全文获取类型
收费全文 | 36981篇 |
免费 | 2002篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 276篇 |
综合类 | 16篇 |
化学工业 | 8252篇 |
金属工艺 | 645篇 |
机械仪表 | 720篇 |
建筑科学 | 1172篇 |
矿业工程 | 62篇 |
能源动力 | 916篇 |
轻工业 | 6901篇 |
水利工程 | 383篇 |
石油天然气 | 151篇 |
武器工业 | 1篇 |
无线电 | 1561篇 |
一般工业技术 | 5899篇 |
冶金工业 | 6642篇 |
原子能技术 | 145篇 |
自动化技术 | 5283篇 |
出版年
2024年 | 83篇 |
2023年 | 343篇 |
2022年 | 669篇 |
2021年 | 1121篇 |
2020年 | 846篇 |
2019年 | 923篇 |
2018年 | 1586篇 |
2017年 | 1512篇 |
2016年 | 1582篇 |
2015年 | 1174篇 |
2014年 | 1470篇 |
2013年 | 2864篇 |
2012年 | 2321篇 |
2011年 | 2272篇 |
2010年 | 1784篇 |
2009年 | 1601篇 |
2008年 | 1596篇 |
2007年 | 1465篇 |
2006年 | 1049篇 |
2005年 | 873篇 |
2004年 | 786篇 |
2003年 | 739篇 |
2002年 | 651篇 |
2001年 | 482篇 |
2000年 | 425篇 |
1999年 | 464篇 |
1998年 | 2384篇 |
1997年 | 1504篇 |
1996年 | 956篇 |
1995年 | 540篇 |
1994年 | 419篇 |
1993年 | 429篇 |
1992年 | 136篇 |
1991年 | 131篇 |
1990年 | 111篇 |
1989年 | 103篇 |
1988年 | 122篇 |
1987年 | 109篇 |
1986年 | 101篇 |
1985年 | 111篇 |
1984年 | 93篇 |
1983年 | 68篇 |
1982年 | 75篇 |
1981年 | 104篇 |
1980年 | 94篇 |
1978年 | 50篇 |
1977年 | 142篇 |
1976年 | 262篇 |
1975年 | 44篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
J. R. Díaz-Estrada E. Camps L. Escobar-Alarcón J. A. Ascencio 《Journal of Materials Science》2007,42(4):1360-1368
Deposition of Ti was carried out by laser ablation onto hydroxyapatite porous discs in an Ar atmosphere. Ti nanoparticles
were deposited onto HAp surface in order to modify its roughness and morphology as it is observed by scanning electron microscopy
(SEM) and scanning probe microscopy (SPM). A homogeneous distribution of Ti over the disc surface was corroborated by elemental
mapping. A comparison of the hydroxyapatite hardness before and after deposition was performed using SPM nanoindentation.
Transmission Electron Microscopy (TEM) showed that the Ti nanoparticles obtained were covered by an oxygen shell. It is shown
that surface modifications of the covered HAp by Ti result in better mechanical properties, reducing the possible damage to
the HAp ceramic by friction or impacts as it often happens in meniscus, bone junctions and the inclusion of prosthesis for
human treatments. 相似文献
73.
Peter Eaton Andrea Ragusa Caroline Clavel Cristina T Rojas Paul Graham Raúl V Durán Soledad Penadés 《IEEE transactions on nanobioscience》2007,6(4):309-318
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents. 相似文献
74.
75.
András Ványolos Balázs Dóra Attila Virosztek 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):643-645
We report of a theoretical study on quasi-one dimensional unconventional charge density wave (UCDW) driven by electron–phonon
interaction. Within mean field theory, we find that the wavevector dependence of the coupling leads to a momentum dependent
single particle gap on the Fermi surface. The presence of small energy single particle excitations around the gap nodes significantly
changes the optical conductivity compared to the conventional CDW result. In addition to that, the collective phase excitation
arising from fluctuation of the order parameter leads to further qualitative changes of the conductivity and results in an
effective mass that is nonmonotonic in temperature.
相似文献
76.
V. Ocelík V. Z. Bengus E. B. Korolkova K. Csach J. Miškuf P. Duhaj 《Journal of Materials Science》1991,26(24):6699-6705
The fracture stress and the critical stress intensity factor of the Fe40Ni40B20 amorphous metallic ribbons 20 μm thick were measured in the temperature range 4.2–300 K and at deformation rates from 3.3×10−6 to 1.25×10−3 m−1 with the aim to obtain more information on the condition for the onset and development of the inhomogeneous plastic deformation
and fracture. 相似文献
77.
In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within
the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour;
the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian
(ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several
representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental
data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle
with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks
to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present
spurious oscillations.
Received: 20 March 2002 / Accepted: 15 October 2002
The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged. 相似文献
78.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
79.
80.
Summary The cationic polymerization of 2-ethyl-2-oxazoline using CH3I as initiator at different monomer/initiator ratios, temperatures, solvents and times of polymerization was carried out. The effect of these variables on the polymerization yield and viscosity of the polymers was studied. The poly(N-propionyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine) (PEI). All the polymers were characterized by elemental analysis, IR,1H NMR, and13C NMR spectroscopy. 相似文献