全文获取类型
收费全文 | 985篇 |
免费 | 69篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 271篇 |
金属工艺 | 5篇 |
机械仪表 | 12篇 |
建筑科学 | 31篇 |
矿业工程 | 1篇 |
能源动力 | 40篇 |
轻工业 | 164篇 |
水利工程 | 8篇 |
无线电 | 55篇 |
一般工业技术 | 141篇 |
冶金工业 | 166篇 |
原子能技术 | 11篇 |
自动化技术 | 134篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 65篇 |
2021年 | 46篇 |
2020年 | 29篇 |
2019年 | 19篇 |
2018年 | 29篇 |
2017年 | 32篇 |
2016年 | 30篇 |
2015年 | 29篇 |
2014年 | 54篇 |
2013年 | 62篇 |
2012年 | 45篇 |
2011年 | 56篇 |
2010年 | 42篇 |
2009年 | 44篇 |
2008年 | 37篇 |
2007年 | 36篇 |
2006年 | 20篇 |
2005年 | 28篇 |
2004年 | 26篇 |
2003年 | 18篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 17篇 |
1998年 | 44篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 2篇 |
1966年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有1054条查询结果,搜索用时 0 毫秒
11.
Potentially life threatening rythm disturbances, such as third degree A-V block and sinus arrest without "escape rythm", represent infrequent and unexpected events during dipyridamole thallium scintigraphy. We report three cases of cardiac arrest requiring resuscitation maneuvers after dipyridamole infusion during myocardial thallium scan. On the basis of these clinical observations we suggest that a trained cardiologist and resuscitation kit should be available in nuclear lab. Moreover elderly patients may require careful screening for preexisting conduction defects and sick sinus syndrome. When dipyridamole infusion provokes severe bradyarrhythmias not related to myocardial ischemia, a transesophageal electrophysiological study should always be performed. 相似文献
12.
Raffaele Calabretta Riccardo Galbiati Stefano Nolfi Domenico Parisi 《Neural Processing Letters》1996,4(3):149-155
In nature the genotype of many organisms exhibits diploidy, i.e., it includes two copies of every gene. In this paper we describe the results of simulations comparing the behavior of haploid and diploid populations of ecological neural networks living in both fixed and changing environments. We show that diploid genotypes create more variability in fitness in the population than haploid genotypes and buffer better environmental change; as a consequence, if one wants to obtain good results for both average and peak fitness in a single population one should choose a diploid population with an appropriate mutation rate. Some results of our simulations parallel biological findings. 相似文献
13.
Given a graph G where a label is associated with each edge, we address the problem of looking for a maximum matching of G using the minimum number of different labels, namely the labeled maximum matching problem. It is a relatively new problem whose application is related to the timetabling problem. We prove it is NP-complete and present four different mathematical formulations. Moreover, we propose an exact algorithm based on a branch-and-bound approach to solve it. We evaluate the performance of our algorithm on a wide set of instances and compare our computational times with the ones required by CPLEX to solve the proposed mathematical formulations. Test results show the effectiveness of our procedure, that hugely outperforms the solver. 相似文献
14.
韩丽 《小型微型计算机系统》2009,30(7)
随着基于样条曲线的模型逐渐成为CAGD的主要研究对象,进一步带动了高度自由曲面建模技术的发展.本文描述一个新颖、直观的旋转曲面绘制技术,它支持三次B样条的自由输入作为轮廓线,并通过提取的样点矢量以及最小方差逼近方法形成旋转轴,利用轴上测量点的切线方向确定各个圆平面,从而建立了平面上旋转坐标矩阵,最终插值空间球面样点生成双三次B样条曲面.实验结果有效地验证了此技术的高效性. 相似文献
15.
Huang CP Liu YT Nakatsuji T Shi Y Gallo RR Lin SB Huang CM 《Proteomics. Clinical applications》2008,2(9):1234-1245
Proteomics is a powerful tool for the identification of proteins, which provides a basis for rational vaccine design. However, it is still a highly technical and time‐consuming task to examine a protein's immunogenicity utilizing traditional approaches. Here, we present a platform for effectively evaluating protein immunogenicity and antibody detection. A tetanus toxin C fragment (Tet‐c) was used as a representative antigen to establish this platform. A cell wall‐anchoring sialidase‐like protein (SLP) of Propionibacterium acnes was utilized to assess the efficacy of this platform. We constructed an Escherichia coli vector‐based vaccine by overexpressing Tet‐c or SLP in E. coli and utilized an intact particle of E. coli itself as a vaccine (E. coli Tet‐c or SLP vector). After ultraviolet (UV) irradiation, the E. coli vector‐based vaccines were administered intranasally into imprinting control region mice without adding exogenous adjuvants. For antibody detection, we fabricated antigen microarrays by printing with purified recombinant proteins including Tet‐c and SLP. Our results demonstrated that detectable antibodies were elicited in mice 6 weeks after intranasal administration of UV‐irradiated E. coli vector‐based vaccines. The antibody production of Tet‐c and SLP was significantly elevated after boosting. Notably, the platform with main benefits of using E. coli itself as a vaccine carrier provides a critical template for applied proteomics aimed at screening novel vaccine targets. In addition, the novel immunogenic SLP potentially serves as an antigen candidate for the development of vaccines targeting P. acnes‐associated diseases. 相似文献
16.
Placidi G Franchi D Marsili L Gallo P 《Computer methods and programs in biomedicine》2007,88(2):144-151
Vascular catheterization is a common procedure in clinical medicine. It is normally performed by a specialist using an X-ray fluoroscopic guide and contrast-media. In the present paper, an image-guided navigation system which indicates a path providing guidance to the desired target inside the vascular tree is described with the aim of reducing the exposure of personnel and patients to X-rays during the catheterization procedure. A 3D model of the patient vascular tree, reconstructed with data collected by an angiography before starting the intervention, is used as a guide map instead of fluoroscopic scans. An accurate spatial correspondence between the body of the patient and the 3D reconstructed vascular model is established and, by means of a position indicator installed over the catheter tip, the real-time position/orientation of the tip is indicated correctly. This paper describes the system and the operational procedures necessary to use the proposed method efficiently during a catheter intervention. Preliminary experimental results on a phantom are also reported. 相似文献
17.
Paolo Carraresi Giorgio Gallo Gabriella Rago 《Annals of Mathematics and Artificial Intelligence》1993,8(3-4):247-270
In a previous paper, a hypergraph model for the satisfiability of Datalog formulas was proposed. Here, we extend that approach in order to deal with a class ofconstraint logic programming (CLP) formulas, that is, Datalog formulas in the presence of constraints. A CLP formula is represented by means of a weighted hypergraph and the problem of evaluating this formula is reduced to a sequence of shortest path computations on hypergraphs. To evaluate the performance of this approach, the bus drivers' scheduling problem is formulated as the problem of checking the satisfiability of a CLP formula and it is solved by means of the hypergraph-based algorithm embedded within a local search procedure. Preliminary experimental results are quite encouraging and suggest that the proposed approach may provide an efficient way to tackle hard real-life combinatorial problems.This research was partially supported by the Progetto Finalizzato Trasporti 2 of the Italian National Research Council, under Contract No. 91.02479.PF74. 相似文献
18.
Gabriele Dono Raffaele Cortignani Luca Doro Luca Giraldo Luigi Ledda Massimiliano Pasqui Pier Paolo Roggero 《Water Resources Management》2013,27(10):3607-3622
Climate change is likely to have a profound effect on many agricultural variables, although the extent of its influence will vary over the course of the annual farm management cycle. Consequently, the effect of different and interconnected physical, technical and economic factors must be modeled in order to estimate the effects of climate change on agricultural productivity. Such modeling commonly makes use of indicators that summarize the among environmental factors that are considered when farmers plan their activities. This study uses net evapotranspiration (ETN), estimated using EPIC, as a proxy index for the physical factors considered by farmers when managing irrigation. Recent trends suggest that the probability distribution function of ETN may continue to change in the near future due to changes in the irrigation needs of crops. Also, water availability may continue to vary due to changes in the rainfall regime. The impacts of the uncertainties related to these changes on costs are evaluated using a Discrete Stochastic Programming model representing an irrigable Mediterranean area where limited water is supplied from a reservoir. In this context, adaptation to climate change can be best supported by improvements to the collective irrigation systems, rather than by measures aimed at individual farms such as those contained within the rural development policy. 相似文献
19.
Gallo Linda C.; Bogart Laura M.; Vranceanu Ana-Maria; Matthews Karen A. 《Canadian Metallurgical Quarterly》2005,88(2):386
The current study used ecological momentary assessment to test several tenets of the reserve capacity model (L.C. Gallo & K. A. Matthews, 2003). Women (N = 108) with varying socioeconomic status (SES) monitored positive and negative psychosocial experiences and emotions across 2 days. Measures of intrapsychic and social resources were aggregated to represent the reserve capacity available to manage stress. Lower SES was associated with less perceived control and positive affect and more social strain. Control and strain contributed to the association between SES and positive affect. Lower SES elicited greater positive but not negative emotional reactivity to psychosocial experiences. Women with low SES had fewer resources relative to those with higher SES, and resources contributed to the association between SES and daily experiences. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
20.
Giovanni Garcea Giampaolo Armentano Salvatore Petrolo Raffaele Casciaro 《International journal for numerical methods in engineering》2005,63(8):1174-1202
In the present paper, the formulation proposed by Casciaro and Garcea (Comput. Meth. Appl. Mech. Eng., 2002; 191 :5761–5792) and applied to the shakedown analysis of plane frames, is extended to the analysis of two‐dimensional flat structures in both the cases of plane‐stress and plane‐strain. The discrete formulation is obtained using a mixed finite element in which both stress and displacement fields are interpolated. The material is assumed to be elasto‐plastic and a linearization of the elastic domain is performed. The result is a versatile iterative scheme well suited to implementation in general purpose FEM codes. An extensive series of numerical tests is presented showing the reliability of the proposed formulation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献