全文获取类型
收费全文 | 36035篇 |
免费 | 4091篇 |
国内免费 | 1916篇 |
专业分类
电工技术 | 2538篇 |
技术理论 | 4篇 |
综合类 | 3239篇 |
化学工业 | 3921篇 |
金属工艺 | 1701篇 |
机械仪表 | 2398篇 |
建筑科学 | 4204篇 |
矿业工程 | 941篇 |
能源动力 | 1272篇 |
轻工业 | 6178篇 |
水利工程 | 1370篇 |
石油天然气 | 1227篇 |
武器工业 | 776篇 |
无线电 | 1854篇 |
一般工业技术 | 5360篇 |
冶金工业 | 1879篇 |
原子能技术 | 610篇 |
自动化技术 | 2570篇 |
出版年
2024年 | 241篇 |
2023年 | 765篇 |
2022年 | 1548篇 |
2021年 | 1661篇 |
2020年 | 1711篇 |
2019年 | 1410篇 |
2018年 | 1397篇 |
2017年 | 1634篇 |
2016年 | 1769篇 |
2015年 | 1791篇 |
2014年 | 2298篇 |
2013年 | 2575篇 |
2012年 | 2814篇 |
2011年 | 2937篇 |
2010年 | 1942篇 |
2009年 | 1831篇 |
2008年 | 1669篇 |
2007年 | 1874篇 |
2006年 | 1690篇 |
2005年 | 1381篇 |
2004年 | 1089篇 |
2003年 | 930篇 |
2002年 | 732篇 |
2001年 | 677篇 |
2000年 | 563篇 |
1999年 | 499篇 |
1998年 | 421篇 |
1997年 | 314篇 |
1996年 | 283篇 |
1995年 | 263篇 |
1994年 | 229篇 |
1993年 | 173篇 |
1992年 | 145篇 |
1991年 | 107篇 |
1990年 | 114篇 |
1989年 | 73篇 |
1988年 | 64篇 |
1987年 | 46篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 18篇 |
1982年 | 26篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1965年 | 16篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1961年 | 13篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A review of robust design methods for multiple responses 总被引:1,自引:0,他引:1
Terrence E. Murphy Kwok-Leung Tsui Janet K. Allen 《Research in Engineering Design》2005,16(3):118-132
Problems in engineering design often involve determining design variable settings to optimize individual product performance
for multiple criteria, which are often in conflict. We review mathematically rigorous techniques from the statistical literature
for finding a vector x of design variable settings, which produces an optimal compromise solution among a group of prioritized response variables.
The best compromise solution is typically gained by optimizing an objective function, which incorporates the prioritized demands
of multiple responses. Since most multi-response objective functions are constructed by combining the functions used to optimize
univariate responses, a review of the prominent univariate approaches is presented first. A multivariate approach from the
engineering literature called the compromise Decision Support Problem is also reviewed. Finally a table comparing the relative
merits of the different multivariate approaches summarizes the article in a concise and user-friendly fashion. 相似文献
72.
73.
Here, we report on the application of corroles as analytically active compounds in liquid membrane electrodes (ISE) that are sensitive towards salicylic acid and salicylate.The potentiometric signals generated by corrole-incorporated ISEs strongly depend on the pH of the aqueous sample solution and the membrane composition, such as the presence of lipophilic sites. Corrole incorporating ISEs are characterised by a low detection limit (4.0 × 10−5 M) and a wide linear range (4.0 × 10−5 to 5.3 × 10−3 M). Also, they are free from interference versus other organic anions.The mechanism of the generation of the potentiometric signals of corrole incorporating ISEs in the presence of salicylate anion, as well salicylic acid, will be discussed. 相似文献
74.
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
75.
准噶尔盆地腹部普遍发育深层(大于4000m)超压系统,很多钻井都钻遇超压。通过对超压段钻井、地质、测井、地震特征系统研究发现,超压段泥浆密度大幅增加,具有高声波时差、低电阻率以及地震低速的超压响应特征。利用Dix公式计算地震层速度和利用Fillippone公式计算地层压力,得到超压数据体。准噶尔盆地腹部超压在白垩系及其以下沉积地层中均有分布,超压层的深度范围不同。分1井西凹陷边缘以及昌吉凹陷西南有空层现象。超压顶面分布的层位由北往南、从东到西逐渐变浅,从三叠系顶部到白垩系底部。深部超压对油气分布和富集有着重要的控制作用,准噶尔盆地腹部超压层分布的研究将对本区油气勘探起积极的推动作用。 相似文献
76.
77.
Results of metal testing in impact tension–compression and indentation are analyzed. As the analysis of these data demonstrates, the strength of metals increases greatly with strain rates and at moderate indentation rates. At high indentation rates, a decrease in the specific energy (per unit volume of a displaced material) necessary for the formation of a conical cavity was observed. The account of the effects of viscosity, temperature increase upon plastic deformation and its localization can be used to explain the above phenomena. 相似文献
78.
农业重组微生物生物安全研究进展 总被引:2,自引:2,他引:0
综述了近年来农业重组微生物的研究现状和进展 ,详细介绍农业重组微生物环境释放的监控方法以及对环境的冲击作用 ,对一些有关生物安全研究的热点问题进行了探讨 相似文献
79.
80.
Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献