全文获取类型
收费全文 | 83568篇 |
免费 | 995篇 |
国内免费 | 406篇 |
专业分类
电工技术 | 772篇 |
综合类 | 2317篇 |
化学工业 | 11402篇 |
金属工艺 | 4763篇 |
机械仪表 | 3013篇 |
建筑科学 | 2157篇 |
矿业工程 | 562篇 |
能源动力 | 1099篇 |
轻工业 | 3570篇 |
水利工程 | 1266篇 |
石油天然气 | 341篇 |
无线电 | 9234篇 |
一般工业技术 | 16271篇 |
冶金工业 | 2628篇 |
原子能技术 | 255篇 |
自动化技术 | 25319篇 |
出版年
2021年 | 17篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 14452篇 |
2017年 | 13379篇 |
2016年 | 9961篇 |
2015年 | 605篇 |
2014年 | 232篇 |
2013年 | 190篇 |
2012年 | 3136篇 |
2011年 | 9404篇 |
2010年 | 8275篇 |
2009年 | 5538篇 |
2008年 | 6763篇 |
2007年 | 7775篇 |
2006年 | 113篇 |
2005年 | 1205篇 |
2004年 | 1122篇 |
2003年 | 1169篇 |
2002年 | 533篇 |
2001年 | 94篇 |
2000年 | 174篇 |
1999年 | 54篇 |
1998年 | 51篇 |
1997年 | 27篇 |
1996年 | 43篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 22篇 |
1988年 | 9篇 |
1975年 | 1篇 |
1969年 | 24篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 44篇 |
1964年 | 11篇 |
1963年 | 28篇 |
1962年 | 22篇 |
1961年 | 18篇 |
1960年 | 30篇 |
1959年 | 35篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
1949年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Ewelina Bik Lukasz Mateuszuk Jagoda Orleanska Malgorzata Baranska Stefan Chlopicki Katarzyna Majzner 《International journal of molecular sciences》2021,22(5)
Chloroquine (CQ) is an antimalarial drug known to inhibit autophagy flux by impairing autophagosome–lysosome fusion. We hypothesized that autophagy flux altered by CQ has a considerable influence on the lipid composition of endothelial cells. Thus, we investigated endothelial responses induced by CQ on human microvascular endothelial cells (HMEC-1). HMEC-1 cells after CQ exposure were measured using a combined methodology based on label-free Raman and fluorescence imaging. Raman spectroscopy was applied to characterize subtle chemical changes in lipid contents and their distribution in the cells, while the fluorescence staining (LipidTox, LysoTracker and LC3) was used as a reference method. The results showed that CQ was not toxic to endothelial cells and did not result in the endothelial inflammation at concentrations of 1–30 µM. Notwithstanding, it yielded an increased intensity of LipidTox, LysoTracker, and LC3 staining, suggesting changes in the content of neutral lipids, lysosomotropism, and autophagy inhibition, respectively. The CQ-induced endothelial response was associated with lipid accumulation and was characterized by Raman spectroscopy. CQ-induced autophagosome accumulation in the endothelium is featured by a pronounced alteration in the lipid profile, but not in the endothelial inflammation. Raman-based assessment of CQ-induced biochemical changes offers a better understanding of the autophagy mechanism in the endothelial cells. 相似文献
2.
Hansung Kim Md. Towfiq Tofail Ciby John 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(4):473-478
Among a variety of solar cell types, thin-film solar cells have been rigorously investigated as cost-effective and efficient solar cells. In many cases, flexible solar cells are also fabricated as thin films and undergo frequent stress due to the rolling and bending modes of applications. These frequent motions result in crack initiation and propagation (including delamination) in the thin-film solar cells, which cause degradation in efficiency. Reliability evaluation of solar cells is essential for developing a new type of solar cell. In this paper, we investigated the effect of layer delamination and grain boundary crack on 3D thin-film solar cells. We used finite element method simulation for modeling of both electrical performance and cracked structure of 3D solar cells. Through simulations, we quantitatively calculated the effect of delamination length on 3D copper indium gallium diselenide (CIGS) solar cell performance. Moreover, it was confirmed that the grain boundary of CIGS could improve the solar cell performance and that grain boundary cracks could decrease cell performance by altering the open circuit voltage. In this paper, the investigated material is a CIGS solar cell, but our method can be applied to general polycrystalline solar cells. 相似文献
3.
Joalet Dalene Steenkamp Wouter Gideon Bam Sello Peter Tsebe 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(11):2422-2427
Benchmarking is a tool available to furnace operators to evaluate their tap-hole life-cycle management practices against those of their peers. It allows furnace operators to challenge their own practices in order to increase furnace utilization. To facilitate the benchmarking process, it is necessary to define the variables to be considered and how they relate to one another. This article develops, from the literature and industry interviews, a holistic conceptualization of the variables that form part of tap-hole lifecycle management and performance. Specifically, the article focuses on the variables related to coke-bed-based processes (FeCr, SiMn, and HCFeMn) applying SAF technology of circular design. 相似文献
4.
Andrew Artzer Michael Moats Jack Bender 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(12):2856-2863
Antimony and bismuth recovery from copper electrorefining electrolyte could reduce the impacts of these problem elements and produce a new primary source for them. Two proprietary phosphonic acid ester extractants were examined (REX-1 and REX-2) for the removal of antimony and bismuth from copper electrorefining electrolytes. Experimentation included shakeout and break tests to determine the basic parameters for the extractants in terms of maximum loading, break times, and extraction and stripping efficiency. Five permutations of extractant mixtures (100 wt.% REX-1 and 25 wt.%, 50 wt.%, 75 wt.% and 100 wt.% REX-2) were studied. It was determined that REX-2 was able to extract Sb and Bi from the electrolyte, but required some mixture with REX-1 to better facilitate stripping with 400 g/L sulfuric acid. The laboratory electrorefining electrolyte containing glue had faster disengagement times than a synthetic solution without glue. 相似文献
5.
Thermal barrier coatings (TBCs) are used to protect the hot sections of gas turbine engines and airplane engines. A TBC system comprises a substrate, bond coat, and TBC topcoat. The development of an accurate method for determining the Young’s modulus and Poisson’s ratio of TBC using a multilayered specimen is of importance. In this study, we applied the bending theory of a laminated plate to a three-layered material and proposed models to determine the Young’s modulus and Poisson’s ratio of the TBC layer using the bending strain of the TBC system specimen. Three methods were developed by utilizing (i) the coating biaxial strain, (ii) substrate biaxial strain, or (iii) coating and substrate biaxial strains. Subsequently, we determined appropriate dimensions of the specimen and span by using three-dimensional finite element analysis, and numerically verified the usefulness of the three proposed methods. However, the Young’s modulus and Poisson’s ratio determined using the multilayered specimen with a substrate are sensitive to experimental errors. Therefore, we evaluated the sensitivity of the three proposed methods to experimental error, and we determined the most insensitive method among them. Finally, we experimentally demonstrated the usefulness of this method. 相似文献
6.
Mykola Moroz Fiseha Tesfaye Myroslava Prokhorenko Serhiy Prokhorenko Oleksandr Reshetnyak 《Journal of Phase Equilibria and Diffusion》2018,39(1):11-16
Triangulation of the Ag-Hg-Se-I system in the vicinity of quaternary phase Ag4HgSe2I2 was performed by differential thermal analysis, X-ray diffraction and electromotive force (EMF) methods. The spatial position of the phase region Ag4HgSe2I2-Se-HgI2 regarding the figurative point of silver was used to write the chemical reaction of formation of Ag4HgSe2I2. The EMF measurements were carried out by applying an electrochemical cell: (–) C|Ag|Ag2GeS3 glass|Ag4HgSe2I2, HgI2, Se|C (+), where C is graphite and Ag2GeS3 glass is the fast purely Ag+ ions conducting electrolyte. The linear dependence of the EMF of the electrochemical cell on temperature was used to determine the standard thermodynamic values of Ag4HgSe2I2 for the first time. 相似文献
7.
Ying Zeng Bin Jiang Ouling Shi Gaofen Quan Salih Al-Ezzi FuSheng Pan 《Metals and Materials International》2018,24(4):830-839
Some alloying elements (Al, Er, Gd, Li, Mn, Sn, Y, Zn) were proved recently by calculations or experiments to improve the formability of Mg alloys, but ignoring their site preference in Mg crystals during the calculated process. A crystallographic model was built via first principle calculations to predict the site preferences of these elements. Regularities between doping elements and site preferences were summarized. Meanwhile, in the basis of the crystallographic model, a series of formulas were deduced combining the diffraction law. It predicted that a crystal plane with abnormal XRD peak intensity of the Mg-based solid solutions, compared to that of the pure Mg, prefers to possess solute atoms. Thus, three single-phase solid solution alloys were then prepared through an original In-situ Solution Treatment, and their XRD patterns were compared. Finally, the experiment further described the site preferences of these solute atoms in Mg crystal, verifying the calculation results. 相似文献
8.
Wei Zuo Le Ma Yu Lu Shu-yong Li Zhiqiang Ji Min Ding 《Metals and Materials International》2018,24(6):1346-1358
A novel additive manufacturing method with TIG–MIG hybrid heat source was applied for fabricating 5356 aluminum alloy component. In this paper the microstructure evolution, mechanical properties and fracture morphologies of both as-deposited and heat-treated component were investigated, and how these were affected by different heat-treated temperature. The as-deposited microstructure showed dominant equiaxed grains with second phase, and the size of them is coarse in the bottom region, medium in the middle region and fine in the top region owing to different thermal cycling conditions. Compared with as-deposited microstructure, the size of grain becomes large and second phases gradually dissolve in the matrix as heat-treated temperature increase. Different microstructures determine the mechanical properties of component. Results show that average ultimate tensile strength enhances from 226 to 270 MPa and average microhardness increases from 64.2 to 75.3 HV0.1 but ductility decreases from 33 to 6.5% with heat-treated temperature increasing. For all components, the tensile properties are almost the same in the vertical direction (Z) and horizontal direction (Y) due to equiaxed grains, which exhibits isotropy, and the mechanisms of these are analyzed in detailed. In general, the results demonstrate that hybrid arc heat source has the potential to fabricate aluminum alloy component. 相似文献
9.
Sandeep Kumar 《Wireless Personal Communications》2018,101(2):723-734
Spectrum sensing is the important function of cognitive radio and energy detection is the most popular technique used for spectrum sensing. Detection of the availability of unused spectrum for the secondary user becomes difficult when the channel is affected by composite multipath/shadowed fading. In this paper, the performance analysis of an Energy Detector in Hoyt/gamma composite fading channel with Maximum Ratio Combining employing micro-diversity is analyzed. Analytical expressions for performance parameters, i.e., the average probability of detection and the average area under the receiver operating characteristics curve are evaluate. The effect of diversity on the performance of energy detector is also studied. Monte-Carlo simulation results have verified the accuracy of the proposed analysis. 相似文献
10.
David Dobnik Kristina Gruden Jana Žel Yves Bertheau Arne Holst-Jensen Marko Bohanec 《Food Analytical Methods》2018,11(8):2105-2122
The selection of the best-fit-for-purpose analytical method to be implemented in the laboratory is difficult due to availability of multiple methods, targets, aims of detection, and different kinds and sources of more or less reliable information. Several factors, such as method performance, practicability, cost of setup, and running costs need to be considered together with personnel training when selecting the most appropriate method. The aim of our work was to prepare a flexible multicriteria decision analysis model suitable for evaluation and comparison of analytical methods used for the purpose of detecting and/or quantifying genetically modified organisms, and to use this model to evaluate a variety of changing analytical methods. Our study included selection of PCR-, isothermal-, protein-, microarray-, and next-generation sequencing-based methods in simplex and/or multiplex formats. We show that the overall result of their fitness for purpose is relatively similar; however, individual criteria or a group of related criteria exposed more substantial differences between the methods. The proposed model of this decision support system enables easy modifications and is thus suitable for any other application of complex analytical methods. 相似文献