全文获取类型
收费全文 | 19633篇 |
免费 | 2992篇 |
国内免费 | 1868篇 |
专业分类
电工技术 | 826篇 |
综合类 | 2137篇 |
化学工业 | 1824篇 |
金属工艺 | 609篇 |
机械仪表 | 1125篇 |
建筑科学 | 1414篇 |
矿业工程 | 619篇 |
能源动力 | 545篇 |
轻工业 | 538篇 |
水利工程 | 598篇 |
石油天然气 | 997篇 |
武器工业 | 1204篇 |
无线电 | 4619篇 |
一般工业技术 | 2076篇 |
冶金工业 | 712篇 |
原子能技术 | 506篇 |
自动化技术 | 4144篇 |
出版年
2024年 | 131篇 |
2023年 | 358篇 |
2022年 | 785篇 |
2021年 | 804篇 |
2020年 | 762篇 |
2019年 | 660篇 |
2018年 | 589篇 |
2017年 | 714篇 |
2016年 | 815篇 |
2015年 | 916篇 |
2014年 | 1297篇 |
2013年 | 1266篇 |
2012年 | 1528篇 |
2011年 | 1653篇 |
2010年 | 1314篇 |
2009年 | 1319篇 |
2008年 | 1199篇 |
2007年 | 1420篇 |
2006年 | 1181篇 |
2005年 | 1045篇 |
2004年 | 851篇 |
2003年 | 735篇 |
2002年 | 582篇 |
2001年 | 479篇 |
2000年 | 414篇 |
1999年 | 321篇 |
1998年 | 261篇 |
1997年 | 196篇 |
1996年 | 178篇 |
1995年 | 138篇 |
1994年 | 115篇 |
1993年 | 92篇 |
1992年 | 71篇 |
1991年 | 52篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 17篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1962年 | 2篇 |
1961年 | 2篇 |
1959年 | 5篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
111.
F. R. Perioto M. E. T. Alvarez W. A. Araujo M. R. Wolf‐Maciel R. Maciel Filho 《应用聚合物科学杂志》2008,110(6):3544-3551
A new calculation procedure for free‐volume parameters is considered in this work by using viscosity prediction methods and the Levenberg‐Marquardt calculation scheme. All parameters used in the Vrentas–Duda free‐volume theory can be estimated from pure component properties. The prediction results are compared with experimental data for some polymer/solvent systems. The diffusion coefficient calculated by Vrentas–Duda theory can be used in the modeling of membrane separation processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
112.
113.
People have knowledge about relationships (i.e., relational schemas) that is based on their experiences. Because most people have experience with complementary behavior (interaction partners behaving similarly in terms of affiliation but oppositely in terms of control), they expect complementary behavior in their relationships. Like other beliefs about relationships, expectations of complementarity affect self-construal. The authors provide evidence for complementary self-construal; people assimilate to relevant relationship partners on the affiliation dimension and contrast on the control dimension. Consistent with the proposed role of relationship knowledge in these effects, complementary self-construal was moderated by the familiarity of the target, whether people focused on their relationship with or the appearance of the target, and whether the context was relevant for the interpersonal dimension. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
114.
将3组不同纤维体积分数的整体毡采用等温CVD进行沉积热解炭增密,结合CVD沉积过程中整体毡内气体传质数学模型,研究了整体毡的纤维体积分数对CVD增密过程的影响,研究结果表明:纤维体积低的整体毡沉积时增重率高;纤维体积分数高的整体毡容易获得较高密度的C/C复合材料;纤维体积分数超过35%的整体毡经过300 h的化学气相沉积,坯体的体积密度能达到1.52 g/cm~3。 相似文献
115.
In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the target object (Experiment 1). Change detection performance remained excellent when the target object was not attended at change (Experiment 2) and when a concurrent verbal working memory load minimized the possibility of verbal encoding. (Experiment 3). Together, these data demonstrate that visual representations accumulate in memory from attended objects as the eyes and attention are oriented within a scene and that change blindness derives, at least in part, from retrieval and comparison failure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
116.
游强盛 《有色冶金设计与研究》2004,25(4):40-44
通过南昌市某快速路的设计实例,认识到搞好快速路沿线各交叉口的方案设计是快速路规划设计的关键内容。道路交叉口设计应注重交通功能分析,满足路口交通需求,同时也不能忽视立交的景观要求。 相似文献
117.
118.
119.
Neal E. Craft Katherine S. Epler Therese A. Butler Willie E. May Regina G. Ziegler 《Journal of research of the National Institute of Standards and Technology》1993,98(3):355-359
Aliquots of serum collected in a large case-control study of cervical cancer were stored at −70°C for up to 4 years during implementation of the study. When 500 μL serum aliquots were thawed in preparation for carotenoid and vitamin A assays, volumes were noticeably variable and fell below 500 μL in the majority of the samples. We were concerned about evaporation/sublimation during storage of the samples because loss of water would concentrate the analytes of interest. We evaluated the use of density and sodium ion concentration measurements to confirm its occurrence. We found that serum density was an unreliable indicator of extent of volume loss since the anticipated increases in density due to evaporation were of the same magnitude as inter-individual variation in serum density. In contrast, Na+ concentration is tightly regulated and would rise if water had been lost from the samples. In a representative sample of serum aliquots from the case-control study, 24 of 25 vials contained less than 500 μL of serum. The mean sodium ion concentration (138.1 ± 3.6 mmol/L) was within the normal range for human serum of 136–145 mmol/L, and no correlation was observed between serum volume and Na+ concentration. These results strongly suggest that the observed low volumes were not due to evaporative losses. Instead, the variably low volumes of serum aliquots were probably due to pipetting errors in the initial aliquotting resulting from the use of air-displacement pipettes. 相似文献
120.
Zinc dust and manganese powder as pigments were incorporated in epoxy-polyamide and butyl titanate medium, with different pigment volume concentration (PVC) ranging from 20 to 74. These protective coatings were coated on sand blasted mild steel substrates and immersed in 3 wt.% sodium chloride solution and the corrosion current was measured by the Tafel extrapolation method. From the corrosion current produced by these primers, the optimum level of the pigments in these binders was identified. Thus the protective performance of optimised primers was evaluated on a sand blasted mild steel surface by the Tafel polarisation method in 3 wt.% sodium chloride solution, over different periods of time. The results were found to be comparable with the salt spray test and galvanic current measurements. The manganese powder used for this investigation showed that it could be used as an alternative to zinc powder for metal rich primers. 相似文献