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   1346篇
  免费   22篇
  国内免费   3篇
电工技术   44篇
综合类   2篇
化学工业   294篇
金属工艺   27篇
机械仪表   36篇
建筑科学   21篇
能源动力   42篇
轻工业   129篇
水利工程   2篇
无线电   106篇
一般工业技术   192篇
冶金工业   365篇
原子能技术   54篇
自动化技术   57篇
  2023年   11篇
  2022年   5篇
  2021年   16篇
  2020年   6篇
  2019年   12篇
  2018年   19篇
  2017年   17篇
  2016年   24篇
  2015年   13篇
  2014年   28篇
  2013年   60篇
  2012年   37篇
  2011年   56篇
  2010年   43篇
  2009年   47篇
  2008年   55篇
  2007年   47篇
  2006年   37篇
  2005年   38篇
  2004年   41篇
  2003年   50篇
  2002年   41篇
  2001年   29篇
  2000年   21篇
  1999年   32篇
  1998年   126篇
  1997年   72篇
  1996年   55篇
  1995年   37篇
  1994年   30篇
  1993年   32篇
  1992年   20篇
  1991年   16篇
  1990年   9篇
  1989年   11篇
  1988年   13篇
  1987年   16篇
  1986年   20篇
  1985年   12篇
  1984年   5篇
  1983年   11篇
  1982年   7篇
  1981年   8篇
  1980年   7篇
  1979年   16篇
  1978年   5篇
  1977年   12篇
  1976年   16篇
  1974年   5篇
  1972年   7篇
排序方式: 共有1371条查询结果,搜索用时 31 毫秒
101.
102.
103.
We propose a low-power two-port SRAM for real-time video processing that exploits statistical similarity in images. To minimize the discharge power on a read bitline, a majority-logic circuit decides if input data should be inverted in a write cycle, so that ldquo1rdquos are in the majority. In addition, for further power reduction, write-in data are reordered into digit groups from the most significant bit group to the least significant bit group. The measurement result of a 68-kbit video memory in a 90-nm process demonstrates that a 45% power saving is achieved on the read bitline. The speed and area overheads are 4% and 7%, respectively.  相似文献   
104.
105.
The relationships between the chemical structures and oxidative fading of the disperse azo dyes, p‐nitrophenylazo‐ and benzothiazoleazo‐anilines, on poly(ethylene terephthalate) substrate are discussed in terms of the parameters k0,i (rate constants of reaction towards 1O2) and fi (photosensitivity), the molecular parameters of molecular orbital theory and substituents in the diazo and coupling components, on the assumption that the initial rates of oxidative fading are proportional to the product of k0,i and fi. 2‐Methoxy‐5‐acetylamino‐N‐substituted aniline couplers exhibited large fi values. 2‐Chloro and 4‐nitro substituents of aniline diazo components exhibited small fi values or high quantum yields of internal conversion, while 4‐nitro substituent did not. A close correlation between N‐substituents and light fastness, proposed by Müller and supplemented by Dawson, demonstrates the applicability of frontier orbital theory, through the highest occupied molecular orbital (HOMO) energy of the dyes, to the analysis of oxidative fading. Dyes with N‐2‐cyanoethyl substituents, which gave a lower HOMO energy, also exhibited superior light fastness compared with N‐2‐hydroxyethyl substituents.  相似文献   
106.
The unprecedented use of a soluble organoindium species, indium(III) hexamethyldisilazide [In(III)(hmds)3], for catalytic carbon carbon bond formations between ketones and boronates, is reported. Various functionalized tertiary homoallyl alcohols were generated easily in high yields. Remarkably, free hydroxy and primary amine functionalities proved to be tolerated. A rate acceleration and markedly improved diastereoselectivities were observed in the presence of methanol. Based on preliminary NMR experiments and the α‐selectivity with an α‐substituted boronate, we assume the in situ generation of reactive allylindium(III) species through catalytic boron‐to‐indium transmetalation.  相似文献   
107.
108.
The inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82.1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, Lll103 (10-3) and Lll102 (KM) also exhibited higher inhibition percentages.  相似文献   
109.
Rhodococcus jostii RHA1 accumulates chlorobenzoates (CBA) during the degradation of polychlorinated biphenyls (PCBs). CBA degradation is considered one of the rate-limiting steps in the complete degradation of PCBs. To reduce the accumulation of CBAs, the upper pathway enzyme genes for PCB degradation of RHA1 were introduced into a CBA-degrading bacterium, Burkholderia sp. NK8. The resulting recombinant strain exhibited no biphenyl 2,3-dioxygenase (BphA) activity encoded by bphAaAbAcAd genes, which encode the large and small subunits of the terminal oxygenase component and the ferredoxin and reductase subunits responsible for electron transfer from NADH to the large subunit. The remaining enzyme genes involved in the transformation of biphenyl to benzoate, bphB2C1D1, which encode dehydrogenase, ring-cleavage dioxygenase and hydrolase, conferred activities to NK8. To obtain the BphA activity of RHA1 in NK8, sets of BphA genes were constructed by combining the bphAaAbAcAd genes of RHA1 and bphA3A4 of Pseudomonas pseudoalcaligenes KF707, encoding the ferredoxin and reductase subunits. Hybrid derivatives of BphA containing the KF707 bphA3 conferred BphA activity to NK8, and a derivative containing the RHA1 bphAaAb and KF707 bphA3A4 genes exhibited the highest BphA activity. A plasmid containing the RHA1 bphAaAb and KF707 bphA3A4 genes plus the RHA1 bphB2C1D1 genes was constructed and introduced into NK8. The resulting recombinant strain efficiently degraded 2-, 3- and 4-chlorobiphenyls with an apparent reduction in CBA accumulation in comparison to the recombinant mutant strain, which had an insertion in the cbeA gene to inactivate CBA dioxygenase.  相似文献   
110.
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