全文获取类型
收费全文 | 1247篇 |
免费 | 73篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 20篇 |
综合类 | 1篇 |
化学工业 | 433篇 |
金属工艺 | 31篇 |
机械仪表 | 43篇 |
建筑科学 | 27篇 |
能源动力 | 41篇 |
轻工业 | 111篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 69篇 |
一般工业技术 | 236篇 |
冶金工业 | 68篇 |
原子能技术 | 7篇 |
自动化技术 | 227篇 |
出版年
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 60篇 |
2020年 | 31篇 |
2019年 | 43篇 |
2018年 | 55篇 |
2017年 | 35篇 |
2016年 | 70篇 |
2015年 | 51篇 |
2014年 | 77篇 |
2013年 | 119篇 |
2012年 | 70篇 |
2011年 | 123篇 |
2010年 | 72篇 |
2009年 | 54篇 |
2008年 | 58篇 |
2007年 | 62篇 |
2006年 | 47篇 |
2005年 | 39篇 |
2004年 | 30篇 |
2003年 | 21篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1997年 | 21篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 7篇 |
1975年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有1323条查询结果,搜索用时 15 毫秒
1.
The observation of the immunomodulatory effects of opioid drugs opened the discussion about possible mechanisms of action and led researchers to consider the presence of opioid receptors (OR) in cells of the immune system. To date, numerous studies analyzing the expression of OR subtypes in animal and human immune cells have been performed. Some of them confirmed the expression of OR at both the mRNA and protein level, while others did not detect the receptor mRNA either. Although this topic remains controversial, further studies are constantly being published. The most recent articles suggested that the expression level of OR in human peripheral blood lymphocytes could help to evaluate the success of methadone maintenance therapy in former opioid addicts, or could serve as a biomarker for chronic pain diagnosis. However, the applicability of these findings to clinical practice needs to be verified by further investigations. 相似文献
2.
3.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
4.
5.
Lucie Vitejnov Vclav Lika Arvind Kumar Jana Ke
kov Ondej Vy
ítal Jan Brha Jan Bene Yaroslav Kolinko Tereza Blassov Zbynk Tonar Michaela Brychtov Marie Karlíkov Jaroslav Racek Hynek Mírka Petr Hoek Daniel Lysk Milena Krlí
kov 《International journal of molecular sciences》2021,22(9)
In liver surgery, biliary obstruction can lead to secondary biliary cirrhosis, a life-threatening disease with liver transplantation as the only curative treatment option. Mesenchymal stromal cells (MSC) have been shown to improve liver function in both acute and chronic liver disease models. This study evaluated the effect of allogenic MSC transplantation in a large animal model of repeated biliary obstruction followed by partial hepatectomy. MSC transplantation supported the growth of regenerated liver tissue after 14 days (MSC group, n = 10: from 1087 ± 108 (0 h) to 1243 ± 92 mL (14 days); control group, n = 11: from 1080 ± 95 (0 h) to 1100 ± 105 mL (14 days), p = 0.016), with a lower volume fraction of hepatocytes in regenerated liver tissue compared to resected liver tissue (59.5 ± 10.2% vs. 70.2 ± 5.6%, p < 0.05). Volume fraction of connective tissue, blood vessels and bile vessels in regenerated liver tissue, serum levels of liver enzymes (AST, ALT, ALP and GGT) and liver metabolites (albumin, bilirubin, urea and creatinine), as well as plasma levels of IL-6, IL-8, TNF-α and TGF-β, were not affected by MSC transplantation. In our novel, large animal (pig) model of repeated biliary obstruction followed by partial hepatectomy, MSC transplantation promoted growth of liver tissue without any effect on liver function. This study underscores the importance of translating results between small and large animal models as well as the careful translation of results from animal model into human medicine. 相似文献
6.
This work focuses mainly about swelling and rheological properties of calcium phosphate filled bacterial cellulose (BC)-based hydrogel scaffolds. Calcium phosphate is incorporated in the form of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) in different ratios, that is, 00:00, 10:90, 20:80, 40:60, 50:50, and 60:40. These scaffolds are also comprised with polyvinylpyrrolidone (PVP), poly(ethylene glycol), agar, and glycerin; designated as “BC-PVP” and “BC-PVP-β-TCP/HA.” All the hydrogel scaffolds are showing the notable viscoelastic property at 28 and 37 °C temperatures. The degree of swelling is found significant in BC-PVP-β-TCP/HA_50:50 scaffold and it is notably elastic at 37 °C after 5 min of swelling. However, after 60 min of swelling and at equilibrium swelling state, the elastic property of BC-PVP-β-TCP/HA_20:80 is revealed the highest. Considering the degree of swelling and rheological properties, the BC-PVP-β-TCP/HA_50:50 and BC-PVP-β-TCP/HA_20:80 hydrogel scaffolds found suitable for their application in bone tissue engineering or bone tissue regeneration. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48522. 相似文献
7.
8.
Miroslav Trnka Petr Hlavinka Mikhail A. Semenov 《Journal of the Royal Society Interface》2015,12(112)
Ways of increasing the production of wheat, the most widely grown cereal crop, will need to be found to meet the increasing demand caused by human population growth in the coming decades. This increase must occur despite the decrease in yield gains now being reported in some regions, increased price volatility and the expected increase in the frequency of adverse weather events that can reduce yields. However, if and how the frequency of adverse weather events will change over Europe, the most important wheat-growing area, has not yet been analysed. Here, we show that the accumulated probability of 11 adverse weather events with the potential to significantly reduce yield will increase markedly across all of Europe. We found that by the end of the century, the exposure of the key European wheat-growing areas, where most wheat production is currently concentrated, may increase more than twofold. However, if we consider the entire arable land area of Europe, a greater than threefold increase in risk was predicted. Therefore, shifting wheat production to new producing regions to reduce the risk might not be possible as the risk of adverse events beyond the key wheat-growing areas increases even more. Furthermore, we found a marked increase in wheat exposure to high temperatures, severe droughts and field inaccessibility compared with other types of adverse events. Our results also showed the limitations of some of the presently debated adaptation options and demonstrated the need for development of region-specific strategies. Other regions of the world could be affected by adverse weather events in the future in a way different from that considered here for Europe. This observation emphasizes the importance of conducting similar analyses for other major wheat regions. 相似文献
9.
10.