全文获取类型
收费全文 | 493篇 |
免费 | 12篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 86篇 |
金属工艺 | 6篇 |
机械仪表 | 9篇 |
建筑科学 | 11篇 |
能源动力 | 24篇 |
轻工业 | 29篇 |
水利工程 | 18篇 |
无线电 | 53篇 |
一般工业技术 | 119篇 |
冶金工业 | 64篇 |
自动化技术 | 83篇 |
出版年
2023年 | 13篇 |
2022年 | 9篇 |
2021年 | 25篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 27篇 |
2017年 | 20篇 |
2016年 | 18篇 |
2015年 | 6篇 |
2014年 | 18篇 |
2013年 | 27篇 |
2012年 | 16篇 |
2011年 | 30篇 |
2010年 | 18篇 |
2009年 | 21篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 16篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 3篇 |
排序方式: 共有506条查询结果,搜索用时 15 毫秒
51.
The Konan groundwater basin of Kochi Prefecture, Japan, is experiencing freshwater shortages for the past few years, particularly during the winter season. The present study aimed at analyzing the problem and exploring increased groundwater withdrawals to meet burgeoning freshwater demands in various sectors. The trend analysis of waterconsumption indicates that the groundwater demandwould increase by 43 and 52% by the years 2010 and2025, respectively, compared to 32 100 m3 d-1 at present.The streamflow of the Monobe River reduces to a minimumin winter and it shows a decreasing trend in recentyears. The geologic investigation results indicatethat unconfined (phreatic) aquifers comprisingalluvial sand and gravel and/or diluvial silty sandand gravel are dominant, and that the northwestern andwestern portions of the basin have greater potentialfor groundwater. Groundwater flows essentially fromnorth to south into the ocean. Groundwater levelfluctuations over the basin vary appreciably in spaceand time, indicating a wide variation of naturalrecharge. Field observations confirm the hypothesisthat stream-aquifer interaction also significantlycontributes to groundwater recharge, besides therainfall infiltration. Further, the pumping testsresults demonstrate that though the aquifers arelow-yielding, enhanced groundwater withdrawals couldbe possible. The aquifer hydraulic conductivity ischaracterized as high and ranges from 65 to 804 m d-1(mean = 229 m d-1), thereby suggesting great aquiferheterogeneity. Finally, it is concluded that thelong-term sustainability of the scarce groundwaterresource of the Konan basin is doubtful, and that acomprehensive analysis of the groundwater system isessential prior to formulating plans for the futuregroundwater development and management. 相似文献
52.
A Madan M Sluzewski WJ van Rooij CC Tijssen JL Teepen 《Canadian Metallurgical Quarterly》1997,39(11):777-780
Deep cerebral vein thrombosis can present with acute, severe neurological symptoms and may be rapidly fatal as in the 20-year-old woman reported here. Although MRI is superior for establishing the diagnosis, CT is usually the first examination performed in the clinical setting. It is therefore important to recognise certain indicators such as extensive bithalamic low density. These and certain other less specific signs are correlated with the MRI and autopsy findings. 相似文献
53.
In this paper the previous hierarchical optimisation algorithm of Hassan and Singh for non-linear interconnected dynamical systems with separable cost functions is extended to the case of non-linear and non-separable cost functions. This ensures that any decomposition could be used and makes the new algorithm suitable for the optimisation of general non-linear problems. 相似文献
54.
EMK-Messungen mit einer Diffusionszelle an flüssigen Schlacken der Systeme CaO–Al2O3 und CaO–SiO2 bei 1600°C. EMK und Sulfidkapazität zeigen lineare Abhängigkeit. EMK-Werte können als relatives Basizitätsmaß gewertet werden. 相似文献
55.
56.
The layered compound, FeOCl is known to form stable intercalates with a large number of organic molecules. When the isostructural γ-FeOOH is treated with organic bases at temperatures of 120–140°C, it is quantitatively converted to the topotactically related γ-Fe2O3. The first step in this base assisted dehydration is presumed to be an intercalation. The second and possibly faster step could be a sequential elimination of water from the interlayer, the role of the base being catalytic. Slightly impure samples of γ-FeOOH that contain a small (5%) amount of α-FeOOH are transformed quantitatively into α-Fe2O3 under the above conditions but pure α-FeOOH is unaffected. A possible rationale for this observation is given. 相似文献
57.
Calcium pyrophosphate dihydrate crystals, which are responsible for various arthritic diseases, were grown in sodium metasilicate
gel. Variations in gel density, pH value and concentration of the reactants were found to have profound effect on the growth
of the crystals. The grown crystals were characterized using IR, XRD, TGA and optical microscopy. 相似文献
58.
Erörterungen zur homogenen Keimbildung und zur Berechnung der kritischen Übersättigung bei der Desoxidation von Eisenschmelzen mit Mangan. Behandlung des Wachstums der Desoxidationsprodukte durch Diffusion und Kollision. Aussagen über die zeitliche Verteilung der Desoxidationsprodukte unter Berücksichtigung von Stokes- und Gradient-Kollision. Angaben über die Bedeutung der Grenzflächenspannung zwischen Schmelze und Einschluß für die Abscheidung der Desoxidationsprodukte. 相似文献
59.
DR Smith P Richterich M Rubenfield PW Rice C Butler HM Lee S Kirst K Gundersen K Abendschan Q Xu M Chung C Deloughery T Aldredge J Maher R Lundstrom C Tulig K Falls J Imrich D Torrey M Engelstein G Breton D Madan R Nietupski B Seitz S Connelly S McDougall H Safer R Gibson L Doucette-Stamm K Eiglmeier S Bergh ST Cole K Robison L Richterich J Johnson GM Church JI Mao 《Canadian Metallurgical Quarterly》1997,7(8):802-819
The nucleotide sequence of 1.5 Mb of genomic DNA from Mycobacterium leprae was determined using computer-assisted multiplex sequencing technology. This brings the 2.8-Mb M. leprae genome sequence to approximately 66% completion. The sequences, derived from 43 recombinant cosmids, contain 1046 putative protein-coding genes, 44 repetitive regions, 3 tRNAs, and 15 tRNAs. The gene density of one per 1.4 kb is slightly lower than that of Mycoplasma (1.2 kb). Of the protein coding genes, 44% have significant matches to genes with well-defined functions. Comparison of 1157 M. leprae and 1564 Mycobacterium tuberculosis proteins shows a complex mosaic of homologous genomic blocks with up to 22 adjacent proteins in conserved map order. Matches to known enzymatic, antigenic, membrane, cell wall, cell division, multidrug resistance, and virulence proteins suggest therapeutic and vaccine targets. Unusual features of the M. leprae genome include large polyketide synthase (pks) operons, inteins, and highly fragmented pseudogenes. 相似文献
60.
The present work undertakes the preparation and physico-chemical characterisation of iron promoted sulphated zirconia (SZ) with different amounts of iron loading and their application to Friedel–Crafts benzoylation of benzene, toluene and xylene under different experimental conditions. XRD and laser Raman techniques reveal the stabilisation of the tetragonal phase of zirconia and the existence of iron in highly dispersed form as Fe2O3 on the catalyst surface. The surface acidic properties were determined by ammonia temperature programmed desorption (TPD) and perylene adsorption. The results were supported by the TGA studies after adsorption of pyridine and 2,6-dimethylpyridine (2,6-DMP). Strong Lewis acid sites on the surface, which are evident from TPD and perylene adsorption studies, explain the high catalytic activity of the systems towards benzoylation. The experimental results provide evidence for the truly heterogeneous nature of the reaction. The studies also establish the resistance to deactivation in the metal incorporated sulphated systems. 相似文献