全文获取类型
收费全文 | 33912篇 |
免费 | 3863篇 |
国内免费 | 2799篇 |
专业分类
电工技术 | 2280篇 |
技术理论 | 1篇 |
综合类 | 3311篇 |
化学工业 | 5303篇 |
金属工艺 | 1452篇 |
机械仪表 | 1796篇 |
建筑科学 | 1920篇 |
矿业工程 | 911篇 |
能源动力 | 1166篇 |
轻工业 | 1721篇 |
水利工程 | 726篇 |
石油天然气 | 1959篇 |
武器工业 | 551篇 |
无线电 | 6584篇 |
一般工业技术 | 4713篇 |
冶金工业 | 1018篇 |
原子能技术 | 1218篇 |
自动化技术 | 3944篇 |
出版年
2024年 | 145篇 |
2023年 | 646篇 |
2022年 | 881篇 |
2021年 | 1045篇 |
2020年 | 1188篇 |
2019年 | 1030篇 |
2018年 | 1011篇 |
2017年 | 1265篇 |
2016年 | 1477篇 |
2015年 | 1428篇 |
2014年 | 2001篇 |
2013年 | 2245篇 |
2012年 | 2453篇 |
2011年 | 2788篇 |
2010年 | 2046篇 |
2009年 | 1987篇 |
2008年 | 1904篇 |
2007年 | 2251篇 |
2006年 | 1952篇 |
2005年 | 1716篇 |
2004年 | 1393篇 |
2003年 | 1210篇 |
2002年 | 919篇 |
2001年 | 862篇 |
2000年 | 719篇 |
1999年 | 629篇 |
1998年 | 525篇 |
1997年 | 459篇 |
1996年 | 416篇 |
1995年 | 348篇 |
1994年 | 311篇 |
1993年 | 264篇 |
1992年 | 201篇 |
1991年 | 166篇 |
1990年 | 151篇 |
1989年 | 126篇 |
1988年 | 95篇 |
1987年 | 63篇 |
1986年 | 54篇 |
1985年 | 53篇 |
1984年 | 41篇 |
1983年 | 28篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1959年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
M. Polák M. Majoro F. Hanic J. Pitel M. Kedrová P. Kottman J. Talapa L. Vencel 《Journal of Superconductivity》1989,2(2):219-233
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ
cs
and the intergranular transport current densityJ
cr
are identical if the measurement conditions are similar. A degradation ofJ
cs
measured in the external field with AC ripple has been observed. 相似文献
72.
73.
74.
75.
色用缓变光纤中交叉相位调制不稳定性分析 总被引:7,自引:2,他引:5
从非线性薛定谔方程出发得到了色散缓变光纤(DDF)中交叉相位调制(XPM)不稳定增益谱。研究了增益谱随入纤功率及光纤纵向色散参量的变化关系。结果表明:反常色散区的增益谱宽比正常色散区宽,且峰值增益高:DDF中XPM不稳定增益谱宽比常规光纤的宽,二者的比值随传输距离和光纤色散参量的乘积成指数增长;DDF的反常色散区是产生调制不稳定的较好的色散介质。 相似文献
76.
CDMA通信系统的MATLAB仿真 总被引:7,自引:0,他引:7
在简要介绍MATLAB语言的基础上,对使用MATLAB语方仿真的CDMA通信系统进行描述。 相似文献
77.
Using the focal mechanisms of earthquakes taken place from 1950 to 1996, the type and direction of principal strains were established, which made it possible to determine the volume stress-strain state of the south-east flank of the Baikal rift zone on the basis of the inverse problem solution. The variations in the stress-strain fields and spatial distribution of the stored potential energy density were found by the displacements of the daylight surface points in Tunkinsk geodetic proving ground in 1975 - 1986. 相似文献
78.
应用统计控制图法,选用平均值——标准差、平均值——极差控制图法,控制24^#坝粘土填筑干密度值及施工偶然异常波动,早期提出警报,以保证土坝的施工质量。 相似文献
79.
Novel polyurethane insulating coatings were prepared from the reaction of glycerin‐terminated polyurethane prepolymers (GPUPs) and a blocked isocyanate curing agent (BIC). The GPUPs were prepared from the reaction of one equivalent of polycaprolactone polyol (CAPA 210) with an excess amount of 4,4′‐methylene bis(phenyl isocyanate) (MDI) and subsequent reaction of the NCO‐terminated polyurethane with glycerin. The BIC was prepared from the reaction of trimethylol propane (TMP), toluene diisocyanate (TDI) and N‐methylaniline (NMA). The polyols and curing agent were characterized by conventional methods while the curing condition was optimized via gel content measurements. The curing kinetics of the polyurethane coating were investigated and the kinetic parameters derived. The crosslink densities of the samples were determined via the equilibrium swelling method, using the Flory–Rehner equation. The relationships between the crosslink density and the electrical, physical, mechanical and dynamic mechanical properties of the coatings were also studied. Copyright © 2005 Society of Chemical Industry 相似文献
80.
RRN Sailaja 《Polymer International》2005,54(12):1589-1598
Lignin was graft copolymerized with methyl methacrylate using manganic pyrophosphate as initiator. This modified lignin was then blended (up to 50 wt%) with low density polyethylene (LDPE) using a small quantity of poly[ethylene‐co‐(glycidyl methacrylate)] (PEGMA) compatibilizer. The mechanical properties of the blend were substantially improved by using modified lignin in contrast to untreated lignin. Differential scanning calorimetry studies showed loss of crystallinity of the LDPE phase owing to the interaction between the blend components. Thermogravimetric analysis showed higher thermal stability of modified lignin in the domain of blend processing. This suggested that there is scope for useful utilization of lignin, which could also lead to the development of eco‐friendly products. Copyright © 2005 Society of Chemical Industry 相似文献