全文获取类型
收费全文 | 176279篇 |
免费 | 1427篇 |
国内免费 | 200篇 |
专业分类
电工技术 | 2691篇 |
综合类 | 132篇 |
化学工业 | 27435篇 |
金属工艺 | 9581篇 |
机械仪表 | 5851篇 |
建筑科学 | 3173篇 |
矿业工程 | 1920篇 |
能源动力 | 2806篇 |
轻工业 | 9503篇 |
水利工程 | 2773篇 |
石油天然气 | 8876篇 |
武器工业 | 13篇 |
无线电 | 15257篇 |
一般工业技术 | 39198篇 |
冶金工业 | 30867篇 |
原子能技术 | 7026篇 |
自动化技术 | 10804篇 |
出版年
2018年 | 3025篇 |
2017年 | 3145篇 |
2016年 | 3414篇 |
2015年 | 1723篇 |
2014年 | 3037篇 |
2013年 | 6517篇 |
2012年 | 4474篇 |
2011年 | 5748篇 |
2010年 | 4649篇 |
2009年 | 5093篇 |
2008年 | 5164篇 |
2007年 | 5214篇 |
2006年 | 4332篇 |
2005年 | 4012篇 |
2004年 | 3817篇 |
2003年 | 3682篇 |
2002年 | 3596篇 |
2001年 | 3604篇 |
2000年 | 3512篇 |
1999年 | 3416篇 |
1998年 | 7740篇 |
1997年 | 5587篇 |
1996年 | 4183篇 |
1995年 | 3138篇 |
1994年 | 2799篇 |
1993年 | 2974篇 |
1992年 | 2390篇 |
1991年 | 2438篇 |
1990年 | 2539篇 |
1989年 | 2463篇 |
1988年 | 2448篇 |
1987年 | 2299篇 |
1986年 | 2376篇 |
1985年 | 2410篇 |
1984年 | 2286篇 |
1983年 | 2217篇 |
1982年 | 2053篇 |
1981年 | 2257篇 |
1980年 | 2116篇 |
1979年 | 2342篇 |
1978年 | 2503篇 |
1977年 | 2540篇 |
1976年 | 3269篇 |
1975年 | 2299篇 |
1974年 | 2361篇 |
1973年 | 2393篇 |
1972年 | 2191篇 |
1971年 | 1946篇 |
1970年 | 1731篇 |
1969年 | 1658篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
913.
Abstract There are still many institutions of higher education in the UK, both universities and polytechnics, that have not taken on board the application of information technology to foreign language learning. Apart from considerations of cost, there is also the problem of time—deciding how best to use the limited time at one's disposal for exploring computer applications to foreign language learning. Both problems may be compounded by the mistaken belief that effective use of this 'new' technology necessarily involves learning one or more programming languages. This paper endeavours to show that recent advances in both software and hardware have produced computing tools of particular interest to translation and the translator, and that, since translation is a reality for large numbers of undergraduates in the UK, such tools represent an obvious starting point for the introduction of IT into the undergraduate curriculum. 相似文献
914.
915.
Valla M. Montagna G. Castello R. Tonietto R. Bietti I. 《Solid-State Circuits, IEEE Journal of》2005,40(4):970-977
A direct conversion 802.11a receiver front-end including a synthesizer with quadrature VCO has been integrated in a 0.13-/spl mu/m CMOS process. The chip has an active area of 1.8 mm/sup 2/ with the entire RF portion operated from 1.2 V and the low frequency portion operated from 2.5 V. Its key features are a current driven passive mixer with a low impedance load that achieves a low 1/f noise corner and an high I-Q accuracy quadrature VCO. Measured noise figure is 3.5 dB with an 1/f noise corner of 200 kHz, and an IIP3 of -2 dBm. The synthesizer DSB phase noise integrated over a 10 MHz band is less than -36 dBc while its I-Q phase unbalance is below 1 degree. 相似文献
916.
A possible method for the simulation of nonideal op-amps with a finite gain and bandwidth by means of an equivalent SC circuit, containing ideal components, is presented. The approach is extended by the case of an op-amp with non-switched input SC building blocks. 相似文献
917.
S. A. Bulgakov V. B. Ryabov V. I. Shnyrkov D. M. Vavriv 《Journal of Low Temperature Physics》1991,83(5-6):241-255
The oscillation dynamics of a nonhysteretic, one-contact superconducting quantum interferometer under low-frequency modulation of an external magnetic flux has been studied. It is shown that even in the case of adiabatic, equilibrium, and nonhysteretic operation modes of a superconducting ring enclosed by a weak link, there can appear chaotic oscillations. The conditions of chaos arising have been considered analytically and numerically; mechanisms and destruction scenarios of periodic oscillations have been studied. The stochastic instability could impose limitations on the increase in sensitivity of nonhysteretic SQUIDs, which was earlier predicted to be high enough. 相似文献
918.
N. I. Gamayunov S. N. Gamayunov 《Journal of Engineering Physics and Thermophysics》2004,77(5):953-964
Approximate (consistent with experiments) methods of solution of problems of freezing of moist grounds of semiinfinite and finite length with different boundary conditions have been proposed. Methods of obtaining the parameters of transfer of heat and moisture from experiments have been given. The analytical and experimental results obtained have been discussed. 相似文献
919.
T. S. Shamirzaev A. I. Toropov A. K. Bakarov K. S. Zhuravlev A. Yu. Kobitski H. P. Wagner D. R. T. Zahn 《Semiconductors》2006,40(5):527-533
The stationary and time-resolved polariton radiation in ultrahigh quality AIGaAs layers have been studied. It has been found
that elastic exciton-exciton collisions lead to the appearance of a low-energy line of polariton radiation. We show that the
rate of exciton-to-polariton transitions caused by elastic exciton-exciton collisions is determined not only by the density
of the excitonic gas, but also by its temperature; this is in accordance with existing theoretical predictions.
The text was submitted by the authors in English. 相似文献
920.
Stress State of Bent Buried Pipelines 总被引:1,自引:0,他引:1
The authors consider edge effects in buried pipelines that occur in the region of joining of a straight buried pipe and a bent insert (factory bend, elbow, or an elastically bent segment). The action of those effects results in the appearance of additional bending moments, which are proportional to the difference between the axial force in an infinite straight pipeline and that in a closed-end pipe, and depend on the geometrical parameters of the pipeline and physical-mechanical characteristics of the soil. Specific examples of analysis of elastic interaction of a pipeline with the soil for pipe bends with various radii of the bend arc are offered. It is shown that additional bending stresses may exceed appreciably the stresses from the axial force, and therefore, they should be taken into account when designing and building pipelines. The solution for an elastically bent segment has been obtained and analyzed. 相似文献