全文获取类型
收费全文 | 101416篇 |
免费 | 7062篇 |
国内免费 | 3689篇 |
专业分类
电工技术 | 3825篇 |
技术理论 | 5篇 |
综合类 | 5828篇 |
化学工业 | 30511篇 |
金属工艺 | 2711篇 |
机械仪表 | 4023篇 |
建筑科学 | 4798篇 |
矿业工程 | 2183篇 |
能源动力 | 4644篇 |
轻工业 | 12110篇 |
水利工程 | 1464篇 |
石油天然气 | 26536篇 |
武器工业 | 379篇 |
无线电 | 1818篇 |
一般工业技术 | 3523篇 |
冶金工业 | 3745篇 |
原子能技术 | 373篇 |
自动化技术 | 3691篇 |
出版年
2024年 | 262篇 |
2023年 | 1070篇 |
2022年 | 2096篇 |
2021年 | 2662篇 |
2020年 | 2703篇 |
2019年 | 2716篇 |
2018年 | 2353篇 |
2017年 | 2803篇 |
2016年 | 3212篇 |
2015年 | 3035篇 |
2014年 | 5306篇 |
2013年 | 5430篇 |
2012年 | 6388篇 |
2011年 | 6803篇 |
2010年 | 5171篇 |
2009年 | 5130篇 |
2008年 | 4684篇 |
2007年 | 6033篇 |
2006年 | 6190篇 |
2005年 | 5500篇 |
2004年 | 4789篇 |
2003年 | 4532篇 |
2002年 | 3980篇 |
2001年 | 3400篇 |
2000年 | 3025篇 |
1999年 | 2455篇 |
1998年 | 1972篇 |
1997年 | 1638篇 |
1996年 | 1403篇 |
1995年 | 1171篇 |
1994年 | 957篇 |
1993年 | 642篇 |
1992年 | 568篇 |
1991年 | 427篇 |
1990年 | 335篇 |
1989年 | 266篇 |
1988年 | 163篇 |
1987年 | 111篇 |
1986年 | 84篇 |
1985年 | 158篇 |
1984年 | 119篇 |
1983年 | 104篇 |
1982年 | 78篇 |
1981年 | 49篇 |
1980年 | 34篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
62.
63.
Ming Chang Fangcheng Qiu Niannian Lan Tao Zhang Xin Guo Qingzhe Jin Ruijie Liu Xingguo Wang 《Lipids》2020,55(4):353-363
In China, Camellia oleifera oil (COO) is not only a common edible oil but also a traditional remedy widely applied to ameliorate a variety of illnesses associated with inflammation, such as mouth ulcers, thrush, eczema, etc. However, there has been a lack of relevant biological research on the anti-inflammatory capacity of COO, and the specific bioactive lipid phytochemicals contributing to the anti-inflammatory effect need further research. In this study, the RAW 264.7 macrophages model was used to investigate the anti-inflammatory capacity of COO. Our data showed that 33–200 μg/mL COO markedly inhibited the lipopolysaccharide lipopolysaccharide (LPS)-stimulated nitric oxide (NO.) secretion via the suppression of Nos2 and Cox-2 expression. The enzyme immunoassay confirmed that COO also exhibited a strong suppressive effect on the expression of proinflammatory cytokines such as Tnf-α and Il-6. To further explore the correlation between the anti-inflammatory effects and the lipid phytochemicals in COO, 10 samples were collected and screened for their chemical compositions. It was interestingly demonstrated that the polyphenol extracts of COO play a vital role in its anti-inflammatory properties. In addition, an oil-in-water (O/W) emulsion-based system was also developed to deliver the liposoluble COO into the cells, and the feasibility of this system was confirmed. Our research confirms the anti-inflammatory potential of COO and highlights that the main functional ingredient is polyphenol extracts. This may provide a scientific basis for the comprehensive utilization and development of COO and related functional foods. 相似文献
64.
65.
《International Journal of Hydrogen Energy》2021,46(64):32480-32489
Based on that hydrogen energy is widely used in fuel cells, we focus our interests on the design and research of new complexes that catalyze the reaction in both directions, such as hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs). A highly efficient catalyst for both hydrogen evolution and oxidation, based on a nickel(II) complex, [Ni-en-P2](ClO4)2, has been designed and provided by the reaction of Ni(ClO4)2 with N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) in our group. Its structure has been determined by X-ray diffraction. [Ni-en-P2](ClO4)2 can electro-catalyze hydrogen evolution both from acetic acid and a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 204 and 1327 mol of hydrogen per mole of catalyst per hour (H2/mol catalyst/h) under an overpotential (OP) of 914.6 mV and 836.6 mV, respectively. [Ni-en-P2](ClO4)2 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s−1 under an OP of 330 mV. The results can be attributed to that [NiII-en-P2](ClO4)2 has three good reversible redox waves at 1.01 (NiIII/II), −0.79 (NiII/I) and −1.38 V (NiI/0) versus Fc+/0, respectively. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation. 相似文献
66.
为有效解决前和煤业3#煤层东胶带大巷在原有锚网索支护下围岩变形量大的问题,结合巷道变形特征,确定采用钻孔卸压技术,采用理论分析和数值模拟的方式确定卸压钻孔在修巷作业前,垂直于巷帮打设,钻孔深度为8 m,结合巷道的具体条件确定巷道采用卸压钻孔+让压支护的围岩控制方案,并采用矿压监测验证支护效果。结果表明:支护方案实施后,顶底板和两帮的最大移近量分别为141 mm和132 mm,有效解决了巷道两帮及底板鼓起量大的问题,保证了巷道围岩的稳定性。 相似文献
67.
68.
69.
70.
Wax deposit properties are a significant concern in pipeline pigging during waxy crude oil transportation. In the present work, the impacts of flow conditions and oil properties on the wax precipitation characteristics of wax deposits are investigated. A flow loop apparatus was developed to conduct wax deposition experiments using four crude oils collected from different field pipes. The differential scanning calorimetry (DSC) technique was employed to observe the wax precipitation characteristics of crude oil and wax deposit. The results show that the wax content and the wax appearance temperature (WAT) of the deposits increase with shear stress and radial temperature gradient, and decrease with radial wax molecule concentration gradient near the pipe wall. The DSC tests on the wax deposits revealed that the deposit wax content is strongly correlated to the oil wax content. Furthermore, an empirical correlation was developed to predict the wax content and the WAT of the wax deposit. Verification of the empirical correlation using the different oils indicated that the average relative error of the wax content prediction and average absolute error of WAT prediction were 13.2% and 3.6°C, respectively. 相似文献