首页 | 官方网站   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   3888篇
  免费   216篇
  国内免费   28篇
工业技术   4132篇
  2024年   9篇
  2023年   60篇
  2022年   175篇
  2021年   207篇
  2020年   166篇
  2019年   206篇
  2018年   256篇
  2017年   193篇
  2016年   228篇
  2015年   142篇
  2014年   199篇
  2013年   398篇
  2012年   225篇
  2011年   250篇
  2010年   188篇
  2009年   162篇
  2008年   130篇
  2007年   89篇
  2006年   99篇
  2005年   60篇
  2004年   58篇
  2003年   46篇
  2002年   53篇
  2001年   28篇
  2000年   31篇
  1999年   18篇
  1998年   66篇
  1997年   39篇
  1996年   42篇
  1995年   28篇
  1994年   27篇
  1993年   26篇
  1992年   24篇
  1991年   19篇
  1990年   14篇
  1989年   19篇
  1988年   14篇
  1987年   13篇
  1986年   6篇
  1985年   12篇
  1984年   10篇
  1983年   9篇
  1982年   8篇
  1981年   10篇
  1980年   10篇
  1979年   8篇
  1978年   9篇
  1977年   8篇
  1976年   13篇
  1971年   6篇
排序方式: 共有4132条查询结果,搜索用时 15 毫秒
991.
In routine clinical diagnostics, peptide biomarkers are most commonly quantified using immunological techniques but these methods often lack sensitivity and/or specificity. Hence, quantitative mass spectrometry detection is desirable as an alternative diagnostic tool. To date, quantitative mass spectrometry is mostly based on ESI‐MS coupled to LC, requiring highly sophisticated instrumentation and knowledge and is time consuming and expensive. In contrast, MALDI‐TOF‐MS is a very simple, sensitive and rapid method for the detection of peptide biomarkers. However, the infeasibility of absolute quantification has been a tremendous handicap to the use of MS in stable clinical diagnostics. Here, we describe the development of a technical platform based on ClinProt particles and heavy‐isotope internal peptide standards for the fast and reliable preparation of samples. This combines the advantages of MALDI‐TOF as a read‐out system with absolute quantitation of peptide biomarkers. As a proof‐of‐concept, this platform was successfully employed for the absolute determination of the concentration of the highly abundant serum peptide des‐Ala‐Fibrinopeptide A in 45 serum samples from healthy donors. Such technology essentially contributes to the development of a stable MALDI‐TOF‐MS‐based clinical assay.  相似文献   
992.
The seven engineering degrees of the Higher Technical School of Design Engineering (ETSID), Technical University of Valencia, include in their formation programs, subjects, and laboratory projects to instruct students in the aspects of the design, development, and validation of applications for process control, automation, industrial informatics, and embedded systems. Moreover, the authors participate in European projects of education such as the International Network of Embedded System (INES) and the European Project Semester (EPS), where exchange students remotely perform the first phase of their projects at ETSID from their home universities. To significantly reduce the cost of installing a huge number of real prototypes in labs and to fulfill the distance requirements of the exchange students, a remote laboratory architecture, i.e., simPROCes, has been designed. simPROCes not only permits the teleoperation of simulators/real prototypes but also allows that complete control applications be remotely tested and validated. simPROCes is precisely specified to be independent of the model of computer, data acquisition card, programming language, and operating system, and is transparent to the programmer and easy to use. This system is useful both for the education and development of control application purposes. A water tank process shows the installation procedure of simPROCes to test and validate control applications. The experience of applying simPROCes in the electronic engineering degree and within the framework of INES and EPS has been successfully rated by student surveys.  相似文献   
993.
An idea that improves the wettability over the surfaces of a cylindrical dehumidifier channel was proposed and experimentally proved. Fibrous sheets were attached to the inner surfaces of the channel. The capillary effect of fibers sustains the complete wetting of the heat and mass transfer surfaces. The air to be dehumidified and cooled flows upward in the annulus space between the two layers of fibrous sheets, which are saturated with the downward flowing desiccant solution. The permeability of the fibrous sheet was determined experimentally. It was 2.43 × 10?10 m2. The measured solution flow rate due to the capillary suction of the sheets was Γin,min = 1.12 kg/h m. The liquid desiccant tested was H2O/CaCl2 with salt concentration ratios ranging from 35 to 40%. The measured distribution of the solution flow rate along the circumference of the sheets at the outlet showed 5% deviation from the average flow rate. This is a good indication for the good wettability of walls inside the dehumidifier.Feeding the solution by this mechanism has many advantages over spray feeding. Beside sustaining complete surface wetting, it also prevents channel blockage with solution, which is a main factor in increasing the air pressure drop. About 95% of the air pressure drop is saved in this study by avoiding these problems. A simple theoretical model for the heat and mass transfer processes inside the dehumidifier was developed and experimentally validated. In general, there is good agreement between the predicted and measured data. The developed model was utilized to study the effect of the different parameters on the dehumidifier performance. For a 1 m height dehumidifier with an inlet specific humidity and air temperature of 0.0234 kgv/kga, and 35 °C, respectively, the predicted outlet air specific humidity was 0.0102 kgv/kgk and the corresponding outlet air temperature was 27.4 °C. The inlet solution temperature and salt concentration were 25 °C and 40%, respectively.  相似文献   
994.
This paper describes the development of a Web-based integrated system for collaborative product development evolving from marketing analysis to prototype generation. The proposed system encompasses a marketing information system (MIS), a human resources management (HRM) system, a supply-chain management (SCM) system, a communication media, an integrated product design studio, a user interface and databases. It enables project planners, marketing analysts, designers, suppliers, and manufacturing planners to work at the early stages to reduce any unnecessary wasted time, resources, and costs, thus increasing the total product quality, maximising the organisation resources used, and reducing the total product cost and product lead time to better face global competition. The tangible advantage of implementing this system is that it provides an integrated environment for total product development from concept to realisation. Therefore, an efficient product development process is generated. One case study is demonstrated and discussed to validate the proposed system.  相似文献   
995.
996.
Besides their other obvious advantages over conventional ultrasonic sensors, laser interferometers offer optical diffraction limited apertures that are far smaller than the acoustic wavelength in the specimen under inspection. This unique feature can be exploited for the purposes of super-resolution near-field acoustic microscopy, which detects the rapidly decaying evanescent vibrations produced by surface and near-surface scatterers such as small fatigue cracks, pores, anomalous grains, etc. However, higher resolution also means higher sensitivity to inherent microscopic material inhomoge-neities. In this paper, experimental results are presented for the incoherent material noise in 2024 aluminum and Ti-6Al-4V titanium alloys at two different nominal frequencies of 5 and 10 MHz. It is shown that the incoherent grain noise significantly increases as the illuminated spot size decreases. Above the acoustic wavelength, the observed phenomenon is mainly due to the increasing sensitivity of the receiver to propagating scattered waves generated in the interior of the specimen. Below the acoustic wavelength, the further increasing material noise is mainly due to evanescent vibrations caused by nearby scatterers.  相似文献   
997.
A series of medium-scale and large-scale triaxial and unconfined compression tests was conducted in order to evaluate the strength and deformation characteristics and small strain properties of undisturbed well-graded gravelly soils retrieved from three tunnel excavation sites in Toyama prefecture, Japan. Undisturbed gravelly soils were taken by means of a new sampling method using thick water-soluble polymer solutions. The strength and deformation characteristics were evaluated mainly by performing sustained loading and large amplitude unloading and reloading cycles during otherwise monotonic loading at a constant strain rate in drained triaxial compression tests. During isotropic consolidation and shearing, at several stress states, eleven very small vertical cycles were applied to evaluate the quasi-elastic deformation property at small strain levels around 0.001% by static measurement. Dynamic measurements using a pair of accelerometers attached to the side surface of the specimen and wave sources attached to the top cap were also conducted at the same stress levels as static measurements in a single test. Several effects including grading characteristics and pressure level on the difference between the moduli measured statically and dynamically were discussed. The relationship between the small strain and strength properties of undisturbed gravelly soils was evaluated. The small strain properties of air-dried dense Toyoura sand in large-scale triaxial compression tests were also investigated in this study to compare the results of undisturbed gravelly soils.  相似文献   
998.
The present study was conducted to explore the occurrence of mycotoxins in commercial baby foods in Doha-Qatar. LCMS/MS- and HPLC-based analysis of baby food (n = 67) for 12 mycotoxins confirmed the presence of aflatoxin M1 (AFM1, 33%), ochratoxin A (OTA, 31%), deoxynivalenol (DON, 27%), aflatoxin B1 (AFB1, 22%), fumonisin B2 (FB2, 10%), zearalenone (ZEN, 4%) and T-2 toxin (2%). Noodles exhibited the maximum contamination percentage, with 33% of the samples being contaminated above the EU maximum limits, for at least one mycotoxin. Among the multi-grain flake samples, up to 28% and for the milk and milk-based-cereal samples, 14% contained at least one mycotoxin above the EU maximum limits. From all cereal-based food samples, 22%, 5%, 2% and 2% were concurrently contaminated with 2, 3, 4 and 5 mycotoxins, respectively. The occurrence of toxicological important mycotoxins in Qatari market warrants the implementation of strict regulatory limits to protect human health.  相似文献   
999.
We propose a dynamic joint scheduling and call admission control (CAC) scheme for service classes defined in IEEE 802.16 standard. Using priority functions, equipped with service weights and service arrival rates, the proposed scheduling scheme differentiates service classes from each other. Based on obtained priority values, we first allocate the achievable bandwidth proportionally. Within individual service classes, we then use appropriate local schedulers to transmit packets accordingly. Moreover, instead of immediate admitting or blocking a new connection request, the proposed CAC scheme computes the average transmission rate that can be allocated to that connection during a time interval. The connection is admitted if its required rate is satisfied while at the same time QoS requirements of ongoing connections are not violated. Our numerical results demonstrate the effectiveness of the proposed schemes compared to the other schemes in the literature.  相似文献   
1000.
The examination of the existing relationships between nanoindentation responses and tribological properties of the nanostructured CrN, Cr(CN), and (CrTi)N coatings was the matters to be considered in this research. A cathodic arc physical vapor deposition machine was therefore implemented to apply the chosen coatings on the DIN 1.2510 tool steel substrate. Moreover, an X-ray diffraction and a field emission scanning electron microscope were utilized in order to show the features regarding microstructure and morphology of these very coatings. The mechanical and tribological behavior of the coatings was expected to be assessed with the use of a nanoindentation and pin-on-disc wear tests. According to the obtained result, the wear resistance and hardness value of the (CrTi)N coating were proved to be much better than those of the CrN and Cr(CN). Linear equations were proposed between wear rate/hardness and friction coefficient/hardness to evaluate the correlation between mechanical and tribological properties. The presence of a quadratic equation between the friction coefficient and the plastic deformation index was also discovered.  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-23

京公网安备 11010802026262号