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   1238篇
  免费   71篇
  国内免费   2篇
电工技术   9篇
综合类   1篇
化学工业   286篇
金属工艺   32篇
机械仪表   18篇
建筑科学   60篇
矿业工程   2篇
能源动力   41篇
轻工业   75篇
水利工程   4篇
石油天然气   1篇
无线电   63篇
一般工业技术   291篇
冶金工业   221篇
原子能技术   5篇
自动化技术   202篇
  2024年   5篇
  2023年   34篇
  2022年   41篇
  2021年   58篇
  2020年   42篇
  2019年   46篇
  2018年   53篇
  2017年   49篇
  2016年   39篇
  2015年   33篇
  2014年   38篇
  2013年   84篇
  2012年   65篇
  2011年   57篇
  2010年   52篇
  2009年   57篇
  2008年   60篇
  2007年   39篇
  2006年   41篇
  2005年   24篇
  2004年   24篇
  2003年   23篇
  2002年   21篇
  2001年   12篇
  2000年   16篇
  1999年   8篇
  1998年   54篇
  1997年   32篇
  1996年   34篇
  1995年   14篇
  1994年   10篇
  1993年   16篇
  1992年   17篇
  1991年   5篇
  1990年   6篇
  1989年   7篇
  1988年   6篇
  1987年   5篇
  1985年   4篇
  1984年   5篇
  1983年   4篇
  1982年   5篇
  1981年   6篇
  1979年   6篇
  1978年   5篇
  1976年   12篇
  1969年   3篇
  1957年   3篇
  1954年   3篇
  1943年   4篇
排序方式: 共有1311条查询结果,搜索用时 15 毫秒
921.
The literature on management control has expanded considerably in the past few decades, yet only a limited number of publications have been devoted to multi-project organizations (MPOs). This is somewhat a problem given the increasing rise and importance of project-based structures and the role of project management as a significant part of many firms' management control system. This paper elaborates on a contingency framework of management control in MPOs and aims at investigating the control issues that call for holistic frameworks of control mechanisms. Relying on a comparative case study, the analysis shows how control mechanisms are deployed and what implications different choices of management control systems have on the organizational structure of MPOs. In particular, the paper addresses the importance technical complementarities, and the role of ‘project interdependencies’ and ‘project openness’ for the design of management control system.  相似文献   
922.
In Germany, over 7000 professional athletes from different sport sectors must undergo regular doping controls. As is the case with many other nations, Germany relies upon a system recommended by the World Anti-Doping Agency (WADA) to coordinate and initiate these controls. Known as the Anti-Doping Admission and Administration System, or ADAMS for short, the system requires athletes to submit their future regular whereabouts via browser, up to three months in advance. This allows the Doping Control Officer (DCO) to be able to locate the athlete without prior notice. The flip side, however, is that, since its introduction in 2007, ADAMS has not only been severely criticized by athletes themselves for its lack of usability, but has also come under attack by data-privacy experts accusing this system of breaching multiple data privacy laws.  相似文献   
923.
Stretchable conductors based on eutectic gallium–indium (eGaIn) alloy are patterned on a polychloroprene substrate (neoprene foam) using stencil printing. By tuning the amount of eGaIn on the neoprene substrate, different strain‐sensitivity of electrical resistance is achieved. Conductors with a layer of eGaIn, which adsorbs to the walls of 60–100 µm wide neoprene cells, change their electrical resistance for 5% at 100% strain. When the amount of eGaIn is increased, the cells are filled with eGaIn and the strain‐sensitivity of the electrical resistance rises to 300% at 100% strain. The developed conductors are patterned as stretchable on‐body coils for receiving magnetic signals in a clinical magnetic resonance imaging setup. First images with a stretchable coil are acquired on an orange and compared to the images that are recorded using a rigid copper coil of the same size.  相似文献   
924.
This study describes rock reinforcement through the use of reinforced shotcrete in structural interaction with rock bolts. The intention of the investigation was to increase the knowledge of steel-fibre-reinforced shotcrete and the way in which bolt anchorage in shotcrete is designed. The researcher performed 22 large-scale laboratory tests on bolt-anchored, reinforced shotcrete lays, 19 of which were reinforced with Bekaert steel fibres, 2 with cold-tensioned reinforcement mesh, and 1 with an annealed mesh. Fibre content, fibre length and anchorage of the bolt in the shotcrete varied in the tests. For each large-scale test, adhesion tests on the rock-shotcrete interface were performed, as well as strength on sawn-out shotcrete cubes and beams both with and without fibres. The concrete mass was tested using cast cubes. Four large-scale tests on extremely thin fibre-reinforced linings without bolt anchorage also were performed. Two specimens contained steel fibres, and two contained glass fibres. Details also are provided of shear tests on split steel-fibre-reinforced test specimens on a small scale. The paper concludes with a discussion of the test results.  相似文献   
925.
Protocadherins (PCDHs) belong to the cadherin superfamily and represent the largest subgroup of calcium-dependent adhesion molecules. In the genome, most PCDHs are arranged in three clusters, α, β, and γ on chromosome 5q31. PCDHs are highly expressed in the central nervous system (CNS). Several PCDHs have tumor suppressor functions, but their individual role in primary brain tumors has not yet been elucidated. Here, we examined the mRNA expression of PCDHGC3, a member of the PCDHγ cluster, in non-cancerous brain tissue and in gliomas of different World Health Organization (WHO) grades and correlated it with the clinical data of the patients. We generated a PCDHGC3 knockout U343 cell line and examined its growth rate and migration in a wound healing assay. We showed that PCDHGC3 mRNA and protein were significantly overexpressed in glioma tissue compared to a non-cancerous brain specimen. This could be confirmed in glioma cell lines. High PCDHGC3 mRNA expression correlated with longer progression-free survival (PFS) in glioma patients. PCDHGC3 knockout in U343 resulted in a slower growth rate but a significantly faster migration rate in the wound healing assay and decreased the expression of several genes involved in WNT signaling. PCDHGC3 expression should therefore be further investigated as a PFS-marker in gliomas. However, more studies are needed to elucidate the molecular mechanisms underlying the PCDHGC3 effects.  相似文献   
926.
Temporal correctness is crucial for real-time systems. Few methods exist to test temporal correctness and most methods used in practice are ad-hoc. A problem with testing real-time applications is the response-time dependency on the execution order of concurrent tasks. Execution order in turn depends on execution environment properties such as scheduling protocols, use of mutual exclusive resources as well as the point in time when stimuli is injected. Model based mutation testing has previously been proposed to determine the execution orders that need to be verified to increase confidence in timeliness. An effective way to automatically generate such test cases for dynamic real-time systems is still needed. This paper presents a method using heuristic-driven simulation to generate test cases.  相似文献   
927.
Terror management theory suggests that people cope with awareness of death by investing in some kind of literal or symbolic immortality. Given the centrality of death transcendence beliefs in most religions, the authors hypothesized that religious beliefs play a protective role in managing terror of death. The authors report three studies suggesting that affirming intrinsic religiousness reduces both death-thought accessibility following mortality salience and the use of terror management defenses with regard to a secular belief system. Study 1 showed that after a naturally occurring reminder of mortality, people who scored high on intrinsic religiousness did not react with worldview defense, whereas people low on intrinsic religiousness did. Study 2 specified that intrinsic religious belief mitigated worldview defense only if participants had the opportunity to affirm their religious beliefs. Study 3 illustrated that affirmation of religious belief decreased death-thought accessibility following mortality salience only for those participants who scored high on the intrinsic religiousness scale. Taken as a whole, these results suggest that only those people who are intrinsically vested in their religion derive terror management benefits from religious beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
928.
Prediction of steel flow stresses at high temperatures and strain rates   总被引:9,自引:0,他引:9  
The flow behavior of steels during deformation in the roll gap was simulated by means of single hit compression tests performed in the temperature range 800 °C to 1200 °C. Strain rates of 0.2 to 50 s−1 were employed on selected low-carbon steels containing various combinations of niobium, boron, and copper. The stress/strain curves determined at the higher strain rates were corrected for deformation heating so that constitutive equations pertaining to idealized isothermal conditions could be formulated. When dynamic recovery is the only softening mechanism, these involve a rate equation, consisting of a hyperbolic sine law, and an evolution equation with one internal variable, the latter being the dislocation density. When dynamic recrystallization takes place, the incorporation of the fractional softening by dynamic recrystallization in the evolution equation makes it possible to predict the flow stress after the peak. These expressions can be employed in computer models for on-line gage control during hot-rolling.  相似文献   
929.
The orientation relationships associated with different mechanisms of new grain formation during the hot deformation of a Mg–3.4% Al–0.33% Mn alloy were investigated using electron back-scattered diffraction (EBSD) techniques. Compression tests were carried out at 350 °C with a strain rate of 0.001 s?1 on samples machined from extruded tubes. Three types of microstructural features were produced at this temperature: (i) microbands (MBs); (ii) bulged regions; (iii) new grains formed by continuous dynamic recrystallization (cDRX). The formation of the MBs is attributed to the collection of basal dislocations in the MB boundaries. Both the bulges as well as the new cDRX grains are formed as a result of dislocation-based processes that produce c-axis rotations toward the loading axis (i.e. away from the radial direction–transverse direction (RD–TD) plane). Once nuclei have formed, however, the new grains have their c-axes located fairly close to the RD–TD plane. In this way dynamic recrystallization leads to the retention of the main characteristics of the initial RD–TD texture.  相似文献   
930.
A hybrid technology of inductive contact joining (ICJ) was developed to join fibre-reinforced thermoplastics (FRP) with metals by using a tool with single-sided heating. In comparison to conventional methods with separate heating, pressing and cooling, the unique new hybrid ICJ process is characterized by combining all three steps into one hybrid process. The maximum temperature is shifted toward the joining zone due to the direct cooling effect of the surface. FE simulations showed the temperature distributions within the joint. The performed experiments provided data for the temperature profile of the process and the resulting strength of the joint, type of damage and microstructural characteristics. Proven advantages include very short cycle time, competitive joint strength and limited influence on the mechanical properties of the metallic component.  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