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   1209篇
  免费   36篇
电工技术   105篇
综合类   5篇
化学工业   268篇
金属工艺   19篇
机械仪表   33篇
建筑科学   32篇
能源动力   81篇
轻工业   63篇
水利工程   3篇
无线电   108篇
一般工业技术   268篇
冶金工业   80篇
原子能技术   38篇
自动化技术   142篇
  2023年   3篇
  2022年   12篇
  2021年   19篇
  2020年   10篇
  2019年   19篇
  2018年   19篇
  2017年   13篇
  2016年   30篇
  2015年   16篇
  2014年   37篇
  2013年   79篇
  2012年   52篇
  2011年   48篇
  2010年   59篇
  2009年   52篇
  2008年   62篇
  2007年   53篇
  2006年   40篇
  2005年   56篇
  2004年   36篇
  2003年   40篇
  2002年   29篇
  2001年   34篇
  2000年   21篇
  1999年   26篇
  1998年   36篇
  1997年   31篇
  1996年   40篇
  1995年   22篇
  1994年   22篇
  1993年   30篇
  1992年   14篇
  1991年   22篇
  1990年   12篇
  1989年   16篇
  1988年   7篇
  1987年   11篇
  1986年   16篇
  1985年   16篇
  1984年   7篇
  1983年   11篇
  1982年   9篇
  1981年   9篇
  1980年   8篇
  1979年   5篇
  1978年   7篇
  1977年   7篇
  1976年   8篇
  1974年   4篇
  1972年   2篇
排序方式: 共有1245条查询结果,搜索用时 93 毫秒
61.
The feasibility of applying a polyethylene (PE) sponge as a biomass carrier in an anaerobic ammonium oxidation (anammox) reactor and its nitrogen removal performance were also investigated. Experiments were carried out in an up-flow column reactor with synthetic inorganic wastewater. Experimental results indicate that reactor containing PE sponge biomass carriers showed a high nitrogen removal capability and exhibited stable performance. In addition, the reactor with 8 strips PE sponge as biomass carrier exhibited greater adaptation capacity compared to that with 6 strips and could achieve a high TN removal rate within a very short period. The ratio of NO2-N removal and NO3-N production to NH4-N removal for the reactor was 1.26:0.21. Furthermore, to investigate the bacterial composition of the mature community, 16S rRNA sequences were amplified by PCR and analyses were conducted using DNA databases. Results showed that a new kind of anammox microorganism (Kumadai-1) was the dominant species in the reactor when using PE sponge as a biomass carrier.  相似文献   
62.
63.
Mohri S  Kasai T  Abe Y  Shi YW  Matsuura Y  Miyagi M 《Applied optics》2002,41(7):1251-1255
We propose sealing techniques for medical hollow fibers to protect the inner surface of fibers from debris or water that scatters from targets. First, hollow fibers are sealed with a film of polymer that is easily formed by use of a dipping technique. The transmission loss of 20-microm-thick sealing film was 0.2 dB for Er:YAG laser light, and the maximum energy that is available for the film was 180 mJ. Second, a sealed glass cap was applied to the output end of hollow fiber. The silica-glass cap with a wall thickness of 400 microm shows a transmission loss of 0.5 dB and was not damaged by radiation of 400-mJ energy pulses.  相似文献   
64.
The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.  相似文献   
65.
Abstract— Thin‐film transistors (TFTs) are field‐effect transistors that can be used to create large‐scale‐integrated (LSI) circuits. The combination of high‐performance TFTs and transfer technology of the TFTs has the potential to foster the rise of a new flexible microelectronics industry. This paper discusses the current status of flexible microelectronics, using a TFT fingerprint sensor (FPS) as an example. Technology used in active‐matrix displays can easily be applied to the TFT FPS. TFT technology should not be confined to the display industry; its use should be expanded into the semiconductor industry. With the result presented in this paper, we declare a new era of flexible microelectronics open.  相似文献   
66.
A pneumatically actuated silicon microvalve applicable to integrated microfluidic systems is presented. All the ports of this microvalve are in-channel, and connectable to any surface fluid channels in microfluidic systems. This microvalve controls fluid flow by means of the controlled gap between glass and silicon diaphragm actuated by a control pressure. In addition, the diaphragm is also deformed by the outlet pressure of the microvalve. Due to the feature, this microvalve shows saturation of flow rate like MOSFETs operated at saturation region. The fabricated microvalve device was evaluated focusing on analogous relationship between MOSFET and the microvalve. Fluids such as air and DI-water were well controlled by the control pressure. Fluid starts to flow in the microvalve when the control pressure exceeds its "threshold pressure." Hysteresis due to sticking of diaphragm was not observed in the characteristics. Air flow rate of the microvalve was gradually saturated with the increasing of the outlet pressure as expected. Through the evaluation, analogous relationship between this microvalve and MOSFET has been experimentally demonstrated.  相似文献   
67.
68.
Inside-out vesicles of plasma membranes prepared from a plant source were used as models to investigate effects of centrifugal forces on separations of early and late endosome populations by aqueous two-phase partition. Endosome subpopulations were resolved readily by preparative free-flow electrophoresis where acidification of the interiors of late endosomes occurred upon addition of ATP to activate a proton translocating ATPase. The resultant increased diffusion potential provided for a surface difference between late and early endosomes to permit electrophoretic separation. With the plant membranes, unincubated inside-out plasma membrane vesicles modeled early endosomes, whereas inside-out vesicles incubated with 1 mM ATP modeled late endosomes. A latent, 2,4-dichlorophenoxyacetic acid (2,4-D)-(auxin)-stimulated NADH:protein disulfide reductase measured spectrophotometrically was used as an enzymatic marker for both populations of inside-out vesicles. Phase partition behavior of each population was quantitated using total protein as the parameter.  相似文献   
69.
Among 11 subtypes of heterotrimeric G-protein gamma-subunit, gamma1 (rod), gamma8 (cone) and gamma11 are modified with farnesyl while the others are modified with geranylgeranyl at the C-terminus. To understand the role of specific isoprenylation (farnesylation) of retinal transducin, we examined how and to what extent the type of isoprenyl group affects transducin-beta gamma (beta1 gamma1) functions such as interactions with membranes, Galpha/receptor, and effectors. To this end, the C-terminal farnesylation signal sequence (CVIS) of gamma1 was replaced by a geranylgeranylation signal (CVIL), and the resultant mutant (S74L) or wild-type (WT) gamma1 was coexpressed with beta1 in the baculovirus-Tn5 insect cell system. Both gamma1WT and gamma1S74L expressed as a beta gamma complex were mixtures modified with farnesyl and geranylgeranyl groups. The ratio of farnesyl to geranylgeranyl in preparations of beta1 gamma1WT and beta1 gamma1S74L purified from the Tn5 cell membrane fraction was about 1:2 and 1:6, respectively. These two forms of recombinant beta1 gamma1 and retinal beta1 gamma1 were different in their abilities to associate with rod outer segment membranes with the following rank order: beta1 gamma1S74L > beta1 gamma1WT > retinal beta1 gamma1. Functionally, beta1 gamma1S74L was the most potent to promote pertussis toxin-catalyzed ADP ribosylation of transducin-alpha (Talpha), to stimulate metarhodopsin II-catalyzed GTPgammaS-binding reaction to Talpha and to modulate adenylyl cyclase and phospholipase C activities. All of the beta1 gamma1 functions absolutely required the isoprenylation of the gamma-subunit. As for the interaction with Goalpha and adenylyl cyclase, predominantly geranylgeranylated beta1 gamma1S74L was less effective than geranylgeranylated beta1 gamma2 purified from bovine brain. These results demonstrate that the properties of Gbeta gamma are strongly affected by the type of functionally indispensable isoprenylation in addition to the amino acid sequence of Ggamma. The relative contribution of the two factors depends on proteins with which Gbeta gamma interacts.  相似文献   
70.
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