全文获取类型
收费全文 | 230351篇 |
免费 | 17678篇 |
国内免费 | 9281篇 |
专业分类
电工技术 | 12617篇 |
技术理论 | 24篇 |
综合类 | 14239篇 |
化学工业 | 39061篇 |
金属工艺 | 13253篇 |
机械仪表 | 14592篇 |
建筑科学 | 17643篇 |
矿业工程 | 7564篇 |
能源动力 | 6456篇 |
轻工业 | 13525篇 |
水利工程 | 3614篇 |
石油天然气 | 16868篇 |
武器工业 | 1662篇 |
无线电 | 25306篇 |
一般工业技术 | 27451篇 |
冶金工业 | 12844篇 |
原子能技术 | 2295篇 |
自动化技术 | 28296篇 |
出版年
2024年 | 1004篇 |
2023年 | 3830篇 |
2022年 | 6546篇 |
2021年 | 9213篇 |
2020年 | 7131篇 |
2019年 | 6051篇 |
2018年 | 6779篇 |
2017年 | 7585篇 |
2016年 | 6791篇 |
2015年 | 8936篇 |
2014年 | 11329篇 |
2013年 | 13370篇 |
2012年 | 14342篇 |
2011年 | 15563篇 |
2010年 | 13506篇 |
2009年 | 12769篇 |
2008年 | 12427篇 |
2007年 | 11937篇 |
2006年 | 12421篇 |
2005年 | 10841篇 |
2004年 | 7315篇 |
2003年 | 6283篇 |
2002年 | 5495篇 |
2001年 | 4917篇 |
2000年 | 5449篇 |
1999年 | 6471篇 |
1998年 | 5463篇 |
1997年 | 4474篇 |
1996年 | 4212篇 |
1995年 | 3513篇 |
1994年 | 2826篇 |
1993年 | 1974篇 |
1992年 | 1544篇 |
1991年 | 1228篇 |
1990年 | 938篇 |
1989年 | 741篇 |
1988年 | 543篇 |
1987年 | 336篇 |
1986年 | 279篇 |
1985年 | 198篇 |
1984年 | 140篇 |
1983年 | 114篇 |
1982年 | 124篇 |
1981年 | 99篇 |
1980年 | 70篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
所开发的压水堆核燃料循环分析计算机经济程序包括12个子程序,代表着压水堆整个核燃料循环各种不同的工艺过程。本程序能算出压水堆核电站核燃料循环中燃料费用对发电成本的影响,给出各工艺过程对燃料成本的敏感度分析,并尽可能给出燃料循环中燃料材料及服务的价格数据. 相似文献
32.
In this study, distribution and history of residual stresses in plaque-like geometries are simulated based on linear thermoviscoelastic
model, which helps to understand the mechanics and evolution of the residual stresses in the injection molding process. The
numerical calculation of direction, combined with the specified boundary conditions. Results show that the stress variation
across the thickness exhibits a high surface tensile value changing to a compressive peak value close to the surface, with
the core region experiencing a parabolic tensile peak. Residual stress distribution throughout the thickness is almost same
along the flowpath and the final residual stresses value near the gate is lower than the value near the end of flowpath. 相似文献
33.
Pattern search algorithms for nonlinear inversion of high-frequency Rayleigh-wave dispersion curves 总被引:1,自引:0,他引:1
Inversion of Rayleigh wave dispersion curves is challenging for most local-search methods due to its high nonlinearity and to its multimodality. In this paper, we implemented and tested a Rayleigh wave dispersion curve inversion scheme based on GPS Positive Basis 2N, a commonly used pattern search algorithm. Incorporating complete poll and complete search strategies based on GPS Positive Basis 2N into the inverse procedure greatly enhances the performance of pattern search algorithms because the two steps can effectively locate the promising areas in the solution space containing the global minima and significantly reduce the computation cost, respectively.The proposed inverse procedure was applied to nonlinear inversion of fundamental-mode Rayleigh wave dispersion curves for a near-surface shear (S)-wave velocity profile. The calculation efficiency and stability of the inversion scheme are tested on three synthetic models and a real example from a roadbed survey in Henan, China. Effects of the number of data points, the reduction of the frequency range of the considered dispersion curve, errors in P-wave velocities and density, the initial S-wave velocity profile as well as the number of layers and their thicknesses on inversion results are also investigated in the present study to further evaluate the performance of the proposed approach.Results demonstrate that pattern search algorithms applied to nonlinear inversion of high-frequency surface wave data should be considered good not only in terms of accuracy but also in terms of the computation effort due to their global and deterministic search process. 相似文献
34.
35.
Sankaralingam K. Nagarajan R. Haiming Liu Changkyu Kim Jaehyuk Huh Burger D. Keckler S.W. Moore C. 《Micro, IEEE》2003,23(6):46-51
The Tera-op reliable intelligently adaptive processing system (TRIPS) architecture seeks to deliver system-level configurability to applications and runtime systems. It does so by employing the concept of polymorphism, which permits the runtime system to configure the hardware execution resources to match the mode of execution and demands of the compiler and application. 相似文献
36.
37.
Novel algorithms for shared segment protection 总被引:8,自引:0,他引:8
Dahai Xu Yizhi Xiong Chunming Qiao 《Selected Areas in Communications, IEEE Journal on》2003,21(8):1320-1331
The major challenges in designing survivable schemes are how to allocate a minimal amount of spare resources (e.g., bandwidth) using fast (e.g., polynomial-time) algorithms, and, in case a failure occurs, to be able to recover quickly from it. All existing approaches invariably make tradeoffs. We propose novel shared segment protection algorithms which make little or no compromise . We develop an elegant integer linear programming (ILP) model to determine an optimal set of segments to protect a given active path. Although the ILP approach is useful for a medium-size network, it is too time consuming for large networks. Accordingly, we also design a fast heuristic algorithm based on dynamic programming to obtain a near-optimal set of segments. Although the heuristic algorithm has a polynomial time complexity, it can achieve a bandwidth efficiency as high as some best-performing shared path protection schemes and, at the same time, much faster recovery than these shared path protection schemes. The proposed scheme is also applicable to a wide range of networking technologies, including Internet Protocol and wavelength-division multiplexing networks under the generalized multiprotocol label switched framework. 相似文献
38.
39.
Voltage switching induced by long-wavelength infrared light from a CO2 laser was observed using a double-barrier resonant tunneling diode (RTD) biased in the bistable region and the intersubband transition (IT) between the quantum confined states. Possible optoelectronic and all-optical switching applications involving hysteresis are proposed and discussed 相似文献
40.