全文获取类型
收费全文 | 4611篇 |
免费 | 235篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 56篇 |
综合类 | 3篇 |
化学工业 | 979篇 |
金属工艺 | 96篇 |
机械仪表 | 74篇 |
建筑科学 | 273篇 |
矿业工程 | 4篇 |
能源动力 | 203篇 |
轻工业 | 473篇 |
水利工程 | 30篇 |
石油天然气 | 9篇 |
无线电 | 392篇 |
一般工业技术 | 864篇 |
冶金工业 | 461篇 |
原子能技术 | 36篇 |
自动化技术 | 903篇 |
出版年
2023年 | 46篇 |
2022年 | 71篇 |
2021年 | 126篇 |
2020年 | 84篇 |
2019年 | 101篇 |
2018年 | 111篇 |
2017年 | 106篇 |
2016年 | 142篇 |
2015年 | 128篇 |
2014年 | 160篇 |
2013年 | 289篇 |
2012年 | 290篇 |
2011年 | 350篇 |
2010年 | 299篇 |
2009年 | 273篇 |
2008年 | 283篇 |
2007年 | 240篇 |
2006年 | 209篇 |
2005年 | 180篇 |
2004年 | 158篇 |
2003年 | 140篇 |
2002年 | 128篇 |
2001年 | 65篇 |
2000年 | 75篇 |
1999年 | 57篇 |
1998年 | 80篇 |
1997年 | 66篇 |
1996年 | 61篇 |
1995年 | 48篇 |
1994年 | 53篇 |
1993年 | 37篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 30篇 |
1988年 | 21篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 19篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1974年 | 7篇 |
1971年 | 6篇 |
排序方式: 共有4856条查询结果,搜索用时 22 毫秒
131.
French Douglas J.; No?l Marc; Vigneau Fran?ois; French Julie A.; Cyr Chantal P.; Evans R. Thomas 《Canadian Metallurgical Quarterly》2005,37(3):181
This study examined the psychometric properties of the PCS-CF, a French-Canadian adaptation of the Pain Catastrophizing Scale (Sullivan, Bishop & Pivik, 1995). One hundred and twenty undergraduate students (83 women; 37 men) completed the PCS-CF and measures of anxiety and depression prior to immersing their hand in ice water for 1-minute. A subset of 39 participants (28 females; 11 males) also completed a second pain task involving an ascending series of electrocutaneous stimulations. Participants' verbal and non-verbal pain behaviours during and immediately after the immersion task were recorded and subsequently independently coded. Reliability analyses revealed that the PCS-CF total score and subscale scores have a high degree of internal consistency and test-retest reliabilities that are comparable to the original Pain Catastrophizing Scale. PCS-CF scores were associated with higher levels of self-reported pain during the ice water immersion task and decreased pain tolerance during electrocutaneous stimulation. Individuals with elevated PCS-CF scores also displayed a more diverse repertoire of pain behaviours than their low PCS-CF counterparts. Previous findings that catastrophizing scores are able to discriminate criterion groups of males and females were also replicated. Given the highly correlated factors obtained in analyses of the dimensionality of the PCS-CF, the structure suggested by the authors of the original scale is only partially supported. However, the results taken together suggest that the PCS-CF is both a reliable and valid measure of the pain catastrophizing construct that is psychometrically comparable to the original PCS. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
132.
由于用传统的刚体匹配方法难以解决待匹配图象之间的结构差异 ,因此需要引入变形模型来进行图象的非刚体匹配 .为此提出了一种利用混合弹性模型 (HEM)来解决图象变形匹配问题的新方法 .该方法不需要预先提取图象的特征 ,而是直接利用匹配图象之间的灰度信息来实现图象之间的匹配 .匹配时 ,首先通过基于主轴的方法来实现两幅图象之间的全局仿射匹配 ;然后利用线性弹簧网模型来求取两幅图象之间的相关性 ,并进一步利用薄板样条模型来实现两幅图象的变形匹配 .该方法在匹配过程中还采取了多分辨率匹配策略 ,合成图象和医学脑图象的实验结果表明 ,该方法是有效的 相似文献
133.
Marc L. Imhoff Thomas D. Sisk Anthony Milne Garth Morgan Tony Orr 《Remote sensing of environment》1997,60(3):217-227
An integrated remote sensing/field ecology project linked the use of synthetic aperture radar (SAR) and aerial photography to studies of landscape spatial heterogeneity and bird community ecology. P-, L-, and C-band SAR data, collected over a section of Kakadu National Park in Australia's Northern Territory during the Joint NASA/Australia DC-8 data acquisition campaign, were analyzed in light of field data integrating vegetation structure and floristics with bird abundances across a heterogeneous study site. Results indicate that SAR data are able to discern structural differences relevant to bird habitat quality within floristically homogeneous stands, while multispectral sensors successfully identified floristic differences among habitat types. Simplifying indices of bird diversity showed ambiguous changes across the site; however, the abundances of individual species were observed to change significantly across both floristic and structural gradients. These results suggest that efforts to map bird diversity should focus on species-specific habitat relationships and that some measure of vegetation structure is needed to understand bird habitat. The approach employed here advances the use of SAR data in the three-dimensional mapping of animal habitats from remotely sensed data, and extends current capabilities for mapping and modeling large-scale patterns in the distribution of biological diversity. 相似文献
134.
135.
Marc Bescond Jean-Luc Autran Nicolas Cavassilas Daniela Munteanu Michel Lannoo 《Journal of Computational Electronics》2004,3(3-4):393-396
A program to numerically simulate point defects in nanowire metal-oxide-semiconductor field-effect transistors is described. The simulation scheme is based on the non-equilibrium Green’s function method self-consistently being obtained via the resolution of 3D Poisson’s equation. A tight-binding hamiltonian is used and the point defect is characterized by a macroscopic coulombic tail treated in the mode-space approach, plus a short range on-site perturbation potential energy, treated exactly. The effect on internal quantities and on the transistor characteristics is studied as a function of the strength and the location of the defect potential. Subthreshold current is found to vary in a factor 10 according to the position of the impurity.Also With Institut Universitaire De France (IUF). 相似文献
136.
137.
The graph partitioning problem consists of dividing the vertices of a graph into clusters, such that the weight of the edges crossing between clusters is minimized. We present a new compact mathematical formulation of this problem, based on the use of binary representation for the index of clusters assigned to vertices. This new formulation is almost minimal in terms of the number of variables and constraints and of the density of the constraint matrix. Its linear relaxation brings a very fast computational resolution, compared with the standard one.Experiments were conducted on classical large benchmark graphs designed for comparing heuristic methods. On one hand, these experiments show that the new formulation is surprisingly less time efficient than expected on general k-partitioning problems. On the other hand, the new formulation applied on bisection problems allows to obtain the optimum solution for about ten instances, where only best upper bounds were previously known. 相似文献
138.
David Gabriel Huub H. J. Cox Marc A. Deshusses 《Canadian Metallurgical Quarterly》2004,130(10):1110-1117
Until recently, biological treatment of odors in biofilters or biotrickling filters was thought to require a longer gas contact time than chemical scrubbing, hence bioreactors for air treatment required a larger footprint. This paper discusses the conversion of chemical scrubbers to biological trickling filters. Initially, research was conducted with a laboratory-scale biotrickling filter. An effective open-pore polyurethane packing material was identified and H2S biotreatment performance was quantified. Key technical issues in determining the general suitability of converting wet scrubbers to biotrickling filters were identified, and a generic ten-step conversion procedure was developed. Following the laboratory research, five full-scale chemical scrubbers treating odorous air at the Sanitation District of Orange County, Calif., were converted to biotrickling filters. The original airflow rate was maintained, resulting in a gas contact time as low as 1.6–3.1?s. The converted biotrickling filters demonstrated an excellent capability for treating high H2S concentrations to concentrations below regulatory limits. This study shows outstanding potential for converting chemical scrubbers to biotrickling filters at publicly owned treatment works. 相似文献
139.
Marc Rennhard Sandro Rafaeli Laurent Mathy Bernhard Plattner David Hutchison 《Electronic Commerce Research》2004,4(1-2):83-111
The lack of privacy is one of the main reasons that limits trust in e-commerce. Current e-commerce practice enforces a customer to disclose her identity to the e-shop and the use of credit cards makes it straightforward for an e-shop to know the real identity of its customers. Although there are some payment systems based on untraceable tokens, they are not as widely used as credit cards. Furthermore, even without buying anything, a customer is already disclosing some information about who or where she may be by just connecting to the e-shop's web server and leaving behind an IP-address. In this paper, we present novel components that enable secure pseudonymous e-commerce. On the one hand, these components allow a customer to browse through an e-shop, select goods, and pay the goods with her credit card such that neither the e-shop operator nor the credit card issuer nor an eavesdropper is able to get any information about the customer's identity. On the other hand, it is guaranteed that none of the involved parties is able to act dishonestly during the credit card payment. Such a system could greatly enhance trust in e-commerce since it overcomes the customers' privacy concerns. 相似文献
140.
This paper represents a first attempt at a systematic study of sensitivity analysis for scheduling problems. Because schedules contain both combinatorial and temporal structures, scheduling problems present unique issues for sensitivity analysis. Some of the issues that we discuss have not been considered before. Others, while studied before, have not been explored in the context of scheduling. The applicability of these issues is illustrated using well-known scheduling models. We provide fast methods to determine when a previously optimal schedule remains optimal. Other methods restore an optimal schedule after a parameter change. The value of studying the sensitivity of an optimal sequence instead of the sensitivity of an optimal schedule is demonstrated. We show that, for some problems, sensitivity analysis results depend on the positions of jobs with changed parameters. We identify scheduling problems where performing additional or different computations during optimization facilitates sensitivity analysis. To improve the robustness of an optimal schedule, selection among multiple optimal schedules is considered. We discuss which types of sensitivity analysis questions are intractable because the scheduling problem itself is intractable. We also study how heuristic error bounds vary when the data of a scheduling problem is continuously modified. Although we focus on scheduling problems, several of the issues we discuss and our classification scheme can be extended to other optimization problems. 相似文献