全文获取类型
收费全文 | 50274篇 |
免费 | 4866篇 |
国内免费 | 3102篇 |
专业分类
电工技术 | 6055篇 |
技术理论 | 1篇 |
综合类 | 2797篇 |
化学工业 | 10306篇 |
金属工艺 | 4147篇 |
机械仪表 | 3375篇 |
建筑科学 | 850篇 |
矿业工程 | 2042篇 |
能源动力 | 1691篇 |
轻工业 | 3696篇 |
水利工程 | 228篇 |
石油天然气 | 1232篇 |
武器工业 | 373篇 |
无线电 | 4784篇 |
一般工业技术 | 9015篇 |
冶金工业 | 1986篇 |
原子能技术 | 3491篇 |
自动化技术 | 2173篇 |
出版年
2024年 | 220篇 |
2023年 | 946篇 |
2022年 | 1505篇 |
2021年 | 1878篇 |
2020年 | 1712篇 |
2019年 | 1617篇 |
2018年 | 1589篇 |
2017年 | 1973篇 |
2016年 | 2191篇 |
2015年 | 2069篇 |
2014年 | 2957篇 |
2013年 | 3663篇 |
2012年 | 3428篇 |
2011年 | 4058篇 |
2010年 | 2735篇 |
2009年 | 2892篇 |
2008年 | 2628篇 |
2007年 | 2895篇 |
2006年 | 2611篇 |
2005年 | 2170篇 |
2004年 | 1901篇 |
2003年 | 1749篇 |
2002年 | 1373篇 |
2001年 | 1099篇 |
2000年 | 1033篇 |
1999年 | 831篇 |
1998年 | 712篇 |
1997年 | 615篇 |
1996年 | 547篇 |
1995年 | 422篇 |
1994年 | 418篇 |
1993年 | 323篇 |
1992年 | 275篇 |
1991年 | 224篇 |
1990年 | 168篇 |
1989年 | 159篇 |
1988年 | 118篇 |
1987年 | 82篇 |
1986年 | 60篇 |
1985年 | 75篇 |
1984年 | 79篇 |
1983年 | 49篇 |
1982年 | 76篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1976年 | 9篇 |
1974年 | 7篇 |
1959年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
G. Martinez 《Journal of Low Temperature Physics》2003,133(1-2):61-95
High magnetic fields are one of the most powerful tools available to scientists for the study, modification and control of matter. This includes the knowledge on correlations effects, interaction mechanisms, structural information and understanding of mesoscopic effects. In this context, a review of recent scientific achievements at the Grenoble High Magnetic Laboratory is given to illustrate, on specific examples, the power of the Magnetic Field probe. 相似文献
22.
Electronic structure and ferromagnetism in III–V compound-based diluted magnetic semiconductors (DMS) are investigated based on first-principles calculations by using the Korringa-Kohn-Rostoker method combined with the coherent-potential-approximation. The stability of the ferromagnetic phase in GaN-, GaAs-, GaP-, GaSb-based DMS is investigated systematically. The calculations show that 3d-impurities from the first-half of the transition metal series favor the ferromagnetic state, while impurities from the latter-half of the series exhibit spin-glass behavior. This chemical trend in the magnetism is explained by the double exchange mechanism taking the local symmetry at the impurity gap states into account. Curie temperatures of GaAs- and GaN-based DMS are estimated by using the Heisenberg model in a mean field approximation with the parameters calculated from first-principles. It is suggested that room-temperature ferromagnetism can be realized in these systems. 相似文献
23.
A.V. GomonnaiI.M. Voynarovych A.M. SolomonYu.M. Azhniuk A.A. KikineshiV.P. Pinzenik M. Kis-VargaL. Daroczy V.V. Lopushansky 《Materials Research Bulletin》2003,38(13):1767-1772
Lattice structure and rod-like shaped SbSI nanocrystals obtained by ball milling with rod thickness down to 70 nm, as estimated from X-ray diffraction (XRD) and electron microscopy, is similar to that of the bulk crystals. The dependence of the grain size on the milling duration is discussed in view of the chain-like crystalline structure of SbSI. Possible factors, responsible for the observed Raman line broadening, are discussed, scattering by surface phonons being considered the predominant one. 相似文献
24.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献
25.
Cs-K混合蒸气中Cs(8D)+K(4S)碰撞能量转移 总被引:3,自引:3,他引:0
在Cs-K混合蒸气中,两步激发Cs原子到8D态,观察了Cs(8D) K(4S)→Cs(5D) K(4P)碰撞能量合并逆过程(REP,reverse energy pooling)。应用双调制技术探测K(4P)原子发射的荧光,基态K原子密度用光学吸收方法测量。得到了REP速率系数,讨论了其它过程对速率系数的影响. 相似文献
26.
In order to investigate the reduction mechanism of thioglycolic acid (TG) on the keratin fibers, cross-sectional samples of white human hair treated with TG were prepared. The heterogeneous reaction between TG and keratin fibers involving the diffusion of TG into human hair was analyzed at the molecular level using microspectrophotometry and FT-Raman spectroscopy. The diffusion of TG into human hair clearly increased by increasing the treatment time and by raising pH. The TG relative concentration and the disconnected relative concentration of disulfide (–SS–) groups at various depths of the hair samples with pH 9.0 were in good agreement, indicating that the reaction rate (the disconnection of –SS– groups) was faster than the diffusion rate of TG into human hair. From these experiments, we demonstrated that TG diffuses gradually beyond the cuticle region, and toward the inside of the cortex region along with the disconnection of –SS– groups. 相似文献
27.
Fe3O4/PSt/TiO2多层包覆电磁响应微球的制备 总被引:7,自引:0,他引:7
首先采用分散聚合法将自制的Fe3O4磁流体和苯乙烯反应合成有磁核的Fe3O4/PSt磁性聚合物微球,然后,用非均匀成核水解反应在Fe3O4/PSt微球外包覆无定形二氧化钛,获得Fe3O4/PSt/TiO2复合微粒。用红外光谱、扫描电镜和热分析对粒子的形貌和结构进行了表征。并测试了微粒的介电性能和磁性,结果表明,所制得复合微粒有良好的电、磁响应性。 相似文献
28.
We report on picosecond time resolved spectroscopy of photogenerated infrared active vibrations in thin films of 2,5-dioctyloxy poly(phenylene vinylene). We excited the films by ?4 ps long pulses of 565 nm laser light with 2×1013 photons/cm2 per pulse and repetition rate of 76 MHz. We then followed the temporal evolution of the infrared active vibrational (IRAV) spectrum using a subsequent, variably delayed, weak tunable IR probe pulses of similar temporal duration. Under these conditions, we show clear spectroscopic evidence for photogenerated infrared active vibrations at times which are shorter than our temporal resolution (<4 ps). We suggest that the transient IRAV absorption is due to secondary polarons formation following exciton dissociation. 相似文献
29.
介绍用已知年龄和烧结温度的古陶片穆斯堡尔超精细参数与年龄和烧结温度的实验关系曲线作基础,应用计算机模拟程序,自动求出未知陶片的年龄和最高烧结温度的方法。 相似文献
30.
回热损失对磁斯特林制冷循环制冷率的影响 总被引:7,自引:0,他引:7
从铁磁质的磁化强度一般表示式出发,探讨热阻和回热损失对磁斯特林制冷循环性能的影响,导出最大制冷率及其它性能参数。得到了结果适用于以顺磁质为工质的磁斯特林制冷循环。并指出在理想回热条件下的结论也适用于磁卡诺制冷循环。 相似文献