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   1357篇
  免费   62篇
电工技术   21篇
综合类   2篇
化学工业   372篇
金属工艺   43篇
机械仪表   22篇
建筑科学   77篇
矿业工程   3篇
能源动力   48篇
轻工业   78篇
水利工程   13篇
石油天然气   2篇
无线电   82篇
一般工业技术   246篇
冶金工业   70篇
原子能技术   4篇
自动化技术   336篇
  2023年   19篇
  2022年   42篇
  2021年   63篇
  2020年   36篇
  2019年   31篇
  2018年   41篇
  2017年   43篇
  2016年   54篇
  2015年   62篇
  2014年   55篇
  2013年   95篇
  2012年   82篇
  2011年   114篇
  2010年   75篇
  2009年   71篇
  2008年   90篇
  2007年   70篇
  2006年   61篇
  2005年   43篇
  2004年   31篇
  2003年   22篇
  2002年   23篇
  2001年   17篇
  2000年   14篇
  1999年   31篇
  1998年   22篇
  1997年   12篇
  1996年   3篇
  1995年   7篇
  1994年   13篇
  1993年   5篇
  1990年   7篇
  1989年   3篇
  1988年   3篇
  1987年   2篇
  1986年   4篇
  1985年   6篇
  1984年   3篇
  1983年   5篇
  1982年   5篇
  1981年   4篇
  1979年   4篇
  1978年   3篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1958年   2篇
排序方式: 共有1419条查询结果,搜索用时 31 毫秒
11.
(1) Background: Placental immune cells are playing a very important role in a successful placentation and the prevention of pregnancy complications. Macrophages dominate in number and relevance in the maternal and the fetal part of the placenta. The evidence on the polarization state of fetal and maternal macrophages involved in both, healthy and pregnancy-associated diseases, is limited. There is no representative isolation method for the direct comparison of maternal and fetal macrophages so far. (2) Material and Methods: For the isolation of decidual macrophages and Hofbauer cells from term placenta, fresh tissue was mechanically dissected and digested with trypsin and collagenase A. Afterwards cell enrichment was increased by a Percoll gradient. CD68 is represented as pan-macrophage marker, the surface markers CD80 and CD163 were further investigated. (3) Results: The established method revealed a high cell yield and purity of the isolated macrophages and enabled the comparison between decidual macrophages and Hofbauer cells. No significant difference was observed in the percentage of single CD163+ cells in the distinct macrophage populations, by using FACS and immunofluorescence staining. A slight increase of CD80+ cells could be found in the decidual macrophages. Considering the percentage of CD80+CD163 and CD80CD163+ cells we could not find differences. Interestingly we found an increased number of double positive cells (CD80+CD163+) in the decidual macrophage population in comparison to Hofbauer cells. (4) Conclusion: In this study we demonstrate that our established isolation method enables the investigation of decidual macrophages and Hofbauer cells in the placenta. It represents a promising method for direct cell comparison, enzyme independently, and unaffected by magnetic beads, to understand the functional subsets of placental macrophages and to identify therapeutic targets of pregnancy associated diseases.  相似文献   
12.
13.
We present an interdigitated back‐contact silicon heterojunction system designed for liquid‐phase crystallized thin‐film (~10 µm) silicon on glass. The preparation of the interdigitated emitter (a‐Si:H(p)) and absorber (a‐Si:H(n)) contact layers relies on the etch selectivity of doped amorphous silicon layers in alkaline solutions. The etch rates of a‐Si:H(n) and a‐Si:H(p) in 0.6% NaOH were determined and interdigitated back‐contact silicon heterojunction solar cells with two different metallizations, namely Al and ITO/Ag electrodes, were evaluated regarding electrical and optical properties. An additional random pyramid texture on the back side provides short‐circuit current density (jSC) of up to 30.3 mA/cm2 using the ITO/Ag metallization. The maximum efficiency of 10.5% is mainly limited by a low of fill factor of 57%. However, the high jSC, as well as VOC values of 633 mV and pseudo‐fill factors of 77%, underline the high potential of this approach. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
14.
Amorphous solids are potential candidates for room temperature applications, such as structural materials, due to their outstanding mechanical properties. For the first time, the local atomic dynamics of amorphous metallic nanorods are spatially resolved at room temperature using electron microscopy. Methodologically, quasi-equilibrium conditions are verified by two-time correlation functions. FeNiP is chosen as a suitable model system since a bamboo structure forms upon electrodeposition into nanotubular confinement, consisting of thin Fe-rich and Ni-rich amorphous layers. Therefore, the present nano-glassy structure allows studying the glass dynamics of two glassy phases at once, at the same time avoiding any preparation-related structural artifacts of the intrinsically electron-transparent samples. By comparing the local atomic mobility with the local composition and the local structural information of the glassy phases, correlations between medium-range order and time scales of heterogeneous glassy dynamics are consistently obtained.  相似文献   
15.
Silage fermentation of minced fish and fish offal after inoculation with cereals prefermented with Pediococcus acidilactici and Lactobacillus plantarum initiates a rapid fall in pH to below 4.5 within 30 h, and the content of competing gram-negative fermenters and fish pathogens, such as Vibrio anguillarum and Aeromonas salmonicida, is eliminated. The addition of 0.1% sorbic acid inhibits the growth of yeasts during the initial fermentation period and during storage but does not affect the lactic acid fermentation. Degradation of nitrogen components proceeds during storage and is manifested as an increase in volatile basic nitrogen compounds, amino acids and peptides. These substances increase the pH and/or force the bacteria to produce more acid. The rate of production of these basic substances is mainly temperature-dependent and cannot be attributed to microbial activity. The proteolytic activity is mainly caused by tissue proteases (e.g., cathepsins) and, to a lower degree, by gut proteases. It is doubtful whether fish fermentation can be utilised on an industrial scale without improving the technique. Such improvements consist of the selection and use of psychotrophic lactic acid fermenters and commercially acceptable inhibitors of proteolytic activity and yeast growth.  相似文献   
16.
The application of loop and data transformations to array and loop intensive programs is crucial to obtain a good performance. Designers often apply these transformations manually or semi-automatically. For the class of static affine programs, automatic methods exist for proving the correctness of these transformations. Realistic multimedia systems, however, often contain constructs that fall outside of this class. We present an extension of a widening based approach to handle the most relevant of these constructs, viz. accesses to array slices, data dependent accesses and data dependent assignments, and report on some experiments with non-trivial applications.  相似文献   
17.
Providing incentives in providerless networks   总被引:1,自引:0,他引:1  
This paper explores the extension of a model for the operation of an ad hoc mobile network to more general providerless networks, such as peer-to-peer systems. The model incorporates incentives for users to act as transit nodes on multi-hop paths and to be rewarded with their own ability to send traffic. The paper explores some of the trust questions that arise in this problem space and conjectures that the very structure of a peer organisation may have some hidden benefits for trust re-enforcement, that have not been previously explored (to our knowledge).  相似文献   
18.
This paper reports fiber Bragg gratings (FBGs) inscribed in a small-core Ge-doped photonic crystal fibers with a UV laser and a Talbot interferometer. The responses of such FBGs to temper- ature, strain, bending, and transverse-loading were systematically investigated. The Bragg wavelength of the FBGs shifts toward longer wavelengths with increasing temperature, tensile strain, and transverse-loading. The bending and transverse- loading properties of the FBGs are sensitive to the fiber orientations.  相似文献   
19.
EMPIRE10 (Evaluation of Methods for Pulmonary Image REgistration 2010) is a public platform for fair and meaningful comparison of registration algorithms which are applied to a database of intrapatient thoracic CT image pairs. Evaluation of nonrigid registration techniques is a nontrivial task. This is compounded by the fact that researchers typically test only on their own data, which varies widely. For this reason, reliable assessment and comparison of different registration algorithms has been virtually impossible in the past. In this work we present the results of the launch phase of EMPIRE10, which comprised the comprehensive evaluation and comparison of 20 individual algorithms from leading academic and industrial research groups. All algorithms are applied to the same set of 30 thoracic CT pairs. Algorithm settings and parameters are chosen by researchers expert in the configuration of their own method and the evaluation is independent, using the same criteria for all participants. All results are published on the EMPIRE10 website (http://empire10.isi.uu.nl). The challenge remains ongoing and open to new participants. Full results from 24 algorithms have been published at the time of writing. This paper details the organization of the challenge, the data and evaluation methods and the outcome of the initial launch with 20 algorithms. The gain in knowledge and future work are discussed.  相似文献   
20.
As intended by its name, physically unclonable functions (PUFs) are considered as an ultimate solution to deal with insecure storage, hardware counterfeiting, and many other security problems. However, many different successful attacks have already revealed vulnerabilities of certain digital intrinsic PUFs. This paper demonstrates that legacy arbiter PUF and its popular extended versions (i.e., feed-forward and XOR-enhanced) can be completely and linearly characterized by means of photonic emission analysis. Our experimental setup is capable of measuring every PUF internal delay with a resolution of 6 ps. Due to this resolution, we indeed require only the theoretical minimum number of linear independent equations (i.e., physical measurements) to directly solve the underlying inhomogeneous linear system. Moreover, it is not required to know the actual PUF responses for our physical delay extraction. We present our practical results for an arbiter PUF implementation on a complex programmable logic device manufactured with a 180 nm process. Finally, we give an insight into photonic emission analysis of arbiter PUF on smaller chip architectures by performing experiments on a field programmable gate array manufactured with a 60 nm process.  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