全文获取类型
收费全文 | 32396篇 |
免费 | 4904篇 |
国内免费 | 3343篇 |
专业分类
化学 | 4886篇 |
晶体学 | 200篇 |
力学 | 3063篇 |
综合类 | 676篇 |
数学 | 16531篇 |
物理学 | 15287篇 |
出版年
2024年 | 39篇 |
2023年 | 287篇 |
2022年 | 493篇 |
2021年 | 665篇 |
2020年 | 780篇 |
2019年 | 719篇 |
2018年 | 741篇 |
2017年 | 987篇 |
2016年 | 1119篇 |
2015年 | 927篇 |
2014年 | 1684篇 |
2013年 | 2213篇 |
2012年 | 1832篇 |
2011年 | 2111篇 |
2010年 | 1927篇 |
2009年 | 2217篇 |
2008年 | 2206篇 |
2007年 | 2247篇 |
2006年 | 2106篇 |
2005年 | 1969篇 |
2004年 | 1742篇 |
2003年 | 1570篇 |
2002年 | 1355篇 |
2001年 | 1204篇 |
2000年 | 1128篇 |
1999年 | 977篇 |
1998年 | 878篇 |
1997年 | 768篇 |
1996年 | 585篇 |
1995年 | 461篇 |
1994年 | 392篇 |
1993年 | 291篇 |
1992年 | 247篇 |
1991年 | 216篇 |
1990年 | 220篇 |
1989年 | 181篇 |
1988年 | 147篇 |
1987年 | 122篇 |
1986年 | 122篇 |
1985年 | 123篇 |
1984年 | 94篇 |
1983年 | 60篇 |
1982年 | 88篇 |
1981年 | 79篇 |
1980年 | 55篇 |
1979年 | 47篇 |
1978年 | 46篇 |
1977年 | 36篇 |
1976年 | 37篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
1.
2.
3.
5.
6.
7.
G. Peruginelli 《代数通讯》2018,46(11):4724-4738
We classify the maximal subrings of the ring of n×n matrices over a finite field, and show that these subrings may be divided into three types. We also describe all of the maximal subrings of a finite semisimple ring, and categorize them into two classes. As an application of these results, we calculate the covering number of a finite semisimple ring. 相似文献
8.
《Wave Motion》2018
Large cable net structures have been widely applied in aerospace engineering due to the feature of light-weight, high packaging efficiency, and high thermal stability. Structural vibrations induced by a variety of disturbances are inevitable in the space environment, resulting in the requirement of effective vibration control strategies for large cable net structures. Since the large cable net structures have many closely spaced vibrational modes in the range of low frequencies, traditional modal based control may cause modal truncation and spillover problems. In this paper, a wave-based boundary control strategy is adopted and its effectiveness to control the vibration of cable net structures is investigated, by transfer function analysis and numerical methods. It is found that the structural vibration can be absolutely resisted by applying the wave-based boundary controllers onto all the exterior nodes, when disturbances come from the external boundaries of the cable net. Our results in this paper can provide a theoretical basis for the vibration control of large cable net structures. 相似文献
9.
Multi-sensor data fusion is an evolving technology whereby data from multiple sensor inputs are processed and combined. The data derived from multiple sensors can, however, be uncertain, imperfect, and conflicting. The present study is undertaken to help contribute to the continuous search for viable approaches to overcome the problems associated with data conflict and imperfection. Sensor readings, represented by belief functions, have to be fused according to their corresponding weights. Previous studies have often estimated the weights of sensor readings based on a single criterion. Mono-criteria approaches for the assessment of sensor reading weights are, however, often unreliable and inadequate for the reflection of reality. Accordingly, this work opts for the use of a multi-criteria decision aid. A modified Analytical Hierarchy Process (AHP) that incorporates several criteria is proposed to determine the weights of a sensor reading set. The approach relies on the automation of pairwise comparisons to eliminate subjectivity and reduce inconsistency. It assesses the weight of each sensor reading, and fuses the weighed readings obtained using a modified average combination rule. The efficiency of this approach is evaluated in a target recognition context. Several tests, sensitivity analysis, and comparisons with other approaches available in the literature are described. 相似文献
10.
Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size. 相似文献