全文获取类型
收费全文 | 704314篇 |
免费 | 9161篇 |
国内免费 | 2106篇 |
专业分类
电工技术 | 12993篇 |
综合类 | 671篇 |
化学工业 | 105325篇 |
金属工艺 | 26707篇 |
机械仪表 | 20458篇 |
建筑科学 | 17379篇 |
矿业工程 | 2942篇 |
能源动力 | 19773篇 |
轻工业 | 61412篇 |
水利工程 | 6798篇 |
石油天然气 | 11415篇 |
武器工业 | 45篇 |
无线电 | 83402篇 |
一般工业技术 | 137166篇 |
冶金工业 | 136481篇 |
原子能技术 | 13872篇 |
自动化技术 | 58742篇 |
出版年
2022年 | 4170篇 |
2021年 | 6383篇 |
2020年 | 4665篇 |
2019年 | 5896篇 |
2018年 | 10044篇 |
2017年 | 9863篇 |
2016年 | 10358篇 |
2015年 | 7115篇 |
2014年 | 11930篇 |
2013年 | 32576篇 |
2012年 | 18854篇 |
2011年 | 26072篇 |
2010年 | 20636篇 |
2009年 | 23290篇 |
2008年 | 23923篇 |
2007年 | 23500篇 |
2006年 | 20651篇 |
2005年 | 18565篇 |
2004年 | 17961篇 |
2003年 | 17839篇 |
2002年 | 16892篇 |
2001年 | 17272篇 |
2000年 | 16019篇 |
1999年 | 16973篇 |
1998年 | 43433篇 |
1997年 | 30405篇 |
1996年 | 23339篇 |
1995年 | 17588篇 |
1994年 | 15367篇 |
1993年 | 15150篇 |
1992年 | 10899篇 |
1991年 | 10360篇 |
1990年 | 10107篇 |
1989年 | 9678篇 |
1988年 | 9120篇 |
1987年 | 8027篇 |
1986年 | 7874篇 |
1985年 | 8718篇 |
1984年 | 8137篇 |
1983年 | 7388篇 |
1982年 | 6920篇 |
1981年 | 6893篇 |
1980年 | 6632篇 |
1979年 | 6379篇 |
1978年 | 6047篇 |
1977年 | 7351篇 |
1976年 | 9736篇 |
1975年 | 5149篇 |
1974年 | 4904篇 |
1973年 | 4947篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
M. A. Lotonov 《Measurement Techniques》1996,39(10):995-998
We obtain expressions for biased estimates for parameters of binomial distributions with allowance fora priori information; our starting poins is the Rao-Kramer inequality.
Translated from Izmeritel'naya Tekhnika, No. 10, pp. 14–16, October, 1996. 相似文献
993.
The author studies dynamic scheduling of computational tasks with communication costs using nonuniform memory access architecture. The computing model assumes that data transfer can be partitioned into parallel and sequential parts with respect to the task execution. A scheduling heuristic, called least-communication (LC), together with a two-level scheduler is proposed in an attempt to minimize the finish time. The LC selects the task that removes the largest amount of remaining data transfer, if no such tasks are available the task that has been ready to run at the earliest is selected first. The time complexity of LC is O(n 2). Testing the finish time of LC and first-come first-served scheduling (FCFS) shows that LC is useful for tasks having moderate granularity and whose computation and communication requirements vary widely for different data sets 相似文献
994.
995.
Munro A. Guelen E. Deguine M. Melpignano G. Martinez A. 《Communications Magazine, IEEE》1998,36(2):118-126
The ACTS program is moving the results of the R&D of the parent RACE program nearer to realization through technology and user trials. Particularly in the mobile domain of ACTS, several projects have been investigating the user dimension in the context of the third-generation Universal Mobile Telecommunications Service. Results so far suggest many opportunities to broaden participation, exploit the inherent benefits of the mobile environment, and take advantage of the enormous improvements in wireless communications to realize the potential of global multimedia mobility. This article considers the needs of users for mobile multimedia applications and the consequences of those needs on the equipment, supporting services and teleservices, and communications bearers 相似文献
996.
Mita T. Hirata M. Murata K. Zhang H. 《Industrial Electronics, IEEE Transactions on》1998,45(3):488-495
In the motion control field, a disturbance observer-based disturbance canceling control is often used as a robust control methodology. However, this method is nothing more than an alternative design of an integral controller, and the robust stability issue cannot be directly accounted for. In this paper, an extended H∞ control scheme is proposed as a new robust motion control method which achieves the disturbance cancellation ability and guarantees robust stability automatically 相似文献
997.
Significative enhancement of free radical formation (FRO) in vivo is an important feature of hypertensive disorders of pregnancy (HDP), namely preeclampsia (PIH). The latest investigations about the pathology of HDP, showed the contribution of placental circulation to the development and evolution of such disease. The placental bed can be a potential source of FRO or activation of cells that can produce FRO. Glutathione, is an important molecule for cellular protection against damage, is a cofactor of many enzymes, in particular, for the glutathione peroxidase of the placental tissue; this enzyme in the placenta bed prevent the production of thromboxan and lipoperoxides; the latter are potentially damaging to the endothelium cells and can cause vasoconstriction, the most important feature of PIH. The activity of that enzyme is deficient in PIH. We studied, by fluorometric assay, the concentrations of the two states of glutathione in placental homogenates (PLH) from pregnant women without pathology (PWN) and from pregnant women with PIH (PWPIH). The data showed significant low concentrations in the PLH of the two states of glutathione in the PWN against high concentrations of this molecule in the PLH from PWPIH. This feature can result from a deficient user of the glutathione by the cellular mechanism for prevention against oxidative factors. In addition, our study shows a biochemical marker that is suggestive that the placental bed is a potential source of FRO production in PIH. 相似文献
998.
Bondyopadhyay P.K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1998,86(1):63-77
The junction transistor, technologically the most important solid-state device, invented theoretically by W.B. Shockley on January 23, 1948, brought about the semiconductor revolution. That invention was triggered by the experimental discovery of the point-contact transistor by W. Brattain and J. Bardeen 38 days earlier. Bardeen's notebook entries at Bell Telephone Laboratories for the crucial 100-day period November 21, 1947-February 29, 1948 have been examined to ascertain why this winner of two Nobel Prizes in physics could not invent the junction transistor. It was found that the boundary between the thin p-type inversion layer and the n-type bulk germanium semiconductor in their original point-contact transistor discovery was characterized as a “high resistance boundary” in macroscopic electrical engineering terms by Bardeen, the electrical engineer turned mathematical physicist. Pages from Shockley's notebook are reproduced in full to show what exactly he was thinking on December 16, 1947, the day the point-contact transistor was experimentally discovered by Brattain and Bardeen. The origin of U.S. Patent 2524035 has been traced to the Bell Telephone Laboratories notebook pages of its inventors and examined. It is shown that this patent could not be considered as the first patent describing Shockley's revolutionary theoretical invention of the minority carrier injection concept underlying bipolar transistor action 相似文献
999.
Germanovix W. O'Neill G. Toumazou C. Drakakis F.M. Kitney R.I. Lande T.S. 《Electronics letters》1998,34(11):1051-1052
A micropower tone-control circuit comprising two first-order log-domain filters and a subtractor built with MOS transistors in weak inversion is described. The tone-controller is capable of providing bass cut/boost and treble cut operations. This circuit is being used in new designs of a conventional (acoustic) hearing-aid and cochlear implant 相似文献
1000.
The first VLSI digital signal processor that performs both high-precision image backprojection and spatial histogram calculations at raster-scan rates as high as 30 MHz is described. Realized in 1 μm CMOS technology, this 13.3 mm×13.3 mm chip is designed to handle images as large as 1024×1024 12 b pixels. Loadable coefficients and a unified architecture allow this IC to be used with a variety of computed-tomography scanners for image reconstructions, including fan- and parallel-beam reconstruction. This chip also computes the forward Radon transform, which is a spatial histogram, permitting it to be used for iterative reconstruction algorithms. The bit lengths in the fixed-point architecture assure 12 b reconstruction accuracy 相似文献