全文获取类型
收费全文 | 3650篇 |
免费 | 204篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 37篇 |
综合类 | 1篇 |
化学工业 | 746篇 |
金属工艺 | 74篇 |
机械仪表 | 83篇 |
建筑科学 | 163篇 |
矿业工程 | 1篇 |
能源动力 | 113篇 |
轻工业 | 242篇 |
水利工程 | 33篇 |
石油天然气 | 13篇 |
无线电 | 386篇 |
一般工业技术 | 787篇 |
冶金工业 | 431篇 |
原子能技术 | 35篇 |
自动化技术 | 723篇 |
出版年
2023年 | 26篇 |
2022年 | 63篇 |
2021年 | 93篇 |
2020年 | 78篇 |
2019年 | 70篇 |
2018年 | 118篇 |
2017年 | 104篇 |
2016年 | 116篇 |
2015年 | 99篇 |
2014年 | 140篇 |
2013年 | 227篇 |
2012年 | 219篇 |
2011年 | 277篇 |
2010年 | 194篇 |
2009年 | 226篇 |
2008年 | 211篇 |
2007年 | 194篇 |
2006年 | 132篇 |
2005年 | 103篇 |
2004年 | 99篇 |
2003年 | 99篇 |
2002年 | 84篇 |
2001年 | 44篇 |
2000年 | 54篇 |
1999年 | 63篇 |
1998年 | 117篇 |
1997年 | 84篇 |
1996年 | 61篇 |
1995年 | 29篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 30篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1988年 | 23篇 |
1987年 | 15篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1977年 | 13篇 |
1976年 | 22篇 |
1974年 | 13篇 |
1973年 | 14篇 |
1972年 | 7篇 |
排序方式: 共有3868条查询结果,搜索用时 62 毫秒
101.
Product family modeling for mass customization 总被引:64,自引:0,他引:64
Jianxin Jiao Mitchell M. Tseng Vincent G. Duffy Fuhua Lin 《Computers & Industrial Engineering》1998,35(3-4):495-498
With growing reliance on modeling in product development, it is imperative to describe product families in a cohesive way. In particular, mass customization calls for a close integration of product life cycle from customer recognition to delivery and services. This paper proposes a triple-view scheme for modeling product families. Technical challenges are discussed by comparing product family modeling with modeling single products. Individual modeling formalisms for different views are discussed. An example of product family modeling in power supply design is presented to illustrate the feasibility and potential of the proposed approach. 相似文献
102.
103.
Soil water content and dry density are two important properties for compaction quality control. This paper presents a new method for determining soil water content and dry density using a single time domain reflectometry test, which is an improvement over that designated by ASTM D6780. This new method is based on simultaneous measurement of apparent dielectric constant and bulk electrical conductivity on the same soil sample. Calibration equations correlate these two parameters with soil gravimetric water content and dry density, which are simultaneously solved after adjusting field-measured conductivity to a standard conductivity. The method compensates for temperature effects. The test process takes about 3 min and all calculations are automated. Testing may be done in situ using a special probe that provides sufficient sampling volume or in a compaction mold adapted to form a probe. Laboratory and field tests results show this one-step method is a fast, accurate, and safe method for construction quality control. 相似文献
104.
The study concerns the location-routing problem with simultaneous pickup and delivery (LRPSPD) in which the pickup and delivery take place at the same time for each customer. The goal is to determine the facility locations and vehicle routes in order to minimise the total system cost as a sum of facility opening cost, vehicle fixed cost and vehicle travel cost. A simulated annealing (SA) heuristic is proposed for the problem and extensive computational experiments are conducted. The results show that the proposed SA effectively solves LRPSPD and outperforms existing exact approaches in terms of solution quality. 相似文献
105.
Vincent C. Conzola 《Theoretical Issues in Ergonomics Science》2013,14(5):499-500
The goal of this study is to extend Rasmussen's framework for risk management to research organisations having to deal with reduced income from government funding and increased market orientation. One human factors research organisation was studied in detail. Using archival records, changes were studied over the period 1989–2010. The results showed an increase in income from market funding relative to government funding, and a decrease in written output. Predictions by stress–strain theory were confirmed in that during the first 5 years of the period under consideration, a linear relationship between the increase in market funding and written output was observed, whereas a nonlinear relationship was observed in the next 5–10 years, indicating a larger decrease in written output than would be expected. Generally, the results show that research organisations are adaptive systems that trade off resource allocation to either commercial activities or scientific activities, depending on incentive schemes. 相似文献
106.
This study presents the use of original systems based on Candida antarctica lipase B (CALB) immobilized on montmorillonite and sepiolite nanoclays as efficient catalysts for the enzymatic polymerization of ε-caprolactone (ε-CL) and the in situ elaboration of nanohybrids. 相似文献
107.
Carbon nanotubes (CNTs) have unique properties, such as their electrical conductivity, that enable them to be combined with conducting polymers to form composites for use in organic solar cells (OSCs). It is envisaged that the improved composite has a higher efficiency of green energy and will reduce the cost of these cells. The use of such alternative energy sources also drastically reduces overuse of fossil fuels and consequently limits environmental degradation. This review compares research and performance between conventional silicon solar cells and OSCs. It also discusses OSC photoexcitation and charge carrier generation with the incorporation of CNTs, physicochemical properties of the composites and other factors that affect the efficiencies of OSCs. In addition, properties of CNTs that favour their dispersion in polymer matrices as acceptors and charge carriers to the electrodes are covered. The effects of CNTs containing dopants, such as nitrogen and boron, on charge transfer are discussed. Also, the fabrication techniques of OSCs that include CNT/polymer composite processing and the methods of film deposition on the substrate are described. Finally, the case studies of OSCs containing polymers with single‐walled CNTs, double‐walled CNTs or multi‐walled CNTs are evaluated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
108.
Open Learner Models (OLMs) have great potential to support students’ Self-Regulated Learning (SRL) in Intelligent Tutoring Systems (ITSs). Yet few classroom experiments have been conducted to empirically evaluate whether and how an OLM can enhance students’ domain level learning outcomes through the scaffolding of SRL processes in an ITS. In two classroom experiments with a total of 302 7th- and 8th-grade students, we investigated the effect of (a) an OLM that supports students’ self-assessment of their equation-solving skills and (b) shared control over problem selection, on students’ equation-solving abilities, enjoyment of learning with the tutor, self-assessment accuracy, and problem selection decisions. In the first, smaller experiment, the hypothesized main effect of the OLM on students’ learning outcomes was confirmed; we found no main effect of shared control of problem selection, nor an interaction. In the second, larger experiment, the hypothesized main effects were not confirmed, but we found an interaction such that the students who had access to the OLM learned significantly better equation-solving skills than their counterparts when shared control over problem selection was offered in the system. Thus, the two experiments support the notion that an OLM can enhance students’ domain-level learning outcomes through scaffolding of SRL processes, and are among the first in-vivo classroom experiments to do so. They suggest that an OLM is especially effective if it is designed to support multiple SRL processes. 相似文献
109.
In this paper we establish the exact solution for a hollow sphere with a rigid-plastic pressure-sensitive matrix and subjected to hydrostatic tension or compression. The matrix is assumed to obey to a parabolic Mises–Schleicher criterion. The closed-form expressions of the velocity field and of the stress field are provided. These exact solutions, expressed by means of the Lambert W function, allow to assess and discuss existing results. 相似文献
110.
Philippe Szternfeld Svetlana V. Malysheva Vincent Hanot Laure Joly 《Food Analytical Methods》2016,9(5):1173-1179
Glyphosate determination in liver is challenging due to this particular molecule/matrix combination. Glyphosate is a very polar molecule and liver composition is highly variable between individuals and species. Since 2014, the Multiannual Control Program (MACP) of the European Union (EU) demands to analyse glyphosate in food of animal origin on a voluntary basis. Moreover, this analysis will be mandatory in 2017. This paper describes a robust and easily transferable method for glyphosate quantification in liver of animal origin by means of liquid chromatography–tandem mass spectrometry (LC-MS/MS). An intensive clean-up was used to eliminate matrix interferences and was combined with a derivatization step which ensures good retention of glyphosate on a conventional reverse-phase LC column. This method allows to meet the MACP requirements without a time-consuming change in the set-up of the routinely used LC-MS/MS system. Furthermore, it allows the use of an LC column and mobile phases often used in multi-residue analysis. The analytical method was validated according to the SANCO/12571/2013 criteria. Isotopic dilution was used to quantify glyphosate, leading to mean apparent recoveries of 115 and 101 % for the low (0.025 mg kg?1) and the high (0.250 mg kg?1) fortification levels, respectively. At both levels, the relative standard deviation was below 10 %. The limit of quantification of 0.025 mg kg?1 was found to be satisfactory as it was below the maximum residue level (MRL) value set at 0.050 mg kg?1 for glyphosate in liver. It is also the lowest MRL for all commodity types. 相似文献