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   807篇
  免费   73篇
电工技术   18篇
化学工业   290篇
金属工艺   8篇
机械仪表   19篇
建筑科学   18篇
矿业工程   2篇
能源动力   25篇
轻工业   163篇
水利工程   4篇
石油天然气   4篇
无线电   44篇
一般工业技术   118篇
冶金工业   62篇
原子能技术   1篇
自动化技术   104篇
  2024年   2篇
  2023年   7篇
  2022年   16篇
  2021年   79篇
  2020年   31篇
  2019年   26篇
  2018年   37篇
  2017年   30篇
  2016年   37篇
  2015年   29篇
  2014年   43篇
  2013年   60篇
  2012年   53篇
  2011年   66篇
  2010年   41篇
  2009年   46篇
  2008年   49篇
  2007年   43篇
  2006年   32篇
  2005年   14篇
  2004年   12篇
  2003年   20篇
  2002年   16篇
  2001年   11篇
  2000年   7篇
  1999年   6篇
  1998年   12篇
  1997年   5篇
  1996年   4篇
  1995年   10篇
  1994年   3篇
  1993年   4篇
  1990年   2篇
  1989年   3篇
  1988年   5篇
  1987年   3篇
  1986年   2篇
  1985年   1篇
  1984年   3篇
  1982年   2篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   4篇
  1975年   1篇
排序方式: 共有880条查询结果,搜索用时 31 毫秒
11.
Novel antiviral nanotherapeutics, which may inactivate the virus and block it from entering host cells, represent an important challenge to face viral global health emergencies around the world. Using a combination of bioorthogonal copper-catalyzed 1,3-dipolar alkyne/azide cycloaddition (CuAAC) and photoinitiated thiol–ene coupling, monofunctional and bifunctional peptidodendrimer conjugates were obtained. The conjugates are biocompatible and demonstrate no toxicity to cells at biologically relevant concentrations. Furthermore, the orthogonal addition of multiple copies of two different antiviral peptides on the surface of a single dendrimer allowed the resulting bioconjugates to inhibit Herpes simplex virus type 1 at both the early and the late stages of the infection process. The presented work builds on further improving this attractive design to obtain a new class of therapeutics.  相似文献   
12.
A molecular distillation plant, built particularly to increase the separation efficiency and to obtain safer working conditions, was tested to remove cholesterol from anhydrous butter and lard. A preliminary experiment was carried out with butter to evaluate the fractionation obtained at temperatures between 190 and 250°C and residual pressures between 10−3 and 10−4 torr. A second experiment was carried out at 185°C and at the maximum operational vacuum, evaluating the fractionation achieved within a time scale between 30 and 180 min. Cholesterol was almost completely removed during the second hour with minimal loss of low-molecular weight triglycerides. An experiment was carried out with lard at 250°C and maximum achievable operational vacuum (10−4 Torr), lasting approximately 6 h, and cholesterol was removed almost completely during the second hour without significant modifications in the triglyceride composition. This situation remained constant throughout the duration of the test.  相似文献   
13.
We propose a stochastic disease model where vaccination is included and such that the immunity is permanent. The existence, uniqueness, and positivity of the solution and the stability of the disease-free equilibrium are studied.  相似文献   
14.
This paper reports upon the research into the influence of sodium ions on C12A7. The actual research work consisted in synthesizing C12A7, treated with the sodium ions as Na2CO3, within the sodium concentration range of up to 25% Na2O by weight in C12A7. The resultant combinations have been identified by the X-ray analysis, the infra-red spectroscopy and the quantitative chemical analysis.

The identification procedure together with the analysis of free CaO content in the products of C12A7 sodium synthesis gave evidence that sodium which is introduced into the researched amount of C12A7 up to 10% Na2O by weight, contributes to the formation of the ever increasing phase of the solid solutions of Na2O in C3A. The continued increase of the sodium volume ( 15% Na2O by weight ) makes it resolve gradually into sodium aluminate β -NA and free CaO.  相似文献   

15.
The influence of the olive paste malaxation time on the composition and the industrial output of oil was investigated. To this purpose, three Italian olive varieties (Leccino, Dritta, Caroleo) were processed with a centrifugal system for six malaxation periods (0, 15, 30, 45, 60 and 75 min). The concentrations of the majority of the oil constituents changed during the malaxation. However, these changes were not significant for all of them: the contents of β‐carotene, the major xanthophylls, chlorophylls a and b, pheophytins a and b in the oils increased progressively with increasing malaxing times, whereas the contents of simple and hydrolysable phenols (secoiridoid derivatives), o‐diphenols and total phenols decreased. A significant increase in total volatiles and green volatiles of the lipoxygenase cascade (C6 aldehydes, C6 alcohols, C5 alcohols and C5 carbonyls) was detected. An opposite trend was observed for the green C6 esters. As a result, the global analytical quality, flavour, aroma and shelf‐life of the oils were negatively affected. The oil yield increased substantially up to 45 min of paste malaxation times. Beyond 60 min, the yields tended to decrease.  相似文献   
16.
The positional distribution of fatty acids (FA) in triacylglycerols (TAG) of 47 virgin olive oils from diverse cultivars grown in distinct areas of North‐Eastern Italy was studied. Few data were previously available on oils from these geographical areas. The effects of climatic and geographical conditions on the stereospecific distribution of TAG in olive oil were confirmed. Moreover, the results of the stereospecific analysis were used to evaluate the preferential esterification position of each FA on the basis of the degree of unsaturation and the chain length. The data of the stereospecific analysis of olive oil TAG can contribute to the determination of the selectivity of olive fruit acyltransferases for distinct FA.  相似文献   
17.
The purpose of this study is to analyze the political economy of food-water security in the water-scarce Middle East and North Africa region. The study deploys the lens of virtual water trade to determine how the region's economies have met their rising food-water requirements over the past three decades. It is shown that the region's water and food security currently depend to a considerable extent on water from outside the region, ‘embedded’ in food imports and accessed through trade. The analysis includes blue (surface and groundwater) and green water resources.  相似文献   
18.
This paper presents a new hardware-oriented approach for the extraction of disparity maps from stereo images. The proposed method is based on the herein named Adaptive Census Transform that exploits adaptive support weights during the image transformation; the adaptively weighted sum of SADs is then used as the dissimilarity metric. Quality tests show that the proposed method reaches significantly better accuracy than alternative hardware-oriented approaches. To demonstrate the practical hardware feasibility, a specific architecture has been designed and its implementation has been carried out using a single FPGA chip. Such a VLSI implementation allows a frame rate up to 68 fps to be reached for 640 × 480 stereo images, using just 80,000 slices and 32 RAM blocks of a Virtex6 chip.  相似文献   
19.
Background Supporting medical decision making is a complex task, that offers challenging research issues to Artificial Intelligence (AI) scientists. The Case-based Reasoning (CBR) methodology has been proposed as a possible means for supporting decision making in this domain since the 1980s. Nevertheless, despite the variety of efforts produced by the CBR research community, and the number of issues properly handled by means of this methodology, the success of CBR systems in medicine is somehow limited, and almost no research product has been fully tested and commercialized; one of the main reasons for this may be found in the nature of the problem domain, which is extremely complex and multi-faceted. Materials and methods In this environment, we propose to design a modular architecture, in which several AI methodologies cooperate, to provide decision support. In the resulting context CBR, originally conceived as a well suited reasoning paradigm for medical applications, can extend its original roles, and cover a set of additional tasks. Results and conclusions As an example, in the paper we will show how CBR can be exploited for configuring the parameters relied upon by other (reasoning) modules. Other possible ways of deploying CBR in this domain will be the object of our future investigations, and, in our opinion, a possible research direction for people working on CBR in the health sciences.  相似文献   
20.
Nowadays, micro components have to fulfill rising optical requirements for different scientific and industrial fields like astronomy, medicine or multimedia. For this purpose, advanced miniaturized chip-cameras are produced for the microsystems engineering market. The assembly and joining technologies play a very important role in the production of these micro components. Several challenges are associated with the joining of chip-cameras. In this study, the application of the soldering technology has been considered in order to face these challenges. Two joining technologies have been investigated: active soldering and transient liquid phase (TLP) bonding. Both soldering processes have shown a big potential for hybrid microsystems joining in previous studies. For both processes, soldering alloys and parameters have been conceived in order to fulfill the joining requirements of the micro camera components. For instance, the joining temperature represents a major challenge because the chip-camera consists of a plastic material, polymethyl methacrylate (PMMA). Therefore, particular attention has been directed to the soldering as well as to the coating temperature. The experimental investigations concerning the solders application through physical vapor deposition (PVD) have been supported by finite element method (FEM) simulations. The analysis of  the temperature distribution in the micro components during the coating process was the focus of  the calculations. Possible undesirable local overheated areas of the chip-camera components can be detected through simulation.
Tatyana KashkoEmail:
  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