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   2733篇
  免费   140篇
  国内免费   1篇
电工技术   21篇
化学工业   517篇
金属工艺   90篇
机械仪表   131篇
建筑科学   45篇
矿业工程   31篇
能源动力   95篇
轻工业   178篇
水利工程   31篇
石油天然气   90篇
无线电   307篇
一般工业技术   644篇
冶金工业   151篇
原子能技术   79篇
自动化技术   464篇
  2023年   23篇
  2022年   29篇
  2021年   89篇
  2020年   79篇
  2019年   76篇
  2018年   112篇
  2017年   91篇
  2016年   128篇
  2015年   90篇
  2014年   117篇
  2013年   198篇
  2012年   177篇
  2011年   196篇
  2010年   135篇
  2009年   106篇
  2008年   132篇
  2007年   117篇
  2006年   80篇
  2005年   57篇
  2004年   66篇
  2003年   54篇
  2002年   68篇
  2001年   40篇
  2000年   26篇
  1999年   30篇
  1998年   42篇
  1997年   45篇
  1996年   25篇
  1995年   19篇
  1994年   15篇
  1993年   12篇
  1991年   13篇
  1990年   21篇
  1989年   17篇
  1987年   15篇
  1986年   18篇
  1985年   12篇
  1983年   11篇
  1982年   17篇
  1981年   17篇
  1979年   18篇
  1978年   24篇
  1977年   24篇
  1976年   14篇
  1975年   19篇
  1973年   16篇
  1972年   14篇
  1971年   14篇
  1970年   13篇
  1969年   14篇
排序方式: 共有2874条查询结果,搜索用时 14 毫秒
1.
Journal of Materials Science: Materials in Electronics - The increasing demand for lithium-ion batteries has stimulated the investigation of new compounds in order to reduce the costs and the...  相似文献   
2.
Refinement of atomic models is a necessary step in solving the macromolecular structure by X-ray diffraction methods. Nowadays, high automation and well-developed interfaces give a possibility to use the most popular refinement programs as black boxes. Nevertheless, working with complex objects requires an understanding of the internal structure and principles of operation of these programs and critical assessment of the results of refinement. In this review, we discuss the basic principles of the organization of refinement programs and the history of their improvement and development, as the studied objects became more and more complicated. The discussions are kept at the level of basic mathematic knowledge avoiding unnecessary formalism and too detailed expressions.  相似文献   
3.
This study investigated the effect of the combination of basic electrolysed water (BEW) and slightly acid electrolysed water (SAEW) with ultrasound (US) for cleaning and sanitation of the knives used in slaughtering processes. The knives were sonicated in a US bath using two modes of operation (normal and sweep) in two steps: (i) 5 min with BEW and (ii) 10 min with SAEW at 35 °C. The microbiological counts and the possible changes in the physical structure of the knives were evaluated. The association BEW + SAEW + US, in the sweep mode, provided lower mesophilic, enterobacterial, Staphylococcus aureus and yeast counts when compared to the values recommended by the international legislation. In addition, these conditions removed all organic residues from the knife blades and promoted the highest migration rate of the residues to the US water bath (12.35 mg/L·min), without modifications in the knife blades. Thus, cleaning and sanitation of knives was feasible with the association of BEW + SAEW + US, which could be a useful alternative for the meat industry.  相似文献   
4.
Topics in Catalysis - This work investigated the photodegradation of bromophenol blue (BPB) and indigo carmine (IC) dye under UV–Visible light using pure oxides of titanium and niobium, as...  相似文献   
5.
Russian Journal of Nondestructive Testing - The results of applying laser-ultrasonic and acoustic-emission nondestructive testing techniques to study the processes of deformation and fracture of...  相似文献   
6.
Anisotropic sintering, including shrinkage and grain growth, was examined for c-axis-oriented (Sr,Ca)2NaNb5O15 (SCNN) ceramics, which were prepared by colloidal processing under a magnetic field. In the c-axis-oriented SCNN powder compact, shrinkage and grain growth along the c-axis were higher than those along the a-axis. The anisotropic microstructural development was clearly associated with anisotropic sintering shrinkage. X-ray diffraction, scanning electron microscopy, and energy back scattering diffraction showed that the grain growth of oriented particles by including random grains contribute to the development of the oriented microstructure. Finally, the highly crystal-oriented SCNN ceramics with a densified microstructure were obtained through anisotropic sintering. These results clearly showed the potential to develop a well-defined anisotropic microstructure during sintering by designing and controlling the particle packing structure in a powder compact.  相似文献   
7.
Protection of Metals and Physical Chemistry of Surfaces - Nickel-based composite electrochemical coatings (CECs) modified with graphite nitrate have been obtained. Their microstructure and...  相似文献   
8.
Hydroxyapatite (HA) nanoparticles (NPs) doped with different radioisotopes for use as theranostic systems play an important role in scientific research nowadays due to their ability to simultaneously act in the treatment and diagnosis of various types of cancers. In this work, we describe the synthesis and characterization of a hydroxyapatite/tenorite nanocomposite functionalized with folic acid, representing a nanotheranostic material with potential for application as an agent in positron emission tomography imaging systems and to act specifically in the treatment and diagnosis of osteosarcoma. 64Cu and 32P were produced by nuclear activation in the TRIGA reactor at CDTN. The obtained samples were characterized by XRD with Rietveld refinement, XAFS, SEM, BET, TGA, FTIR, CHN, ICP-AES, XPS and gamma spectroscopy. We investigated how CuO grows in HA NPs, the stability of the interactions between CuO and HA constituents and the interactions between folic acid and the surface of the HA NPs. The results indicate the formation of a second phase (tenorite) besides hydroxyapatite, and that the interactions between the two phases are stable, resulting in a nanocomposite. Furthermore, the activation of 64Cu and 32P inside the HA matrix, through the exposition to a neutron flux, produces a theranostic material of interest for biological tests.  相似文献   
9.
10.
The catalytic hydrolysis of soybean oil was used as an alternative for the production of monoglycerides (MG) and diglycerides (DG). The reactions were conducted in a stainless-steel tubular reactor in the temperature range of 240–290 °C, on niobium phosphate (NBP) and niobium oxide (NBO) as catalysts. In the hydrolysis reactions at 270 °C, the maximum selectivities of the products of interest were obtained at 22 % MG and 48 % DG for the reaction with NBP, and 7 % MG and 33 % DG with NBO, for 59 % and 36 % of triglyceride conversion in 10 min, respectively. The proposed kinetic model presented a good fit of the theoretical model with the experimental data, showing that the previous hypotheses considered for the mechanism development are suitable for describing the kinetics of soybean oil hydrolysis.  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