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   568篇
  免费   29篇
电工技术   2篇
化学工业   170篇
金属工艺   7篇
机械仪表   10篇
建筑科学   86篇
能源动力   7篇
轻工业   39篇
水利工程   2篇
石油天然气   2篇
无线电   18篇
一般工业技术   127篇
冶金工业   30篇
自动化技术   97篇
  2024年   1篇
  2023年   5篇
  2022年   8篇
  2021年   15篇
  2020年   6篇
  2019年   16篇
  2018年   14篇
  2017年   10篇
  2016年   13篇
  2015年   29篇
  2014年   22篇
  2013年   40篇
  2012年   34篇
  2011年   37篇
  2010年   20篇
  2009年   26篇
  2008年   37篇
  2007年   28篇
  2006年   29篇
  2005年   39篇
  2004年   17篇
  2003年   14篇
  2002年   13篇
  2001年   10篇
  2000年   10篇
  1999年   9篇
  1998年   14篇
  1997年   12篇
  1996年   5篇
  1995年   8篇
  1994年   5篇
  1993年   10篇
  1992年   7篇
  1991年   2篇
  1990年   3篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   3篇
  1980年   1篇
  1979年   3篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1967年   1篇
排序方式: 共有597条查询结果,搜索用时 15 毫秒
91.
An important recent advance in the functional analysis of Saccharomyces cerevisiae genes is the development of the one-step PCR-mediated technique for deletion and modification of chromosomal genes. This method allows very rapid gene manipulations without requiring plasmid clones of the gene of interest. We describe here a new set of plasmids that serve as templates for the PCR synthesis of fragments that allow a variety of gene modifications. Using as selectable marker the S. cerevisiae TRP1 gene or modules containing the heterologous Schizosaccharomyces pombe his5+ or Escherichia coli kanr gene, these plasmids allow gene deletion, gene overexpression (using the regulatable GAL1 promoter), C- or N-terminal protein tagging [with GFP(S65T), GST, or the 3HA or 13Myc epitope], and partial N- or C-terminal deletions (with or without concomitant protein tagging). Because of the modular nature of the plasmids, they allow efficient and economical use of a small number of PCR primers for a wide variety of gene manipulations. Thus, these plasmids should further facilitate the rapid analysis of gene function in S. cerevisiae. © 1998 John Wiley & Sons, Ltd.  相似文献   
92.
The question of pattern in architecture generally divides architects into two distinct groups: those with an aesthetic interest in man-made ornament; and those who take a deeper interest in the processes that underlie the formation of pattern in the natural world. An investigation of the performative, though, enables an exploration of pattern that arises out of the interaction of man-made interventions with the natural environment. Michael Hensel , Professor for research by Design at AHO, the Oslo School of Architecture and Design, and Achim Menges of the Emtech (Emergent Technologies and Design programme) at the Architectural Association in London, explore this arena based on their research and educational work at the AA and other international institutions, which focuses on aspects of performance in the built environment. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
93.
Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer   总被引:1,自引:0,他引:1  
The development of a new high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is reported. The high-resolution capabilities of this instrument allow the direct separation of most ions from inorganic and organic species at the same nominal m/z, the quantification of several types of organic fragments (CxHy, CxHyOz, CxHyNp, CxHyOzNp), and the direct identification of organic nitrogen and organosulfur content. This real-time instrument is field-deployable, and its high time resolution (0.5 Hz has been demonstrated) makes it well-suited for studies in which time resolution is critical, such as aircraft studies. The instrument has two ion optical modes: a single-reflection configuration offers higher sensitivity and lower resolving power (up to approximately 2100 at m/z 200), and a two-reflectron configuration yields higher resolving power (up to approximately 4300 at m/z 200) with lower sensitivity. The instrument also allows the determination of the size distributions of all ions. One-minute detection limits for submicrometer aerosol are <0.04 microg m(-3) for all species in the high-sensitivity mode and <0.4 microg m(-3) in the high-resolution mode. Examples of ambient aerosol data are presented from the SOAR-1 study in Riverside, CA, in which the spectra of ambient organic species are dominated by CxHy and CxHyOz fragments, and different organic and inorganic fragments at the same nominal m/z show different size distributions. Data are also presented from the MIRAGE C-130 aircraft study near Mexico City, showing high correlation with independent measurements of surrogate aerosol mass concentration.  相似文献   
94.
We report on chemically specific, subsurface imaging with high spatial resolution. Using tip-enhanced Raman spectroscopy, we probe carbon nanotubes buried beneath a host dielectric media. We demonstrate our ability to map and resolve specific vibrational modes with 30 nm spatial resolution for dielectric layers with different thicknesses.  相似文献   
95.
Renal nanoparticle passage opens the door for targeting new cells like podocytes, which constitute the exterior part of the renal filter. When cyclo(RGDfC)‐modified Qdots are tested on isolated primary podocytes for selective binding to the αvβ3 integrin receptor a highly cell‐ and receptor‐specific binding can be observed. In displacement experiments with free cyclo(RGDfC) IC50 values of 150 nM for αvβ3 integrin over‐expressing U87‐MG cells and 60 nM for podocytes are measured. Confocal microscopy shows a cellular Qdot uptake into vesicle‐like structures. Our ex vivo study gives clear evidence that, after renal filtration, nanoparticles can be targeted to podocyte integrin receptors in the future. This could be a highly promising approach for future therapy and diagnostics of podocyte‐associated diseases.  相似文献   
96.
Acousto-electric charge conveyance induced by a surface acoustic wave (SAW) is employed to dissociate photogenerated excitons. Over macroscopic distances, both electrons and holes are injected sequentially into a remotely positioned, isolated and high quality quantum emitter, a self-assembled quantum post. This process is found to be highly efficient and to exhibit improved stability at high acoustic powers when compared to direct optical pumping at the position of the quantum post. These characteristics are attributed to the wide matrix quantum well in which charge conveyance occurs and to the larger number of carriers available for injection in the remote configuration, respectively. The emission of such pumped quantum posts is dominated by recombination of neutral excitons and fully directional when the propagation direction of the SAW and the position of the quantum post are reversed.  相似文献   
97.
This work presents a new approach to the thermal modelling of direct laser interference patterning (DLIP). The spatial and temporal evolution of the temperature distribution within metallic substrates, which are irradiated by nanosecond pulses during the DLIP process, is computed by means of a smoothed particle hydrodynamics (SPH) method. The developed model considers the conversion of laser energy into heat within a very thin surface layer, heat conduction into the bulk material and the effect of latent heat during involved phase transformations. The importance of proper determination of characteristic SPH parameters and adequate spatial resolution of the computational domain on the accuracy of the numerical solution is discussed in detail. The computed temperature distributions are in good agreement with the results of a previously developed FEM model and correspond very well to simultaneously performed experimental investigations.  相似文献   
98.
Material behaviour computes form. In the physical world, material form is always inseparably connected to internal constraints and external forces; in the virtual space of digital design, though, form and force are usually treated as separate entities – divided into processes of geometric form generation and subsequent engineering simulation. Using the example of the interdisciplinary ICD/ITKE Research Pavilion, constructed at the University of Stuttgart in 2010, Moritz Fleischmann, Jan Knippers, Julian Lienhard, Achim Menges and Simon Schleicher explain how feedback between computational design, advanced simulation and robotic fabrication expands the design space towards previously unexplored architectural possibilities. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
99.
100.
A literature review of studies analyzing work–family conflict and its consequences was conducted, and 427 effect sizes were analyzed meta-analytically. Work–family conflict was analyzed bidirectionally in terms of work interference with family (WIF) and family interference with work (FIW). We assessed 3 categories of potential outcomes: work-related outcomes, family-related outcomes, and domain-unspecific outcomes. Results show that WIF and FIW are consistently related to all 3 types of outcomes. Both types of interrole conflict showed stronger relationships to same-domain outcomes than to cross-domain outcomes. Thus, WIF was more strongly associated with work-related than with family-related outcomes, and FIW was more strongly associated with family-related than with work-related outcomes. In moderator analyses, parenthood could not explain variability in effect sizes. However, time spent at work did moderate the relationships between WIF and family-related outcomes, as well as FIW and domain-unspecific outcomes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  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