全文获取类型
收费全文 | 23307篇 |
免费 | 944篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 343篇 |
综合类 | 24篇 |
化学工业 | 4706篇 |
金属工艺 | 458篇 |
机械仪表 | 500篇 |
建筑科学 | 1142篇 |
矿业工程 | 73篇 |
能源动力 | 740篇 |
轻工业 | 1955篇 |
水利工程 | 140篇 |
石油天然气 | 74篇 |
武器工业 | 1篇 |
无线电 | 2304篇 |
一般工业技术 | 4120篇 |
冶金工业 | 3867篇 |
原子能技术 | 227篇 |
自动化技术 | 3611篇 |
出版年
2023年 | 186篇 |
2022年 | 253篇 |
2021年 | 575篇 |
2020年 | 445篇 |
2019年 | 470篇 |
2018年 | 561篇 |
2017年 | 519篇 |
2016年 | 604篇 |
2015年 | 511篇 |
2014年 | 646篇 |
2013年 | 1423篇 |
2012年 | 1048篇 |
2011年 | 1372篇 |
2010年 | 975篇 |
2009年 | 1030篇 |
2008年 | 1087篇 |
2007年 | 944篇 |
2006年 | 886篇 |
2005年 | 772篇 |
2004年 | 630篇 |
2003年 | 563篇 |
2002年 | 532篇 |
2001年 | 407篇 |
2000年 | 402篇 |
1999年 | 443篇 |
1998年 | 950篇 |
1997年 | 635篇 |
1996年 | 502篇 |
1995年 | 365篇 |
1994年 | 379篇 |
1993年 | 371篇 |
1992年 | 269篇 |
1991年 | 221篇 |
1990年 | 195篇 |
1989年 | 182篇 |
1988年 | 185篇 |
1987年 | 167篇 |
1986年 | 165篇 |
1985年 | 211篇 |
1984年 | 189篇 |
1983年 | 163篇 |
1982年 | 128篇 |
1981年 | 149篇 |
1980年 | 126篇 |
1979年 | 134篇 |
1978年 | 123篇 |
1977年 | 160篇 |
1976年 | 183篇 |
1975年 | 109篇 |
1974年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
21.
22.
Precil Diego M. M. Neves Fernanda M. Freitas Christiane A. Kojima Beatriz L. Carmello Rodrigo Bazan Pasqual Barretti Luis C. Martin 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(1):143-145
Antibiotics are potentially a cause of neurotoxicity in dialysis patients, the most common are the beta‐lactams as ceftazidime and cefepime, and few cases have been reported after piperacillin/tazobactam use. This report presents a case of a hypertensive and diabetic 67‐year‐old woman in regular hemodialysis, which previously had a stroke. She was hospitalized presenting pneumonia, which was initially treated with cefepime. Two days after treatment, she presented dysarthria, left hemiparesis, ataxia, and IX and X cranial nerves paresis. Computed tomography showed no acute lesions and cefepime neurotoxicity was hypothesized, and the antibiotic was replaced by piperacillin/tazobactam. The neurologic signs disappeared; however, 4 days after with piperacillin/tazobactam treatment, the neurological manifestations returned. A new computed tomography showed no new lesions, and the second antibiotic regimen withdrawn. After two hemodialysis sessions, the patient completely recovered from neurological manifestations. The patient presented sequentially neurotoxicity caused by two beta‐lactams antibiotics. This report meant to alert clinicians that these antibiotics have dangerous neurological effects in chronic kidney disease patients. 相似文献
23.
24.
Ole Wiborg Martin O'Connell Richard Thiele Martin Wichert Gunther Kolb 《化学工程与技术》2015,38(8):1308-1314
Many critical issues need to be addressed when microstructured reactors are manufactured in large unit volumes. The most crucial of these are cost, ease of production, and reliability. The lack of breakthrough manufacturing technology to provide high‐efficiency, low‐cost, high‐precision plates is a hindrance to the early market implementation of systems requiring metallic microstructured plates. This contribution focuses on the development and optimization of a combined embossing and bending tool for the quick and continuous manufacture of easily machined plates. 相似文献
25.
This paper introduces a wide-spectrum specification logic νZ. The minimal core logic is extended to a more expressive specification logic which includes a schema calculus similar (but not equivalent) to Z, new additional schema operators, and extensions to programming and program development logics. 相似文献
26.
Frank H. P. Fitzek Martin Reisslein 《International Journal of Communication Systems》2004,17(5):421-435
Video streaming is expected to account for a large portion of the traffic in future networks, including wireless networks. It is widely accepted that the user datagram protocol (UDP) is the preferred transport protocol for video streaming and that the transmission control protocol (TCP) is unsuitable for streaming. The widespread use of UDP, however, has a number of drawbacks, such as unfairness and possible congestion collapse, which are avoided by TCP. In this paper we investigate the use of TCP as the transport layer protocol for streaming video in a multi‐code CDMA cellular wireless system. Our approach is to stabilize the TCP throughput over the wireless links by employing a recently developed simultaneous MAC packet transmission (SMPT) approach at the link layer. We study the capacity, i.e. the number of customers per cell, and the quality of service for streaming video in the uplink direction. Our extensive simulations indicate that streaming over TCP in conjunction with SMPT gives good performance for video encoded in a closed loop, i.e. with rate control. We have also found that TCP is unsuitable (even in conjunction with SMPT) for streaming the more variable open‐loop encoded video. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
27.
Kelson C. Lopes Flvia S. Pereira Regiane C. M. U. Araújo Mozart N. Ramos Roy E. Bruns 《Chemometrics and Intelligent Laboratory Systems》2004,70(2):157-163
Factorial design and principal component models are used to determine how ab initio H-bond stretching frequencies depend on characteristics of the molecular orbital wave functions of acetylene–HX, ethylene–HX and cyclopropane–HX π-type hydrogen complexes with X=F, Cl, CN, NC and CCH. The results obtained for the three sets of complexes show that factorial design and principal component analyses complement each other. Factorial design calculations clearly show that these frequencies are affected mostly by inclusion of electron correlation on the calculation level. On average, their values are increased by about 25 cm−1 due to a change from the Hartree–Fock (HF) to Möller–Plesset 2 (MP2) level. Valence, diffuse and polarization main effects as well as valence–diffuse, diffuse–correlation and polarization–correlation interaction effects are also important to better describe a factorial model to the H-bond stretching frequencies of these hydrogen complexes. This simplified model has been successful in reproducing the complete ab initio results, which correspond to two hundred and forty calculations. Principal component analyses applied only to hydrogen-bonded complexes whose experimental frequencies are known, has revealed that the six-dimensional original space can be accurately represented by a bidimensional space defined by two principal components. Its graphical representation reveals that the experimental intermolecular stretching frequencies are in closest agreement with the MP2/6–31+G and MP2/6–311+G ab initio results. 相似文献
28.
Hannerz Harald; Albertsen Karen; Nielsen Martin Lindhardt; Tüchsen Finn; Burr Hermann 《Canadian Metallurgical Quarterly》2004,23(3):283
This study explored whether factors related to the work environment could predict changes in body mass index (BMI) and whether the effect of psychosocial factors was dependent on baseline BMI. The sample consisted of 1,980 male employees from the Danish National Work Environment Cohort Study. Changes in BMI between 1995 and 2000 were analyzed, by multiple regression, as a function of background variables and a series of occupational variables obtained in 1995. Age, baseline BMI, job insecurity, and psychological demands predicted changes in BMI. Job insecurity and high or low psychological demands increased the likelihood of weight gain among obese employees, whereas they increased the likelihood of weight loss among employees with a low BMI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Martin F. Falcone F. Bonache J. Marques R. Sorolla M. 《Microwave and Wireless Components Letters, IEEE》2003,13(12):511-513
A novel compact stop band filter consisting of a 50 /spl Omega/ coplanar waveguide (CPW) with split ring resonators (SRRs) etched in the back side of the substrate is presented. By aligning SRRs with the slots, a high inductive coupling between line and rings is achieved, with the result of a sharp and narrow rejection band in the vicinity of the resonant frequency of the rings. In order to widen the stop band of the filter, several ring pairs tuned at equally spaced frequencies within the desired gap are cascaded. The frequency response measured in the fabricated prototype device exhibits pronounced slopes at either side of the stop band and near 0 dBs insertion loss outside that band. Since SRR dimensions are much smaller than signal wavelength, the proposed filters are extremely compact and can be used to reject frequency parasitics in CPW structures by simply patterning properly tuned SRRs in the back side metal. Additional advantages are easy fabrication and compatibility with MMIC or PCB technology. 相似文献
30.
Agnieszka M. Wusatowska-Sarnek Martin J. Blackburn Mark Aindow 《Materials Science and Engineering: A》2003,360(1-2):390-395
Methods are described for sample preparation of polycrystalline Ni-based superalloys in order to perform a detailed microstructural characterization. Specific techniques for the precise definition of the various phases present are outlined and these are shown to be useful for the measurement of size, volume fractions and distribution. A number of optical, scanning and transmission microscopy techniques are used to provide the necessary information. 相似文献