全文获取类型
收费全文 | 6582篇 |
免费 | 527篇 |
国内免费 | 258篇 |
专业分类
电工技术 | 183篇 |
综合类 | 462篇 |
化学工业 | 4015篇 |
金属工艺 | 297篇 |
机械仪表 | 113篇 |
建筑科学 | 189篇 |
矿业工程 | 178篇 |
能源动力 | 146篇 |
轻工业 | 568篇 |
水利工程 | 31篇 |
石油天然气 | 118篇 |
武器工业 | 2篇 |
无线电 | 118篇 |
一般工业技术 | 675篇 |
冶金工业 | 181篇 |
原子能技术 | 58篇 |
自动化技术 | 33篇 |
出版年
2024年 | 15篇 |
2023年 | 93篇 |
2022年 | 158篇 |
2021年 | 235篇 |
2020年 | 167篇 |
2019年 | 151篇 |
2018年 | 144篇 |
2017年 | 288篇 |
2016年 | 268篇 |
2015年 | 235篇 |
2014年 | 284篇 |
2013年 | 358篇 |
2012年 | 478篇 |
2011年 | 509篇 |
2010年 | 363篇 |
2009年 | 333篇 |
2008年 | 290篇 |
2007年 | 410篇 |
2006年 | 326篇 |
2005年 | 297篇 |
2004年 | 287篇 |
2003年 | 227篇 |
2002年 | 224篇 |
2001年 | 183篇 |
2000年 | 185篇 |
1999年 | 172篇 |
1998年 | 102篇 |
1997年 | 87篇 |
1996年 | 70篇 |
1995年 | 84篇 |
1994年 | 62篇 |
1993年 | 47篇 |
1992年 | 54篇 |
1991年 | 39篇 |
1990年 | 32篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7367条查询结果,搜索用时 343 毫秒
991.
Yunjie Huang Erik Christensen Qin Shuai Qingfeng Li 《International Journal of Hydrogen Energy》2017,42(10):7235-7240
Proton conducting electrolyte materials operational in the intermediate temperature range of 200–400 °C are of special interest for applications in fuel cells and water electrolysers. Bismuth phosphates in forms of polycrystalline powders and amorphous glasses are synthesized and investigated by scanning electron microscopy, X-ray diffraction, FT-IR, thermogravimetric analysis and AC impedance. Under dry atmosphere the pure crystalline and amorphous phosphates exhibit an intrinsic conductivity of up to 10?5 S cm?1 at 250 °C. In the presence of atmospheric humidity the conductivity of both types of phosphates is significantly enhanced, reaching about 10?2 S cm?1 at a water vapor partial pressure above 0.5 atm. During a period of more than 100 h with four humidity cycles from zero to 0.58 atm of the water vapor partial pressure, the phosphates show good stability, suggesting the potential as an intermediate temperature electrolyte. 相似文献
992.
993.
Abd El‐Aziz A Said Kamal MS Khalil 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(3):196-204
Different ratios of vanadium pentoxide supported on aluminum phosphate (1–30 mol%) have been prepared by an impregnation method. The original and calcined samples were characterized by TG, DTG, DSC, X‐ray diffraction, IR spectra, N2 adsorption and electrical conductivity measurements. The catalytic decomposition of ethanol has been carried out at 210 °C in a flow system at 1 atm using air as a carrier gas. The results indicate that the catalysts calcined at 400 °C were active and selective towards ethene formation whereas the samples calcined at 600 °C showed a drastic reduction in both activity and selectivity. © 2000 Society of Chemical Industry 相似文献
994.
Mahmoud Z. Sitohy Said S. El‐Saadany Salah M. Labib Mohamed F. Ramadan 《Starch - St?rke》2000,52(4):101-105
Different types of starch were phosphorylated to different degrees of substitution using monosodium and disodium hydrogen orthophosphate at 160 °C under vacuum. Generally, phosphation enhanced the physicochemical properties of the modified starches compared to their native counterparts. Solubility and swelling power greatly increase when phosphorylation was carried out to a low degree of substitution, while the solubility and swelling power decreased gradually by increasing the degree of substitution. However, the values of the monoesters were still higher than those of the corresponding native polysaccharides. Viscosities of different starch types except corn amylose showed the highest values at the lowest degree of substitution, when the degree of phosphation increased the viscosity values decreased. Native potato starch formed a clear paste (96% transmittance) due to the presence of phosphate groups while the paste clarity of potato starch decreased gradually by increasing the degree of phosphation. Generally, phosphorylation increased the light transmittance of the other starches investigated at the lowest degree of substitution but the clarity decreased by increasing the degree of substitution. 相似文献
995.
A novel aqueous antiwear additive, a ternary complex of zinc with dioxyethylenated octylphenol phosphate and triethanolamine (TXOZ + TEA), has been synthesised. Its tribological behaviour in water was evaluated using a four‐ball tester. The results indicate that the complex in water exhibits higher load‐carrying capacity than mineral oil plus ZDTP, and excellent antiwear behaviour. The elemental composition of its rubbed surface was investigated with Auger electron spectroscopy (AES), and the results of this analysis are presented in the paper. The action mechanism of the additive is also discussed. 相似文献
996.
Xinchen Wang Yoshitomo Honda Jianxin Zhao Hidetoshi Morikuni Aki Nishiura Yoshiya Hashimoto Naoyuki Matsumoto 《International journal of molecular sciences》2021,22(22)
Various stresses latently induce cellular senescence that occasionally deteriorates the functioning of surrounding tissues. Nevertheless, little is known about the appearance and function of senescent cells, caused by the implantation of beta-tricalcium phosphate (β-TCP)—used widely in dentistry and orthopedics for treating bone diseases. In this study, two varying sizes of β-TCP granules (<300 μm and 300–500 μm) were implanted, and using histological and immunofluorescent staining, appearances of senescent-like cells in critical-sized bone defects in the calvaria of Sprague Dawley rats were evaluated. Parallelly, bone formation in defects was investigated with or without the oral administration of senolytics (a cocktail of dasatinib and quercetin). A week after the implantation, the number of senescence-associated beta-galactosidase, p21-, p19-, and tartrate-resistant acid phosphatase-positive cells increased and then decreased upon administrating senolytics. This administration of senolytics also attenuated 4-hydroxy-2-nonenal staining, representing reactive oxygen species. Combining senolytic administration with β-TCP implantation significantly enhanced the bone formation in defects as revealed by micro-computed tomography analysis and hematoxylin-eosin staining. This study demonstrates that β-TCP granules latently induce senescent-like cells, and senolytic administration may improve the bone-forming ability of β-TCP by inhibiting senescence-associated mechanisms. 相似文献
997.
Zeqing Zhao Yaxi Sun Qingchen Qiao Li Zhang Xianju Xie Michael D. Weir Abraham Schneider Hockin H. K. Xu Ning Zhang Ke Zhang Yuxing Bai 《International journal of molecular sciences》2021,22(22)
(1) Background: Vascularization remains a critical challenge in bone tissue engineering. The objective of this study was to prevascularize calcium phosphate cement (CPC) scaffold by co-culturing human periodontal ligament stem cells (hPDLSCs) and human umbilical vein endothelial cells (hUVECs) for the first time; (2) Methods: hPDLSCs and/or hUVECs were seeded on CPC scaffolds. Three groups were tested: (i) hUVEC group (hUVECs on CPC); (ii) hPDLSC group (hPDLSCs on CPC); (iii) co-culture group (hPDLSCs + hUVECs on CPC). Osteogenic differentiation, bone mineral synthesis, and microcapillary-like structures were evaluated; (3) Results: Angiogenic gene expressions of co-culture group were 6–9 fold those of monoculture. vWF expression of co-culture group was 3 times lower than hUVEC-monoculture group. Osteogenic expressions of co-culture group were 2–3 folds those of the hPDLSC-monoculture group. ALP activity and bone mineral synthesis of co-culture were much higher than hPDLSC-monoculture group. Co-culture group formed capillary-like structures at 14–21 days. Vessel length and junction numbers increased with time; (4) Conclusions: The hUVECs + hPDLSCs co-culture on CPC scaffold achieved excellent osteogenic and angiogenic capability in vitro for the first time, generating prevascularized networks. The hPDLSCs + hUVECs co-culture had much better osteogenesis and angiogenesis than monoculture. CPC scaffolds prevacularized via hPDLSCs + hUVECs are promising for dental, craniofacial, and orthopedic applications. 相似文献
998.
为提高磷酸铁锂中Fe、Li和P浸出率,同时实现高效去除Cu、Al和F,开发了硫酸熟化-水浸、铁粉置换除铜、化学沉淀-萃取二段除铝工艺。结果表明,在熟化时间2.5 h、熟化温度110 ℃、固液比4.0/1、水浸温度60 ℃及水浸时间2 h的最佳条件下,硫酸熟化-水浸工艺可将浓硫酸的使用量降至理论值的0.75倍,此时铁浸出率达95%以上,氟脱除率达74.4%; 铁粉置换除铜过程中,控制初始pH=1.2,铁粉加入量为理论值的1.2倍时,浸出液中残留的Cu2+浓度可降至4.9 mg/L以下; 采用化学沉淀-P204萃取二段除铝工艺,可将浸出液中Al3+浓度降至10 mg/L以下。 相似文献
999.
1000.
传统方法制备的异相离子交换膜,在强酸强氧化性溶液体系中使用存在树脂粉脱落和膜性能严重下降的现象,针对这一问题使用流涎法制备出了以聚偏氟乙烯为高分子膜骨架,以聚氯乙烯树脂粉为主要荷电基团,以磷钨酸和磷酸锆颗粒为掺杂荷电基团的聚合物基杂化阳离子交换膜。研究了聚合物基杂化阳离子交换膜的基本性能,测试了膜在强酸强氧化性溶液体系中的电解稳定性,利用扫描电子显微镜(SEM)对膜的表面和截面微观形貌进行了表征。结果表明,相比于传统方法制备的异相阳离子交换膜,流涎法制备的聚合物基杂化阳离子交换膜,膜的选择透过性能和导电性能均有所提高,在强酸强氧化性溶液体系中的电解稳定性也得到了很大的改善,基本上不存在树脂粉脱落和膜性能严重下降的问题。 相似文献