全文获取类型
收费全文 | 24009篇 |
免费 | 2811篇 |
国内免费 | 1337篇 |
专业分类
电工技术 | 2184篇 |
综合类 | 2315篇 |
化学工业 | 2187篇 |
金属工艺 | 531篇 |
机械仪表 | 1530篇 |
建筑科学 | 3052篇 |
矿业工程 | 352篇 |
能源动力 | 928篇 |
轻工业 | 4862篇 |
水利工程 | 694篇 |
石油天然气 | 854篇 |
武器工业 | 298篇 |
无线电 | 1581篇 |
一般工业技术 | 3077篇 |
冶金工业 | 1189篇 |
原子能技术 | 467篇 |
自动化技术 | 2056篇 |
出版年
2024年 | 124篇 |
2023年 | 519篇 |
2022年 | 1011篇 |
2021年 | 1263篇 |
2020年 | 1159篇 |
2019年 | 1020篇 |
2018年 | 893篇 |
2017年 | 1058篇 |
2016年 | 1101篇 |
2015年 | 1163篇 |
2014年 | 1432篇 |
2013年 | 1560篇 |
2012年 | 2047篇 |
2011年 | 2078篇 |
2010年 | 1306篇 |
2009年 | 1283篇 |
2008年 | 1131篇 |
2007年 | 1265篇 |
2006年 | 1117篇 |
2005年 | 925篇 |
2004年 | 716篇 |
2003年 | 624篇 |
2002年 | 464篇 |
2001年 | 410篇 |
2000年 | 331篇 |
1999年 | 314篇 |
1998年 | 274篇 |
1997年 | 206篇 |
1996年 | 176篇 |
1995年 | 173篇 |
1994年 | 134篇 |
1993年 | 123篇 |
1992年 | 110篇 |
1991年 | 74篇 |
1990年 | 75篇 |
1989年 | 55篇 |
1988年 | 48篇 |
1987年 | 41篇 |
1986年 | 27篇 |
1985年 | 31篇 |
1984年 | 26篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1965年 | 15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 234 毫秒
61.
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
62.
63.
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
64.
用SAS9.0中的响应曲面试验设计,研究了盐浓度、水分活度、发酵温度、发酵时间和糖浓度等环境因子对发酵香肠发酵过程中细菌总数变化的影响,建立科学的数学模型,此数学模型能够表达发酵香肠发酵过程中细菌总数的变化趋势。用建立的数学模型对发酵过程中的微生物进行了预测,结果可靠。细菌总数与实验测定数据进行比较,平均误差范围是-10.20%~8.43%。此数学模型为发酵香肠发酵过程的控制,提高发酵肉制品的安全性,缩短生产周期提供了依据,也是微生物预报的重要基础。 相似文献
65.
Herbert S. Bennett 《Journal of research of the National Institute of Standards and Technology》2007,112(4):209-221
In this paper, we present the theory for calculating Raman line shapes as functions of the Fermi energy and finite temperatures in zinc blende, n-type GaAs for donor densities between 1016 cm−3 and 1019 cm−3. Compared to other theories, this theory is unique in two respects: 1) the many-body effects are treated self-consistently and 2) the theory is valid at room temperature for arbitrary values of the ratio R = (Q2/α), where Q is the magnitude of the normalized wave vector and α is the normalized frequency used in the Raman measurements. These calculations solve the charge neutrality equation self-consistently for a two-band model of GaAs at 300 K that includes the effects of high carrier concentrations and dopant densities on the perturbed densities of states used to calculate the Fermi energy as a function of temperature. The results are then applied to obtain the carrier concentrations from Fermi energies in the context of line shapes in Raman spectra due to the coupling between longitudinal optical phonons and plasmons. Raman measurements have been proposed as a non-destructive method for wafer acceptance tests of carrier density in semiconductor epilayers. The interpretation of Raman spectra to determine the majority electron density in n-type semiconductors requires an interdisciplinary effort involving experiments, theory, and computer-based simulations and visualizations of the theoretical calculations. 相似文献
66.
Prepulse inhibition (PPI) refers to a reduction in the startle response to a strong sensory stimulus when this stimulus is preceded by a weaker stimulus--the prepulse. PPI reflects a nonlearned sensorimotor gating mechanism and also shows a robust gender difference, with women exhibiting lower PPI than men. The present study examined the eyeblink startle responses to acoustic stimuli of 59 healthy heterosexual and homosexual men and women. Homosexual women showed significantly masculinized PPI compared with heterosexual women, whereas no difference was observed in PPI between homosexual and heterosexual men. These data provide the first evidence for within-gender differences in basic sensorimotor gating mechanisms and implicate the known neural substrates of PPI in human sexual orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
It has been reported that it is harder to switch to a strong, well-practiced task from a weaker, less-practiced task than vice versa. Three experiments replicated this surprising asymmetry and investigated how it is affected by a reduction in interference between tasks. Experiment 1 progressively delayed the onset of the stimulus attribute associated with the stronger task. Experiments 2 and 3 separated the response sets of the tasks. Both manipulations reduced, without eliminating, interference of the stronger with the weaker task but reversed the asymmetry of switch costs, resulting in a larger cost of switching to the weaker task. The results are interpreted in terms of a model of the interactions between control input, task strength, and task priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
The authors used visual search tasks in which components of the classic flanker task (B. A. Eriksen & C. W. Eriksen, 1974) were introduced. In several experiments the authors obtained evidence of parallel search for a target among distractor elements. Therefore, 2-stage models of visual search predict no effect of the identity of those distractors. However, clear compatibility effects of the distractors were obtained: Responses were faster when the distractors were compatible with the response than when they were incompatible. These results show that even in parallel search tasks identity information is extracted from the distractors. In addition, alternative interpretations of the results in terms of the occasional identification of a distractor before or after the target was identified could be ruled out. The results showed that flat search slopes obtained in visual search experiments provide no benchmark for preattentive processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
A modified rainflow counting method 总被引:1,自引:0,他引:1
Nie Hong 《International Journal of Fatigue》1991,13(6):465-469
The rainflow counting method is commonly recognized to be a good cyclic counting method in fatigue life prediction and for testing engineering components and structures. However, it has some shortcomings, which are pointed out in this paper in connection with the analysis of the stress-strain response. A modified rainflow counting method is presented. Case studies show that all the cycles really existing in the stress-strain response that cannot be counted by the rainflow counting method can be counted by the modified rainflow counting method. So it can be said that the modified rainflow counting method is a more reasonable cycling counting method than the traditional rainflow counting method. 相似文献