全文获取类型
收费全文 | 85577篇 |
免费 | 192篇 |
国内免费 | 88篇 |
专业分类
电工技术 | 1882篇 |
综合类 | 94篇 |
化学工业 | 10963篇 |
金属工艺 | 7522篇 |
机械仪表 | 6261篇 |
建筑科学 | 1524篇 |
矿业工程 | 912篇 |
能源动力 | 776篇 |
轻工业 | 1379篇 |
水利工程 | 1293篇 |
石油天然气 | 2168篇 |
武器工业 | 1篇 |
无线电 | 8023篇 |
一般工业技术 | 22437篇 |
冶金工业 | 6898篇 |
原子能技术 | 1431篇 |
自动化技术 | 12293篇 |
出版年
2018年 | 9354篇 |
2017年 | 10032篇 |
2016年 | 5301篇 |
2015年 | 651篇 |
2014年 | 218篇 |
2013年 | 214篇 |
2012年 | 2993篇 |
2011年 | 9232篇 |
2010年 | 8863篇 |
2009年 | 7550篇 |
2008年 | 7281篇 |
2007年 | 9510篇 |
2006年 | 192篇 |
2005年 | 4068篇 |
2004年 | 2307篇 |
2003年 | 1923篇 |
2002年 | 809篇 |
2001年 | 175篇 |
2000年 | 258篇 |
1999年 | 90篇 |
1998年 | 92篇 |
1997年 | 83篇 |
1993年 | 85篇 |
1992年 | 95篇 |
1991年 | 109篇 |
1989年 | 92篇 |
1988年 | 118篇 |
1987年 | 96篇 |
1986年 | 85篇 |
1980年 | 83篇 |
1979年 | 100篇 |
1978年 | 119篇 |
1976年 | 93篇 |
1975年 | 97篇 |
1974年 | 110篇 |
1973年 | 106篇 |
1972年 | 109篇 |
1969年 | 124篇 |
1968年 | 177篇 |
1967年 | 166篇 |
1966年 | 183篇 |
1965年 | 165篇 |
1964年 | 92篇 |
1961年 | 93篇 |
1960年 | 106篇 |
1958年 | 87篇 |
1957年 | 131篇 |
1956年 | 123篇 |
1955年 | 139篇 |
1954年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
A consistent analytical model of nonlinear ion drift spectrometry for modern gas analyzers is developed. A procedure for determining the field dependence of the ion mobility using the experimental data is described. An ionogram is calculated for the case of a flat drift chamber and polynomial character of the field dependence of the ion mobility. 相似文献
132.
S. Zh. Davrenbekov E. S. Mustafin B. K. Kasenov S. T. Edil'baeva Sh. B. Kasenova E. K. Zhumadilov Zh. I. Sagintaeva 《Inorganic Materials》2004,40(9):976-978
NdMCr2O5 (M = Na, K, Cs) and NdMgCr2O5.5 are prepared by solid-state reactions between appropriate oxides and carbonates and are shown to have a tetragonal structure. The heat capacity of these chromites, measured from 298.15 to 673 K, exhibits sharp changes attributable to second-order phase transitions. The C
p
0(T) data are represented by quadratic best fit equations. The electrical resistivity of the chromites is measured between 303 and 493 K. The results attest to semiconducting behavior of the materials in certain temperature ranges. 相似文献
133.
N. A. Ashurbekov K. O. Iminov V. S. Kobzeva O. V. Kobzev 《Technical Physics Letters》2007,33(6):517-520
The spatial structure of visible emission from plasma of a transverse nanosecond pulsed electric discharge in a gas-filled diode with a hollow (slit) cathode has been experimentally studied. A relation is established between the regime of electron energy relaxation and the plasma-beam discharge structure formation. High values of the electron emission coefficient are observed in the experiment, which cannot be explained using the notion of electron emission from a cathode bombarded by fast heavy particles. 相似文献
134.
V. N. Perevezentsev M. Yu. Shcherban’ M. Yu. Murashkin R. Z. Valiev 《Technical Physics Letters》2007,33(8):648-650
The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10?3 to 1 s?1. 相似文献
135.
Broadband chaotic oscillations were monitored in a depressed potential collector of a traveling-wave oscillator (TWO). This signal appears due to the oscillations of a virtual cathode, which is formed in the spent electron beam under the action of retarding fields existing in the multistage depressed collector. 相似文献
136.
V. V. Mamutin O. V. Bondarenko A. P. Vasil’ev A. G. Gladyshev A. Yu. Egorov N. V. Kryzhanovskaya V. S. Mikhrin V. M. Ustinov 《Technical Physics Letters》2007,33(5):384-387
The optical properties of heterostructures comprising InAs/InGaAsN quantum wells in strain-compensated GaAsN/InGaAsN superlattices have been studied. It is demonstrated that, using such superlattices of various design and thickness and with additional InAs monolayer spacers, it is possible to control the wavelength of room-temperature emission from InGaAsN quantum wells within 1.3–1.6 μm without deteriorating the output radiation characteristics, which opens additional prospects for the development of lasers on GaAs substrates for telecommunication applications. 相似文献
137.
M. I. Danielyan K. S. Kulakov S. L. Kulakov V. L. Tumanov M. E. Kompan 《Technical Physics Letters》2007,33(7):597-599
A considerable (~1.4-fold) increase in the average output power of a chemical current source has been achieved by means of a periodic pulsed manipulation of the load. A scheme used for the pulse-train loading is presented and mechanisms ensuring an increase in the average output power of the current source are considered. 相似文献
138.
V. Yu. Karpov 《Materials Science》2007,43(5):746-749
We developed a new type of porous materials with anisotropic structure based on a large number of metals. It is shown that
these material, called gasars, have properties different from the properties of the other porous materials. Thus, the strength
of gasars is much higher than the strength of powder materials with the same porosity and their impact toughness is readily
regulated by the sizes of the pores. The internal structures of gasars and possible versions of the types of pores in these
materials are strongly diversified, which makes the spectrum of their possible applications very wide. We discuss some specific
directions of the potential applications of gasars. The results of measurements of the thermal conductivity of gasars and
monolithic specimens are presented. It is shown that, for a certain level of porosity, the specific thermal conductivity of
gasars is higher than for monolithic materials. We also make some basic conclusions concerning the characteristics of new
porous materials.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 5, pp. 125–127, September–October, 2007. 相似文献
139.
Ér. V. Kal’yanov 《Technical Physics Letters》2007,33(6):451-453
A new simple model of a system with chaotic dynamics, based on the equations of bistable systems, is considered. The possibility of converting harmonic signals into chaotic oscillations, which represent intermittent irregular and switching quasi-regular motions, is demonstrated by numerical methods. The mechanism of chaotization is analyzed using the results of numerical calculations. 相似文献
140.
D. I. Zolotarevskaya 《Journal of Engineering Physics and Thermophysics》2007,80(5):977-988
This paper considers problems on the rolling of rigid driven and driving cylinders slipping on a compactible viscoelastic
base. As a result of the investigation of the process of propagation of viscoelastic decaying strain waves in a deformable
medium caused by a cylinder rolling over it and the action of the sliding friction forces, formulas and calculation algorithms
have been obtained for determining the indices of the stressed-strained state and compactness of the base, the rolling resistance
of the driven and diving cylinders, and the driving force of the driving cylinder. Calculations of these indices have been
performed for the cases of cylinders rolling over a soil whose viscoelastic properties have been investigated experimentally.
__________
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 122–132, September–October, 2007. 相似文献