全文获取类型
收费全文 | 17059篇 |
免费 | 2877篇 |
国内免费 | 2225篇 |
专业分类
电工技术 | 1226篇 |
综合类 | 2223篇 |
化学工业 | 607篇 |
金属工艺 | 173篇 |
机械仪表 | 897篇 |
建筑科学 | 585篇 |
矿业工程 | 173篇 |
能源动力 | 211篇 |
轻工业 | 297篇 |
水利工程 | 323篇 |
石油天然气 | 288篇 |
武器工业 | 277篇 |
无线电 | 2576篇 |
一般工业技术 | 1945篇 |
冶金工业 | 413篇 |
原子能技术 | 94篇 |
自动化技术 | 9853篇 |
出版年
2024年 | 99篇 |
2023年 | 332篇 |
2022年 | 593篇 |
2021年 | 644篇 |
2020年 | 750篇 |
2019年 | 666篇 |
2018年 | 643篇 |
2017年 | 806篇 |
2016年 | 858篇 |
2015年 | 949篇 |
2014年 | 1185篇 |
2013年 | 1341篇 |
2012年 | 1361篇 |
2011年 | 1397篇 |
2010年 | 1063篇 |
2009年 | 1132篇 |
2008年 | 1214篇 |
2007年 | 1182篇 |
2006年 | 1007篇 |
2005年 | 821篇 |
2004年 | 669篇 |
2003年 | 534篇 |
2002年 | 464篇 |
2001年 | 402篇 |
2000年 | 360篇 |
1999年 | 235篇 |
1998年 | 192篇 |
1997年 | 184篇 |
1996年 | 133篇 |
1995年 | 158篇 |
1994年 | 112篇 |
1993年 | 91篇 |
1992年 | 88篇 |
1991年 | 72篇 |
1990年 | 69篇 |
1989年 | 68篇 |
1988年 | 55篇 |
1987年 | 25篇 |
1986年 | 28篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
11.
带关键字搜索的公钥加密(PEKS)是一种有用的加密原语,它允许用户将在加密数据上搜索的功能委托给不可信的第三方服务器,而不影响原始数据的安全性和隐私性。但是,由于缺乏对于数据的加密以及解密能力,PEKS方案不能单独进行使用,必须与标准的公钥加密方案(PKE)相结合。因此,Baek等人在2006年引入了一种新的加密原语,称为结合PKE和PEKS的加密方案(PKE+PEKS),它同时提供了PKE和PEKS的功能。目前,已有文献提出了几种PKE+PEKS方案。然而,他们都没有考虑关键字猜测攻击的问题。本文提出一个新的高效且能够抵抗关键字猜测攻击的PKE+PEKS方案,与已有方案相比,该方案在性能上有很大的提升,并且在生成关键字和数据密文时,不需要使用双线性对,极大地降低了计算和存储成本。安全性分析表明,本文中所提出的方案能够满足密文隐私安全性、陷门不可区分性和抗关键字猜测攻击的安全性。效率分析表明,本分提出的方案更加高效。 相似文献
12.
Semantic search is gradually establishing itself as the next generation search paradigm, which meets better a wider range of information needs, as compared to traditional full-text search. At the same time, however, expanding search towards document structure and external, formal knowledge sources (e.g. LOD resources) remains challenging, especially with respect to efficiency, usability, and scalability.This paper introduces Mímir—an open-source framework for integrated semantic search over text, document structure, linguistic annotations, and formal semantic knowledge. Mímir supports complex structural queries, as well as basic keyword search.Exploratory search and sense-making are supported through information visualisation interfaces, such as co-occurrence matrices and term clouds. There is also an interactive retrieval interface, where users can save, refine, and analyse the results of a semantic search over time. The more well-studied precision-oriented information seeking searches are also well supported.The generic and extensible nature of the Mímir platform is demonstrated through three different, real-world applications, one of which required indexing and search over tens of millions of documents and fifty to hundred times as many semantic annotations. Scaling up to over 150 million documents was also accomplished, via index federation and cloud-based deployment. 相似文献
13.
Online configuration of large-scale systems such as networks requires parameter optimization within a limited amount of time, especially when configuration is needed as a response to recover from a failure in the system. To quickly configure such systems in an online manner, we propose a Probabilistic Trans-Algorithmic Search (PTAS) framework which leverages multiple optimization search algorithms in an iterative manner. PTAS applies a search algorithm to determine how to best distribute available experiment budget among multiple optimization search algorithms. It allocates an experiment budget to each available search algorithm and observes its performance on the system-at-hand. PTAS then probabilistically reallocates the experiment budget for the next round proportional to each algorithm’s performance relative to the rest of the algorithms. This “roulette wheel” approach probabilistically favors the more successful algorithm in the next round. Following each round, the PTAS framework “transfers” the best result(s) among the individual algorithms, making our framework a trans-algorithmic one. PTAS thus aims to systematize how to “search for the best search” and hybridize a set of search algorithms to attain a better search. We use three individual search algorithms, i.e., Recursive Random Search (RRS) (Ye and Kalyanaraman, 2004), Simulated Annealing (SA) (Laarhoven and Aarts, 1987), and Genetic Algorithm (GA) (Goldberg, 1989), and compare PTAS against the performance of RRS, GA, and SA. We show the performance of PTAS on well-known benchmark objective functions including scenarios where the objective function changes in the middle of the optimization process. To illustrate applicability of our framework to automated network management, we apply PTAS on the problem of optimizing link weights of an intra-domain routing protocol on three different topologies obtained from the Rocketfuel dataset. We also apply PTAS on the problem of optimizing aggregate throughput of a wireless ad hoc network by tuning datarates of traffic sources. Our experiments show that PTAS successfully picks the best performing algorithm, RRS or GA, and allocates the time wisely. Further, our results show that PTAS’ performance is not transient and steadily improves as more time is available for search. 相似文献
14.
Greg A. Breed Paul M. Severns Andrew M. Edwards 《Journal of the Royal Society Interface》2015,12(103)
Lévy flights have gained prominence for analysis of animal movement. In a Lévy flight, step-lengths are drawn from a heavy-tailed distribution such as a power law (PL), and a large number of empirical demonstrations have been published. Others, however, have suggested that animal movement is ill fit by PL distributions or contend a state-switching process better explains apparent Lévy flight movement patterns. We used a mix of direct behavioural observations and GPS tracking to understand step-length patterns in females of two related butterflies. We initially found movement in one species (Euphydryas editha taylori) was best fit by a bounded PL, evidence of a Lévy flight, while the other (Euphydryas phaeton) was best fit by an exponential distribution. Subsequent analyses introduced additional candidate models and used behavioural observations to sort steps based on intraspecific interactions (interactions were rare in E. phaeton but common in E. e. taylori). These analyses showed a mixed-exponential is favoured over the bounded PL for E. e. taylori and that when step-lengths were sorted into states based on the influence of harassing conspecific males, both states were best fit by simple exponential distributions. The direct behavioural observations allowed us to infer the underlying behavioural mechanism is a state-switching process driven by intraspecific interactions rather than a Lévy flight. 相似文献
15.
Neural Machine Translation (NMT) is an end-to-end learning approach for
automated translation, overcoming the weaknesses of conventional phrase-based translation
systems. Although NMT based systems have gained their popularity in commercial
translation applications, there is still plenty of room for improvement. Being the most
popular search algorithm in NMT, beam search is vital to the translation result. However,
traditional beam search can produce duplicate or missing translation due to its target
sequence selection strategy. Aiming to alleviate this problem, this paper proposed neural
machine translation improvements based on a novel beam search evaluation function. And
we use reinforcement learning to train a translation evaluation system to select better
candidate words for generating translations. In the experiments, we conducted extensive
experiments to evaluate our methods. CASIA corpus and the 1,000,000 pairs of bilingual
corpora of NiuTrans are used in our experiments. The experiment results prove that the
proposed methods can effectively improve the English to Chinese translation quality. 相似文献
16.
1-read/1-write (1R1W) register file (RF) is a popular memory configuration in modern feature rich SoCs requiring significant amount of embedded memory. A memory compiler is constructed using the 8T RF bitcell spanning a range of instances from 32 b to 72 Kb. An 8T low-leakage bitcell of 0.106 μm2 is used in a 14 nm FinFET technology with a 70 nm contacted gate pitch for high-density (HD) two-port (TP) RF memory compiler which achieves 5.66 Mb/mm2 array density for a 72 Kb array which is the highest reported density in 14 nm FinFET technology. The density improvement is achieved by using techniques such as leaf-cell optimization (eliminating transistors), better architectural planning, top level connectivity through leaf-cell abutment and minimizing the number of unique leaf-cells. These techniques are fully compatible with memory compiler usage over the required span. Leakage power is minimized by using power-switches without degrading the density mentioned above. Self-induced supply voltage collapse technique is applied for write and a four stack static keeper is used for read Vmin improvement. Fabricated test chips using 14 nm process have demonstrated 2.33 GHz performance at 1.1 V/25 °C operation. Overall Vmin of 550 mV is achieved with this design at 25 °C. The inbuilt power-switch improves leakage power by 12x in simulation. Approximately 8% die area of a leading 14 nm SoC in commercialization is occupied by these compiled RF instances. 相似文献
17.
18.
19.
Efficient multicast search under delay and bandwidth constraints 总被引:1,自引:0,他引:1
The issue of a multicast search for a group of users is discussed in this study. Given the condition that the search is over
only after all the users in the group are found, this problem is called the Conference Call Search (CCS) problem. The goal
is to design efficient CCS strategies under delay and bandwidth constraints. While the problem of tracking a single user has
been addressed by many studies, to the best of our knowledge, this study is one of the first attempts to reduce the search
cost for multiple users. Moreover, as oppose to the single user tracking, for which one can always reduce the expected search
delay by increasing the expected search cost, for a multicast search the dependency between the delay and the search cost
is more complicated, as demonstrated in this study. We identify the key factors affecting the search efficiency, and the dependency
between them and the search delay. Our analysis shows that under tight bandwidth constraints, the CCS problem is NP-hard.
We therefore propose a search method that is not optimal, but has a low computational complexity. In addition, the proposed
strategy yields a low search delay as well as a low search cost. The performance of the proposed search strategy is superior
to the implementation of an optimal single user search on a group of users.
Amotz Bar-Noy received the B.Sc. degree in 1981 in Mathematics and Computer Science and the Ph.D. degree in 1987 in Computer Science, both
from the Hebrew University, Israel. From October 1987 to September 1989 he was a post-doc fellow in Stanford University, California.
From October 1989 to August 1996 he was a Research Staff Member with IBM T. J. Watson Research Center, New York. From February
1995 to September 2001 he was an associate Professor with the Electrical Engineering-Systems department of Tel Aviv University,
Israel. From September 1999 to December 2001 he was with AT research labs in New Jersey. Since February 2002 he is a Professor
with the Computer and Information Science Department of Brooklyn College - CUNY, Brooklyn New York.
Zohar Naor received the Ph.D. degree in Computer Science from Tel Aviv University, Tel Aviv, Israel, in 2000. Since 2003 he is with
the University of Haifa, Israel. His areas of interests include wireless networks, resource management of computer networks,
mobility, search strategies, and multiple access protocols. 相似文献
20.
随机减量技术中周期激励的影响及消除方法 总被引:3,自引:2,他引:1
本文针对机械系统中通常存在确定性周期激励的事实 ,论证了周期干扰成分的存在对提取的随机减量特征信号的影响 ,基于数字滤波技术提出了一种从周期干扰环境中提取随机减量特征信号的简便方法。在回转机械稳定性监测中的应用实例表明本文提出的方法是有效的。 相似文献