全文获取类型
收费全文 | 686篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 191篇 |
金属工艺 | 15篇 |
机械仪表 | 21篇 |
建筑科学 | 11篇 |
能源动力 | 30篇 |
轻工业 | 67篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 85篇 |
一般工业技术 | 158篇 |
冶金工业 | 31篇 |
原子能技术 | 3篇 |
自动化技术 | 101篇 |
出版年
2024年 | 2篇 |
2023年 | 20篇 |
2022年 | 19篇 |
2021年 | 43篇 |
2020年 | 47篇 |
2019年 | 24篇 |
2018年 | 33篇 |
2017年 | 32篇 |
2016年 | 31篇 |
2015年 | 23篇 |
2014年 | 50篇 |
2013年 | 57篇 |
2012年 | 28篇 |
2011年 | 51篇 |
2010年 | 38篇 |
2009年 | 27篇 |
2008年 | 19篇 |
2007年 | 22篇 |
2006年 | 20篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 19篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有724条查询结果,搜索用时 9 毫秒
81.
Sudip Misra P. Venkata Krishna Kiran Isaac Abraham 《Wireless Personal Communications》2011,56(1):55-72
Providing effective medium access for wireless networks is a challenging task. Most of the existing protocols of IEEE 802.11
Medium Access Control (MAC) work towards the goal of achieving effective channel access by developing various backoff procedures.
In this paper, we make an attempt to develop a new medium access protocol named Learning Automata (LA) based Wireless Channel
Reservation (LAWCR). We use an LA approach to implement reservation for channel access for single hop wireless networks. Also,
sequence procedure is used to improve the reservation mechanism. The performance of the proposed LAWCR scheme show significant
improvements over the legacy DCF protocol with respect to important criteria such as the average time spent in the buffer
and the throughput. 相似文献
82.
Kiran Mariam Wang Cong Papadimitriou George Mandal Anirban Deelman Ewa 《Machine Learning》2020,109(5):1127-1143
Machine Learning - Large-scale scientific workflows rely heavily on high-performance file transfers. These transfers require strict quality parameters such as guaranteed bandwidth, no packet loss... 相似文献
83.
The thermal decomposition of poly(butene-1 sulfone), poly(pentene-1 sulfone), poly(hexene-1 sulfone), poly(styrene sulfone), and polystyrene was investigated in helium at a heating rate of 20°C/min using an experimental system which consists of a programmable pyrolyzer, a thermal conductivity detector, a mass chromatograph, and a vapor-phase infrared spectrophotometer. Poly(butene-1 sulfone), poly(penetene-1 sulfone), and poly(hexene-1 sulfone) displayed two-step decomposition; the primary products of decomposition at both steps were the comonomers (olefin and SO2). For poly(styrene sulfone), in addition to styrene and SO2, products with molecular weights corresponding to dimers of styrene were observed. Decomposition of this polymer was compared with that of polystyrene, which formed mostly monomer. 相似文献
84.
SAT-Solving the Coverability Problem for Petri Nets 总被引:2,自引:0,他引:2
Parosh Aziz Abdulla S. Purushothaman Iyer Aletta Nylén 《Formal Methods in System Design》2004,24(1):25-43
Net unfoldings have attracted great attention as a powerful technique for combating state space explosion in model checking, and have been applied to verification of finite state systems including 1-safe (finite) Petri nets and synchronous products of finite transition systems. Given that net unfoldings represent the state space in a distributed, implicit manner the verification algorithm is necessarily a two step process: generation of the unfolding and reasoning about it. In his seminal work McMillan (K.L. McMillan, Symbolic Model Checking. Kluwer Academic Publishers, 1993) showed that deadlock detection on unfoldings of 1-safe Petri nets is NP-complete. Since the deadlock problem on Petri nets is PSPACE-hard it is generally accepted that the two step process will yield savings (in time and space) provided the unfoldings are small.In this paper we show how unfoldings can be extended to the context of infinite-state systems. More precisely, we show how unfoldings can be constructed to represent sets of backward reachable states of unbounded Petri nets in a symbolic fashion. Furthermore, based on unfoldings, we show how to solve the coverability problem for unbounded Petri nets using a SAT-solver. Our experiments show that the use of unfoldings, in spite of the two-step process for solving coverability, has better time and space characteristics compared to a traditional reachability based implementation that considers all interleavings for solving the coverability problem. 相似文献
85.
A heuristic algorithm for the formation of part families to design cells with consideration to alternative routing of parts is presented. Most of the existing algorithms in cellular manufacturing systems utilize fixed routings for parts. Consideration of alternative routings in the design of cells is important for improving operational aspects of cellular manufacturing systems. An example problem solved is included in the paper. 相似文献
86.
A new formula for calculating the calorific value of coal from its ultimate analysis has been obtained by regression analysis of a data bank consisting of data on 775 samples of U.S. coals of all ranks. It yielded zero average difference between observed and calculated values and a standard deviation of 129 Btu/lb (300 kJ/kg). Neither average difference nor standard deviation varied much with rank of the coal. The Dulong, Mott-Spooner, Boie, and Grummel-Davies formulae were also tested with the data but gave substantially poorer results. The new formula has been substantiated with data from other laboratories and with data on chars. The distribution of variance, attributable to variability of mineral matter, variability of coal organic matter not related to rank, and variance of laboratory determinations was estimated. Use of the formula to monitor performance of a laboratory is illustrated, as is modification to obtain maximum precision in heat balance calculations on a coal conversion process. 相似文献
87.
A THERMODYNAMIC MODEL OF THE HEAT CAPACITY OF COMPOSITIONALLY COMPLEX MULTICOMPONENT POLYMER SOLUTIONS: KRAFT BLACK LIQUOR 总被引:1,自引:0,他引:1
A thermodynamic model of the heat capacity of multicomponent polymer solutions is developed and applied to the prediction of the heat capacity of kraft black liquor. The model is developed using a pseudo-binary solution assumption. The form of the excess heat capacity is expressed as CpE = γWnW1Wm2 where γ, m, and n are model parameters. For the particular system studied γ varies linearly with temperature and indicates the magnitude and degree of temperature dependence of the excess heat capacity. Parameters m and n are independent of temperature. The resulting model is capable of predicting the heat capacity of compositionally complex black liquor to within 1-3% of the experimental data. @KEYWORDS: Heat capacity, Thermodynamics, Kraft black liquor, Polymer solutions 相似文献
88.
I. D. Moore N. Purushothaman B. S. Heaton 《International journal for numerical methods in engineering》1988,26(2):437-452
A three-dimensional finite element model has been developed to simulate the sliding of a rubber block over a grooved road surface. The model makes use of the symmetries of the problem to simplify the analysis, so that two-dimensional isoparametric elements of both rectangular and triangular configuration have been extended into the third dimension. A procedure for analysing the behaviour of any one groove to groove unit of the pavement is also developed, and this is extended so that the contact between the sliding rubber block and the leading edge of each raised pavement section is analysed. Preliminary comparisons between theoretical calculations and experimental measurements indicate that the finite element procedure provides an accurate and economical estimate of the behaviour of the rubber slider as it is pressed into a grooved pavement. Elastic predictions of sliding resistance seem reasonable at low sliding speeds, but viscoelastic rubber analysis appears necessary if higher speed skid resistance is to be predicted. 相似文献
89.
p-nitrobenzyl triphenyl phosphonium ylide initiated radical polymerisation of MMA in 1-4 dioxane at 65 ± 1°C for 2 h under
a nitrogen blanket, follows ideal kinetics with bimolecular termination. The overall activation energy and average value of
k
p
2/k
t are 75.7 kJ mol and 1.14 × 102 l mol−1 s−1. FTIR Spectroscopy confirms a band of 1,729 cm−1 of the ester group. 1H NMR and 13C NMR confirms methoxy protons at 3.8 δ ppm and 52 δ ppm, respectively. E.S.R studies confirm a free radical mode of polymerisation. TGDTA analysis confirms the atactic nature
of polymer and its thermal stability up to 120°C. Ylide dissociates to give a phenyl radical which is responsible for polymerisation. 相似文献
90.
Decision rules for inventory control parameters are combined in a microcomputer based information and decision system. Decision rules implemented in IDSIM cover a wide variety of models for deterministic and stochastic demand cases. The system consists of four modules: The determination of economic order and production quantities and the evaluation of any arbitrary ordering rule in terms of carrying and ordering costs are accomplished in the first module. The second module deals with aggregate level decisions for deterministic demand systems, generates Total Cycle Stock curves, and addresses the problems of group replenishment and group discounts for deterministic systems. The third module calculates the optimum safety stock levels and optimum values of control parameters for order/point quantity as well as periodic review/order-up-to-level parameters in stochastic systems with normal and Laplace distributions. Other sophisticated algorithms, which utilize iterative procedures and yield near optimal solutions, are incorporated in the fourth module for the allocation of total safety stock to minimize either the expected number of stockouts or the total value of shortages. 相似文献