全文获取类型
收费全文 | 42713篇 |
免费 | 1553篇 |
国内免费 | 196篇 |
专业分类
化学 | 22781篇 |
晶体学 | 228篇 |
力学 | 1226篇 |
综合类 | 21篇 |
数学 | 7249篇 |
物理学 | 12957篇 |
出版年
2022年 | 273篇 |
2021年 | 431篇 |
2020年 | 586篇 |
2019年 | 468篇 |
2018年 | 638篇 |
2017年 | 613篇 |
2016年 | 1240篇 |
2015年 | 952篇 |
2014年 | 1115篇 |
2013年 | 2293篇 |
2012年 | 1979篇 |
2011年 | 2134篇 |
2010年 | 1490篇 |
2009年 | 1218篇 |
2008年 | 1984篇 |
2007年 | 1854篇 |
2006年 | 1732篇 |
2005年 | 1549篇 |
2004年 | 1327篇 |
2003年 | 1079篇 |
2002年 | 1007篇 |
2001年 | 913篇 |
2000年 | 745篇 |
1999年 | 532篇 |
1998年 | 473篇 |
1997年 | 452篇 |
1996年 | 554篇 |
1995年 | 475篇 |
1994年 | 510篇 |
1993年 | 520篇 |
1992年 | 565篇 |
1991年 | 399篇 |
1990年 | 410篇 |
1989年 | 368篇 |
1988年 | 340篇 |
1987年 | 344篇 |
1986年 | 322篇 |
1985年 | 517篇 |
1984年 | 499篇 |
1983年 | 418篇 |
1982年 | 432篇 |
1981年 | 442篇 |
1980年 | 431篇 |
1979年 | 411篇 |
1978年 | 406篇 |
1977年 | 402篇 |
1976年 | 375篇 |
1975年 | 368篇 |
1974年 | 354篇 |
1973年 | 292篇 |
排序方式: 共有10000条查询结果,搜索用时 906 毫秒
251.
252.
253.
V. Shatokhin T. Wellens C. A. Müller A. Buchleitner 《The European physical journal. Special topics》2007,151(1):51-57
We survey recent progress achieved in understanding the
impact of inelastic processes on coherent backscattering of light
from cold atoms that are saturated by a powerful laser field. 相似文献
254.
255.
akir Aydoan Mustafa Salam Abdulmecit Türüt 《Journal of Polymer Science.Polymer Physics》2006,44(11):1572-1579
The polypyrrole/p‐InP structure has been fabricated by the electrochemical polymerization of the organic polypyrrole onto the p‐InP substrate. The current–voltage (I–V), capacitance–voltage (C–V), and capacitance–frequency (C–f) characteristics of the PPy/p‐InP structure have been determined at room temperature. The structure showed nonideal I–V behavior with the ideality factor and the barrier height 1.48 and 0.69 eV respectively. C–f measurements of the structure have been carried out using the Schottky capacitance spectroscopy technique and it has been seen that there is a good agreement between the experimental and theoretical values. Also, it has been seen that capacitance almost show a plateau up to a certain value of frequency, after which, the capacitance decreases. The higher values of capacitance at low frequencies were attributed to the excess capacitance resulting from the interface states in equilibrium with the p‐InP that can follow the a.c. signal. The interface state density Nss and relaxation time τ of the structure were determined from C–f characteristics. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1572–1579, 2006 相似文献
256.
Monika Schuster Robert Inführ Claudia Turecek Jürgen Stampfl Franz Varga Robert Liska 《Monatshefte für Chemie / Chemical Monthly》2006,4(4):843-853
To substitute cross-linked photopolymers in rapid prototyping of mold materials and therefore extend the range of materials
which can be casted, organo-soluble photopolymers were developed. Branched bisalkylacrylamides were suitable as base component
for such formulations, due to their high reactivity, good mechanical properties, and excellent solubility of the formed polymers.
These molding materials were used to prepare cellular biocompatible materials which could be used as bone replacement materials.
Biocompatible crosslinkers based on methacrylates from hydrolyzed gelatine or lactic acid ethyleneglycol blockcopolymers and
commercially available reactive diluents are the base components of such a formulation. Biocompatibility was investigated
by osteoblast-like cells. Cellular biocompatible parts were obtained by thermal polymerization in soluble mould materials
prepared by 3D-photoshaping. 相似文献
257.
Uwe Bandelow Mindaugas Radziunas Andrei Vladimirov Bernd Hüttl Ronald Kaiser 《Optical and Quantum Electronics》2006,38(4-6):495-512
We study both theoretically and experimentally typical operation regimes of 40 GHz monolithic mode-locked lasers. The underlying
Traveling Wave Equation model reveals quantitative agreement for characteristics of the fundamental mode-locking as pulse
width and repetition frequency tuning, as well as qualitative agreement with the experiments for other dynamic regimes. Especially
the appearance of stable harmonic mode-locking at 80 GHz has been predicted theoretically and confirmed by measurements. Furthermore,
we derive and apply a simplified Delay-Differential-Equation model which guides us to a qualitative analysis of bifurcations
responsible for the appearance and the breakup of different mode-locking regimes. Higher harmonics of mode-locking are predicted
by this model as well. 相似文献
258.
M.M. El-Nahass M.A.M. Seyam H.E.A. El-Sayed A.M. Abd El-Barry 《Applied Surface Science》2006,252(18):6218-6227
Thin films of samples of the glassy SxSe100−x system with 0 ≤ x ≤ 7.28 have been prepared by thermal evaporation technique at room temperature (300 K). X-ray investigations show that the structure of pure selenium (Se) does change seriously by the addition of small amount of sulphur S ≤7.28%. The lattice parameters were determined as a function of sulphur content. Results of differential thermal analysis (DTA) of the glassy compositions of the system SxSe100−x were discussed. The characteristic temperatures (Tg, Tc and Tm) were evaluated. Dark electrical resistivities, ρ, of SxSe100−x thin films with different thicknesses from 100 to 500 nm, were measured in the temperature range from 300 to 423 K. Two distinct linear parts with different activation energies were observed. The variation of electrical resistivity of examined compositions has been discussed as a function of the film thickness, temperature and the sulphur content. The application of Mott model for the phonon assisted hopping of small polarons gave the same two activation energies obtained from the resistivity temperature calculations. 相似文献
259.
In this article, local optimality in multiobjective combinatorial optimization is used as a baseline for the design and analysis
of two iterative improvement algorithms. Both algorithms search in a neighborhood that is defined on a collection of sets
of feasible solutions and their acceptance criterion is based on outperformance relations. Proofs of the soundness and completeness
of these algorithms are given. 相似文献
260.
I. N. Koprinarov U. Müller-Jahreis P. Thiele 《Applied Physics A: Materials Science & Processing》1996,62(6):565-570
The crystalline-amorphous transition in GaAs induced by Ar ions (energy 1–3 keV) has been investigated using single-wavelength ellipsometry. The experiments have been performed in-situ at room temperature. Ion damage straggling, amorphization threshold and critical energy density have been derived by means of a simple analytical model for the growth of the amorphous layer. This model is discussed and the corresponding calculations are found to be in satisfactory agreement with experimental data. 相似文献