全文获取类型
收费全文 | 240813篇 |
免费 | 4112篇 |
国内免费 | 725篇 |
专业分类
电工技术 | 4074篇 |
综合类 | 392篇 |
化学工业 | 38136篇 |
金属工艺 | 11145篇 |
机械仪表 | 7825篇 |
建筑科学 | 5287篇 |
矿业工程 | 2334篇 |
能源动力 | 5245篇 |
轻工业 | 17344篇 |
水利工程 | 3161篇 |
石油天然气 | 7865篇 |
武器工业 | 33篇 |
无线电 | 23439篇 |
一般工业技术 | 51308篇 |
冶金工业 | 42431篇 |
原子能技术 | 6839篇 |
自动化技术 | 18792篇 |
出版年
2021年 | 2752篇 |
2020年 | 2118篇 |
2019年 | 2506篇 |
2018年 | 4667篇 |
2017年 | 4559篇 |
2016年 | 4997篇 |
2015年 | 3135篇 |
2014年 | 4870篇 |
2013年 | 10905篇 |
2012年 | 7275篇 |
2011年 | 8935篇 |
2010年 | 7290篇 |
2009年 | 7855篇 |
2008年 | 8146篇 |
2007年 | 7946篇 |
2006年 | 6679篇 |
2005年 | 6021篇 |
2004年 | 5353篇 |
2003年 | 5182篇 |
2002年 | 4950篇 |
2001年 | 4948篇 |
2000年 | 4638篇 |
1999年 | 4749篇 |
1998年 | 12460篇 |
1997年 | 8606篇 |
1996年 | 6515篇 |
1995年 | 4796篇 |
1994年 | 4149篇 |
1993年 | 4357篇 |
1992年 | 3258篇 |
1991年 | 3233篇 |
1990年 | 3118篇 |
1989年 | 3075篇 |
1988年 | 3091篇 |
1987年 | 2716篇 |
1986年 | 2750篇 |
1985年 | 3137篇 |
1984年 | 2946篇 |
1983年 | 2767篇 |
1982年 | 2487篇 |
1981年 | 2515篇 |
1980年 | 2570篇 |
1979年 | 2547篇 |
1978年 | 2550篇 |
1977年 | 2763篇 |
1976年 | 3382篇 |
1975年 | 2324篇 |
1974年 | 2178篇 |
1973年 | 2321篇 |
1972年 | 2002篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Sebastian Roth Peter Stockinger Jakob Steff Simon Steimle Dr. Viktor Sautner Prof. Dr. Kai Tittmann Prof. Dr. Jürgen Pleiss Prof. Dr. Michael Müller 《Chembiochem : a European journal of chemical biology》2020,21(18):2615-2619
The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes. 相似文献
82.
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra 相似文献
83.
84.
85.
86.
87.
88.
89.
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
90.
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