全文获取类型
收费全文 | 14264篇 |
免费 | 1835篇 |
国内免费 | 787篇 |
专业分类
电工技术 | 94篇 |
技术理论 | 1篇 |
综合类 | 748篇 |
化学工业 | 7168篇 |
金属工艺 | 371篇 |
机械仪表 | 345篇 |
建筑科学 | 152篇 |
矿业工程 | 152篇 |
能源动力 | 158篇 |
轻工业 | 1953篇 |
水利工程 | 24篇 |
石油天然气 | 1435篇 |
武器工业 | 140篇 |
无线电 | 1092篇 |
一般工业技术 | 2165篇 |
冶金工业 | 158篇 |
原子能技术 | 172篇 |
自动化技术 | 558篇 |
出版年
2024年 | 71篇 |
2023年 | 374篇 |
2022年 | 419篇 |
2021年 | 865篇 |
2020年 | 611篇 |
2019年 | 599篇 |
2018年 | 525篇 |
2017年 | 498篇 |
2016年 | 589篇 |
2015年 | 578篇 |
2014年 | 835篇 |
2013年 | 1003篇 |
2012年 | 1003篇 |
2011年 | 957篇 |
2010年 | 677篇 |
2009年 | 721篇 |
2008年 | 588篇 |
2007年 | 783篇 |
2006年 | 752篇 |
2005年 | 661篇 |
2004年 | 556篇 |
2003年 | 460篇 |
2002年 | 387篇 |
2001年 | 382篇 |
2000年 | 298篇 |
1999年 | 239篇 |
1998年 | 213篇 |
1997年 | 161篇 |
1996年 | 189篇 |
1995年 | 157篇 |
1994年 | 119篇 |
1993年 | 107篇 |
1992年 | 94篇 |
1991年 | 80篇 |
1990年 | 63篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 34篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1959年 | 1篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
51.
52.
53.
Mohamed Janshir Bin Gulam Mohamed Hafiz Abdul Mannan Rizwan Nasir Dzeti Farhah Mohshim Hilmi Mukhtar Aymn Abdulrahman Anas Ahmed 《应用聚合物科学杂志》2020,137(12):48476
Membrane technology has been considered a key factor for sustainable growth in high-efficiency gas separation. Current mixed matrix membranes (MMMs) technology is rising, but these membranes in the dense structure are having difficulties in operating at high pressures and scale up for commercialization. The purpose of this research is to synthesize composite MMMs (CMMMs) consisting of polyethersulfone (PES), carbon molecular sieve (CMS 1–5 wt %), and Novatex 2471 nonwoven fabric (support layer). The membranes' physical, chemical, and thermal properties were evaluated by different analytical equipment. The morphology of both PES and PES-CMS composite membranes had a porous and asymmetric structure, in which CMS was uniformly distributed in the polymer matrix. The thermal properties showed that the membranes were stable up to 350 °C with a single glass transition temperature. The functional groups in the membrane were confirmed by spectral analysis. The gas performance results showed that carbon dioxide permeance increased with increased CMS concentration and methane permeance decreased due to the hindering effect of CMS under similar operating conditions. The highest selectivity achieved was 12.774 using CMMM of 5 wt % of CMS at 10 bar, which on average was 137.80%, improved selectivity compared to pure PES membrane. The support layer was able to withstand high operating pressures and showed the ability to scale up. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48476. 相似文献
54.
Meng Guo Masakoto Kanezashi Hiroki Nagasawa Liang Yu Kazuki Yamamoto Takahiro Gunji Toshinori Tsuru 《American Institute of Chemical Engineers》2020,66(4):e16850
Fine-tuned, molecular-composite, organosilica membranes were fabricated via the co-condensation of organosilica precursors bis(triethoxysilyl)acetylene (BTESA) and bis(triethoxysilyl)benzene (BTESB). Fourier transform infrared and UV–vis spectra confirmed the co-condensation behaviors of BTESA and BTESB. The evolution of the network structure indicated that the incorporated BTESB decreased the membrane pore size, which was determined by a modified gas translation model according to the steric effect of the phenyl groups. The incorporation of BTESB to BTESA finely tuned the membrane structure and endowed the resultant composite membrane with improved separation properties. The BTESAB 9:1 membrane (molar ratio of BTESA/BTESB was 9:1) exhibited high C3H6 permeance at 4.5 × 10−8 mol m−2 s−1 Pa−1 and a C3H6/C3H8 permeance ratio of 33 at 50°C. One of the most important developments of this study involved clearly defining the relationship between membrane pore size and C3H6/C3H8 separation performance for organosilica membranes in single and binary separation systems. 相似文献
55.
Understanding interactions between functionalized gold nanoparticles (NPs) and lipid bilayers is essential for biomedical applications. Experiments have shown that NPs that are stable in solution can assemble into clusters when adsorbed to a lipid bilayer, suggesting that bilayer-mediated interactions facilitate assembly. In this work, we use coarse-grained molecular dynamics simulations to study bilayer-mediated interactions between NPs adsorbed to single- and multicomponent lipid bilayers. We perform unbiased simulations and umbrella sampling calculations using an implicit solvent force field to determine the thermodynamic contributions to assembly. We show that bilayer-mediated interactions drive the assembly of NPs into linear aggregates on liquid-disordered bilayers, which we attribute to a reduction in bilayer curvature. Similar bilayer-mediated interactions induce the alignment of NP clusters with phase boundaries in phase-separated bilayers. Together, these simulation results provide new physical insight into the balance of forces that dictate the assembly of charged NPs at multicomponent lipid bilayer interfaces. 相似文献
56.
采用固定床反应器分别探究了三类催化剂(固体磷酸催化剂、酸性阳离子交换树脂催化剂以及分子筛催化剂)对异丁烯齐聚过程的影响。实验结果表明:固体磷酸催化剂适用于C8烯烃的生产,酸性阳离子树脂催化剂及改性的分子筛催化剂(Hβ)适合生产C12烯烃。异丁烯齐聚产物C8~C16(清洁燃料油)因无芳烃、无硫,在石化工业中具有非常广泛的应用潜力;由三种类催化剂的评价结果来看,C8~C16的选择性最高时均能接近100%,但是固体磷酸催化剂和酸性阳离子树脂催化剂的异丁烯原料转化率比Hβ分子筛催化剂低,Hβ催化作用下异丁烯转化率可以达到88%。 相似文献
57.
由于挥发性有机物(VOCs)会对环境造成严重的危害,因此VOCs的处理一直备受人们的关注,但发展高效的VOCs处理技术仍然存在严峻的挑战。本文针对大风量、低浓度VOCs的处理展开了综述,重点围绕吸附、催化燃烧处理展开讨论。对于大风量的低浓度VOCs,虽然浓度较低但VOCs排放量非常巨大。通过VOCs浓缩技术,提高浓度减少风量成为降低VOCs处理成本的有效途径。其中,发展高性能VOCs吸附材料是VOCs浓缩技术的关键。阐明了活性炭、分子筛等重要吸附材料的性质及其吸附VOCs的原理,并对吸附材料性质和VOCs种类对吸附效果的影响进行了探讨。展望了活性炭浓缩-催化燃烧技术和分子筛转轮浓缩-催化燃烧技术在大风量的低浓度VOCs处理中的应用前景。 相似文献
58.
59.
Dr. Lei Huang Jan Philipp Bittner Dr. Pablo Domínguez de María Dr. Sven Jakobtorweihen Prof. Dr. Selin Kara 《Chembiochem : a European journal of chemical biology》2020,21(6):811-817
The use of oxidoreductases (EC1) in non-conventional reaction media has been increasingly explored. In particular, deep eutectic solvents (DESs) have emerged as a novel class of solvents. Herein, an in-depth study of bioreduction with an alcohol dehydrogenase (ADH) in the DES glyceline is presented. The activity and stability of ADH in mixtures of glyceline/water with varying water contents were measured. Furthermore, the thermodynamic water activity and viscosity of mixtures of glyceline/water have been determined. For a better understanding of the observations, molecular dynamics simulations were performed to quantify the molecular flexibility, hydration layer, and intraprotein hydrogen bonds of ADH. The behavior of the enzyme in DESs follows the classic dependence of water activity (aW) in non-conventional media. At low aW values (<0.2), ADH does not show any activity; at higher aW values, the activity was still lower than that in pure water due to the high viscosities of the DES. These findings could be further explained by increased enzyme flexibility with increasing water content. 相似文献
60.
Prof. Dr. Roger Alberto 《Chembiochem : a European journal of chemical biology》2020,21(19):2743-2749
The complex [99mTc(OH2)3(CO)3]+ has become a versatile building block in radiopharmaceutical chemistry, applied by many groups worldwide. However, despite widespread efforts, only one compound has made it right the way through clinical trials. Along the way from its discovery to its development into an eventual product, the author experienced issues that he would handle differently in retrospect. In this article, these experiences are turned into “lessons” that might be helpful for young researchers finding themselves in similar situations. Beside issues with patenting and company strategies, the carbonyl story has provided scientific implications beyond its own story, and insights from which any future 99mTc-based chemistry for radiopharmacy or molecular imaging might benefit. 相似文献