全文获取类型
收费全文 | 14985篇 |
免费 | 1959篇 |
国内免费 | 1054篇 |
专业分类
电工技术 | 817篇 |
综合类 | 1639篇 |
化学工业 | 861篇 |
金属工艺 | 1733篇 |
机械仪表 | 1347篇 |
建筑科学 | 3460篇 |
矿业工程 | 391篇 |
能源动力 | 255篇 |
轻工业 | 161篇 |
水利工程 | 742篇 |
石油天然气 | 566篇 |
武器工业 | 150篇 |
无线电 | 1220篇 |
一般工业技术 | 1444篇 |
冶金工业 | 447篇 |
原子能技术 | 43篇 |
自动化技术 | 2722篇 |
出版年
2024年 | 83篇 |
2023年 | 265篇 |
2022年 | 430篇 |
2021年 | 526篇 |
2020年 | 513篇 |
2019年 | 515篇 |
2018年 | 425篇 |
2017年 | 571篇 |
2016年 | 602篇 |
2015年 | 673篇 |
2014年 | 949篇 |
2013年 | 985篇 |
2012年 | 1081篇 |
2011年 | 1167篇 |
2010年 | 851篇 |
2009年 | 882篇 |
2008年 | 793篇 |
2007年 | 1009篇 |
2006年 | 923篇 |
2005年 | 791篇 |
2004年 | 669篇 |
2003年 | 586篇 |
2002年 | 433篇 |
2001年 | 384篇 |
2000年 | 347篇 |
1999年 | 289篇 |
1998年 | 234篇 |
1997年 | 200篇 |
1996年 | 152篇 |
1995年 | 126篇 |
1994年 | 119篇 |
1993年 | 92篇 |
1992年 | 60篇 |
1991年 | 52篇 |
1990年 | 49篇 |
1989年 | 40篇 |
1988年 | 26篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1965年 | 3篇 |
1963年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
We present a methodology for compiler synthesis based on Mosses-Watt's action semantics. Each action in action semantics notation is assigned specific “analysis functions”, such as a typing function and a binding-time function. When a language is given an action semantics, the typing and binding-time functions for the individual actions compose into typing and binding-time analyses for the language; these are implemented as the type checker and static semantics processor, respectively, in the synthesized compiler. Other analyses can be similarly formalized and implemented. We show a sample language semantics and its synthesized compiler, and we describe the compiler synthesizer that we have developed. 相似文献
42.
43.
The automated fare collection(AFC) system,also known as the transit smart card(SC) system,has gained more and more popularity among transit agencies worldwide.Compared with the conventional manual fare collection system,an AFC system has its inherent advantages in low labor cost and high efficiency for fare collection and transaction data archival.Although it is possible to collect highly valuable data from transit SC transactions,substantial efforts and methodologies are needed for extracting such data because most AFC systems are not initially designed for data collection.This is true especially for the Beijing AFC system,where a passenger’s boarding stop(origin) on a flat-rate bus is not recorded on the check-in scan.To extract passengers’ origin data from recorded SC transaction information,a Markov chain based Bayesian decision tree algorithm is developed in this study.Using the time invariance property of the Markov chain,the algorithm is further optimized and simplified to have a linear computational complexity.This algorithm is verified with transit vehicles equipped with global positioning system(GPS) data loggers.Our verification results demonstrated that the proposed algorithm is effective in extracting transit passengers’ origin information from SC transactions with a relatively high accuracy.Such transit origin data are highly valuable for transit system planning and route optimization. 相似文献
44.
强力输送带接头识别算法 总被引:2,自引:1,他引:1
针对现有的强力输送带故障实时检测方法存在故障定位困难的问题,以接头为基准参考点,提出了一种基于图像处理技术的强力输送带接头识别算法。该算法根据接头点的特征,把接头点用一个数值表示出来,并根据这个数值,以一种简单的方式区分出上、下接头点;然后根据接头的特征,并通过修改最长公共子序列算法的匹配方式,对接头进行识别。实际应用表明,该算法精度高、速度快,可有效识别强力输送带的接头,满足了强力输送带故障检测中接头定位的要求。 相似文献
45.
Estimation of elastic constant of rocks using an ANFIS approach 总被引:4,自引:0,他引:4
The engineering properties of the rocks have the most vital role in planning of rock excavation and construction for optimum utilization of earth resources with greater safety and least damage to surroundings. The design and construction of structure is influenced by physico-mechanical properties of rock mass. Young's modulus provides insight about the magnitude and characteristic of the rock mass deformation due to change in stress field. The determination of the Young's modulus in laboratory is very time consuming and costly. Therefore, basic rock properties like point load, density and water absorption have been used to predict the Young's modulus. Point load, density and water absorption can be easily determined in field as well as laboratory and are pertinent properties to characterize a rock mass. The artificial neural network (ANN), fuzzy inference system (FIS) and neuro fuzzy are promising techniques which have proven to be very reliable in recent years. In, present study, neuro fuzzy system is applied to predict the rock Young's modulus to overcome the limitation of ANN and fuzzy logic. Total 85 dataset were used for training the network and 10 dataset for testing and validation of network rules. The network performance indices correlation coefficient, mean absolute percentage error (MAPE), root mean square error (RMSE), and variance account for (VAF) are found to be 0.6643, 7.583, 6.799, and 91.95 respectively, which endow with high performance of predictive neuro-fuzzy system to make use for prediction of complex rock parameter. 相似文献
46.
A paradigm of scientific discovery is defined within a first-order logical framework. Within this paradigm, the concept of successful scientific inquiry is formalized and investigated. Among other results, it is shown that a simple method of scientific inquiry is universal in the sense that it leads to success on every problem for which success is in principle possible. 相似文献
47.
48.
钛及钛合金电弧钎焊及接头强度 总被引:3,自引:1,他引:3
用Ti—Cu—Ni,Ti-Cr-Zr钎料在TIG电弧加热条件对TA2和Ti—6Al—4V钛合金进行钎焊。结果表明:用Ti—Cu—Ni钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是418.3MPa和439.6MPa;用Ti—Cr—Zr钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是575.2MPa和656.1MPa。对Ti-Cu-Ni钎料/母材界面分析认为固液异分化合物η相((Cu,Ni)Ti2)生成时呈笋状生长,嵌入钎缝对钎缝的强度提高有利。对Ti-Cr-Zr钎料/母材界面分析,认为主要是固溶体β-Ti(Cr)存在提高了钎缝强度。 相似文献
49.
Providing an easy ingress–egress (I/E) movement remains a challenge for car designers. I/E has been largely studied in kinematics, but not in dynamics. This study proposes: (1) to evaluate and describe the motor torques developed in the lower limbs and lumbar joints during I/E motions and (2) to analyse the influence of the car geometry and subject anthropometry. An experiment was performed to observe 15 subjects of three anthropometrical groups getting in and out of a car mock-up simulating three different vehicle configurations. Motor torques were extracted using an inverse dynamics analysis. Both ingress and egress motions were primarily characterised by large torques. Overall, the taller a subject and the lower the seat of the vehicle were, the larger the peak torques were. Moreover, peak torques were higher for egress than ingress. These results are discussed in regard to the current knowledge on I/E ergonomics. 相似文献
50.
观音岩水电站装机容量 3 000 M W, 为一等大( ? ) 型工程。厂房坝段设置 5条横缝, 分为 6 个坝段。通过接缝
灌浆, 极大的改善厂房坝段受力条件, 提高大坝结构整体性和耐久性。结合观音岩水电站现场施工条件, 从施工角
度论述了接缝灌浆的施工工艺以及施工过程中可能存在的问题及处理方法。 相似文献