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   1800篇
  免费   57篇
  国内免费   3篇
电工技术   25篇
综合类   2篇
化学工业   385篇
金属工艺   80篇
机械仪表   42篇
建筑科学   28篇
矿业工程   1篇
能源动力   103篇
轻工业   89篇
水利工程   17篇
石油天然气   8篇
无线电   230篇
一般工业技术   368篇
冶金工业   184篇
原子能技术   21篇
自动化技术   277篇
  2023年   15篇
  2022年   22篇
  2021年   33篇
  2020年   18篇
  2019年   39篇
  2018年   43篇
  2017年   36篇
  2016年   43篇
  2015年   35篇
  2014年   43篇
  2013年   111篇
  2012年   65篇
  2011年   103篇
  2010年   84篇
  2009年   78篇
  2008年   78篇
  2007年   78篇
  2006年   67篇
  2005年   55篇
  2004年   29篇
  2003年   46篇
  2002年   39篇
  2001年   30篇
  2000年   29篇
  1999年   36篇
  1998年   67篇
  1997年   52篇
  1996年   32篇
  1995年   34篇
  1994年   43篇
  1993年   25篇
  1992年   35篇
  1991年   37篇
  1990年   21篇
  1989年   24篇
  1988年   13篇
  1987年   12篇
  1986年   11篇
  1985年   21篇
  1984年   18篇
  1983年   26篇
  1982年   21篇
  1981年   19篇
  1980年   16篇
  1979年   12篇
  1978年   8篇
  1977年   12篇
  1975年   12篇
  1974年   11篇
  1973年   9篇
排序方式: 共有1860条查询结果,搜索用时 125 毫秒
1.
GeTe is a promising candidate for the fabrication of high-temperature segments for p-type thermoelectric (TE) legs. The main restriction for the widespread use of this material in TE devices is high carrier concentration (up to ∼ 1021 cm−3), which causes the low Seebeck coefficient and high electronic component of thermal conductivity. In this work, the band structure diagram and phase equilibria data have been effectively used to attune the carrier concentration and to obtain the high TE performance. The Ge1−xBixTe (x = 0.04) material prepared by the Spark plasma sintering (SPS) technique demonstrates a high power factor accompanied by moderate thermal conductivity. As a result, a significantly higher dimensionless TE figure of merit ZT = 2.0 has been obtained at ∼ 800 K. Moreover, we are the first to propose that application of the developed Ge1−xBixTe (x = 0.04) material in the TE unicouple should be accompanied by SnTe and CoGe2 transition layers. Only such a unique solution for the TE unicouple makes it possible to prevent the negative effects of high contact resistance and chemical diffusion between the segments at high temperatures.  相似文献   
2.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
3.
Bulletin of Engineering Geology and the Environment - The pavements of the Beijing Capital International Airport (BCIA), China, where a buried fault zone lies beneath, have undergone continuous...  相似文献   
4.
Zinc (Zn), the second-most necessary trace element, is abundant in the human body. The human body lacks the capacity to store Zn; hence, the dietary intake of Zn is essential for various functions and metabolism. The uptake of Zn during its transport through the body is important for proper development of the three major accessory sex glands: the testis, epididymis, and prostate. It plays key roles in the initial stages of germ cell development and spermatogenesis, sperm cell development and maturation, ejaculation, liquefaction, the binding of spermatozoa and prostasomes, capacitation, and fertilization. The prostate releases more Zn into the seminal plasma during ejaculation, and it plays a significant role in sperm release and motility. During the maternal, labor, perinatal, and neonatal periods, the part of Zn is vital. The average dietary intake of Zn is in the range of 8–12 mg/day in developing countries during the maternal period. Globally, the dietary intake of Zn varies for pregnant and lactating mothers, but the average Zn intake is in the range of 9.6–11.2 mg/day. The absence of Zn and the consequences of this have been discussed using critical evidence. The events and functions of Zn related to successful fertilization have been summarized in detail. Briefly, our current review emphasizes the role of Zn at each stage of human reproduction, from the spermatogenesis process to childbirth. The role of Zn and its supplementation in in vitro fertilization (IVF) opens opportunities for future studies on reproductive biology.  相似文献   
5.
A nanocomposite CuTi layered double hydroxide (LDH) supported on g-C3N4 (15 wt% of g-C3N4) is facilely synthesized by hydrothermal method. There are electrostatic interactions between positive layers of CuTi-LDH and negatively charged inner g-C3N4 sheets. The nanocomposite and its precursors are characterized through various analytical techniques, which affirmed the presence of both g-C3N4 and CuTi-LDH characteristic features. The pore-enriched hybrid geometry of CuTi-LDH@g-C3N4 with high specific surface area (146 m2/g), and suitable band gap of 2.46 eV enables the nanocomposite to act as both an electrocatalyst and photoelectrocatalyst for oxygen evolution reaction (OER). Both the electrochemical and photoelectrochemical studies are done using 1 M KOH (pH = 13.6) with applied potential of ?0.2 V to 1.5 V vs. Ag/AgCl. The onset potential of CuTi-LDH@g-C3N4 for OER appears at η = 0.36 V in dark and η = 0.32 V under visible light illumination of 30 min. Also, Mott-Schottky analysis shows n-type semiconductor behaviour for CuTi-LDH@g-C3N4 and its precursors. The photoelectrochemical water oxidation proceeds by charge transfer across a Type II heterojunction formed between the CuTi-LDH and g-C3N4 materials.  相似文献   
6.
Researchers have derived inspiration from the biophotosynthetic structures in nature and have started to synthesize the modified bioinspired solar cells copying the evolved organic and inorganic material properties. One of the highlighted examples of bioinspired photo voltaic (PV) cells is the astonishing achievement of an increase in the absorption of integrated sunlight waves in unpatterned solar cells simulated from the wings of the butterfly. Further, deployment possibilities of incorporating flexible cells on flat or curved surfaces for optimizing performance are also under progress. This article mainly discusses the recent concepts of bioinspired solar cells at the research and development level with the prospects and challenges that lie ahead in the upcoming field of photovoltaic renewable energy cell technology. Different potential materials found suitable for bioinspired solar cells construction are reviewed with their particular challenges.  相似文献   
7.
Journal of Materials Science - Flexible and stretchable strain sensors are in great demand in advanced health care, human–machine interface, stretchable electronics, electronic skin, etc. Of...  相似文献   
8.
Wireless Personal Communications - Ultrasound scan plays a predominant role in assisting the health care provider for monitoring pregnancy. This methods is employed for providing insights about...  相似文献   
9.
Bulletin of Engineering Geology and the Environment - The numerical methods for slope stability problems always have a serious concern related to their continuum and discontinuum nature. In...  相似文献   
10.
Use of mining and seismological parameters as premonitors of rockbursts   总被引:2,自引:0,他引:2  
Comprising one of the deepest mines in the world, the gold mining region of the Kolar Gold Fields (KGF) in southern India is known to be confronted with the acute problem of rockbursts that pose a hazard to workmen and cause disruptions in the production schedule. In combination with mining parameters, seismological data of these rockbursts events systematically monitored over the years using a regional seismic network have been employed to examine and model premonitory characteristics of the events. Linear empirical relations are established relying on correlations seen between the seismic energy released due to a rockburst, total tonnage of ore mined out and total number of rockbursts, as well as seismic events in some shallow and deep workings currently active at KGF. The deterministic model, although not free from certain limitations at present, has been applied to predict rockburst activity with some success.  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