全文获取类型
收费全文 | 29282篇 |
免费 | 2179篇 |
国内免费 | 1232篇 |
专业分类
电工技术 | 1388篇 |
技术理论 | 6篇 |
综合类 | 1946篇 |
化学工业 | 5127篇 |
金属工艺 | 1839篇 |
机械仪表 | 1807篇 |
建筑科学 | 2265篇 |
矿业工程 | 798篇 |
能源动力 | 792篇 |
轻工业 | 1678篇 |
水利工程 | 500篇 |
石油天然气 | 1956篇 |
武器工业 | 159篇 |
无线电 | 3173篇 |
一般工业技术 | 3687篇 |
冶金工业 | 1583篇 |
原子能技术 | 390篇 |
自动化技术 | 3599篇 |
出版年
2024年 | 109篇 |
2023年 | 468篇 |
2022年 | 743篇 |
2021年 | 1063篇 |
2020年 | 810篇 |
2019年 | 682篇 |
2018年 | 779篇 |
2017年 | 845篇 |
2016年 | 844篇 |
2015年 | 1001篇 |
2014年 | 1345篇 |
2013年 | 1649篇 |
2012年 | 1679篇 |
2011年 | 1931篇 |
2010年 | 1734篇 |
2009年 | 1680篇 |
2008年 | 1588篇 |
2007年 | 1426篇 |
2006年 | 1425篇 |
2005年 | 1292篇 |
2004年 | 975篇 |
2003年 | 1000篇 |
2002年 | 1061篇 |
2001年 | 1026篇 |
2000年 | 796篇 |
1999年 | 871篇 |
1998年 | 727篇 |
1997年 | 579篇 |
1996年 | 524篇 |
1995年 | 430篇 |
1994年 | 378篇 |
1993年 | 266篇 |
1992年 | 208篇 |
1991年 | 153篇 |
1990年 | 119篇 |
1989年 | 106篇 |
1988年 | 75篇 |
1987年 | 51篇 |
1986年 | 54篇 |
1985年 | 25篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1976年 | 13篇 |
1970年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
X.Y Fu M Ishii 《Nuclear Engineering and Design》2003,219(2):143-168
The prediction of the dynamical evolution of interfacial area concentration is one of the most challenging tasks in two-fluid model application. This paper is focused on developing theoretical models for interfacial area source and sink terms for a two-group interfacial area transport equation. Mechanistic models of major fluid particle interaction phenomena involving two bubble groups are proposed, including the shearing-off of small bubbles from slug/cap bubbles, the wake entrainment of spherical/distorted bubble group into slug/cap bubble group, the wake acceleration and coalescence between slug/cap bubbles, and the breakup of slug/cap bubbles due to turbulent eddy impacts. The existing one-group interaction terms are extended in considering the generation of cap bubbles, as well as different parametric dependences when these terms are applied to the slug flow regime. The complete set of modeling equations is closed and continuously covers the bubbly flow, slug flow, and churn-turbulent flow regimes. Prediction of the interfacial area concentration evolution using a one-dimensional two-group transport equation and evaluation with experimental results are described in a companion paper. 相似文献
53.
随着化工及军工企业的扩建,防爆起重机作为一种特殊用途的起重机需求量与日俱增,寻求设计出更为先进实用的产品来满足生产的需要已成为起重机生产厂的目标。目前在防爆起重机的变频调速不很成熟的前提下,对双速电机的控制方案作进一步改进已成为必要。 相似文献
54.
In this paper, we shall discuss oscillatory behavior of the solutions of difference equations, including the self-adjoint second-order linear equation and the discrete version of the nonlinear wave equation. Our work is to give sufficient conditions such that every nontrivial solution of the equations oscillates. 相似文献
55.
对文献[7]发展的(e,2e)反应多重散射理论做了改进用得到的波函数计算了能量为544eV的(e,2e)反应的截面,结果表明改进后的多重散射理论与实验符合较好 相似文献
56.
付毅迅 《石油化工高等学校学报》1997,10(2):20-22
对传统卡尔费休试剂的不足进行了分析 ,提出了一种用有机胺代替吡啶 ,用多元醇衍生物代替甲醇的无吡啶、无甲醇、高效低毒、性能稳定、应用范围广泛、克服了传统卡尔费休试剂无法测定含羰基化合物样品中微量水弊端的新型卡尔费休试剂。经与英国BDH公司、北京石油科学研究院和山东淄博无线电一厂生产的市售卡尔费休试剂的对比分析和工厂现场试验证明本试剂可完全替代传统和进口卡尔费休试剂对石油产品、化工产品及含有羰基化合物样品中的微量水分分析。分析误差符合GB6 0 6 77规定的范围 相似文献
57.
Fu-Lai Chung Tak-Chung Fu Ng V. Luk R.W.P. 《Evolutionary Computation, IEEE Transactions on》2004,8(5):471-489
Time series data, due to their numerical and continuous nature, are difficult to process, analyze, and mine. However, these tasks become easier when the data can be transformed into meaningful symbols. Most recent works on time series only address how to identify a given pattern from a time series and do not consider the problem of identifying a suitable set of time points for segmenting the time series in accordance with a given set of pattern templates (e.g., a set of technical patterns for stock analysis). However, the use of fixed-length segmentation is an oversimplified approach to this problem; hence, a dynamic approach (with high controllability) is preferable so that the time series can be segmented flexibly and effectively according to the needs of the users and the applications. In view of the fact that this segmentation problem is an optimization problem and evolutionary computation is an appropriate tool to solve it, we propose an evolutionary time series segmentation algorithm. This approach allows a sizeable set of pattern templates to be generated for mining or query. In addition, defining similarity between time series (or time series segments) is of fundamental importance in fitness computation. By identifying the perceptually important points directly from the time domain, time series segments and templates of different lengths can be compared and intuitive pattern matching can be carried out in an effective and efficient manner. Encouraging experimental results are reported from tests that segment both artificial time series generated from the combinations of pattern templates and the time series of selected Hong Kong stocks. 相似文献
58.
59.
用三氯化铁-2,2'-联吡啶-1-嗅乙基苯催化聚合苯乙烯,研究了聚合反应条件对聚合的影响,三氯化铁/2,2'-联吡啶/1-溴乙基苯摩尔比对聚合的影响,用凝胶渗透色谱研究了分子量和分子量分布。 相似文献
60.
Tang Y.B. Chen Y.G. Teng B.H. Fu H. Li H.X. Tu M.J. 《IEEE transactions on magnetics》2004,40(3):1597-1600
We calculate the magnetic field distribution of a permanent magnetic circuit with an air gap in a magnetic refrigerator by a finite-element method, and compare the field strengths of different structural parameters of the magnetic circuit. We show how the structure of the magnetic circuit can be optimized and present some approaches to improve the structure for a specific magnetic circuit. The main purpose is to provide basic parameters for the design of a practical magnetic refrigerator. 相似文献