全文获取类型
收费全文 | 26985篇 |
免费 | 2962篇 |
国内免费 | 1817篇 |
专业分类
电工技术 | 1646篇 |
技术理论 | 1篇 |
综合类 | 2164篇 |
化学工业 | 4133篇 |
金属工艺 | 1506篇 |
机械仪表 | 1638篇 |
建筑科学 | 2131篇 |
矿业工程 | 734篇 |
能源动力 | 804篇 |
轻工业 | 2592篇 |
水利工程 | 703篇 |
石油天然气 | 1164篇 |
武器工业 | 269篇 |
无线电 | 3462篇 |
一般工业技术 | 3129篇 |
冶金工业 | 987篇 |
原子能技术 | 384篇 |
自动化技术 | 4317篇 |
出版年
2024年 | 142篇 |
2023年 | 411篇 |
2022年 | 851篇 |
2021年 | 1146篇 |
2020年 | 915篇 |
2019年 | 742篇 |
2018年 | 872篇 |
2017年 | 940篇 |
2016年 | 903篇 |
2015年 | 1146篇 |
2014年 | 1407篇 |
2013年 | 1826篇 |
2012年 | 1993篇 |
2011年 | 1994篇 |
2010年 | 1922篇 |
2009年 | 1871篇 |
2008年 | 1785篇 |
2007年 | 1765篇 |
2006年 | 1578篇 |
2005年 | 1257篇 |
2004年 | 1011篇 |
2003年 | 979篇 |
2002年 | 1070篇 |
2001年 | 969篇 |
2000年 | 560篇 |
1999年 | 391篇 |
1998年 | 253篇 |
1997年 | 219篇 |
1996年 | 183篇 |
1995年 | 150篇 |
1994年 | 109篇 |
1993年 | 74篇 |
1992年 | 79篇 |
1991年 | 51篇 |
1990年 | 34篇 |
1989年 | 44篇 |
1988年 | 15篇 |
1987年 | 20篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1959年 | 8篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
62.
在不同反应温度条件下采用原位聚合法在石英基片上制备了聚苯胺薄膜.对薄膜样品进行了紫外光谱、SEM、电性能表征。实验结果表明,过高的合成温度会加速聚合反应过程,抑制膜厚的增长,引起薄膜的热降解,进而对样品的导电性产生不良影响。根据生长速率与合成温度的依赖关系,估算了聚合反应的活化能Ea=34.4kJ/mol。 相似文献
63.
针对有限元仿真分析中结构自振周期减小的问题,讨论了几种主要的影响因素,并借用商品化设计软件TBSA,ETABS 和有限元分析软件ANSYS,通过对一个简单结构的多次计算,比较了这些因素的影响大小。 相似文献
64.
The rate of filtration and the water content of cake are influenced by the existence of a dense skin in a highly compressible
cake. The phenomenon of the dense skin has been rarely studied, and its existence has not been verified experimentally. In
this study, the porosity variation in a very compressible cake is measured by using a new experimental apparatus, and with
this the existence of dense skin has been established experimentally. ‘Unified theory on solid-liquid separation’, a recently
developed theory, is utilized for calculating the porosity variation in a very compressible cake. 相似文献
65.
应用SolidWorks软件,建立了螺杆压缩机机体三维实体模型.对螺杆压缩机机体的内、外螺旋面的建模进行了分析和研究,提出了建立分段螺旋面模型的基本思路和方法. 相似文献
66.
An adaptive optical sequence generation scheme has been described in a nonlinear optical ring which exhibits chaotic dynamics. The adaptation is based on avoidance of collisions between the ring output and signals from another source. It is shown that collision-avoiding sequences can be autonomously selected via chaotic mode transitions induced by the feedback of collision signals. Experimental results demonstrate that the method can be successful for various collision signal patterns with different periods and pulsewidths. The mechanism of inducing chaos with collision signals is examined both experimentally and with numerical simulations and the results verify the effectiveness of the proposed adaptation method. A possible application of the proposed signal generation scheme in intelligent optical communication networks is mentioned 相似文献
67.
68.
CaO-Al2O3-MgO (CAM) ceramic fibre produced via inviscid melt spinning (IMS) was investigated for phase transformation. Differential thermal analysis (DTA) on the as-spun CAM fibre gave two transformation peaks, one for exothermic peak at around 927°C and the other for endothermic one at around 1100°C. In order to identify each phase transformation x-ray diffraction (XRD) analysis was performed on the CAM fibres heat-treated to each phase transformation completion temperature. The exothermic peak was determined to represent crystallization of remaining amorphous phase in the as-spun CAM fibre. The endothermic peak was determined to correspond to transformation of non-equilibrium CaO · Al2O3 phase to equilibrium 3CaO· 5Al2O3 phase. 相似文献
69.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
70.
This study employs a relational dialectics approach to gain insights into the nature of relational communication via Cyworld , a Korean social network site. Qualitative analysis of in-depth interview data from 49 users suggests that Cyworld users routinely negotiate multiple dialectical tensions that are created within the online world, transferred from face-to-face contexts, or imposed by interpersonal principles that relate to Korea's collectivistic culture. The interviewees experienced a new relational dialectic of interpersonal relations versus self-relation, analogous to Baxter and Montgomery's (1996) connection-autonomy contradiction. Their responses suggest that Cyworld's design features and functions encourage users to transcend the high-context communication of Korean culture by offering an alternative channel for elaborate and emotional communication, which fosters the reframing of relational issues offline. Cy-Ilchons (online buddies) virtually extend the Korean cultural concept of blood ties, called yons, in ways that intensify the openness-closedness contradiction at early stages of relationship formation. 相似文献