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   128015篇
  免费   12374篇
  国内免费   6852篇
电工技术   8770篇
技术理论   9篇
综合类   10036篇
化学工业   20215篇
金属工艺   7241篇
机械仪表   8240篇
建筑科学   10604篇
矿业工程   3902篇
能源动力   3508篇
轻工业   10623篇
水利工程   2853篇
石油天然气   6892篇
武器工业   1230篇
无线电   14177篇
一般工业技术   14217篇
冶金工业   5671篇
原子能技术   1658篇
自动化技术   17395篇
  2024年   625篇
  2023年   2247篇
  2022年   4246篇
  2021年   5653篇
  2020年   4319篇
  2019年   3465篇
  2018年   3899篇
  2017年   4435篇
  2016年   3925篇
  2015年   5338篇
  2014年   7118篇
  2013年   8162篇
  2012年   9254篇
  2011年   9738篇
  2010年   8911篇
  2009年   8286篇
  2008年   8091篇
  2007年   7834篇
  2006年   7243篇
  2005年   6052篇
  2004年   4211篇
  2003年   3368篇
  2002年   3045篇
  2001年   2711篇
  2000年   2674篇
  1999年   2514篇
  1998年   1762篇
  1997年   1526篇
  1996年   1367篇
  1995年   1187篇
  1994年   957篇
  1993年   705篇
  1992年   540篇
  1991年   422篇
  1990年   364篇
  1989年   286篇
  1988年   220篇
  1987年   126篇
  1986年   122篇
  1985年   67篇
  1984年   56篇
  1983年   31篇
  1982年   38篇
  1981年   34篇
  1980年   32篇
  1979年   11篇
  1977年   2篇
  1976年   2篇
  1959年   9篇
  1951年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
为了响应"全员育人、全程育人、全方位育人"三全育人的重要举措,以及体现专业课程在立德树人方面的重要作用和对生物化工专业的认同,文中旨将专业知识与社会主义核心价值观有机的融合,润物细无声的对学生进行思政教育,积极探索微生物学实验中能够与思政元素相融合的切入点,一方面激发了学生的学习兴趣和自学潜能,提升了课堂教学效果和效率,另一方面达成了生物化工行业对高质量人才的需求.  相似文献   
42.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency.  相似文献   
43.
Cancer remains an intractable medical problem. Rapid diagnosis and identification of cancer are critical to differentiate it from nonmalignant diseases. High-throughput biofluid metabolic analysis has potential for cancer diagnosis. Nevertheless, the present metabolite analysis method does not meet the demand for high-throughput screening of diseases. Herein, a high-throughput, cost-effective, and noninvasive urine metabolic profiling method based on TiO2/MXene-assisted laser desorption/ionization mass spectrometry (LDI-MS) is presented for the efficient screening of bladder cancer (BC) and nonmalignant urinary disease. Combined with machine learning, TiO2/MXene-assisted LDI-MS enables high diagnostic accuracy (96.8%) for the classification of patient groups (including 47 BC and 46 ureteral calculus (UC) patients) from healthy controls (113 cases). In addition, BC patients can also be identified from noncancerous UC individuals with an accuracy of 88.3% in the independent test cohort. Furthermore, metabolite variations between BC and UC individuals are investigated based on relative quantification, and related pathways are also discussed. These results suggest that this method, based on urine metabolic patterns, provides a potential tool for rapidly distinguishing urinary diseases and it may pave the way for precision medicine.  相似文献   
44.
0.5 at.% Cr:ZnGa2O4 precursor was synthesized by the co-precipitation method with nitrates as raw materials, using ammonium carbonate as the precipitant. Low-agglomerated Cr:ZnGa2O4 powders with an average particle size of 43 nm were obtained by calcining the precursor at 900℃ for 4 h. Using the powders as starting materials, 0.5 at.% Cr:ZnGa2O4 ceramics with an average grain size of about 515 nm were prepared by presintering at 1150℃ for 5 h in air and HIP post-treatment at 1100℃ for 3 h under 200 MPa Ar. The in-line transmittance of 0.5 at.% Cr:ZnGa2O4 ceramics with a thickness of 1.3 mm reaches 59.5% at the wavelength of 700 nm. The Cr:ZnGa2O4 ceramics can be effectively excited by visible light and produce persistent luminescence at 700 nm. For Cr:ZnGa2O4 transparent ceramics, the brightness of afterglow was larger than 0.32 mcd/m2 after 30 min, which is far superior to that of Cr:ZnGa2O4 persistent luminescence powders.  相似文献   
45.
Element doping into the Cu2ZnSn(S,Se)4 (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu2InxZn1-xSn(S,Se)4 (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu2ZnSnS4 (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (PIn). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In3+ into the main lattice of CZTSSe. The partial Zn2+ cations were substituted by In3+ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the PIn was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as PIn increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at PIn = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm2V?1s?1, which is a potential material as the absorption layer of high-performance solar cells.  相似文献   
46.
The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo2C/CeO2 catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce3+ and surface oxygen species. The presence of Mo2C and CeO2 overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO2 catalyst prepared without carbonization, the Mo2C/CeO2 catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis.  相似文献   
47.
Zu  Guoqing  Lu  Yukuan  Yan  Yi  Zhang  Xiaoming  Zhao  Jingwei  Du  Wei  Ran  Xu  Jiang  Zhengyi 《Metals and Materials International》2020,26(2):248-259
Metals and Materials International - The flow behaviour and microstructure characteristics of a ferritic stainless steel were investigated using plain strain compression test on a Gleeble 3500...  相似文献   
48.
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved.  相似文献   
49.
Glyco‐mimicking nanoparticles (glyco‐NPs) with Förster resonance energy transfer (FRET) donor and acceptor groups formed via dynamic covalent bond of benzoboroxole and sugar from two complementary polymers are prepared. The glyco‐NPs are proved to be quite stable under physiological conditions but sensitive to pH. So the glyco‐NPs can be internalized by dendritic cells with integrity and nontoxicity and then dissociate within the acidic organelles. This particle dissociation is directly observed and visualized in vitro, for the first time via the FRET measurements and fluorescent microscopy. This feature makes controlled release of drug or protein by glyco‐NPs possible, i.e., when model antigen Ovalbumin is loaded in the glyco‐NPs, the released Ovalbumin in dendritic cells stimulates T cells more efficiently than the free Ovalbumin itself as a result of the enhanced antigen processing and presentation. Thus, the results enlighten a bright future of the glyco‐NPs in immunotherapy.  相似文献   
50.
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