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   636篇
  免费   38篇
  国内免费   1篇
电工技术   8篇
综合类   1篇
化学工业   179篇
金属工艺   6篇
机械仪表   7篇
建筑科学   31篇
能源动力   22篇
轻工业   42篇
水利工程   1篇
石油天然气   4篇
无线电   51篇
一般工业技术   103篇
冶金工业   67篇
原子能技术   2篇
自动化技术   151篇
  2024年   3篇
  2023年   4篇
  2022年   18篇
  2021年   32篇
  2020年   27篇
  2019年   27篇
  2018年   27篇
  2017年   24篇
  2016年   30篇
  2015年   18篇
  2014年   27篇
  2013年   37篇
  2012年   40篇
  2011年   49篇
  2010年   33篇
  2009年   27篇
  2008年   28篇
  2007年   15篇
  2006年   23篇
  2005年   9篇
  2004年   16篇
  2003年   6篇
  2002年   14篇
  2001年   6篇
  2000年   5篇
  1999年   8篇
  1998年   15篇
  1997年   13篇
  1996年   8篇
  1995年   8篇
  1994年   3篇
  1993年   6篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1989年   2篇
  1988年   4篇
  1987年   3篇
  1985年   3篇
  1984年   2篇
  1983年   3篇
  1982年   5篇
  1981年   9篇
  1979年   2篇
  1977年   5篇
  1976年   5篇
  1975年   5篇
  1973年   5篇
  1966年   1篇
  1965年   1篇
排序方式: 共有675条查询结果,搜索用时 15 毫秒
1.
2.
Seed kernels ofCalodendrum capense (L.f.) Thunb. yielded 60% of a light yellow oil which had the following fatty acid composition: 23.8% palmitic, 4.5% stearic, 33.7% oleic, 35.6% linoleic, 1.4% linolenic and 1.0% arachidic. Myristic and behenic acids were present in trace amounts, and the kernel cake contained 37.6% crude protein.  相似文献   
3.
Gas hold-up and Sauter mean bubble diameter measurements were made in a 0.051 m diameter by 3 m long glass bubble column in the system, nitrogen-molten wax, with three different waxes (paraffin wax FT-300, Sasol's Arge wax and Mobil's reactor wax). Paraffin wax has a tendency to foam and gas hold-up is a strong function of gas distributor type, temperature and start-up procedure, whereas the reactor waxes do not foam and are much less affected by these variables, In experiments at 265°C with a 1.85 mm single hole orifice plate distributor the gas hold-ups were nearly the same for all three waxes. However, significant differences in Sauter mean bubble diameters were obtained in experiments with different waxes; FT-300 wax produced the smallest Sauter mean bubble diameters whereas Mobil's reactor wax produced the largest bubbles. Addition of 1-octadecanol and octadecanoic acid (up to 10wt%) to the FT-300 paraffin wax caused an increase in gas hold-up and a delay in the foam break-up in runs at 265°C with the 1.85 mm orifice plate distributor.  相似文献   
4.
Analysis of the hornet’s hemolymph revealed the presence of C16 and C18 fatty acids (70%), which were accompanied by minor quantities (ranging from 0.1% to 0.6%) of the following acids: C10∶0, C11∶0, C12∶0, C13∶0, C14∶0, C15∶0, C16∶0, and C17∶0. The hemolymph of the queen larvae contained more C18∶1 than the hemolymph of the worker larvae, and the percentage of C16∶1 was higher in the fat body and the midgut than in the hemolymph. The significance of these results is discussed.  相似文献   
5.
6.
The APSSNMP network management protocol was proposed as a secure alternative to the Simple Network Management Protocol (SNMP) used in the TCP/IP suite. The designers claimed that it resists meet-in-the-middle (MITM) attacks. In this paper, we present an advanced MITM attack on the APSSNMP and hence show that it fails to achieve its design objective of providing better security against MITM attacks. Since the APSSNMP has been presented in several journals, and IEEE and IASTED conferences, our result is important to highlight to network implementers and users of distributed systems that the APSSNMP is not secure for practical deployment.  相似文献   
7.
8.
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   
9.
10.
图像配准是图像变化检测、融合、拼接等技术的 基础,在遥感图像处理领域具有广泛的应用 。利用非抽样Contourlet变换(NSCT)在图像分解上的灵活性,交叉累积剩余熵(CCRE)对遥感图像进行配准的有效性,提出一种基于CCRE和NSCT 的多模式遥感图像配准算法。首先对参考图像和待配准图像分别进行NSCT分解得到低频图像 ,然后采用CCRE作为相似性测度,利用牛顿法获得最优仿射变换模型的 参数对图像进行配准。实验 结果表明,本文方法能够较快的搜索到全局最优解,配准精度高,是一种有效的配准算法。  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