全文获取类型
收费全文 | 9414篇 |
免费 | 539篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 64篇 |
综合类 | 3篇 |
化学工业 | 2117篇 |
金属工艺 | 126篇 |
机械仪表 | 161篇 |
建筑科学 | 307篇 |
矿业工程 | 14篇 |
能源动力 | 244篇 |
轻工业 | 1853篇 |
水利工程 | 101篇 |
石油天然气 | 26篇 |
无线电 | 417篇 |
一般工业技术 | 1389篇 |
冶金工业 | 1497篇 |
原子能技术 | 31篇 |
自动化技术 | 1614篇 |
出版年
2024年 | 13篇 |
2023年 | 88篇 |
2022年 | 204篇 |
2021年 | 337篇 |
2020年 | 229篇 |
2019年 | 290篇 |
2018年 | 355篇 |
2017年 | 339篇 |
2016年 | 386篇 |
2015年 | 293篇 |
2014年 | 423篇 |
2013年 | 776篇 |
2012年 | 620篇 |
2011年 | 663篇 |
2010年 | 473篇 |
2009年 | 459篇 |
2008年 | 431篇 |
2007年 | 418篇 |
2006年 | 248篇 |
2005年 | 224篇 |
2004年 | 228篇 |
2003年 | 185篇 |
2002年 | 182篇 |
2001年 | 120篇 |
2000年 | 107篇 |
1999年 | 121篇 |
1998年 | 589篇 |
1997年 | 333篇 |
1996年 | 216篇 |
1995年 | 118篇 |
1994年 | 96篇 |
1993年 | 88篇 |
1992年 | 31篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 27篇 |
1987年 | 15篇 |
1986年 | 13篇 |
1985年 | 26篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 26篇 |
1976年 | 30篇 |
1975年 | 3篇 |
排序方式: 共有9964条查询结果,搜索用时 9 毫秒
21.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献
22.
M Tuena de Gómez-Puyou F Sandoval JJ García A Gómez-Puyou 《Canadian Metallurgical Quarterly》1998,255(1):303-308
Soluble mitochondrial F1 and F1 in complex with the natural ATPase inhibitor protein (F1-IP) catalyze the spontaneous synthesis of [gamma-32P]ATP from medium [32P]phosphate and enzyme-bound ADP when incubated in media with dimethylsulfoxide (Me2SO); under these conditions, the synthesized [gamma-32P]ATP is not released into the media, it remains tightly bound to the enzymes [Gómez-Puyou, A., Tuena de Gómez-Puyou, M. & de Meis, L. (1986) Eur. J. Biochem. 159, 133-140]. Some of the characteristics of the synthesized [gamma-32P]ATP were studied in F1 and F1-IP (ATPase activities of 70 and 1-3 micromol x min(-1) x mg(-1), respectively). In Me2SO media, gamma-phosphate of synthesized ATP in F1 or F1-IP exchanges with medium phosphate. From the rates of the exchange reaction, the half-times for hydrolysis of the synthesized ATP in F1 and F1-IP were calculated: 45 min and 58 min for F1 and F1-IP, respectively. The course that synthesized [gamma-32P]ATP follows after dilution of the Me2SO synthetic mixture with aqueous buffer was determined. After dilution, the half-life of synthesized ATP in F1 was less than 1 min. In F1-IP, ATP was also hydrolyzed, but at significantly lower rates. In F1-IP, dilution also produced release of the synthesized [gamma-32P]ATP. This was assayed by the accessibility of [gamma-32P]ATP to hexokinase. About 25% of [gamma-32P]ATP synthesized in F1-IP, but not in F1, was released into the media after dilution with aqueous buffer that contained 20 mM phosphate. Release of tightly bound ATP required the binding energy of phosphate and solvation of F1-IP, however, the particular kinetics of F1-IP were also central for medium ATP synthesis in the absence of electrochemical H+ gradients. 相似文献
23.
24.
25.
BACKGROUND: Continent urinary diversion may be necessary in a range of urological abnormalities. In circumstances where the standard techniques are not possible, alternative innovative techniques may be used. METHODS: In a female patient with bladder exstrophy, a continent diversion was recommended. The appendix was not available, the ureters were not suitable and a continent stoma was fashioned from an isolated segment of colon. RESULTS: The stoma proved to be continent, although it was somewhat stenotic. However, clean intermittent catheterization maintained its patency. CONCLUSIONS: A continent catheterizable stoma may be constructed from a segment of colon. The technique may be considered when other well recognized methods are not feasible. 相似文献
26.
AJ Dorta M Ferra R Bu-Colfiu L García M Gil X Escobar G Martín NA Díaz OM Perez MT Interián 《Canadian Metallurgical Quarterly》1993,10(10):490-491
It is essential to know how the immune system acts in different neurological diseases, some of them non very well known or of unknown etiology at all. It was applied Reiber and Felgenhauer's formula in 56 patients with different diseases. IgA, IgM, IgG and albumin were quantified in sera and cerebrospinal fluid by simple immunodiffusion. It was observed more frequent IgG local synthesis and IgA in this sample. 相似文献
27.
28.
29.
Temperature, thermal efficiency, and gradient performance from two seawater-SZ solar ponds 总被引:1,自引:0,他引:1
This paper presents 10 months of experience with two seawater-SZ (Storage Zone) solar ponds operated as a source of warm seawater which could have been used in an adjacent mariculture facility. Observations and extensive temperature, gradient and efficiency data are presented. This work demonstrated operation of and heat extraction from seawater-SZ solar ponds over a much longer interval than in previous work. It confirmed that seawater-SZ solar ponds can consistently give useful temperature elevations. A few phenomena not characteristic of conventional solar ponds were identified and are discussed. 相似文献
30.
Summary Poly(propylene oxide), PPO, obtained using diphenylzinc, Ph2Zn, and using the diphenylzinc-water system at various molar ratios H2O/Ph2Zn, were studied through 1H NMR and IR spectroscopy establishing that the polymerization initiates by coordition of propylene oxide (PO) to a terminal zinc atom of the active species followed by consecutive insertions of PO units at this zinc atom. The PPO obtained showed Ph-and HO-, HO-and HO-end-groups depending on the molar ratio H2O/Ph2Zn used, and also HO-and PhO-end-groups when oxygen was present in the polymerization system. 相似文献