全文获取类型
收费全文 | 79196篇 |
免费 | 850篇 |
国内免费 | 702篇 |
专业分类
电工技术 | 1629篇 |
综合类 | 51篇 |
化学工业 | 11968篇 |
金属工艺 | 3559篇 |
机械仪表 | 2770篇 |
建筑科学 | 1686篇 |
矿业工程 | 503篇 |
能源动力 | 1987篇 |
轻工业 | 6612篇 |
水利工程 | 865篇 |
石油天然气 | 2307篇 |
武器工业 | 41篇 |
无线电 | 7722篇 |
一般工业技术 | 17088篇 |
冶金工业 | 13672篇 |
原子能技术 | 2783篇 |
自动化技术 | 5505篇 |
出版年
2022年 | 616篇 |
2021年 | 975篇 |
2020年 | 730篇 |
2019年 | 813篇 |
2018年 | 1592篇 |
2017年 | 1613篇 |
2016年 | 1821篇 |
2015年 | 993篇 |
2014年 | 1639篇 |
2013年 | 3762篇 |
2012年 | 2482篇 |
2011年 | 2991篇 |
2010年 | 2482篇 |
2009年 | 2786篇 |
2008年 | 2790篇 |
2007年 | 2686篇 |
2006年 | 2322篇 |
2005年 | 2033篇 |
2004年 | 1946篇 |
2003年 | 1903篇 |
2002年 | 1808篇 |
2001年 | 1770篇 |
2000年 | 1761篇 |
1999年 | 1692篇 |
1998年 | 4176篇 |
1997年 | 2891篇 |
1996年 | 2147篇 |
1995年 | 1655篇 |
1994年 | 1446篇 |
1993年 | 1469篇 |
1992年 | 1035篇 |
1991年 | 1098篇 |
1990年 | 1109篇 |
1989年 | 1091篇 |
1988年 | 981篇 |
1987年 | 913篇 |
1986年 | 930篇 |
1985年 | 966篇 |
1984年 | 821篇 |
1983年 | 803篇 |
1982年 | 720篇 |
1981年 | 730篇 |
1980年 | 696篇 |
1979年 | 661篇 |
1978年 | 653篇 |
1977年 | 805篇 |
1976年 | 991篇 |
1975年 | 590篇 |
1974年 | 559篇 |
1973年 | 551篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
P.O. Fanger B.M. Ipsen G. Langkilde B.W. Olessen N.K. Christensen S. Tanabe 《Energy and Buildings》1985,8(3):225-236
Groups of 32 and 16 subjects of both sexes were exposed in an environmental chamber to radiant asymmetry caused by a cool wall, a warm wall, and a cool ceiling. Each subject was tested individually while seated and clothed at 0.6 clo. During each 3.5-hour experiment the subject was exposed to six radiant temperature asymmetries. He was asked whether and where he experienced any local cool or warm sensation, and whether it was felt to be uncomfortable. During the entire experiment he was kept thermally neutral by changing the air temperature according to his wishes.For cool walls, warm walls, and cool ceilings curves have been established showing the percentage of dissatisfied subjects as a function of the radiant asymmetry. Radiant asymmetry at a warm wall caused less discomfort than a cool wall. A cool ceiling caused less discomfort than a warm ceiling. Accepting that 5% of the subjects may feel uncomfortable. a radiant temperature asymmetry of 10°C is allowable at a cool wall, 23°C at a warm wall, and 14°C under a cool ceiling. A previous study showed that 4°C is allowable under a warm ceiling. Radiant asymmetry had no significant impact on the operative temperatures preferred by the subjects. No significant differences were observed between the responses of men and women exposed to radiant asymmetry. 相似文献
102.
103.
Kitakami O. Ogawa Y. Fujiwara H. Kugiya F. Suzuki M. 《IEEE transactions on magnetics》1989,25(3):2607-2611
A Co-Cr film deposited directly on a substrate has an initial growth layer with low coercivity. However, the existence of a Ti underlayer prevents the formation of such a layer. As a result, Co-Cr film deposited on a Ti underlayer has high perpendicular anisotropy and coercivity even in cases of extremely thin film thickness (200 Å). As for the read-write characteristics of Co-Cr thin-film media, the existence of such an initial growth layer greatly improves the reproduced output level. The cause for this is considered to be that the free charges which appear on the back surface of the perpendicular recording layer are reduced and the demagnetization field acting on the recorded magnetization subsequently decreases due to the existence of the initial growth layer 相似文献
104.
O. N. Vasilenko 《Strength of Materials》1989,21(10):1415-1420
The Malkin method, which was developed to construct a single unique resonance solution of nonlinear equations, is generalized for the case of the derivation of all stationary solutions in the near-resonance zone, and also for transient oscillations.Kiev Polytechnic Institute. Translated from Problemy Prochnosti, No. 10, pp. 108–112, October, 1989. 相似文献
105.
A numerical solution of the inverse problem of the gravitational field at a single point is obtained using six field elements
for a point, a spherical cap, a differential spherical sector and a vertical segment. In the system of six equations obtained,
the unknowns are the mass of the body, the depth of its center, and the second, third, and fourth degree moments. The accuracy
of the solution of this system is ten times higher than when using three field elements.
__________
Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2007. 相似文献
106.
C. R. Foschini O. Treu Filho S. A. Juiz A. G. Souza J. B. L. Oliveira E. Longo E. R. Leite C. A. Paskocimas J. A. Varela 《Journal of Materials Science》2004,39(6):1935-1941
Reactive zirconia powder was synthesized by the complexation of zirconium metal from zirconium hydroxide using a solution of 8-hydroxiquinoline. The kinetics of zirconia crystallization was followed by X-ray diffraction, scanning electron microscopy and surface area measured by the nitrogen adsorption/desorption technique. The results indicated that zirconia with a surface area as high as 100 m2/g can be obtained by this method after calcination at 500°C. Zirconia presents three polymorphic phases (monoclinic, tetragonal and cubic), which are reversibly interconversible. The cluster model Zr4O8 and Zr4O7
+2 was used for a theoretical study of the stabilization process. The ab initio RHF method was employed with the Gaussian94 program and the total energies and the energy gap of the different phases were calculated and compared with the experimental energy gap. The theoretical results show good reproducibility of the energy gap for zirconia. 相似文献
107.
108.
109.
A. D. Bulanov A. N. Moiseev O. Yu. Troshin V. V. Balabanov D. V. Isaev 《Inorganic Materials》2004,40(6):555-557
High-purity isotopically enriched (99.98% 28Si, 99.57% 29Si, and 99.83% 30Si) silane samples are prepared for the first time. The total hydrocarbon content of the samples is no higher than 0.1–0.3 ppm. The concentration of electroactive impurities in the silicon prepared from the purified monoisotopic silane is below 1015 cm–3. 相似文献
110.
Small-angle neutron scattering measurements on a double-crystal spectrometer with perfect monochromator and analyzer crystals were used to follow microstructural changes in the aluminum alloy VD-17, refractory alloy ZhS-6, and dispersion-hardened zirconia-based ceramics with yttria additions. The measurements were carried out by the Warren method, involving determination of the small-angle neutron attenuation coefficient. The experimentally determined total macroscopic small-angle scattering cross section is correlated with different parameters characterizing external influences on the material: the number of loading cycles, heat-treatment temperature, and fracture stress. The potential of the proposed approach for optimizing processing technologies is discussed. 相似文献