全文获取类型
收费全文 | 12506篇 |
免费 | 533篇 |
国内免费 | 368篇 |
专业分类
电工技术 | 185篇 |
综合类 | 653篇 |
化学工业 | 2195篇 |
金属工艺 | 888篇 |
机械仪表 | 1334篇 |
建筑科学 | 466篇 |
矿业工程 | 458篇 |
能源动力 | 369篇 |
轻工业 | 514篇 |
水利工程 | 82篇 |
石油天然气 | 234篇 |
武器工业 | 47篇 |
无线电 | 697篇 |
一般工业技术 | 1004篇 |
冶金工业 | 571篇 |
原子能技术 | 42篇 |
自动化技术 | 3668篇 |
出版年
2024年 | 23篇 |
2023年 | 96篇 |
2022年 | 126篇 |
2021年 | 201篇 |
2020年 | 242篇 |
2019年 | 210篇 |
2018年 | 168篇 |
2017年 | 237篇 |
2016年 | 320篇 |
2015年 | 386篇 |
2014年 | 629篇 |
2013年 | 752篇 |
2012年 | 618篇 |
2011年 | 928篇 |
2010年 | 566篇 |
2009年 | 634篇 |
2008年 | 590篇 |
2007年 | 762篇 |
2006年 | 733篇 |
2005年 | 692篇 |
2004年 | 626篇 |
2003年 | 586篇 |
2002年 | 514篇 |
2001年 | 419篇 |
2000年 | 385篇 |
1999年 | 334篇 |
1998年 | 308篇 |
1997年 | 226篇 |
1996年 | 192篇 |
1995年 | 180篇 |
1994年 | 171篇 |
1993年 | 116篇 |
1992年 | 98篇 |
1991年 | 64篇 |
1990年 | 58篇 |
1989年 | 34篇 |
1988年 | 38篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1974年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
CAPP系统中工艺卡片生成过程的研究 总被引:10,自引:1,他引:9
以AutoCAD2 0 0 0为开发平台、VC + + 6 0为开发环境、ObjectARX2 0 0 0为开发工具、SQLServer为后台数据库 ,通过编写writeText、fillGykztb、fillGykjtb等自定义函数 ,生成工艺卡片 ,并实现工序内容在工艺卡片中的分页显示等功能。 相似文献
22.
23.
R. B. Buitendijk 《Computational Economics》1988,1(2):79-96
SQL is often used to express questions imposed by users. It is well known that this process is not error-free in that it may result in syntactically or semantically incorrect SQL queries. This article is meant to probe deeper into SQL queries that are incorrect, due to delusion errors. A classification of natural language questions will be introduced. The purpose of this classification is two-fold. Firstly, it gives insight into possible errors and enables us to distinguish between types of errors. Secondly, it is a means of determining the influence of measures (for instance, SQL training) that can be taken to reduce the number of aforementioned errors. For discussion, several of these measures will be presented and related to the classification.Abbreviations RA
Relational algebra
- SQL
structured query language 相似文献
24.
An integrated process based on simultaneous solid-liquid extraction and liquid membrane separation is proposed for recovery and isolation of valuable species from botanicals. This integration provides complete exhausting of the solid material even in the case of very low solubility of the specified solute in the extracting solvent. Selectivity of the liquid membrane ensures a preferential transport of the desired solute from the native extract into the strip solution, while the other co-extracted species remain predominantly in the native extract. 相似文献
25.
Th. Pretorius G. Habedank J. Woitschig F. Vollertsen 《Materialwissenschaft und Werkstofftechnik》2006,37(1):85-91
Thermal treatments of steel components with the goal of hardening often result in distortion by releasing the residual stresses which were brought into the specimen during the preceding processing steps. The goal of the presented work is the minimization of this distortion. By generating definite residual stress fields and investigating the resulting distortion, the distortion mechanism can be observed in detail. A flexible and reproducible way to generate such residual stress fields inside a specimen is by means of local thermal treatment with a laser beam. Computer simulations as well as experiments were carried out using an idealized tooth of a gearwheel (finger sample) as a model system. The deformation of the samples due to the laser heat treatment and the stress fields generated inside the samples were determined with respect to different process parameters. 相似文献
26.
Transformations in machining. Part 1. enhancement of wavelet transformation neural network (WT-NN) combination with a preprocessor 总被引:2,自引:0,他引:2
X. Wang P. Chen I.N. Tansel Yenilmez A 《International Journal of Machine Tools and Manufacture》2006,46(1):36-42
Properly selected transformation methods obtain the most significant characteristics of metal cutting data efficiently and simplify the classification. Wavelet Transformation (WT) and Neural Networks (NN) combination was used to classify the experimental cutting force data of milling operations previously. Preprocessing (PreP) of the approximation coefficients of the WT is proposed just before the classification by using the Adaptive Resonance Theory (ART2) type NNs. Genetic Algorithm (GA) was used to estimate the weights of each coefficient of the PreP. The WT-PreP-NN (ART2) combination worked at lower vigilances by creating only a few meaningful categories without any errors. The WT-NN (ART2) combination could obtain the same error rate only if very high vigilances are used and many categories are allowed. 相似文献
27.
28.
介绍柳钢35t转炉方坯连铸机系统优化措施,通过优化使生产稳定性提高,铸坯质量得到改善,提高各项经济技术指标。 相似文献
29.
A model-based autotuning method consists of an identification and a regulator tuning phase. To achieve satisfactory performance and robustness, it is advisable that both phases be tailored a priori to the characteristics of the observed process dynamics. Such characteristics include, but are not limited to, the model structure. For example, overdamped and underdamped models with the same pole-zero structure are parametrised and controlled in different ways. Step response data, that are typically used for the identification phase in the autotuning context, can also be pre-processed to reveal those characteristics. This paper presents a step response classification method suitable for the above purpose. The method is based on a polygonal curve approximation technique for data pre-processing, followed by a neural network classifier. Only normalised I/O data are employed, so that the neural network can be trained off-line with simulated data. Simulation results are reported to show the effectiveness of the proposed classification method in terms of the achievable tuning results. 相似文献
30.