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   4253篇
  免费   297篇
  国内免费   4篇
电工技术   85篇
综合类   19篇
化学工业   982篇
金属工艺   92篇
机械仪表   70篇
建筑科学   342篇
矿业工程   18篇
能源动力   116篇
轻工业   333篇
水利工程   39篇
石油天然气   2篇
无线电   384篇
一般工业技术   883篇
冶金工业   376篇
原子能技术   17篇
自动化技术   796篇
  2024年   6篇
  2023年   64篇
  2022年   85篇
  2021年   155篇
  2020年   123篇
  2019年   103篇
  2018年   127篇
  2017年   110篇
  2016年   166篇
  2015年   178篇
  2014年   192篇
  2013年   279篇
  2012年   263篇
  2011年   336篇
  2010年   273篇
  2009年   227篇
  2008年   233篇
  2007年   228篇
  2006年   177篇
  2005年   165篇
  2004年   116篇
  2003年   97篇
  2002年   87篇
  2001年   61篇
  2000年   56篇
  1999年   65篇
  1998年   78篇
  1997年   68篇
  1996年   65篇
  1995年   46篇
  1994年   31篇
  1993年   30篇
  1992年   16篇
  1991年   16篇
  1990年   15篇
  1989年   26篇
  1988年   12篇
  1986年   12篇
  1985年   9篇
  1984年   6篇
  1981年   6篇
  1979年   13篇
  1977年   9篇
  1976年   19篇
  1975年   6篇
  1973年   10篇
  1971年   5篇
  1969年   6篇
  1940年   8篇
  1938年   5篇
排序方式: 共有4554条查询结果,搜索用时 31 毫秒
1.
Fullerenes are candidates for theranostic applications because of their high photodynamic activity and intrinsic multimodal imaging contrast. However, fullerenes suffer from low solubility in aqueous media, poor biocompatibility, cell toxicity, and a tendency to aggregate. C70@lysozyme is introduced herein as a novel bioconjugate that is harmless to a cellular environment, yet is also photoactive and has excellent optical and optoacoustic contrast for tracking cellular uptake and intracellular localization. The formation, water-solubility, photoactivity, and unperturbed structure of C70@lysozyme are confirmed using UV-visible and 2D 1H, 15N NMR spectroscopy. The excellent imaging contrast of C70@lysozyme in optoacoustic and third harmonic generation microscopy is exploited to monitor its uptake in HeLa cells and lysosomal trafficking. Last, the photoactivity of C70@lysozyme and its ability to initiate cell death by means of singlet oxygen (1O2) production upon exposure to low levels of white light irradiation is demonstrated. This study introduces C70@lysozyme and other fullerene-protein conjugates as potential candidates for theranostic applications.  相似文献   
2.
3.
4.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
5.
6.
An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr2Re3 type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content.  相似文献   
7.
Vector coupled-mode theory of dielectric waveguides   总被引:1,自引:0,他引:1  
A consistent derivation of a system of vector coupled-mode (VCM) equations for parallel dielectric waveguides is presented and compared with earlier versions of the improved coupled-mode theory (ICMT). As a validity test, it is shown that the effectively scalar transverse electric and transverse magnetic (TM) coupled-mode (CM) equations are direct limits of our full VCM formulation. In particular, our formulation does not lead to the fundamental error found with earlier coupled-mode theories (CMTs) in a case of TM fields. Functional equations of our VCMT are consistent with Maxwell's equations and lead to higher precision. They can be applied to complicated arrays of strongly coupled parallel dielectric waveguides with true vectorial behavior.  相似文献   
8.
9.
Nitric oxide (NO) acts as a modulator of neuronal transmission in mature neuronal systems, including the retina. Recently, NO has also been suggested to have a trophic function during development. We examined immunocytochemically the distribution of NO-producing cells in developing and transplanted rabbit retinas. An antibody detecting the neuronal isoform of its biosynthetic enzyme, nitric oxide synthase (NOS), was used on normal developing retinas [starting at embryonic day (E) 15] and on rabbit retinal transplants after various survival times (1-139 days after surgery). Weakly stained cell bodies were first observed in the proximal margin of the neuroblastic layer at E 29. Stained processes projecting towards a developing inner plexiform layer were also visible at this time point. Immunoreactive cells were located at later stages in the innermost part of the inner nuclear layer and in the ganglion cell layer, and are likely to correspond mainly to amacrine cells. NOS-labelled cells were also found in retinal transplants. The first NOS-labelled cells appeared, as in normal developing retinas, in ages corresponding to E 29 and were still detected in transplants corresponding to postnatal day 123. NOS-labelled cells were seen in areas between rosettes, where amacrine cells are located. NOS-labelled processes were at times seen to project for long distances, forming very distinct plexuses. NOS-containing amacrine cells thus appear both in the transplants and in developing retinas in the embryonic stages, long before synaptic function involving these cells can be expected, suggesting a role for NO not only in neuromodulation but also in retinal development.  相似文献   
10.
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