全文获取类型
收费全文 | 568225篇 |
免费 | 7160篇 |
国内免费 | 1004篇 |
专业分类
电工技术 | 10533篇 |
综合类 | 467篇 |
化学工业 | 90627篇 |
金属工艺 | 23375篇 |
机械仪表 | 18549篇 |
建筑科学 | 12597篇 |
矿业工程 | 4314篇 |
能源动力 | 14523篇 |
轻工业 | 45914篇 |
水利工程 | 6949篇 |
石油天然气 | 14965篇 |
武器工业 | 39篇 |
无线电 | 60527篇 |
一般工业技术 | 116674篇 |
冶金工业 | 95659篇 |
原子能技术 | 14692篇 |
自动化技术 | 45985篇 |
出版年
2021年 | 5541篇 |
2020年 | 4066篇 |
2019年 | 5321篇 |
2018年 | 9265篇 |
2017年 | 9462篇 |
2016年 | 9917篇 |
2015年 | 6085篇 |
2014年 | 10338篇 |
2013年 | 26269篇 |
2012年 | 15944篇 |
2011年 | 21297篇 |
2010年 | 17134篇 |
2009年 | 18957篇 |
2008年 | 19208篇 |
2007年 | 18911篇 |
2006年 | 16387篇 |
2005年 | 14825篇 |
2004年 | 14071篇 |
2003年 | 13740篇 |
2002年 | 13294篇 |
2001年 | 12894篇 |
2000年 | 12361篇 |
1999年 | 12048篇 |
1998年 | 27694篇 |
1997年 | 20069篇 |
1996年 | 15646篇 |
1995年 | 12019篇 |
1994年 | 10871篇 |
1993年 | 10627篇 |
1992年 | 8351篇 |
1991年 | 8112篇 |
1990年 | 7998篇 |
1989年 | 7768篇 |
1988年 | 7482篇 |
1987年 | 6756篇 |
1986年 | 6538篇 |
1985年 | 7392篇 |
1984年 | 6703篇 |
1983年 | 6441篇 |
1982年 | 5779篇 |
1981年 | 5896篇 |
1980年 | 5630篇 |
1979年 | 5734篇 |
1978年 | 5665篇 |
1977年 | 6181篇 |
1976年 | 7688篇 |
1975年 | 5109篇 |
1974年 | 4903篇 |
1973年 | 4980篇 |
1972年 | 4279篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
High Temperature - The temperature dependences of the viscosity of liquid Fe90B x Si(10 − x) alloys are studied in the mode of heating and subsequent cooling. The temperature dependences of... 相似文献
162.
163.
Adebisi A. Okeleye 《Chemical Engineering Communications》2019,206(9):1181-1198
In this work, the effects of solid/solvent ratio (0.10–0.25?g/ml), extraction time (3–8?h), and solvent type (n-hexane, ethyl acetate, and acetone) together with their shared interactions on Kariya seed oil (KSO) yield were investigated. The oil extraction process was modeled via response surface methodology (RSM), artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) while the optimization of the three input variables essential to the oil extraction process was carried out by genetic algorithm (GA) and RSM methods. The low mean relative percent deviation (MRPD) of 0.94–4.69% and high coefficient of determination (R2) > 0.98 for the models developed demonstrate that they describe the solvent extraction process with high accuracy in this order: ANFIS, ANN, and RSM. The best operating condition (solid/solvent ratio of 0.1?g/ml, extraction time of 8?h, and acetone as solvent of extraction) that gave the highest KSO yield (32.52?wt.%) was obtained using GA-ANFIS and GA-ANN. Solvent extraction efficiency evaluation showed that ethyl acetate, n-hexane, and acetone gave maximum experimental oil yields of 19.20?±?0.28, 25.11?±?0.01, and 32.33?±?0.04?wt.%, respectively. Properties of the KSO varied based on the type of solvent used. The results of this work showed that KSO could function as raw material in both food and chemical industries. 相似文献
164.
Russian Engineering Research - Formulas are derived for the most important parameters of channel extrusion. 相似文献
165.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
166.
Salman M.A. Salman 《国际水资源开发杂志》2015,31(1):4-16
The United Nations Watercourses Convention entered into force on 17 August 2014, following a long and complex journey that dates back to 1970 when the UN referred the matter to its legal arm, the International Law Commission. This article follows the Convention through that long and turbulent road, examines its main provisions and analyses the reasons for the delay of its entry into force. It concludes by answering the question of why entry into force of the Convention should indeed matter. 相似文献
167.
168.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
169.
170.