全文获取类型
收费全文 | 11804篇 |
免费 | 1005篇 |
国内免费 | 532篇 |
专业分类
电工技术 | 168篇 |
综合类 | 1005篇 |
化学工业 | 2521篇 |
金属工艺 | 1099篇 |
机械仪表 | 332篇 |
建筑科学 | 2212篇 |
矿业工程 | 271篇 |
能源动力 | 224篇 |
轻工业 | 454篇 |
水利工程 | 339篇 |
石油天然气 | 395篇 |
武器工业 | 200篇 |
无线电 | 1522篇 |
一般工业技术 | 1701篇 |
冶金工业 | 528篇 |
原子能技术 | 135篇 |
自动化技术 | 235篇 |
出版年
2024年 | 19篇 |
2023年 | 141篇 |
2022年 | 235篇 |
2021年 | 297篇 |
2020年 | 342篇 |
2019年 | 262篇 |
2018年 | 228篇 |
2017年 | 349篇 |
2016年 | 324篇 |
2015年 | 388篇 |
2014年 | 556篇 |
2013年 | 744篇 |
2012年 | 718篇 |
2011年 | 787篇 |
2010年 | 684篇 |
2009年 | 673篇 |
2008年 | 632篇 |
2007年 | 866篇 |
2006年 | 826篇 |
2005年 | 711篇 |
2004年 | 634篇 |
2003年 | 504篇 |
2002年 | 439篇 |
2001年 | 367篇 |
2000年 | 296篇 |
1999年 | 239篇 |
1998年 | 178篇 |
1997年 | 163篇 |
1996年 | 132篇 |
1995年 | 120篇 |
1994年 | 99篇 |
1993年 | 86篇 |
1992年 | 68篇 |
1991年 | 50篇 |
1990年 | 47篇 |
1989年 | 41篇 |
1988年 | 25篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
51.
52.
L.N. Koltunova 《Chemical Engineering Communications》1992,114(1):1-15
Methods of obtaining averaged diffusion equations are considered in case of non-uniform profile of the velocity in a channel. With the flow of Couette as an example, the comparison of exact and approximate solutions (obtained by means of perturbation method) has been carried out. The peculiarities of function of residence time distribution of liquid in the flows with non-uniform velocity field are noted. It is shown that the distribution function moments values including the zero and first moments values would depend on the degree of the velocity profile irregularity, on efficiency of radial mixing in a system as well as on the averaging method. The averaged diffusion equations which have been found by means of perturbation method are the most general of proposed ones at present in the appropriate literature. The Taylor's model and Goldstein's hyperbolic equations are included in said averaged equations as particular cases. The table of the numerical values of first three moments of RTD-function necessary for determining of the model parameters is given. The problems of application of the obtained averaged equation for calculating real chemical apparatuses, e.g. reactors, are discussed. 相似文献
53.
北京火车站抗震鉴定与加固技术 总被引:5,自引:3,他引:2
北京火车站抗震加固与改造设计项目组 《工程抗震与加固改造》2003,(1):25-29
北京火车站是首都重要的标志性建筑之一 ,195 9年建成 ,当时按 7度设防考虑 ,存在着许多不符合抗震要求的问题 ,一些设施也明显不能满足现代使用功能要求。北京火车站抗震加固与改造设计项目组 ,运用多种先进的加固手段 ,在保持原建筑外貌不变的前提下 ,实现了抗震能力和改善使用功能的协调 ,取得了大型公共建筑加固改造的新经验 相似文献
54.
Yilmaz Muslu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1991,51(4):449-460
A dispersed flow model previously developed to study substrate utilization in unsaturated media was experimentally verified and its practical application was considered. For this purpose, measurements were made using tap water and a synthetic feed solution. The importance of the change in fluid regime as regards to the simultaneous transport and reaction within biological filters were demonstrated. The effect of drop formation and the breakage of liquid jets inside the filters on substrate utilization was also shown. 相似文献
55.
The effect of adsorption on the measurement of diffusion coefficients by the Taylor dispersion technique is investigated by modifying the governing equation to account for reversible, nonequilibrium adsorption. The resulting two-dimensional equations are solved by an explicit finite-difference technique. Experimental data for the acridine carbon dioxide system indicated that acridine adsorbs on the walls on the tubing and these data were investigated with this model. The influence of carious parameters including the number of sites and the rates of adsorption desorption was investigated by conducting a parametric sensitivity analysis on the model. It was found that adsorption of the solute on the wall of the tubing could produce an error as high as 35% on the measured diffusion coefficient compared to the actual diffusion coellicient. Examination of the influence of each of the parameters will enable Inure investigators to reduce the effect of adsorption in the measurement of diffusion coefficients by Taylor dispersion. 相似文献
56.
A two-dimensional cross-section finite difference model is presented to simulate density dependent leachate migration in leaky aquifers. Unlike existing models, a new approach is adopted to couple the groundwater-flow equation and the hydrodynamic dispersion equation with the elimination of the intermediate step of calculating velocities. The concept of the reference density is employed, permitting increased accuracy (over pressure-based models) in the representation of the transport process. The model is then used to study the effect of several hydraulic and transport parameters on the flow pattern and plume migration which are found to be very sensitive to most of these parameters. Equiconcentration and equipotential lines are overlapped to provide a better understanding of the coupling effect. 相似文献
57.
含钇奥氏体基堆焊焊条堆焊层研究 总被引:1,自引:0,他引:1
针对高温、磨损、热疲劳工况下服役零件的失效,研制了一种含稀土元素钇的奥氏体基沉淀强化型堆焊焊条,并对堆焊层组织与性能进行了较系统的研究。 相似文献
58.
通过对桥梁加固技术的研究,讨论了体系转换法和粘贴碳纤维布加固法的具体应用。 相似文献
59.
Mao Ze yu Chen Chang zhi Department of Hydraulic Engineering Tsinghua University Beijing P.R.China 《水动力学研究与进展(B辑)》1999,(3)
1. INTRODUCTIONThesimulationofstreamwatertemperatureissignificantlyimportantforthestudyofnumericalmodelingofrivericeprocesses[1] .Historically,themathematicalmodelingofthetransportandfateofheatinawaterbodyhasbeenthesubjectofextensivestudyforvariousre… 相似文献
60.
利用短周期地脉动推断深层地基S波速度 总被引:3,自引:0,他引:3
从二维随机波场的相关理论出发,提出了如何从短周期地脉动(频率>0.5Hz)时域信号中计算Rayleigh波弥散曲线,进而反演深层地基剪切波(S波)速度的理论方法和分析技术,并结合实测信号的分析结果,探讨了该方法的可行性和实用性。 相似文献