全文获取类型
收费全文 | 402478篇 |
免费 | 4179篇 |
国内免费 | 994篇 |
专业分类
电工技术 | 7257篇 |
综合类 | 445篇 |
化学工业 | 59799篇 |
金属工艺 | 18391篇 |
机械仪表 | 13041篇 |
建筑科学 | 8712篇 |
矿业工程 | 2783篇 |
能源动力 | 8709篇 |
轻工业 | 30189篇 |
水利工程 | 5000篇 |
石油天然气 | 11363篇 |
武器工业 | 78篇 |
无线电 | 46091篇 |
一般工业技术 | 82560篇 |
冶金工业 | 70344篇 |
原子能技术 | 11102篇 |
自动化技术 | 31787篇 |
出版年
2021年 | 3246篇 |
2019年 | 3227篇 |
2018年 | 5804篇 |
2017年 | 5972篇 |
2016年 | 6348篇 |
2015年 | 3684篇 |
2014年 | 6419篇 |
2013年 | 16596篇 |
2012年 | 10093篇 |
2011年 | 13374篇 |
2010年 | 10650篇 |
2009年 | 11918篇 |
2008年 | 12706篇 |
2007年 | 12681篇 |
2006年 | 11226篇 |
2005年 | 10300篇 |
2004年 | 9890篇 |
2003年 | 9686篇 |
2002年 | 9283篇 |
2001年 | 9343篇 |
2000年 | 8989篇 |
1999年 | 8971篇 |
1998年 | 20325篇 |
1997年 | 14713篇 |
1996年 | 11419篇 |
1995年 | 8943篇 |
1994年 | 7957篇 |
1993年 | 7951篇 |
1992年 | 6481篇 |
1991年 | 6189篇 |
1990年 | 6135篇 |
1989年 | 5797篇 |
1988年 | 5622篇 |
1987年 | 5089篇 |
1986年 | 5023篇 |
1985年 | 5582篇 |
1984年 | 5274篇 |
1983年 | 4896篇 |
1982年 | 4556篇 |
1981年 | 4831篇 |
1980年 | 4540篇 |
1979年 | 4636篇 |
1978年 | 4600篇 |
1977年 | 5056篇 |
1976年 | 6266篇 |
1975年 | 4253篇 |
1974年 | 4284篇 |
1973年 | 4337篇 |
1972年 | 3716篇 |
1971年 | 3361篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition. 相似文献
992.
I A Bukaeva L A Iakovleva B A Lapin L V Indzhiia E M Kobe 《Eksperimental?nai?a onkologii?a》1987,9(4):26-30
The results of morphological study of B- and T-cellular immunoblast baboon lymphomas are presented. Differences are found both in the structure of tumour cells and in the histostructure of tumours as a whole. The tumor cells of B-immunoblastic lymphomas expressed mainly IgM. The tumour cells of certain T-immunoblastic lymphomas being investigated by means of monoclonal OKT4 antibodies had a surface phenotype peculiar to T-helper cells. 相似文献
993.
I A Lisniak 《Eksperimental?nai?a onkologii?a》1987,9(4):72-73
A fraction with the angiogenetic activity was obtained by the methods of the gel-chromatography on G-100 and the ion-exchange chromatography on DEAE-cellulose. Treatment of this fraction with the 10% water isopropanol solution has led to dissociation of the obtained material with a release of a low-molecular-weight angiogenic factor with a high angiogenic activity when tested on the chorioallantoic membrane. The molecular weight of this factor (300-600 daltons) was estimated by the chromatography on the biogel P2. 相似文献
994.
Scattering from bandlimited fractal fibers 总被引:2,自引:0,他引:2
The scattering of electromagnetic or optical waves from tenuous dielectric fibers characterized by bandlimited fractal surfaces is considered. The role of several fractal dimensions is noted, and one suitable for this problem is identified. It is found that in the fractal regime, the Rayleigh-Gans differential scattering cross section as a function of the normalized size parameter exhibits a power-law relation reminiscent of that associated with light scattering from fractal clusters and small-angle X-ray and neutron scattering by porous material. This power-law relation is monotonically related to an appropriate fractal dimension and variance of the fiber surface 相似文献
995.
996.
V. I. Naryshkin G. M. Strelkov A. M. Ryazantsev 《Journal of Communications Technology and Electronics》2008,53(7):782-787
Deformation and attenuation of an ultrawideband radio pulse propagating along a single-wire line are analyzed as functions of the pulse initial duration. Variations in the longitudinal and transverse components of the pulse electric field with the distance from the line are determined. Features of the spatial distribution of the energy carried by the pulse near the line are revealed. 相似文献
997.
A. A. Nechitaĭlov T. K. Zvonareva A. D. Remenyuk V. A. Tolmachev D. N. Goryachev O. S. El’tsina L. V. Belyakov O. M. Sreseli 《Semiconductors》2008,42(10):1249-1254
Catalytic properties of composite amorphous carbon-platinum layers produced by magnetron cosputtering have been studied. The layers were characterized by electron microscopy, IR spectroscopy, ellipsometry, gravimetry, and spectrophotometric chemical analysis. The catalytic activity of the layers was studied in an air-hydrogen fuel cell by measuring its load and power characteristics. 相似文献
998.
With the aim to reduce disorder and improve efficiency, nodes in an ad hoc network run a self-organization scheme to cooperatively organize the network. Although metrics such as complexity or self-stability are commonly used for evaluation, to the best of our knowledge, none of them quantifies the efficiency to build and maintain an organization (order). We henceforth apply the notion of entropy to ad hoc type wireless networks facilitating a quantification of the internal organizational state generated by different self-organization schemes. Invoking node and link failure probabilities, we expose the dependency of the organizational state on the self-organization protocol of choice. 相似文献
999.
Koch B. Hidayat A. Hongbin Zhang Mirvoda V. Lichtinger M. Sandel D. Noe R. 《Photonics Technology Letters, IEEE》2008,20(12):961-963
We demonstrate endless polarization stabilization with a control speed of up to 9 krad/s, over random Poincare sphere trajectories. These are in total >35 Mrad long, are composed in particular of difficult-to-track circles with all radii and orientations, and thereby include all possible worst cases. The maximum polarization mismatch and relative intensity errors are 0.13 rad and 0.43%, respectively. The controller runs on a field-programmable gate array and uses a commercial multistage LiNbO3 polarization transformer as the control device. 相似文献
1000.
Grobnic D. Mihailov S.J. Smelser C.W. Ramos R.T. 《Photonics Technology Letters, IEEE》2008,20(12):973-975
Strong fiber Bragg gratings were written through the standard polymer coatings of "off-the-shelf" high numerical aperture single-mode optical fibers after a few seconds exposure with femtosecond pulse durations of infrared radiation through a phase mask. While writing through the acrylate coating, we obtained index modulations of up to 1.4 x 10-3 and 7 x 10-4 with and without H2 -loading, respectively. 相似文献