首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1493篇
  免费   96篇
  国内免费   1篇
电工技术   13篇
化学工业   457篇
金属工艺   31篇
机械仪表   54篇
建筑科学   40篇
矿业工程   3篇
能源动力   78篇
轻工业   260篇
水利工程   19篇
石油天然气   17篇
无线电   71篇
一般工业技术   223篇
冶金工业   55篇
原子能技术   10篇
自动化技术   259篇
  2024年   14篇
  2023年   21篇
  2022年   39篇
  2021年   85篇
  2020年   64篇
  2019年   76篇
  2018年   71篇
  2017年   61篇
  2016年   75篇
  2015年   47篇
  2014年   70篇
  2013年   133篇
  2012年   87篇
  2011年   105篇
  2010年   103篇
  2009年   109篇
  2008年   58篇
  2007年   63篇
  2006年   39篇
  2005年   24篇
  2004年   28篇
  2003年   26篇
  2002年   22篇
  2001年   12篇
  2000年   15篇
  1999年   12篇
  1998年   17篇
  1997年   18篇
  1996年   10篇
  1995年   8篇
  1994年   11篇
  1993年   9篇
  1992年   8篇
  1990年   5篇
  1989年   3篇
  1988年   2篇
  1987年   4篇
  1985年   2篇
  1984年   7篇
  1983年   3篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1976年   4篇
  1967年   2篇
  1961年   1篇
  1940年   1篇
  1930年   1篇
  1925年   2篇
  1921年   1篇
排序方式: 共有1590条查询结果,搜索用时 0 毫秒
1.
In this work it is presented a study on the residence time distribution (RTD) of particles in a co-current pilot-plant spray dryer operated with a rotary atomization system. A nuclear technique is applied to investigate the RTD responses of spray dryers. The methodology is based on the injection of a radioisotope tracer in the feed stream followed by the monitoring of its concentration at the outlet stream. The experiments were performed during the drying of aqueous suspensions of gadolinium oxide. The RTD responses obtained experimentally presented good reproducibility, indicating that the technique applied is well suited to investigating fluid-dynamics of spray dryers. In addition to the experimental investigation, a mathematical model was used to describe the RTD experimental curves.  相似文献   
2.
We compute the temperature dependent magnetic susceptibility of the single-impurity, two-channel Anderson model with an alternative multi-step numerical renormalization-group transformation, previously applied only to the two-impurity single-channel Kondo model. Compared with the traditional transformation, the new procedure requires substantially less memory and computational time, and opens therefore perspectives for the application of the numerical renormalization-group procedure to more complex Hamiltonians.  相似文献   
3.
Subalpine fir (Abies lasiocarpa Hook) lumber containing wetpockets (wetwood) was used for the measurements of gas permeability and the results were then compared to the gas permeability of normal wood, which was free of the wetpockets. The impacts of pretreatment methods were also investigated, including steaming at green condition, steaming at fiber saturation point (FSP), microwave treatment, and radio-frequency treatment. Results from this study demonstrated that both the transverse and the longitudinal gas permeability of subalpine fir wetwood are greater than that of normal wood. There is no significant change in the permeability after 4-h steaming pretreatment at green condition and at FSP. The impacts of microwave and radio-frequency pretreatments were not significant, but the findings cannot be generalized because they may depend on the power intensity applied.  相似文献   
4.
Hormone-refractory prostate cancer (HRPC) patients often have nonmeasurable disease. In such patients, predictive biomarkers other than tumor response may be required to compare therapeutic effects. We examined the predictive value for survival of various clinical and laboratory parameters, including prostate-specific antigen (PSA), in HRPC patients treated with suramin. Data from 103 HRPC patients were analyzed using various survival analyses, the likelihood ratio approach, and logistic regression analyses. When pretreatment factors, percentage decrease in PSA at 4 weeks from start of treatment (deltaPSA), and updated survival data were fit by a multivariate Cox proportional hazards model, acid phosphatase, lactate dehydrogenase, and deltaPSA were significant, with risk ratios close to 1. There was a decrease in likelihood ratio with increasing APSA. A logistic regression model was developed to predict the probability of <1 year of survival from the start of treatment. Hemoglobin and deltaPSA were found to be significant variables. However, in view of the complexities involving the relationship between PSA expression and prostate cancer growth and possible selective effect of treatment on PSA, further prospective testing is necessary. Therefore, deltaPSA cannot necessarily be used as a biomarker for survival response in individual patients during the evaluation of the therapeutic response of HRPC to new antineoplastic drugs.  相似文献   
5.

Contracts play an important role in business management where relationships among different parties are dictated by legal rules. Electronic contracts have emerged mostly due to technological advances and electronic trading between companies and customers. New challenges have then arisen to guarantee reliability among the stakeholders in electronic negotiations. In this scenario, automatic verification of electronic contracts appeared as an imperative support, specially the conflict detection task of multi-party contracts. The problem of checking contracts has been largely addressed in the literature, but there are few, if any, methods and practical tools that can deal with multi-party contracts using a contract language with deontic and dynamic aspects as well as relativizations, over the same formalism. In this work we present an automatic checker for finding conflicts on multi-party contracts modeled by an extended contract language with deontic operators and relativizations. Moreover a well-known case study of sales contract is modeled and automatically verified by our tool. Further, we performed practical experiments in order to evaluate the efficiency of our method and the practical tool.

  相似文献   
6.
Pattern Analysis and Applications - Digital holography is an imaging process able to recreate three-dimensional representations of objects from recording pattern interference among distinct waves....  相似文献   
7.
8.
This paper discusses the problem of modeling on triangulated surfaces with geodesic curves. In the first part of the paper we define a new class of curves, called geodesic Bézier curves, that are suitable for modeling on manifold triangulations. As a natural generalization of Bézier curves, the new curves are as smooth as possible. In the second part we discuss the construction of C 0 and C 1 piecewise Bézier splines. We also describe how to perform editing operations, such as trimming, using these curves. Special care is taken to achieve interactive rates for modeling tasks. The third part is devoted to the definition and study of convex sets on triangulated surfaces. We derive the convex hull property of geodesic Bézier curves.
Luiz VelhoEmail:
  相似文献   
9.
This paper presents two new mathematical formulations for the point-feature cartographic label placement problem (PFCLP) and a new Lagrangean relaxation with clusters (LagClus) to provide bounds to these formulations. The PFCLP can be represented by a conflict graph and the relaxation divides the graph in small subproblems (clusters) that are easily solved. The edges connecting clusters are relaxed in a Lagrangean way and a subgradient algorithm improves the bounds. The LagClus was successfully applied to a set of instances up to 1000 points providing the best results of those reported in the literature.  相似文献   
10.
A new simple method (“line patterning technique”) using only standard office equipment is described whereby clearly defined, electrically conducting patterns of graphite can be deposited on polymer (plastic) or paper substrates. The properties of the conductive patterns have been characterized by electrical conductivity and SEM measurements. Sensors were constructed by using interdigitated patterns of graphite deposited on plastic and paper, and coated with a thin film of conducting electronic polymer, e.g. polyaniline emeraldine salt.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号