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   1902篇
  免费   77篇
  国内免费   4篇
电工技术   11篇
综合类   1篇
化学工业   398篇
金属工艺   33篇
机械仪表   25篇
建筑科学   49篇
能源动力   33篇
轻工业   104篇
水利工程   5篇
石油天然气   14篇
无线电   139篇
一般工业技术   371篇
冶金工业   492篇
原子能技术   18篇
自动化技术   290篇
  2022年   26篇
  2021年   47篇
  2020年   33篇
  2019年   34篇
  2018年   43篇
  2017年   32篇
  2016年   49篇
  2015年   32篇
  2014年   52篇
  2013年   80篇
  2012年   76篇
  2011年   95篇
  2010年   73篇
  2009年   53篇
  2008年   67篇
  2007年   58篇
  2006年   43篇
  2005年   39篇
  2004年   47篇
  2003年   30篇
  2002年   41篇
  2001年   34篇
  2000年   26篇
  1999年   44篇
  1998年   117篇
  1997年   75篇
  1996年   50篇
  1995年   40篇
  1994年   53篇
  1993年   39篇
  1992年   25篇
  1991年   27篇
  1990年   28篇
  1989年   19篇
  1988年   20篇
  1987年   24篇
  1986年   18篇
  1985年   24篇
  1984年   16篇
  1983年   14篇
  1982年   28篇
  1981年   26篇
  1980年   15篇
  1979年   10篇
  1978年   13篇
  1977年   27篇
  1976年   35篇
  1975年   17篇
  1973年   10篇
  1970年   8篇
排序方式: 共有1983条查询结果,搜索用时 0 毫秒
91.
Periodontitis is a multifactorial disease. The aim of this explorative study was to investigate the role of Interleukin-(IL)-1, IL-4, GATA-3 and Cyclooxygenase-(COX)-2 polymorphisms after non-surgical periodontal therapy with adjunctive systemic antibiotics (amoxicillin/metronidazole) and subsequent maintenance in a Caucasian population. Analyses were performed using blood samples from periodontitis patients of a multi-center trial (ClinicalTrials.gov NCT00707369=ABPARO-study). Polymorphisms were analyzed using quantitative real-time PCR. Clinical attachment levels (CAL), percentage of sites showing further attachment loss (PSAL) ≥1.3 mm, bleeding on probing (BOP) and plaque score were assessed. Exploratory statistical analysis was performed. A total of 209 samples were genotyped. Patients carrying heterozygous genotypes and single-nucleotide-polymorphisms (SNP) on the GATA-3-IVS4 +1468 gene locus showed less CAL loss than patients carrying wild type. Heterozygous genotypes and SNPs on the IL-1A-889, IL-1B +3954, IL-4-34, IL-4-590, GATA-3-IVS4 +1468 and COX-2-1195 gene loci did not influence CAL. In multivariate analysis, CAL was lower in patients carrying GATA-3 heterozygous genotypes and SNPs than those carrying wild-types. For the first time, effects of different genotypes were analyzed in periodontitis progression after periodontal therapy and during supportive treatment using systemic antibiotics demonstrating a slight association of GATA-3 gene locus with CAL. This result suggests that GATA-3 genotypes are a contributory but non-essential risk factor for periodontal disease progression.  相似文献   
92.
93.
Journal of Computational Electronics - Wigner functions, allowing for a reformulation of quantum mechanics in phase space, are of central importance for the study of the quantum-classical...  相似文献   
94.
95.
96.
In this paper, a numerical model for the flow of foams in flotation cells in up to three dimensions is described. By using finite elements to solve Laplace's equation for a potential scalar, the flow pattern and velocity of the foam can be obtained. This has allowed, for the first time, the carrying out of numerical investigations of foam flow patterns regardless of the symmetry of the system. The numerical model has been implemented in Fluidity, a general purpose finite element method code that allows simulations to be carried out on anisotropic unstructured meshes. Such a model is of particular interest since other phenomena occurring in flotation depend on the foam velocity. Convergence tests that verify the numerical model are presented, and simulation results that showcase important features of the present implementation are discussed.  相似文献   
97.
98.
99.
A magnetic resin based on cardanol, furfural, and curaua fibers was prepared and characterized. The material could be used in oil‐spill cleanup processes, because of its aromatic/aliphatic balance. The resin was prepared through bulk polycondensation of cardanol and furfural in the presence of curaua fibers and maghemite nanoparticles. Hydrophobicity of the curaua fibers was improved by acetylation, increasing the oil‐absorbing capability of the composites. The obtained magnetic composites were studied by Fourier‐transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis. Degree of cure, magnetic force, and oil‐removal capability tests were also performed. The results show that the composites possess an elevated cure degree in addition to a considerable magnetic force. The materials exhibit a good oil removal capability in the presence of a magnetic field, which is improved by the use of acetylated curaua. In the best case, the composite filled with maghemite and curaua can remove 12 parts of oil from water. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41732.  相似文献   
100.
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