全文获取类型
收费全文 | 29904篇 |
免费 | 3432篇 |
国内免费 | 2442篇 |
专业分类
电工技术 | 3074篇 |
综合类 | 4060篇 |
化学工业 | 2599篇 |
金属工艺 | 1574篇 |
机械仪表 | 2195篇 |
建筑科学 | 2246篇 |
矿业工程 | 728篇 |
能源动力 | 1307篇 |
轻工业 | 935篇 |
水利工程 | 998篇 |
石油天然气 | 1886篇 |
武器工业 | 374篇 |
无线电 | 2600篇 |
一般工业技术 | 4221篇 |
冶金工业 | 883篇 |
原子能技术 | 316篇 |
自动化技术 | 5782篇 |
出版年
2024年 | 152篇 |
2023年 | 455篇 |
2022年 | 744篇 |
2021年 | 940篇 |
2020年 | 1043篇 |
2019年 | 884篇 |
2018年 | 814篇 |
2017年 | 984篇 |
2016年 | 1062篇 |
2015年 | 1134篇 |
2014年 | 1711篇 |
2013年 | 1936篇 |
2012年 | 2152篇 |
2011年 | 2214篇 |
2010年 | 1653篇 |
2009年 | 1761篇 |
2008年 | 1670篇 |
2007年 | 1897篇 |
2006年 | 1748篇 |
2005年 | 1499篇 |
2004年 | 1269篇 |
2003年 | 1146篇 |
2002年 | 985篇 |
2001年 | 841篇 |
2000年 | 817篇 |
1999年 | 657篇 |
1998年 | 554篇 |
1997年 | 525篇 |
1996年 | 456篇 |
1995年 | 386篇 |
1994年 | 328篇 |
1993年 | 264篇 |
1992年 | 253篇 |
1991年 | 185篇 |
1990年 | 161篇 |
1989年 | 157篇 |
1988年 | 103篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 27篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1959年 | 3篇 |
1956年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
论校园文化和德育目标的一致性 总被引:3,自引:0,他引:3
冯峰 《河南机电高等专科学校学报》2002,10(1):13-14
中系统介绍了校园化和德育目标的关系,并找准两之间的结合点,通过分析两的一致性和辩证统一关系,达到育人目的。 相似文献
62.
The main problems in estimating the uncertainty due to the presence of impurities in the material: the absence in the documents of a unique definition of the quantity being measured – the fixed point temperature, the lack of agreed methods of realizing the fixed points and the insufficient justification of the equations used for the estimate, are analyzed. The results of a measurement of the melting point of gallium are presented, which differ in the conditions in which they were realized – with one and two liquid-solid interfaces and different solidification conditions, are presented. The reasons for the considerable difference between the values of the temperatures obtained in these experiments are discussed. 相似文献
63.
64.
65.
Hamid Javaherian Naghash Ahmad Reza Momeni Hamid Alian Ahmad Reza Massah Shahla Ataie 《Polymer International》2005,54(11):1564-1571
Poly(methyl methacrylate) (PMMA) gels with varying amounts of silicone and solvent and constant amounts of crosslinker were prepared by solution free radical crosslinking copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) comonomer systems. They were then studied in benzene at a total monomer concentration of 3.5 mol L?1 and 70 °C. The conversion of monomer, volume swelling ratio, weight fraction and gel point were measured as a function of the reaction time, silicone concentration and benzene content up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in benzene, gel fraction and Fourier‐transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by SEM. Based on the obtained results, it was concluded that the FTIR data did not have the capacity to show the presence of the VTES or TEOS moiety in these kinds of copolymers. On the other hand, the variation of weight fraction of gel, Wg, and its equilibrium volume swelling ratio in benzene, qv, exhibited the same behaviour as that of MMA/EGDM copolymers. Also, the dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percent of conversion and gel fraction. Finally, TEOS is not an ideal silicone compound for reaction in the MMA/EGDM copolymerization system, whereas VTES is a suitable silicone comonomer for this system and it has been proved useful. Copyright © 2005 Society of Chemical Industry 相似文献
66.
This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated. 相似文献
67.
Alfalfa juice was extracted from plants during the graving phases of the first and second crops. The alfalfa juice was dried and solute concentrations were measured periodically during the process using freezing point depression (FPD) as an indicator. Solute/solvent weight ratios were calculated from the freezing point depression of fresh unconcentrated 'uice extracted from both firsc and second crops. At the time of harvest, tie FPD was a function of this ratio. The first and second crops behaved distinctively different during the drying process, with the second having a larger soluce concentration and a greater FPD at a given moisture content. The appearance of preci itate during the drying process and the general1 large FPD makes this materiay a questionable product for drying vitg low temperature processes. 相似文献
68.
T. Bag 《Information Sciences》2006,176(19):2910-2931
In this paper, definitions of strongly fuzzy convergent sequence, l-fuzzy weakly convergent sequence and l-fuzzy weakly compact set are given in a fuzzy normed linear space. The concepts of fuzzy normal structure, fuzzy non-expansive mapping, uniformly convex fuzzy normed linear space are introduced and fixed point theorems for fuzzy non-expansive mappings are proved. 相似文献
69.
黄化字 《南方冶金学院学报》2005,26(6):55-59
给出了射影几何中关于二阶曲线渐近线的几个等价定义,并探讨了根据不同 定义的二阶曲线渐近线的应用. 相似文献
70.
The macroscopic deformation behavior of a fiber-reinforced aluminum-boron composite is investigated. Different periodic and random arrangements of the microstructure are considered with macroscopic hardening behavior due to the evolution of plastic zones on the microscale being taken into account.
For the solution of the initial boundary value problem, a non-standard algorithm is applied. It consists of the direct solution of the whole set of equations, treating all variables as global quantities. Together with a higher order time integration method (BDF2), an automatic step size control is used in the FEM calculations. 相似文献