全文获取类型
收费全文 | 1341篇 |
免费 | 51篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 332篇 |
金属工艺 | 56篇 |
机械仪表 | 52篇 |
建筑科学 | 59篇 |
矿业工程 | 1篇 |
能源动力 | 39篇 |
轻工业 | 61篇 |
水利工程 | 8篇 |
石油天然气 | 2篇 |
无线电 | 115篇 |
一般工业技术 | 257篇 |
冶金工业 | 134篇 |
原子能技术 | 5篇 |
自动化技术 | 258篇 |
出版年
2024年 | 4篇 |
2023年 | 21篇 |
2022年 | 24篇 |
2021年 | 51篇 |
2020年 | 42篇 |
2019年 | 51篇 |
2018年 | 33篇 |
2017年 | 23篇 |
2016年 | 42篇 |
2015年 | 42篇 |
2014年 | 44篇 |
2013年 | 74篇 |
2012年 | 79篇 |
2011年 | 97篇 |
2010年 | 70篇 |
2009年 | 59篇 |
2008年 | 58篇 |
2007年 | 67篇 |
2006年 | 57篇 |
2005年 | 43篇 |
2004年 | 36篇 |
2003年 | 21篇 |
2002年 | 32篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 16篇 |
1998年 | 51篇 |
1997年 | 31篇 |
1996年 | 23篇 |
1995年 | 25篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1967年 | 2篇 |
排序方式: 共有1392条查询结果,搜索用时 0 毫秒
991.
Liposome-based nanocapsules 总被引:1,自引:0,他引:1
Ruysschaert T Germain M Gomes JF Fournier D Sukhorukov GB Meier W Winterhalter M 《IEEE transactions on nanobioscience》2004,3(1):49-55
Here we present three different types of mechanically stable nanometer-sized hollow capsules. The common point of the currently developed systems in our laboratory is that they are liposome based. Biomolecules can be used to functionalize lipid vesicles to create a new type of intelligent material. For example, insertion of membrane channels into the capsule wall can modify the permeability. Covalent binding of antibodies allows targeting of the capsule to specific sites. Liposomes loaded with enzymes may provide an optimal environment for them with respect to the maximal turnover and may stabilize the enzyme. However, the main drawback of liposomes is their instability in biological media as well as their sensitivity to many external parameters such as temperature or osmotic pressure. To increase their stability we follow different strategies: 1) polymerize a two-dimensional network in the hydrophobic core of the membrane; 2) coat the liposome with a polyelectrolyte shell; or 3) add surface active polymers to form mixed vesicular structures. 相似文献
992.
Temperature estimation using ultrasonic spatial compound imaging 总被引:3,自引:0,他引:3
Pernot M Tanter M Bercoff J Waters KR Fink M 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2004,51(5):606-615
The feasibility of temperature estimation during high-intensity focused ultrasound therapy using pulse-echo diagnostic ultrasound data has been demonstrated. This method is based upon the measurement of thermally-induced modifications in backscattered RF echoes due to thermal expansion and local changes in the speed of sound. It has been shown that strong ripple artifacts due to the thermo-acoustic lens effect severely corrupt the temperature estimates behind the heated region. We propose here a new imaging technique that improves the temperature estimation behind the heated region and reduces the variance of the temperature estimates in the entire image. We replaced the conventional beamforming on transmit with multiple steered plane wave insonifications using several subapertures. A two-dimensional temperature map is estimated from axial displacement maps between consecutive RF images of identically steered plane wave insonifications. Temperature estimation is then improved by averaging the two-dimensional maps from the multiple steered plane wave insonifications. Experiments were conducted in a tissue-mimicking gelatin-based phantom and in fresh bovine liver. 相似文献
993.
Despite the intrinsic complexity of integrating individual, social and technologically supported intelligence, the paper proposes
a relatively simple ‘connectionist’ framework for conceptualizing distributed cognitive systems. Shared information sources
(documents) are represented as nodes connected by links of variable strength, which increases as the documents co-occur in
the usage patterns. This learning procedure captures and exploits its users’ implicit knowledge to help them find relevant
information, thus supporting an unconscious form of exchange. These principles are applied to a concrete problem domain: architects
sharing design knowledge through a database of associatively connected building projects. 相似文献
994.
Deepak V. Kulkarni Daniel A. Tortorelli Mathias Wallin 《Computer Methods in Applied Mechanics and Engineering》2007,196(7):1169-1177
We introduce a Newton-Schur alternative to the consistent tangent approach in plasticity computations and show that the structure of the consistent tangent approach is preserved in the new Newton-Schur approach. However, the local constitutive iterations used in the conventional computational plasticity analyses are eliminated when using the Newton-Schur approach. Two numerical examples are presented which illustrate the efficiencies gained by the new approach. 相似文献
995.
Grard Fleury 《Probabilistic Engineering Mechanics》2006,21(1):35-43
In many applications of stochastic calculus, like stochastic dynamical systems, stochastic differential equations are involved, the coefficients of which are not globally, but only locally Lipschitz. For instance, in order to study technics using one trajectory of a process defined by differential equations of oscillators associated to structures submitted to a white noise excitation, such as the random decrement, one need to simulate a trajectory for such a process. Different schemes are proposed to numerically solve such stochastic differential equations: Euler, Milshtein or Newmark schemes for example. In this paper, the almost sure convergence of some of the most important schemes is studied under locally Lipschitz assumptions and a speed of convergence is established. 相似文献
996.
997.
Finite element modeling concepts and linear analyses of 3D regular open cell structures 总被引:1,自引:0,他引:1
Mathias?H.?LuxnerEmail author Juergen?Stampfl Heinz?E.?Pettermann 《Journal of Materials Science》2005,40(22):5859-5866
Various Finite Element modeling concepts and linear analyses of 3D regular cellular solids (lattice structures) with relative
densities ranging from 10% to 20% are presented. Continuum element based models and beam element based models are employed,
the latter with and without an adaptation of stiffness in the vicinity of the vertices. Space filling unit cell models are
used for a constitutive characterization of four different structures in terms of density and directional dependence of their
Young's moduli. Finite structure models of different size are simulated for investigating the influence of free surfaces and
being compared to results of uniaxial compression tests of samples fabricated by two different Rapid Prototyping techniques. 相似文献
998.
Zhanar E. Ibraeva Mathias Hahn Werner Jaeger Andre Laschewsky Larisa A. Bimendina Sarkyt E. Kudaibergenov 《大分子材料与工程》2005,290(8):769-777
Summary: The swelling behavior of an amphoteric gel composed of 50 mol‐% of maleic acid (MA), 25 mol‐% of N,N′‐dimethyldiallylammonium chloride (DMDAAC) and 25 mol‐% of diallylamine (DAA) was studied in aqueous and aqueous‐salt solutions. The isoelectric point (IEP) of the MA‐DMDAAC‐DAA gel determined from swelling experiments was about pH 4.6. Considerable gel swelling with increasing ionic strength was observed at the IEP. Dynamic swelling properties of the amphoteric gel in water with and without added salt were measured at various pH values including the IEP. The swelling behavior of the amphoteric gel was found to depend on the ionization state of the functional groups. It can be described by either a relaxation‐controlled or non‐Fickian (anomalous) mechanism. Swelling‐deswelling properties of the amphoteric gel were also studied in mixtures of water and organic solvents. The amphoteric gel was able to complex sodium poly(styrene sulfonate), sodium lauryl sulfate, the cationic drug richlocain, and the bivalent transition metal ions Cu2+, Ni2+, Co2+, and Zn2+. The sorption of polyelectrolyte, surfactant, drug, and metal ions by the amphoteric gel is accompanied by the contraction of the gel network. Partial release of the cationic drug molecules entrapped into the gel volume takes place at the IEP of the amphoteric gel with low activation energy, while neither the anionic polyelectrolyte nor the surfactants are released from the gel interior at the IEP. The swelling‐shrinking behavior of gel‐polyelectrolyte and gel‐surfactant complexes in dependence of pH and ionic strength of the outer solution is similar.
999.
Kals M Natter K Thallinger GG Trajanoski Z Kohlwein SD 《Yeast (Chichester, England)》2005,22(3):213-218
The Yeast Protein Localization database (YPL.db(2)) is an archive of microscopic image data of protein localization patterns in the yeast Saccharomyces cerevisiae. The current version of YPL.db(2) harbours 500 sets of image data derived from high-resolution microscopic analyses of proteins tagged with the green fluorescent protein (GFP). Major functional improvements in YPL.db(2) over a previous release are a web-based experiment and image submission interface, facilitating standardized data entry by remote users through the Internet. The image display page provides image gallery and image scrolling features. In addition, fluorescence and transmission images can be superimposed, allowing image fading for precise correlation of the protein's localization in the cellular context. The reference structure database displaying 'prototypic' localization patterns was extended, and a feature to display and manipulate 3D-image datasets, using a freely available VRML plug-in, was included. Access to the Yeast Protein Localization database version 2.0 (YPL.db(2)) is available through http://YPL.uni-graz.at. 相似文献
1000.
Shear modulus imaging with 2-D transient elastography 总被引:3,自引:0,他引:3
Sandrin L Tanter M Catheline S Fink M 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2002,49(4):426-435
In previous work, we have shown that time-resolved 2-D transient elastography is a promising technique for characterizing the elasticity of soft tissues. It involves the measurement of the displacements induced by the propagation of low frequency (LF) pulsed shear waves in biological tissues. In this paper, we present a novel apparatus that contains a LF vibrating device surrounding a linear array of 128 ultrasonic transducers that performs ultrafast ultrasonic imaging (up to 10,000 frames/s) and that is able to follow in real time the propagation of a LF shear wave in the human body. The vibrating device is made of two rods, fixed to electromagnetic vibrators, that produce in the ultrasonic image area a large amplitude shear wave. The geometry has been chosen both to enhance the sensitivity and to create a quasi linear shear wave front in the imaging plane. An inversion algorithm is used to recover the shear modulus map from the spatio-temporal data, and the first experimental results obtained from tissue-equivalent materials are presented. 相似文献