全文获取类型
收费全文 | 10751篇 |
免费 | 293篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 204篇 |
综合类 | 10篇 |
化学工业 | 2389篇 |
金属工艺 | 217篇 |
机械仪表 | 208篇 |
建筑科学 | 641篇 |
矿业工程 | 26篇 |
能源动力 | 251篇 |
轻工业 | 968篇 |
水利工程 | 103篇 |
石油天然气 | 21篇 |
武器工业 | 2篇 |
无线电 | 705篇 |
一般工业技术 | 1555篇 |
冶金工业 | 2061篇 |
原子能技术 | 119篇 |
自动化技术 | 1577篇 |
出版年
2022年 | 100篇 |
2021年 | 146篇 |
2020年 | 106篇 |
2019年 | 151篇 |
2018年 | 136篇 |
2017年 | 132篇 |
2016年 | 164篇 |
2015年 | 170篇 |
2014年 | 238篇 |
2013年 | 544篇 |
2012年 | 374篇 |
2011年 | 543篇 |
2010年 | 402篇 |
2009年 | 380篇 |
2008年 | 494篇 |
2007年 | 424篇 |
2006年 | 405篇 |
2005年 | 315篇 |
2004年 | 300篇 |
2003年 | 275篇 |
2002年 | 289篇 |
2001年 | 168篇 |
2000年 | 152篇 |
1999年 | 179篇 |
1998年 | 246篇 |
1997年 | 215篇 |
1996年 | 189篇 |
1995年 | 188篇 |
1994年 | 181篇 |
1993年 | 160篇 |
1992年 | 144篇 |
1991年 | 117篇 |
1990年 | 141篇 |
1989年 | 154篇 |
1988年 | 114篇 |
1987年 | 118篇 |
1986年 | 134篇 |
1985年 | 162篇 |
1984年 | 136篇 |
1983年 | 157篇 |
1982年 | 137篇 |
1981年 | 131篇 |
1980年 | 116篇 |
1979年 | 125篇 |
1978年 | 118篇 |
1977年 | 126篇 |
1976年 | 128篇 |
1975年 | 123篇 |
1974年 | 99篇 |
1973年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Kazdin Alan E.; Bass Debra; Siegel Todd; Thomas Christopher 《Canadian Metallurgical Quarterly》1989,57(4):522
112 children (aged 7-13 yrs) were randomly assigned to one of three treatments: problem-solving skills training (PSST), problem-solving skills training with in vivo practice (PSST-P), which included therapeutically planned activities to extend training to settings outside of treatment, or client-centered relationship therapy (RT). PSST and PSST-P children showed significantly greater reductions in antisocial behavior and overall behavior problems, and greater increases in prosocial behavior than RT children. These effects were evident on measures obtained immediately after treatment and at a 1-year follow-up, and on measures of child performance at home and at school. PSST-P children showed greater changes than PSST children on measures of functioning at school at posttreatment, but these differences were no longer evident at follow-up. Children in both PSST conditions showed significant reductions in deviant behavior and improvements in prosocial behavior from pretreatment to follow-up, whereas RT children tended to remain at their pretreatment level of functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
14.
Larissa Canilha Walter Carvalho Marco Giulietti Maria Das Graças Almeida Felipe João Batista Almeida E Silva 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(5):715-721
BACKGROUND: Xylitol bioproduction from lignocellulosic residues comprises hydrolysis of the hemicellulose, detoxification of the hydrolysate, bioconversion of the xylose, and recovery of xylitol from the fermented hydrolysate. There are relatively few reports on xylitol recovery from fermented media. In the present study, ion‐exchange resins were used to clarify a fermented wheat straw hemicellulosic hydrolysate, which was then vacuum‐concentrated and submitted to cooling in the presence of ethanol for xylitol crystallization. RESULTS: Sequential adsorption into two anion‐exchange resins (A‐860S and A‐500PS) promoted considerable reductions in the content of soluble by‐products (up to 97.5%) and in medium coloration (99.5%). Vacuum concentration led to a dark‐colored viscous solution that inhibited xylitol crystallization. This inhibition could be overcome by mixing the concentrated medium with a commercial xylitol solution. Such a strategy led to xylitol crystals with up to 95.9% purity. The crystallization yield (43.5%) was close to that observed when using commercial xylitol solution (51.4%). CONCLUSION: The experimental data demonstrate the feasibility of using ion‐exchange resins followed by cooling in the presence of ethanol as a strategy to promote the fast recovery and purification of xylitol from hemicellulose‐derived fermentation media. Copyright © 2008 Society of Chemical Industry 相似文献
15.
Tuan Vo-Dinh Guy Griffin David L. Stokes Alan Wintenberg 《Sensors and actuators. B, Chemical》2003,90(1-3):104-111
We describe a multi-functional biochip (MFB), which uses two different types of bioreceptors, including nucleic acid and antibody probes, on a single platform. The multi-functional capability of the MFB device for biomedical diagnostics is illustrated by measurements of DNA probes specific to gene fragments of Bacillus anthracis and antibody probes targeted to Escherichia coli. Calibration curves for monitoring pathogenic species using antibody probes against E. coli and DNA probes for B. anthracis illustrate the capability of the device for medical diagnostics and for quantitative detection of pathogenic agents. 相似文献
16.
Alan A. Luo Robert C. Kubic John M. Tartaglia 《Metallurgical and Materials Transactions A》2003,34(11):2549-2557
This study investigated the microstructure and fatigue properties of hydroformed sections of the 5754 and 6063 aluminum alloys.
The second-phase particles in 6063-T7 are identified as a mixture of Al12Fe3Si and Al9Fe2Si2, with a slightly higher fraction of the former. The constituent particles in the 5754 alloy are Al4Mn-type hexagonal compounds, where Mn is partially substituted by various other elements, resulting in Al4(Fe,Mn,Si,Cr). The results show that despite its lower yield strength, the hydroformed 5754 alloy has higher ultimate tensile
strength, ductility, and, more importantly, higher fatigue resistance than the 6063 material. Both crystallographic stage
I and noncrystallographic stage II cracking are found in the 6063-T7 samples, but only stage II cracking is observed in the
5754 alloy. This implies that the low fatigue strength of 6063-T7 is related to its relatively large grain size, resulting
in rapid stage I crack propagation. The higher fatigue lives of the 5754 alloy compared to the 6063 alloy in both the low-
and high-cycle life regimes are due to the increased fatigue-crack-initiation and propagation resistance of the 5754 alloy
and its probable cyclic strain-hardening behavior. 相似文献
17.
18.
Hans-Dirk Walter 《Informatik-Spektrum》2008,31(4):333-343
Zusammenfassung ,,Rich Internet Applications“ (RIA) sind Webapplikationen, die mit einer wesentlich interaktiveren Benutzerschnittstelle ausgestattet
sind, als wir das bisher von den auf HTML basierten ,,poor ugly web applications“ (PUWA) gewohnt waren. 相似文献
19.
Diane M. Hopkins Alan D. Jackson Kenneth Oates 《Microscopy research and technique》1991,18(2):176-182
The standardisation of frozen hydrated bulk biological specimens using gelatin standards is described. The relationship between corrected elemental X-ray counts and ionic concentration was found to be linear, and minimum detectable limits for each element are stated. Variations in uncorrected standard curves were found to be due to changes in aluminium coating thickness. There was an inverse relationship between coating thickness and elemental X-ray counts. The factors causing this are discussed. To avoid errors arising from inconsistent aluminium thickness, experimental material should only be compared with standards of similar aluminium net counts. This can be achieved most easily by mounting and analysing specimen and standard together. 相似文献
20.
This article argues that an iconic event in the history of helping research--the story of the 38 witnesses who remained inactive during the murder of Kitty Genovese--is not supported by the available evidence. Using archive material, the authors show that there is no evidence for the presence of 38 witnesses, or that witnesses observed the murder, or that witnesses remained inactive. Drawing a distinction between the robust bystander research tradition and the story of the 38 witnesses, the authors explore the consequences of the story for the discipline of psychology. They argue that the story itself plays a key role in psychology textbooks. They also suggest that the story marks a new way of conceptualizing the dangers of immersion in social groups. Finally, they suggest that the story itself has become a modern parable, the telling of which has served to limit the scope of inquiry into emergency helping. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献