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   538篇
  免费   3篇
  国内免费   1篇
电工技术   3篇
综合类   3篇
化学工业   154篇
金属工艺   12篇
机械仪表   6篇
建筑科学   27篇
能源动力   33篇
轻工业   40篇
水利工程   1篇
石油天然气   3篇
无线电   48篇
一般工业技术   101篇
冶金工业   37篇
原子能技术   11篇
自动化技术   63篇
  2022年   7篇
  2021年   9篇
  2020年   4篇
  2019年   6篇
  2018年   6篇
  2017年   6篇
  2016年   5篇
  2015年   8篇
  2014年   9篇
  2013年   22篇
  2012年   21篇
  2011年   31篇
  2010年   29篇
  2009年   26篇
  2008年   36篇
  2007年   32篇
  2006年   25篇
  2005年   26篇
  2004年   19篇
  2003年   26篇
  2002年   18篇
  2001年   10篇
  2000年   6篇
  1999年   11篇
  1998年   9篇
  1997年   12篇
  1996年   13篇
  1995年   5篇
  1994年   5篇
  1993年   7篇
  1992年   4篇
  1991年   7篇
  1990年   6篇
  1989年   6篇
  1988年   5篇
  1987年   7篇
  1986年   4篇
  1985年   5篇
  1984年   2篇
  1983年   4篇
  1982年   7篇
  1981年   8篇
  1980年   4篇
  1979年   5篇
  1978年   4篇
  1976年   3篇
  1975年   2篇
  1973年   5篇
  1972年   1篇
  1970年   1篇
排序方式: 共有542条查询结果,搜索用时 15 毫秒
111.
Rigid vinyl can be considered as a highly versatile thermoplastic, finding its way into many different applications. Vinyl's capacity for innovation is virtually limitless, thanks in part to advances in formulation additives, which have enlarged vinyl's processing and end-use performance capabilities. The importance of formulating is particularly evident in rigid cellular PVC, which can be extruded into a variety of shapes, such as profile, pipe, and sheet, all made with less PVC than their solid counterparts. The sheet application can be especially challenging, and it has been made the subject of this paper. The various types of extrusion processes, formulations, and uses for rigid cellular PVC sheet that are found in North America and Europe are compared. The effect of certain types of formulation ingredients on sheet density, surface, and impact strength is described. Reference is made to coextrusion of solid/cellular PVC layers as an economically feasible approach to handling industrial regrind PVC.  相似文献   
112.
Attacks on smart cards can only be based on a black box approach where the code of cryptographic primitives and operating system are not accessible. To perform hardware or software attacks, a white box approach providing access to the binary code is more efficient. In this paper, we propose a methodology to discover the romized code whose access is protected by the virtual machine. It uses a hooked code in an indirection table. We gained access to the real processor, thus allowing us to run a shell code written in 8051 assembly language. As a result, this code has been able to dump completely the ROM of a Java Card operating system. One of the issues is the possibility to reverse the cryptographic algorithm and all the embedded countermeasures. Finally, our attack is evaluated on different cards from distinct manufacturers.  相似文献   
113.
A novel electrochemical aptasensor, based on disposable screen-printed electrodes was developed for the sensitive detection of the mycotoxin ochratoxin A (OTA). Two strategies were investigated by using an indirect and a direct competitive assay, based on the use of superparamagnetic nanoparticles. The performance of the optimized aptasensors in terms of reproducibility, stability, sensitivity, and analysis time was studied. The best strategy was found to be the direct competitive format. In this assay, free OTA competed with labeled alkaline phosphatase-OTA for the binding to the DNA aptamer immobilized on magnetic beads. The electrochemical detection was thus achieved through a suitable substrate for the enzyme ALP, by Differential Pulse Voltammetry. The aptasensor obtained using this novel approach allowed detection limit of 0.11 ng/mL, and was also validated for real sample analysis.  相似文献   
114.
With the advent and availability of powerful personal computing, the computer music research and industry have been focusing on real-time musical interactions between musicians and computers; delegating human-like actions to computers who interact with a musical environment. One common use-case of this kind is Automatic Accompaniment where the system is comprised of a real-time machine listening system that in reaction to recognition of events in a score from a human performer, launches necessary actions for the accompaniment section. While the real-time detection of score events out of live musicians’ performance has been widely addressed in the literature, score accompaniment (or the reactive part of the process) has been rarely discussed. This paper deals with this missing component in the literature from a formal language perspective. We show how language considerations would enable better authoring of time and interaction during programming/composing and how it addresses critical aspects of a musical performance (such as errors) in real-time. We sketch the real-time features required by automatic musical accompaniment seen as a reactive system. We formalize the timing strategies for musical events taking into account the various temporal scales used in music. Various strategies for the handling of synchronization constraints and the handling of errors are presented. We give a formal semantics to model the possible behaviors of the system in terms of Parametric Timed Automata.  相似文献   
115.
Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1-2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.  相似文献   
116.
This paper presents a theoretical study of the failure rate behavior of components subjected to random environmental stresses. Three kinds of stresses are considered: point, alternating, diffused. The concept that the component could memorize the stress is introduced. Diverse types of stress action can thus be defined: instantaneous, cumulative, recovering. Two classes of stochastic models are proposed, which express the effect of stress to the lifetime of the component. Several examples for which the resulting failure rate has an explicit expression, are presented. In most of these examples, the failure rate converges rapidly to a constant, that confirms a conjecture frequently made by the engineers.  相似文献   
117.
The dynamic behaviour of marine vehicles in extreme sea states is a matter of great concern following some recent and dramatic mishaps. The complex problem of its prediction can be approached from the study, yet of broader scope, of non-linear dynamic systems subjected to stochastic excitations. However, a general non-linear stochastic dynamic theory is not yet available. A new technique, the so-called linearize-and-match method, for predicting the response statistics of non-linear systems, is presented. Essentially, the technique involves the construction of an infinite series of linear systems aimed at the prediction of the response statistical moments of a given order. The linear systems are successively defined by linearizing the original, non-linear system and matching the Volterra functional model response statistics to the desired order. The linear system for predicting second order statistics is shown to coincide with the one obtained using the method of equivalent linearization. Response probability distributions can be constructed from the knowledge of such statistics. Particular attention is devoted to the distribution of maximum entropy and its justification in such underdetermined moment problems. Finally, applications to the roll motion of ships serve to exemplify as well as to assess the accuracy and the versatility of the overall method. Response distributions of maxima so predicted compare very well with digital simulation estimates.  相似文献   
118.
Eosinophils are rare, multifunctional granulocytes. Their growth, survival, and tissue migration mainly depend on interleukin (IL)-5 in physiological conditions and on IL-5 and IL-33 in inflammatory conditions. Preclinical evidence supports an immunological role for eosinophils as innate immune cells and as agents of the adaptive immune response. In addition to these data, several reports show a link between the outcomes of patients treated with immune checkpoint inhibitors (ICI) for advanced cancers and blood eosinophilia. In this review, we present, in the context of non-small cell lung cancer (NSCLC), the biological properties of eosinophils and their roles in homeostatic and pathological conditions, with a focus on their pro- and anti-tumorigenic effects. We examine the possible explanations for blood eosinophilia during NSCLC treatment with ICI. In particular, we discuss the value of eosinophils as a potential prognostic and predictive biomarker, highlighting the need for stronger clinical data. Finally, we conclude with perspectives on clinical and translational research topics on this subject.  相似文献   
119.
Contraction of the heart is caused by actin filaments sliding along myosin filaments. This generates a frictional force inducing wear of the contractile apparatus. We postulated that this process could be exacerbated when the heart was submitted to severe anoxia. Anoxia induced dramatic abnormalities in the molecular properties of actin-myosin crossbridges. We applied the formalism of far-from-equilibrium thermodynamics to the left ventricular papillary muscles (LVPMs) of mammalian rat hearts which had been subjected to a prolonged anoxia (3 h). We showed that when subjected to prolonged anoxia, the heart operated far-from-equilibrium as evidenced by the non-linearity between thermodynamic force (F/T: Frictional force/Kelvin temperature) and thermodynamic flow (v0: myofilament sliding velocity). The rate of entropy production (EPR) was the product of (F/T) and v0. The excess entropy production (EEP) was equal to δ2St = FTδvo; (S: entropy). The tribological system remained stable when EEP was positive and became unstable when EEP became negative, thus characterizing instability of the system and reflecting the occurrence of self-organization and possibly dissipative structures. After 3 h anoxia, re-oxygenation induced significant reversibility. About 20% of the myosin heads did not recover despite re-oxygenation. These results may be of importance in the context of heart transplantation where the delay between the time of sampling from the donor and the time of the graft installation in the recipient should be as short as possible.  相似文献   
120.
Intermittent hypoxia (IH), the major feature of obstructive sleep apnea syndrome (OSAS), induces atherosclerosis and elastic fiber alterations. VE-cadherin cleavage is increased in OSAS patients and in an IH-cellular model. It is mediated by HIF-1 and Src-tyr-kinases pathways and results in endothelial hyperpermeability. Our aim was to determine whether blocking VE-cadherin cleavage in vivo could be an efficient strategy to inhibit deleterious IH-induced vascular remodeling, elastic fiber defects and atherogenesis. VE-cadherin regulation, aortic remodeling and atherosclerosis were studied in IH-exposed C57Bl/6J or ApoE-/-mice treated or not with Src-tyr-kinases inhibitors (Saracatinib/Pazopanib) or a HIF-1 inhibitor (Acriflavine). Human aortic endothelial cells were exposed to IH and treated with the same inhibitors. LDL and the monocytes transendothelium passage were measured. In vitro, IH increased transendothelium LDL and monocytes passage, and the tested inhibitors prevented these effects. In mice, IH decreased VE-cadherin expression and increased plasmatic sVE level, intima-media thickness, elastic fiber alterations and atherosclerosis, while the inhibitors prevented these in vivo effects. In vivo inhibition of HIF-1 and Src tyr kinase pathways were associated with the prevention of IH-induced elastic fiber/lamella degradation and atherogenesis, which suggests that VE-cadherin could be an important target to limit atherogenesis and progression of arterial stiffness in OSAS.  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