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   130658篇
  免费   12687篇
  国内免费   7928篇
电工技术   9566篇
技术理论   4篇
综合类   12015篇
化学工业   19635篇
金属工艺   7507篇
机械仪表   8591篇
建筑科学   10112篇
矿业工程   3217篇
能源动力   3660篇
轻工业   10727篇
水利工程   2923篇
石油天然气   5346篇
武器工业   1233篇
无线电   15876篇
一般工业技术   14031篇
冶金工业   4967篇
原子能技术   1747篇
自动化技术   20116篇
  2024年   487篇
  2023年   1712篇
  2022年   3499篇
  2021年   4921篇
  2020年   3723篇
  2019年   3064篇
  2018年   3229篇
  2017年   3664篇
  2016年   3561篇
  2015年   5031篇
  2014年   6550篇
  2013年   7817篇
  2012年   9411篇
  2011年   9945篇
  2010年   9216篇
  2009年   9071篇
  2008年   9114篇
  2007年   8473篇
  2006年   8166篇
  2005年   6713篇
  2004年   5216篇
  2003年   4634篇
  2002年   5462篇
  2001年   4775篇
  2000年   3381篇
  1999年   2420篇
  1998年   1555篇
  1997年   1300篇
  1996年   1129篇
  1995年   945篇
  1994年   711篇
  1993年   517篇
  1992年   429篇
  1991年   322篇
  1990年   253篇
  1989年   185篇
  1988年   155篇
  1987年   113篇
  1986年   51篇
  1985年   68篇
  1984年   49篇
  1983年   37篇
  1982年   32篇
  1981年   28篇
  1980年   32篇
  1979年   20篇
  1977年   12篇
  1976年   16篇
  1959年   12篇
  1951年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
ABSTRACT

The thermal characterization of aluminum flat grooved heat pipes is performed experimentally for different groove dimensions. Three heat pipes with groove widths of 0.2?mm, 0.4?mm, and 1.5?mm are used in the experiments. The effect of the amount of the working fluid is extensively studied for each groove width. The results reveal that, although all three succeed in dissipating the heat input through the phase change of the working fluid by continuous evaporation and condensation, the effectiveness of the heat transfer increases with reduced groove width. Furthermore, it is observed that there exists an optimum operating point, where the temperature difference between the heating and cooling sections is at a minimum, and the magnitude of this temperature difference is a strong function of the groove width. To the best of the authors’ knowledge, the combined effects of groove dimensions and the amount of the working fluid, from fully flooded to dry, is reported for the first time for aluminum flat grooved heat pipes.  相似文献   
22.
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   
23.
24.
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance.  相似文献   
25.
陈国亮  李宏  朱旭 《纺织器材》2015,42(1):61-62
为了解决钢丝圈挂花问题,阐述了LH001新型钢丝圈清洁器的特点和应用效果;通过试验说明使用新型钢丝圈清洁器断头率低,基本无挂花,纺纱效果好。指出:新型钢丝圈清洁器是普通钢丝圈清洁器的更新换代产品,值得推广。  相似文献   
26.
The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. GdIII−GdIII distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-GdIII were indistinguishable from GdIII−GdIII distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.  相似文献   
27.
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations...  相似文献   
28.
29.
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.  相似文献   
30.
介绍锚杆应用及常用的拆锚方法,针对现有前混合磨料射流退锚装置存在锚杆拆卸时间长、工人作业环境差、装置部件锈蚀维护性差等问题,提出了一种前混合磨料射流退锚改进装置,并进行现场试验,结果表明,所改进设计装置具有退锚时间短、对工人伤害小、操作简便、部件维护周期长和无需专门配备泵站等特点,对进一步提高锚杆拆除效率具有重要参考价值。  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