全文获取类型
收费全文 | 655281篇 |
免费 | 9406篇 |
国内免费 | 2016篇 |
专业分类
电工技术 | 12368篇 |
综合类 | 1076篇 |
化学工业 | 99062篇 |
金属工艺 | 22460篇 |
机械仪表 | 18495篇 |
建筑科学 | 17842篇 |
矿业工程 | 1675篇 |
能源动力 | 17693篇 |
轻工业 | 66202篇 |
水利工程 | 5296篇 |
石油天然气 | 5285篇 |
武器工业 | 29篇 |
无线电 | 82517篇 |
一般工业技术 | 121162篇 |
冶金工业 | 124728篇 |
原子能技术 | 9537篇 |
自动化技术 | 61276篇 |
出版年
2021年 | 4938篇 |
2020年 | 3584篇 |
2019年 | 4431篇 |
2018年 | 7357篇 |
2017年 | 7171篇 |
2016年 | 7585篇 |
2015年 | 5963篇 |
2014年 | 9637篇 |
2013年 | 31156篇 |
2012年 | 16394篇 |
2011年 | 22914篇 |
2010年 | 17840篇 |
2009年 | 20162篇 |
2008年 | 21550篇 |
2007年 | 21606篇 |
2006年 | 19221篇 |
2005年 | 17732篇 |
2004年 | 17134篇 |
2003年 | 16680篇 |
2002年 | 16149篇 |
2001年 | 16233篇 |
2000年 | 15286篇 |
1999年 | 16277篇 |
1998年 | 38564篇 |
1997年 | 27836篇 |
1996年 | 21875篇 |
1995年 | 16916篇 |
1994年 | 15200篇 |
1993年 | 14587篇 |
1992年 | 10809篇 |
1991年 | 10381篇 |
1990年 | 9919篇 |
1989年 | 9571篇 |
1988年 | 9210篇 |
1987年 | 7765篇 |
1986年 | 7835篇 |
1985年 | 9390篇 |
1984年 | 8658篇 |
1983年 | 7814篇 |
1982年 | 7199篇 |
1981年 | 7293篇 |
1980年 | 6859篇 |
1979年 | 6591篇 |
1978年 | 6151篇 |
1977年 | 7547篇 |
1976年 | 10187篇 |
1975年 | 5268篇 |
1974年 | 5048篇 |
1973年 | 4994篇 |
1972年 | 3992篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Shute H.A. Wilton D.T. McKirdy D.Mc.A. Mapps D.J. 《IEEE transactions on magnetics》2004,40(5):3402-3406
We have used a series of singular expansion functions to represent the potential across the gap of a shielded pole head in the presence of a highly permeable underlayer. This method of analysis reduces the size of the system of equations to be solved for the series coefficients to the number of coefficients that will be used. Just two series terms suffice to evaluate the magnetic potential to within 1% of the pole potential at any point on the air-bearing surface for a large range of head dimensions. Here, we express the surface field spectrum analytically. Including just two series terms provides an excellent estimate. 相似文献
902.
A physically based hysteresis theory incorporating a domain size that depends on the Weiss effective field explains the observed ranges of reversible and irreversible magnetization in the initial-magnetization curve and exterior loop of ferromagnetic materials. The theory applies to materials exhibiting both normal and wasp-waisted exterior loops and agrees well with measured data. It also provides close linkages between magnetization at the quantum scale, domain properties at the mesoscopic scale, and measurements at the macroscopic scale. 相似文献
903.
E. N. Selivanov V. M. Chumarev R. I. Gulyaeva V. P. Mar'evich A. D. Vershinin A. A. Pankratov E. S. Korepanova 《Inorganic Materials》2004,40(8):845-850
The iron calcium oxysulfides Ca3Fe4S3O6 and CaFeSO are synthesized by reacting mixtures of CaO and FeS in an inert atmosphere. Their elemental compositions and lattice parameters are determined by x-ray microanalysis and x-ray diffraction. From the temperature-dependent lattice parameters of the oxysulfides (measured up to 1020 K), their thermal expansion coefficients are evaluated. 相似文献
904.
The dielectric and pyroelectric properties of Ge-doped (0.1 mol %) TlInS2 crystals are studied. The results demonstrate that TlInS2 is a ferroelectric relaxor. The experimental data are used to evaluate, using the Vogel–Fulcher relation, the activation energy (0.045 eV), preexponential factor (f
0 = 2 × 1013 Hz), and the dipole-freezing temperature (T
F = 142 K) and to determine the temperature range of the stable relaxor (nanodomain) state and the temperature of the transition to the ferroelectric (macrodomain) state, accompanied by an anomaly in the temperature-dependent pyroelectric coefficient. 相似文献
905.
Youngjean Jung Panayiotis Papadopoulos R. O. Ritchie 《International journal for numerical methods in engineering》2004,60(2):429-460
This work concerns the micromechanical constitutive modelling, algorithmic implementation and numerical simulation of polycrystalline superelastic alloys under multiaxial loading. The model is formulated in finite deformations and incorporates the effect of texture. The numerical implementation is based on the constrained minimization of the Helmholtz free energy with dissipation. Simulations are conducted for thin tubes of Nitinol under tension–torsion, as well as for a simplified model of a biomedical stent. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
906.
Jürgen Schönbeçk 《NTM》2004,12(2):80-99
Thomas Fincke (January 6th, 1561–April 24th, 1656), born in Flensburg (Germany), was one of the very most important and significant scientists in Denmark during the
seventeenth century, a mathematician and astrologer and physician in the beginning of modern science, a representative of
humanism and an influentual academic organizer. He studied in Strasbourg (since 1577) and Padua (since 1583) and received
his M.D. in Basel (1587), he practised as a physician throughout his life (since 1587 or 1590) and became a professor at Copenhagen
(1591). But he was best known because of his Geometriae rotundi libri XIIII (1583), a famous book on plane and spherical trigonometry, based not on Euclid but on Petrus Ramus. In this influentual work,
in which Fincke introduced the terms tangent and secant and probable first noticed the Law of Tangents and the so-called Newton-Oppel-Mauduit-Simpson-Mollweide-Gauss-formula,
he showed himself to be „abreast of the mathematics of his time“.
相似文献
907.
Local Strain Measurement within Tendon 总被引:2,自引:0,他引:2
Abstract: Tendon is a dense connective tissue, responsible for transmitting the forces generated by muscles to the skeleton. It is composed of a hierarchical arrangement of crimped collagen fibres, interspersed with proteoglycan matrix and cells, known as tenocytes. During physiological loading, tendons are subjected to strains in the region of 5–6%, which result in the straightening and realignment of the collagen fibres, generating variable local strain fields within the tendon. This study demonstrates a technique for analysing local strains within viable tendon explants, during both loading and unloading of the tissue. Samples were strained in a custom-designed rig, allowing real-time visualisation of cell nuclei, used as local discrete markers, on a confocal microscope. Results indicated that local strains within the fascicle are smaller than the applied strains, never exceeding 1.2%, even at 8% gross applied strain. By contrast, the sliding of adjacent collagen units was recorded at each strain increment in this study, reaching a mean maximum of 3.9% of the applied displacement. Loading–unloading studies indicated that sliding behaviour is reversible up to strains of 5%, and provides the major extension mechanism within the rat-tail tendon. This technique can be extended to further analyse shearing behaviour within the matrix. 相似文献
908.
909.
We determine the temperature fields and stresses formed in a long hollow conducting cylinder under the action of pulsed electromagnetic fields specified by the values of the axial component of the vector of intensity of a uniform magnetic field on the inner and outer surfaces. We consider the case where the electromagnetic action obeys the law of damped sinusoid on the inner and outer surfaces of the cylinder. 相似文献
910.
Terahertz characterisation of building materials 总被引:1,自引:0,他引:1
Piesiewicz R. Kleine-Ostmann T. Krumbholz N. Mittleman D. Koch M. Kurner T. 《Electronics letters》2005,41(18):1002-1004
To obtain realistic models for propagation channels in future pico-cellular indoor terahertz communication systems it is necessary to know the reflective properties of building materials found in a typical office environment. The angular dependent reflection coefficients of different building materials were determined using terahertz time-domain spectroscopy in transmission geometry and Fresnel's equations. This approach is more efficient than a set of measurements in reflection geometry for different angles. Verification of the method with a set of such reflection measurements shows an excellent agreement. 相似文献