全文获取类型
收费全文 | 75286篇 |
免费 | 8684篇 |
国内免费 | 5141篇 |
专业分类
电工技术 | 6794篇 |
技术理论 | 4篇 |
综合类 | 6663篇 |
化学工业 | 10154篇 |
金属工艺 | 4610篇 |
机械仪表 | 5074篇 |
建筑科学 | 6280篇 |
矿业工程 | 2989篇 |
能源动力 | 2096篇 |
轻工业 | 5940篇 |
水利工程 | 2103篇 |
石油天然气 | 3579篇 |
武器工业 | 1180篇 |
无线电 | 9093篇 |
一般工业技术 | 6874篇 |
冶金工业 | 2974篇 |
原子能技术 | 1035篇 |
自动化技术 | 11669篇 |
出版年
2024年 | 252篇 |
2023年 | 1314篇 |
2022年 | 2820篇 |
2021年 | 3891篇 |
2020年 | 2835篇 |
2019年 | 2112篇 |
2018年 | 2329篇 |
2017年 | 2638篇 |
2016年 | 2356篇 |
2015年 | 3642篇 |
2014年 | 4357篇 |
2013年 | 5091篇 |
2012年 | 6318篇 |
2011年 | 6465篇 |
2010年 | 5892篇 |
2009年 | 5621篇 |
2008年 | 5575篇 |
2007年 | 5055篇 |
2006年 | 4631篇 |
2005年 | 3792篇 |
2004年 | 2540篇 |
2003年 | 1708篇 |
2002年 | 1537篇 |
2001年 | 1395篇 |
2000年 | 1213篇 |
1999年 | 886篇 |
1998年 | 504篇 |
1997年 | 444篇 |
1996年 | 414篇 |
1995年 | 357篇 |
1994年 | 245篇 |
1993年 | 200篇 |
1992年 | 178篇 |
1991年 | 107篇 |
1990年 | 93篇 |
1989年 | 59篇 |
1988年 | 55篇 |
1987年 | 37篇 |
1986年 | 32篇 |
1985年 | 13篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1959年 | 12篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
采用低温水等离子体技术,在三通道聚氯乙烯(PVC)膜表面接枝了甲基丙烯氧基苄基二甲基氯化铵(DMAE)单体,增强了膜亲水和抗菌性能。通过红外分析,表明DMAE成功接枝到了PVC膜上,水通量提高两倍,PVC-ir-H2O膜(通过水等离子体处理的膜)对牛血清蛋白(BSA)的吸附能力下降67%,对BSA溶液的通量从7.7提高至40 kg?m-2?h-1,并且对BSA的截留能力不变。通过静态及动态抗菌实验,接枝后的PVC膜(PVC-g-PMAE膜)抗菌率达到100%,膜组件运行中的抗菌率也达到82%以上。在保证细菌截留率100%的同时,其渗透通量提高三倍。该膜表面修饰工程技术能实现膜表面的均一化改性,且绿色环保、操作简便、成本低,改性膜在饮用水处理领域,尤其是家用净水器中展现了很好的应用前景。 相似文献
42.
中央美院青岛创业中心项目为角部重叠的回字形山地建筑,采用了框架-剪力墙结构体系.主体建筑结构总高度为54m,坐落在三个台地上,每两个相邻台地高差10m左右.掉层处采用"掉层脱开式且有拉梁"的方式进行结构布置.结合山地建筑结构的基本概念和受力特点,介绍了本项目的结构处理方式和设计难点,采用PKPM,MIDAS Building,SAUSAGE软件对结构进行了弹性反应谱法分析、弹性时程分析、动力弹塑性时程分析和抗震性能设计,同时针对各种不利因素采取了相应的加强措施,确保了结构安全. 相似文献
43.
In this research, the three‐dimensional structural and colorimetric modeling of three‐dimensional woven fabrics was conducted for accurate color predictions. One‐hundred forty single‐ and double‐layered woven samples in a wide range of colors were produced. With the consideration of their three‐dimensional structural parameters, three‐dimensional color prediction models, K/S‐, R‐, and L*a*b*‐based models, were developed through the optimization of previous two‐dimensional models which have been reported to be the three most accurate models for single‐layered woven structures. The accuracy of the new three‐dimensional models was evaluated by calculating the color differences ΔL*, ΔC*, Δh°, and ΔECMC(2:1) between the measured and the predicted colors of the samples, and then the error values were compared to those of the two‐dimensional models. As a result, there has been an overall improvement in color predictions of all models with a decrease in ΔECMC(2:1) from 10.30 to 5.25 units on average after the three‐dimensional modeling. 相似文献
44.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
45.
46.
受断层影响,巷道过断层期间掘进速度缓慢,影响采掘接替和矿井生产效率。为了更好地促进矿井生产,以23上04轨顺掘进为研究对象,采用FLAC 3D软件模拟巷道过断层时巷道围岩变形量和塑性区范围,并将围岩划分为正常围岩、过渡带和破碎带3部分。根据模拟结果可知,围岩变形量和塑性区范围都在过渡带开始增大,在破碎带达到最大值。巷道采用后退卧底法过断层,并对断层破碎带及时采用锚网索、注浆、U型钢棚进行支护,通过联合支护相互配合,可以共同提高巷道支护强度,增强巷道顶帮抗变形能力。 相似文献
47.
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
48.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
50.
ABSTRACTImproving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%. 相似文献