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   1390篇
  免费   5篇
电工技术   3篇
化学工业   36篇
金属工艺   11篇
机械仪表   11篇
建筑科学   12篇
能源动力   3篇
轻工业   17篇
无线电   35篇
一般工业技术   63篇
冶金工业   1177篇
原子能技术   4篇
自动化技术   23篇
  2022年   3篇
  2021年   2篇
  2020年   2篇
  2018年   5篇
  2016年   4篇
  2015年   2篇
  2014年   6篇
  2013年   10篇
  2012年   10篇
  2011年   9篇
  2010年   6篇
  2009年   4篇
  2008年   11篇
  2007年   8篇
  2006年   8篇
  2005年   6篇
  2004年   5篇
  2003年   7篇
  2002年   3篇
  2001年   5篇
  1999年   36篇
  1998年   381篇
  1997年   192篇
  1996年   155篇
  1995年   87篇
  1994年   65篇
  1993年   73篇
  1992年   12篇
  1991年   21篇
  1990年   11篇
  1989年   17篇
  1988年   17篇
  1987年   12篇
  1986年   12篇
  1985年   10篇
  1984年   2篇
  1983年   2篇
  1982年   12篇
  1981年   15篇
  1980年   10篇
  1979年   3篇
  1978年   7篇
  1977年   39篇
  1976年   66篇
  1974年   3篇
  1973年   6篇
  1971年   2篇
  1970年   3篇
  1966年   1篇
  1964年   1篇
排序方式: 共有1395条查询结果,搜索用时 15 毫秒
11.
Enzyme(s) capable of decomposing N-acetylglucosaminyl ribitol teichoic acid prepared from the cell wall of Staphylococcus aureus FDA 209 P was obtained from the culture supernatant of a gram-negative, rod-shaped, spore-forming soil bacterium. Properties of the bacterium were very similar to those of Bacillus circulans.  相似文献   
12.
A surgical technique for secondary emplacement of an orbital implant is described in which a spherical implant encased in a scleral homograft is placed in the orbit through a transconjuctival incision and sutured to the superior part of the periosteum.  相似文献   
13.
Cholecystostomy     
The role of cholecystostomy in the sugical treatment of gallstones has been considered. In a consecutive series of 558 patients who underwent surgery for gallstones, 30 (5-4 per cent) had cholecystostomy alone and a further 17 (3-1 per cent) cholecystostomy combined with exploration of the bile ducts. Cholecystostomy was done because cholecystectomy was technically very hazardous in 15 patients. In the remaining patients cholecystostomy was preferred to cholecystectomy because o f the poor general condition of the patient or the presence of pancreatitis. Of the 47 patients submitted to cholecystostomy, 2(4-2 per cent) died postoeratively and 4(8-4 percent) subsequently underwent cholecystectomy. Of 24 patients who were available for long term follow-up, only 1 patient had pain which was definitely considered to be due to gallstones, although 3 other patients also had abdominal pain, while 7 patients showed radiological evidience of gallstones. It is contended that cholecystostomy has a small but definite part to play in the immediate surgical treatment of gallstones and that the long term results of the operation are sufficiently good to justify its use in selected patients.  相似文献   
14.
Ethanol extracts of Chardonnay grape and black raspberry seed flours were evaluated for their capacity to suppress lipid oxidation, preserve important fatty acids, and inhibit microbial growth. They were also tested for radical scavenging activity against DPPH and peroxyl radicals as reflected in oxygen radical absorbance capacity (ORAC), and total phenolic content (TPC). Both tested seed flour extracts suppressed lipid oxidation and rancidity development in fish oil. Black raspberry seed flour extract significantly reduced the degradation of biologically important n − 3 PUFA under accelerated oxidative conditions. Black raspberry and Chardonnay seed flour extracts at 165 and 160 μg seed flour equivalents/mL, respectively exhibited bacteriocidal activity against Escherichia coli and growth inhibition of Listeria monocytogenes under experimental conditions. Both seed flour extracts exhibited DPPH radical quenching activity and Chardonnay had the stronger ORAC of 663 μmol Trolox equivalents per gram seed flour and the higher TPC of 99 mg gallic acid equivalents/g flour. The data from this study suggest the potential for developing natural food preservatives from these seed flours for improving food stability, quality, safety, and consumer acceptance.  相似文献   
15.
S.J. Radcliffe  A.A. Parry 《Wear》1979,56(1):203-212
Solid lubricant coatings usually fail quite suddenly and thus, for a given specimen, a well-defined life can be measured. Failure may be caused by a number of physical processes, e.g. wearing through the coating, loss of adhesion to the substrate or fatigue. Wear tests of 70 specimens with similarly loaded MoS2 coatings are analysed. The coating life (in cycles) was in general proportional to the thickness and inversely proportional to the load and amplitude, but there was considerable scatter. The results could be expressed in terms of a specific wear rate fitting a mixed Weibull distribution.  相似文献   
16.
Coral reefs are in global decline, with seaweeds increasing as corals decrease. Although seaweeds inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly understood. Here, we used field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting seaweed effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, neurymenolide A, as the main allelopathic agent. For allelopathy of lipid-soluble metabolites to be effective, the compounds would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify neurymenolide A on the surface of P. neurymenioides, and we found the molecule on all surfaces analyzed, with highest concentrations on basal portions of blades.  相似文献   
17.
We report the heterologous expression, structure, and antimicrobial activity of a lasso peptide, ubonodin, encoded in the genome of Burkholderia ubonensis. The topology of ubonodin is unprecedented amongst lasso peptides, with 18 of its 28 amino acids found in the mechanically bonded loop segment. Ubonodin inhibits RNA polymerase in vitro and has potent antimicrobial activity against several pathogenic members of the Burkholderia genus, most notably B. cepacia and B. multivorans, causative agents of lung infections in cystic fibrosis patients.  相似文献   
18.
Cold-pressed seed flours from pumpkin, parsley, mullein, cardamom, and milk thistle were examined for total oil, fatty acid profile of the oil, total phenolic content (TPC), scavenging activities against peroxyl (ORAC), hydroxyl (HOSC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (RDSC) radicals, and antiproliferative capacity against HT-29 human colon cancer cells. The cold-pressed parsley seed flour contained a very high concentration of total oil—17.6 g/100 g flour—with primarily C18:1 fatty acid at 86.2 g/100 g fatty acids. All other flour oils had relatively high levels of saturated fats, ranging from 39.0 to 62.9 g/100 g fatty acids. The tested seed flours demonstrated significant TPC and free radical scavenging activities. Milk thistle seed flour had the highest TPC value of 25.2 mg gallic acid equivalent per g flour (GAE mg/g) followed by that of parsley seed flour at 8.1 GAE mg/g. Milk thistle seed-flour extract also had significantly higher antioxidant activities than all other extracts against all tested radicals. The milk thistle seed-flour extract had an ORAC value of 1131 μmol trolox equivalents (TE) per g flour (TE μmol/g), a HOSC value of 893 TE μmol/g, and an RDSC value of 61 TE μmol/g. Also, ORAC, HOSC, and TPC values were significantly correlated (P < 0.01) under the experimental conditions. The cold-pressed milk thistle seed flour inhibited the proliferation of HT-29 cancer cells in a dose-dependent manner. Results from this study suggest that these cold-pressed seed flours may serve as natural sources of antioxidants and may be used to improve human health.  相似文献   
19.
Nitrogen (N) and phosphorus (P) co-doped anatase TiO2 nanosheets were realized by low-temperature self-doping N–TiO2 followed by high-temperature P doping with foreign precursor. It is found that P doping process can maintain good TiO2 nanosheets morphology with exposed {001} facets. Chemical state of dopants indicates that N and P atoms replace O on O sites in TiO2 lattice. Compared with pure TiO2 and N-doped TiO2, N–P co-doped TiO2 nanosheets exhibits stronger optical absorption and higher degradation rate of dye molecules in visible light regime. The enhanced photocatalytic properties are attributed to two factors. On one hand, N–P co-doping can effectively reduce band gap of TiO2 from 3.20 to 2.48 eV, leading to an enhancement of the absorption in visible light regime. On the other hand, the presence of exposed {001} facets of TiO2 nanosheets can induce the effective separation of photogenerated electrons and holes in reaction.  相似文献   
20.
Despite structured enforcement of food hygiene requirements known to prevent foodborne disease outbreaks, catering businesses continue to be the most common setting for outbreaks in the United Kingdom. In a matched case control study of catering businesses, 148 businesses associated with outbreaks were compared with 148 control businesses. Hazard analysis critical control point systems and/or formal food hygiene training qualifications were not protective. Food hygiene inspection scores were not useful in predicting which catering businesses were associated with outbreaks. Businesses associated with outbreaks were more likely to be larger small and medium-sized enterprises (SMEs) or to serve Chinese cuisine and less likely to have the owner or manager working in the kitchen, but when size of the SME was taken into account these two differences were no longer significant. In larger businesses, case businesses were more likely to be hotels and were more commonly associated with viral foodborne outbreaks, but there was no explanation within the data for this association.  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