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   300篇
  免费   12篇
  国内免费   1篇
电工技术   8篇
化学工业   56篇
金属工艺   7篇
机械仪表   12篇
建筑科学   6篇
能源动力   13篇
轻工业   20篇
无线电   16篇
一般工业技术   88篇
冶金工业   36篇
原子能技术   7篇
自动化技术   44篇
  2023年   6篇
  2022年   11篇
  2021年   15篇
  2020年   10篇
  2019年   2篇
  2018年   10篇
  2017年   5篇
  2016年   9篇
  2015年   6篇
  2014年   7篇
  2013年   13篇
  2012年   15篇
  2011年   24篇
  2010年   16篇
  2009年   19篇
  2008年   19篇
  2007年   16篇
  2006年   11篇
  2005年   11篇
  2004年   5篇
  2003年   9篇
  2002年   13篇
  2001年   3篇
  2000年   4篇
  1999年   1篇
  1998年   8篇
  1997年   3篇
  1996年   2篇
  1995年   5篇
  1994年   6篇
  1993年   5篇
  1992年   5篇
  1991年   1篇
  1990年   1篇
  1989年   4篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1982年   1篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1962年   1篇
  1961年   1篇
排序方式: 共有313条查询结果,搜索用时 10 毫秒
101.
Legal probabilism is the view that juridical fact-finding should be modeled using Bayesian methods. One of the alternatives to it is the narration view, according to which instead we should conceptualize the process in terms of competing narrations of what (allegedly) happened. The goal of this paper is to develop a reconciliatory account, on which the narration view is construed from the Bayesian perspective within the framework of formal Bayesian epistemology.  相似文献   
102.
The Helicity Injected Torus with Steady Inductive Helicity Injection (HIT-SI) consists of an axisymmetric flux conserver and two half-torus magnetic helicity injectors, mounted on either side of the axisymmetric confinement region (Jarboe et al., 2006, Phys. Rev. Lett., 97, 115003). Current and flux are driven sinusoidally with time in each injector, injecting both power and magnetic helicity into the HIT-SI device, with the goal of forming and sustaining a spheromak in the confinement region. Recent HIT-SI results include formation of discharges with toroidal spheromak current 1.5 times the injector current amplitude, development of a Taylor-state model for the magnetic fields in HIT-SI discharges, and direct measurement of the portion of the induced injector electric field that drives current in the confinement region.  相似文献   
103.
The purpose of the present work is a parametrical study of the interaction between a propagating edge-crack and an embedded elastic fibre using the Boundary Element (BE) technique. Uniaxial fibre reinforced composites generally have very good properties in the direction of the fibres, but in conventional multi-layer crossply laminates it is cracking in the transverse direction which effectively limits the strength of a stressed body. Therefore, in this study the propagation of a crack in the transverse direction is considered, i.e., in a plane containing the fibre axes, rather than perpendicular to the fibres. Crack deflection/attraction mechanisms and their associated energy release rate variations are investigated for a range of Young's moduli and Poisson's ratio mismatches, and crack offsets with respect to the inclusion centreline. Furthermore, the effects of a third-phase, i.e., coating, applied to the fibre's surface are analysed, and results have been obtained for different coating thicknesses and elastic moduli ratios. From this investigation it was found that the Poisson's ratio of the different phases could have a significant effect on the crack trajectory, and hence the energetics involved in the process of crack deflection are also dramatically altered. This opens up the possibility of enhancing the fracture toughness of fibre reinforced composite materials by considering the Poisson's ratio of the individual phases when selecting the particular material combination.  相似文献   
104.
The paper presents the results of extensive experimental research focused on the analysis of deformation conditions in multi‐pass drawing process. The wire rod of medium and high‐carbon steel manufactured with application of controlled cooling rate after hot rolling was chosen as the material to be drawn. Suitability of the wire rod for the multi‐pass drawing process was assessed by means of detailed analysis of mechanical properties of a material before drawing, after each pass as well as of the final product. The drawing process was realised without intermediate heat treatment, assuming maximum possible reduction to be attained. The effect of history of deformation (distribution and number of unit reductions, die geometry) on the mechanical properties of drawn wires was analysed. The force parameters of the drawing process were also evaluated in detail, which allowed for an attempt to determine the optimum drawing conditions. The separate part of work was the upper‐bound process modelling which included calculations of the components of power of deformation as well as the analysis of state of strain by means of strain redundancy factor evaluation. Finally, conclusions were formulated concerning suitability of the investigated wire rod for deep cold working as well as the influence of history of deformation on the product quality.  相似文献   
105.
A large volume microwave plasma generator was used for producing thin plasma-polymerized (PP) films as corrosion protection on metal substrates.Through the control of plasma polymerization variables (“monomer” vapour, pressure, power density and substrate temperature), strongly adhering, pinhole-free and highly cross-linked coatings can be deposited on metal surfaces. Numerous monomer-metal combinations were tested and PP films were found to outperform “conventional” polymeric coatings in various corrosive media. Organosilicone films appear to hold particular promise as they have excellent mechanical properties and are stable up to high (>800°C) temperatures. Carbon steel substrates with coatings 2 μ thick were found to withstand a simulated marine environment for periods of several weeks with no trace of corrosion.  相似文献   
106.
The purpose of this work is to apply an inverse boundary element formulation in order to develop efficient algorithms for identification of polarization curves in a cathodic protection system. The problem is to minimize an objective function measuring the difference between observed and BEM‐predicted surface potentials. The numerical formulation is based on the application of genetic algorithms, which are robust search techniques emulating the natural process of evolution as a means of progressing towards an optimum solution. Examples of application are included in the paper for different types of polarization curves in finite and infinite electrolytes. The accuracy and efficiency of the numerical results are verified by comparison with standard conjugate gradient techniques. As a result of this research, the genetic algorithm approach is shown to be more robust, independent of the position of the sensors and of initial guesses, and will be further developed for three‐dimensional applications. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
107.
Identification of liver cancer-specific aptamers using whole live cells   总被引:4,自引:0,他引:4  
Liver cancer is the third most deadly cancers in the world. Unfortunately, there is no effective treatment. One of the major problems is that most cancers are diagnosed in the later stage, when surgical resection is not feasible. Thus, accurate early diagnosis would significantly improve the clinical outcome of liver cancer. Currently, there are no effective molecular probes to recognize biomarkers that are specific for liver cancer. The objective of our current study is to identify liver cancer cell-specific molecular probes that could be used for liver cancer recognition and diagnosis. We applied a newly developed cell-SELEX (Systematic Evolution of Ligands by EXponential enrichment) method for the generation of molecular probes for specific recognition of liver cancer cells. The cell-SELEX uses whole live cells as targets to select aptamers (designed DNA/RNA) for cell recognition. In generating aptamers for liver cancer recognition, two liver cell lines were used: a liver cancer cell line BNL 1ME A.7R.1 (MEAR) and a noncancer cell line, BNL CL.2 (BNL). Both cell lines were originally derived from Balb/cJ mice. Through multiple rounds of selection using BNL as a control, we have identified a panel of aptamers that specifically recognize the cancer cell line MEAR with Kd in the nanomolar range. We have also demonstrated that some of the selective aptamers could specifically bind liver cancer cells in a mouse model. There are two major new results (compared with our reported cell-SELEX methodology) in addition to the generation of aptamers specifically for liver cancer. The first one is that our current study demonstrates that cell-based aptamer selection can select specific aptamers for multiple cell lines, even for two cell lines with minor differences (MEAR cell is derived from BNL by chemical inducement); and the second result is that cell-SELEX can be used for adhesive cells and thus open the door for solid tumor selection and investigation. The newly generated cancer-specific aptamers hold great promise as molecular probes for cancer early diagnosis and basic mechanism studies.  相似文献   
108.
In this work, Lactobacillus casei rhamnosus were obtained from the commercial product of fermented milk and possible antagonistic effect of selenium (as sodium selenite) against cadmium toxicity was studied. The bacteria capability to incorporate Se was demonstrated: after 1 week exposure to Se(IV), its total concentration in the freeze-dried biomass was 405+/-28 microg/g (7.4+/-0.8 microg/g in control). In the presence of Se(IV) and Cd(II), the bacterial growth and cell viability were improved and lipid peroxidation less marked with respect to bacteria exposed to Cd(II) alone. The distribution of Se and Cd in molecular mass fractions of bacteria extracts was investigated by size exclusion chromatography with diode array and ICP-MS detection. The results obtained suggest that the antagonistic effect of Se is due to lower incorporation of cadmium at a high molecular mass (MM<600 kDa). Slightly different distribution of elements in the fractions of MM<40 kDa suggests the formation of new chemical species involving Cd and Se in bacteria exposed to Cd(II)+Se(IV) as compared to those exposed to Cd(II) alone. The study illustrates the high utility of atomic spectrometry to critically inform molecular questions that could be important in the industrial processes based on bacterial activity.  相似文献   
109.
Transmission electron microscopes fitted with field-emission guns (to provide coherent electron waves) can be adapted to record the magnetic fields within and surrounding nanoparticles or metal clusters, for example, the lines of force of a nanoferromagnet encapsulated within a multiwalled carbon nanotube. Whereas most chemists are aware that electron microscopy readily identifies crystallographic symmetries and phases, solves structures, and, in conjunction with electron energy-loss spectroscopy, yields valence states and electronic information of materials, relatively few know that it can also provide important quantitative information, with nanometer-scale spatial resolution, pertaining to such materials' magnetic properties. In this Account, with the aid of representative examples embracing solid-state chemistry, geochemistry, and bio-inorganic phenomena, we illustrate how off-axis electron holography affords deep insight into magnetic phenomena on the nanoscale. Specifically, we describe the unprecedented level of information available regarding the magnetic nature of magnetotactic bacteria, magnetic nanoparticle chains and chiral bracelets, and geochemically relevant phenomena involving exsolution (the un-mixing of two mineral phases, as in the magnetite-ulv?spinel system). It is, for example, possible to reveal vortices and multidomain states that have no net magnetization in minute blocks of magnetite. With the current burgeoning interest and activity in nanoscience and nanotechnology, our Account concludes with examples of some existing enigmas that electron holography, especially when augmented by the related technique of electron tomography, might play an important experimental role in resolving, such as the occurrence of ferromagnetism in nanocrystals of silver within carbon tubes and in clusters of alkali metals incarcerated within zeolites.  相似文献   
110.
Electron tomography and electron holography experiments have been combined to investigate the 3D electrostatic potential distribution in semiconductor devices. The experimental procedure for the acquisition and data reconstruction of holographic tilt series of silicon p-n junction specimens is described. A quantitative analysis of the experimental results from specimens of two different thicknesses is presented, revealing the 3D electrostatic potential variations arising from the presence of surfaces and damage generated by focused ion beam (FIB) sample preparation. Close to bulk-like properties are measured in the centre of the tomographic reconstruction of the specimen, revealing higher electrically active dopant concentrations compared to the measurements obtained at the specimen surfaces. A comparison of the experimental results from the different thickness specimens has revealed a 'critical' thickness for this specimen preparation method of 350nm that is required for this device structure to retain 'bulk'-like properties in the centre of the membrane.  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