全文获取类型
收费全文 | 784篇 |
免费 | 34篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 189篇 |
金属工艺 | 45篇 |
机械仪表 | 43篇 |
建筑科学 | 16篇 |
能源动力 | 43篇 |
轻工业 | 73篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 48篇 |
一般工业技术 | 174篇 |
冶金工业 | 70篇 |
原子能技术 | 12篇 |
自动化技术 | 90篇 |
出版年
2023年 | 13篇 |
2022年 | 17篇 |
2021年 | 18篇 |
2020年 | 22篇 |
2019年 | 16篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 29篇 |
2015年 | 25篇 |
2014年 | 30篇 |
2013年 | 64篇 |
2012年 | 40篇 |
2011年 | 44篇 |
2010年 | 34篇 |
2009年 | 33篇 |
2008年 | 30篇 |
2007年 | 19篇 |
2006年 | 33篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 13篇 |
2002年 | 24篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 23篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有821条查询结果,搜索用时 15 毫秒
91.
An analytical method, based on the concept of shock wave formation in the bearing clearance, is used to develop a mathematical model by which the pressure distribution along the fluid film can be predicted. Based on this model, the limiting conditions for shock free operation are determined. The effects of recess geometry and inlet gas conditions are analysed. Experimental pressure distributions along the fluid film at different values of film thickness, supply pressure and rotating speed compare well with the theory. The analysis reveals that a bearing with a tapered recess has a higher resistance to shock wave formation than a conventional bearing having the same recess volume. Moreover, the tapered recess bearing has superior stability to the conventional bearing for the same recess depth. 相似文献
92.
93.
Said S. Ibrahim Ferial M. Abu Salem M. A. Abdallah 《Molecular nutrition & food research》1975,19(3):207-211
In this study processed mango juice was packed in four types of containers and stored at different temperatures for 16 weeks through which furfural level determination and organoleptic assessment were conducted. The experiment revealed an evident relationship to exist among furfural level, storage temperature and type of packing material. Furfural level failed to closely parallel flavour difference; therefore it could be regarded as one of the features concomitant juice aging rather than accepted as a satisfactory criterion of off flavour. The study relates flavour deterioration to the changes in the lipid fraction of the juice. 相似文献
94.
Abou-Zeid A. Abou-Zeid Abd El-Wahab I. Eissa Hassan M. Salem 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1976,26(6):318-322
Production of gentamicin antibiotics by Micromonospora purpurea was carried out successfully on a synthetic medium which contained the following ingredients (g/litre): glucose 10.0, NaNO3 2.0, KH2PO4 1.0, and CaCO3 1.0. The initial pH value of the fermentation medium was adjusted to 7.2. Effects of certain amino acids, organic acids, vitamins, purine and pyrimidine bases on the fermentative production of gentamicins were revealed. The ingredients which increased the antibiotic yields were phenylalanine, isoleucine, lysine, methionine, leucine, arginine, glycine, β′-alanine, cystine, tryptophan, malic acid, maleic acid, cobalamin, folic acid, riboflavin, vitamin B1, vitamin B6, biotin, nicotinamide, uracil, adenine, guanine and adenosine. Trace elements (Co, Mo, Fe, Cu, Zn and Mn) exhibited their important role on the biosynthesis and formation of gentamicins by Micromonospora purpurea. 相似文献
95.
96.
Heat transfer from five horizontal copper plates with different surface finish to boiling refrigerants R11 (CFCI3) and R115 (C2F5Cl) was measured at saturation pressures between 0.4 and 91% of the critical pressure. Although the relative pressure dependence of the heat transfer coefficient α is similar for the plates with different surface treatment, a detailed comparison of the experimental results shows that the influence of the different surface conditions achieved by mechanical and chemical treatment on the absolute value of α cannot be correlated by one of the roughness parameters used in the literature, within the whole range of pressures investigated. 相似文献
97.
Titanium substrates were ion plated with aluminium, producing under certain conditions a graded interface 5 μm deep. The graded interface consists of a solid solution of aluminium in titanium together with TiAl3. The solid solution has a near perfect hexagonal close-packed structure and the hardness of the interface is about 850 VHN. The combination of increased hardness and modified structure results in low friction coefficients and wear rates, and the ion-plated aluminium film provides excellent corrosion resistance. Thus the method has immense practical application in preventing seizure and corrosion in aircraft fasteners. 相似文献
98.
S.A.L. Salem S.T.S. Al-Hassani W. Johnson 《International Journal of Mechanical Sciences》1975,17(3):211-225
For nail driving, some aspects of the effect on penetration of the hammer mass, the speed at impact, the nail size and section shape and the driving direction in relation to the wood grain are reported.A 6 in. long, 0·236 in. dia., round nail was strain gauged to show how the strain in the nail varies with time during an impact.An analysis, which reasonably accounts for the experimental results, is developed for predicting the strain pulse in the nail, the amount of penetration by the nail and its time under strain.Maintaining the same kinetic energy input at each blow, it is found that the larger the initial penetration, the smaller is the further penetration.The effect on penetration depth of the material backing to the piece of wood is reported.The variation of the Euler buckling load with the nail penetration for a specific type of wood and nail dimensions is given. 相似文献
99.
When the cost of reducing the duration of activities is convex and nonlinear, it may be advisable (to reduce the computing burden) to seek a “satisficing” answer, in which the project is compressed to a desired completion time with a prespecified tolerable relative error. We treat the problem of constructing the optimal first degree interpolating linear spline that guarantees such maximal error and consider various possible refinements. 相似文献
100.
The sugars in the dried Iraqi figs (Wazeri Variety) were examined by paper chromatographic analysis. Glucose comprised (34.30%), and fructose (31.20%) together with (7.82 %) of the fruit. Polysaccharides were found to be arabogalactans. Iron, calcium and phosphorus were found to be 14, 145 and 150 mg per 100 g dry weight respectively. Hydrolysis showed the presence of all the essential amino acids with adequate lysin and sulphur amino acids but relatively little tryptophan. 相似文献