全文获取类型
收费全文 | 566篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 131篇 |
金属工艺 | 14篇 |
机械仪表 | 21篇 |
建筑科学 | 24篇 |
矿业工程 | 4篇 |
能源动力 | 80篇 |
轻工业 | 78篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 38篇 |
一般工业技术 | 93篇 |
冶金工业 | 18篇 |
原子能技术 | 11篇 |
自动化技术 | 77篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 21篇 |
2019年 | 14篇 |
2018年 | 34篇 |
2017年 | 22篇 |
2016年 | 27篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 40篇 |
2010年 | 52篇 |
2009年 | 54篇 |
2008年 | 37篇 |
2007年 | 33篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 15篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有596条查询结果,搜索用时 15 毫秒
1.
2.
3.
Reset controllers are linear controllers that reset some of their states to zero when their input is zero. We are interested in their feedback connection with linear plants, and in this paper we establish fundamental closed-loop properties including stability and asymptotic tracking. This paper considers more general reset structures than previously considered, allowing for higher-order controllers and partial-state resetting. It gives a testable necessary and sufficient condition for quadratic stability and links it to both uniform bounded-input bounded-state stability and steady-state performance. Unlike previous related research, which includes the study of impulsive differential equations, our stability results require no assumptions on the evolution of reset times. 相似文献
4.
Orhan Gazi A. Ozgur Yilmaz 《Communications Letters, IEEE》2007,11(2):173-175
Decoding delay is an important consideration for the use of turbo codes in practical applications. We propose a new structure for turbo codes which is very suitable for parallel decoding. It is shown by union bound analysis and simulation results that the proposed system performance is comparable to that of the classical turbo codes 相似文献
5.
Using genetic algorithm for the optimization of seismic behavior of steel planar frames with semi-rigid connections 总被引:1,自引:0,他引:1
Asghar?Vatani?OskoueiEmail author Sahand?Sarioletlagh?Fard Orhan?Aksogan 《Structural and Multidisciplinary Optimization》2012,45(2):287-302
Beam-column connections have a significant role in the results of the analysis and the design of steel frames. In this paper,
a genetic algorithm has been used for the non-linear analysis and design of steel frames. For minimizing the weight of frames,
while satisfying the applied constraints and restraints such as the limits of normal and combined stresses, criteria such
as target displacement(s) and the number and locations of plastic hinges were used. To analyze and design the frame elements,
I and box-shaped standard sections were used for beams and columns, respectively. Finally, some clues for finding optimizing
semi-rigid connection stiffness values for beam-to-column connections have been obtained. The degrees of these rigidities
are obtained by a genetic algorithm during the procedure of optimization in order to reach a frame with the minimum weight.
SAP2000 structural analysis program was used to perform modal analysis and linear and non-linear static solutions as well
as the design of the elements. A MATLAB program was written for the process of optimization. The procedure of optimization
was based on a weight minimization carried out for 9 steel frames. Thus, the optimum connection stiffness could be obtained
for minimizing the weight of the structure. The results show that the non-linear analysis gives less weight for short period
frames with semi-rigid connections compared to those of linear ones. However, by increasing the periods of frames, much less
weights are obtained in the case of non-linear analysis with semi-rigid connections. 相似文献
6.
A controlled release profile of salicylic acid (SA) for transdermal administration has been developed. Poly (vinyl alcohol) (PVA) and Poly(vinyl alcohol)/Poly(vinyl pyrrolidone) (PVP) blended preparations were used to prepare the membranes by solvent‐casting technique. The release of the drug from the membranes was evaluated at in vitro conditions. The effects of PVA/PVP (v/v) ratio, pH, SA concentration and temperature were investigated. 60/40 (v/v) PVA/PVP ratio was found to be the best ratio for the SA release. Increase in pH and temperature was observed to increase the transport of SA. Instead of blending PVA with PVP, N‐Vinyl‐2‐pyrrolidone (VP) was grafted onto the PVA and the delivery performance for SA was compared with that of the blended PVA/PVP membranes. Grafted membranes gave higher transport percentages than the blended membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1244–1253, 2006 相似文献
7.
Polarization and impedance measurements were performed on steel in deaerated 5% HCl solution with and without Schiff base additives within the concentration range 1 × 10−4–5 × 10−3 mol/dm3. The Schiff base compounds used were salicylaldimine, R, N-(2-chlorophenyl)salicyaldimine, 2Cl-R, N-(3-chlorophenyl)salicyaldimine, 3Cl-R, and N-(4-chlorophenyl)salicyaldimine, 4Cl-R. It was found that when the concentration of the inhibitors were increased the inhibitor efficiencies, η, also increased with increasing surface coverage. The results indicated that the ortho-substituted (2Cl-R) compound had the highest inhibition efficiency. All the Schiff base additives studied obeyed the Langmuir isotherm. 相似文献
8.
We present a new method for rapidly computing shadows from semi‐transparent objects like hair. Our deep opacity maps method extends the concept of opacity shadow maps by using a depth map to obtain a per pixel distribution of opacity layers. This approach eliminates the layering artifacts of opacity shadow maps and requires far fewer layers to achieve high quality shadow computation. Furthermore, it is faster than the density clustering technique, and produces less noise with comparable shadow quality. We provide qualitative comparisons to these previous methods and give performance results. Our algorithm is easy to implement, faster, and more memory efficient, enabling us to generate high quality hair shadows in real‐time using graphics hardware on a standard PC. 相似文献
9.
Yunus Ziya Arslan Yuksel Hacioglu Nurkan Yagiz 《Journal of Intelligent and Robotic Systems》2008,52(1):121-138
In order to improve the life quality of amputees, providing approximate manipulation ability of a human hand to that of a
prosthetic hand is considered by many researchers. In this study, a biomechanical model of the index finger of the human hand
is developed based on the human anatomy. Since the activation of finger bones are carried out by tendons, a tendon configuration
of the index finger is introduced and used in the model to imitate the human hand characteristics and functionality. Then,
fuzzy sliding mode control where the slope of the sliding surface is tuned by a fuzzy logic unit is proposed and applied to
have the finger model to follow a certain trajectory. The trajectory of the finger model, which mimics the motion characteristics
of the human hand, is pre-determined from the camera images of a real hand during closing and opening motion. Also, in order
to check the robust behaviour of the controller, an unexpected joint friction is induced on the prosthetic finger on its way.
Finally, the resultant prosthetic finger motion and the tendon forces produced are given and results are discussed. 相似文献
10.
In unstructured peer-to-peer (P2P) networks, the overlay topology (or connectivity graph) among peers is a crucial component in addition to the peer/data organization and search. Topological characteristics have profound impact on the efficiency of a search on such unstructured P2P networks, as well as other networks. A key limitation of scale-free (power-law) topologies is the high load (i.e., high degree) on a very few number of hub nodes. In a typical unstructured P2P network, peers are not willing to maintain high degrees/loads as they may not want to store a large number of entries for construction of the overlay topology. Therefore, to achieve fairness and practicality among all peers, hard cutoffs on the number of entries are imposed by the individual peers, which limits scale-freeness of the overall topology, hence limited scale-free networks. Thus, it is expected that the efficiency of the flooding search reduces as the size of the hard cutoff does. We investigate the construction of scale-free topologies with hard cutoffs (i.e., there are not any major hubs) and the effect of these hard cutoffs on the search efficiency. Interestingly, we observe that the efficiency of normalized flooding and random walk search algorithms increases as the hard cutoff decreases. 相似文献