首页 | 官方网站   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   137385篇
  免费   4176篇
  国内免费   2598篇
工业技术   144159篇
  2023年   793篇
  2022年   1027篇
  2021年   1955篇
  2020年   1524篇
  2019年   1508篇
  2018年   2034篇
  2017年   2188篇
  2016年   2176篇
  2015年   2240篇
  2014年   3174篇
  2013年   6775篇
  2012年   4666篇
  2011年   6216篇
  2010年   5256篇
  2009年   5691篇
  2008年   5852篇
  2007年   6015篇
  2006年   5674篇
  2005年   5050篇
  2004年   4342篇
  2003年   4019篇
  2002年   3499篇
  2001年   3643篇
  2000年   3373篇
  1999年   3997篇
  1998年   10221篇
  1997年   6856篇
  1996年   5426篇
  1995年   3750篇
  1994年   3307篇
  1993年   3075篇
  1992年   1942篇
  1991年   1829篇
  1990年   1693篇
  1989年   1473篇
  1988年   1287篇
  1987年   940篇
  1986年   945篇
  1985年   958篇
  1984年   848篇
  1983年   716篇
  1982年   726篇
  1981年   695篇
  1980年   573篇
  1979年   471篇
  1978年   409篇
  1977年   536篇
  1976年   960篇
  1975年   297篇
  1974年   275篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Theoretical Foundations of Chemical Engineering - Troxerutin supported palladium (TXT-Pd) catalyst was prepared readily by using one-step synthetic method. As-fabricated TXT-Pd catalyst was...  相似文献   
42.
ABSTRACT

To ensure the reasonable application and perfect the theory of decision making with interval multiplicative preference relations (IMPRs), this paper continues to discuss decision making with IMPRs. After reviewing previous consistency concepts for IMPRs, we find that Krej?í’s consistency concept is more flexible and natural than others. However, it is insufficient to address IMPRs only using this concept. Considering this fact, this paper researches inconsistent and incomplete IMPRs that are usually encountered. First, programming models for addressing inconsistent and incomplete IMPRs are constructed. Then, this paper studies the consensus of individual IMPRs and defines a consensus index using the defined correlation coefficient. When the consensus requirement does not satisfy requirement, a programming model for improving consensus level is built, which can ensure the consistency. Subsequently, a procedure for group decision making with IMPRs is offered, and associated examples are provided to specifically show the application of main theoretical results.  相似文献   
43.
Wireless Personal Communications - The integration of the Internet of Things (IoT) and cloud environment has led to the creation of Cloud of Things, which has given rise to new challenges in IoT...  相似文献   
44.
This paper presents new results of studying the influence of parameters of microplasma spraying (MPS) of Ti wire on the structure and properties of Ti coatings. Based on the design of the experiment and the results of the SEM study, certain spraying modes were chosen to form the desired composition and structure of the Ti coating.  The dense sublayer (up to 300 µm thick) provides good adhesion to the substrate, and a porous top layer can accelerate the coated implant ingrowth with the bone.  This technology is developed for the manufacture of coated endoprosthesis implants.  相似文献   
45.
The LaNi5 intermetallic compound is an AB5 type hydrogen storage alloy which exhibits low operating temperature, easy activation, low pressure and tolerance to impurities. In this study, LaNi4.7-x Al0.3Bix (x = 0.0, 0.1, 0.2, 0.3) alloys were produced by melt-spinning technique and the effects of Al and Bi additions on the microstructure, thermal and hydrogen storage properties of LaNi5 were investigated. The results showed that substitution of Ni with Al led to a desired decrease in absorption/desorption plateau pressure and hysteresis without a decrease in hydrogen storage capacity. In contrast, Bi substitution with Ni increased the absorption/desorption plateau pressure, reduced the hydrogen capacity and increased pulverization resistance of the alloy due to the formation of BiLa and AlNi3 intermetallic phases at the grain boundaries.  相似文献   
46.
47.
Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.  相似文献   
48.
Liu  Dejia  Guo  Rui  Hu  Yong  Shen  Mingxue  Tang  Yanchuan  Zhao  Longzhi  Li  Deying  Wang  Xiangjie 《Metals and Materials International》2020,26(6):854-866
Metals and Materials International - High-entropy alloys having excellent properties are particularly suitable for the application as the filler metals in welding. In the present study,...  相似文献   
49.
Electroslag casting(ESC)is an important method to produce high quality castings.In this study,the ESC up-pulling inner mold method(EUPIM)was used to produce hollow cylindrical castings with the multiple consumable electrodes.The radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell were analyzed using the finite element method(FEM)with the aid of ANSYS software.The ProCAST software was used to calculate the specific heat,heat conductivity and density curve of Cu.Simulation results show that the radial deformation,the axial and radial internal stress of the inner mold,and the axial internal stress of the slag shell near the slag-metal interface of hollow cylndrical casting gradually increase from 0 s to 360 s after the ESC starting(slagging)process but before applying the up-pulling force.The suitable initial up-pulling moment of the inner mold is at around 180-198 s after the starting process.  相似文献   
50.
A small-scale silica gel-water adsorption system with modular adsorber, which utilizes solar energy to achieve the cogeneration of domestic air conditioning and water heating effect, is proposed and investigated in this paper. A heat recovery process between two adsorbers and a mass recovery process between two evaporators are adopted to improve the overall cooling and heating performance. First, the adsorption system is tested under different modes (different mass recovery, heat recovery, and cogeneration time) to determine the optimal operating conditions. Then, the cogeneration performance of domestic cooling and water heating effect is studied at different heat transfer fluid temperatures. The results show that the optimal time for cogeneration, mass recovery, and heat recovery are 600 s, 40 s, and 40 s, respectively. When the inlet temperature of hot water is around 85°C, the largest cooling power and heating power are 8.25 kW and 21.94 kW, respectively. Under the condition of cooling water temperature of 35°C, the obtained maximum COPc, COPh, and SCP of the system are 0.59, 1.39, and 184.5 W/kg, respectively.  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-23

京公网安备 11010802026262号