全文获取类型
收费全文 | 47537篇 |
免费 | 1339篇 |
国内免费 | 16篇 |
专业分类
化学 | 29092篇 |
晶体学 | 244篇 |
力学 | 787篇 |
综合类 | 1篇 |
数学 | 8824篇 |
物理学 | 9944篇 |
出版年
2023年 | 354篇 |
2022年 | 306篇 |
2021年 | 510篇 |
2020年 | 711篇 |
2019年 | 659篇 |
2018年 | 974篇 |
2017年 | 891篇 |
2016年 | 1722篇 |
2015年 | 1440篇 |
2014年 | 1391篇 |
2013年 | 3100篇 |
2012年 | 2969篇 |
2011年 | 2789篇 |
2010年 | 1858篇 |
2009年 | 1561篇 |
2008年 | 2442篇 |
2007年 | 2220篇 |
2006年 | 1965篇 |
2005年 | 2022篇 |
2004年 | 1733篇 |
2003年 | 1438篇 |
2002年 | 1252篇 |
2001年 | 961篇 |
2000年 | 957篇 |
1999年 | 669篇 |
1998年 | 518篇 |
1997年 | 437篇 |
1996年 | 576篇 |
1995年 | 411篇 |
1994年 | 488篇 |
1993年 | 441篇 |
1992年 | 471篇 |
1991年 | 398篇 |
1990年 | 444篇 |
1989年 | 361篇 |
1988年 | 367篇 |
1987年 | 329篇 |
1986年 | 320篇 |
1985年 | 446篇 |
1984年 | 410篇 |
1983年 | 325篇 |
1982年 | 326篇 |
1981年 | 342篇 |
1980年 | 282篇 |
1979年 | 272篇 |
1978年 | 271篇 |
1977年 | 262篇 |
1976年 | 278篇 |
1974年 | 250篇 |
1973年 | 263篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Oscillating nature of current pulses under d.c. excitation in subnormal region with longitudinal magnetic field at pressure
range 0.20 torr to 0.85 torr have been studied. The frequency, bandwidth, peak-peak voltage, cut-off current and rise time
of the current pulses have been observed with pressure, average tube current and magnetic field. A study of these oscillograms
in magnetic field, average tube current and pressure are presented. The probable mechanism for the generation of oscillation
based on space-charge field modification with magnetic field is discussed 相似文献
72.
Experiments in dc supplied corona discharge in natural gas + air mixture and in combustion exhaust of natural gas + air mixture were realized. The influence of discharge on CO, CO2, NO
x
and other minority components was studied using IR absorption spectrometry. Production of NCO radicals in gas and consequent formation of NCO containing surface layers on a plate electrode was detected. In natural gas + air mixture after about 1 min oxygen poor combustion exhaust was produced due to slow combustion by corona discharge. Occurrence of various pulses in discharge current was typical. 相似文献
73.
Fernández F. R. Monroy L. Puerto J. 《Journal of Optimization Theory and Applications》1998,99(2):403-421
In this paper, we deal with multicriteria matrix games. Different solution concepts have been proposed to cope with these games. Recently, the concept of Pareto-optimal security strategy which assures the property of security in the individual criteria against an opponent's deviation in strategy has been introduced. However, the idea of security behind this concept is based on expected values, so that this security might be violated by mixed strategies when replications are not allowed. To avoid this inconvenience, we propose in this paper a new concept of solution for these games: the G-goal security strategy, which includes as part of the solution the probability of obtaining prespecified values in the payoff functions. Thus, attitude toward risk together with payoff values are considered jointly in the solution analysis. 相似文献
74.
It is shown that the non-trivial cocycles on simple Lie algebras may be used to introduce antisymmetric multibrackets which
lead to higher-order Lie algebras, the definition of which is given. Their generalised Jacobi identities turn out to be satisfied
by the antisymmetric tensors (or higher-order “structure constants”) which characterise the Lie algebra cocycles. This analysis
allows us to present a classification of the higher-order simple Lie algebras as well as a constructive procedure for them.
Our results are synthesised by the introduction of a single, complete BRST operator associated with each simple algebra.
Received: 3 June 1996 / Accepted: 8 November 1996 相似文献
75.
A.V. Andreev B. Janoušová V. Sechovský Y. Homma Y. Shiokawa 《Czechoslovak Journal of Physics》2002,52(2):275-278
We present the first single-crystal study of Fe and Ni doped U(Co1-x
T
x
)Al compounds in comparison to the parent compound, the itinerant 5f-electron metamagnet UCoAl. Magnetization and specific-heat data measured in the temperature range of (1.8-300) K and in fields up to 10 T are analyzed and discussed. Both compounds exhibit a strong uniaxial anisotropy with the dominating magnetic response along the c-axis of the hexagonal ZrNiAl-type structure. Ni substitution yields an increase of the critical field for metamagnetism; UCo0.95Fe0.05Al is ferromagnetic below 30 K. Temperature evolution of the entropy change between 0 and 10 T points to involvement of magnetic correlations or spin fluctuations in the paramagnetic compounds UCoAl and UCo0.95Ni0.05Al. 相似文献
76.
D. Kaptás T. Kemény J. Balogh L. F. Kiss L. Gránásy I. Vincze 《Hyperfine Interactions》1994,94(1):1861-1865
The temperature dependence of the iron hyperfine field distribution is reported in melt-quenched amorphous Fe-Zr alloys. The most remarkable feature is the compositinal change in the shape of the average hyperfine field versus temperature curves. The unusual increase in the average hyperfine field below about 85 K is a characteristic feature of the RSG systems; however, no anomaly is observed in the width of the hyperfine field distribution as a function of temperature. The results cannot be properly explained in the framework of the existing spin glass models. 相似文献
77.
We present a way of introducing joint distibution function and its marginal distribution functions for non-compatible observables.
Each such marginal distribution function has the property of commutativity. Models based on this approach can be used to better
explain some classical phenomena in stochastic processes. 相似文献
78.
Zólomy A. Berceli T. Járó G. Hilt A. Marozsák T. 《Optical and Quantum Electronics》1998,30(11-12):969-983
Optical and Quantum Electronics - A new approach for the design and construction of low noise broadband optical receivers is presented utilizing distributed amplification based on hybrid integrated... 相似文献
79.
F. Máca 《Czechoslovak Journal of Physics》1993,43(9-10):941-945
We present the calculations of electronic structure and photoemission spectra for a lattice-matched Ag-Au(111) superlattice. The selfconsistent band structure exhibits a superlattice gap at about 1 eV below the Fermi level. A surface state is found in this gap and its dispersion properties are investigated. Its energy location is varied with location of surface terminating plane within the superlattice period. The calculated normal photoemission spectra explain well available experimental data. 相似文献
80.
José Natário 《General Relativity and Gravitation》2006,38(3):475-484
We find a class of warp drive spacetimes possessing Newtonian limits, which we then determine. The same method is used to
compute Newtonian limits of the Schwarzschild solution and spatially flat Friedmann-Robertson-Walker cosmological models.
This work was partially supported by FCT/POCTI/FEDER. 相似文献