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   964篇
  免费   39篇
  国内免费   1篇
电工技术   14篇
化学工业   151篇
金属工艺   10篇
机械仪表   13篇
建筑科学   18篇
矿业工程   1篇
能源动力   39篇
轻工业   74篇
水利工程   8篇
石油天然气   2篇
无线电   36篇
一般工业技术   88篇
冶金工业   477篇
原子能技术   4篇
自动化技术   69篇
  2023年   3篇
  2022年   11篇
  2021年   23篇
  2020年   4篇
  2019年   21篇
  2018年   24篇
  2017年   14篇
  2016年   15篇
  2015年   17篇
  2014年   26篇
  2013年   39篇
  2012年   32篇
  2011年   36篇
  2010年   30篇
  2009年   23篇
  2008年   23篇
  2007年   21篇
  2006年   23篇
  2005年   17篇
  2004年   19篇
  2003年   16篇
  2002年   13篇
  2001年   13篇
  2000年   18篇
  1999年   23篇
  1998年   137篇
  1997年   96篇
  1996年   56篇
  1995年   32篇
  1994年   32篇
  1993年   26篇
  1992年   7篇
  1991年   2篇
  1990年   9篇
  1989年   9篇
  1988年   2篇
  1987年   9篇
  1986年   2篇
  1985年   3篇
  1984年   3篇
  1982年   4篇
  1981年   3篇
  1980年   4篇
  1978年   3篇
  1977年   15篇
  1976年   35篇
  1974年   2篇
  1967年   1篇
  1966年   1篇
  1962年   1篇
排序方式: 共有1004条查询结果,搜索用时 15 毫秒
41.
在市场经济条件下,国有企业要生存和发展,就必须重视和加强管理创新。文中就企业创新管理中的理念、决策、战略、组织结构、人本管理这5个方面的管理创新等问题进行了阐述,对企业创新管理具有一定的指导意义。  相似文献   
42.
A gel filtration chromatographic method has been developed which is capable of fractionating amylose and amylopectin in starch. Three GFC columns (2 × 4000 A and 1 × 300A PL Separation Sciences, Polymer Laboratories Ltd,) are used in series using sodium chloride solution as eluent. Minimal sample preparation is involved which includes a preliminary wetting of powder starch with ethanol followed by dissolution with sodium hydroxide. Since the solvent system is aqueous, cooked starch samples are analysed by direct dissolution with sodium hydroxide. The method shows promise as a rapid technique in elucidating starch structure.  相似文献   
43.

Background  

Mexico has seen a very steep increase in child obesity level. Little is known about caloric beverage intake in this country as well as all other countries outside a few high income countries. This study examines overall patterns and trends in all caloric beverages from two nationally representative surveys from Mexico.  相似文献   
44.
Monomers or N-alkoxyamine initiators containing protected thiol groups are utilized to prepare polymers via nitroxide-mediated radical polymerization. Following thiol deprotection, the macromolecular properties of these polymers are manipulated, by adjusting the redox conditions to either form or cleave disulfide bonds, or irreversibly cap free thiols by the rapid addition to a maleimide Michael acceptor. Formation of disulfide bonds under dilute conditions results in intramolecular disulfide formation, resulting in internal polymer collapse. Alternatively, disulfide formation under high concentration results in intermolecular crosslinking of polymers to form networked macromolecular assemblies.  相似文献   
45.
A total of 260 samples from six food groups (grains and grain products, tree nuts, dried fruits, fresh produce, fruit juice, and dairy products) were tested for levels of fungal contamination using the SimPlate Yeast and Mould Color Indicator (YM-CI) and the FDA official (BAM) method. Results showed that the SimPlate, in most cases, gave higher yeast and mould (YM) counts than the FDA (reference) method. Statistical analysis of the data (paired t-test) revealed that there were significant differences (α = 0.05) between the two methods for several foods tested. The SimPlate was easy to use, saved time during sample preparation and inoculation and gave results faster than the reference method. Some difficulties were encountered when spreading moulds were present.  相似文献   
46.
This paper presents a new evolutionary cooperative–competitive algorithm for the design of Radial Basis Function Networks (RBFNs) for classification problems. The algorithm, CO2RBFN, promotes a cooperative–competitive environment where each individual represents a radial basis function (RBF) and the entire population is responsible for the final solution. The proposal considers, in order to measure the credit assignment of an individual, three factors: contribution to the output of the complete RBFN, local error and overlapping. In addition, to decide the operators’ application probability over an RBF, the algorithm uses a Fuzzy Rule Based System. It must be highlighted that the evolutionary algorithm considers a distance measure which deals, without loss of information, with differences between nominal features which are very usual in classification problems. The precision and complexity of the network obtained by the algorithm are compared with those obtained by different soft computing methods through statistical tests. This study shows that CO2RBFN obtains RBFNs with an appropriate balance between accuracy and simplicity, outperforming the other methods considered.  相似文献   
47.
This work presents the numerical simulation of a laboratory reactor with rotating cylinder electrode (RCE) and a six-plate counter electrode that is used in studies on heavy metal recovery. The rate of electrode rotation and the potential applied are of such magnitude that the electrochemical reactor works in conditions of mass transport control under turbulent flow to obtain high recovery rates and formation of dendritic metal deposits. For hydrodynamics, the Reynolds averaged Navier–Stokes (RANS) equations were solved using the standard kε turbulence model, as well as wall functions based on the universal velocity distribution in the near-wall region. Results of 3-D simulations of the velocity field show clearly the formation of the turbulence Taylor vortex flow. For mass transfer, convection–diffusion equation was solved using the Kays–Crawford model for turbulent Schmidt number and Launder–Spalding wall functions adapted for mass transfer. Kinetics of copper recovery from aqueous solutions containing 0.019 M CuSO4 and 1 M H2SO4, in the range of rotation speed of 400–1100 rpm, was adequately fit (error <8%) during the electrolysis time to achieve a final recovery of 85% for potentiostatic and 60% for galvanostatic experiments. The fitting parameter of the concentration wall function used in all experiments was A=2.9.  相似文献   
48.
49.
This research was focused on the production of polyunsaturated fatty acid concentrates from a farmed rainbow trout (Oncorhynchus mykiss) by‐product (i.e. belly muscle). The effect of different process variables (urea/fatty acids (FA) contents ratio, crystallisation time and temperature and stirring speed of the urea/FA mixture) on the lipid oxidation development during the urea complexation process was investigated. For this purpose, an experimental design (26 runs) following the response‐surface methodology was developed. As a result, peroxide value and TOTOX index showed to be dependent on the crystallisation time and temperature and the urea/FA ratio, while no influence of the crystallisation stirring speed was detected on both indices; additionally, polyene index was affected by the urea/FA ratio and its interaction with the crystallisation time. An optimised desirability score near 1.0 was attained provided values of 2.8 °C, 3.05 h and 3.57 were applied for crystallisation temperature, crystallisation time and urea/FA ratio, respectively.  相似文献   
50.
A quadratic cost functional for reconstruction of a high-resolution wave front from a coarse wave front is presented. The functional uses as data the position and the direction of the coarse wave front that had previously been computed with a ray-tracing method. This functional uses an optical relationship between the ray information and the wave front's shape to reconstruct a high-density wave front. The performance of the proposed functional is illustrated by reconstruction of complicated wave fronts for which this functional has an accuracy that is superior to that of conventional interpolation methods.  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