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   3585篇
  免费   212篇
  国内免费   2篇
电工技术   29篇
综合类   2篇
化学工业   896篇
金属工艺   78篇
机械仪表   84篇
建筑科学   138篇
矿业工程   12篇
能源动力   130篇
轻工业   271篇
水利工程   30篇
石油天然气   8篇
无线电   275篇
一般工业技术   749篇
冶金工业   484篇
原子能技术   17篇
自动化技术   596篇
  2024年   8篇
  2023年   49篇
  2022年   94篇
  2021年   173篇
  2020年   89篇
  2019年   85篇
  2018年   126篇
  2017年   114篇
  2016年   122篇
  2015年   103篇
  2014年   164篇
  2013年   255篇
  2012年   225篇
  2011年   285篇
  2010年   206篇
  2009年   167篇
  2008年   172篇
  2007年   184篇
  2006年   121篇
  2005年   103篇
  2004年   100篇
  2003年   88篇
  2002年   78篇
  2001年   45篇
  2000年   40篇
  1999年   37篇
  1998年   72篇
  1997年   70篇
  1996年   36篇
  1995年   36篇
  1994年   27篇
  1993年   25篇
  1992年   24篇
  1991年   16篇
  1990年   28篇
  1989年   18篇
  1988年   11篇
  1987年   9篇
  1986年   11篇
  1985年   18篇
  1984年   9篇
  1983年   13篇
  1982年   9篇
  1981年   13篇
  1980年   11篇
  1979年   10篇
  1977年   9篇
  1976年   21篇
  1975年   8篇
  1974年   9篇
排序方式: 共有3799条查询结果,搜索用时 15 毫秒
961.
962.
963.
964.
The insignificant relationship between rewards and actual compliance with information security policies does not make sense. Quite possibly this relationship results from not applying rewards for security compliance.  相似文献   
965.
The application of ionic liquids (ILs) has grown enormously, from their use as simple solvents, catalysts, media in separation science, or electrolytes to that as task-specific, tunable molecular machines with appropriate properties. A thorough understanding of these properties and structure–property relationships is needed to fully exploit their potential, open new directions in IL-based research and, finally, properly implement the appropriate applications. In this work, we investigated the structure–properties relationships of a series of alkyltriethylammonium bis(trifluoromethanesulfonyl)imide [TEA-R][TFSI] ionic liquids in relation to their thermal behavior, structure organization, and self-diffusion coefficients in the bulk state using DSC, FT-IR, SAXS, and NMR diffusometry techniques. The phase transition temperatures were determined, indicating alkyl chain dependency. Fourier-transformed infrared spectroscopy studies revealed the structuration of the ionic liquids along with alkyl chain elongation. SAXS experiments clearly demonstrated the existence of polar/non-polar domains. The alkyl chain length influenced the expansion of the non-polar domains, leading to the expansion between cation heads in polar regions of the structured IL. 1H NMR self-diffusion coefficients indicated that alkyl chain elongation generally caused the lowering of the self-diffusion coefficients. Moreover, we show that the diffusion of anions and cations of ILs is similar, even though they vary in their size.  相似文献   
966.
Doxorubicin is an effective chemotherapeutic drug, however, its toxicity is a significant limitation in therapy. Encapsulation of doxorubicin inside liposomes or ferritin cages decreases cardiotoxicity while maintaining anticancer potency. We synthesized novel apoferritin- and liposome-encapsulated forms of doxorubicin (“Apodox” and “lip-8-dox”) and compared its toxicity with doxorubicin and Myocet on prostate cell lines. Three different prostatic cell lines PNT1A, 22Rv1, and LNCaP were chosen. The toxicity of the modified doxorubicin forms was compared to conventional doxorubicin using the MTT assay, real-time cell impedance-based cell growth method (RTCA), and flow cytometry. The efficiency of doxorubicin entrapment was 56% in apoferritin cages and 42% in the liposome carrier. The accuracy of the RTCA system was verified by flow-cytometric analysis of cell viability. The doxorubicin half maximal inhibition concentrations (IC50) were determined as 170.5, 234.0, and 169.0 nM for PNT1A, 22Rv1, and LNCaP, respectively by RTCA. Lip8-dox is less toxic on the non-tumor cell line PNT1A compared to doxorubicin, while still maintaining the toxicity to tumorous cell lines similar to doxorubicin or epirubicin (IC50 = 2076.7 nM for PNT1A vs. 935.3 and 729.0 nM for 22Rv1 and LNCaP). Apodox IC50 was determined as follows: 603.1, 1344.2, and 931.2 nM for PNT1A, 22Rv1, and LNCaP.  相似文献   
967.
The majority of important reactions in beer are associated with the action of oxygen during malting and brewing. With respect to oxygen, beer is considered to possess a relatively strong reducing environment. The gradual reduction of oxygen gives rise to reactive oxygen species (ROS) capable of attacking beer components that are important to consumers. Indigo carmine (IC) bleaching was used to prove ROS formation formed by oxidation of beer energy sources such as maltose and ethanol. This paper examines oxygen radical oxidation of organic matter in the presence of the radical initiator potassium peroxodisulphate. A mixture of organic sources of energy such as maltose and ethanol, oxygen, radical initiator and cupric ions generates ROS formation in a broad range of concentrations even at room temperature. ROS irreversibly split blue dye IC into the colourless form and takes part in the radical transformation of organic matter, which is similar to its burning at low temperature or to radical oxidation of reducing agents. Other organic matter can suppress ROS formation and be incorporated into the radical chain of the pathway of its ‘cold burning’. Ethanol inhibited phenylalanine oxidation during its oxidative Maillard reaction. IC bleaching can serve as simple indicator of ROS generation in aerated food. Copyright © 2015 The Institute of Brewing & Distilling  相似文献   
968.
We show here how a simple data mining of bibliographic records can be used to follow and help understand the evolution of a research domain, at a level that cannot be captured by reading individual papers in a field of this size. We illustrate the approach by investigating 43 yr of research on ceramic materials, covered by 253 000 bibliographic records. The patterns of keywords used reveal the trends and the evolution of research ideas and priorities within the field. Simple, interactive tools based on co‐word network analysis help us better appreciate the organization and relationships of ideas or individuals, and hopefully allow identification of unexplored concepts, connections, or approaches on a given topic.  相似文献   
969.
Composites of isotactic polypropylene filled with comminuted rapeseed straw are studied. Improvement in interfacial adhesion is achieved by chemical modification of the lignocellulose filler. Composites were subjected to recycling by extrusion. The effect of multiple recycling of the composites on the process of nucleation and crystallization of polypropylene matrix, surface topography, and free radical generation was checked. On the basis of differential scanning calorimetry data, a significant influence of the recycling on nucleation activity of the lignocellulose filler was evidenced. A relation between the filler particle size and multiple recycling was established by observations under a polarization microscope, while scanning electron microscope analyses confirmed the positive effect of chemical modification of rapeseed straw on the interfacial adhesion. The composite structure changes forced by multiple recycling are discussed in the context of free radical generation. Concentration of free radicals in the rapeseed straw samples and composites was measured by the electron paramagnetic resonance spectroscopy to show that it was higher in the systems subjected to multiple recycling. Interestingly, the composites after multiple recycling showing elevated concentration of free radicals are also characterized by higher nucleation activity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41693.  相似文献   
970.
A highly compartmentalized enzymatic network regulates the pro‐apoptotic and proliferative effects of sphingolipids. Over‐conversion of ceramide (Cer) correlates with insensitivity to apoptosis signaling (in response to chemotherapy) and to drug resistance of cancer cells. De novo sphingomyelin biosynthesis relies on non‐vesicular ceramide trafficking by the CERT (CERamide Transfer) protein. Therefore, blocking CERT transfer, thus leading to increased intracellular ceramide availability, represents a potential anticancer strategy. Our study is based on the implementation of an in vitro binding assay, supported by in silico molecular docking. It constitutes the first attempt to explore at the molecular level for the identification of novel CERT ligands. This approach is the first step toward in silico design and optimization of CERT inhibitor candidates, potentially relevant as innovative ceramide‐transfer‐targeting therapeutic agents.  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