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   833篇
  免费   68篇
电工技术   13篇
化学工业   248篇
金属工艺   26篇
机械仪表   32篇
建筑科学   26篇
矿业工程   1篇
能源动力   20篇
轻工业   172篇
水利工程   3篇
石油天然气   10篇
无线电   39篇
一般工业技术   101篇
冶金工业   111篇
原子能技术   4篇
自动化技术   95篇
  2024年   2篇
  2023年   10篇
  2022年   23篇
  2021年   48篇
  2020年   30篇
  2019年   40篇
  2018年   52篇
  2017年   39篇
  2016年   40篇
  2015年   36篇
  2014年   33篇
  2013年   60篇
  2012年   49篇
  2011年   62篇
  2010年   41篇
  2009年   38篇
  2008年   30篇
  2007年   32篇
  2006年   19篇
  2005年   25篇
  2004年   16篇
  2003年   7篇
  2002年   12篇
  2001年   13篇
  2000年   4篇
  1999年   11篇
  1998年   32篇
  1997年   23篇
  1996年   20篇
  1995年   10篇
  1994年   7篇
  1993年   10篇
  1992年   4篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1979年   1篇
  1978年   1篇
  1976年   5篇
  1973年   1篇
  1963年   1篇
  1957年   1篇
排序方式: 共有901条查询结果,搜索用时 15 毫秒
41.
For the first time, we show that Tritrichomonas foetus can adhere on superhydrophilic vertically aligned carbon nanotubes (VACNT) films. Scanning electron microscopy shows an unusual adhesion with a higher membrane filopodium projection in all directions, directly attached to superhydrophilic VACNT tips.  相似文献   
42.
New carbon composite materials were prepared by pyrolysis of mixture of coffee wastes and red mud at 700 °C with the inorganic: organic ratios of 1.9 (CC-1.9) and 2.2 (CC-2.2). These adsorbents were used to remove reactive orange 16 (RO-16) and reactive red 120 (RR-120) textile dyes from aqueous solution. The CC-1.9 and CC-2.2 materials were characterized using Fourier transform infrared spectroscopy, Nitrogen adsorption/desorption curves, scanning electron Microscopy and X-ray diffraction. The kinetic of adsorption data was fitted by general order kinetic model. A three-parameter isotherm model, Liu isotherm model, gave the best fit of the equilibrium data (298 to 323 K). The maximum amounts of dyes removed at 323 K were 144.8 (CC-1.9) and 139.5 mg g?1 (CC-2.2) for RO-16 dye and 95.76 (CC-1.9) and 93.80 mg g?1 (CC-2.2) for RR-120 dye. Two simulated dyehouse effluents were used to investigate the application of the adsorbents for effluent treatment.  相似文献   
43.
This work describes the utilization of a Pt UME in the study of the hydrogen evolution reaction in 0.5 M H2SO4. A non-linear fitting procedure was employed in order to analyze polarization curves obtained at several temperatures (25–75 °C). The results revealed that the traditionally accepted model described by a Volmer–Tafel route fails to fit the obtained experimental data. In this sense, a new model was proposed involving the Volmer–Heyrovsky mechanism, being the Heyrovsky reaction rate determining step. To achieve the best fit between experimental and calculated data, the kinetic equations had to be proposed with a small value of the transfer coefficient (β<0.2). This unusual value was associated with an activationless process, which can also justify the limiting kinetic current (not diffusional) observed. Trying to get further insight into this possibility, the polarization studies were also performed on a surface modified by underpotentially deposited copper. With a degree of coverage as high as 0.8, the only observed effect on the polarization curves was a shift towards minor current values. This shift can be completely justified by the blocking of surface area. A change in mechanism was not observed albeit the Cu UPD eliminated the pairs of neighbor active sites necessary to the Volmer–Tafel pathway.  相似文献   
44.
We employ finite elements methods for the approximation of solutions of the Ginzburg-Landau equations describing the deconfinement transition in quantum chromodynamics. These methods seem appropriate for situations where the deconfining transition occurs over a finite volume as in relativistic heavy ion collisions, where in addition expansion of the system and flow of matter are important. Simulation results employing finite elements are presented for a Ginzburg-Landau equation based on a model free energy describing the deconfining transition in pure gauge SU(2) theory. Results for finite and infinite system are compared.  相似文献   
45.
46.
The MRMAX chart is a single chart based on the standardized sample means and sample ranges for monitoring the mean vector and the covariance matrix of multivariate processes. User’s familiarity with the computation of these statistics is a point in favor of the MRMAX chart. As a single chart, the recently proposed MRMAX chart is very appropriate for supplementary runs rules. In this article, we compare the supplemented MRMAX chart and the synthetic MRMAX chart with the standard MRMAX chart. The supplementary and the synthetic runs rules enhance the performance of the MRMAX chart.  相似文献   
47.
The chitosan biopolymer can be used as a proton‐conducting membrane in proton‐exchange membrane fuel cell. In the forms that they have normally obtained and tested, chitosan membranes typically show poor performance in conduction of protons, requiring modifications in the structure of the biopolymer or blending with other polymers to increase its proton conductivity. The present work investigates the individual properties of chitosan and relates them to the proton conductivity performance of membranes composed of this polymer. Evaluation was made of the effects of variables such as the degree of deacetylation (DD) and the molar mass (Mv) of chitosan membranes without addition of any other polymer. The DD and Mv values of the chitosan used to produce membranes determined the proton conduction, with lower DD and higher Mv resulting in higher conductivity. The thicker membranes presented greater crystallinity, with conductivity between 2.0 × 10?4 and 1.8 × 10?3 S cm?1. The characteristic stages of degradation of the chitosan membranes were in the ranges 200 to 300°C and 500 to 600°C, indicating good thermal stability of the material.  相似文献   
48.
Phagocytosis in embryos was studied by Elie Metchnikoff more than a century ago and is a pillar of the Phagocytic Theory. Throughout the last three decades phagocytosis in embryos has been studied from different perspectives, which this review describes and analyzes. The following branches were identified: 1) the search for the origin and first identification of well-known adult phagocytes in embryos, including their role after induced injuries; 2) the search for the occurrence of phagocytosis in embryos and its role during their physiological development; and 3) the search for phagocytosis in embryos, as a tool to study identity and self-recognition. It is possible to verify that different cell types are able to undertake phagocytosis, under a variety of different stimuli, and that the nature of what is phagocytosed also varies widely. Although the overwhelming majority of species described among metazoarians are invertebrates, most published articles in this field relate to mammals (particularly mice and humans) and birds (particularly chicks). In order to enrich this field of knowledge, research using a wider variety of vertebrate and invertebrate species should be undertaken. Furthermore, the present knowledge of phagocytosis in embryos needs a revised paradigm capable of embracing all the above-mentioned research trends under a single, more general, biological theory. In this sense, Metchnikoff's Phagocytic Theory, which is based on a broad biological paradigm and is thus capable of dealing with all research trends mentioned herein, should be revisited in order to contribute to this edification.  相似文献   
49.
This paper presents an approach for the generation of test purposes in the form of labelled transition systems from specifications of properties in CTL. The approach is aimed at adapting the model checking process, by extending search algorithms to perform further analysis so that examples and counter-examples can be extracted. An algorithm for the generation of test purposes through analysis over the examples and counter-examples is presented, along with a case study to show the correspondence between the CTL properties and the generated test purposes.  相似文献   
50.
The authors calculated the shunt revision rate for 77 consecutive patients with tumoural obstructive hydrocephalus. At a mean follow up of 23.7 months, the annual revision rate was 0.06 which is significantly lower than the annual revision rate of 0.39 for other hydrocephalic patients treated during the same period. Shunted patients who had total excision of their lesions had a significantly lower revision rate than patients who had a partial excision or a biopsy. It is therefore, suggested that cases with tumoural obstructive hydrocephalus may represent a subset of hydrocephalic patients who are associated with a relatively low risk of shunt complications. The observation has to be addressed when the role of endoscopic third ventriculostomy in these patients is being considered.  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