全文获取类型
收费全文 | 11510篇 |
免费 | 1383篇 |
国内免费 | 801篇 |
专业分类
电工技术 | 516篇 |
综合类 | 845篇 |
化学工业 | 2007篇 |
金属工艺 | 304篇 |
机械仪表 | 457篇 |
建筑科学 | 508篇 |
矿业工程 | 555篇 |
能源动力 | 309篇 |
轻工业 | 487篇 |
水利工程 | 98篇 |
石油天然气 | 282篇 |
武器工业 | 780篇 |
无线电 | 2727篇 |
一般工业技术 | 2449篇 |
冶金工业 | 198篇 |
原子能技术 | 509篇 |
自动化技术 | 663篇 |
出版年
2024年 | 37篇 |
2023年 | 139篇 |
2022年 | 317篇 |
2021年 | 323篇 |
2020年 | 311篇 |
2019年 | 270篇 |
2018年 | 233篇 |
2017年 | 412篇 |
2016年 | 418篇 |
2015年 | 400篇 |
2014年 | 668篇 |
2013年 | 771篇 |
2012年 | 786篇 |
2011年 | 890篇 |
2010年 | 704篇 |
2009年 | 736篇 |
2008年 | 577篇 |
2007年 | 710篇 |
2006年 | 675篇 |
2005年 | 618篇 |
2004年 | 493篇 |
2003年 | 480篇 |
2002年 | 381篇 |
2001年 | 343篇 |
2000年 | 282篇 |
1999年 | 261篇 |
1998年 | 204篇 |
1997年 | 181篇 |
1996年 | 159篇 |
1995年 | 160篇 |
1994年 | 132篇 |
1993年 | 109篇 |
1992年 | 83篇 |
1991年 | 82篇 |
1990年 | 56篇 |
1989年 | 59篇 |
1988年 | 34篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 39篇 |
1984年 | 37篇 |
1983年 | 22篇 |
1982年 | 39篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1976年 | 5篇 |
1974年 | 3篇 |
1959年 | 3篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Flow-mode static and dynamic laser light scattering (SLS/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 °C were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, Rg and hydrodynamic radius, Rh) of polymers eluting from the GPC columns were obtained simultaneously. The conformation of different polymers in TCB at 150 °C were discussed according to the scaling relationships between Rg, Rh and M and the ρ-ratio (ρ=Rg/Rh). Flow-mode DLS results of PDMS were verified by batch-mode DLS study of the same sample. The presented technique was proved to be a convenient and quick method to study the shape and conformation of polymers in solution at high temperature. However, the flow-mode DLS was only applicable for high molecular weight polymers with a higher refractive index increment such as PDMS. 相似文献
12.
Nonlinear Propagation of Coupling Optical Pulse under Compton Scattering in Laser Medium 总被引:1,自引:1,他引:0
HAO Dong-shan ZHANG Xiao-fu 《半导体光子学与技术》2006,12(3):178-183,204
After considering Kerr nonlinear effect,group velocity dispersion of host and gain distribution of active particle in laser amplifying medium,a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides,the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium. 相似文献
13.
14.
对爆炸效应在淤泥软基工程中的应用问题进行了探讨,并首次提出了爆炸在淤泥软基中的分界应力特征以及排水固结及破坏分区的基本模式。为采用动力加速对淤泥软基工程的处理,提供了试验依据,具有实用价值和指导意义。 相似文献
15.
16.
Adriana Brancaccio Giovanni Leone Rocco Pierri 《AEUE-International Journal of Electronics and Communications》2004,58(6):382-390
In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data. 相似文献
17.
18.
Didier Lemoine 《Computer Physics Communications》1996,97(3):331-344
A quantum wave packet code for studying nonreactive scattering of closed-shell atoms or diatomic molecules from a rigid surface is described. The time evolution relies on the Chebychev propagator. Up to 5 collider degrees of freedom, 3 in translation and 2 in rotation, are treated in a pseudospectral way with the momentum or finite basis representation as the primary space. Potential matrix elements are efficiently evaluated by means of sequential 1D transformations between momentum and coordinate spaces. Fast Fourier transforms are performed for the translational and azimuthal coordinates whereas a Gauss-Legendre transform is used for the polar coordinate. This pseudospectral strategy minimizes memory requirements because no off-diagonal Hamiltonian matrix elements need to be stored. In addition, a wide variety of physical systems can be studied since no particular functional form is imposed for the interaction potential. 相似文献
19.
20.
Shizuo Arichi Noriyuki Sakamoto Shozo Himuro Mayumi Miki Masafumi Yoshida 《Polymer》1985,26(8):1175-1180
In order to obtain the additional data concerning the unperturbed dimension of poly-4-substituted styrene, light scattering measurements are performed on the twenty-two fractions with molecular weight of (0.91–352)·104 of poly(4-acetoxystyrene) in dioxan at 25°C, from which the molecular weight obtained was found easily to be evaluated with the gel permeation chromatography using THF. Phase separation experiments for this polymer indicate that the theta state is attained in isopropyl acetate at 19.7°C and butyl acetate at 26.8°C. By making viscosity measurements at that state, the value of KΘ is directly evaluated as 5.4·10?4 dl g?1. The limiting viscosity number is also obtained in good solvents, THF and dioxan, at 25°C and constants of the Mark-Houwink-Sakurada equation in each solvent are determined. Further, approximately the same KΘ as above is obtained from these data with the Stockmayer-Fixman plot. The calculated value of steric factor, 2.37, on this polymer may be plausible, compared with those of polyvinylaromatic derivatives. 相似文献