全文获取类型
收费全文 | 76153篇 |
免费 | 8922篇 |
国内免费 | 5894篇 |
专业分类
电工技术 | 6418篇 |
技术理论 | 4篇 |
综合类 | 7058篇 |
化学工业 | 10536篇 |
金属工艺 | 2436篇 |
机械仪表 | 4900篇 |
建筑科学 | 3227篇 |
矿业工程 | 1767篇 |
能源动力 | 5507篇 |
轻工业 | 1315篇 |
水利工程 | 5376篇 |
石油天然气 | 4052篇 |
武器工业 | 698篇 |
无线电 | 7469篇 |
一般工业技术 | 5793篇 |
冶金工业 | 3354篇 |
原子能技术 | 1401篇 |
自动化技术 | 19658篇 |
出版年
2024年 | 392篇 |
2023年 | 1247篇 |
2022年 | 1979篇 |
2021年 | 2312篇 |
2020年 | 2553篇 |
2019年 | 2213篇 |
2018年 | 2065篇 |
2017年 | 2632篇 |
2016年 | 2971篇 |
2015年 | 3170篇 |
2014年 | 4354篇 |
2013年 | 5141篇 |
2012年 | 5030篇 |
2011年 | 5838篇 |
2010年 | 4184篇 |
2009年 | 4793篇 |
2008年 | 4659篇 |
2007年 | 5080篇 |
2006年 | 4523篇 |
2005年 | 3997篇 |
2004年 | 3349篇 |
2003年 | 2973篇 |
2002年 | 2496篇 |
2001年 | 2113篇 |
2000年 | 1874篇 |
1999年 | 1562篇 |
1998年 | 1331篇 |
1997年 | 1132篇 |
1996年 | 1008篇 |
1995年 | 861篇 |
1994年 | 710篇 |
1993年 | 555篇 |
1992年 | 445篇 |
1991年 | 274篇 |
1990年 | 265篇 |
1989年 | 192篇 |
1988年 | 142篇 |
1987年 | 102篇 |
1986年 | 74篇 |
1985年 | 71篇 |
1984年 | 78篇 |
1983年 | 66篇 |
1982年 | 57篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1959年 | 21篇 |
1951年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Anna Hać 《Journal of Network and Systems Management》1994,2(1):49-62
This paper analyzes the performance of a switching architecture. The performance measures include the elapsed time of packet transfer and the waiting time to begin transfer. The architecture is partitioned depending on the type of network used and the expected traffic in the network. Every partition has a switch with a buffer that can absorb surges of bursty traffic within the network partition. The buffer size depends on the type of the network and incoming traffic. The partition size depends on the network bandwidth, network traffic, packet size and buffer size. Examples of different networks are used to show the applications of the model. The results show that the elapsed time of packet switch transfer depends exponentially on the number of partitions in the network. 相似文献
112.
In ATM networks the requirement of providing the negotiated Quality of Service (QOS) needs an efficient flow enforcement technique that will result in preventive congestion control. A very effective technique is the Exponentially Weighted Moving Average (EWMA) method. In this paper, we have suggested improvements to the EWMA and call it the Enhanced EWMA (EEWMA). Simulation results show that the EEWMA is consistently better than the EWMA in most of the situations. We present comparisons of cell loss under various conditions. No theoretical analysis is presented. 相似文献
113.
114.
This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate. 相似文献
115.
α,ω-Methacrylate-terminated poly(1,3-dioxolane)s (polyDXL) were synthesized by cationic ring-opening polymerization of DXL in the presence of methylene-bis(oxyethylmethacrylate) as transfer agent. If the initiator concentration is small compared with the transfer agent concentration, the molecular weights of the polymers are governed by the ratio of the reacted monomer to the reacted transfer agent. The α,ω-methacrylate-terminated polyDXLs obtained undergo free radical polymerization with formation of polyacetal networks. The properties of the networks as function of the molecular weight of the corresponding prepolymers are reported. 相似文献
116.
A mixed mode digital/analog special purpose VLSI hardware implementation of an associative memory with neural architecture is presented. The memory concept is based on a matrix architecture with binary storage elements holding the connection weights. To enhance the processing speed analog circuit techniques are applied to implement the algorithm for the association. To keep the memory density as high as possible two design strategies are considered. First, the number of transistors per storage element is kept to a minimum. In this paper a circuit technique that uses a single 6-transistor cell for weight storage and analog signal processing is proposed. Second, the device precision has been chosen to a moderate level to save area as much as possible. Since device mismatch limits the performance of analog circuits, the impact of device precision on the circuit performance is explicitly discussed. It is shown that the device precision limits the number of rows activated in parallel. Since the input vector as well as the output vector are considered to be sparsely coded it is concluded, that even for large matrices the proposed circuit technique is appropriate and ultra large scale integration with a large number of connection weights is feasible. 相似文献
117.
118.
考虑变质量湍流影响的水平井流入动态分析 总被引:1,自引:0,他引:1
在水平井生产过程中,井筒内管流与地层渗流互相制约、互相影响、互为边界条件,从而构成了一个完整的水动力学体系。根据水平井生产时井筒内管流与油藏的相互作用关系,建立了水平井筒存在压力梯度的变质量湍流与地层渗流的耦合计算新方法。关于井筒内流的计算;应用了经典的kεM湍流模型,关于地层的渗流计算,采用了有限元法。通过耦合模拟获得了井筒内湍流场流速分布及总压能损耗的规律,根据耦合模拟计算结果绘出了较为准确的水平井流入动态曲线。该计算方法为描述水平井流入动态、评价水平井产能、确定合理生产制度提供了可靠的手段. 相似文献
119.
高含蜡原油管道停输后的再启动问题非常复杂。它涉及因素多,问题的非线性很强。而有足够多神经元的S型三层神经网络理论上可逼近任意有理函数。文章采用误差反向传播网络预测环道实验装置中的启动压力,得到了较好结果。 相似文献
120.
介绍了质量流量计的工作原理有应用效果。这种新型质量流量计精度高,稳定性好,示值计量简便,可直接显示质量、流量、介质温度、密度等,维护量低,但必须正确安装、使用,才能发挥其应有的作用。 相似文献