全文获取类型
收费全文 | 2476篇 |
免费 | 150篇 |
国内免费 | 36篇 |
专业分类
化学 | 69篇 |
晶体学 | 1篇 |
力学 | 144篇 |
综合类 | 9篇 |
数学 | 592篇 |
物理学 | 503篇 |
无线电 | 1344篇 |
出版年
2024年 | 1篇 |
2023年 | 34篇 |
2022年 | 38篇 |
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 31篇 |
2018年 | 40篇 |
2017年 | 57篇 |
2016年 | 62篇 |
2015年 | 84篇 |
2014年 | 156篇 |
2013年 | 165篇 |
2012年 | 139篇 |
2011年 | 177篇 |
2010年 | 126篇 |
2009年 | 174篇 |
2008年 | 169篇 |
2007年 | 138篇 |
2006年 | 117篇 |
2005年 | 122篇 |
2004年 | 92篇 |
2003年 | 80篇 |
2002年 | 78篇 |
2001年 | 63篇 |
2000年 | 55篇 |
1999年 | 54篇 |
1998年 | 48篇 |
1997年 | 38篇 |
1996年 | 41篇 |
1995年 | 42篇 |
1994年 | 31篇 |
1993年 | 34篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有2662条查询结果,搜索用时 390 毫秒
161.
Zenon Hendzel 《Nonlinear dynamics》2007,50(4):849-855
In this paper, we propose a new application of the adaptive critic methodology for the feedback control of wheeled mobile
robots, based on a critic signal provided by a neural network (NN). The adaptive critic architecture uses a high-level supervisory
NN adaptive critic element (ACE), to generate the reinforcement signal to optimise the associative search element (ASE), which
is applied to approximate the non-linear functions of the mobile robot. The proposed tracking controller is derived from Lyapunov
stability theory and can guarantee tracking performance and stability. A series of computer simulations have been used to
emulate the performance of the proposed solution for a wheeled mobile robot. 相似文献
162.
在FPGA中用查找表技术实现数控振荡器是软件无线电研究的重要内容。累加器步长、累加器控制字等参数决定NCOs的性能,频谱纯度是衡量NCOs的关键指标。借助Simulink仿真平台分析得出相位截断对频谱纯度的影响远大于幅度值的量化。提出相位加抖技术及三种实现提高无杂散动态范围的方法。由仿真分析看出,通过恰当的相位加抖可以极大地提高SFDR。 相似文献
163.
164.
This paper presents a method to reduce the energy consumption of multi-core systems characterized by processor cores and buses with discrete frequency levels under timing constraints. The proposed method takes the transformations of the original task graphs, which include dependent tasks located in different iterations, as inputs. The proposed method utilizes mapping selection as well as joint processor and communication frequency scaling to implement energy reduction. We conduct experiments on several random task graphs. Experimental results show that the proposed method can achieve substantial energy reduction compared with previous work under the same hard timing constraints. 相似文献
165.
In this paper we present a general formalism for the establishment and mean-square performance analysis of the family of selective partial update affine projection (SPU-AP), selective regressor affine projection (SR-AP), and selective partial update subband adaptive filter (SPU-SAF) algorithms. This analysis is based on energy conservation arguments and does not need to assume a Gaussian or white distribution for the regressors. We demonstrate through simulations that the results are useful in predicting the performance of these adaptive filter algorithms. 相似文献
166.
This work presents chaos synchronization between two different hyperchaotic systems using adaptive control. The sufficient conditions for achieving synchronization of two high dimensional chaotic systems are derived based on Lyapunov stability theory, and an adaptive control law and a parameter update rule for unknown parameters are given such that generalized Henon–Heiles system is controlled to be hyperchaotic Chen system. Theoretical analysis and numerical simulations are shown to verify the results. 相似文献
167.
This paper presents a multicarrier communication system which transmits information on independent subcarriers to achieve an increased data rate. For this system, a passive-phase conjugation (PPC) based receiver structure is assessed by processing data collected in sea trials. Based on temporal diversity (pulse compression) exploited by PPC processing, an adaptive multichannel decision feedback equalizer is used to remove intersymbol interference, where spatial diversity is exploited by adaptive multichannel combination. The digital phase-locked loop (DPLL) technique is implemented for carrier-phase tracking. In the scenario of low input signal-to-noise ratios (SNRs), the receiver structure achieved superior performance using a common DPLL. In a depth-fluctuated environment, two sea experiments were conducted over ranges of 2 km and 4 km, respectively, and this communication system was assessed with a data rate of 4 kbps. In terms of mean square error, output SNR and bit error rate, this receiver structure has demonstrated its performance for the multicarrier communication system. 相似文献
168.
We introduce a second-order solver for the Poisson–Boltzmann equation in arbitrary geometry in two and three spatial dimensions. The method differs from existing methods solving the Poisson–Boltzmann equation in the two following ways: first, non-graded Quadtree (in two spatial dimensions) and Octree (in three spatial dimensions) grid structures are used; Second, Neumann or Robin boundary conditions are enforced at the irregular domain’s boundary. The irregular domain is described implicitly and the grid needs not to conform to the domain’s boundary, which makes grid generation straightforward and robust. The linear system is symmetric, positive definite in the case where the grid is uniform, nonsymmetric otherwise. In this case, the resulting matrix is an M-matrix, thus the linear system is invertible. Convergence examples are given in both two and three spatial dimensions and demonstrate that the solution is second-order accurate and that Quadtree/Octree grid structures save a significant amount of computational power at no sacrifice in accuracy. 相似文献
169.
C. Michoski C. Mirabito C. Dawson D. Wirasaet E.J. Kubatko J.J. Westerink 《Journal of computational physics》2011,230(22):8028-8056
We study a family of generalized slope limiters in two dimensions for Runge–Kutta discontinuous Galerkin (RKDG) solutions of advection-diffusion systems. We analyze the numerical behavior of these limiters applied to a pair of model problems, comparing the error of the approximate solutions, and discuss each limiter’s advantages and disadvantages. We then introduce a series of coupled p-enrichment schemes that may be used as standalone dynamic p-enrichment strategies, or may be augmented via any in the family of variable-in-p slope limiters presented. 相似文献
170.
Hui-Chuan Cheng 《Optics Communications》2011,284(8):2118-2121
We report an adaptive mechanical-wetting lens actuated by ferrofluids. The ferrofluids works like a piston to pump liquids in and out from the lens chamber, which in turn reshapes the lens curvature and changes the focal length. Both positive and negative lenses are demonstrated experimentally. The ferrofluid-actuated mechanical-wetting lens exhibits some attractive features, such as high resolution, fast response time, low power consumption, simple structure and electronic control, weak gravity effect, and low cost. Its potential applications in medical imaging, surveillance, and commercial electronics are foreseeable. 相似文献