全文获取类型
收费全文 | 52185篇 |
免费 | 4678篇 |
国内免费 | 3272篇 |
专业分类
电工技术 | 3026篇 |
技术理论 | 4篇 |
综合类 | 6630篇 |
化学工业 | 5805篇 |
金属工艺 | 1620篇 |
机械仪表 | 1976篇 |
建筑科学 | 7335篇 |
矿业工程 | 2447篇 |
能源动力 | 1414篇 |
轻工业 | 3512篇 |
水利工程 | 2398篇 |
石油天然气 | 2649篇 |
武器工业 | 727篇 |
无线电 | 4522篇 |
一般工业技术 | 4719篇 |
冶金工业 | 2832篇 |
原子能技术 | 560篇 |
自动化技术 | 7959篇 |
出版年
2024年 | 205篇 |
2023年 | 714篇 |
2022年 | 1163篇 |
2021年 | 1420篇 |
2020年 | 1373篇 |
2019年 | 1305篇 |
2018年 | 1177篇 |
2017年 | 1420篇 |
2016年 | 1608篇 |
2015年 | 1715篇 |
2014年 | 2736篇 |
2013年 | 2917篇 |
2012年 | 3379篇 |
2011年 | 3636篇 |
2010年 | 2851篇 |
2009年 | 3117篇 |
2008年 | 2869篇 |
2007年 | 3615篇 |
2006年 | 3268篇 |
2005年 | 2954篇 |
2004年 | 2496篇 |
2003年 | 2267篇 |
2002年 | 1998篇 |
2001年 | 1667篇 |
2000年 | 1400篇 |
1999年 | 1169篇 |
1998年 | 881篇 |
1997年 | 771篇 |
1996年 | 640篇 |
1995年 | 613篇 |
1994年 | 481篇 |
1993年 | 398篇 |
1992年 | 325篇 |
1991年 | 234篇 |
1990年 | 239篇 |
1989年 | 199篇 |
1988年 | 164篇 |
1987年 | 127篇 |
1986年 | 81篇 |
1985年 | 91篇 |
1984年 | 67篇 |
1983年 | 42篇 |
1982年 | 32篇 |
1981年 | 37篇 |
1980年 | 37篇 |
1979年 | 36篇 |
1978年 | 20篇 |
1977年 | 22篇 |
1976年 | 20篇 |
1975年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
谌行星 《湖南冶金职业技术学院学报》2006,6(2):262-264
在用基本不等式求最值时,大家都熟悉一个口诀:"一正二定三相等",但是有许多学生在怎样保证定值和相等时不知道该如何变形.为了解决学生的困难和困惑,我根据自己的经验,概括为两句口诀:"一正二定三相等,巧变四数定乾坤". 相似文献
52.
Alexandre Szklo Giovani Machado Roberto Schaeffer Jacqueline Mariano Janaí na Sala Marina Tavares 《Catalysis Today》2005,106(1-4):123-128
This paper assesses the impacts of a GTL plant on the expansion of Brazil's oil refining segment. The GTL plant (50,000 bpd) was sized to start up operations in 2015, producing diesel and naphtha through the indirect route (FT-synthesis). This plant will consume the non-associated natural gas production from the recent discoveries at the Santos Basin (around 419 Bm3), and the associated gas production from the Campos Basin. Both basins are located in the Southeast of Brazil, the most populated, rich and industrialized region of the country. Two different criteria for refinery expansion were simulated in order to meet oil product demand scenarios. Findings show that depending on the refinery expansion criteria considered GTL will play a fundamental hole to meet the oil product demand forecast to Brazil in the next 10 years. 相似文献
53.
A probabilistic model for cleavage fracture with a length scale--parameter estimation and predictions of stationary crack experiments 总被引:1,自引:0,他引:1
This study presents a large experimental investigation in the transition temperature region on a modified A508 steel. Tests were carried out on single-edge-notch-bend specimens with three different crack depth over specimen width ratios to capture the strong constraint effect on fracture toughness. Three test temperatures were considered, covering a range of 85 °C. All specimens failed by cleavage fracture prior to ductile tearing. A recently proposed probabilistic model for the cumulative failure by cleavage was applied to the comprehensive sets of experimental data. This modified weakest link model incorporates a length scale, which together with a threshold stress reduce the scatter in predicted toughness distributions as well as introduces a fracture toughness threshold value. Model parameters were estimated by a robust procedure, which is crucial in applications of probabilistic models to real structures. The conformity between predicted and experimental toughness distributions, respectively, were notable at all the test temperatures. 相似文献
54.
介绍了钻孔灌注桩成孔质量的影响因素 ,详细叙述了钢筋笼的制作和吊放处理步骤 ,阐述了断桩发生的原因 ,提出了具体的防治措施 ,经实践效果良好 相似文献
55.
张小蹦 《西安邮电学院学报》2008,13(1):139-140,148
本文的主要目的是利用初等方法研究Smarandache可乘函数在简单数集中的均值性质,并给出一个有趣的渐近公式。 相似文献
56.
周明 《徐州工程学院学报》2008,23(3):44-47
张仲谋教授的新著《宋词欣赏教程》,是南京大学出版社出版的“江苏省高等学校精品教材系列”中的一种。该书共8章,既构成一个严谨的教学体系,又多有创新出彩之处;对于词的艺术个性有深刻的把握和精当的阐发;又善于引导学生,循循善诱。该书既是教材,亦具有学术专著的品格。 相似文献
57.
The discrimination problem for two normal populations with the same covariance matrix when additional information on the population is available is considered. A study of the robustness properties against training sample contamination of classification rules that incorporate this additional information is performed. These rules have received recently attention where their total misclassification probability (TMP) is proved to be lower than Fisher's linear discriminant rule. The results of a simulation study on the TMP which compares the behaviour of the new rules against Fisher's rule and some of its robustified versions under different types of contamination are presented. These results show that the rules that incorporate the additional information not only have lower TMP, but they also prevent against some types of contamination. In order to achieve prevention from all types of contamination a robustifed version of these rules is recommended. 相似文献
58.
Mirna Suárez-Quiroz Béatrice De Louise Oscar Gonzalez-Rios Michel Barel Bernard Guyot Sabine Schorr-Galindo & Joseph-Pierre Guiraud 《International Journal of Food Science & Technology》2005,40(6):605-611
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety. 相似文献
59.
Gleevec是抑制致癌的融合蛋白BCR-ABL的一种分子靶向治疗药物,BCR-ABL是一种与慢性髓细胞性白血病(CML)有关的酪氨酸激酶抑制剂。用Gleevec选择性地抑制BCR-ABL活性在治疗CML中显示出很好的效果,特别是在CML慢性期,因此,监测疗效非常重要。现就Gleevec的研究进展及如何监测其在CML中的疗效作一简单综述。 相似文献
60.