全文获取类型
收费全文 | 1202篇 |
免费 | 82篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 47篇 |
综合类 | 12篇 |
化学工业 | 271篇 |
金属工艺 | 30篇 |
机械仪表 | 55篇 |
建筑科学 | 36篇 |
矿业工程 | 14篇 |
能源动力 | 62篇 |
轻工业 | 305篇 |
水利工程 | 9篇 |
石油天然气 | 11篇 |
武器工业 | 3篇 |
无线电 | 59篇 |
一般工业技术 | 179篇 |
冶金工业 | 53篇 |
原子能技术 | 15篇 |
自动化技术 | 142篇 |
出版年
2024年 | 4篇 |
2023年 | 26篇 |
2022年 | 106篇 |
2021年 | 135篇 |
2020年 | 70篇 |
2019年 | 64篇 |
2018年 | 35篇 |
2017年 | 36篇 |
2016年 | 36篇 |
2015年 | 32篇 |
2014年 | 41篇 |
2013年 | 214篇 |
2012年 | 53篇 |
2011年 | 70篇 |
2010年 | 64篇 |
2009年 | 53篇 |
2008年 | 31篇 |
2007年 | 38篇 |
2006年 | 32篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1932年 | 1篇 |
1927年 | 1篇 |
1919年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有1303条查询结果,搜索用时 250 毫秒
101.
The polycyclic aromatic hydrocarbon (PAH), chrysene, was linked to the solid support TentaGel S-NH2 via a linker by means of synthesis. The resulting product 4-(chrysene-1-yloxy)-N-(TentaGel S)butanamide (4) was then evaluated for its ability to isolate PAHs from solution by means of π-π-interactions. 相似文献
102.
103.
Abstract A four-channel multipotentiostat has been developed for simultaneous voltammetric measurements with microelectrode arrays. To reduce the complexity of electrochemical cell, only one reference and one auxiliary electrode are used. The potential ranges of the four working electrodes may be independently controlled, but they are synchronously scanned by only one DAC. This is accomplished through a microcomputer interfaced with a PCL-711B data acquisition board, which allows the continuous monitoring of the currents and actual potentials of the working electrodes. The system has been applied to the simultaneous determination of ascorbic and uric acids in synthetic samples. The measurements were carried out with gold microelectrodes modified by deposition of noble metals, which enhance the electrocatalysis and provide an anticipation and a better definition of the oxidation potentials. Recuperation of 98.2% and 97.8% for ascorbic and uric acids, respectively, was obtained by using amperometry. 相似文献
104.
H. J. Grabke P. C. Prasannan E. M. MÜller 《Metallurgical and Materials Transactions A》1986,17(6):915-921
The stability of the protective oxide layer formed on Fe-12.5 pct Cr, Fe-18 pct Cr-10 pct Ni, and Fe-25 pct Cr-20 pct Ni was
investigated in a flowing nonequilibrium H2-H2O-CH4-CO mixture at 950 °C. The samples were preoxidized in H2-H2O, and subsequently
the carbon activity was raised in stepwise manner by adding methane. CO formation occurred on the sample surface by the catalytic
reaction CH4 + H2O → CO + 3H2. The conversion of oxide to carbide commenced at the end of the sample wherePco has its highest andPH2O its lowest value. Oxidation, conversion, and catalytic reaction were monitored by gravimetric measurements and CO-determination
during the experiments. Partial equilibria can be calculated for (ac)1 =K
1
P
ch
4/(Ph2)2, (ac)2 =K2(PcoPh2)ph{2o}and(Po2)1\2 = K3Ph2o/Ph2. The conversion of oxide to carbide started when the steady state ofac and(Po2)1/2 on the surface approached the value for the equilibrium of chromium oxide and chromium carbide. The results show that this
steady state value is much nearer to the point(ac)2-(Po2)1/2 in the thermochemical stability diagram than to the point (ac)1 — (Po
2)1/2- The oxide layers were stable even at very high values of (ac)1 which demonstrates that there is only very little interaction of CH4 with the oxide surface.
P. C. Prasannan formerly Research Scientist at the Max-Planck-Institut für Eisenforschung
This paper is based on a presentation made at the “Stephen R. Shatynski Memorial Symposium on Surfaces and Interfaces” held
at the 114th annual AIME meeting in New York, February 24-28, 1985, under the auspices of the ASM-MSD Thermodynamic Activity
Committee. 相似文献
105.
Green State Joining of Silicon Carbide Using Polycarbosilane 总被引:1,自引:0,他引:1
Green state joining of SiC was investigated using a paste consisting of polycarbosilane polymer and SiC powder. The joining process and densification were described. Initial experiments resulted in the formation of symmetrical black bands and cracks on both sides of the joint. However, with modifications in processing conditions, the cracks were eliminated and the resulting joints were indistinguishable from the matrix. The flexural strength of joined samples was measured to be 234 MPa, which was comparable to that of the control sample with similar density. As the applied pressure during joining was increased from 34 to 138 MPa, the strength of the joined samples increased from 180 to 250 MPa. 相似文献
106.
M. Weyers N. Pütz H. Heinecke M. Heyen H. LÜth P. Balk 《Journal of Electronic Materials》1986,15(2):57-59
We report on the intentional ρ-type doping of GaAs layers grown in an UHV system from molecular beams of arsine (AsH3) and mixtures of frimethyl gallium (TMG) and friethyl gallium (TEG). The entire doping range between 1014 cm-3 (growth from pure TEG) and 1020 cm-3 (growth from pure TMG) can be covered by using mixtures of TMG and TEG. As revealed by SIMS and photoluminescence (PL) carbon
is the dominant acceptor in the layers. Comparison of the Hall mobility and of the PL spectra shows that the quality of our
films equals that of the best LPE and MBE grown ρ-type GaAs layers. 相似文献
107.
108.
In this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl3 as an initiator. Average particle sizes (d50) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
109.
Summary The existence of a unique axisymmetric non-radiating surface wave near a cylindrical elastic shell submerged in a fluid and described by Kennard's model is proved. 相似文献
110.
V. WIESMANN D. FRANZ C. HELD C. MÜNZENMAYER R. PALMISANO T. WITTENBERG 《Journal of microscopy》2015,257(1):39-53
An increasing number of free software tools have been made available for the evaluation of fluorescence cell micrographs. The main users are biologists and related life scientists with no or little knowledge of image processing. In this review, we give an overview of available tools and guidelines about which tools the users should use to segment fluorescence micrographs. We selected 15 free tools and divided them into stand‐alone, Matlab‐based, ImageJ‐based, free demo versions of commercial tools and data sharing tools. The review consists of two parts: First, we developed a criteria catalogue and rated the tools regarding structural requirements, functionality (flexibility, segmentation and image processing filters) and usability (documentation, data management, usability and visualization). Second, we performed an image processing case study with four representative fluorescence micrograph segmentation tasks with figure‐ground and cell separation. The tools display a wide range of functionality and usability. In the image processing case study, we were able to perform figure‐ground separation in all micrographs using mainly thresholding. Cell separation was not possible with most of the tools, because cell separation methods are provided only by a subset of the tools and are difficult to parametrize and to use. Most important is that the usability matches the functionality of a tool. To be usable, specialized tools with less functionality need to fulfill less usability criteria, whereas multipurpose tools need a well‐structured menu and intuitive graphical user interface. 相似文献