全文获取类型
收费全文 | 33010篇 |
免费 | 2583篇 |
国内免费 | 1153篇 |
专业分类
电工技术 | 1048篇 |
综合类 | 2045篇 |
化学工业 | 13824篇 |
金属工艺 | 1539篇 |
机械仪表 | 795篇 |
建筑科学 | 2285篇 |
矿业工程 | 551篇 |
能源动力 | 2868篇 |
轻工业 | 3675篇 |
水利工程 | 339篇 |
石油天然气 | 1307篇 |
武器工业 | 235篇 |
无线电 | 847篇 |
一般工业技术 | 3763篇 |
冶金工业 | 769篇 |
原子能技术 | 199篇 |
自动化技术 | 657篇 |
出版年
2024年 | 126篇 |
2023年 | 502篇 |
2022年 | 1019篇 |
2021年 | 1224篇 |
2020年 | 1112篇 |
2019年 | 922篇 |
2018年 | 705篇 |
2017年 | 929篇 |
2016年 | 890篇 |
2015年 | 885篇 |
2014年 | 1557篇 |
2013年 | 1639篇 |
2012年 | 2322篇 |
2011年 | 2366篇 |
2010年 | 1904篇 |
2009年 | 1884篇 |
2008年 | 1643篇 |
2007年 | 2188篇 |
2006年 | 1996篇 |
2005年 | 1806篇 |
2004年 | 1512篇 |
2003年 | 1316篇 |
2002年 | 1057篇 |
2001年 | 935篇 |
2000年 | 856篇 |
1999年 | 699篇 |
1998年 | 555篇 |
1997年 | 467篇 |
1996年 | 343篇 |
1995年 | 276篇 |
1994年 | 264篇 |
1993年 | 205篇 |
1992年 | 186篇 |
1991年 | 116篇 |
1990年 | 70篇 |
1989年 | 62篇 |
1988年 | 42篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Here, we report on the application of corroles as analytically active compounds in liquid membrane electrodes (ISE) that are sensitive towards salicylic acid and salicylate.The potentiometric signals generated by corrole-incorporated ISEs strongly depend on the pH of the aqueous sample solution and the membrane composition, such as the presence of lipophilic sites. Corrole incorporating ISEs are characterised by a low detection limit (4.0 × 10−5 M) and a wide linear range (4.0 × 10−5 to 5.3 × 10−3 M). Also, they are free from interference versus other organic anions.The mechanism of the generation of the potentiometric signals of corrole incorporating ISEs in the presence of salicylate anion, as well salicylic acid, will be discussed. 相似文献
22.
介绍一种新型的恒通量的微滤膜———ISOFLUX 膜 ,该种膜的膜通量衰减比通常的微滤膜要小得多 ,对ISOFLUX 膜的原理和数学模型进行了推导 ,并给出了对牛奶进行冷杀菌过滤的结果 . 相似文献
23.
24.
High speedsteel (HSS) ,ischaracterizedbyex cellenthardness ,wearresistance ,and goodredhardness .Recently ,HSSisappliedtomanufacturehotrollingrollstoproducestripsofgoodshapeandsmallcrownwithextendedrollservicelife[1,2 ] .TheHSSisappliedtomanufacturerollcollarfor… 相似文献
25.
介绍了二次盐水及离子膜电解工序的主要设备和流程,对二次盐水及离子膜电解工序运行中出现的问题进行了分析,并提出了解决措施。 相似文献
26.
Herbert S. Bennett 《Journal of research of the National Institute of Standards and Technology》2007,112(4):209-221
In this paper, we present the theory for calculating Raman line shapes as functions of the Fermi energy and finite temperatures in zinc blende, n-type GaAs for donor densities between 1016 cm−3 and 1019 cm−3. Compared to other theories, this theory is unique in two respects: 1) the many-body effects are treated self-consistently and 2) the theory is valid at room temperature for arbitrary values of the ratio R = (Q2/α), where Q is the magnitude of the normalized wave vector and α is the normalized frequency used in the Raman measurements. These calculations solve the charge neutrality equation self-consistently for a two-band model of GaAs at 300 K that includes the effects of high carrier concentrations and dopant densities on the perturbed densities of states used to calculate the Fermi energy as a function of temperature. The results are then applied to obtain the carrier concentrations from Fermi energies in the context of line shapes in Raman spectra due to the coupling between longitudinal optical phonons and plasmons. Raman measurements have been proposed as a non-destructive method for wafer acceptance tests of carrier density in semiconductor epilayers. The interpretation of Raman spectra to determine the majority electron density in n-type semiconductors requires an interdisciplinary effort involving experiments, theory, and computer-based simulations and visualizations of the theoretical calculations. 相似文献
27.
Preparation of Compound Ultrafine CeO2 by Wet-Solid-Phase Mechanochemical Modification 总被引:1,自引:0,他引:1
To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process. 相似文献
28.
29.
膜分离法回收合成氨弛放气中氢气 总被引:1,自引:0,他引:1
介绍了膜分离的原理和应用。实践表明该方法具有效率高、流程简单、操作灵活容易、纯度高和收率高等优点。 相似文献
30.
Francisco Jos Alguacil Concepcin Caravaca María Isabel Martín 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(10):1048-1053
The transport of chromium(VI) through a flat‐sheet supported liquid membrane containing Cyanex 921 as a carrier has been investigated. The permeation of the metal is investigated as a function of various experimental variables: hydrodynamic conditions, concentration of chromium(VI) and HCl in the feed phase, carrier concentration and diluent in the membrane and strippant concentration in the stripping phase. The mass transfer coefficient and the thickness of the aqueous boundary layer were calculated from the experimental data. Furthermore, the selectivity of Cyanex 921‐based flat‐sheet supported liquid membrane towards different metal ions and the behaviour of the system against other carriers are presented. Copyright © 2003 Society of Chemical Industry 相似文献