全文获取类型
收费全文 | 6864篇 |
免费 | 1050篇 |
国内免费 | 491篇 |
专业分类
化学 | 1192篇 |
晶体学 | 19篇 |
力学 | 714篇 |
综合类 | 64篇 |
数学 | 803篇 |
物理学 | 5613篇 |
出版年
2024年 | 6篇 |
2023年 | 49篇 |
2022年 | 128篇 |
2021年 | 122篇 |
2020年 | 130篇 |
2019年 | 98篇 |
2018年 | 113篇 |
2017年 | 274篇 |
2016年 | 286篇 |
2015年 | 261篇 |
2014年 | 462篇 |
2013年 | 448篇 |
2012年 | 420篇 |
2011年 | 465篇 |
2010年 | 355篇 |
2009年 | 414篇 |
2008年 | 496篇 |
2007年 | 512篇 |
2006年 | 415篇 |
2005年 | 345篇 |
2004年 | 337篇 |
2003年 | 301篇 |
2002年 | 251篇 |
2001年 | 258篇 |
2000年 | 218篇 |
1999年 | 185篇 |
1998年 | 177篇 |
1997年 | 164篇 |
1996年 | 126篇 |
1995年 | 100篇 |
1994年 | 73篇 |
1993年 | 71篇 |
1992年 | 50篇 |
1991年 | 49篇 |
1990年 | 43篇 |
1989年 | 32篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 12篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 10篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有8405条查询结果,搜索用时 680 毫秒
961.
Naum K. Berger 《Optics Communications》2010,283(7):1397-1405
We propose a method for the measurement of periodic optical waveforms based on the use of an electrooptic phase modulator placed in an optical Fabry-Perot or ring resonator. Significant broadening of the modulation spectrum extends the recently developed method of periodic modulation for pulse characterization into femtosecond scales. We numerically demonstrate the characterization of a 300-fs optical pulse. We also present a technique based on the temporal fractional Talbot effect for restoration of the pulse phase profile. After fast linear processing, subpicosecond pulses will be observed on the screen of a real-time oscilloscope. This complete characterization of optical pulses is entirely linear and therefore highly sensitive and simple in implementation. 相似文献
962.
A tellurite glass fiber with a high Brillouin gain was employed for distributed strain measurement with Brillouin optical correlation-domain reflectometry (BOCDR). First, the spatial resolution of BOCDR was evaluated using the tellurite fiber. With the high Brillouin gain of the fiber, it was confirmed clearly in the experiment that the spatial resolution is limited by the Rayleigh scattering-induced noise. Then, the dependence of the Brillouin frequency shift (BFS) on strain in the tellurite fiber was investigated, showing a negative dependence with a coefficient of −0.023 MHz/με. Using this tellurite fiber, the distribution of the BFS around a 1-cm strain-applied section was successfully measured with BOCDR of a nominal spatial resolution of 6 mm. 相似文献
963.
Zhiling Hou 《Optik》2010,121(14):1324-1329
In the three-dimensional (3D) phase measurement, some marks are usually adhered to the object in order to make the 3D registration process faster and easier. As covered with marks, local phase data are missing and have to be interpolated later. Considering the phase distribution nearby the marks, a gradient estimate (GE) interpolation algorithm is provided here. This algorithm recovers one pixel's missing phase value with the average of the estimated values which is calculated by gradients in eight directions nearby. Since this algorithm is a local processing, the missing phase values should be interpolated from the edge of the marks to the center. In the computer simulation and the practical experiment, compared with the same-size neighborhood mean (NM) algorithm and the Gerchberg-Saxton (GS) algorithm, this new algorithm achieves very good fit results with the least time. So it can be used as a practical tool for automatic missing phase interpolation. 相似文献
964.
Adaptive Penalized Weighted Least Absolute Deviations Estimation for the Accelerated Failure Time Model 下载免费PDF全文
The accelerated failure time model always offers a valuable complement to the traditional Cox proportional hazards model due to its direct and meaningful interpretation. We propose a variable selection method in the context of the accelerated failure time model for survival data, which can simultaneously complete variable selection and parameter estimation. Meanwhile, the proposed method can deal with the potential outliers in survival times as well as heteroscedastic model errors, which are frequently encountered in practice. Specifically, utilizing the general nonconvex penalty, we propose the adaptive penalized weighted least absolute deviation estimator for the accelerated failure time model. Under some regularity conditions, we show that the proposed method yields consistent estimator and possesses the oracle property. In addition, we propose a new algorithm to compute the estimate in the high dimensional settings, and evaluate the practical utility of the proposed method through extensive simulation studies and two real examples. 相似文献
965.
In this paper, we present a local Csrg–Révész type functional limit theorem for increments of Brownian motion and give its convergence rate. The results also extend the functional forms of Lévy's modulus of continuity for Brownian motion. 相似文献
966.
In this paper, we consider the stochastic heat equation of the form $$\frac{\partial u}{\partial t}=(\Delta_\alpha+\Delta_\beta)u+\frac{\partial f}{\partial x}(t,x,u)+\frac{\partial^2W}{\partial t\partial x},$$ where $1<\beta<\alpha< 2$, $W(t,x)$ is a fractional Brownian sheet, $\Delta_\theta:=-(-\Delta)^{\theta/2}$ denotes the fractional Lapalacian operator and $f:[0,T]\times \mathbb{R}\times \mathbb{R}\rightarrow\mathbb{R}$ is a nonlinear measurable function. We introduce the existence, uniqueness and H\"older regularity of the solution. As a related question, we consider also a large deviation principle associated with the above equation with a small perturbation via an equivalence relationship between Laplace principle and large deviation principle. 相似文献
967.
S. Dereich 《Journal of Functional Analysis》2010,258(9):2910-2936
In this article, we carry out a rough paths analysis for Banach space-valued Wiener processes. We show that most of the features of the classical Wiener process pertain to its rough path analog. To be more precise, the enhanced process has the same scaling properties and it satisfies a Fernique type theorem, a support theorem and a large deviation principle in the same Hölder topologies as the classical Wiener process does. Moreover, the canonical rough paths of finite dimensional approximating Wiener processes converge to the enhanced Wiener process. Finally, a new criterion for the existence of the enhanced Wiener process is provided which is based on compact embeddings. This criterion is particularly handy when analyzing Kunita flows by means of rough paths analysis which is the topic of a forthcoming article. 相似文献
968.
利用Brown运动在H\"older 范数下关于$(r,p)$-容度的大偏差,证明了Brown运动增量在H\"older范数下关于$(r,p)$-容度的泛函极限定理. 相似文献
969.
970.