全文获取类型
收费全文 | 6011篇 |
免费 | 187篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 91篇 |
综合类 | 40篇 |
化学工业 | 1641篇 |
金属工艺 | 170篇 |
机械仪表 | 129篇 |
建筑科学 | 345篇 |
矿业工程 | 11篇 |
能源动力 | 95篇 |
轻工业 | 501篇 |
水利工程 | 36篇 |
石油天然气 | 2篇 |
无线电 | 362篇 |
一般工业技术 | 1135篇 |
冶金工业 | 960篇 |
原子能技术 | 64篇 |
自动化技术 | 630篇 |
出版年
2022年 | 65篇 |
2021年 | 85篇 |
2020年 | 54篇 |
2019年 | 74篇 |
2018年 | 90篇 |
2017年 | 80篇 |
2016年 | 117篇 |
2015年 | 103篇 |
2014年 | 148篇 |
2013年 | 278篇 |
2012年 | 220篇 |
2011年 | 314篇 |
2010年 | 219篇 |
2009年 | 206篇 |
2008年 | 254篇 |
2007年 | 249篇 |
2006年 | 185篇 |
2005年 | 193篇 |
2004年 | 160篇 |
2003年 | 135篇 |
2002年 | 135篇 |
2001年 | 129篇 |
2000年 | 122篇 |
1999年 | 128篇 |
1998年 | 220篇 |
1997年 | 160篇 |
1996年 | 125篇 |
1995年 | 123篇 |
1994年 | 106篇 |
1993年 | 101篇 |
1992年 | 89篇 |
1991年 | 83篇 |
1990年 | 91篇 |
1989年 | 64篇 |
1988年 | 70篇 |
1987年 | 73篇 |
1986年 | 59篇 |
1985年 | 76篇 |
1984年 | 76篇 |
1983年 | 64篇 |
1982年 | 63篇 |
1981年 | 58篇 |
1979年 | 55篇 |
1978年 | 58篇 |
1977年 | 87篇 |
1976年 | 77篇 |
1975年 | 50篇 |
1974年 | 61篇 |
1972年 | 46篇 |
1970年 | 45篇 |
排序方式: 共有6212条查询结果,搜索用时 15 毫秒
1.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology. 相似文献
2.
Separation tests using hollow-fibre modules were performed for the difficult selective extraction of trivalent actinides over fission lanthanides from acidic media. This article shows that with 2,6-di(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine as the extractant, up to 94% americium could be extracted from 1.0 kmol/m3 HNO3, with minimal lanthanide co-extraction. Using a synergistic mixture of bis(chlorophenyl)dithiophosphinic acid and tri-n-octyl phosphine oxide, tests were performed on extraction, lanthanide scrubbing and stripping. In the extraction test, up to 99.99% americium could be extracted from 0.5 kmol/m3 HNO3, with approximately one third of the lanthanides being co-extracted. Mass transfer calculations using a consistent set of input data showed good agreement with the experiments. 相似文献
3.
4.
Pyrolysis experiments were performed in high vacuum and under reduced air pressure (100 Pa). The volatile products of pure cellulose and cellulose containing various amounts of flame retardant 2,2′-oxybis (5,5-dimethyl-1,3,2-dioxaphosphorinane-2,2′-disulfide), i.e., Sandoflam 5060 of Sandoz AG, were studied by means of gas chromatography in combination with mass spectroscopy. The volatile products were characterized with infrared spectroscopy. The studied revealed that the incorporation of the flame retardant enhanced the water release and shifted the onset of this reaction to lower temperature. On the basis of these findings an explanation for the mechanism of flame retardancy in generated cellulose fibers modified with this particular flame retardant is attempted. From experiments with different residual air pressure the influence of oxygen on the primary processes of the pyrolytic degradation of cellulose is being discussed. 相似文献
5.
6.
The multi-homogeneous Bezout number is a bound for the number of solutions of a system of multi-homogeneous polynomial equations,
in a suitable product of projective spaces. Given an arbitrary, not necessarily multi-homogeneous, system, one can ask for
the optimal multi-homogenization that would minimize the Bezout number. In this paper it is proved that the problem of computing,
or even estimating, the optimal multi-homogeneous Bezout number is actually NP-hard. In terms of approximation theory for
combinatorial optimization, the problem of computing the best multi-homogeneous structure does not belong to APX, unless P
= NP. Moreover, polynomial-time algorithms for estimating the minimal multi-homogeneous Bezout number up to a fixed factor
cannot exist even in a randomized setting, unless BPP ⫆ NP. 相似文献
7.
The price of SO2 permits and the volume of trading under the US Acid Rain Program have been lower than expected. This can be explained by the creation and distribution of more permits than were initially authorized, by the sale of permits by high cost abaters who are subject to more stringent local emission constraints or who have irreversibly invested in high cost abatement technologies and by the deregulation of the natural gas and railroad industries which, in combination with incentives for cost-cutting under the new market approach to SO2 control, has lowered marginal costs of abatement curves and made them more uniform across powerplants. The low price of permits and low trading volume are evidence that market approaches to pollution control can be more cost-effective than command and control regulations. The effect of public policies and technological changes on the allowance market are usefully examined in the context of an ideal market, in which the equilibrium price of allowances equals the marginal cost of abatement of individual powerplants. Using recent data from Coggins and Swinton (1996), we are able to explain the current price of permits with some accuracy. 相似文献
8.
J Abart K Eberhardt H Fischer W Huk E Richter F Schmitt T Storch B Tomandl E Zeitler 《Canadian Metallurgical Quarterly》1997,21(4):532-538
PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation. 相似文献
9.
Klaus Bauckhage 《化学,工程师,技术》1993,65(10):1200-1205
Utilisation of Different Components of Scattered Light for Particle Size Determination in Dispersed Systems . Light scattered by finely and coarsely dispersed particles can be used in variety of ways for characterization of sprays, emulsions, or suspensions. The characteristic of greatest interest is the particle size or the particle size distribution. While homogeneous, coarsely dispersed particles at sufficient dilutions and randomly distributed in a transparent continuous phase are generally amenable to particle size analysis, finely dispersed particles at higher concentrations or coarsely dispersed particles containing finely dispersed components are often difficult to measure. This article discusses ways of overcoming such difficulties on the basis of examples taken mainly from phase Doppler anemometry. 相似文献
10.
O K?lbl K Bratengeier S Richter R Henkel R Schmidt M Flentje 《Canadian Metallurgical Quarterly》1997,173(10):513-518
PURPOSE: There are different techniques of boost irradiation in the treatment of patients with anal carcinoma. A new system of applicators is presented, which can be used for an intracavitary afterloading therapy. MATERIAL AND METHODS: Three different applicators are available, the first with a central catheter (K1), a second with 5 semicircular fixed catheters (K2) and an eccentric shield, a third with 8 circular fixed catheters and a central shield (K3). RESULTS: The adequate choice of applicator and catheters takes into consideration the individual localisation and extension of anal carcinoma in planning therapy. Thus, in circular growing tumors, an irradiation of the whole circumference of the anal canal is possible. In non-circular growing tumors, the dose applied in the non-affected part of the anal canal can be reduced to a quarter of the dose applied at the tumor. CONCLUSION: The new system of intracavitary afterloading therapy is a good alternative to previous techniques of boost irradiation in the treatment of anal carcinoma. By means of this technique, irradiation can be highly individualized, the tumor better included and non-affected sections of the anal canal saved. 相似文献