全文获取类型
收费全文 | 662772篇 |
免费 | 7773篇 |
国内免费 | 2364篇 |
专业分类
电工技术 | 11754篇 |
综合类 | 2755篇 |
化学工业 | 96701篇 |
金属工艺 | 27454篇 |
机械仪表 | 21439篇 |
建筑科学 | 15255篇 |
矿业工程 | 3344篇 |
能源动力 | 17684篇 |
轻工业 | 47360篇 |
水利工程 | 7011篇 |
石油天然气 | 10420篇 |
武器工业 | 29篇 |
无线电 | 81816篇 |
一般工业技术 | 131647篇 |
冶金工业 | 112964篇 |
原子能技术 | 12711篇 |
自动化技术 | 72565篇 |
出版年
2022年 | 3570篇 |
2021年 | 5423篇 |
2020年 | 4118篇 |
2019年 | 5179篇 |
2018年 | 22059篇 |
2017年 | 21029篇 |
2016年 | 18495篇 |
2015年 | 6478篇 |
2014年 | 10067篇 |
2013年 | 28283篇 |
2012年 | 18415篇 |
2011年 | 29805篇 |
2010年 | 24502篇 |
2009年 | 24270篇 |
2008年 | 26068篇 |
2007年 | 26720篇 |
2006年 | 17573篇 |
2005年 | 16682篇 |
2004年 | 15859篇 |
2003年 | 15962篇 |
2002年 | 14497篇 |
2001年 | 14331篇 |
2000年 | 13441篇 |
1999年 | 14061篇 |
1998年 | 35934篇 |
1997年 | 24882篇 |
1996年 | 19235篇 |
1995年 | 14392篇 |
1994年 | 12692篇 |
1993年 | 12613篇 |
1992年 | 9069篇 |
1991年 | 8691篇 |
1990年 | 8546篇 |
1989年 | 8074篇 |
1988年 | 7772篇 |
1987年 | 6712篇 |
1986年 | 6540篇 |
1985年 | 7233篇 |
1984年 | 6622篇 |
1983年 | 6161篇 |
1982年 | 5673篇 |
1981年 | 5681篇 |
1980年 | 5348篇 |
1979年 | 5131篇 |
1978年 | 4965篇 |
1977年 | 5805篇 |
1976年 | 7767篇 |
1975年 | 4265篇 |
1974年 | 4066篇 |
1973年 | 4083篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
S. Otakulov 《Cybernetics and Systems Analysis》1994,30(3):458-462
Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 172–176, May–June, 1994 相似文献
85.
86.
Nutrient uptake by the hindlimb was investigated utilising the arteriovenous difference technique in 5 Thoroughbred horses fed to maintenance a diet of 100% roughage or 52% oat grain and 48% roughage. Arterial blood was obtained from a catheter inserted into the carotid artery while venous blood was simultaneously collected from a catheter placed into the iliac vein via the medial saphenous vein. The arteriovenous difference for glucose was significant and represented a mean extraction of 10 +/- 1% with no effect of diet. If fully oxidised, glucose uptake (corrected for lactate and pyruvate arteriovenous difference) was sufficient to account for 78 +/- 13% or 107 +/- 15% of the oxygen consumed by the hindlimb in horses fed a roughage or 52% oat grain diet respectively. Acetate was also a major metabolite of the hindlimb, showing a 39 +/- 5% extraction with no effect of diet. However, the 52% oat grain diet did induce a significant decline in the concentration of acetate in arterial blood. The potential contribution to oxidation in the hindlimb was significantly reduced from 32 +/- 4% in horses fed roughage to 21 +/- 3% when fed 52% oat grain. D-3-Hydroxybutyrate uptake could account for 9 +/- 1% of the oxidation by the hindlimb with no effect of diet. The technique for measuring nutrient uptake across the hindlimb using the arteriovenous difference is relatively simple and would be valuable in investigating fuel use by muscle during exercise. 相似文献
87.
An extended logistic model with a varying asymptotic upper bound for long-range peak demand forecasting is described. The model has been applied to a typical fast growing system, the Saudi Consolidated Electric Company. The forecasts are compared with actual demands and with those obtained from classical forecasting methods. The model gave relatively accurate peak demand forecasts compared with other classical methods. The model with a single load observation is capable of producing several peak demand forecasts corresponding to different levels of maximum temperature and various levels of social activity. The forecasts produced by the model were also stable irrespective of the length of the ex-post simulation period 相似文献
88.
This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate. 相似文献
89.
A novel class of narrow-band tunable wavelength filters is proposed and evaluated. Wavelength selectivity of the proposed filters Is derived from the finite time response of an optical nonlinearity. The nonlinearity is gain saturation in semiconductor optical amplifier structures. The filters are shown to have very narrow passbands tunable over the entire semiconductor gain bandwidth. The key to filter implementation is a device configuration in which the wave-mixing products can be isolated from the amplified inputs. Three integrated optics compatible configurations are considered and shown to have high filter throughputs 34 to 180% and subangstrom bandwidths 相似文献
90.
V. A. Arzamastsev N. L. Sardaev A. S. Kochergin 《Metal Science and Heat Treatment》1996,38(11):477-479
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described. 相似文献