全文获取类型
收费全文 | 223384篇 |
免费 | 43210篇 |
国内免费 | 31806篇 |
专业分类
化学 | 150649篇 |
晶体学 | 2528篇 |
力学 | 14418篇 |
综合类 | 954篇 |
数学 | 28681篇 |
物理学 | 101170篇 |
出版年
2024年 | 640篇 |
2023年 | 3465篇 |
2022年 | 5076篇 |
2021年 | 5781篇 |
2020年 | 6752篇 |
2019年 | 6870篇 |
2018年 | 6370篇 |
2017年 | 6426篇 |
2016年 | 9040篇 |
2015年 | 8966篇 |
2014年 | 10428篇 |
2013年 | 14778篇 |
2012年 | 17116篇 |
2011年 | 19073篇 |
2010年 | 18083篇 |
2009年 | 17907篇 |
2008年 | 12686篇 |
2007年 | 11378篇 |
2006年 | 10501篇 |
2005年 | 9460篇 |
2004年 | 8619篇 |
2003年 | 6988篇 |
2002年 | 6419篇 |
2001年 | 6193篇 |
2000年 | 5054篇 |
1999年 | 5579篇 |
1998年 | 4642篇 |
1997年 | 4304篇 |
1996年 | 4657篇 |
1995年 | 4695篇 |
1994年 | 4552篇 |
1993年 | 4217篇 |
1992年 | 3740篇 |
1991年 | 3207篇 |
1990年 | 2699篇 |
1989年 | 2582篇 |
1988年 | 2392篇 |
1987年 | 1636篇 |
1986年 | 1675篇 |
1985年 | 1266篇 |
1984年 | 1277篇 |
1983年 | 582篇 |
1982年 | 1073篇 |
1981年 | 867篇 |
1980年 | 880篇 |
1979年 | 580篇 |
1978年 | 582篇 |
1977年 | 690篇 |
1976年 | 1093篇 |
1972年 | 548篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
911.
Xuechao Li 《Graphs and Combinatorics》2006,22(4):503-513
In this paper, we give new lower bounds for the size of Δ-critical graphs with Δ=8,9 which improve the partial results of
Luo [6] and Y. Zhao [12]. 相似文献
912.
注重内涵,以创新求跨越,持续发展,建设国家物理学基础科学人才培养基地——中国科学技术大学国家物理学基础科学人才培养基地建设总结 总被引:1,自引:1,他引:0
中国科学技术大学国家物理学基础科学人才培养基地 《大学物理》2006,25(9):49-54
介绍了中国科学技术大学国家物理学基础科学人才培养基地的建设经验.基地传承了“科学与技术、科研与教学、理论与实践”相结合的中国科学技术大学办学特色,充分发挥基地物理学科门类齐全、学风优良、师资力量雄厚的综合优势,以培养具有宽厚知识、创新能力和探索精神的创新人才为目标,对物理理论课和物理实验课课程体系、教学内容、教学方法等方面作了全面的改革,取得了显著成果. 相似文献
913.
The phase boundary theory and the contact rule of phase regions are compared, and some weaknesses of the latter are manifested.
The comparison between the Gupta’s method and the boundary theory method for constructing multicomponent isobaric sections
is also presented. 相似文献
914.
R. Minami A. Kasugai K. Takahashi N. Kobayashi Y. Mitsunaka K. Sakamoto 《International Journal of Infrared and Millimeter Waves》2006,27(1):13-24
A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A
helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have
been optimized for the TE31.8 mode at 170 GHz and TE22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking
the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing
in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design.
High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the
thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of
high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons. 相似文献
915.
In this paper, the relation between synchronization and pattern formation in one-dimensional discrete and continuous open flow models is investigated in detail. Firstly a sufficient condition for globally asymptotical stability of lag/anticipating synchronization among lattices of these models is proved by analytic method. Then, by analyzing and simulating lag/anticipating synchronization in discrete case, three kinds of pattern of wave (it is called wave pattern) travelling in the lattices are discovered. Finally, a proper definition for these kinds of pattern is proposed. 相似文献
916.
In this paper, we first reduce the problem of finding a minimum parity (g,f)-factor of a graph G into the problem of finding a minimum perfect matching in a weighted simple graph G*. Using the structure of G*, a necessary and sufficient condition for the existence of an even factor is derived.
This paper was accomplished while the second author was visiting the Center for Combinatorics, Nankai University.
The research is supported by NSFC 相似文献
917.
918.
In situ flying height testing technology is becoming more and more important in slider–disk interaction analysis and manufacturing quality control of disk drives and head-related components. Triple harmonic method is a quite promising choice for in situ flying height analysis, compared with other in situ methods reported up to now. This paper reports results of investigations on engineering issues of applying triple harmonic method for in situ flying height analysis. The paper reports results of analysis on the effects of various testing conditions on flying height testing repeatability and accuracy. Results suggest that working at reasonable high channel density and working on the ratio between third and first harmonics will be an advantage in terms of both flying height testing sensitivity and testing repeatability. Comparing with media thickness effect, the gap-length variation among different heads will be important if it is to study flying height difference among different heads and the testing is at high channel density. Also, it is suggested to work at AC erased track, in order to reduce the non-linearity caused by hard transition. 相似文献
919.
N.A. Buznikov A.S. Antonov A.B. Granovsky C.G. Kim C.O. Kim X.P. Li S.S. Yoon 《Journal of magnetism and magnetic materials》2006
The giant magnetoimpedance effect in composite wires consisting of a non-magnetic inner core and soft magnetic shell is studied theoretically. It is assumed that the magnetic shell has a helical anisotropy. The current and field distributions in the composite wire are found by means of a simultaneous solution of Maxwell equations and the Landau–Lifshitz equation. The expressions for the diagonal and off-diagonal impedance are obtained for low and high frequencies. The dependences of the impedance on the anisotropy axis angle and the shell thickness are analyzed. Maximum field sensitivity is shown to correspond to the case of the circular anisotropy in the magnetic shell. It is demonstrated that the optimum shell thickness to obtain maximum impedance ratio is equal to the effective skin depth in the magnetic material. 相似文献
920.
X.J. Liu E.Y. Jiang Z.Q. Li B.L. Li W.R. Li A. Yu P. Wu H.L. Bai 《Journal of magnetism and magnetic materials》2006
We have investigated the magnetic, electrical transport and electron spin resonance (ESR) properties of polycrystalline Nd0.85Na0.15MnO3 prepared by sol–gel method. A ferromagnetic–paramagnetic (FM–PM) transition is observed around 110 K, which is not accompanied by a metal–insulator transition. The sample displays the complete PM state associated with the ESR spectra fitted by single Lorentzian line shape above 130 K. Below 130 K, ESR spectra become distorted and then linewidth increases rapidly, where short-range magnetic order develops and coexists with PM phase due to the inhomogeneous magnetic state. In addition, the large difference between the activation energies obtained from the resistivity and ESR parameters (peak-to-peak linewidth and line intensity) at the frame of adiabatic small polaron hopping model is pointed out for Nd0.85Na0.15MnO3. 相似文献