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   30071篇
  免费   2155篇
  国内免费   404篇
电工技术   864篇
综合类   522篇
化学工业   6383篇
金属工艺   1287篇
机械仪表   1762篇
建筑科学   965篇
矿业工程   192篇
能源动力   1202篇
轻工业   2619篇
水利工程   232篇
石油天然气   378篇
武器工业   64篇
无线电   4656篇
一般工业技术   5825篇
冶金工业   1879篇
原子能技术   407篇
自动化技术   3393篇
  2024年   43篇
  2023年   376篇
  2022年   615篇
  2021年   986篇
  2020年   722篇
  2019年   742篇
  2018年   934篇
  2017年   919篇
  2016年   1046篇
  2015年   909篇
  2014年   1422篇
  2013年   1924篇
  2012年   2026篇
  2011年   2454篇
  2010年   1875篇
  2009年   1850篇
  2008年   1709篇
  2007年   1397篇
  2006年   1208篇
  2005年   1112篇
  2004年   905篇
  2003年   854篇
  2002年   884篇
  2001年   789篇
  2000年   631篇
  1999年   590篇
  1998年   833篇
  1997年   527篇
  1996年   468篇
  1995年   338篇
  1994年   236篇
  1993年   203篇
  1992年   154篇
  1991年   123篇
  1990年   98篇
  1989年   110篇
  1988年   87篇
  1987年   69篇
  1986年   55篇
  1985年   48篇
  1984年   47篇
  1983年   41篇
  1982年   40篇
  1981年   40篇
  1980年   34篇
  1979年   16篇
  1977年   24篇
  1976年   35篇
  1975年   21篇
  1974年   13篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
2.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of...  相似文献   
3.
Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface-area adsorbents functionalized with high-selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen-rich polymer, is reported, giving rise to PAN-S nanoparticles with cyclic π-conjugated backbone and electronic conductivity. PAN-S can be coated on ultra-robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N- and S-containing soft Lewis bases have strong binding to Hg2+, Pb2+, Cu2+, and Cd2+, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter-electrode as metallic Hg0, Pb0, Cu0, and Cd0, and the PAN-S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN-S@ML filter can be fabricated cheaply and holds promise for scale-up applications.  相似文献   
4.
5.
Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl3) and hexamethyldisilazane (HN(SiMe3)2) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl3 and HN(SiMe3)2 to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl3 and HN(SiMe3)2 alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl3 with more heat released compared to that for the introduction of HN(SiMe3)2. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions.  相似文献   
6.
7.
Food Science and Biotechnology - Aluminum based reflective nanolens arrays were developed via a series of aluminum electropolishing and anodization steps with subsequent selective dissolution of...  相似文献   
8.
9.
Yang  Xi  Gao  Ling  Guo  Qing  Li  Yongjiang  Ma  Yue  Yang  Ju  Gong  Changyang  Yi  Cheng 《Nano Research》2020,13(10):2579-2594

Over the past decade, numerous studies have attempted to enhance the effectiveness of radiotherapy (external beam radiotherapy and internal radioisotope therapy) for cancer treatment. However, the low radiation absorption coefficient and radiation resistance of tumors remain major critical challenges for radiotherapy in the clinic. With the development of nanomedicine, nanomaterials in combination with radiotherapy offer the possibility to improve the efficiency of radiotherapy in tumors. Nanomaterials act not only as radiosensitizers to enhance radiation energy, but also as nanocarriers to deliver therapeutic units in combating radiation resistance. In this review, we discuss opportunities for a synergistic cancer therapy by combining radiotherapy based on nanomaterials designed for chemotherapy, photodynamic therapy, photothermal therapy, gas therapy, genetic therapy, and immunotherapy. We highlight how nanomaterials can be utilized to amplify antitumor radiation responses and describe cooperative enhancement interactions among these synergistic therapies. Moreover, the potential challenges and future prospects of radio-based nanomedicine to maximize their synergistic efficiency for cancer treatment are identified.

  相似文献   
10.
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s.  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