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排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
Boon Tiong Tan Siou Teck Chew Mook Seng Leong Ban Leong Ooi 《Microwave Theory and Techniques》2003,51(8):1906-1910
A dual-mode ring bandpass filter with two pairs of capacitors has been designed. The capacitors are used to control the location of the even- and odd-mode frequencies independently, allowing weak coupling for narrow-band filter design with realizable capacitance values. Theoretical expressions have been derived for these frequencies. A 4% bandwidth bandpass filter centered at 1.9 GHz was designed and tested with good agreement between theoretical and measured results. 相似文献
2.
A deterministic digital simulation model with finite sum of properly weighted sinusoids is used to simulate a frequency nonselective mobile channel with LOS component. Measurement data are used to optimise the parameters. Which are then used in the deterministic simulation model. The probability distribution and level cross rate (LCR) obtained from the measured data agree well with the analytical and simulation results 相似文献
3.
Kin Kit Fong Inn Shi Tan Henry Chee Yew Foo Man Kee Lam Adrian Chiong Yuh Tiong Steven Lim 《中国化学工程学报》2021,33(5):297-305
The rising production of produced water from oilfields had been proven to bring detrimental environmental effects. In this study, an efficient, recyclable, and environmental-friendly reduced graphene oxide immobilized κ-Carrageenan hydrogel composite(κCa GO) was fabricated as an alternative sorbent for crude oil-in-water demulsification. Polyethyleneimine(PEI) was employed to form a stable hydrogel composite. The conditions for the immobilization of graphene oxide(GO) on PEI-modified κ-Carrageenan(κC) beads were optimized appropriately. An immobilization yield of 77% was attained at 2% PEI, 2 h immobilization activation time, and p H6.5. Moreover, the synthesized κCa GO is capable of demulsification with an average demulsification efficiency of 70%. It was found that the demulsification efficiency increases with salinity and κCa GO dosage, and it deteriorates under alkaline condition. These phenomena can be attributed to the interfacial interactions between κCa GO and the emulsion. Furthermore, the κCa GO can be recycled to use for up to six cycles without significant leaching and degradation. As such, the synthesized κCa GO could be further developed as a potential sorbent substitute for the separation of crude oil from produced water. 相似文献
4.
This paper presents theoretical and experimental investigations on electroosmotic control of stream width in hydrodynamic
focusing. In the experiments, three liquids (aqueous NaCl, aqueous glycerol and aqueous NaCl) are introduced by syringe pumps
to flow side by side in a straight rectangular microchannel. External electric fields are applied on the two aqueous NaCl
streams. Under the same inlet volumetric flow rates, the applied electric fields are varied to control the interface positions
and consequently the width of the focused aqueous glycerol stream. The electroosmotic effect on the width of the aqueous glycerol
is measured using fluorescence imaging technique. The electroosmotic effect under different flow rates, different viscosity,
and aspect ratio are investigated. The results indicate that the electroosmotic effect on the pressure-driven flow becomes
weaker with the increase in flow rates, viscosity ratio or aspect ratio of the channel. The measured results of the focused
width of the non-conducting fluid agree well with the analytical model. 相似文献
5.
6.
Quantitative Proteomics Study Reveals Changes in the Molecular Landscape of Human Embryonic Stem Cells with Impaired Stem Cell Differentiation upon Exposure to Titanium Dioxide Nanoparticles
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Lei Pan Yew Mun Lee Teck Kwang Lim Qingsong Lin Xiuqin Xu 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(23)
The increasing number of nanoparticles (NPs) being used in various industries has led to growing concerns of potential hazards that NP exposure can incur on human health. However, its global effects on humans and the underlying mechanisms are not systemically studied. Human embryonic stem cells (hESCs), with the ability to differentiate to any cell types, provide a unique system to assess cellular, developmental, and functional toxicity in vitro within a single system highly relevant to human physiology. Here, the quantitative proteomics approach is adopted to evaluate the molecular consequences of titanium dioxide NPs (TiO2 NPs) exposure in hESCs. The study identifies ≈328 unique proteins significantly affected by TiO2 NPs exposure. Proteomics analysis highlights that TiO2 NPs can induce DNA damage, elevated oxidative stress, apoptotic responses, and cellular differentiation. Furthermore, in vivo analysis demonstrates remarkable reduction in the ability of hESCs in teratoma formation after TiO2 NPs exposure, suggesting impaired pluripotency. Subsequently, it is found that TiO2 NPs can disrupt hESC mesoderm differentiation into cardiomyocytes. The study unveils comprehensive changes in the molecular landscape of hESCs by TiO2 NPs and identifies the impact which TiO2 NPs can have on the pluripotency and differentiation properties of human stem cells. 相似文献
7.
Technological advancement has brought a whole new way of delivering financial services around the world. E-finance industry
in Malaysia has grown rapidly with the help of internet and conducting financial services are far easier now if compared to
last time. Internet provided a new medium or channel in delivering financial services. However, there are also risks and challenges
when using electronic finance. A total of 100 respondents had been targeted in completing this study. Survey method was utilized
in collecting respondent’s opinion and perception to test the variables. The target was companies which used electronic finance
in delivering their services. Interviews were also conducted and relevant tests conducted which provided evidence to support
the hypotheses for this study. It was found that e-finance was affected by security, revenue and cost dimensions, and technology
architecture with the adoption of global technology. 相似文献
8.
Current real-time collaborative application implementations use dedicated infrastructure to carry out all communication and synchronization activities. Specifically, they require all end nodes to communicate directly with and through the central server. In this paper, we investigate scenarios in which the most resource intensive functionality of continuous communication among collaborators to disseminate changes is decentralized, utilizing the end users themselves as relays. We observe that communication characteristics of real-time collaboration makes use of existing multicast mechanisms unsuitable. As collaborative editing sessions are typically long and repeated, it is possible to gather and leverage node behavior (their instabilities and frequency of sending updates) and communication links (latencies and average costs). Several criteria to determine the quality of a multicast tree can be identified: cost, latency and instability. In this paper, we analyze the complexity of the problem of finding optimal communication topologies, and propose approximate algorithms to optimize the same. We also consider the multiobjective problem in which we search for a topology that provides good trade-off between these sometimes conflicting measures. Validation of our proposed algorithms on numerous graphs shows that it is important to consider the multiobjective problem, as optimal solutions for one performance measure can be far from optimal for the other metrics. Finally, we briefly present an implementation of a communication library that uses the proposed algorithms to periodically adjust the dissemination tree. 相似文献
9.
S. Q. Wang Robert L. K. Tiong S. K. Ting D. Ashley 《Construction Management & Economics》2013,31(2):197-207
China is actively investigating ways to introduce project financing, specifically through the build-operate-transfer (BOT) scheme to meet the needs for the country's infrastructure and to be attractive to foreign investors and lenders. The advent of concession agreements, backed by new BOT laws, will be a positive move forward to achieving project-financed infrastructure projects. There are thus opportunities especially in the power sector for foreign investors. However, it is important to identify and manage the unique or critical risks associated with China's BOT projects. This is especially so after policies were introduced in late 1996 when the first state-approved BOT project, the US$650 million 2 × 350 megawatt (MW) coal-fired Laibin B Power Plant (Laibin B), was awarded. They include a competitive tendering process and 100% foreign ownership of the operating company. This paper is based on the findings from an international survey on risk management of BOT projects in developing countries, with emphasis on power projects in China. It discusses specifically the criticality of foreign exchange and revenue risks which include exchange rate and convertibility risk, financial closing risk, dispatch constraint risk and tariff adjustment risk. The measures for mitigating each of these risks are discussed also. 相似文献
10.
Mun Fai Loke Indresh Yadav Teck Kwang Lim Johan R. C. van der Maarel Lok-To Sham Vincent T. Chow 《International journal of molecular sciences》2022,23(6)
The presence of co-infections or superinfections with bacterial pathogens in COVID-19 patients is associated with poor outcomes, including increased morbidity and mortality. We hypothesized that SARS-CoV-2 and its components interact with the biofilms generated by commensal bacteria, which may contribute to co-infections. This study employed crystal violet staining and particle-tracking microrheology to characterize the formation of biofilms by Streptococcus pneumoniae and Staphylococcus aureus that commonly cause secondary bacterial pneumonia. Microrheology analyses suggested that these biofilms were inhomogeneous soft solids, consistent with their dynamic characteristics. Biofilm formation by both bacteria was significantly inhibited by co-incubation with recombinant SARS-CoV-2 spike S1 subunit and both S1 + S2 subunits, but not with S2 extracellular domain nor nucleocapsid protein. Addition of spike S1 and S2 antibodies to spike protein could partially restore bacterial biofilm production. Furthermore, biofilm formation in vitro was also compromised by live murine hepatitis virus, a related beta-coronavirus. Supporting data from LC-MS-based proteomics of spike–biofilm interactions revealed differential expression of proteins involved in quorum sensing and biofilm maturation, such as the AI-2E family transporter and LuxS, a key enzyme for AI-2 biosynthesis. Our findings suggest that these opportunistic pathogens may egress from biofilms to resume a more virulent planktonic lifestyle during coronavirus infections. The dispersion of pathogens from biofilms may culminate in potentially severe secondary infections with poor prognosis. Further detailed investigations are warranted to establish bacterial biofilms as risk factors for secondary pneumonia in COVID-19 patients. 相似文献