全文获取类型
收费全文 | 9516篇 |
免费 | 677篇 |
国内免费 | 155篇 |
专业分类
电工技术 | 27篇 |
综合类 | 383篇 |
化学工业 | 5276篇 |
金属工艺 | 222篇 |
机械仪表 | 74篇 |
建筑科学 | 110篇 |
矿业工程 | 53篇 |
能源动力 | 181篇 |
轻工业 | 1899篇 |
水利工程 | 10篇 |
石油天然气 | 479篇 |
武器工业 | 5篇 |
无线电 | 122篇 |
一般工业技术 | 600篇 |
冶金工业 | 759篇 |
原子能技术 | 29篇 |
自动化技术 | 119篇 |
出版年
2024年 | 40篇 |
2023年 | 148篇 |
2022年 | 343篇 |
2021年 | 472篇 |
2020年 | 261篇 |
2019年 | 262篇 |
2018年 | 219篇 |
2017年 | 250篇 |
2016年 | 308篇 |
2015年 | 303篇 |
2014年 | 432篇 |
2013年 | 497篇 |
2012年 | 584篇 |
2011年 | 638篇 |
2010年 | 469篇 |
2009年 | 552篇 |
2008年 | 458篇 |
2007年 | 572篇 |
2006年 | 589篇 |
2005年 | 448篇 |
2004年 | 427篇 |
2003年 | 362篇 |
2002年 | 322篇 |
2001年 | 264篇 |
2000年 | 186篇 |
1999年 | 175篇 |
1998年 | 127篇 |
1997年 | 114篇 |
1996年 | 68篇 |
1995年 | 75篇 |
1994年 | 64篇 |
1993年 | 43篇 |
1992年 | 52篇 |
1991年 | 32篇 |
1990年 | 37篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1964年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
41.
Extracts of maleMamestra brassicae (L.) hairpencils were analyzed by capillary gas chromatography (GC) and by GC-mass spectrometry (GC-MS). The extracts were found to consist of six components. Benzaldehyde, 2-methylpropanoic acid, 2-methylbutanoic acid, and phenol were present in the extracts as well as the previously identified benzyl alcohol and phenyl ethanol. The two major components were 2-phenylethanol and 2-methylbutanoic acid. They represented, respectively, 74% and 12.5% of the total blend in 3-day-old male extracts. Electroantennograms were recorded on male and female antennae in response to stimulation by hairpencil compounds. Male and female antennae responded to each chemical but the female responses were significantly higher than those of the males. 相似文献
42.
仲丁醇含量对正丁烯直接水合法制仲丁醇的影响 总被引:1,自引:0,他引:1
研究了正丁烯直接水合法制仲丁醇工艺中原料水中仲丁醇含量对反应的影响.当原料水中含有少量仲丁醇时(约0.9%时),其对水合反应过程的转化率影响不大;原料水中含有少量仲丁醇时,反应过程的稳定性比较好.当水合反应的原料水中仲丁醇浓度增大时(原料水中仲丁醇浓度为2.0%左右时),反应过程的转化率明显下降.当水合反应的原料水中仲丁醇含量进一步增大时,反应过程的转化率下降明显,但呈非线性变化. 相似文献
43.
Aviles Fredy; Earleywine Mitchell; Pollock Vicki; Stratton Joy; Miller Norman 《Canadian Metallurgical Quarterly》2005,19(1):108
The authors examined alcohol's effect on triggered displaced aggression, the hostile reaction to a second provoking person after provocation from a first. Participants consumed an alcoholic or a nonalcoholic beverage. Subsequently, one individual provoked all of them with moderate intensity. Then, 2 groups were studied: those who received or who failed to receive a second provocation of minimal intensity. Consistent with prior research, participants who received a second, minimal provocation displayed more aggression than those who did not. After participants drank alcohol, the magnitude of this difference was significantly greater, indicating that alcohol increases triggered displaced aggression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
Performance of Alcohol and Safer Sex Change Rulers Compared With Readiness to Change Questionnaires.
LaBrie Joseph W.; Quinlan Thomas; Schiffman Jason E.; Earleywine Mitchell E. 《Canadian Metallurgical Quarterly》2005,19(1):112
As part of a larger intervention study, the authors hypothesized that change rulers created for alcohol and safer sex would be equivalent to longer questionnaires. Ninety-six male college students completed rulers and questionnaires for assessing behavior change readiness. Participants' scores on the rulers significantly correlated with their scores on the questionnaires (r = .77 for alcohol; r = .77 for safer sex). In both domains, the rulers outperformed the questionnaires in predicting behavioral intentions, suggesting that the rulers had at least comparable concurrent criterion validity. This finding is the first of its kind in the safe sex literature and suggests that quick assessments of readiness to change are possible. Because the rulers are a continuous measure, the results are consistent with the idea that the change process is continuous rather than a series of discrete stages. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Muraven Mark; Collins R. Lorraine; Morsheimer Elizabeth T.; Shiffman Saul; Paty Jean A. 《Canadian Metallurgical Quarterly》2005,19(3):253
The authors examined whether the reciprocal relationship between alcohol consumption and distress unfolded over time in 2 samples of social drinkers. Participants monitored their alcohol intake and their cognitive and emotional responses to that drinking on hand-held computers. On mornings after drinking, those who had violated their self-imposed limits the day before reported more guilt, even after controlling for acute negative symptoms of drinking and amount consumed. Reciprocally, guilt led to poorer self-regulation of alcohol intake: Greater distress over alcohol consumption was linked to more intake, intoxication, and more limit violations. Individual differences moderated the relationships among limit violations, distress, and drinking. Consistent with the limit violation effect, violating a limit produced distress over consumption among social drinkers, and they responded to that distress by drinking more. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Phillips Tamara J.; Broadbent Julie; Burkhart-Kasch Sue; Henderson Carly; Wenger Charlotte D.; McMullin Carrie; McKinnon Carrie S.; Cunningham Christopher L. 《Canadian Metallurgical Quarterly》2005,119(4):892
Short-term selective breeding created mouse lines divergent for ethanol drinking (high drinking short-term selected line [STDRHI], low drinking [STDRLO]) or ethanol-induced conditioned taste aversion (CTA; high [HTA], low [LTA]). Compared with STDRLO, STDRHI mice consumed more saccharin and less quinine, exhibited greater ethanol-induced conditioned place preference (CPP), and showed reduced ethanol stimulation and sensitization under some conditions; a line difference in ethanol-induced CTA was not consistently found. Compared with LTA, HTA mice consumed less ethanol but were similar in saccharin consumption, sensitivity to ethanol-induced CPP, and ethanol-induced locomotor stimulation and sensitization. These data suggest that ethanol drinking is genetically associated with several reward-and aversion-related traits. The interpretation of ethanol-induced CTA as more genetically distinct must be tempered by the inability to test the CTA lines beyond Selection Generation 2. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
有机醇的结构与色谱保留指数的相关性拓扑指数法研究 总被引:11,自引:6,他引:11
韩海洪 《计算机与应用化学》2003,20(5):687-689
通过计算40种有机醇化合物分子结构的拓扑指数,用多元线性回归将它与气相色谱保留指数进行关联分析,结果获得了良好的相关性,因此,对有机醇各组分在气相色谱上保留指数的理论预测,可作为在色谱分离过程中识别各组分的一种参考方法。 相似文献
48.
49.
对云南潦浒及寻甸褐煤树脂中醇类化学成分进行了GC-MS研究,探索褐煤树脂醇类作为药用资源的可能性.实验结果表明,树脂醇由正构烷醇、正构酮(甲基酮)、甾醇类、五环三萜醇及五环三萜酮所组成.褐煤树脂醇中均存在24-甲基-5β(H)-胆甾烷-3β-醇(C28H50O,MW.402),24-乙基胆甾-5,22-二烯-3β-醇(C29H48O,MW.412),24-乙基-5α(H)-胆甾烷-3β-醇(C29H52O,MW.416),23,24-二甲基胆甾-5-烯一3β-醇(C29H50O,MW.414),C29-5β(H),3β(OH)-甾醇(C29H52O,MW.416),24-异丙基胆甾-5,24(28)E-二烯-3β-醇(C30H50O,MW.426)等甾类物质.化学组成表明褐煤树脂作为药用资源是可能的. 相似文献
50.
Guyll Max; Spoth Richard L.; Chao Wei; Wickrama K. A. S.; Russell Daniel 《Canadian Metallurgical Quarterly》2004,18(2):293
Four years of longitudinal data from 373 families participating in a randomized intervention-control clinical trial were used to examine whether intervention effects on adolescent alcohol and tobacco use trajectories were moderated by family risk, as defined by parental social emotional maladjustment. Consistent with earlier outcome evaluations based on analyses of covariance, analyses confirmed that both the Preparing for the Drug Free Years program and the Iowa Strengthening Families Program favorably influenced alcohol use index trajectories across the time frame of the study; only the latter program, however, evidenced positive effects on a tobacco use index. Concerning the primary research question, analyses provided no support for family risk moderation of any intervention effect. Findings indicate the feasibility of developing universal preventive interventions that offer comparable benefits to all families. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献