全文获取类型
收费全文 | 86252篇 |
免费 | 1173篇 |
国内免费 | 493篇 |
专业分类
电工技术 | 913篇 |
综合类 | 2568篇 |
化学工业 | 11762篇 |
金属工艺 | 4954篇 |
机械仪表 | 3201篇 |
建筑科学 | 2294篇 |
矿业工程 | 653篇 |
能源动力 | 1189篇 |
轻工业 | 3744篇 |
水利工程 | 1307篇 |
石油天然气 | 560篇 |
武器工业 | 26篇 |
无线电 | 9433篇 |
一般工业技术 | 16594篇 |
冶金工业 | 2850篇 |
原子能技术 | 287篇 |
自动化技术 | 25583篇 |
出版年
2023年 | 43篇 |
2022年 | 72篇 |
2021年 | 96篇 |
2020年 | 82篇 |
2019年 | 67篇 |
2018年 | 14503篇 |
2017年 | 13455篇 |
2016年 | 10028篇 |
2015年 | 713篇 |
2014年 | 366篇 |
2013年 | 313篇 |
2012年 | 3275篇 |
2011年 | 9556篇 |
2010年 | 8428篇 |
2009年 | 5685篇 |
2008年 | 6923篇 |
2007年 | 7876篇 |
2006年 | 256篇 |
2005年 | 1312篇 |
2004年 | 1214篇 |
2003年 | 1246篇 |
2002年 | 591篇 |
2001年 | 158篇 |
2000年 | 240篇 |
1999年 | 126篇 |
1998年 | 124篇 |
1997年 | 114篇 |
1996年 | 116篇 |
1995年 | 67篇 |
1994年 | 57篇 |
1993年 | 46篇 |
1992年 | 28篇 |
1991年 | 46篇 |
1990年 | 19篇 |
1988年 | 26篇 |
1969年 | 24篇 |
1968年 | 44篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 35篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A new patch-based texture synthesis method is presented in this paper. By the method, a set of patches that can be matched
with a sampled patch for growing textures effectively, called the matching compatibility between patches, is generated first
for each patch, and the set is further optimized by culling the patches that may cause synthesis conflicts. In this way, similarity
measurement calculation for selecting suitable patches in texture synthesis can be greatly saved, and synthesis conflicts
between neighbouring patches are substantially reduced. Furthermore, retrace computation is integrated in the synthesis process
to improve the texture quality. As a result, the new method can produce high quality textures as texture optimization, the
best method to date for producing good textures, and run in a time complexity linear to the size of the output texture. Experimental
results show that the new method can interactively generate a large texture in 1024 × 1024 pixels, which is very difficult
to achieve by existing methods.
Supported by the National Basic Research Program of China (Grant No. 2009CB320802), the National Natural Science Foundation
of China (Grant Nos. 60773026, 60833007), the National High-Tech Research & Development Program of China (Grant Nos. 2006AA01Z306,
2008AA01Z301), and the Research Grant of University of Macau 相似文献
992.
Based on local Taylor expansions on the complex plane, a method for fast locating all modes (FLAM) of spectral-domain Green’s
Functions in a planar layered medium is developed in this paper. SDP-FLAM, a combination of FLAM with the steepest descent
path algorithm (SDP), is employed to accurately evaluate the spatial-domain Green’s functions in a layered medium. According
to the theory of complex analysis, the relationship among the poles, branch points and Riemann sheets is also analyzed rigorously.
To inverse the Green’s functions from spectral to spatial domain, SDP-FLAM method and discrete complex image method (DCIM)
are applied to the non-near field region and the near filed region, respectively. The significant advantage of SDP-FLAM lies
in its capability of calculating Green’s functions in a layered medium of moderate thickness with loss or without loss. Some
numerical examples are presented to validate SDP-FLAM method.
Supported by the National Natural Science Foundation of China (Grant No. 60621002), and the State Key Development Program
for Basic Research of China (Grant No. 2009CB320200) 相似文献
993.
This paper presents a Lyapunov-based approach to design the boundary feedback control for an openchannel network composed
of a cascade of multi-reach canals, each described by a pair of Saint-Venant equations. The weighted sum of entropies of the
multi-reaches is adopted to construct the Lyapunov function. The time derivative of the Lyapunov function is expressed by
the water depth variations at the gate boundaries, based on which a class of boundary feedback controllers is presented to
guarantee the local asymptotic closed-loop stability. The advantage of this approach is that only the water level depths at
the gate boundaries are measured as the feedback.
Supported by the National Natural Science Foundation of China (Grant Nos. 60504026, 60674041), and the National High-Tech
Research & Development Program of China (Grant No. 2006AA04Z173) 相似文献
994.
In this paper, a multivariable direct adaptive controller using multiple models without minimum phase assumption is presented
to improve the transient response when the parameters of the system jump abruptly. The controller is composed of multiple
fixed controller models, a free-running adaptive controller model and a re-initialized adaptive controller model. The fixed
controller models are derived from the corresponding fixed system models directly. The adaptive controller models adopt the
direct adaptive algorithm to reduce the design calculation. At every instant, the optimal controller is chosen out according
to the switching index. The interaction of the system is viewed as the measured disturbance which is eliminated by the choice
of the weighing polynomial matrix. The global convergence is obtained. Finally, several simulation examples in a wind tunnel
experiment are given to show both effectiveness and practicality of the proposed method. The significance of the proposed
method is that it is applicable to a non-minimum phase system, adopting direct adaptive algorithm to overcome the singularity
problem during the matrix calculation and realizing decoupling control for a multivariable system.
Supported by the National Natural Science Foundation of China (Grant Nos. 60504010, 60864004), the National High-Tech Research
and Development Program of China (Grant No. 2008AA04Z129), the Key Project of Chinese Ministry of Education (Grant No. 208071),
and the Natural Science Foundation of Jiangxi Province (Grant No. 0611006) 相似文献
995.
This paper designs and analyzes switching fuzzy reduced-order observer and proves that the corresponding separation principle
does hold. A numerical simulation and comparison with smooth fuzzy full-order observer are given to assess switching fuzzy
reduced-order observer and the validity of the separation principles.
Supported by the National Laboratory of Space Intelligent Control and Open Foundation (Grant No. SIC07010202), and the National
Natural Science Foundation of China (Grant Nos. 60604010, 90716021, 60736023) 相似文献
996.
Fotis N. Koumboulis Nikolaos D. Kouvakas Paraskevas N. Paraskevopoulos 《中国科学F辑(英文版)》2009,52(7):1084-1094
In the present paper the problem of disturbance rejection of single input-single output neutral time delay systems with multiple
measurable disturbances is solved via dynamic controllers. In particular, the general form of the controller matrices is presented,
while the necessary and sufficient conditions for the controller to be realizable are offered. The proposed technique is applied
to a test case neutral time delay central heating system. In particular, the nonlinear model of the plant and its linearized
approximation are presented. Based on the linearized model, a two-stage controller is designed in order to regulate the room
temperature and the boiler effluent temperature. The performance of the closed loop system is investigated through computational
experiments. 相似文献
997.
How to compose existing web services automatically and to guarantee the correctness of the design(e.g. freeness of deadlock and unspecified reception,and temporal constraints) is an important and challenging problem in web services. Most existing approaches require a detailed specification of the desired behaviors of a composite service beforehand and then perform certain formal verification to guarantee the correctness of the design,which makes the composition process both complex and time-consuming. In th... 相似文献
998.
LiQiang Zhang ZhiFeng Guo ZhiZhong Kang LiXin Zhang XingMing Zhang Ling Yang 《中国科学F辑(英文版)》2009,52(9):1588-1597
Adaptive rendering large and complex spatial data has become an important research issue in a 3DGIS application. In order to transmit the data to the client efficiently,this paper proposes a node-layer data model to manage the 3D scene. Because the large spatial data and limited network bandwidth are the main bottlenecks of web-based 3DGIS,a client/server architecture including progressive transmission methods and multiresolution representations,together with the spatial index,are developed to improve the p... 相似文献
999.
1000.
Perfect forward secure identity-based authenticated key agreement protocol in the escrow mode 总被引:1,自引:0,他引:1
CHOO Kim-Kwang Raymond 《中国科学F辑(英文版)》2009,52(8):1358-1370
The majority of existing escrowable identity-based key agreement protocols only provide partial forward secrecy. Such protocols are, arguably, not suitable for many real-word applications, as the latter tends to require a stronger sense of forward secrecy—perfect forward secrecy. In this paper, we propose an efficient perfect forward-secure identity-based key agreement protocol in the escrow mode. We prove the security of our protocol in the random oracle model, assuming the intractability of the Gap Biline... 相似文献