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   3272篇
  免费   147篇
  国内免费   24篇
电工技术   46篇
综合类   5篇
化学工业   795篇
金属工艺   97篇
机械仪表   102篇
建筑科学   112篇
矿业工程   6篇
能源动力   412篇
轻工业   277篇
水利工程   17篇
石油天然气   66篇
无线电   281篇
一般工业技术   596篇
冶金工业   172篇
原子能技术   20篇
自动化技术   439篇
  2024年   9篇
  2023年   68篇
  2022年   148篇
  2021年   195篇
  2020年   132篇
  2019年   116篇
  2018年   202篇
  2017年   141篇
  2016年   154篇
  2015年   93篇
  2014年   144篇
  2013年   270篇
  2012年   163篇
  2011年   200篇
  2010年   131篇
  2009年   145篇
  2008年   107篇
  2007年   99篇
  2006年   91篇
  2005年   44篇
  2004年   63篇
  2003年   67篇
  2002年   47篇
  2001年   32篇
  2000年   31篇
  1999年   33篇
  1998年   56篇
  1997年   39篇
  1996年   36篇
  1995年   40篇
  1994年   20篇
  1993年   27篇
  1992年   25篇
  1991年   22篇
  1990年   15篇
  1989年   22篇
  1988年   13篇
  1987年   11篇
  1986年   14篇
  1985年   26篇
  1984年   17篇
  1983年   13篇
  1982年   15篇
  1981年   13篇
  1980年   15篇
  1979年   11篇
  1977年   12篇
  1976年   8篇
  1974年   7篇
  1973年   11篇
排序方式: 共有3443条查询结果,搜索用时 15 毫秒
81.
82.
The behavior of electrospun polyvinyl alcohol (PVA) and polyethylene oxide (PEO) nanofibers embedded with urea is studied as a function of various process parameters. Our results show that three‐dimensional nanofiber networks can be obtained when high concentrations of urea in the solution are used during electrospinning. The nanofibers are characterized using both scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The stability of the nanofiber as a function of electric field has also been studied. The successful formation of three‐dimensional nanofiber networks can open new trends toward applications in fertilizers containing nanofibers in the nanoagricultural field. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39840.  相似文献   
83.
Measurements were made on a series of cotton/polyester blends having different compositions. The results showed that the time to ignition increased as the polyester contents of the fabric were increased. An explanation of this observation is given. Both the orientation of the fabric and the temperature of the furnace environment affect the time-to-ignition values. The time to ignition was found to be longer for the fabric loaded in horizontal position than that loaded in vertical position. This difference was attributed to the effect of the forced convection induced inside the furnace. © 1996 John Wiley & Sons, Inc.  相似文献   
84.
This article presents an effective analytical model for determining the moisture diffusivities and moisture transfer coefficients for solid objects (namely, infinite slab, infinite cylinder, sphere; and also for irregularly shaped objects, by using a shape factor) subject to drying applications in a medium. The unsteady-state moisture diffusion analysis is used on the basis of two important criteria: 0·1 <Bi < 100 and Bi > 100. The drying coefficients and lag factors were employed. The analytical models are then verified using available experimental data taken from the literature. The results show that the method presented here can be used to determine the moisture diffusion coefficients and moisture transfer coefficients for such solid objects in a simple and accurate manner for a variety of drying applications.  相似文献   
85.
Digital cellular systems will have profound implications for the integration of mobile computing and communications allowing true networking on the move. The European-developed GSM system is rapidly becoming the de-facto world standard for mobile communications. Other emerging standards include IS-54 in North America and PDC in Japan, in addition to the CDMA standard (IS-95) in the USA. The aim of this article is to compare the four emerging standards, with particular emphasis on their user capacity and spectrum utilization efficiency.  相似文献   
86.
The synthesis of starch/glycidyl methacrylate/acrylic acid cation exchange composites was achieved by bulk polymerizing of acrylic acid (AA)/glycidyl methacrylate (GMA) mixtures in presence of starch using sodium peroxydisulphate/sodium sulphite initiating redox system. The effect of the concentration of each of sodium peroxydisulphate sodium sulphite, AA and GMA as well as polymerization temperature on the formation of the composites was investigated. Five kinds of composites of different carboxyl contents were prepared and characterized by investigating their potentiometric titrations, durabilities to use, as well as water swellabilities and solubilities.  相似文献   
87.
88.
2-Aroyl-3-methyl-1 H-1,4-benzothiazine ylids ( 2a – k ) were prepared by alkylation of the corresponding 4H-benzothiazines 1 . The ylids 2 are labile at room temperature; proper analytical and 1H-n.m.r. data were obtained for their picrates. E.s.r. studies of u. v. irradiated polycrystalline form of ( 2 ; R1 = Me, R2 = H) gave evidence for a long-lived benzothiazinyl radical with the odd electron residing on nitrogen 6 .  相似文献   
89.
Poly(ε-caprolactone) (PCL) is a bioresorbable and biocompatible polymer with assorted medical applications. However, remarkable hydrophobicity and nonosteoconductivity have stood as a barrier to limit its applications. The present study aims to modify the bulk characteristics of PCL to develop a polymeric scaffold with adequate structural and mechanical properties to support regenerated tissues. For this purpose, functionalized bacterial cellulose nanowhiskers (BCNW-g-βCD-PCL2000) are synthesized. Reinforcing PCL matrix with 4 wt % of the nanowhiskers resulted in a bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite shows improvements of 115 and 51% in tensile strength and Young's modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous structures of 86–95% porosity with interconnected macropores of mean pore diameters of 250–420 μm. Porous scaffolds showed compression modulus values of 5.3–9.1 MPa and would have promising applications in regenerative medicine. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48481.  相似文献   
90.
SMYD3 is a lysine methyltransferase that regulates the expression of over 80 genes and is required for the uncontrolled proliferation of most breast, colorectal, and hepatocellular carcinomas. The elimination of SMYD3 restores normal expression patterns of these genes and halts aberrant cell proliferation, making it a promising target for small molecule inhibition. In this study, we sought to establish a proof of concept for our in silico/in vitro hit-to-lead enzyme inhibitor development platform and to identify a lead small molecule candidate for SMYD3 inhibition. We used Schrodinger® software to screen libraries of small molecules in silico and the five compounds with the greatest predicted binding affinity within the SMYD3 binding pocket were purchased and assessed in vitro in direct binding assays and in breast cancer cell lines. We have confirmed the ability of one of these inhibitors, Inhibitor-4, to restore normal rates of cell proliferation, arrest the cell cycle, and induce apoptosis in breast cancer cells without affecting wildtype cell behavior. Our results provide a proof of concept for this fast and affordable small molecule hit-to-lead methodology as well as a promising candidate small molecule SMYD3 inhibitor for the treatment of human cancer.  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