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891.
The application of focused ion beam instrumentation in the generation of three-dimensional microstructural data is described. The methodologies used to acquire and manipulate this data are explained, and the technique is illustrated by a number of examples from the material sciences. The limitations of this method, and practical pointers to the generation of meaningful data, are also discussed. 相似文献
892.
Ciriello VM 《Applied ergonomics》2007,38(1):1-5
In the development of our present manual materials handling (MMH) guidelines (Snook, S.H., Ciriello, V.M., 1991. The design of manual tasks: revised tables of maximum acceptable weights and forces. Ergonomics 34, 1197-1213), the assumption was made that the effects of frequency on maximum acceptable weights (MAWs) of lifting with a large box (hand distance, 38 cm from chest) were similar to that of lifting with a small box (hand distance, 17 cm from chest). The first purpose of the present experiment was to investigate this assumption with female industrial workers. The second purpose was to study the effects of extended horizontal reach lifting (hand distance, 44.6 cm from chest) on MAWs as a confirmation of the results of a previous studies on this variable with males (Ciriello, V.M., Snook, S.H., Hughes, G.J., 1993. Further studies of psychophysically determined maximum acceptable weights and forces. Hum. Factors 35(1), 175-186; Ciriello, V.M., 2003. The effects of box size, frequency, and extended horizontal reach on maximum acceptable weights of lifting. Int. J. Ind. Ergon. 32, 115-120). Lastly, we studied the effects of high frequency (20 lifts/min) on MAWs of lifting. Ten female industrial workers performed 15 variations of lifting using our psychophysical methodology whereby the subjects were asked to select a workload they could sustain for 8h without "straining themselves or without becoming unusually tired weakened, overheated or out of breath". The results confirmed that MAWs of lifting with the large box was significantly effected by frequency. The frequency factor pattern in this study was similar to the frequency pattern from a previous study using the small box (Ciriello, V.M., Snook, S.H., 1983. A study of size distance height, and frequency effects on manual handling tasks. Hum. Factors 25(5), 473-483) for all fast frequencies down to one lift every 2 min with deviations of 7%, 15%, and 13% for the one lift every 5 and 30 min tasks and the one lift in 8h task, respectively. The effects of lifting with an extended horizontal reach decreased MAW 22% and 18% for the mid and center lift and the effects of the 20 lifts/min frequency resulted in a MAW that was 47% of a 1 lift/min MAW. Incorporating these results in future guidelines should improve the design of MMH tasks for female workers. 相似文献
893.
Controlled calcination of Texas montmorillonite has allowed production of a range of materials of cation exchange capacity from 70 mequiv./100 g dry clay to virtually zero. Pillaring of these with Chlorhydrol precursor solution has then provided a family of materials of pillar density ranging from about one per six unit cells to zero. The analytical technique based on isomorphous metal dilution (IMD) that follows pillaring is validated. The results provide a consistent value for the precursor (Keggin) ion charge, in the conditions normally used, of 3.15±0.10 rather than the formal value of 7. An approach to the attainment of pillar densities consistent with the introduction of shape/size selectivity on pillared layered materials is outlined. 相似文献
894.
Calculating soil nutrient balances in Africa at different scales 总被引:6,自引:3,他引:3
E. M. A. Smaling J. J. Stoorvogel P. N. Windmeijer 《Nutrient Cycling in Agroecosystems》1993,35(3):237-250
Nutrient balances were calculated for the arable soils of 38 sub-Saharan African countries. FAO production figures and forecasts for 35 crops for the period 1982–1984 and for 2000 were used to define land use systems, further characterized by fertility input through fertilizers, manure, rain and dust, biological N-fixation, and sedimentation, and fertility output through harvest of crops and removal of residues, leaching, denitrification, and erosion. The summarized output of the study is the sum of inputs minus the sum of outputs of nitrogen, phosphorus and potassium in the root zone. The alarming annual average nutrient loss for sub-Saharan Africa was 22 kg N, 2.5 kg P, and 15 kg K in 1982–84, and will be 26 kg N, 3 kg P, and 19 kg K in 2000. As the soil nutrient pool has to offset the negative balances each year, there is gross nutrient mining in sub-Saharan Africa. The need for integrated systems of nutrient management is emphasized, manipulating all inputs and outputs in a judicious way. Future scenarios of continued mining and conservation of soil fertility are discussed. 相似文献
895.
896.
897.
Novel Ultrahigh-Energy Materials 总被引:3,自引:0,他引:3
M. B. Talawar R. Sivabalan S. N. Asthana H. Singh 《Combustion, Explosion, and Shock Waves》2005,41(3):264-277
This paper reviews the recent work carried out in the field of modern high-energy materials (HEMs) with the emphasis on homoleptic polynitrogen compounds. A large volume of quantum-chemical investigations have predicted the possibility of existence of polynitrogen compounds not only as short-lived transient species but also in the form of isolable discrete molecules. Despite the theoretical speculations, only a few polynitrogen ions are known today in addition to well-entrenched N
1–
3
discovered almost 100 year ago. Extraordinary potential of these green molecules to deliver high amounts of energy in comparison with todays and tomorrows most powerful HEMs, namely, hexanitrohexaazaisowurtzitane (CL-20) and octanitrocubane (ONC), has fuelled the imagination of propellant and explosive engineers and technologists. Research activities are in progress in many quantum-chemical schools to explore the possibility of other promising polynitrogen compounds. After the recent discovery of key synthons/building blocks Mg(N5)2, N
1+
5
SbF
1–
6
, N
1+
5
SbF11, N
1+
5
, N
1+
5
SnF6, and N
1+
5
Sn(CF3)4, the wealth of polynitrogen compounds is just waiting to be harvested by the HEMs community. There are ambitious plans all over the globe to realize N60, which only prove a eco-friendly dense powerhouse of energy.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 3, pp. 29–45, May–June, 2005. 相似文献
898.
汽车用涂装材料的现状及发展 总被引:1,自引:0,他引:1
介绍了我国汽车用涂装材料市场的变化,以及国内外车用涂料现状,并对汽车涂装材料的发展趋势进行了分析. 相似文献
899.
刘培飞 《化学工业与工程技术》2002,23(3):19-20
根据材质的价位与寿命以及磷酸生产厂家使用情况的统计 ,并结合我厂使用的结果 ,应合理分类与合理选用合金材料。萃取槽搅拌桨、料浆泵过流部件选用Cr30。滤洗液泵、磷酸泵、轴流泵等过流部件选用CD - 4MCu。而 941在常温下耐各种浓度的硫酸 ,并具有较好的焊接性能 ,故硫酸泵过流部件用材选择 941。 相似文献
900.
本文为石化排污管道的设计进行分析与选材,提出采用玻璃钢管道,并对其树脂基体材料和纤维增强材料的选取进行了分析与选择。 相似文献