全文获取类型
收费全文 | 22177篇 |
免费 | 2628篇 |
国内免费 | 1682篇 |
专业分类
电工技术 | 1351篇 |
综合类 | 2369篇 |
化学工业 | 3651篇 |
金属工艺 | 2047篇 |
机械仪表 | 854篇 |
建筑科学 | 1579篇 |
矿业工程 | 490篇 |
能源动力 | 1498篇 |
轻工业 | 1081篇 |
水利工程 | 626篇 |
石油天然气 | 972篇 |
武器工业 | 166篇 |
无线电 | 2546篇 |
一般工业技术 | 2616篇 |
冶金工业 | 780篇 |
原子能技术 | 505篇 |
自动化技术 | 3356篇 |
出版年
2024年 | 103篇 |
2023年 | 350篇 |
2022年 | 584篇 |
2021年 | 720篇 |
2020年 | 739篇 |
2019年 | 694篇 |
2018年 | 696篇 |
2017年 | 808篇 |
2016年 | 765篇 |
2015年 | 844篇 |
2014年 | 1239篇 |
2013年 | 1701篇 |
2012年 | 1597篇 |
2011年 | 1606篇 |
2010年 | 1271篇 |
2009年 | 1368篇 |
2008年 | 1228篇 |
2007年 | 1411篇 |
2006年 | 1286篇 |
2005年 | 1094篇 |
2004年 | 933篇 |
2003年 | 793篇 |
2002年 | 701篇 |
2001年 | 567篇 |
2000年 | 534篇 |
1999年 | 427篇 |
1998年 | 351篇 |
1997年 | 308篇 |
1996年 | 255篇 |
1995年 | 244篇 |
1994年 | 200篇 |
1993年 | 168篇 |
1992年 | 137篇 |
1991年 | 136篇 |
1990年 | 132篇 |
1989年 | 116篇 |
1988年 | 74篇 |
1987年 | 53篇 |
1986年 | 37篇 |
1985年 | 49篇 |
1984年 | 37篇 |
1983年 | 19篇 |
1982年 | 29篇 |
1981年 | 19篇 |
1980年 | 19篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
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
83.
Bob Eisenberg 《Journal of Computational Electronics》2002,1(3):331-333
Ion channels are proteins with a hole down their middle important in a wide range of biological functions yet simple enough to be analyzed as devices in the engineering tradition. 相似文献
84.
钟蔚 《艺术与设计.数码设计》2007,(7)
通过对中西方服饰的审美文化的探讨,分析服装设计的审美特性和美学意蕴。从全面的、科学的角度来客观评价东西方服饰文化的审美价值。 相似文献
85.
A generalized diffusion coefficient correlation for a binary system of liquids has been developed to represent the data for a wide range of temperatures. Detailed analysis shows that the proposed correlation fits the experimental measurements of diffusivity with the corresponding calculated values with an acceptable percentage error. 相似文献
86.
《Drying Technology》2007,25(7):1275-1280
When using the convective drying method, the mass transfer between drying air and moisture diffusion of the material is very important. The moisture moves inside the material because of the volume change caused by the increased temperature. This movement is additionally affected by the texture of the material. According to the research dealing with colloid capillary porous texture of vegetables and fruit, the humidity migration inside the material occurs in both fluid and steam condition at the same time. This migration is stimulated by the heating and decreasing humidity along with the flow. In this research, winter varieties of apples (Jonathan, Golden Delicious, and Idared) were studied by heating of a 20 × 20 × 20 piece of apple with a thermocouple in it. On the basis of the measurements it can be stated that for the fruits with a high percentage of moisture (75-90%), when making the drying condition, the moisture gradient is influenced by the fractured cells of the cut area. It was found that the variety of apple is very important in relation to the heating and water loss gradient. According to the results, the wet volume change due to the heating highly influences the water loss. The models that describe the temperature of the material have a connection with the water loss. 相似文献
87.
高文义 《有色金属材料与工程》2006,27(2):27-31
碳化硅砖和碳化硅砖与普通碳砖复合侧块,在上世纪末期我国铝电解槽上开始推广应用。使用后各厂家普遍发现碳化硅砖及碳化硅砖与普通碳块复合侧块均出现不同程度的断裂、上抬和脱落现象,该文对断裂、上抬和脱落原因进行了分析,并提出了改进措施。 相似文献
88.
The present study deals with effect of the type and chemical character of incorporated polyester/polyether blocks on the hydrolytic stability of crosslinked polyurethane oligomers. Diffusion parameters of the investigated polyurethane oligomers, giving information concerning chemical changes taking place in neutral, basic and acidic aqueous environments, have also been determined. 相似文献
89.
Mössbauer studies of Fe2+ in water-soaked nafion polymer membranes in the temperature range between 90 K and 250 K have been performed. Above a critical temperature (~ 180 K) the spectra exhibit both elastic narrow absorption lines and quasielastic broad lines. These spectra are typical of bounded diffusion phenomena observed by Mössbauer spectroscopy in macromolecular systems like haemoglobin, myoglobin and ferritin. Similar spectral shapes have been observed by quasielastic neutron scattering from water in nafion membranes. Within 50 K above the critical temperature the total Mössbauer absorption area decreases by an order of magnitude whereas the narrow absorption line decreases by two orders of magnitude. The results are interpreted in terms of bounded diffusive motion of the iron. Using a model based on overdamped harmonically bound Brownian motion, the essential parameters of the iron motion can be derived as a function of temperature. The iron motion most probably reflects the motion of a large Fe2+ complex, e.g. Fe(H2O)2+6, which is attached to the polymer side chains via the sulphonic group. 相似文献
90.