全文获取类型
收费全文 | 37996篇 |
免费 | 3633篇 |
国内免费 | 3024篇 |
专业分类
电工技术 | 2772篇 |
技术理论 | 1篇 |
综合类 | 5167篇 |
化学工业 | 1677篇 |
金属工艺 | 692篇 |
机械仪表 | 2279篇 |
建筑科学 | 2286篇 |
矿业工程 | 750篇 |
能源动力 | 915篇 |
轻工业 | 629篇 |
水利工程 | 939篇 |
石油天然气 | 590篇 |
武器工业 | 270篇 |
无线电 | 2801篇 |
一般工业技术 | 3804篇 |
冶金工业 | 1095篇 |
原子能技术 | 209篇 |
自动化技术 | 17777篇 |
出版年
2024年 | 123篇 |
2023年 | 340篇 |
2022年 | 561篇 |
2021年 | 703篇 |
2020年 | 936篇 |
2019年 | 993篇 |
2018年 | 887篇 |
2017年 | 1188篇 |
2016年 | 1311篇 |
2015年 | 1390篇 |
2014年 | 2318篇 |
2013年 | 2875篇 |
2012年 | 2595篇 |
2011年 | 2580篇 |
2010年 | 2075篇 |
2009年 | 2345篇 |
2008年 | 2474篇 |
2007年 | 2604篇 |
2006年 | 2270篇 |
2005年 | 2025篇 |
2004年 | 1651篇 |
2003年 | 1478篇 |
2002年 | 1232篇 |
2001年 | 1153篇 |
2000年 | 986篇 |
1999年 | 820篇 |
1998年 | 657篇 |
1997年 | 592篇 |
1996年 | 501篇 |
1995年 | 456篇 |
1994年 | 425篇 |
1993年 | 335篇 |
1992年 | 298篇 |
1991年 | 251篇 |
1990年 | 195篇 |
1989年 | 188篇 |
1988年 | 155篇 |
1987年 | 85篇 |
1986年 | 75篇 |
1985年 | 55篇 |
1984年 | 69篇 |
1983年 | 46篇 |
1982年 | 53篇 |
1981年 | 42篇 |
1980年 | 37篇 |
1979年 | 42篇 |
1978年 | 19篇 |
1977年 | 30篇 |
1976年 | 17篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
含多类型分布式电源的微电网已经成为了未来电力系统的重要发展方向,其中风能和光能在降低化石能源消耗和二氧化碳排放等方面有着极大优势,考虑二者之间强互补性的协同调度已被广泛研究.但风/光协同调度的微电网多关注分钟级的调度或优化问题而非风/光波动下秒级的实时电流按容量比例精准分担,简称电流均衡,而精准电流均衡有助于可再生能源的高比例消纳.因此,本文提出了基于自适应动态规划的微电网电流均衡和电压恢复控制策略.首先,构建包含风电整流型电能变换器和光电升压型电能变换器的广义风光拓扑同胚升压变换器模型,其提供了后续控制器设计的模型基础.其次,本文将电流均衡和电压恢复问题转化为最优控制问题,基于此,每个能源主体的目标函数转化为获取最优控制变量和最小电压/电流控制偏差,进而转化为求解哈密顿?雅克比?贝尔曼(Hamilton-Jacobi-Bellman,HJB)方程问题.基于此,提出了基于贝尔曼准则的分布式自适应动态规划控制策略以求取HJB方程的数值解,最终实现电流均衡和电压恢复.最后仿真结果验证了所提分布式自适应动态规划控制策略的有效性. 相似文献
993.
《The Journal of Strategic Information Systems》2022,31(1):101708
With business ecosystems digitalizing by the force of digital innovation, the deployment of boundary resources (such as application programming interfaces: APIs) becomes a strategic option across contexts. We distinguish between boundary resources that provide access openness and those that provide resource openness, and theorize the antecedents and consequences of their deployment. Employing panel data regressions to a longitudinal cross-industry dataset, we find that the digital knowledge base of the focal firm and the existence of potential digital complementors drive boundary resource deployment. Such deployment benefits firm performance depending on the firm’s market power. From our empirical analysis, we reveal a differentiated perspective on the quality of the confined openness provided by boundary resources as well as the embeddedness of their deployment in the rationales and motivations of the associated actors in digital business ecosystems. We complement the existent theoretical framework on boundary resources and provide valuable insights to managers reflecting about deploying boundary resources in a beneficial way. 相似文献
994.
Phan Nguyen Ky Phuc 《计算机系统科学与工程》2022,40(1):75-85
Stochastic demand is an important factor that heavily affects production planning. It influences activities such as purchasing, manufacturing, and selling, and quick adaption is required. In production planning, for reasons such as reducing costs and obtaining supplier discounts, many decisions must be made in the initial stage when demand has not been realized. The effects of non-optimal decisions will propagate to later stages, which can lead to losses due to overstocks or out-of-stocks. To find the optimal solutions for the initial and later stage regarding demand realization, this study proposes a stochastic two-stage linear programming model for a multi-supplier, multi-material, and multi-product purchasing and production planning process. The objective function is the expected total cost after two stages, and the results include detailed plans for purchasing and production in each demand scenario. Small-scale problems are solved through a deterministic equivalent transformation technique. To solve the problems in the large scale, an algorithm combining metaheuristic and sample average approximation is suggested. This algorithm can be implemented in parallel to utilize the power of the solver. The algorithm based on the observation that if the remaining quantity of materials and number of units of products at the end of the initial stage are given, then the problems of the first and second stages can be decomposed. 相似文献
995.
在国产异构众核平台神威·太湖之光上的非结构网格计算具有稀疏存储、离散访存、数据依赖等特点,严重制约了众核处理器的性能发挥。为解决稀疏存储和离散访存问题,提出一种N阶对角染色算法,以有效平衡主从核计算并利用从核将全局访存转化为LDM访问。针对数据依赖造成的计算竞争问题,采用自适应和无依赖的任务划分方法,避免并行计算时的数据冲突。为对处理器架构和非结构网格计算进行优化,采用主核与从核异步并行的方式,差异化使用主从核以充分利用硬件资源,同时,取消处理器提供的寄存器通信机制,降低从核阵列的同步开销同时便于扩展到新一代神威平台。此外,使用计算访存异步重叠技术来充分隐藏访存延迟。利用SpMV、Integration、calcLudsFcc算子进行实验,结果表明,相比主核实现,组合加速算法在不同算例规模下平均取得了10倍的加速效果,加速比最高可达24倍,N阶对角染色算法相比非染色分块算法取得了超过5.8倍的性能加速,有效提升了数据局部性和计算并行度。该算法对有依赖关系的计算冲突算子同样具有良好的加速性能,验证了自适应和无依赖任务划分方法的有效性。 相似文献
996.
Wei Zhou Xiaoming Huang Linbing Wang 《International Journal of Pavement Engineering》2017,18(4):285-291
The objective of this study was to analyse the void reduction behaviour of porous asphalt mixture under load. A three-dimensional discrete element model of porous asphalt mixture based on aggregate gradation and void gradation was built in PFC3D software. The parameter of the model was obtained from creep test. The rutting test was simulated using this discrete element model. And a new method was developed to obtain and analyse the void structure in discrete element model. The simulation results were compared with one of the laboratory test. The comparative analysis indicates that, the discrete element method can be used to simulate the creep response and void reduction behaviour of porous asphalt mixture. Further research shows that porosity, effective porosity, number of connected components and section pores have a good correlation with strain of porous asphalt mixture. With the increase in strain, the proportion of section pores with diameter less than 2 mm increases. In the initial stage of loading, the void reduction is the main reason for rut increment of porous asphalt mixture. In the later stage, the void structure is almost incompressible; the lateral deformation of mixture becomes the domination factor. 相似文献
997.
998.
L. Marin A. Karageorghis D. Lesnic B. T. Johansson 《Inverse Problems in Science & Engineering》2017,25(5):652-673
An inverse problem in static thermo-elasticity is investigated. The aim is to reconstruct the unspecified boundary data, as well as the temperature and displacement inside a body from over-specified boundary data measured on an accessible portion of its boundary. The problem is linear but ill-posed. The uniqueness of the solution is established but the continuous dependence on the input data is violated. In order to reconstruct a stable and accurate solution, the method of fundamental solutions is combined with Tikhonov regularization where the regularization parameter is selected based on the L-curve criterion. Numerical results are presented in both two and three dimensions showing the feasibility and ease of implementation of the proposed technique. 相似文献
999.
1000.
Md. Shahriar J. Hossain 《国际生产研究杂志》2016,54(12):3603-3621
The production rate and product quality are two vital concerns for any manufacturing industry. Number of defective items reduces production rate and increases unit production cost. Moreover, if nonconforming items reach to the customers then manufacturer’s goodwill may drastically go down. Thus, quality inspection is treated as an inherent part of manufacturing. In this research, an N-stage serial production line with an inspection station at the end of it is considered to make decisions concerning this issue. On detecting a defective item at the end of the line it is scrapped or repaired at regular workstation or is sent to an off-line rework station for repair. Assuming each workstation produces a single type of defect a unit cost function is developed for alternative decisions on each type of defect. In order to minimise the unit cost of production and determine an appropriate decision for individual defect types, a fractional mixed integer nonlinear programming is formulated. After transformation to a mixed integer linear programming problem it is solved optimally. A small problem from garments industry is described in detail to show the solution procedure with a branch and bound method. Empirical tests with up to 40 workstations are permed to show the efficiency of the solution process. 相似文献