全文获取类型
收费全文 | 949篇 |
免费 | 43篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 248篇 |
金属工艺 | 23篇 |
机械仪表 | 27篇 |
建筑科学 | 37篇 |
矿业工程 | 5篇 |
能源动力 | 28篇 |
轻工业 | 77篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 66篇 |
一般工业技术 | 179篇 |
冶金工业 | 122篇 |
原子能技术 | 12篇 |
自动化技术 | 148篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 33篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 24篇 |
2016年 | 28篇 |
2015年 | 34篇 |
2014年 | 29篇 |
2013年 | 57篇 |
2012年 | 48篇 |
2011年 | 63篇 |
2010年 | 39篇 |
2009年 | 36篇 |
2008年 | 56篇 |
2007年 | 36篇 |
2006年 | 34篇 |
2005年 | 19篇 |
2004年 | 17篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 6篇 |
1999年 | 13篇 |
1998年 | 52篇 |
1997年 | 23篇 |
1996年 | 23篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1976年 | 11篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 7篇 |
1970年 | 6篇 |
1967年 | 3篇 |
排序方式: 共有993条查询结果,搜索用时 15 毫秒
951.
952.
953.
René Roscher Andreas Hilkert Martin Gessner Erna Schindler Peter Schreier W. Schwab 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,204(3):198-201
2,5-Dimethyl-4-hydroxy-3[2H]-furanone (Furaneol, 1), an important aroma constituent, was detected at concentrations of up to 2 mg/l after 4 days of growth of Pichia capsulata on casein peptone culture medium containing L-(+)-rhamnose (2). Blank samples without yeast contained no 1 after the incubation period. In parallel experiments five samples of 2 exhibiting different [13C] abundance were given to P. capsulata. The volatile compounds formed were isolated and analysed for their [13C]/[12C] ratios by on-line gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). A positive correlation between
the isotopes in 1 and 2 was observed; thus, 2 served as the carbon source for 1. However, 1 was formed from a postulated intermediate of 2 generated during thermal sterilization, as 1 was neither detected after sterile filtration of the culture medium nor after separate thermal sterilization of the casein
peptone and 2. This observation was confirmed by an experiment investigating the time course of the formation of 1.
Received: 4 June 1996 相似文献
954.
955.
The idea of coding the human voice into digital pulses was conceived more than three decades ago; exploitation had to await the ushering in of the transistor era. Since then, coding systems gradually have improved. One of the latest and most efficient schemes is delta modulation. Compared with earlier analog-to-digital-pulse conversion systems, an increase in the voice-handling capacity of telephone equipment by a factor of two or more has been made possible. At the same time, equipment requirements have become less stringent. 相似文献
956.
Summary In the present paper, the determination of yield locus curves for deep drawing sheet metal is described. The experiments are based on the combination of biaxial tension tests on plane cross-shaped specimens with uniaxial tension and compression tests performed on conventional specimens. The influence of preloading (prestrain) on the hardening behaviour is discussed. The material coefficients are computed through the equalization of the test results by means of a quadratic formulation of the yield condition. Finally, the material coefficients are given as functions of the prestrain of specimens in the rolling direction.With 9 Figures 相似文献
957.
C Nasel K R?ssler K Heimberger H G?rzer H Lassmann E Schindler 《Canadian Metallurgical Quarterly》1997,39(9):627-632
It is possible to underestimate the grade of nonenhancing cerebral tumours on conventional contrast-enhanced MRI or CT. Differentiation of high- and low-grade gliomas by measurement of the brain-blood partition coefficient lambda (T lambda) with Xe-enhanced CT (XeCT) has been reported. We assessed the practical applications of XeCT in suspected low-grade astrocytomas. We examined 15 patients with tumours which showed no contrast enhancement on conventional MRI and CT, using XeCT. Tumour blood flow (TBF) and T lambda were calculated. Fourteen patients underwent surgery, one patient had a biopsy. We recognized three histological groups. While T lambda differed significantly between them, TBF did not. Group 1 contained grade II-III astrocytomas and T lambda was 0.77; group 2 contained grade I-II astrocytomas with T lambda 1.14, and group 3 four oligodendrogliomas in which a T lambda of 1.50 was found. 相似文献
958.
C Schindler U Ackermann-Liebrich P Leuenberger C Monn R Rapp G Bolognini JP Bongard O Br?ndli G Domenighetti W Karrer R Keller TG Medici AP Perruchoud MH Sch?ni JM Tschopp B Villiger JP Zellweger 《Canadian Metallurgical Quarterly》1998,9(4):405-411
Ample experimental evidence indicates that acute beta-amyloid infusion into the nucleus basalis of rats elicits abrupt degeneration of the magnocellular cholinergic neurons projecting to the cerebral cortex. In fact, involvement of a permanent Ca2+ overload, partially via N-methyl-D-aspartate (NMDA) receptors, was proposed as a pivotal mechanism in beta-amyloid-induced neurodegeneration. A definite measure of NMDA receptor-mediated processes and subsequent Ca2+ entry is the induction of Ca2+/calmodulin-activated neuronal nitric oxide synthase (nNOS) in nerve cells. In the present account we therefore assessed activation of nNOS in correlation with cholinergic decline after beta-amyloid(1-42) or beta-amyloid(25-35) infusion into the rat nucleus basalis. The results demonstrate the beta-amyloid conformation-dependent enhancement of cortical nitric oxide synthase (NOS) activity. Furthermore, chronic application of the polyamine site NMDA receptor blocker ifenprodil effectively attenuated beta-amyloid neurotoxicity. We propose that nNOS activation reflects the degree of beta-amyloid-induced excitotoxic injury in a proportional manner. Moreover, Ca2+-mediated processes via NMDA receptors, or direct binding of beta-amyloid to this receptor may be a critical step in the neurotoxic mechanisms in vivo. 相似文献
959.
960.
G. Jerinic J. Fines M. Cobb M. Schindler 《Journal of Infrared, Millimeter and Terahertz Waves》1985,6(2):79-130
GaAs IMPATT diodes are capable of generating 2 to 3 W simultaneously with 18–22% efficiency in the 33 GHz to 46 GHz frequency band. The design of the amplifier circuits which utilize these devices is discussed. The circuit design is based on a 3-step closed form algorithm. The first step is a passive circuit characterization with an automatic network analyzer. In the second step, a computer is used to generate diode device lines. The third step is load line synthesis for predictable operation. The resulting performance is described. 2 W over a 2GHz bandwidth was achieved simultaneously with a minimum gain of 12 dB. 相似文献