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   27478篇
  免费   2892篇
  国内免费   1465篇
电工技术   1720篇
技术理论   2篇
综合类   1997篇
化学工业   4588篇
金属工艺   1611篇
机械仪表   1707篇
建筑科学   1964篇
矿业工程   685篇
能源动力   958篇
轻工业   2300篇
水利工程   594篇
石油天然气   1420篇
武器工业   193篇
无线电   3216篇
一般工业技术   3447篇
冶金工业   1124篇
原子能技术   343篇
自动化技术   3966篇
  2024年   163篇
  2023年   558篇
  2022年   916篇
  2021年   1182篇
  2020年   885篇
  2019年   842篇
  2018年   936篇
  2017年   922篇
  2016年   991篇
  2015年   1137篇
  2014年   1386篇
  2013年   1599篇
  2012年   1714篇
  2011年   1931篇
  2010年   1638篇
  2009年   1560篇
  2008年   1510篇
  2007年   1471篇
  2006年   1407篇
  2005年   1225篇
  2004年   923篇
  2003年   984篇
  2002年   1156篇
  2001年   1043篇
  2000年   707篇
  1999年   631篇
  1998年   406篇
  1997年   382篇
  1996年   363篇
  1995年   302篇
  1994年   200篇
  1993年   160篇
  1992年   145篇
  1991年   98篇
  1990年   71篇
  1989年   57篇
  1988年   52篇
  1987年   41篇
  1986年   34篇
  1985年   16篇
  1984年   13篇
  1983年   9篇
  1982年   13篇
  1981年   8篇
  1980年   11篇
  1979年   9篇
  1976年   3篇
  1975年   3篇
  1974年   6篇
  1973年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
珍珠贝肉蛋白饮料的研制   总被引:2,自引:0,他引:2  
研究了用马氏珠母贝肉水解液制作蛋白饮料的工艺。结果表明:采用枯草杆菌中性酶和胃蛋白酶复合水解,蛋白质水解率可达66.2%。水解液经脱腥、脱色处理,再用山楂、红枣、白砂糖进行调配,制成营养丰富,具有一定保健功能的蛋白饮料。  相似文献   
992.
Changes in β-glycosidase activity, total phenolic and isoflavone contents, and antioxidant activities during the fermentation of brown soybeans (Galmi) fermented food cheonggukjang by the potential probiotic Bacillus subtilis CSY191 were investigated. The total phenolic and isoflavone-glycoside and -aglycone contents as well as ABTS radical scavenging activity and FRAP assays of extracts increased, but malonylglycoside content decreased after a steaming process. It was found that fermentation enhanced the total phenolic and isoflavone-aglycone and -malonylglycoside contents, corresponding to antioxidant activities increased, but isoflavone-glycoside content decreased. The highest levels of daidzein, glycitein, and gensitein were present at concentrations of 156.5 μg/g, 10.2 μg/g, and 2.5 μg/g after 48 h of fermentation. In addition, ABTS radical scavenging activity and FRAP assay increased significantly during fermentation. We suggest that the high antioxidant activity of cheonggukjang of brown soybeans might be related to the markedly higher levels of total phenolic content and isoflavone-aglycones achieved during fermentation.  相似文献   
993.
In addition to cellulose and lignin, hemicellulose is an important biomass material. Recently, hemicellulose and its derivatives and materials have attracted increasing attention owing to their unique structures, improved properties, and promising application potential, and many reports on the extraction, isolation, and modification of hemicellulose are currently available. We summarized the recent developments of hemicellulose and its derivatives and materials by focusing on the extraction, purification, and modification of hemicellulose. The synthesis of hemicellulose-based derivatives and materials was also reviewed. Various methods of extracting, isolating, and modifying hemicellulose were discussed. Remaining challenges related to hemicellulose extraction, purification, and application were mentioned, and directions for further research on hemicellulose were proposed.  相似文献   
994.
朱安妮  唐俊妮  赵燕英  汤承  陈娟  刘骥 《食品科学》2016,37(16):193-198
目的:建立简便、灵敏检测金黄色葡萄球菌肠毒素I(staphylococcal enterotoxin I,SEI)的双抗夹心酶联免疫吸附方法(double-antibody sandwich-enzyme linked immunosorbent assay,DAS-ELISA)。方法:利用DAS-ELISA检测程序确定单克隆抗体、抗血清、辣根过氧化物酶(horseradish peroxidase,HRP)标记的羊抗兔IgG(IgG/HRP)的最佳稀释度,再通过检测不同包被缓冲液、封闭时间、抗原包被时间、IgG/HRP作用时间以及四甲基联苯胺(3,3’,5,5’-tetramethylbenzidine,TMB)显色时间条件下的OD450 nm值对实验条件进行优化,最后用灵敏度、批内变异、批间变异和加标回收率指标对方法进行评价。结果:抗SEI单克隆抗体的最佳稀释质量浓度为2.89 mg/L,抗SEI兔血清稀释度1∶2 000,酶标二抗稀释度1∶6 000;1×磷酸缓冲盐溶液(pH 7.4)为最佳包被缓冲液;最佳封闭时间、抗原孵育时间、酶标二抗孵育时间和TMB显色时间分别为60、90、30 min和15 min。该方法的回归方程为y=0.040 9x+0.042 9,R2=0.993 3;灵敏度为0.5 μg/L,精密度批内变异低于10%,批间变异低于15%,除巴氏杀菌牛乳外,对生理盐水、熟牦牛肉糜、大米饭和超高温瞬时灭菌牛乳回收率达90%以上。结论:本研究建立了一种快速检测SEI的双抗夹心方法。  相似文献   
995.
以红树莓为原料,采用超声辅助法并结合单因素和正交试验优化花色苷的提取工艺,在此基础上,优化AB-8型大孔树脂纯化花色苷的工艺,并研究其抑菌活性。结果表明:红树莓花色苷最佳提取工艺为乙醇提取剂浓度90%、pH4.0、温度 30℃、时间 150 min、料液比 1∶10(g/mL),花色苷提取率高达 1.15 mg/g。最佳纯化工艺为上样液 pH2.0、静态吸附时间150 min、乙醇洗脱剂浓度90%、洗脱剂pH2.0、解吸时间30 min,纯化后花色苷纯度显著提高到纯化前的1.68倍;纯化后的花色苷对大肠杆菌(Escherichia coli)和金黄色葡萄球菌(Staphylococcus aureus)具有明显的抑制生长作用,而对啤酒酵母(Saccharomycete cerevisiae)及黑曲霉(Aspergillus niger)则无抑制作用。  相似文献   
996.
目的 对保健食品中的污染菌进行分离和鉴定。方法 按照GB 4789《食品安全国家标准 食品微生物学检验》对31批次保健食品进行检验, 采用全自动细菌鉴定系统对污染菌进行鉴定。结果 从31批次的保健食品中分离、鉴定出64株污染菌, 在沙门氏菌、志贺氏菌、金黄色葡萄球菌和溶血性链球菌的检验中未检出目的菌, 但分离得到致病菌和条件致病菌, 分别是阴沟肠杆菌、肺炎克雷伯菌、气味沙雷菌、温和气单胞菌、赫氏埃希菌、阪崎肠杆菌、非脱羧勒菌、泛菌属、缓慢葡萄球菌、浅绿气球菌、哥伦比亚肠球菌、腐生葡萄球菌、产色葡萄球菌、溶血葡萄球菌、铅黄肠球菌、屎肠球菌、以及枯草/解淀粉/萎缩芽孢杆菌、死谷芽孢杆菌、短小芽孢杆菌、凝结芽孢杆菌以及蜡样/苏云金/蕈状芽孢杆菌。结论 各种致病菌及条件致病菌的检出, 对消费者健康存在潜在的风险。通过分析污染菌的来源及危害, 提出提高保健食品卫生质量的建议, 为保健食品的生产、消毒灭菌、卫生学检验及监督管理等方面提供参考。  相似文献   
997.
Illumination of noble metal nanoparticles at the plasmon resonance causes substantial heat generation, and the transient and highly localized temperature increases that result from this energy conversion can be exploited for photothermal therapy by plasmonically heating gold nanorods (NRs) bound to cell surfaces. Here, plasmonic heating is used for the first time to locally release silver from gold core/silver shell (Au@Ag) NRs targeted to bacterial cell walls. A novel biomimetic method of preparing Au@Ag core–shell NRs is employed, involving deposition of a thin organic polydopamine (PD) primer onto Au NR surfaces, followed by spontaneous electroless silver metallization, and conjugation of antibacterial antibodies and passivating polymers for targeting to gram‐negative and gram‐positive bacteria. Dramatic cytotoxicity of S. epidermidis and E. coli cells targeted with Au@Ag NRs is observed upon exposure to light as a result of the combined antibacterial effects of plasmonic heating and silver release. The antibacterial effect is much greater than with either plasmonic heating or silver alone, implying a strong therapeutic synergy between cell‐targeted plasmonic heating and the associated silver release upon irradiation. The findings suggest a potential antibacterial use of Au@Ag NRs when coupled with light irradiation, which has not been previously described.  相似文献   
998.
The evaporation-induced self-assembly method using a novel diblock (poly(ethylene-co-butylene)-b-poly(ethylene oxide)) copolymer (KLE) provides fully crystalline mesoporous layers of TiO2 exhibiting high thermal stability up to 700 °C, high photocatalytic activity in the decomposition of methyl stearate and facile transformation into a substantially stable superhydrophilic state by 1 mW/cm2 UV-illumination.  相似文献   
999.
The charge transfer within heterojunction is crucial for the efficiency and stability of photocatalyst for overall water splitting (OWS). Herein, InVO4 nanosheets have been employed as a support for the lateral epitaxial growth of ZnIn2S4 nanosheets to produce hierarchical InVO4@ZnIn2S4 (InVZ) heterojunctions. The distinct branching heterostructure facilitates active site exposure and mass transfer, further boosting the participation of ZnIn2S4 and InVO4 for proton reduction and water oxidation, respectively. The unique Z-scheme modulated charge transfer, visualized by simulation and in situ analysis, has been proved to promote the spatial separation of photoexcited charges and strengthen the anti-photocorrosion capability of InVZ. The optimized InVZ heterojunction presents improved OWS (153.3 µmol h−1 g−1 for H2 and 76.9 µmol h−1 g−1 for O2) and competitive H2 production (21090 µmol h−1 g−1). Even after 20 times (100 h) of cycle experiment, it still holds more than 88% OWS activity and a complete structure.  相似文献   
1000.
Flexible pressure sensors play an indispensable role in flexible electronics. Microstructures on flexible electrodes have been proven to be effective in improving the sensitivity of pressure sensors. However, it remains a challenge to develop such microstructured flexible electrodes in a convenient way. Inspired by splashed particles from laser processing, herein, a method for customizing microstructured flexible electrodes by femtosecond laser-activated metal deposition is proposed. It takes advantage of the catalyzing particles scattered during femtosecond laser ablation and is particularly suitable for moldless, maskless, and low-cost fabrication of microstructured metal layers on polydimethylsiloxane (PDMS). Robust bonding at the PDMS/Cu interface is evidenced by the scotch tape test and the duration test over 10 000 bending cycles. Benefiting from the firm interface, the developed flexible capacitive pressure sensor with microstructured electrodes presents several conspicuous features, including a sensitivity (0.22 kPa−1) 73 times higher than the one using flat Cu electrodes, ultralow detection limit (<1 Pa), rapid response/recovery time (4.2/5.3 ms), and excellent stability. Moreover, the proposed method, inheriting the merits of laser direct writing, is capable of fabricating a pressure sensor array in a maskless manner for spatial pressure mapping.  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