全文获取类型
收费全文 | 25572篇 |
免费 | 2650篇 |
国内免费 | 1588篇 |
专业分类
电工技术 | 2974篇 |
综合类 | 2852篇 |
化学工业 | 2277篇 |
金属工艺 | 977篇 |
机械仪表 | 2212篇 |
建筑科学 | 1895篇 |
矿业工程 | 648篇 |
能源动力 | 899篇 |
轻工业 | 1132篇 |
水利工程 | 496篇 |
石油天然气 | 1562篇 |
武器工业 | 385篇 |
无线电 | 2681篇 |
一般工业技术 | 2175篇 |
冶金工业 | 786篇 |
原子能技术 | 357篇 |
自动化技术 | 5502篇 |
出版年
2024年 | 103篇 |
2023年 | 280篇 |
2022年 | 592篇 |
2021年 | 740篇 |
2020年 | 747篇 |
2019年 | 584篇 |
2018年 | 584篇 |
2017年 | 743篇 |
2016年 | 849篇 |
2015年 | 978篇 |
2014年 | 1526篇 |
2013年 | 1589篇 |
2012年 | 1822篇 |
2011年 | 1933篇 |
2010年 | 1462篇 |
2009年 | 1523篇 |
2008年 | 1419篇 |
2007年 | 1707篇 |
2006年 | 1555篇 |
2005年 | 1363篇 |
2004年 | 1140篇 |
2003年 | 1039篇 |
2002年 | 932篇 |
2001年 | 732篇 |
2000年 | 687篇 |
1999年 | 544篇 |
1998年 | 451篇 |
1997年 | 415篇 |
1996年 | 308篇 |
1995年 | 268篇 |
1994年 | 244篇 |
1993年 | 183篇 |
1992年 | 167篇 |
1991年 | 109篇 |
1990年 | 100篇 |
1989年 | 81篇 |
1988年 | 56篇 |
1987年 | 25篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1979年 | 6篇 |
1965年 | 9篇 |
1959年 | 8篇 |
1958年 | 10篇 |
1956年 | 10篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
61.
1MotivationsIncreasingdensityofVLSIchipsmakesthecostoftestingveryexpensive.Designfortestabilitycantemperthisproblemdrastically.Therearetwokindsofsolutions:(i)localsolutionl3'2]withlowcomputingcomplexity,whichcannotalwaysgetsatisfactoryresults;(ii)globa.lsolutionwithprohibitivecomputingcomplekityl1'5].T.H.Chen'andM.A.Breuer[1lpresentedanILPmodeltoplacetestpointsglobally.Becauseofitscomputingcomplealty,[1lcanonlydealwithsmallormediumscalecircuits.SCOAPisusedin[1],whichisnotaveryaccuratet… 相似文献
62.
本文介绍一套先进的构件实验设备的功能及其在发动机构件疲劳试验方面的具体应用实例.通过对几种受力较复杂构件的受力分析设计出实验方法,使构件在实验室中受力情况与构件实际受力情况相似或相同,这样,得出的试验数据就可为构件的可靠性分析工作提供较好的依据. 相似文献
63.
64.
介绍燕山石化公司为扩大1Mt/a中压加氢改质装置的原料来源,改用大庆减二线油和重油催化裂化柴油组成的混合料开工投产的经验以及装置初期的运行条件。中压加氢改质技术可以生产优质柴油和蒸汽裂解制乙烯的原料,还可增产喷气燃料。 相似文献
65.
彩色PDP用玻璃基板 总被引:4,自引:0,他引:4
本文讨论了彩色PDP现用钠钙玻璃的热稳定性,指出由于这种玻璃在热处理过程中易变形和收缩,因而不适合作大面积彩色PDP基板材料,介绍了彩色PDP基板玻璃的制造方法和特点。最后介绍了日本旭硝子公司和美国康宁公司各自为彩色PDP新开发的玻璃基板材料PD200和CS25。 相似文献
66.
从徐淮地区井筒破裂的特点出发,分析引起井壁破裂的根本原因,据此提出井筒的破裂机理,为选择防治井筒破裂的方法提供依据 相似文献
67.
68.
A novel successive learning algorithm based on a Test Feature Classifier is proposed for efficient handling of sequentially provided training data. The fundamental characteristics of the successive learning are considered. In the learning, after recognition of a set of unknown data by a classifier, they are fed into the classifier in order to obtain a modified performance. An efficient algorithm is proposed for the incremental definition of prime tests which are irreducible combinations of features and capable of classifying training patterns into correct classes. Four strategies for addition of training patterns are investigated with respect to their precision and performance using real pattern data. A real-world problem of classification of defects on wafer images has been dealt with by the proposed classifier, obtaining excellent performance even through efficient addition strategies. 相似文献
69.
Quantitative analyses of flow and stage data, remote sensing and geographic information systems analysis, and field studies were used to assess the impact of dams and diversions on the point bar habitat of the Sacramento Valley Tiger Beetle (Cicindela hirticollis abrupta). The reaches of interest include sites of known historic populations of C. h. abrupta along the Sacramento River from approximately 8 km north of Colusa southward to the confluence with the Feather River and along the Feather River between Yuba City and its confluence with the Sacramento River. The results from this study show that construction of two major dams has altered flows such that prolonged and increased flows during summer, fall, and early winter have most likely disrupted life cycles, flooded larvae, drowned overwintering adults and led to high mortality. Additionally, habitat availability has decreased over time because point bars have decreased in number and area causing increased distances between populations and isolation of populations. Moreover, point bar armouring, channel scouring, altered flows, redirected flows through weirs, and lithologic controls have produced a bimodal distribution of mean grain sizes in the Sacramento River in which the more northern bars contain gravel deposits and more southern bars possess fine sands. These conditions negatively alter moisture retention and sediment compaction and, consequently, burrowing conditions needed by this tiger beetle. Additionally, more stabilized flows (reduced variability) and increased fine‐grained deposition have enabled development and encroachment of vegetation onto the sand bars. Finally, human stresses, such as foot traffic and vehicular traffic may have interfered with burrowing, ovipositing, and foraging. The combination of these stress factors has most likely led to a reduction in source populations and, ultimately, the apparent extirpation of the entire metapopulation. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
70.
成形磨削中砂轮修整精度的研究 总被引:6,自引:1,他引:5
成形磨削一般采用金刚石笔来修整所需要的砂轮形状,金刚石笔在安装中的位置误差将影响被加工工件的精度,本文对此误差的大小进行了分析。 相似文献