全文获取类型
收费全文 | 3916篇 |
免费 | 468篇 |
国内免费 | 267篇 |
专业分类
电工技术 | 404篇 |
技术理论 | 1篇 |
综合类 | 679篇 |
化学工业 | 244篇 |
金属工艺 | 160篇 |
机械仪表 | 148篇 |
建筑科学 | 324篇 |
矿业工程 | 153篇 |
能源动力 | 94篇 |
轻工业 | 139篇 |
水利工程 | 110篇 |
石油天然气 | 232篇 |
武器工业 | 28篇 |
无线电 | 366篇 |
一般工业技术 | 535篇 |
冶金工业 | 171篇 |
原子能技术 | 119篇 |
自动化技术 | 744篇 |
出版年
2024年 | 8篇 |
2023年 | 45篇 |
2022年 | 94篇 |
2021年 | 89篇 |
2020年 | 129篇 |
2019年 | 118篇 |
2018年 | 129篇 |
2017年 | 147篇 |
2016年 | 116篇 |
2015年 | 133篇 |
2014年 | 254篇 |
2013年 | 274篇 |
2012年 | 299篇 |
2011年 | 296篇 |
2010年 | 250篇 |
2009年 | 245篇 |
2008年 | 245篇 |
2007年 | 246篇 |
2006年 | 234篇 |
2005年 | 193篇 |
2004年 | 148篇 |
2003年 | 154篇 |
2002年 | 117篇 |
2001年 | 104篇 |
2000年 | 91篇 |
1999年 | 71篇 |
1998年 | 49篇 |
1997年 | 35篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 38篇 |
1993年 | 35篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1987年 | 2篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1968年 | 2篇 |
1959年 | 3篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有4651条查询结果,搜索用时 15 毫秒
91.
With the recent growth in smartphone services, the “mobile” environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile‐Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile‐oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier‐locator separation, query‐first data delivery for route optimization, and distributed control of identifier‐locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier‐locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay. 相似文献
92.
In recent years, a peculiar homelessness policy that goes under the name of ‘Housing First’ has become increasingly popular all over the world. Epitomising a quintessential case of policy-mobility, Housing First can today be considered an heterogeneous assemblage of experiences and approaches that sometimes have little in common with each other. Introducing and commenting upon this heterogeneity, the paper critically analyses why and how Housing First has become a planetary success and what are the issues at stake with its widespread implementation. If recent scholarship published in this journal has granted us a fine understanding of Housing First’s functioning in the US, this paper offers something currently absent from the debate: a nuanced and critical understanding of the ambiguities related to the international success of this policy, with specific references to the challenges associated to its translation in the Italian case. 相似文献
93.
94.
采用密度泛函理论框架下的第一性原理平面波超软赝势方法,在相同环境条件下分别建立了未掺杂和取代O高掺杂N原子的金红石型TiO2超胞模型,优化了晶胞的几何结构,计算了能带分布、态密度分布和吸收光谱.结果表明,金红石型TiO2-xNx超胞取x=0.0625的条件下,N的2p态与O的2p态发生杂化耦合,使其价带上移、最小带隙变... 相似文献
95.
采用基于密度泛函理论(Density function theory,DFT)的第一性原理方法,计算研究了AlN中掺杂Mg后的电子结构和磁性。我们从理论上给出了AlN∶Mg的晶体结构参数和电子结构,计算了铁磁相和反铁磁相的总能,发现AlN∶Mg具有半金属特性,并且其铁磁相更稳定。我们通过分析比较AlN和AlN∶Mg的电子结构,解释了非磁性杂质Mg掺杂在AlN中产生磁性的原因是Mg取代Al后,会在自旋向下的价带顶部引入空穴,导致费米能级移入价带中,从而使自旋向上和自旋向下的态密度产生不对称的分布,从而导致材料中有净磁矩。另外,通过比较AlN∶Mg的多种构型的形成能,发现在纤锌矿结构AlN中掺入Mg比较容易实现,在闪锌矿结构中次之,但对于其它几何构型,由于形成能太高,Mg很难掺入到材料中。这种材料可作为制备非磁性掺杂的半导体自旋电子器件的备选材料。 相似文献
96.
考虑到直接解析法求解速度快和非线性直接解析法求解精度高的特点,提出一种用于结构损伤识别的混合迭代算法,该算法用二阶非线性的解析解作为算法的第一次迭代值,用一阶灵敏度方程的求解值对该算法的第一次迭代值进行关于泰勒级数截尾误差的修正。通过对一个空间框架结构进行数值模拟分析验证了该方法的可行性。结果表明,提出的混合迭代算法由于采用了精确度较高的二阶非线性解析解作为迭代修正的初值,因此,迭代修正精度更高,收敛性更好,而且大幅地减少了运算时间,尤其对于多损伤或者大损伤,本算法优势更加明显。 相似文献
97.
孔祥强 《Canadian Metallurgical Quarterly》2011,21(4)
研究了一类特殊矩阵特征值的绝对扰动上界问题,利用矩阵的奇异值分解和矩阵计算方面的技巧,探讨了正规矩阵特征值的扰动问题,得到了正规矩阵特征值的Wielandt型绝对扰动上界。本文得到的结论还进一步推广了Wielandt-Hoffman定理.是比Wielandt-Hoffman定理更一般的形式。 相似文献
98.
Stroud Catherine B.; Davila Joanne; Hammen Constance; Vrshek-Schallhorn Suzanne 《Canadian Metallurgical Quarterly》2011,120(1):142
Overall, research has evidenced support for Post's (1992) model, which asserts that the 1st episode of depression is more likely to be associated with severe life events than are subsequent episodes. In spite of this, there are significant gaps in the understanding of the stress–depression association. This study aimed to address three gaps by (a) identifying the explanatory model underlying the association (stress sensitization vs. stress autonomy), (b) elucidating how the role of stress changes with successive episodes, and (c) examining the role of nonsevere events. The impact and occurrence of severe and nonsevere events in a 5-year longitudinal study of late-adolescent women were examined using Cox regression models. Overall, we found support for the stress sensitization model over the stress autonomy model. Specifically, the impact of nonsevere (but not severe) events was greater in individuals with a history of depression compared with those with no history of depression. In addition, the occurrence of severe (but not nonsevere) events was greater for 1st onsets than recurrences. These effects were modified by event independence. The results were discussed in terms of the underlying mechanisms of the stress–depression association and future directions for research were elaborated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
In this article we examined aspects of negotiation within a persuasion framework. Specifically, we investigated how the provision of arguments that justified the first offer in a negotiation affected the behavior of the parties, namely, how it influenced counteroffers and settlement prices. In a series of 4 experiments and 2 pilot studies, we demonstrated that when the generation of counterarguments was easy, negotiators who did not add arguments to their first offers achieved superior results compared with negotiators who used arguments to justify their first offer. We hypothesized and provided evidence that adding arguments to a first offer was likely to cause the responding party to search for counterarguments, and this, in turn, led him or her to present counteroffers that were further away from the first offer. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
100.