全文获取类型
收费全文 | 20341篇 |
免费 | 2214篇 |
国内免费 | 1149篇 |
专业分类
电工技术 | 1394篇 |
综合类 | 1714篇 |
化学工业 | 3140篇 |
金属工艺 | 950篇 |
机械仪表 | 1099篇 |
建筑科学 | 1490篇 |
矿业工程 | 430篇 |
能源动力 | 433篇 |
轻工业 | 2758篇 |
水利工程 | 519篇 |
石油天然气 | 616篇 |
武器工业 | 142篇 |
无线电 | 2179篇 |
一般工业技术 | 2215篇 |
冶金工业 | 769篇 |
原子能技术 | 279篇 |
自动化技术 | 3577篇 |
出版年
2024年 | 117篇 |
2023年 | 386篇 |
2022年 | 851篇 |
2021年 | 1004篇 |
2020年 | 787篇 |
2019年 | 694篇 |
2018年 | 687篇 |
2017年 | 831篇 |
2016年 | 716篇 |
2015年 | 1076篇 |
2014年 | 1266篇 |
2013年 | 1530篇 |
2012年 | 1688篇 |
2011年 | 1735篇 |
2010年 | 1517篇 |
2009年 | 1414篇 |
2008年 | 1390篇 |
2007年 | 1213篇 |
2006年 | 1104篇 |
2005年 | 880篇 |
2004年 | 570篇 |
2003年 | 399篇 |
2002年 | 318篇 |
2001年 | 287篇 |
2000年 | 238篇 |
1999年 | 182篇 |
1998年 | 123篇 |
1997年 | 90篇 |
1996年 | 81篇 |
1995年 | 65篇 |
1994年 | 47篇 |
1993年 | 44篇 |
1992年 | 48篇 |
1991年 | 20篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 18篇 |
1986年 | 22篇 |
1985年 | 14篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 22篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1974年 | 9篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
In a complex social, political, economic, technological, and/or environmental context, corporate, military, government, and other organizations are often faced with collective decision-making situations. The rationale for group decision exercises is that the judgment of many will usually prove superior to the judgment of one. However, it has been shown that collective decision exercises are often highly dependent on matters of perspective, values and opinion, all of which - being essentially subjective in nature - are beyond the reach of existing formal decision technology. Furthermore, it can be expected that many collective decision exercises - particularly those of strategic import - will not lend themselves to the quantitative analysis instruments that have long dominated the management and decision science repertoire. This does not, however, mean that they must remain entirely and forever outside the bounds of scientific rationality. The ordering protocols which are currently available do not have enough technical mechanics to be relied upon to bring us to any satisfying resolution of a priori disputation. Hence, we propose an a priori ordering reference model that might support consensus-building in a multiple stakeholders context. In order to detect whether the subjective arguments are products of proper reasons or merely instances of raw rhetoric and to suggest how any logical or syntactical flaws might best be repaired, we propose logical ordering facilities and protocols for integrating procedural and instrumental provisions for a group-decision process with two lines of technical innovation: the superimpositional ordering function and the logical ordering support facilities. 相似文献
72.
介绍了高温超导红外探测器电极材料的选择和制备。选用先蒸、后蒸金,再合金化的电极工艺。芯片装配成器件后,器件性能稳定,膜层牢固,接触电阻小。 相似文献
73.
本文介绍了ConcurrentC语言在一分布式系统上的实现。该实现使用了不同于预编译法的编译器的构造方法,同时将Concurrent C语言中的进程实现为UNIX进程中的用户级线索,是ConcurrentC语言在分布式系统上的一种高效实现。 相似文献
74.
In this paper,we address the need for better hands-on learning materials in computing education and the need for integrating mobile computing education into computing curricular.We propose an innovative learning approach that uses state-of-the-art mobile computing technologies and devices to design a highly accessible and real-world relevant hands-on labware for computing education.The labware employs a modular design such that the learning materials can both be combined together into a single course of mobile program development and be integrated into the related computing courses as building blocks.The labware will help students understand the concepts,improve their problem solving skills,and prepare them for the mobile computing industrial workforce.The pilot modules of the labware have been presented to undergraduate students and have received positive feedbacks. 相似文献
75.
吴丹 《计算机与数字工程》2012,40(7):56-59
文章介绍了波形数字化仪的原理、结构、工作方式及特点,并针对其校准技术进行了深入的研究。通过多功能校准源、示波器及测试系统数字模块实现波形数字化仪模块的精确校准,解决了波形数字化仪模块的校准问题。校准结果表明,该校准装置及校准方法能够满足集成电路测试系统任意波形发生器的校准要求。 相似文献
76.
77.
针对MIMO链路ad hoc网络中已有传输调度算法未充分利用MIMO空间复用能力的问题,提出了一种新的传输调度算法.该算法通过考虑MIMO的多流接收能力而有效地减小了调度帧长,通过合理安排节点分配顺序使得节点分配的数据流比较平均,同时,该算法通过允许节点发送多个数据流而高效利用了MIMO的空间复用能力.推导分析了传输调度算法的通过量和时延性能,结果表明,与已有算法相比,采用文中算法可以提高网络的通过量,减小网络的平均时延和最大时延. 相似文献
78.
79.
针对初学者在学习Access数据库中遇到的困难,设计了三个教学案例,介绍报表中计算控件的使用、if语句的语法格式和通配符“?”和“’,的使用.对于提高Access数据库的教学效果有一定的参考价值。 相似文献
80.
Lyndsay A. Cartwright Sue Hayes Douglas C. Tozer Dan Clayton Mary-Ann Burns Dena Lewis Noah Gaetz Namrata Shrestha 《Journal of Great Lakes research》2021,47(2):273-282
Beneficial use impairments (BUIs) under the Great Lakes Water Quality Agreement identify environmental issues requiring remedial action within the Great Lakes Areas of Concern (AOCs). We conducted this study to support the assessment of the wildlife component of BUI 3: degradation of fish and wildlife populations. We compared bird and amphibian (frogs and toads) data from the Toronto and Region Conservation Authority’s Terrestrial Long-term Monitoring Program in the Toronto and Region AOC to an adjacent, but otherwise similar, reference watershed, Duffins Creek. Twelve of 13 targets were met within the AOC for forest bird, wetland bird, meadow bird and amphibian populations based on averages of mean annual values at sites within the AOC that were within two standard deviations of averages at sites in the Duffins Creek reference watershed between 2008 and 2017. Even though wildlife populations within the AOC were within the normal range of variability expected from a reference watershed, they were often at lower levels than within the Duffins Creek reference watershed. In addition, forest bird and amphibian populations were negatively affected by urbanization within the AOC and meadow bird indices declined. We conclude that while wildlife populations within the AOC currently meet targets for BUI 3, they continue to be negatively impacted by numerous stressors that are primarily related to past and ongoing urbanization. Thus, continued restoration of wildlife habitat and protection of existing habitat within the AOC is highly recommended. 相似文献