全文获取类型
收费全文 | 28259篇 |
免费 | 3462篇 |
国内免费 | 2838篇 |
专业分类
化学 | 2646篇 |
晶体学 | 44篇 |
力学 | 2832篇 |
综合类 | 709篇 |
数学 | 20670篇 |
物理学 | 7658篇 |
出版年
2024年 | 39篇 |
2023年 | 222篇 |
2022年 | 388篇 |
2021年 | 474篇 |
2020年 | 607篇 |
2019年 | 624篇 |
2018年 | 673篇 |
2017年 | 851篇 |
2016年 | 952篇 |
2015年 | 681篇 |
2014年 | 1352篇 |
2013年 | 1978篇 |
2012年 | 1416篇 |
2011年 | 1713篇 |
2010年 | 1563篇 |
2009年 | 1881篇 |
2008年 | 1955篇 |
2007年 | 2017篇 |
2006年 | 1824篇 |
2005年 | 1741篇 |
2004年 | 1451篇 |
2003年 | 1341篇 |
2002年 | 1165篇 |
2001年 | 1028篇 |
2000年 | 982篇 |
1999年 | 833篇 |
1998年 | 738篇 |
1997年 | 681篇 |
1996年 | 509篇 |
1995年 | 427篇 |
1994年 | 349篇 |
1993年 | 286篇 |
1992年 | 225篇 |
1991年 | 172篇 |
1990年 | 193篇 |
1989年 | 121篇 |
1988年 | 120篇 |
1987年 | 106篇 |
1986年 | 97篇 |
1985年 | 115篇 |
1984年 | 98篇 |
1983年 | 59篇 |
1982年 | 90篇 |
1981年 | 78篇 |
1980年 | 56篇 |
1979年 | 50篇 |
1978年 | 47篇 |
1977年 | 42篇 |
1976年 | 37篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 718 毫秒
1.
2.
Prof. Dr. Peter Hess 《Chemphyschem》2022,23(6):e202100880
In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials. 相似文献
3.
4.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
6.
7.
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.