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   8524篇
  免费   315篇
  国内免费   14篇
电工技术   46篇
综合类   1篇
化学工业   1075篇
金属工艺   116篇
机械仪表   120篇
建筑科学   89篇
矿业工程   7篇
能源动力   120篇
轻工业   877篇
水利工程   56篇
石油天然气   17篇
无线电   222篇
一般工业技术   658篇
冶金工业   4897篇
原子能技术   28篇
自动化技术   524篇
  2024年   22篇
  2023年   45篇
  2022年   146篇
  2021年   234篇
  2020年   146篇
  2019年   194篇
  2018年   198篇
  2017年   208篇
  2016年   175篇
  2015年   133篇
  2014年   173篇
  2013年   268篇
  2012年   264篇
  2011年   278篇
  2010年   184篇
  2009年   217篇
  2008年   174篇
  2007年   148篇
  2006年   121篇
  2005年   105篇
  2004年   73篇
  2003年   76篇
  2002年   62篇
  2001年   53篇
  2000年   53篇
  1999年   200篇
  1998年   1487篇
  1997年   812篇
  1996年   572篇
  1995年   307篇
  1994年   281篇
  1993年   281篇
  1992年   57篇
  1991年   85篇
  1990年   69篇
  1989年   108篇
  1988年   80篇
  1987年   73篇
  1986年   81篇
  1985年   60篇
  1984年   10篇
  1983年   6篇
  1982年   18篇
  1981年   31篇
  1980年   52篇
  1979年   5篇
  1978年   10篇
  1977年   125篇
  1976年   276篇
  1975年   7篇
排序方式: 共有8853条查询结果,搜索用时 11 毫秒
71.
72.
73.
74.
75.
This article is a discussion of the use of narrow-band light sources coupled with cameras equipped with band-pass filters to document patterned injuries on human skin. Several case reports are included.  相似文献   
76.
We have isolated a putative serine/threonine receptor kinase gene with an expression pattern indicating that it may play a role in the stylar response to pollination. Differential display PCR was used to select tobacco mRNAs with increased accumulation following pollination. NTS16, a cDNA identified by this method, is homologous to a ca. 2.4 kb mRNA primarily expressed in pistil tissues. Levels of this mRNA increase during floral development and are further increased by pollination reaching maximal accumulation 12-18 hours after pollination and then declining. mRNA levels can also be increased by the application of ethylene to unpollinated flowers. A polypeptide encoded by the NTS 16 open reading frame has sequence similarity to the catalytic domain of several receptor protein kinases from plants including the S-receptor kinases implicated in the rejection of self-pollen in Brassica species and the Pto gene product of tomato which confers resistance to a bacterial pathogen.  相似文献   
77.
Catalytic abatement of solutions of 1,000 mg/L in phenol, ortho and para nitrophenol and ortho and para cresols was acomplished by using two catalytic systems. Fenton's reagent was used at 50 degrees C by adding 10 mg/L of ferrous cation and different dosages of H2O2. The mixture was reacting isothermically in a batch way during 3 hours. Catalytic wet oxidation (CWO) was carried out by using a commercial Activated Carbon, Industrial React FE01606A, CWO runs were carried out in a fixed bed reactor (FBR) with concurrent upflow. Temperature and oxygen pressure of the reactor were set to 160 degrees C and 16 bar, respectively. While phenols are quicky oxidised by the Fenton reagent higher mineralisation was obtained in the CWO process.  相似文献   
78.
P. Herbert    L. Santos    M. Bastos    P. Barros    A. Alves 《Journal of food science》2002,67(5):1616-1620
ABSTRACT: A new methodology to the quantification of ethyl carbamate (EC) has been developed. This method allows the analysis by HPLC of ethyl carbamate in samples of wine, fortified wine, and wine brandy, by a pre-column derivatization with 9-xanthydrol, and fluorescence detection. This does not require previous sample extraction or concentration. The method presents an average recovery of 96% among samples studied, a detection limit of 4.2μg/L, and an average intermediate precision of 6.3%. The comparison of the results obtained for EC analysis on the same wine brandy samples by GC/MS and HPLC are statistically indistinguishable with 97.5% probability. The results of the analysis of 42 samples are presented.  相似文献   
79.
Four genes on the short arm of human chromosome 19 (HSA 19p) were assigned to bovine chromosome 7 (BTA 7) using a bovine x rodent somatic hybrid cell panel. These four genes were cartilage oligomeric matrix protein (COMP), lymphoblastic leukemia derived sequence 1 (LYL1), lysosomal alpha-mannosidase (MANB), and RAS oncogene family member RAB3A. Bovine sequence tagged sites were developed for the four genes and used for screening a bovine x rodent somatic cell panel. All four genes were mapped to bovine synteny group U22 (BTA 7) with a correlation coefficient of 0.901-1.000. This study confirms that the centromeric region of BTA 7 is conserved with HSA 19p.  相似文献   
80.
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