全文获取类型
收费全文 | 34306篇 |
免费 | 3532篇 |
国内免费 | 1836篇 |
专业分类
电工技术 | 1705篇 |
技术理论 | 1篇 |
综合类 | 2172篇 |
化学工业 | 5975篇 |
金属工艺 | 1748篇 |
机械仪表 | 2072篇 |
建筑科学 | 2251篇 |
矿业工程 | 735篇 |
能源动力 | 1093篇 |
轻工业 | 3234篇 |
水利工程 | 733篇 |
石油天然气 | 1168篇 |
武器工业 | 271篇 |
无线电 | 4729篇 |
一般工业技术 | 4744篇 |
冶金工业 | 1469篇 |
原子能技术 | 476篇 |
自动化技术 | 5098篇 |
出版年
2024年 | 148篇 |
2023年 | 498篇 |
2022年 | 971篇 |
2021年 | 1336篇 |
2020年 | 1085篇 |
2019年 | 964篇 |
2018年 | 1108篇 |
2017年 | 1182篇 |
2016年 | 1252篇 |
2015年 | 1397篇 |
2014年 | 1781篇 |
2013年 | 2342篇 |
2012年 | 2493篇 |
2011年 | 2620篇 |
2010年 | 2395篇 |
2009年 | 2306篇 |
2008年 | 2209篇 |
2007年 | 2085篇 |
2006年 | 1848篇 |
2005年 | 1503篇 |
2004年 | 1202篇 |
2003年 | 1171篇 |
2002年 | 1254篇 |
2001年 | 1124篇 |
2000年 | 688篇 |
1999年 | 530篇 |
1998年 | 456篇 |
1997年 | 355篇 |
1996年 | 294篇 |
1995年 | 221篇 |
1994年 | 144篇 |
1993年 | 124篇 |
1992年 | 105篇 |
1991年 | 85篇 |
1990年 | 71篇 |
1989年 | 68篇 |
1988年 | 36篇 |
1987年 | 34篇 |
1986年 | 20篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1959年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
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
92.
Jong Jip Kim 《Journal of Materials Science Letters》1996,15(19):1687-1689
93.
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
94.
Testing of the multi-application small light water reactor (MASLWR) passive safety systems 总被引:1,自引:0,他引:1
Jose N. Reyes John Groome Brian G. Woods Eric Young Kent Abel You Yao Yeon Jong Yoo 《Nuclear Engineering and Design》2007,237(18):1999-2005
Experimental thermal hydraulic research has been conducted at Oregon State University for the purpose of assessing the performance of a new reactor design concept, the multi-application small light water reactor (MASLWR). The MASLWR is a pressurized light water reactor design with a net output of 35 MWe that uses natural circulation in both normal and transient operation. Due to its small size, portability and modularity, the MASLWR design is well suited to help fill the potential need for grid appropriate reactor designs for smaller electricity grids as may be found in developing or remote regions. The purpose of the OSU MASLWR test facility is to assess the operation of the MASLWR under normal full operating pressure and full temperature conditions and to assess the passive safety systems under transient conditions. The data generated by the testing program will be used to assess computer code calculations and to provide a better understanding of the thermal-hydraulic phenomena in the design of the MASLWR NSSS. During this testing program, four tests were conducted at the OSU MASLWR test facility. These tests included one design basis accident and one beyond design basis accident. During the performance of these tests, plant operations to include start up, normal operation and shut down evolutions were demonstrated successfully. 相似文献
95.
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
96.
张蕴生 《消防技术与产品信息》2005,(2):45-46
从高层医院所应具备自动消防系统和在高层医院日常管理中 ,加强消防安全教育 ,建立管理制度 ,主动发挥“人”主观能动性的两个方面 ,具体阐述了高层医院的消防安全工作 相似文献
97.
目的改良大鼠可逆性大脑中动脉缺血模型的栓子制作方法,增加模型稳定性和成功率,提高脑缺血实验研究结果的可靠性.方法体重280~320g Wistar雄性大鼠60只,随机分成改良组和对照组,每组30只.对照组用尼龙线一端加热法制作传统栓子,改良组用尼龙线一端沾silicone胶法制作改良栓子.两组模型除栓子制作方法不同外,其他手术步骤完全相同.采用Zea Longa 5分制法进行模型的神经功能评分,采用TTC染色法测量并计算梗死灶的大小.比较两组模型制作成功率、成功模型中神经功能评分3、4级大鼠所占百分数,以 相似文献
98.
99.
100.
We explore in this paper the efficient clustering of market-basket data. Different from those of the traditional data, the features of market-basket data are known to be of high dimensionality and sparsity. Without explicitly considering the presence of the taxonomy, most prior efforts on clustering market-basket data can be viewed as dealing with items in the leaf level of the taxonomy tree. Clustering transactions across different levels of the taxonomy is of great importance for marketing strategies as well as for the result representation of the clustering techniques for market-basket data. In view of the features of market-basket data, we devise in this paper a novel measurement, called the category-based adherence, and utilize this measurement to perform the clustering. With this category-based adherence measurement, we develop an efficient clustering algorithm, called algorithm k-todes, for market-basket data with the objective to minimize the category-based adherence. The distance of an item to a given cluster is defined as the number of links between this item and its nearest tode. The category-based adherence of a transaction to a cluster is then defined as the average distance of the items in this transaction to that cluster. A validation model based on information gain is also devised to assess the quality of clustering for market-basket data. As validated by both real and synthetic datasets, it is shown by our experimental results, with the taxonomy information, algorithm k-todes devised in this paper significantly outperforms the prior works in both the execution efficiency and the clustering quality as measured by information gain, indicating the usefulness of category-based adherence in market-basket data clustering. 相似文献