全文获取类型
收费全文 | 5271篇 |
免费 | 338篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 100篇 |
综合类 | 2篇 |
化学工业 | 1405篇 |
金属工艺 | 134篇 |
机械仪表 | 175篇 |
建筑科学 | 128篇 |
矿业工程 | 7篇 |
能源动力 | 209篇 |
轻工业 | 884篇 |
水利工程 | 43篇 |
石油天然气 | 31篇 |
无线电 | 393篇 |
一般工业技术 | 966篇 |
冶金工业 | 554篇 |
原子能技术 | 46篇 |
自动化技术 | 540篇 |
出版年
2024年 | 15篇 |
2023年 | 57篇 |
2022年 | 153篇 |
2021年 | 222篇 |
2020年 | 146篇 |
2019年 | 177篇 |
2018年 | 202篇 |
2017年 | 224篇 |
2016年 | 196篇 |
2015年 | 164篇 |
2014年 | 252篇 |
2013年 | 357篇 |
2012年 | 337篇 |
2011年 | 358篇 |
2010年 | 283篇 |
2009年 | 300篇 |
2008年 | 258篇 |
2007年 | 236篇 |
2006年 | 206篇 |
2005年 | 144篇 |
2004年 | 120篇 |
2003年 | 109篇 |
2002年 | 82篇 |
2001年 | 67篇 |
2000年 | 48篇 |
1999年 | 72篇 |
1998年 | 162篇 |
1997年 | 138篇 |
1996年 | 87篇 |
1995年 | 58篇 |
1994年 | 53篇 |
1993年 | 45篇 |
1992年 | 21篇 |
1991年 | 36篇 |
1990年 | 38篇 |
1989年 | 18篇 |
1988年 | 31篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 22篇 |
1974年 | 5篇 |
1971年 | 3篇 |
排序方式: 共有5617条查询结果,搜索用时 15 毫秒
61.
Three formulations of mix concentrated milk with hydrosolubles extract of soybean powder and cow's milk were prepared. The products were condensed up to 31% and 33.65% of solids in a vacuum evaporator at temperature of 45 degrees and 58 degrees C with a vacuum pressure of 540 mmHg. The products obtained were compared with standard concentrated milk through sensory evaluation showing satisfactory characteristics. 相似文献
62.
Thermotropic polyesters prepared from series of 4,4-dihydroxy-,w-diphenoxy alkanes and 4,4-dichloroformyl-,w-diphenoxy alkanes are well known. The substitution of a methylenic spacer by an oxyethylenic spacer in the main chain of these polyesters drastically modifies their physical properties, particularly the mesogenic transition temperatures, as can be observed by DSC and thermooptical analysis. The thermal stability and the polymer solubility in common organic solvents of these polymers did not show a significant change. The physical properties of the two thermotropic polyesters prepared in diphenyl ether were evaluated. 相似文献
63.
Boundary scan test,test methodology,and fault modeling 总被引:1,自引:0,他引:1
The test technique called boundary scan test (BST) offers new opportunities in testing but confronts users with new problems too. The implementation of BST in a chip has become an IEEE standard and users on board level are the next group to begin thinking about using the new possibilities. This article addresses some of the questions about changes in board-level testing and fault diagnosis. The fault model itself is also affected by using BST. Trivial items are extended with more sophisticated details in order to complete the fault model. Finally, BST appears to be a test technique that offers a high degree of detectability on board level, but for diagnosis, some additional effort has to be made. 相似文献
64.
Electrochemical tests were carried out on steel/steel multi-laminar cells under thin layers of sulphate solution simulating atmospheres with contents of 20, 50 and 75 μg m−3 of SO2 and a relative humidity of 85%. Measurements of the current flowing between the two electrodes of the cell vs drying time and impedance measurements for different times were taken. Potentiodynamic cathodic polarization plots were also obtained for one concentration of contaminant at various drying times using three electrode multi-laminar cells. The results showed that the multi-laminar cells allowed the drying process of the thin electrolyte films to be followed. The use of electrochemical techniques gave information on the kinetics and mechanism of the corrosion process occurring during the drying period. Initially the process is controlled by oxygen diffusion through the liquid film, but for longer periods the control changes to the anodic reaction. 相似文献
65.
Expert finding is an information retrieval task that is concerned with the search for the most knowledgeable people with respect to a specific topic, and the search is based on documents that describe people's activities. The task involves taking a user query as input and returning a list of people who are sorted by their level of expertise with respect to the user query. Despite recent interest in the area, the current state‐of‐the‐art techniques lack in principled approaches for optimally combining different sources of evidence. This article proposes two frameworks for combining multiple estimators of expertise. These estimators are derived from textual contents, from graph‐structure of the citation patterns for the community of experts and from profile information about the experts. More specifically, this article explores the use of supervised learning to rank methods, as well as rank aggregation approaches, for combining all of the estimators of expertise. Several supervised learning algorithms, which are representative of the pointwise, pairwise and listwise approaches, were tested, and various state‐of‐the‐art data fusion techniques were also explored for the rank aggregation framework. Experiments that were performed on a dataset of academic publications from the Computer Science domain attest the adequacy of the proposed approaches. 相似文献
66.
67.
Andrew B. Lambe Joaquim R. R. A. Martins 《Structural and Multidisciplinary Optimization》2016,53(3):589-603
In structural optimization subject to failure constraints, computing the gradients of a large number of functions with respect to a large number of design variables may not be computationally practical. Often, the number of constraints in these optimization problems is reduced using constraint aggregation at the expense of a higher mass of the optimal structural design. This work presents results of structural and coupled aerodynamic and structural design optimization of aircraft wings using a novel matrix-free augmented Lagrangian optimizer. By using a matrix-free optimizer, the computation of the full constraint Jacobian at each iteration is replaced by the computation of a small number of Jacobian-vector products. The low cost of the Jacobian-vector products allows optimization problems with thousands of failure constraints to be solved directly, mitigating the effects of constraint aggregation. The results indicate that the matrix-free optimizer reduces the computational work of solving the optimization problem by an order of magnitude compared to a traditional sequential quadratic programming optimizer. Furthermore, the use of a matrix-free optimizer makes the solution of large multidisciplinary design problems, in which gradient information must be obtained through iterative methods, computationally tractable. 相似文献
68.
Francisco Henrique Ferreira Ana Paula C. da Silva Alex B. Vieira 《Peer-to-Peer Networking and Applications》2016,9(1):1-15
Despite the large number of works devoted to understand P2P live streaming applications, most of them put forth so far rely on characterizing the static view of these systems. In this work, we characterize the SopCast, one of the most important P2P live streaming applications. We focus on its dynamics behavior as well as on the community formation phenomena. Our results show that SopCast presents a low overlay topology diameter and low end-to-end shortest path. In fact, diameter is smaller than 6 hops in almost 90 % of the observation time. More than 96 % of peers’ end-to-end connections present only 3 hops. These values combined may lead to low latencies and a fast streaming diffusion. Second, we show that communities in SopCast are well defined by the streaming data exchange process. Moreover, the SopCast protocol does not group peers according to their Autonomous System. In fact, the probability that a community contains 50 % of its members belonging to the same AS (when we observe the largest AS of our experiments) is lower then 10 %. Peers exchange more data with partners belonging to the same community instead of peers inside the same AS. For the largest AS we have, less than 18 % of peer traffic has been exchanged with another AS partners. Finally, our analysis provides important information to support the future design of more efficient P2P live streaming systems and new protocols that exploit communities’ relationships. 相似文献
69.
70.
Requena C.G. Requena M.E.G. Rodriguez P.J.L. Marin J.F.D. 《Parallel and Distributed Systems, IEEE Transactions on》2009,20(6):802-817
Fault tolerance in the interconnection network of large clusters of PCs is an issue of growing importance, since their increasing size also increases the failure probability. The fat-tree topology is usually used in these machines since it has become very popular among high-speed interconnect manufacturers. This paper proposes a new distributed fault-tolerant routing methodology for fat trees. Unlike other previous proposals, it does not require additional network hardware, and its memory requirements, switch hardware, and routing delay scales up with the network size. Indeed, it nullifies only the strictly necessary paths, allowing adaptive routing through the healthy paths. The methodology is based on enhancing the interval routing scheme with exclusion intervals. Exclusion intervals are associated to each switch output port and represent the nodes that are unreachable from this port after a fault. We propose a methodology to identify the links where the exclusion intervals must be updated after a fault, the values to write on them, and a very efficient mechanism to distribute the required information through the network without stopping the system activity. Our methodology can tolerate a high number of network failures with a low degradation in performance. Moreover, it can achieve zero packet losing during the updating period. 相似文献