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   155735篇
  免费   14693篇
  国内免费   9623篇
电工技术   5702篇
技术理论   3篇
综合类   10000篇
化学工业   40927篇
金属工艺   13231篇
机械仪表   6197篇
建筑科学   4639篇
矿业工程   3507篇
能源动力   5717篇
轻工业   10657篇
水利工程   1952篇
石油天然气   6443篇
武器工业   1078篇
无线电   17741篇
一般工业技术   22328篇
冶金工业   6344篇
原子能技术   2134篇
自动化技术   21451篇
  2024年   97篇
  2023年   2813篇
  2022年   3205篇
  2021年   5303篇
  2020年   5348篇
  2019年   6071篇
  2018年   3886篇
  2017年   4657篇
  2016年   4755篇
  2015年   4972篇
  2014年   7577篇
  2013年   8665篇
  2012年   10288篇
  2011年   13065篇
  2010年   10042篇
  2009年   11430篇
  2008年   9876篇
  2007年   11481篇
  2006年   10479篇
  2005年   8285篇
  2004年   6728篇
  2003年   5839篇
  2002年   4601篇
  2001年   3536篇
  2000年   3136篇
  1999年   2499篇
  1998年   1901篇
  1997年   1486篇
  1996年   1414篇
  1995年   1240篇
  1994年   1163篇
  1993年   903篇
  1992年   689篇
  1991年   547篇
  1990年   439篇
  1989年   350篇
  1988年   226篇
  1987年   171篇
  1986年   181篇
  1985年   113篇
  1984年   91篇
  1983年   65篇
  1982年   83篇
  1981年   69篇
  1980年   71篇
  1979年   49篇
  1978年   25篇
  1976年   24篇
  1975年   26篇
  1951年   25篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Internal stability assessment of geosynthetic-reinforced soil structures (GRSSs) has been commonly carried out assuming plane-strain conditions and dry backfills. However, failures of GRSSs usually show three-dimensional (3D) features and occur under unsaturated conditions. A procedure based on the kinematic limit-analysis method is proposed herein to assess 3D effects and the role of steady unsaturated infiltration on the required geosynthetic strength for GRSSs. A suction stress-based framework is used to describe the soil stress behavior under steady unsaturated infiltration. Based on the principle of energy-work balance, the required geosynthetic strength is determined. A comparison analysis with the prior research is conducted to verify the developed method. Two kinds of backfills, i.e., high-quality backfill and marginal backfill, are considered for comparison in this work. It is shown that accounting for 3D effects and the role of unsaturated infiltration considerably reduces the required geosynthetic strength. The 3D effects are primarily affected by the width-to-height ratio of GRSSs, and the contribution of unsaturated infiltration is mainly influenced by the soil type, flow rate, GRSS's height, and location of the water table.  相似文献   
2.
A novel hierarchical structure of bimetal sulfide FeS2@SnS2 with the 1D/2D heterostructure was developed for high-performance sodium-ion batteries (SIBs). The FeS2@SnS2 was synthesized through a hydrothermal reaction and a sulphuration process. The exquisite 1D/2D heterostructure is featured with 2D SnS2 nanoflakes anchoring on the 1D FeS2 nanorod. This well-designed FeS2@SnS2 provides shortened ion diffusion pathway and adequate surface area, which facilitates the Na+ transport and capacitive Na+ storage. Besides, the FeS2@SnS2 integrates the 1D/2D synthetic structural advantages and synthetic hybrid active material. Consequently, the FeS2@SnS2 anode exhibits high initial specific capacity of 765.5 mAh·g−1 at 1 A·g−1 and outstanding reversibility (506.0 mAh·g−1 at 1 A·g−1 after 200 cycles, 262.5 mAh·g−1 at 5 A·g−1 after 1400 cycles). Moreover, the kinetic analysis reveals that the FeS2@SnS2 anode displays significant capacitive behavior which boosts the rate capacity.  相似文献   
3.
The consumer demand for emerging technologies such as augmented reality (AR), autopilot, and three-dimensional (3D) internet has rapidly promoted the application of novel optical display devices in innovative industries. However, the micro/nanomanufacturing of high-resolution optical display devices is the primary issue restricting their development. The manufacturing technology of micro/nanostructures, methods of display mechanisms, display materials, and mass production of display devices are major technical obstacles. To comprehensively understand the latest state-of-the-art and trigger new technological breakthroughs, this study reviews the recent research progress of master molds produced using nanoimprint technology for new optical devices, particularly AR glasses, new-generation light-emitting diode car lighting, and naked-eye 3D display mechanisms, and their manufacturing techniques of master molds. The focus is on the relationships among the manufacturing process, microstructure, and display of a new optical device. Nanoimprint master molds are reviewed for the manufacturing and application of new optical devices, and the challenges and prospects of the new optical device diffraction grating nanoimprint technology are discussed.  相似文献   
4.
The SnO2-based family is a traditional but important gas-sensitive material. However, the requirement for high working temperature limits its practical application. Much work has been done to explore ways to improve its gas-sensing performance at room temperature (RT). For this report, SnO2, SnO, and SnO/SnO2 heterojunction was successfully synthesized by a facile hydrothermal combined with subsequent calcination. Pure SnO2 requires a high operating temperature (145 °C), while SnO/SnO2 heterojunction exhibits an excellent performance for sensing NO2 at RT. Moreover, SnO/SnO2 exhibits a fast response, of 32 s, to 50 ppm NO2 at RT (27 °C), which is much faster than that of SnO (139 s). The superior sensing properties of SnO/SnO2 heterojunction are attributed to the unique hierarchical structures, large number of adsorption sites, and enhanced electron transport. Our results show that SnO/SnO2 heterojunction can be used as a promising high-performance NO2 sensitive material at RT.  相似文献   
5.
Superamphiphobic surfaces have attracted the attention of researchers because of their broad application prospects. Currently, superamphiphobicity is primarily achieved by minimizing the solid–liquid contact area. Over the past few decades, researchers have primarily focused on using physical deposition methods to construct superamphiphobic surfaces using fine-sized nanoparticles (< 100 nm). However, porous hollow SiO2 particles (PH-SiO2), which are typically large spheres, have a highly hierarchical structure and can provide lower solid–liquid contact fractions than those provided by fine-sized particles. In this study, we used PH-SiO2 as building blocks and combined them with poly (dimethylsiloxane) to construct a mechanically robust coating on fiber by spray-coating. After chemical vapor deposition treatment, the coating exhibited excellent superamphiphobicity and could repel various liquids, covering a wide range of surface tensions (27.4–72.0 mN·m−1).  相似文献   
6.
In recent years, superhydrophobic coatings have received extensive attention due to their functions of waterproof, antifouling, self-cleaning, etc. However, wide applications of superhydrophobic coatings are still affected by their disadvantages of complex preparation, low mechanical properties, and poor ultraviolet (UV) resistance. In this study, cellulose nanocrystal containing a small amount of lignin (L-CNC)/SiO2 composite particles were used as the main material, polydimethylsiloxane (PDMS) as the adhesive and perfluorooctyltrichlorosilane (FOTS) as the modifier to prepare superhydrophobic coatings by a one-step spray method. The resulted coating showed excellent superhydrophobicity (water contact angle (WCA) of 161° and slide angle (SA) of 7°) and high abrasion resistance (capable of withstanding 50 abrasion cycles under the load of 50 g). Moreover, it still maintained good superhydrophobicity after 5 h of exposure to the UV light (1000 W), displaying its good UV resistance. This study provides theoretical and technical reference for the simple preparation of organic‒inorganic composite superhydrophobic coatings with high abrasion resistance and good UV resistance, which is beneficial to improving the practicability and broadening the application scope of superhydrophobic coatings.  相似文献   
7.
8.
9.
王亮  程树森  刘朋波  陈艳波 《钢铁》2022,57(1):48-56
 随着高品位铁矿石消耗的加快,资源逐渐趋于贫化,钢铁企业可利用的铁矿石原料逐渐向中低品位原料转变,尤其是高铝铁矿,这类原料的使用无疑会增加高炉渣中Al2O3质量分数,影响高炉现有的操作制度。Al2O3质量分数为15%~17%的高炉渣,由于Al2O3含量高而使高炉渣的冶金性能变差,为了保证高炉渣的冶金性能,必须在其中添加8%左右的MgO。然而,Al2O3含量相似的浦项钢铁的高炉渣,其MgO质量分数仅为4%左右,高炉实现了高效、稳定、顺行。因此,从高炉CaO-SiO2-Al2O3-MgO四元渣系的物理化学机理出发,研究了K2O、Na2O对高炉渣四元渣系CaO-SiO2-Al2O3-MgO中各组元活度的影响;研究了“渣-气”平衡条件下渣中碱金属氧化物和气体中碱金属的关系;计算了K2O、Na2O和MgO对黏度的影响。结果显示,在考虑高炉渣CaO-SiO2-Al2O3-MgO中各组元活度、碱金属在渣-气间的分布和炉渣黏度的情况下,当碱金属氧化物K2O和Na2O存在时,可以适当减小MgO含量,并可以保证高炉渣各组元活度及炉渣黏度基本不变。这不仅有助于减少高炉原料中添加含镁熔剂、提高原料品位、高效排碱、降低碱危害、减少碳排放、延长高炉寿命及降低成本,还能促进钢铁企业实现节能减排的目标。  相似文献   
10.
 为了掌握高Al2O3条件下(w(Al2O3)为15%以上)高炉渣系的熔化特性,利用差式扫描量热仪分析了不同w(MgO)/w(Al2O3)、碱度(R)以及w(Al2O3)对高铝高炉渣的熔化温度及熔化热的影响。试验结果表明,炉渣熔化开始温度为1 248~1 291 ℃、熔化结束温度为1 432~1 485 ℃、熔化热为137~211 J/g;当w(Al2O3)=15%、高w(MgO)/w(Al2O3)时,发生了共晶逆反应,导致高炉炉渣熔化开始温度逐渐降低,但由于高炉炉渣的液相线温度基本未变,所以炉渣熔化结束温度基本未发生改变;w(Al2O3)为20%时,随着w(MgO)/w(Al2O3)的增加,炉渣中易生成熔点较高的镁铝尖晶石,导致高炉炉渣熔化开始温度逐渐增大,与此同时,炉渣液相线温度逐渐降低,导致炉渣熔化结束温度逐渐降低;随着碱度R的增加,高炉炉渣中生成了具有高熔点的化合物、炉渣的液相线温度升高,使得高炉炉渣的熔化开始温度逐渐增加、炉渣熔化结束温度逐渐升高;随着w(Al2O3)的增加,发生了共晶逆反应,故炉渣的熔化开始温度逐渐降低,而随着w(Al2O3)的增加,炉渣中键能较大的Al—O键增多,需要在更高温度下才能实现炉渣的最终熔化,即熔化结束温度逐渐增加;随着w(MgO)/w(Al2O3)、R以及w(Al2O3)的增加,炉渣熔化热逐渐增多。分析认为,随着R的增加,炉渣中有高熔点化合物的生成,熔化热增加;随着炉渣中w(Al2O3)的增加,炉渣中Al—O键增多,解聚破坏熔渣结构消耗的热量增多;而随着w(MgO)/w(Al2O3)增加,高熔点化合物的生成或熔化开始温度降低,造成熔化热增加。  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