全文获取类型
收费全文 | 159797篇 |
免费 | 2363篇 |
国内免费 | 659篇 |
专业分类
电工技术 | 3193篇 |
综合类 | 197篇 |
化学工业 | 25594篇 |
金属工艺 | 5907篇 |
机械仪表 | 5088篇 |
建筑科学 | 4915篇 |
矿业工程 | 394篇 |
能源动力 | 4133篇 |
轻工业 | 17938篇 |
水利工程 | 1208篇 |
石油天然气 | 644篇 |
武器工业 | 6篇 |
无线电 | 20960篇 |
一般工业技术 | 30335篇 |
冶金工业 | 25493篇 |
原子能技术 | 2456篇 |
自动化技术 | 14358篇 |
出版年
2019年 | 962篇 |
2018年 | 1255篇 |
2017年 | 1298篇 |
2016年 | 1451篇 |
2015年 | 1211篇 |
2014年 | 2012篇 |
2013年 | 7139篇 |
2012年 | 3547篇 |
2011年 | 5084篇 |
2010年 | 3936篇 |
2009年 | 4527篇 |
2008年 | 5026篇 |
2007年 | 5320篇 |
2006年 | 4737篇 |
2005年 | 4430篇 |
2004年 | 4283篇 |
2003年 | 4162篇 |
2002年 | 4148篇 |
2001年 | 4132篇 |
2000年 | 3898篇 |
1999年 | 3844篇 |
1998年 | 6779篇 |
1997年 | 5363篇 |
1996年 | 4596篇 |
1995年 | 3855篇 |
1994年 | 3479篇 |
1993年 | 3293篇 |
1992年 | 2901篇 |
1991年 | 2765篇 |
1990年 | 2709篇 |
1989年 | 2709篇 |
1988年 | 2549篇 |
1987年 | 2256篇 |
1986年 | 2204篇 |
1985年 | 2646篇 |
1984年 | 2406篇 |
1983年 | 2283篇 |
1982年 | 2122篇 |
1981年 | 2064篇 |
1980年 | 1918篇 |
1979年 | 1926篇 |
1978年 | 1837篇 |
1977年 | 2131篇 |
1976年 | 2606篇 |
1975年 | 1624篇 |
1974年 | 1470篇 |
1973年 | 1486篇 |
1972年 | 1236篇 |
1971年 | 1128篇 |
1970年 | 960篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
23.
24.
Hefei Zhao Xiaoqing Xie Paul Read Benjamin Loseke Stephen Gamet Wenkuan Li Changmou Xu 《International Journal of Food Science & Technology》2021,56(2):825-837
Enriching the micronutrients, selenium (Se) and lithium (Li), in grapes to improve their nutraceutical properties were implemented by foliar application of organic fertiliser rich in Se and Li onto five grape cultivars. The effects of this biofortification on vine vigour, fruit quality, overall micronutrients and phenolic compounds also were investigated. Agronomic biofortification was found greatly increased the Se and Li content in the whole grape by multiple times, meanwhile it did not significantly affect the vine vigour and fruit quality of grapes. However, the biofortification did impact the Ionome (including all the mineral nutrients and trace elements) and phenolic compounds in grapes and this varied among cultivars. This study demonstrated foliar spray of organic Se/Li fertiliser was a very effective strategy to biofortify these micronutrients in grape berries, particularly in the skin, and therefore might be a promising strategy to increase the consumption and awareness of these grapes. 相似文献
25.
Dr. Iain J. W. McKean Prof. Paul A. Hoskisson Prof. Glenn A. Burley 《Chembiochem : a European journal of chemical biology》2020,21(20):2890-2897
This Concept article describes the latest developments in the emerging area of late-stage biocatalytic alkylation. Central to these developments is the ability to efficiently prepare S-adenosyl methionine (SAM) cofactor analogues and couple this with enzymatic alkyl transfer. Recent developments in the enzymatic synthesis of SAM cofactor analogues are summarized first, followed by their application as alkyl transfer agents catalyzed by methyltransferases (MTases). Second, innovative methods to regenerate SAM cofactors by enzymatic cascades is reported. Finally, future opportunities towards establishing a generalized platform for late-stage alkylation are described. 相似文献
26.
27.
28.
The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ~4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015. 相似文献
29.
Steffen Vojacek Lukas Schulig Nathalie Wössner Norman Geist Prof. Dr. Walter Langel Prof. Dr. Manfred Jung Prof. Dr. Dennis Schade Prof. Dr. Andreas Link 《ChemMedChem》2019,14(8):853-864
Indoles are privileged structures in medicinal and bioorganic chemistry that are particularly well suited to serve as platforms for diversity. Among many other therapeutic areas, the indole scaffold has been used to design aromatic compounds useful to interfere with enzymes engaged in the regulation of substrate acylation status, such as sirtuins. However, the planarity of the indole ring is not necessarily optimal for all target enzymes, especially when functionalization with aromatic side chains is required. Replacement of flat scaffolds by nonplanar molecular cores dominated by sp3 hybridization is a common strategy to avoid the disadvantages associated with poor solubility and high promiscuity, while covering less-well-explored areas of chemical space. Thus, we synthesized fragment-like tetrahydroindoles suitable for fragment-based drug discovery as well as a well-characterized small library intended as multipurpose screening compounds. For proof of principle, these compounds were screened against sirtuins 1–3, enzymes known to be addressable by indoles. We found that 2,6,6-trimethyl-4-oxo-4,5,6,7-tetrahydro-1H-indole-3-carboxamides are potent and selective SIRT2 inhibitors. Compound 16 t displayed an IC50 value of 0.98 μm and could serve as exquisite starting point for hit-to-lead profiling. 相似文献
30.