全文获取类型
收费全文 | 34339篇 |
免费 | 3443篇 |
国内免费 | 2378篇 |
专业分类
化学 | 3549篇 |
晶体学 | 94篇 |
力学 | 1787篇 |
综合类 | 527篇 |
数学 | 19197篇 |
物理学 | 6665篇 |
无线电 | 8341篇 |
出版年
2024年 | 63篇 |
2023年 | 327篇 |
2022年 | 629篇 |
2021年 | 806篇 |
2020年 | 857篇 |
2019年 | 784篇 |
2018年 | 759篇 |
2017年 | 920篇 |
2016年 | 961篇 |
2015年 | 869篇 |
2014年 | 1630篇 |
2013年 | 2040篇 |
2012年 | 1758篇 |
2011年 | 2204篇 |
2010年 | 1928篇 |
2009年 | 2333篇 |
2008年 | 2262篇 |
2007年 | 2377篇 |
2006年 | 2172篇 |
2005年 | 1893篇 |
2004年 | 1501篇 |
2003年 | 1392篇 |
2002年 | 1138篇 |
2001年 | 1010篇 |
2000年 | 908篇 |
1999年 | 847篇 |
1998年 | 752篇 |
1997年 | 672篇 |
1996年 | 531篇 |
1995年 | 475篇 |
1994年 | 402篇 |
1993年 | 345篇 |
1992年 | 265篇 |
1991年 | 211篇 |
1990年 | 303篇 |
1989年 | 279篇 |
1988年 | 181篇 |
1987年 | 172篇 |
1986年 | 186篇 |
1985年 | 194篇 |
1984年 | 145篇 |
1983年 | 84篇 |
1982年 | 98篇 |
1981年 | 90篇 |
1980年 | 70篇 |
1979年 | 61篇 |
1978年 | 58篇 |
1977年 | 55篇 |
1976年 | 48篇 |
1973年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
5G系统将移动通信服务从移动电话、移动宽带和大规模机器通信扩展到新的应用领域,即所谓对通信服务有特殊要求的垂直领域。对使能未来工厂的5G能力进行了全面的分析总结,包括弹性网络架构、灵活频谱、超可靠低时延通信、时间敏感网络、安全和定位,而弹性网络架构又包括对网络切片、非公共网络、5G局域网和边缘计算的支持。希望从广度到深度,对相关的理论及技术应用做透彻、全面的梳理,对其挑战做清晰的总结,从而为相关研究和工程技术人员提供借鉴。 相似文献
2.
4.
5.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual. 相似文献
6.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
7.
《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
8.
We report a simple processing method to simultaneously improve the efficiency and stability of organic solar cells (OSCs). Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxy-thiophene (PEDOT:PSS), widely used as hole transport layer (HTL) in OSCs, tends to accelerate the degradation of devices because of its hygroscopic and acidic properties. In this regard, we have modified PEDOT:PSS to reduce its hygroscopic and acidic properties through a condensation reaction between PEDOT:PSS and poly(ethylene glycol) methyl ether (PEGME) in order to improve the efficiency and stability of OSCs. As a result, the power conversion efficiency (PCE) increased by 21%, from 2.57% up to 3.11%. A better energy level alignment by the reduced work function of the modified PEDOT:PSS with a highest occupied molecular orbital (HOMO) level of poly(3-hexylthiophene-2,5-diyl) (P3HT) is considered the origin of the improved the efficiency. The half-life of OSCs with PEDOT:PSS modified with PEGME buffer layer also increased up to 3.5 times compared to that of devices with pristine PEDOT:PSS buffer layer. 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.