全文获取类型
收费全文 | 24081篇 |
免费 | 2741篇 |
国内免费 | 1669篇 |
专业分类
化学 | 12738篇 |
晶体学 | 691篇 |
力学 | 841篇 |
综合类 | 71篇 |
数学 | 1065篇 |
物理学 | 13085篇 |
出版年
2024年 | 23篇 |
2023年 | 197篇 |
2022年 | 356篇 |
2021年 | 457篇 |
2020年 | 559篇 |
2019年 | 490篇 |
2018年 | 455篇 |
2017年 | 573篇 |
2016年 | 854篇 |
2015年 | 642篇 |
2014年 | 901篇 |
2013年 | 1873篇 |
2012年 | 1403篇 |
2011年 | 1580篇 |
2010年 | 1249篇 |
2009年 | 1621篇 |
2008年 | 1667篇 |
2007年 | 1922篇 |
2006年 | 1701篇 |
2005年 | 1302篇 |
2004年 | 1262篇 |
2003年 | 1001篇 |
2002年 | 885篇 |
2001年 | 688篇 |
2000年 | 687篇 |
1999年 | 565篇 |
1998年 | 542篇 |
1997年 | 366篇 |
1996年 | 457篇 |
1995年 | 389篇 |
1994年 | 341篇 |
1993年 | 270篇 |
1992年 | 241篇 |
1991年 | 160篇 |
1990年 | 136篇 |
1989年 | 102篇 |
1988年 | 105篇 |
1987年 | 68篇 |
1986年 | 65篇 |
1985年 | 72篇 |
1984年 | 63篇 |
1983年 | 22篇 |
1982年 | 33篇 |
1981年 | 45篇 |
1980年 | 12篇 |
1979年 | 20篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Y.B. Melnichenko G.D. Wignall D.R. Cole H. Frielinghaus L.A. Bulavin 《Journal of Molecular Liquids》2005,120(1-3):7-9
Small angle neutron scattering (SANS) is a well-established technique for investigating the behavior of confined binary liquid solutions, as it can probe the correlation length and susceptibility in pores on length scales 1 – 100 nm. We applied SANS to explore the influence of confinement on critical behavior of an individual fluid carbon dioxide (CO2) in a highly porous aerogel. The results demonstrate that quenched disorder induced by aerogel significantly depresses density fluctuations. Despite the negligible volume occupied by aerogel (< 4%), the macroscopic phase separation of confined CO2 into coexisting liquid and gaseous phases is suppressed and below the critical temperature of the bulk fluid frozen methastable microdomains are formed. Experimental data show that critical adsorption is as important as the effect of confinement in defining the behavior of confined fluids. 相似文献
42.
K. C. Kumara Swamy E. Balaraman M. Phani Pavan N. N. Bhuvan Kumar K. Praveen Kumar N. Satish Kumar 《Journal of Chemical Sciences》2006,118(6):495-501
The diversity of products in the reaction of diethyl azodicarboxylate (DEAD)/diisopropyl azodicarboxylate (DIAD) and activated
acetylenes with PIII compounds bearing oxygen or nitrogen substituents is discussed. New findings that are useful in understanding the nature
of intermediates involved in the Mitsunobu reaction are highlighted. X-ray structures of two new compounds (2-t-Bu-4-MeC6H3O)P (μ-N-t-Bu)2P+[(NH-t-Bu)N[(CO2]-i-Pr)(HNCO2-i-Pr)]](Cl-)(2-t-Bu-4-MeC6H3OH)(23)and [CH2(6-t-Bu-4-Me-C6H2O)2P(O)C(CO2Me)C-(CO2Me)CClNC(O)Cl] (33) are also reported. The structure of23 is close to one of the intermediates proposed in the Mitsunobu reaction. 相似文献
43.
We discuss the problem of transmitting polarized pulses along optical fibers with variable dispersion. The dissipation and mean dispersion are assumed to be zero, which allows using the model of the vector nonlinear Schrödinger equation. We consider an optical fiber consisting of arms of equal length, which is assumed to be large. We propose an asymptotic recursive procedure for calculating the amplitude and the phase of an optical pulse propagating along the optical cable with variable dispersion. 相似文献
44.
François Nicoleau 《Journal of Differential Equations》2004,205(2):354-364
We study an inverse scattering problem for a pair of Hamiltonians (H,H0) on L2(Rn), where H0=-Δ and H=H0+V, V being a short- or long-range potential. By an elementary constructive method, we show that the scattering operator S, which is localized near a fixed energy λ>0, determines the asymptotics of the potential V at infinity, in dimension n?3. This is done by studying the action of the scattering operator on suitable wave packets. 相似文献
45.
Generation of UV laser light by stimulated Raman scattering in D2, D2/Ar and D2/He using a pulsed Nd:YAG laser at 355nm
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A pulsed Nd:YAG laser at 355nm is used to pump Raman cell filled with D_2, D_2/Ar and D_2/He. With adequately adjusted parameters, the maximum photon conversion efficiency of the first-order Stokes light (S_1, 396.796nm) reaches 33.33% in D_2/Ar and the stability of S_1 in pure D_2 is fairly high, the energy drift being less than 10% when the pump energy drifts in the range of 5%. The conversion efficiency and stability, which are functions of the composition and pressure of the Raman medium and the energy of pump laser, are investigated. The result has been used to optimize the laser transmitter system for a differential absorption lidar system to measure NO_2 concentration profiles. 相似文献
46.
Ray Leslie Withers Carlos Otero-Diaz Adrian Gómez-Herrero Albert Prodan Lasse Norén 《Journal of solid state chemistry》2005,178(10):3159-3168
Ternary derivatives of 1T-TaS2 have been synthesized and the variation in the highly structured diffuse intensity distributions characteristic of such materials carefully monitored to investigate the effect that such substitution has upon the band structures and Fermi surfaces (FSs) of the materials. Removal of d electrons via the replacement of Ta ions with lower valent transition metal ions leads to a systematic increase in the radii of the characteristic structured diffuse intensity distribution. Extended Hückel tight binding calculations of the FSs of the doped samples are carried out and used to predict possible nesting wave-vectors. The results are in reasonably good agreement with the radii of the experimentally observed diffuse intensity distributions. 相似文献
47.
A brief account of applications of polarized inelastic neutron scattering in condensed matter research is given. We show that
full polarization analysis is the only tool allowing to discriminate unambiguously between different magnetic modes in various
magnetic materials. We show by means of recent results in the Heisenberg ferromagnet EuS that the effects of dipolar interactions
can be studied on a microscopic scale. Moreover, we have found for the first time indications for the divergence of the longitudinal
fluctuations belowT
c. In the itinerant antiferromagnet chromium we demonstrate that the dynamics of the longitudinal and transverse excitations
are very different, resolving a long standing puzzle concerning the slope of their dispersion. Finally, we show that a measurement
of the polarization-dependent part of the cross section of non-centrosymmetric MnSi proves directly that the chirality of
the magnetic fluctuations is left-handed. 相似文献
48.
49.
The cocrystal of 1,2-bis(diphenylphosphinoyl)ethane (DPPEO) with phenol (1:1) were studied theoretically with AM1, PM3, MNDO and MINDO/3 semi-empirical methods to elucidate its structure. The bond lengths and angles from theoretical studies of molecule DPPEO/phenol (1:1) were found to be as expected. Theoretical results, concerning with intermolecular van der Waals forces in cocrystal, were compared with the previously obtained experimental data and AM1 results were found to be the best fit for bond lengths and angles of DPPEO/phenol. 相似文献
50.