全文获取类型
收费全文 | 21071篇 |
免费 | 2549篇 |
国内免费 | 1355篇 |
专业分类
电工技术 | 1573篇 |
技术理论 | 2篇 |
综合类 | 2565篇 |
化学工业 | 2224篇 |
金属工艺 | 299篇 |
机械仪表 | 769篇 |
建筑科学 | 2296篇 |
矿业工程 | 1133篇 |
能源动力 | 698篇 |
轻工业 | 3049篇 |
水利工程 | 1554篇 |
石油天然气 | 1236篇 |
武器工业 | 201篇 |
无线电 | 1736篇 |
一般工业技术 | 1643篇 |
冶金工业 | 695篇 |
原子能技术 | 69篇 |
自动化技术 | 3233篇 |
出版年
2024年 | 92篇 |
2023年 | 306篇 |
2022年 | 628篇 |
2021年 | 734篇 |
2020年 | 787篇 |
2019年 | 702篇 |
2018年 | 669篇 |
2017年 | 792篇 |
2016年 | 924篇 |
2015年 | 929篇 |
2014年 | 1373篇 |
2013年 | 1467篇 |
2012年 | 1643篇 |
2011年 | 1785篇 |
2010年 | 1304篇 |
2009年 | 1205篇 |
2008年 | 1164篇 |
2007年 | 1399篇 |
2006年 | 1225篇 |
2005年 | 1044篇 |
2004年 | 831篇 |
2003年 | 705篇 |
2002年 | 544篇 |
2001年 | 445篇 |
2000年 | 372篇 |
1999年 | 357篇 |
1998年 | 285篇 |
1997年 | 231篇 |
1996年 | 195篇 |
1995年 | 172篇 |
1994年 | 152篇 |
1993年 | 112篇 |
1992年 | 65篇 |
1991年 | 78篇 |
1990年 | 54篇 |
1989年 | 40篇 |
1988年 | 41篇 |
1987年 | 16篇 |
1986年 | 24篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1973年 | 3篇 |
1961年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Gradient-corrected density functional theory was used to investigate the adsorption of H2S on Pd(1 1 1) surface. Molecular adsorption was found to be stable with H2S binding preferentially at top sites. In addition, the adsorption of other S moieties (SH and S) was investigated. SH and S were found to be preferentially bind at the bridge and fcc sites, respectively. The reaction pathways and energy profiles for H2S decomposition giving rise to adsorbed S and H were determined. Both H2S(ad) → SH(ad) + H(ad) and SH(ad) → S(ad) + H(ad) reactions were found to have low barriers and high exothermicities. This reveals that the decomposition of H2S on Pd(1 1 1) surface is a facile process. 相似文献
82.
本文介绍在铀矿床工业指标制定中,对未来矿山开采设计方案及经济计算参数几千问题的分析,以利于合理的制定铀矿床工业指标,为铀矿冶企业技术改造,在建企业修改设计和为选择新建企业提供决策依据,进而使铀矿冶企业提高经济效益。 相似文献
83.
84.
85.
86.
ABSTRACT: Crack development during freezing (CDF) is one of the major challenges in individually quick frozen (IQF) cut and peel carrot processing. The effects of processing and freezer storage on crack development were examined on the cut and peel carrot variety, Sugarsnax. Carrot samples were removed from the major processing steps, the trans-slicer, the shaper, the blancher, and the dryer, and examined for crack development by measuring percentage cracked, crack morphology, total soluble solids, moisture levels, and membrane injury index immediately after processing. These parameters were also examined following 20 wk of standard freezer storage for cut and peels. Approximately 2% of nonprocessed carrots were cracked compared to 45% of carrots after the initial trans-slicing stage. As the processing continued, cracking decreased due to the removal of the outer epidermis to 16% of the finished product. This suggests that CDF was initiated at the 1st processing stage. Crack width and depth were 2.3 and 2.6 mm, respectively, at the trans-slicer stage and decreased to 1.1 and 1.8 mm at the end of the line. It was found that CDF was further exacerbated by freezer storage due to inefficient water removal at the dryer stage. Crack width and depth increased to 1.5 and 3.0 mm after 20 wk for freezer storage. Root size also played a role in CDF, suggesting that larger pieces are more susceptible to crack development. Total soluble solid concentrations did not play a role in crack formation during cut and peel processing. 相似文献
87.
This article is concerned with the l2-approximation of a given transfer function f by a rational one whose order is prescribed. We show that the sum of the indices of the critical points of the criterion is generically equal to 1, and in particular does not depend on f. 相似文献
88.
Liping Wang Ramana V. Grandhi Dale A. Hopkins 《International journal for numerical methods in engineering》1995,38(10):1721-1738
The objective of this paper is to conduct reliability-based structural optimization in a multidisciplinary environment. An efficient reliability analysis is developed by expanding the limit functions in terms of intermediate design variables. The design constraints are approximated using multivariate splines in searching for the optimum. The reduction in computational cost realized in safety index calculation and optimization are demonstrated through several structural problems. This paper presents safety index computation, analytical sensitivity analysis of reliability constraints and optimization using truss, frame and plate examples. 相似文献
89.
介绍了基于自由载流子对介质折射率调制作用,而建立的监测半导体器件内自由载流子变化情况的实验装置,该装置能实时反映自由载流子变化情况,且对原电路无任何影响。本方法适用于硅和砷化镓材料的电子和光电子器件,也显示了在测量集成电路内部有源器件特性方面的潜在应用前景。 相似文献
90.
工作流是实现企业业务过程建模、优化、管理、集成和自动化的核心技术.作为分布式的应用平台,工作流管理系统任务处理能力即吞吐能力是一个重要的性能指标.目前,已有的工作流管理系统在这方面存在较大的不足,成为工作流管理系统广泛应用的严重障碍.本文研究了工作流系统的协作方式和负载平衡技术,定义了工作流系统的负载因子,给出了一个分布式协作工作流系统模型,并结合业务流程逻辑,提出了分布式协作工作流系统负载平衡调度算法.实验表明该分布式协作工作流系统有效地扩展了单个工作流系统的吞吐能力。 相似文献