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   659篇
  免费   41篇
电工技术   5篇
综合类   2篇
化学工业   190篇
金属工艺   18篇
机械仪表   9篇
建筑科学   50篇
矿业工程   2篇
能源动力   17篇
轻工业   39篇
水利工程   2篇
无线电   55篇
一般工业技术   134篇
冶金工业   34篇
原子能技术   6篇
自动化技术   137篇
  2023年   16篇
  2022年   10篇
  2021年   20篇
  2020年   12篇
  2019年   11篇
  2018年   12篇
  2017年   17篇
  2016年   28篇
  2015年   15篇
  2014年   32篇
  2013年   33篇
  2012年   34篇
  2011年   43篇
  2010年   47篇
  2009年   46篇
  2008年   38篇
  2007年   43篇
  2006年   16篇
  2005年   25篇
  2004年   25篇
  2003年   14篇
  2002年   6篇
  2001年   9篇
  2000年   15篇
  1999年   13篇
  1998年   6篇
  1997年   12篇
  1996年   11篇
  1995年   2篇
  1994年   7篇
  1993年   6篇
  1992年   9篇
  1991年   6篇
  1990年   2篇
  1989年   3篇
  1988年   6篇
  1987年   4篇
  1986年   8篇
  1985年   2篇
  1983年   4篇
  1982年   4篇
  1981年   6篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1974年   2篇
  1966年   3篇
  1964年   1篇
排序方式: 共有700条查询结果,搜索用时 953 毫秒
91.
92.
93.
94.
Among other waveguide elements directional couplers are required in integrated millimeterwave circuits in image guide technique. Hereby an I-guide is used which consists of a dielectric slab between two conducting plates on which the electric field is perpendicularily. Flat coupling behaviour and better isolation can be reached by use of a dielectric coupling element and absorber materials. Thereby the frequency dependence is reduced significantly. Further the coupling can be steered by an additional premagnetized ferrite slab. In this way switched couplers can be realized.  相似文献   
95.
One‐dimensional fibers and tubes are constructed through the oriented carbon‐carbon cross‐linking reactions towards rigid conjugated polymer networks. As the result, a template‐free and one‐step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as‐formed carbon‐rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m2 g–1 are obtained, together with HR‐TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon‐rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double‐layered capacitor (EDLC).  相似文献   
96.
The photo‐induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3‐hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc‐CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) are studied as well. The light‐induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo‐induced absorption (PIA) and light‐induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo‐excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long‐term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc‐CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed.  相似文献   
97.
Protein unfolding inside immobilized polymerosomes : One of the most interesting properties of polymeric vesicles is their remarkable stability against extreme temperatures and osmotic stress, and their longevity even under harsh environmental conditions. We have demonstrated, in an application on protein folding, that surface‐tethered polymerosomes are suitable for performing time‐resolved single molecule studies with encapsulated proteins, as illustrated here.

  相似文献   

98.
Whereas the cytostatic agents mer‐[RhX3(DMSO)(pp)] (X=Cl, Br; pp=phen, dpq) are considerably more potent than their facial isomers, this order is reversed for the analogous kinetically more inert IrIII polypyridyl complexes. The complexes induce specific apoptotic cell death in leukemia and lymphoma cells via the intrinsic mitochondrial pathway and cause negligible necrotic damage.

  相似文献   

99.
Human mitochondrial DNA (mtDNA) is located in discrete DNA-protein complexes, so called nucleoids. These structures can be easily visualized in living cells by utilizing the fluorescent stain PicoGreen®. In contrary, cells devoid of endogenous mitochondrial genomes (ρ0 cells) display no mitochondrial staining in the cytoplasm. A modified restriction enzyme can be targeted to mitochondria to cleave the mtDNA molecules in more than two fragments, thereby activating endogenous nucleases. By applying this novel enzymatic approach to generate mtDNA-depleted cells the destruction of mitochondrial nucleoids in cultured cells could be detected in a time course. It is clear from these experiments that mtDNA-depleted cells can be seen as early as 48 h post-transfection using the depletion system. To prove that mtDNA is degraded during this process, mtDNA of transfected cells was quantified by real-time PCR. A significant decline could be observed 24 h post-transfection. Combination of both results showed that mtDNA of transfected cells is completely degraded and, therefore, ρ0 cells were generated within 48 h. Thus, the application of a mitochondrially-targeted restriction endonuclease proves to be a first and fast, but essential step towards a therapy for mtDNA disorders.  相似文献   
100.
The full‐notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental stress cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE‐HD). Usually the full‐notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental stress cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full‐notch creep testing device with 12 individual sub‐stations, each equipped with individual electronic stress and temperature control and continuous online monitoring of the specimen elongation.  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