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   19050篇
  免费   828篇
  国内免费   139篇
电工技术   324篇
综合类   32篇
化学工业   4231篇
金属工艺   589篇
机械仪表   628篇
建筑科学   370篇
矿业工程   48篇
能源动力   1364篇
轻工业   1156篇
水利工程   152篇
石油天然气   84篇
武器工业   1篇
无线电   2355篇
一般工业技术   4317篇
冶金工业   1437篇
原子能技术   172篇
自动化技术   2757篇
  2024年   101篇
  2023年   418篇
  2022年   995篇
  2021年   1156篇
  2020年   910篇
  2019年   938篇
  2018年   1214篇
  2017年   955篇
  2016年   924篇
  2015年   602篇
  2014年   842篇
  2013年   1513篇
  2012年   888篇
  2011年   1065篇
  2010年   853篇
  2009年   805篇
  2008年   710篇
  2007年   573篇
  2006年   474篇
  2005年   361篇
  2004年   272篇
  2003年   241篇
  2002年   188篇
  2001年   177篇
  2000年   169篇
  1999年   168篇
  1998年   291篇
  1997年   238篇
  1996年   219篇
  1995年   168篇
  1994年   157篇
  1993年   151篇
  1992年   103篇
  1991年   130篇
  1990年   99篇
  1989年   95篇
  1988年   79篇
  1987年   89篇
  1986年   76篇
  1985年   85篇
  1984年   73篇
  1983年   72篇
  1982年   61篇
  1981年   70篇
  1980年   48篇
  1979年   31篇
  1978年   27篇
  1977年   26篇
  1976年   35篇
  1971年   12篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
In this study, we have introduced newly synthesized substituted benzothiazole based berberine derivatives that have been analyzed for their in vitro and in silico biological properties. The activity towards various kinds of influenza virus strains by employing the cytopathic effect (CPE) and sulforhodamine B (SRB) assay. Several berberine–benzothiazole derivatives (BBDs), such as BBD1, BBD3, BBD4, BBD5, BBD7, and BBD11, demonstrated interesting anti-influenza virus activity on influenza A viruses (A/PR/8/34, A/Vic/3/75) and influenza B viral (B/Lee/40, and B/Maryland/1/59) strain, respectively. Furthermore, by testing neuraminidase activity (NA) with the neuraminidase assay kit, it was identified that BBD7 has potent neuraminidase activity. The molecular docking analysis further suggests that the BBD1–BBD14 compounds’ antiviral activity may be because of interaction with residues of NA, and the same as in oseltamivir.  相似文献   
112.
Silicon - In the present report, a photonic crystal based micro-ring resonator (MRR) structure is proposed which is very compact in size and has very fast response and is employed for temperature...  相似文献   
113.
Silicon - The primary purpose of this work is to study the effect of symmetric and asymmetric variation of underlap regions both on source and drain side of 3D SOI n-FinFET. Underlap length is...  相似文献   
114.
Reddy  N. Nagendra  Panda  Deepak Kumar 《SILICON》2021,13(12):4545-4551
Silicon - In this paper, a dielectric modulated dual material gate TFET (DM-DMG_TFET)based biosensor is proposed. In order to detect various biomolecules, a nanogap cavity is formed by the...  相似文献   
115.
Solay  Leo Raj  Singh  Sarabdeep  Kumar  Naveen  Amin  S. Intekhab  Anand  Sunny 《SILICON》2021,13(12):4633-4640
Silicon - In this treatise, we have proposed a Single Material Gate–Dual Gate Impact Ionization Metal Oxide Semiconductor (SMG DG-IMOS) based Pressure Sensor. The pressure sensor has the most...  相似文献   
116.

A temperature sensor based on photonic crystal structures with two- and three-dimensional geometries is proposed, and its measurement performance is estimated using a machine learning technique. The temperature characteristics of the photonic crystal structures are studied by mathematical modeling. The physics of the structure is investigated based on the effective electrical permittivity of the substrate (silicon) and column (air) materials for a signal at 1200 nm, whereas the mathematical principle of its operation is studied using the plane-wave expansion method. Moreover, the intrinsic characteristics are investigated based on the absorption and reflection losses as frequently considered for such photonic structures. The output signal (transmitted energy) passing through the structures determines the magnitude of the corresponding temperature variation. Furthermore, the numerical interpretation indicates that the output signal varies nonlinearly with temperature for both the two- and three-dimensional photonic structures. The relation between the transmitted energy and the temperature is found through polynomial-regression-based machine learning techniques. Moreover, rigorous mathematical computations indicate that a second-order polynomial regression could be an appropriate candidate to establish this relation. Polynomial regression is implemented using the Numpy and Scikit-learn library on the Google Colab platform.

  相似文献   
117.

The quantum-dot cellular automata (QCA) is considered to be one of the ground-breaking nanotechnologies developed over the last two decades. A layered T (LT) logic cell library is constructed herein, and the methodology is extended to generic adder and subtractor module designs. The two proposed algorithms lead to more efficient QCA layout designs for an n-bit ripple carry adder (RCA) and subtractor based on an effective clock zone assignment approach. The suggested one-, four-, and eight-bit RCAs and subtractors surpass most of their existing counterparts by offering lower effective area and cell complexity. A comparative analysis is presented regarding the complexity, irreversible power dissipation, and Costα of the proposed n-bit layouts from a cost estimation purview.

  相似文献   
118.

High nitrogen steels provide excellent mechanical properties and corrosion resistance but are prone to form precipitates which adversely affect the corrosion resistance and toughness. High nitrogen steel powders currently available in the market are not claimed to be precipitate free. It is critical to avoid these precipitates while retaining nitrogen in the dissolved form to realize the value of these powder alloys. However, retaining high level of dissolved nitrogen in steel powder during melt atomization process is very challenging. Instead, solid-state dissolution of nitrogen into the powder alloy followed by rapid cooling may provide a convenient approach to avoid precipitate formation compared to traditional melt processing. This study presents a solution treatment approach to achieve elevated dissolved nitrogen levels (~ 0.4 wt pct) in Fe–Mn–Cr powder alloy with negligible precipitation of nitrides. The influence of starting material, holding time, temperature and cooling rate on the resulting microstructure is presented. A fully austenite matrix with high dissolved nitrogen content resulted in powders with desired mechanical properties.

  相似文献   
119.
The fracture strength of HF-etched samples was measured as a function of field-assisted K-Na ion exchange depth, as well as the severity of abrasion. As expected, the more severe the abrasion, the greater the depth required to make the strength insensitive to abrasion. An abrasion-independent weakening mechanism that increased with exchange depth was also found to be operative.  相似文献   
120.
A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ?0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ?43 dB at 9.5 GHz. The achieved on state return loss is ?38 dB as compared to ?21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.  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