全文获取类型
收费全文 | 25883篇 |
免费 | 2771篇 |
国内免费 | 671篇 |
专业分类
化学 | 5042篇 |
晶体学 | 20篇 |
力学 | 948篇 |
综合类 | 206篇 |
数学 | 7807篇 |
物理学 | 6553篇 |
无线电 | 8749篇 |
出版年
2024年 | 43篇 |
2023年 | 313篇 |
2022年 | 499篇 |
2021年 | 842篇 |
2020年 | 780篇 |
2019年 | 610篇 |
2018年 | 478篇 |
2017年 | 679篇 |
2016年 | 1027篇 |
2015年 | 897篇 |
2014年 | 1569篇 |
2013年 | 1846篇 |
2012年 | 1414篇 |
2011年 | 1493篇 |
2010年 | 1175篇 |
2009年 | 1476篇 |
2008年 | 1714篇 |
2007年 | 1760篇 |
2006年 | 1447篇 |
2005年 | 1196篇 |
2004年 | 981篇 |
2003年 | 999篇 |
2002年 | 914篇 |
2001年 | 660篇 |
2000年 | 659篇 |
1999年 | 522篇 |
1998年 | 484篇 |
1997年 | 349篇 |
1996年 | 308篇 |
1995年 | 285篇 |
1994年 | 260篇 |
1993年 | 195篇 |
1992年 | 173篇 |
1991年 | 127篇 |
1990年 | 112篇 |
1989年 | 127篇 |
1988年 | 122篇 |
1987年 | 84篇 |
1986年 | 77篇 |
1985年 | 123篇 |
1984年 | 93篇 |
1983年 | 38篇 |
1982年 | 58篇 |
1981年 | 53篇 |
1980年 | 53篇 |
1979年 | 43篇 |
1978年 | 40篇 |
1977年 | 38篇 |
1976年 | 36篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In a typical embedded CPU, large on-chip storage is critical to meet high performance requirements. However, the fast increasing size of the on-chip storage based on traditional SRAM cells makes the area cost and energy consumption unsustainable for future embedded applications. Replacing SRAM with DRAM on the CPU’s chip is generally considered not worthwhile because DRAM is not compatible with the common CMOS logic and requires additional processing steps beyond what is required for CMOS. However a special DRAM technology, Gain-Cell embedded-DRAM (GC-eDRAM) [1], [2], [3] is logic compatible and retains some of the good properties of DRAM (small and low power). In this paper we evaluate the performance of a novel hybrid cache memory where the data array, generally populated with SRAM cells, is replaced with GC-eDRAM cells while the tag array continues to use SRAM cells. Our evaluation of this cache demonstrates that, compared to the conventional SRAM-based designs, our novel architecture exhibits comparable performance with less energy consumption and smaller silicon area, enabling the sustainable on-chip storage scaling for future embedded CPUs. 相似文献
2.
如何在互联网时代打造一个信息化的管理模式,已经成为广大学校图书管理发展过程中亟待处理的问题。文章就互联网时代下的高职图书管理信息化建设进行了详细探讨,以期能够给广大同仁提供一些借鉴参考,共同为图书管理工作的现代化改革和发展贡献力量。 相似文献
3.
文章首先对智能化电子信息技术进行了深入的研究,而后分析了该技术在应用过程中出现的问题,最后结合该技术的相关特点给出了相应的问题解决措施,希望能够对智能化电子信息技术的发展提供帮助。 相似文献
4.
以智能反射面(intelligent reflecting surface,IRS)辅助的无线携能通信(simultaneous wireless information and power transfer,SWIPT)系统为背景,研究了该系统中基于能效优先的多天线发送端有源波束成形与IRS无源波束成形联合设计与优化方法。以最大化接收端的最小能效为优化目标,构造在发送端功率、接收端能量阈值、IRS相移等多约束下的非线性优化问题,用交替方向乘子法(alternating direction method of multipliers,ADMM)求解。采用Dinkelbach算法转化目标函数,通过奇异值分解(singular value decomposition,SVD)和半定松弛(semi-definite relaxation,SDR)得到发送端有源波束成形向量。采用SDR得到IRS相移矩阵与反射波束成形向量。结果表明,该系统显著降低了系统能量收集(energy harvesting,EH)接收端的能量阈值。当系统总电路功耗为?15 dBm时,所提方案的用户能效为300 KB/J。当IRS反射阵源数与发送天线数均为最大值时,系统可达最大能效。 相似文献
5.
Claudius Gros 《Entropy (Basel, Switzerland)》2021,23(2)
Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed. 相似文献
6.
7.
In 1976 S. Hawking claimed that “Because part of the information about the state of the system is lost down the hole, the final situation is represented by a density matrix rather than a pure quantum state”. 1 This was the starting point of the popular “black hole (BH) information paradox”. 相似文献
8.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate
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)
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
9.
本文对运营商信息安全集中管控架构演进和信息安全管控策略面临的问题进行了深入分析,提出了信息安全集中管控架构的演进方向建议及对信息安全监控策略工作优化的若干意见。 相似文献
10.