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   3509篇
  免费   221篇
  国内免费   2篇
电工技术   45篇
综合类   1篇
化学工业   966篇
金属工艺   122篇
机械仪表   91篇
建筑科学   80篇
矿业工程   15篇
能源动力   129篇
轻工业   541篇
水利工程   33篇
石油天然气   8篇
无线电   184篇
一般工业技术   808篇
冶金工业   73篇
原子能技术   46篇
自动化技术   590篇
  2023年   40篇
  2022年   49篇
  2021年   115篇
  2020年   96篇
  2019年   116篇
  2018年   171篇
  2017年   162篇
  2016年   157篇
  2015年   156篇
  2014年   195篇
  2013年   403篇
  2012年   205篇
  2011年   254篇
  2010年   251篇
  2009年   185篇
  2008年   120篇
  2007年   94篇
  2006年   54篇
  2005年   25篇
  2004年   39篇
  2003年   42篇
  2002年   38篇
  2001年   32篇
  2000年   42篇
  1999年   25篇
  1998年   31篇
  1997年   30篇
  1996年   19篇
  1995年   25篇
  1994年   23篇
  1993年   26篇
  1992年   24篇
  1991年   20篇
  1990年   17篇
  1989年   16篇
  1988年   13篇
  1986年   11篇
  1985年   20篇
  1984年   29篇
  1983年   21篇
  1982年   30篇
  1981年   45篇
  1980年   35篇
  1979年   25篇
  1978年   25篇
  1977年   24篇
  1976年   39篇
  1975年   24篇
  1974年   16篇
  1973年   23篇
排序方式: 共有3732条查询结果,搜索用时 0 毫秒
991.
Design is commonly understood as a key element of products, contributing to their distinctiveness, usability and aesthetics. The success of a product is increasingly related to the user experience or the aesthetics of the user interface, meaning that design is increasingly important in the digital environment. The shift in competitive focus to the customer induced by digital design encourages companies to innovate and can also lead to changes in internal operations, market orientation and the reconfiguration of external collaboration procedures. This dimension of digital design-induced effects has to date seen very little research. The objective of this study is to investigate how digital design-induced changes in market orientation, internal restructuring and external cooperation affect firms' competitive orientation. The simultaneous equation framework was applied to a survey of 515 user interface and experience designers from France. Our results suggest that market orientation is not the only channel through which digital design influences firm competitiveness. Digital design leads to organizational change and the reconfiguration of external relationships that directly and indirectly help companies build competitive advantages and increase customer satisfaction.  相似文献   
992.

Cancer therapy for both central nervous system (CNS) and non-CNS tumors has been previously associated with transient and long-term cognitive deterioration, commonly referred to as ‘chemo fog’. This therapy-related damage to otherwise normal-appearing brain tissue is reported using post-mortem neuropathological analysis. Although the literature on monitoring therapy effects on structural magnetic resonance imaging (MRI) is well established, such macroscopic structural changes appear relatively late and irreversible. Early quantitative MRI biomarkers of therapy-induced damage would potentially permit taking these treatment side effects into account, paving the way towards a more personalized treatment planning.

This systematic review (PROSPERO number 224196) provides an overview of quantitative tomographic imaging methods, potentially identifying the adverse side effects of cancer therapy in normal-appearing brain tissue. Seventy studies were obtained from the MEDLINE and Web of Science databases. Studies reporting changes in normal-appearing brain tissue using MRI, PET, or SPECT quantitative biomarkers, related to radio-, chemo-, immuno-, or hormone therapy for any kind of solid, cystic, or liquid tumor were included. The main findings of the reviewed studies were summarized, providing also the risk of bias of each study assessed using a modified QUADAS-2 tool. For each imaging method, this review provides the methodological background, and the benefits and shortcomings of each method from the imaging perspective. Finally, a set of recommendations is proposed to support future research.

  相似文献   
993.
This paper proposes an approach for reducing the computational complexity of a model-predictive-control strategy for discrete-time hybrid systems with discrete inputs only. Existing solutions are based on dynamic programming and multi-parametric programming approaches, while the one proposed in this paper is based on a modified version of performance-driven reachability analyses. The algorithm abstracts the behaviour of the hybrid system by building a ’tree of evolution’. The nodes of the tree represent the reachable states of a process, and the branches correspond to input combinations leading to designated states. A cost-function value is associated with each node and based on this value the exploration of the tree is driven. For any initial state, an input sequence is thus obtained, driving the system optimally over a finite horizon. According to the model predictive strategy, only the first input is actually applied to the system. The number of possible discrete input combinations is finite and the feasible set of the states of the system may be partitioned according to the optimization results. In the proposed approach, the partitioning is performed offline and a probabilistic neural network (PNN) is then trained by the set of points at the borders of the state-space partitions. The trained PNN is used as a system-state-based control-law classifier. Thus, the online computational effort is minimized and the control can be implemented in real time.  相似文献   
994.
995.
Many real-world optimisation problems are of dynamic nature, requiring an optimisation algorithm which is able to continuously track a changing optimum over time. To achieve this, we propose two population-based algorithms for solving dynamic optimisation problems (DOPs) with continuous variables: the self-adaptive differential evolution algorithm (jDE) and the differential ant-stigmergy algorithm (DASA). The performances of the jDE and the DASA are evaluated on the set of well-known benchmark problems provided for the special session on Evolutionary Computation in Dynamic and Uncertain Environments. We analyse the results for five algorithms presented by using the non-parametric statistical test procedure. The two proposed algorithms show a consistently superior performance over other recently proposed methods. The results show that both algorithms are appropriate candidates for DOPs.  相似文献   
996.
The article addresses automatic building extraction from IKONOS images in suburban areas. In the proposed approach, we used a stereo pair of IKONOS images. Automatic photogrammetric methods of image matching were used to generate a digital surface model (DSM) and a digital elevation model. In further processing, single-image methods were used. The orthophotos of individual bands were created. The initial building mask was generated from the calculated normalized DSM (nDSM). The calculated normalized difference vegetation index and the road data extracted from the existing topographical database were used to remove vegetation and traffic surfaces. The mask was further improved with our own combination of methods based on non-linear diffusion filtering, unsupervised classification, colour segmentation and region growing. The final mask was vectorized using the Hough transform. Compared with a reference building database, 83.2% of the buildings in the test area were detected using the proposed approach with a quality percentage (how likely a building pixel produced by an automatic approach is correct) of 49.46.  相似文献   
997.
In the present paper, we introduce a proper superclass of homogeneous effect algebras. We call this superclass as 0-homogeneous effect algebras. We prove that in every 0-homogeneous effect algebra, the set of all sharp elements forms a subalgebra. Every chain-complete 0-homogeneous effect algebra is homogeneous.  相似文献   
998.
The stability of Fe-Ni-base metallic glasses on annealing in the range 30 to 1000° C was investigated by microhardness measurements. The results (i.e. two maxima in all recorded curves, for annealing temperatures below and above 400° C) were correlated with other recent experimental evidence for structural relaxation and structural changes in the same metallic glasses.  相似文献   
999.
1000.
Summary Polymerization of 9-(2,3-epoxypropyl) carbazole (EPC) and 1,2-epoxy-6-(9-carbazolyl)-4-oxahexane (ECOH) with triphenylcarbenium hexachloroantimonate and triphenylcarbenium tetrafluoroborate have been studied by the microcalorimetric technique. Triphenylcarbenium salts have turn out to be more efficient catalyst for the polymerization of carbazolyl-containing epoxides than Lewis acids, giving high yields at low initial concentration of the catalyst. Using comparatively restricted conditions of reaction ([triphenylcarbenium saltyda]o0.02 mol/l t50° C) transition from the conventional active chain end mechanism to the activated monomer mechanism has been observed at a sufficiently high degree of conversion of monomer.  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