}^{-}?ghtarrow {? W}^{+}{? W}^{-}?ghtarrow {? f}_{1}{?erline {? f}}_{2}{? f}_{3}{?erline {? f}}_{4}$ contains charges in the initial, intermediate and final stages. This gives a rich selection of possible QED interconnection effects. Coulomb interaction is the simplest of these, and can thus be used to explore consequences. We study a number of experimental observables, with emphasis on those related to the W momentum distribution. Second-order Coulomb effects are shown to be practically negligible. The limited LEP 2 statistics will not allow detailed tests, so any theory uncertainty will be reflected in the systematic error on the W mass. Currently the uncertainty from this source may be as high as 20 MeV. 相似文献
28.
Given a simplicial complex δ on vertices {1, …,n} and a fieldF we consider the subvariety of projective (n−1)-space overF consisting of points whose homogeneous coordinates have support in δ. We give a simple rational expression for the zeta function
of this singular projective variety overF
q and show a close connection with the Betti numbers of the corresponding variety over ℂ. This connection is particularly simple
in the case when Δ is Cohen-Macaulay. 相似文献
29.
Let R be a local ring and let (x
1, …, x
r) be part of a system of parameters of a finitely generated R-module M, where r < dimR
M. We will show that if (y
1, …, y
r) is part of a reducing system of parameters of M with (y
1, …, y
r) M = (x
1, …, x
r) M then (x
1, …, x
r) is already reducing. Moreover, there is such a part of a reducing system of parameters of M iff for all primes P ε Supp M ∩ V
R(x
1, …, x
r) with dimR
R/P = dimR
M − r the localization M
P of M at P is an r-dimensional Cohen-Macaulay module over R
P.
Furthermore, we will show that M is a Cohen-Macaulay module iff y
d is a non zero divisor on M/(y
1, …, y
d−1) M, where (y
1, …, y
d) is a reducing system of parameters of M (d:= dimR
M). 相似文献
30.
We show how the quantization of two-dimensional gravity leads to an (Euclidean) quantum space–time where the average geometry is that of constant negative curvature and where the Hartle–Hawking boundary condition arises naturally. 相似文献