首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4796篇
  免费   870篇
  国内免费   524篇
化学   1562篇
晶体学   47篇
力学   127篇
综合类   63篇
数学   699篇
物理学   897篇
无线电   2795篇
  2024年   12篇
  2023年   56篇
  2022年   100篇
  2021年   138篇
  2020年   146篇
  2019年   141篇
  2018年   133篇
  2017年   202篇
  2016年   230篇
  2015年   274篇
  2014年   389篇
  2013年   335篇
  2012年   377篇
  2011年   368篇
  2010年   290篇
  2009年   349篇
  2008年   400篇
  2007年   364篇
  2006年   349篇
  2005年   306篇
  2004年   249篇
  2003年   196篇
  2002年   121篇
  2001年   134篇
  2000年   112篇
  1999年   65篇
  1998年   61篇
  1997年   68篇
  1996年   49篇
  1995年   42篇
  1994年   21篇
  1993年   19篇
  1992年   20篇
  1991年   15篇
  1990年   10篇
  1989年   6篇
  1988年   9篇
  1987年   7篇
  1986年   4篇
  1985年   2篇
  1984年   12篇
  1983年   3篇
  1982年   2篇
  1981年   4篇
排序方式: 共有6190条查询结果,搜索用时 187 毫秒
101.
The Grover's a1gorithm was used for fau1t attack against the pub1ic key cryptography.A fixed phase rotation based Grover's a1gorithm was proposed,and the probabi1ity of success achieved 99.23% with 0.1π phase rotation.Combined with the fau1t attack further,ECC(e11iptic curve cryptography)vo1tage burr attack a1gorithm based on Grover a1gorithm with 0.1π phase rotation was proposed.Then a safety Kob1itz curve,K-163,pub1ished successfu11y attacked by NIST on binary domain in simu1ation and the success rate was 100%.The comp1exity of the attack great1y reduces on the exponentia1.It was a new effective way,except the Shor's a1gorithm,to attack pub1ic key cryptography by quantum computing,and it contributed to extend the attack ways to the other pub1ic key cryptography.  相似文献   
102.
王峥  毛钦曙  王钦玉 《信息技术》2012,(7):151-153,156
为了解决生产中短波天调配谐过程存在的劳动强度大,统计不够准确等问题,设计了一种检测仪。该检测仪以嵌入式技术为基础,利用短波电台所提供的遥控命令,实现短波天调自动配谐功能,并根据统计得到的配谐数据判断天调匹配性能是否合格。经生产验证,该测试仪在提高劳动效率的同时,还能减少人工统计数据可能带来的误差。  相似文献   
103.
《Comptes Rendus Chimie》2014,17(4):342-351
A systematic study of the design and characterization of silica-microemulsion templates is presented. The ternary phase diagrams in micro-heterogeneous systems, by using a non-ionic surfactant (Brij 30) and different silica precursors (MTEOS, TEOS, PTEOS), have been drawn. Based on Khalweit diagrams, the phase inversion temperature was estimated as close to 315 K, for both alchil (TEOS) and aril (PTEOS) types of alcoxides. By correlating the information obtained from phase diagrams at room temperature with that of size effects revealed by VIS absorption molecular probes (bromthymol blue dye), the phase inversion point, i.e. the transition point from water-in-oil to oil-in-water microemulsion, was also clearly established as corresponding to R  1. Besides technically attractive features such as a wide variety of inorganic and hybrid nanomaterials, high specific surface and highly efficient applicative properties of the final materials, the approach of silica-microemulsion-based templates can be seen as a route towards the Green Chemistry concept.  相似文献   
104.
In this paper we use fixed point and coincidence theorems due to Park [8] to give matching theorems concerning closed coverings of nonempty convex sets in a real topological vector space. Our new results extend previously given ones due to Ky Fan [2], [3], Shih [10], Shih and Tan [11], and Park [7].  相似文献   
105.
Jianwei Ben 《中国物理 B》2022,31(7):76104-076104
Introducing voids into AlN layer at a certain height using a simple method is meaningful but challenging. In this work, the AlN/sapphire template with AlN interlayer structure was designed and grown by metal-organic chemical vapor deposition. Then, the AlN template was annealed at 1700 ℃ for an hour to introduce the voids. It was found that voids were formed in the AlN layer after high-temperature annealing and they were mainly distributed around the AlN interlayer. Meanwhile, the dislocation density of the AlN template decreased from 5.26×109 cm-2 to 5.10×108 cm-2. This work provides a possible method to introduce voids into AlN layer at a designated height, which will benefit the design of AlN-based devices.  相似文献   
106.
Is it true that every matching in the n-dimensional hypercube can be extended to a Gray code? More than two decades have passed since Ruskey and Savage asked this question and the problem still remains open. A solution is known only in some special cases, including perfect matchings or matchings of linear size. This article shows that the answer to the Ruskey–Savage problem is affirmative for every matching of size at most . The proof is based on an inductive construction that extends balanced matchings in the completion of the hypercube by edges of into a Hamilton cycle of . On the other hand, we show that for every there is a balanced matching in of size that cannot be extended in this way.  相似文献   
107.
Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS2/MoO3 nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO3/MoS2 composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO3/MoS2 composites. According to Raman spectroscopy results, as-obtained defect-rich MoS2 is confirmed to be a metallic 1T-phase MoS2. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g−1 and up to 1720.6 mAh g−1 after 317 cycles under a current density of 0.2 A g−1). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g−1 at 2 A g−1 after 700 cycles and 584.8 mAh g−1 at 5 A g−1 after 800 cycles). Moreover, at a rate of 1 A g−1, the average specific capacity is maintained at 661 mAh g−1. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.  相似文献   
108.
Let M be a perfect matching in a graph. A subset S of M is said to be a forcing set of M, if M is the only perfect matching in the graph that contains S. The minimum size of a forcing set of M is called the forcing number of M. Pachter and Kim (1998) conjectured that the forcing number of every perfect matching in the n-dimensional hypercube is 2n?2, for all n2. This was revised by Riddle (2002), who conjectured that it is at least 2n?2, and proved it for all even n. We show that the revised conjecture holds for all n2. The proof is based on simple linear algebra.  相似文献   
109.
Kreweras conjectured that every perfect matching of a hypercube Qn for n2 can be extended to a hamiltonian cycle of Qn. Fink confirmed the conjecture to be true. It is more general to ask whether every perfect matching of Qn for n2 can be extended to two or more hamiltonian cycles of Qn. In this paper, we prove that every perfect matching of Qn for n4 can be extended to at least 22n?4 different hamiltonian cycles of Qn.  相似文献   
110.
Video object segmentation, aiming to segment the foreground objects given the annotation of the first frame, has been attracting increasing attentions. Many state-of-the-art approaches have achieved great performance by relying on online model updating or mask-propagation techniques. However, most online models require high computational cost due to model fine-tuning during inference. Most mask-propagation based models are faster but with relatively low performance due to failure to adapt to object appearance variation. In this paper, we are aiming to design a new model to make a good balance between speed and performance. We propose a model, called NPMCA-net, which directly localizes foreground objects based on mask-propagation and non-local technique by matching pixels in reference and target frames. Since we bring in information of both first and previous frames, our network is robust to large object appearance variation, and can better adapt to occlusions. Extensive experiments show that our approach can achieve a new state-of-the-art performance with a fast speed at the same time (86.5% IoU on DAVIS-2016 and 72.2% IoU on DAVIS-2017, with speed of 0.11s per frame) under the same level comparison. Source code is available at https://github.com/siyueyu/NPMCA-net.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号