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   732831篇
  免费   66584篇
  国内免费   38371篇
电工技术   50879篇
技术理论   66篇
综合类   57508篇
化学工业   112305篇
金属工艺   42174篇
机械仪表   48007篇
建筑科学   61605篇
矿业工程   23754篇
能源动力   20648篇
轻工业   53892篇
水利工程   16126篇
石油天然气   41228篇
武器工业   7146篇
无线电   82745篇
一般工业技术   75514篇
冶金工业   34507篇
原子能技术   7935篇
自动化技术   101747篇
  2024年   3249篇
  2023年   11021篇
  2022年   21594篇
  2021年   29256篇
  2020年   22102篇
  2019年   17363篇
  2018年   19817篇
  2017年   22766篇
  2016年   20493篇
  2015年   29346篇
  2014年   37483篇
  2013年   44133篇
  2012年   49848篇
  2011年   53870篇
  2010年   48781篇
  2009年   46287篇
  2008年   46013篇
  2007年   43606篇
  2006年   42851篇
  2005年   35972篇
  2004年   25442篇
  2003年   22887篇
  2002年   23088篇
  2001年   20284篇
  2000年   17286篇
  1999年   16531篇
  1998年   12235篇
  1997年   10324篇
  1996年   9649篇
  1995年   7916篇
  1994年   6599篇
  1993年   4487篇
  1992年   3540篇
  1991年   2679篇
  1990年   2095篇
  1989年   1692篇
  1988年   1419篇
  1987年   912篇
  1986年   711篇
  1985年   435篇
  1984年   321篇
  1983年   242篇
  1982年   250篇
  1981年   191篇
  1980年   216篇
  1979年   118篇
  1978年   37篇
  1977年   38篇
  1976年   53篇
  1951年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
This study investigated the inhibitory effects of curcumin and piperine on fluorescent advanced glycation end products (fAGEs) formation in a bovine serum albumin (BSA)–fructose model. Model systems of BSA and fructose were prepared, and curcumin or piperine was added. fAGEs and BSA oxidation product (dityrosine, kynurenine and N'-formylkynurenine) contents were determined. The results showed that fAGEs content decreased with increasing concentration of curcumin and piperine (P < 0.05). Addition of curcumin and piperine at 160 µg mL−1 could inhibit fluorescent AGEs by 100% and 93% respectively. Dityrosine and N'-formylkynurenine contents decreased as curcumin and piperine concentration increased (P < 0.05). Furthermore, the result of principal component analysis indicated that curcumin and piperine markedly impeded BSA oxidation, resulting in a lower level of fAGEs in model systems. Therefore, adding curcumin and piperine may facilitate reduced fAGEs levels in BSA–fructose model.  相似文献   
22.
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin.  相似文献   
23.
Ceramic microparticles have great potentials in various fields such as materials engineering, biotechnology, microelectromechanical systems, etc. Morphology of the microparticle performs an important role on their application. To date, it remains difficult to find an effective and controllable way for fabricating nonspherical ceramic microparticles with 3D features. This work demonstrates a method that combines UV light lithography and single emulsion opaque-droplet-templated microfluidic molding to prepare the crescent-shaped ceramic microparticles. By tailoring the intensity of UV light and flow rate of fluid, the shapes of microparticles are accordingly tuned. Therefore, varieties of crescent-shaped microparticles and their variations have been fabricated. After sintering, the crescent-shaped alumina ceramic microparticles were obtained. Benefitting from the light absorption and scattering behavior of most ceramic nanoparticles, this system can serve as a general platform to produce crescent-shaped microparticles made from different materials, and hold great potentials for applications in microrobotics, structural materials in MEMS, and biotechnology.  相似文献   
24.
纳米药物非临床药代动力学的研究策略及关注要点   总被引:1,自引:0,他引:1  
随着纳米技术的迅速发展,纳米药物的研发已成为目前药物创新的发展方向之一。纳米药物具有基于纳米结构的尺度效应,其药代动力学特征与普通药物相比存在明显差异,其药代动力学研究与普通药物相比也有其特殊性。本文着重探讨纳米药物的非临床药代动力学的研究策略及关注要点,包括受试物、体内/外试验、生物样本分析、数据评价分析等,期望为研发者提供参考。  相似文献   
25.
26.
International Journal of Speech Technology - With the development of multimedia technology and network technology applications, it is possible to implement online teaching systems in schools. This...  相似文献   
27.
有机-无机压电材料是一种分子铁电体,具有柔性、结构灵活、易成膜、全液相合成及环保节能等优点,可满足新一代薄膜器件及可穿戴设备的需求。该文以三甲基卤代甲基铵(TMXM, X=F, Cl, Br)为有机部分,MnCl2为无机部分,通过溶液蒸发法制备了具有钙钛矿分子结构的有机-无机压电材料三甲基氯三氯化锰(TMCM-MnCl3),并对其分子结构组成、压电、热学、声学及铁电性进行表征。结果表明,TMCM-MnCl3的压电常数为106 pC/N,居里温度为130 ℃,声阻抗值约为16.5 MRayl,低于压电陶瓷PZT-4(大于33 MRayl),具有广阔的应用前景。  相似文献   
28.
29.
30.
Wang  Chen  Bao  Chun-Hui  Wu  Wan-Yu  Hsu  Chia-Hsun  Zhao  Ming-Jie  Zhang  Xiao-Ying  Lien  Shui-Yang  Zhu  Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate...  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