全文获取类型
收费全文 | 13455篇 |
免费 | 467篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 272篇 |
综合类 | 17篇 |
化学工业 | 2389篇 |
金属工艺 | 381篇 |
机械仪表 | 370篇 |
建筑科学 | 234篇 |
矿业工程 | 73篇 |
能源动力 | 741篇 |
轻工业 | 1227篇 |
水利工程 | 194篇 |
石油天然气 | 83篇 |
无线电 | 1721篇 |
一般工业技术 | 2943篇 |
冶金工业 | 1611篇 |
原子能技术 | 200篇 |
自动化技术 | 1525篇 |
出版年
2024年 | 39篇 |
2023年 | 181篇 |
2022年 | 514篇 |
2021年 | 526篇 |
2020年 | 423篇 |
2019年 | 426篇 |
2018年 | 576篇 |
2017年 | 529篇 |
2016年 | 499篇 |
2015年 | 299篇 |
2014年 | 467篇 |
2013年 | 928篇 |
2012年 | 541篇 |
2011年 | 712篇 |
2010年 | 570篇 |
2009年 | 568篇 |
2008年 | 510篇 |
2007年 | 424篇 |
2006年 | 348篇 |
2005年 | 288篇 |
2004年 | 264篇 |
2003年 | 238篇 |
2002年 | 196篇 |
2001年 | 157篇 |
2000年 | 158篇 |
1999年 | 169篇 |
1998年 | 364篇 |
1997年 | 243篇 |
1996年 | 260篇 |
1995年 | 234篇 |
1994年 | 197篇 |
1993年 | 184篇 |
1992年 | 151篇 |
1991年 | 158篇 |
1990年 | 122篇 |
1989年 | 111篇 |
1988年 | 139篇 |
1987年 | 111篇 |
1986年 | 98篇 |
1985年 | 128篇 |
1984年 | 103篇 |
1983年 | 116篇 |
1982年 | 108篇 |
1981年 | 93篇 |
1980年 | 83篇 |
1979年 | 54篇 |
1978年 | 48篇 |
1977年 | 59篇 |
1976年 | 79篇 |
1975年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
To convey the dynamic information related to traffic conditions in various parts of a city, we propose an environment utilizing the technology of smart phones to provide information anywhere and anytime. Called ";The Interactive Traffic Beat Project,"; it uses a Web-based service to deliver this information to people through their cell phones at the right time so that valuable time can be saved and the chaos on the roads can be managed. 相似文献
53.
Lean philosophy: implementation in a forging company 总被引:2,自引:2,他引:0
Ajit Kumar Sahoo N. K. Singh Ravi Shankar M. K. Tiwari 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):451-462
This research addresses the implementation of lean philosophy in a forging company with a focus on radial forging production
flow lines. Here, the prime motive is to evolve and test several strategies to eliminate waste on the shop floor. In this
research, a systematic approach is suggested for the implementation of lean principles. This paper describes an application
of value stream mapping (VSM). Consequently, the present and future states of value stream maps are constructed to improve
the production process by identifying waste and its sources. Furthermore, Taguchi’s method of design of experiments is pursued
here to minimize the forging defects produced due to imperfect operating conditions. A noticeable reduction in set-up time
and work-in-process (WIP) inventory level is substantiated. Finally, we conclude with a discussion of managerial implications
and the future scope of research. 相似文献
54.
María J. Martín David E. Singh J. Carlos Mourio Francisco F. Rivera Ramn Doallo Javier D. Bruguera 《Parallel Computing》2003,29(11-12):1763
The aim of this work is to provide a high performance air quality simulation using the STEM-II (Sulphur Transport Eulerian Model 2) program, a large-scale pollution modeling application. First, we optimize the sequential program with the aim of increasing data locality. Then, we parallelized the program using OpenMP directives for shared memory systems, and the MPI library for distributed memory machines. Performance results are presented for a SGI O2000 multiprocessor, a Fujitsu AP3000 multicomputer and a Cluster of PCs. Experimental results show that the parallel versions of the code achieve important reductions in the CPU time needed by each simulation. This will allow us to obtain results with adequate speed and reliability for the industrial environment where it is intended to be applied. 相似文献
55.
56.
Sushil K. Singh 《Canadian Metallurgical Quarterly》2007,133(2):155-161
A semianalytical model is developed for computing drawdowns in and around a partially penetrating large diameter well. The new model can take into account an unsteady pumping discharge and thus drawdowns during recovery can be computed. This model can also yield the unsteady contributions from well and aquifer storages to the pumped discharge. While developing the model, the flow from the bottom of the well is also accounted. 相似文献
57.
Sudhir Singh Bhadauria Dr. Mahesh Chandra Gupta 《Canadian Metallurgical Quarterly》2007,21(3):234-239
Reports of failure of existing concrete structures due to a lack of durability, rather than a deficiency in structural strength, has made concrete technologists, engineers, and researchers focus research on the parameters influencing durability performance with respect to time. Systematic performance monitoring, with respect to chosen durability parameters of existing concrete structures, will decide the direction of future research in this area. Inferences based on laboratory simulations and testing need to be confirmed by in situ field measurements and studies. In situ condition rating and performance monitoring surveys have been conducted by many researchers, scientists, and professional associations, and reported in literature. Inferences of few such studies are summarized and discussed. Deterioration of concrete structures constructed in recent times is observed at relatively faster rates, and has been mainly attributed to cracking. Cracking is associated with the use of faster-hydrating portland cements with increased fineness and the tricalcium silicate (C3S) content to support the high speed of modern construction. In the present research, a case study of deteriorated water tank structures situated in the semitropical region of India is presented. Some selected parameters—such as concrete cover, carbonation depth, chloride concentration, compressive strength, etc. which influence long term durability of structures—have been measured. 相似文献
58.
59.
A. Singh 《AI & Society》2007,21(1-2):27-46
The paper explores the relation between reason and action as it emerges from the texts of āyurveda. Life or Ayus (commonly understood as life-span) is primary subject matter of Ayurveda. Life is a locus of experience, action and disposition. Experiences and actions are differentially determined by dispositions that characterize the organism; otherwise all living organisms will be identical. Ayus of each living being is uniquely individual and remains constant between birth and death. In this journey, upkeep of ayus is the purpose of āyurveda or science of life. Ayurveda is a science of experienced matter as well as of experienced body. The living body is critically dependent on the influx of matter for its upkeep. āyurveda offers a conceptual system to reason about balance and imbalances of the system and the causal role of the material flux through the system. This sensate matter is causally open and makes room for definite causal role for the individual and the effective insertion of the felt-purpose of action. Some of the strengths of Ayurveda are brought forth in the paper such as (a) reasoning out the compatibility between the bodily processes and the selection of the natural products for diet and drug, (b) role for heuristics in medical diagnosis, which takes into cognizance the particularity of each living body and the teleology evident in the very act of diagnostic reasoning. The paper shows that āyurvedic theory is built on experiential datum whereas scientific medical theory is built on experience-independent datum. āyurveda explores causal efficacy of ‘secondary qualities’ whereas scientific medicine explores causal efficacy of ‘primary qualities’. The actionable experiential reasoning is at the foundations of āyurveda whereas modern medical science is ab initio saddled with difficult ‘hiatus theoreticus’ between theory and practice. For Ayurveda it is experience of qualities that discloses behavior of matter. The types of qualities that appear in experience have a special significance for theorizing about the actions of matter with the help of qualities. The paper explores the relation between experience of qualities and the method of science. It shows how efficacy of medical practice is based on the foundational stance of experiential realism in theory. To bring the point home, the paper borrows Aristotalian concepts to show how the relation between phantasm and phronesis is honored in the very theory of āyurveda. 相似文献
60.
Yuan Y. Jambunathan R. Singh J. Bhattacharya P. 《Quantum Electronics, IEEE Journal of》1997,33(3):408-415
The performance characteristics of a coupled cavity InGaAsP-InP MQW laser/active waveguide made by one-step epitaxy and well-controlled reactive ion etching (RIE) have been theoretically analyzed and experimentally determined. A theoretical model based on a finite-difference time-domain (FDTD) technique was used to simulate the propagation of an optical wave launched in the coupled system and determine the reflectivity of the facets created by RIE. The calculated effective reflectivity of the coupling region consisting of two facets and an air gap is between 0.45 and 0.55, which is in good agreement with the experimentally measured value of 0.5. The reflectivity of a single etched mirror derived from this value is estimated to be 0.3. A 120-μm-long monolithically integrated active waveguide when biased as a modulator and excited by the laser shows a maximum extinction ratio of 8 dB and a modulation bandwidth ⩾14 GHz at a dc bias of -0.5 V with a bias swing of 2 V 相似文献