全文获取类型
收费全文 | 3116篇 |
免费 | 1175篇 |
国内免费 | 448篇 |
专业分类
化学 | 582篇 |
晶体学 | 32篇 |
力学 | 127篇 |
综合类 | 246篇 |
数学 | 902篇 |
物理学 | 2850篇 |
出版年
2024年 | 37篇 |
2023年 | 96篇 |
2022年 | 152篇 |
2021年 | 119篇 |
2020年 | 108篇 |
2019年 | 85篇 |
2018年 | 74篇 |
2017年 | 126篇 |
2016年 | 149篇 |
2015年 | 141篇 |
2014年 | 312篇 |
2013年 | 217篇 |
2012年 | 278篇 |
2011年 | 296篇 |
2010年 | 228篇 |
2009年 | 172篇 |
2008年 | 230篇 |
2007年 | 193篇 |
2006年 | 176篇 |
2005年 | 153篇 |
2004年 | 180篇 |
2003年 | 170篇 |
2002年 | 154篇 |
2001年 | 130篇 |
2000年 | 117篇 |
1999年 | 80篇 |
1998年 | 82篇 |
1997年 | 69篇 |
1996年 | 60篇 |
1995年 | 40篇 |
1994年 | 60篇 |
1993年 | 44篇 |
1992年 | 43篇 |
1991年 | 28篇 |
1990年 | 34篇 |
1989年 | 25篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
排序方式: 共有4739条查询结果,搜索用时 31 毫秒
61.
在虚拟仪器平台上演示负载与功率的关系 总被引:1,自引:0,他引:1
Lab VIEW又称实验室虚拟仪器工程平台,是美国NI公司推出的一种基于G语言的虚拟仪器软件开发工具,用Lab VIEW设计的虚拟仪器可脱离Lab VIEW开发环境,最终用户看见的是和实际的硬件仪器相似的操作面板. 相似文献
62.
63.
当外电路的电阻等于电源内电阻时,电源输出功率最大,应用这个结论,可以省去许多计算步骤.但实际应用时还要注意一些问题,下面从几个方面加以讨论.1 电源实际输出功率与最大输出功率的区别 这是两个不同的概念,一些学生往往会用Pm=(?)/4r计算电源输出最大功率,其实,(?)/4r只是电源输出功率的极限,电源一般不在该状态下工作. 相似文献
64.
65.
Multiplexing Chaotic Signals Generated by Colpitts Oscillator and Chua Circuit Using Dual Synchronization 下载免费PDF全文
We demonstrate multiplexing chaotic signals generated by two totally different dynamic systems (one is a Colpitts oscillator and the other is a Chua circuit) using dual synchronization and propose a method to select the proper coupling parameters. In the response systems, the cross coupling method is used, in which the voltage difference between the sum of two master oscillators and one slave oscillator is converted to current and then feed into the other slave oscillator. The result in this letter offers a potential multiuser coherent chaotic communication scheme where different chaotic oscillators can be used in one system. 相似文献
66.
LIKAITAI HEYINNIAN XIANGYIMIN 《高校应用数学学报(英文版)》1994,9(1):11-30
This paper deals with the inertial manifold and the approximate inertial manifold concepts of the Navier-Stokes equations with nonhomogeneous boundary conditions and inertial algorithm. Furtheremore, we provide the error estimates of the approximate solutions of the Navier-Stokes Equations. 相似文献
67.
物理实验微机接口及辅助教学系统设计 总被引:4,自引:1,他引:3
介绍了国家八五科技项目(攻关)子专题“物理实验计算机接口系列及辅助教学系统的研制”的设计方案,包括硬件设计和软件设计,给出了有关接口电路、信号调理电路、传感器电路,及部分软件的框图. 相似文献
68.
Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B1∏ of 7LiH 下载免费PDF全文
The reasonable dissociation limit of the second excited singlet state
B1∏ of 7LiH molecule is obtained. The accurate dissociation energy and
equilibrium geometry of the B1\Pi state are calculated using a
symmetry-adapted-cluster configuration--interaction method in full active space. The
whole potential energy curve for the B1∏ state is obtained over the
internuclear distance ranging from about 0.10nm to 0.54nm, and has a least-square
fit to the analytic Murrell--Sorbie function form. The vertical excitation energy is
calculated from the ground state to the
B1∏ state and compared with previous theoretical results. The
equilibrium internuclear distance obtained by geometry optimization is found to be
quite different from that obtained by single-point energy scanning under the same
calculation condition. Based on the analytic potential energy function, the harmonic
frequency value of the B1∏ state is estimated. A comparison of the
theoretical calculations of dissociation energies, equilibrium interatomic distances
and the analytic potential energy function with those obtained by previous
theoretical results clearly shows that the present work is more comprehensive and in
better agreement with experiments than previous theories, thus it is an improvement
on previous theories. 相似文献
69.
Design of Two-Dimensional Photonic Crystal Edge Emitting Laser for Photonic Integrated Circuits 下载免费PDF全文
An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of air-holes, and a waveguide. In the cavity, laser resonance in the inner structure benefits from not only the anomalous dispersion characteristic of the first band-edge at the M point in the first Brillouin-zone but also zero photon states in the outer structure. A line defect waveguide is introduced in the outer structure for extracting photons from the inner cavity. Three-dimensional finite-difference time-domain simulations apparently show the in-plane laser output from the waveguide. The microcavity has an effective mode volume of about 3.2(λ/nslab)^3 for oscillation mode and the quality factor of the device including line defect waveguide is estimated to be as high as 1300. 相似文献
70.
单电子效应与单电子晶体管 总被引:2,自引:0,他引:2
由于半导体超微细加工技术的发展,在半径为几百nm的量子点结构上观察到由单个电子的阻塞和隧穿引起的电流振荡,分别称为库仑阻塞,单电子隧穿和库仑振荡,与此效应有关的现象还有库仑台阶,旋转门效应,旋转门器件可利用作为电流标准测量,单电子晶体管将是下世纪大容量存贮器的最好选择,单电子效应的研究将开辟一门新的“人造原子物理学”。 相似文献