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   704篇
  免费   14篇
  国内免费   1篇
电工技术   14篇
化学工业   150篇
金属工艺   25篇
机械仪表   12篇
建筑科学   10篇
能源动力   43篇
轻工业   63篇
石油天然气   1篇
无线电   76篇
一般工业技术   89篇
冶金工业   193篇
原子能技术   9篇
自动化技术   34篇
  2022年   10篇
  2021年   16篇
  2020年   5篇
  2019年   8篇
  2018年   13篇
  2017年   6篇
  2016年   12篇
  2015年   5篇
  2014年   12篇
  2013年   38篇
  2012年   28篇
  2011年   34篇
  2010年   15篇
  2009年   30篇
  2008年   23篇
  2007年   24篇
  2006年   12篇
  2005年   9篇
  2004年   17篇
  2003年   15篇
  2002年   11篇
  2001年   17篇
  2000年   11篇
  1999年   18篇
  1998年   81篇
  1997年   43篇
  1996年   31篇
  1995年   23篇
  1994年   18篇
  1993年   19篇
  1992年   15篇
  1991年   12篇
  1990年   5篇
  1989年   3篇
  1988年   5篇
  1987年   10篇
  1986年   8篇
  1985年   7篇
  1984年   5篇
  1982年   4篇
  1980年   10篇
  1979年   3篇
  1978年   2篇
  1976年   14篇
  1975年   1篇
  1974年   3篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
  1965年   1篇
排序方式: 共有719条查询结果,搜索用时 546 毫秒
71.
72.
Post-translational modifications (PTMs) of serine and threonine occur by diverse mechanisms, including phosphorylation, sulfation, and various types of sugar chain modifications, making characterization of the resulting structures very labor-intensive. Moreover, to fully understand the biological functions of PTMs, both the sites of modification and the modified structures must be analyzed. The present work describes a novel, versatile strategy in which the released O-glycan and the formerly glycosylated/phosphorylated peptide are labeled and thus amenable to further study. In this approach, glycopeptides/phosphopeptides are subjected to β-elimination in the presence of pyrazolone derivatives (BEP), which in the same reaction labels the formerly glycosylated/phosphorylated peptide. The reaction is essentially a β-elimination/Michael addition in which a carbon-carbon bond-forming Michael donor rather than a heteroatomic Michael donor is used. The O-glycans released upon BEP are recovered as bis-pyrazolone derivatives, without any detectable side reaction (peeling). Using this technique, the O-glycan profiles of model mucin-type glycoproteins were successfully analyzed. The BEP strategy discriminates between phosphorylated and GlcNAcylated peptides, since cleaved GlcNAc is detectable. In addition, both the released O-glycan and the formerly glycosylated peptide can be selectively labeled by different reagents via a β-elimination reaction performed in the presence of pyrazolone and the thiol Michael donor.  相似文献   
73.
Investigation of pesticide residues in foods distributed in Kitakyushu City   总被引:2,自引:0,他引:2  
We investigated 160 kinds of pesticide residues in 715 samples of 116 kinds of foods distributed in Kitakyushu city. Sixty kinds of pesticides were detected in 55 kinds of foods (204 samples) in the range of 0.002-22 mg/kg. Five kinds of pesticides in 7 samples violated the residue standards and the indication of "unused". The detection ratios of unregulated pesticide in domestic and imported foods were 27.8 and 33.0%, respectively. Iprodione, dicofol, diethofencarb, procymidone and chlorfenapyr (for domestic food) and total bromine, benomyl, chlorpyrifos, dicofol, fenvalerate, cypermethrin and dimethoate (for imported food) showed relatively high detection ratios. Chinese cabbage, garland chrysanthemum, tomatoes and green teas (domestic) and broccoli, bananas, grapefruit, lemons, oranges, frozen edamame and frozen kidney beans (imported) showed high relative pesticide detection ratios. Residual pesticides were detected with relatively high frequency in imported fruits, imported frozen foods and imported processed foods.  相似文献   
74.
Recently a German appraisal instrument for clinical guidelines was published that could be used by various parties in formal evaluation of guidelines. An user's guide to the appraisal instrument was designed that contains a detailed explanation for each question to ensure that the instrument is interpreted consistently. This paper describes the purposes, format and contents of the user's guide, and reviews the key factors influencing the validity of guidelines. Taking into account international experiences, the purposes, chances and methodological limitations of a prospective assessment of clinical practice guidelines are discussed.  相似文献   
75.
We have recently demonstrated that the growth of murine macrophages is induced by oxidized low density lipoprotein (Ox-LDL) and that lysophosphatidylcholine (lyso-PC), a major phospholipid component of Ox-LDL, plays an essential role in its mitogenic effect. The present study was undertaken to further characterize the role of the macrophage scavenger receptor (MSR) in Ox-LDL-induced macrophage growth. The growth-stimulating effect of Ox-LDL on murine resident peritoneal macrophages was inhibited by maleylated bovine serum albumin (maleyl-BSA), a non-lipoprotein ligand for MSR but a poor carrier of lyso-PC, while maleyl-BSA itself failed to induce macrophage growth even in the presence of lyso-PC. Moreover, it competitively inhibited the endocytic uptake of 125I-Ox-LDL and the specific uptake of lyso-PC by MSR, whereas nonspecific lyso-PC transfer to cells was not affected. Furthermore, the Ox-LDL-induced cell growth of peritoneal macrophages obtained from MSR knockout mice was significantly weaker than that of macrophages obtained from their wild-type littermates. Our results suggest that the MSR is an important and efficient internalization pathway for lyso-PC in Ox-LDL-induced macrophage growth.  相似文献   
76.
We herein report an 83-year-old man who presented with a pleural tumor in the right thorax. The tumor was surgically resected and histopathologically diagnosed as ectopic primary pleural thymoma lacking any evidence of a mediastinal tumor. The clinicopathological aspects of this unusual thymoma are also discussed.  相似文献   
77.
The authors evaluated, using computer image analysis system, 15 renal biopsy specimens from patients with MCD and 15 from patients with FSGS. As a control group 5 biopsy and 10 autopsy renal specimens were used. These studies revealed, that in MCD glomeruli showed proliferative changes unrecognizable by light microscopy. In FSGS glomeruli without sclerotic changes were larger than in controls and showed glomerular cells proliferation (per unit of glomerular area) similar to MCD. FSGS in comparison with MCD showed larger glomeruli and prominent interstitial fibrosis. These observations appeared to be helpful in distinguishing MCD and recent forms of FSGS. There were no correlations between relative interstitial volume and glomerular changes in MCD as well as in FSGS. The authors concluded, that histomorphometry can't be used instead of morphological examinations of renal biopsy specimens, but it gives objective informations about progression of the illness and may be useful in differential diagnosis of selected cases of MCD and FSGS.  相似文献   
78.
Four mono-O-methylated and one mono-O-acetylated UDP-D-Gal analogues and UDP-L-Fuc were synthesized. 2-O-Methyl-D-galactose residue was enzymatically transferred to give 2'-O-methyllactosaminide in high yield. UDP-Fuc and UDP-Man showed potent inhibitory activities against beta-1,4-galactosyltransferase. Structural requirement and steric allowance for the ground and transition states of the enzyme reaction were discussed.  相似文献   
79.
80.
Neuronal nitric oxide synthase produces nitric oxide, a radical involved in neurotransmission as well as in cytotoxicity during stroke and neurodegenerative diseases. In the adult Wistar rat neuronal nitric oxide synthase-positive neurons are inhomogenously distributed along defined cortical areas, with highest densities (18 cells/mm2) in cingular area 1, piriform cortex, frontal motor area Fr 2 and in the medial visual association area Oc 2MM. A medium packing density of neuronal nitric oxide synthase neurons (10/mm2) characterizes primary sensory areas, whereas retrosplenial cortices contain lowest cell numbers (3-5/mm2). The data suggest that functions of certain cortical areas are more dependent on intracortically produced nitric oxide than others, and that cortical injury may cause more severe nitric oxide related cytotoxicity in areas with higher numbers of neuronal nitric oxide synthase-positive neurons.  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