全文获取类型
收费全文 | 10966篇 |
免费 | 1536篇 |
国内免费 | 1277篇 |
专业分类
化学 | 7793篇 |
晶体学 | 119篇 |
力学 | 690篇 |
综合类 | 69篇 |
数学 | 1308篇 |
物理学 | 3800篇 |
出版年
2024年 | 62篇 |
2023年 | 276篇 |
2022年 | 432篇 |
2021年 | 441篇 |
2020年 | 458篇 |
2019年 | 464篇 |
2018年 | 404篇 |
2017年 | 391篇 |
2016年 | 535篇 |
2015年 | 526篇 |
2014年 | 605篇 |
2013年 | 818篇 |
2012年 | 906篇 |
2011年 | 953篇 |
2010年 | 660篇 |
2009年 | 598篇 |
2008年 | 726篇 |
2007年 | 605篇 |
2006年 | 552篇 |
2005年 | 413篇 |
2004年 | 370篇 |
2003年 | 280篇 |
2002年 | 313篇 |
2001年 | 211篇 |
2000年 | 203篇 |
1999年 | 259篇 |
1998年 | 181篇 |
1997年 | 133篇 |
1996年 | 142篇 |
1995年 | 133篇 |
1994年 | 99篇 |
1993年 | 108篇 |
1992年 | 88篇 |
1991年 | 87篇 |
1990年 | 78篇 |
1989年 | 58篇 |
1988年 | 42篇 |
1987年 | 36篇 |
1986年 | 21篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
251.
Control of soliton characteristics of the condensate by an arbitrary x-dependent external potential 下载免费PDF全文
This paper presents a family of soliton solutions of the one-dimensional nonlinear Schrdinger equation which describes the dynamics of the dark solitons in Bose-Einstein condensates with an arbitrary x-dependent external potential.The obtained results show that the external potential has an important effect on the dark soliton dynamical characteristics of the condensates.The amplitude,width,and velocity of the output soliton are relative to the source position of the external potential.The smaller the amplitude of the soliton is,the narrower its width is,and the slower the soliton propagates.The collision of two dark solitons is nearly elastic. 相似文献
252.
Kernel regression estimation for continuous spatial processes 总被引:1,自引:0,他引:1
We investigate here a kernel estimate of the spatial regression function r(x) = E(Y
u | X
u = x), x ∈ ℝd, of a stationary multidimensional spatial process { Z
u = (X
u, Y
u), u ∈ ℝ
N
}. The weak and strong consistency of the estimate is shown under sufficient conditions on the mixing coefficients and the
bandwidth, when the process is observed over a rectangular domain of ℝN. Special attention is paid to achieve optimal and suroptimal strong rates of convergence. It is also shown that this suroptimal
rate is preserved by using a suitable spatial sampling scheme.
相似文献
253.
254.
Using the finite-difference time-domain (FDTD) method, we simulate the coupling between a gold nanorod and gold nanoparticles
with different plasmonic resonant frequencies/volumes as well as that between the nanorod and a dielectric nanosphere. The
influences of coupling with different nanoparticles on the excitation of a forbidden longitudinal surface plasmon mode of
the nanorod under normal incidence are investigated. It is found that the cause of this excitation is the broken symmetry
of the local electric field experienced by the nanorod resulting from the charge pileup on the other nanoparticle. This result
is valuable for understanding the near-field optical characterization of plasmonic metal nanoparticles.
Supported by the National Natural Science Foundation of China (Grant Nos. 10821062 and 10804004), the National Basic Research
Program of China (Grant No. 2007CB307001), and the Specialized Research Fund for the Doctoral Program of Higher Education
(Grant No. 200800011023)
Contributed by GONG QiHuang 相似文献
255.
将存在多个工作环境的加速度计组合件温度控制受控对象描述为存在有界时变参数摄动和有界干扰的非线性时变不确定系统,提出了一种基于信号补偿的鲁棒温度控制方法,该方法设计的控制器由标称控制器和鲁棒补偿器组成.证明了闭环系统的鲁棒控制特性,实验结果显示所设计的控制系统能够在多个工作环境下实现高精度的鲁棒温度控制. 相似文献
256.
GENERALIZED SOLUTION OF SINGULARLY PERTURBED PROBLEMS FOR REACTION DIFFUSION EQUATIONS 总被引:2,自引:0,他引:2
Yao Jingsun Mo Jiaqi 《Annals of Differential Equations》2006,22(1):81-86
The singularly perturbed initial boundary value problem for reaction diffusion equation is considered. Under suitable conditions the existence, uniqueness and asymptotic behavior of the generalized solution for the problems are studied. 相似文献
257.
基于非平衡光纤干涉仪的窄线宽激光光源跳模实时测试方法 总被引:1,自引:2,他引:1
窄线宽激光器随机发生的跳模现象,是影响光学系统稳定的重要因素.激光器线宽窄往往意味着较长的谐振腔和较小的模间隔,从而给跳模的监测带来了难度.本文提出一种基于非平衡光纤干涉仪的窄线宽光源跳模测试方法,该方法将激光器跳模的频率变化转变为干涉仪的相位变化,并通过相位产生载波(PGC)调制解调技术来检测相位信息,从而实现对跳模过程的监测.该方法灵敏度高,能够长时间连续监控,测试效果优于Fabry-Pérot干涉仪,还可在kHz量级上测量窄线宽激光器的线宽,为单纵模窄线宽激光器研究提供有效的测试手段. 相似文献
258.
Recently GaN-based high electron mobility transistors (HEMTs) have
revealed the superior properties of a high breakdown field and high
electron saturation velocity. Reduction of the gate leakage current
is one of the key issues to be solved for their further improvement.
This paper reports that an Al layer as thin as 3 nm was inserted
between the conventional Ni/Au Schottky contact and n-GaN epilayers,
and the Schottky behaviour of Al/Ni/Au contact was investigated
under various annealing conditions by current--voltage (I--V)
measurements. A non-linear fitting method was used to extract the
contact parameters from the I--V characteristic curves.
Experimental results indicate that reduction of the gate leakage
current by as much as four orders of magnitude was successfully
recorded by thermal annealing. And high quality Schottky contact
with a barrier height of 0.875 eV and the lowest reverse-bias
leakage current, respectively, can be obtained under 12 min
annealing at 450°C in N2 ambience. 相似文献
259.
L.?Si Email author Y.L.?Chang J.?Ding C.K.?Ong B.?Yao 《Applied Physics A: Materials Science & Processing》2003,77(5):641-643
In order to search for new materials for the application of magnetic refrigeration, the polycrystalline perovskite compound Nd2/3Sr1/3MnO3 was prepared by a solid-state method. The dependence of the magnetization on the applied field and temperature was measured near the Curie temperature. In terms of Maxwells equation, the temperature dependence of the absolute value of the isothermal magnetic entropy change |SM| at various applied fields from 1 T to 5 T was determined. The results showed that a large magnetic entropy change was observed in this compound. The maximum magnetic entropy change |SMmax|can reach 3.25 J/kgK with an applied field of 1 T at the Curie temperature of 257.5 K, which equals that of Gd. At 5 T applied field, it is 7.57 J/kgK. Such good magnetocaloric properties make this compound a promising candidate for the application of magnetic refrigeration in the room-temperature range. PACS 74.25.Ha; 75.30.-m; 75.30.Sg; 75.50.-y; 75.60.-d 相似文献
260.
In this paper, a gap function for a system of vector equilibrium problems is introduced and studied. Some necessary and sufficient
conditions for the system of vector equilibrium problems are established. Characterizations of the solutions set for the system
of vector equilibrium problems are also derived. Furthermore, some existence results of solutions for the system of vector
equilibrium problems are proved.
This work was supported by the National Natural Science Foundation of China, the Youth Foundation, Sichuan Education Department
of China, the National Natural Science Foundation, Sichuan Education Department of China (2004C018), and a grant from the
National Science Council of ROC. 相似文献