全文获取类型
收费全文 | 110986篇 |
免费 | 11078篇 |
国内免费 | 7087篇 |
专业分类
电工技术 | 8433篇 |
技术理论 | 3篇 |
综合类 | 9034篇 |
化学工业 | 15882篇 |
金属工艺 | 7186篇 |
机械仪表 | 7776篇 |
建筑科学 | 9125篇 |
矿业工程 | 3559篇 |
能源动力 | 3399篇 |
轻工业 | 7465篇 |
水利工程 | 2736篇 |
石油天然气 | 5436篇 |
武器工业 | 1351篇 |
无线电 | 13390篇 |
一般工业技术 | 11898篇 |
冶金工业 | 4366篇 |
原子能技术 | 1642篇 |
自动化技术 | 16470篇 |
出版年
2024年 | 313篇 |
2023年 | 1492篇 |
2022年 | 2739篇 |
2021年 | 4232篇 |
2020年 | 3204篇 |
2019年 | 2662篇 |
2018年 | 2936篇 |
2017年 | 3375篇 |
2016年 | 3200篇 |
2015年 | 4628篇 |
2014年 | 5951篇 |
2013年 | 6890篇 |
2012年 | 8225篇 |
2011年 | 9044篇 |
2010年 | 8387篇 |
2009年 | 8071篇 |
2008年 | 8160篇 |
2007年 | 7827篇 |
2006年 | 7394篇 |
2005年 | 5957篇 |
2004年 | 4375篇 |
2003年 | 3569篇 |
2002年 | 3467篇 |
2001年 | 2913篇 |
2000年 | 2373篇 |
1999年 | 1821篇 |
1998年 | 1160篇 |
1997年 | 1012篇 |
1996年 | 827篇 |
1995年 | 679篇 |
1994年 | 541篇 |
1993年 | 419篇 |
1992年 | 297篇 |
1991年 | 230篇 |
1990年 | 195篇 |
1989年 | 140篇 |
1988年 | 100篇 |
1987年 | 76篇 |
1986年 | 71篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1959年 | 17篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
71.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
72.
Biyun Fang Chuanfeng Zhang Zeliang Qi Chunyan Li Jun Ni Xiuyun Wang Jianxin Lin Chak-Tong Au Bingyu Lin Lilong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17849
The design of an efficient non-noble metal catalyst is of burgeoning interest for ammonia synthesis. Herein, we report a Mo2C/CeO2 catalyst that is superior in ammonia synthesis activity. In this catalyst, molybdenum carbide coexisted with the ceria overlayers which is from the ceria support as the strong metal–support interaction. There is a high proportion of low-valent Mo species, as well as high concentration of Ce3+ and surface oxygen species. The presence of Mo2C and CeO2 overlayers not only leads to enhancement of hydrogen and nitrogen adsorption, but also facilitates the desorption and exchange of adsorbed species with the gaseous reagents. Compared with the Mo/CeO2 catalyst prepared without carbonization, the Mo2C/CeO2 catalyst is more than sevenfold higher in ammonia synthesis rate. This work not only presents an explicit example of designing Mo-based catalyst that is highly efficient for ammonia synthesis by tuning the adsorption and desorption properties of the reactant gases, but opens a perspective for other elements in ammonia synthesis. 相似文献
73.
以太阳纸业备料车间木片筛选碎料(筛余物)为原料,对其烧碱法半化学制浆的实验室工艺和生产试验进行了研究。结果表明,筛余物采用半化学法制浆可获得较高得率和环压强度的纸浆,且用碱量对纸浆性能有显著影响。相对8%NaOH (相对于绝干原料)化学预处理,采用14%NaOH化学预处理结合两段浆浓22%的高浓磨浆工艺,所制半化学浆抄造浆张的裂断长和环压指数分别达2.89 km和9.76 N·m/g,是前者的1.9倍和1.2倍,而且优于现用国内OCC废纸浆抄造浆张;生产试验得到的浆张性能指标与实验室相吻合,其中紧度和环压强度分别达到GB/T 13023—2008瓦楞芯(原)纸AA级和A级优等品要求。 相似文献
74.
The polyamide 6-polyurethane copolymer (PA6-b-PU-b-PA6) was synthesized through anionic suspension polymerization and then mixed with polyamide 6/thermoplastic polyurethane (PA6/TPU) and polyamide 6, 6/thermoplastic polyurethane (PA66/TPU) blends using as the compatibilizer. The results show that the PA6-b-PU-b-PA6 copolymers powders several can be obtained through suspension polymerization using dimethicone as disperse medium. The average diameter of PA6-b-PU-b-PA6 copolymer powders decreased with the increasing of PU content. With the addition of PA6-b-PU-b-PA6, the TPU phase dispersed more uniformly in PA6 or PA66 matrix, and the size of TPU dispersed phase decreased obviously. The PA6-b-PU-b-PA6 copolymer with higher PU content shows better compatibilizing effect. Addition of PA6-b-PU-b-PA6 can improve both strength and toughness of the PA/TPU blends. When the amount of PA6-PU25% copolymer was 5 phr, the tensile strength and notched impact strength of PA6/TPU/PA6-PU25% blends increased 29 and 159.4%, respectively, compared to the PA6/TPU blend without compatibilizer. 相似文献
75.
76.
77.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献
78.
Dr. Yahu A. Liu Dr. Qihui Jin Qiang Ding Dr. Xueshi Hao Tingting Mo Shanshan Yan Dr. Yefen Zou Dr. Zhihong Huang Xiaoyue Zhang Wenqi Gao Dr. Tom Y.-H. Wu Chun Li Dr. Badry Bursalaya Dr. Michael Di Donato Dr. You-Qing Zhang Lisa Deaton Dr. Weijun Shen Dr. Brandon Taylor Anwesh Kamireddy Dr. George Harb Dr. Jing Li Dr. Yong Jia Dr. Andrew M. Schumacher Dr. Bryan Laffitte Dr. Richard Glynne Dr. Shifeng Pan Dr. Peter McNamara Dr. Valentina Molteni Dr. Jon Loren 《ChemMedChem》2020,15(16):1562-1570
Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation. 相似文献
80.
Jialin Sun Jun Zhao Xiuying Ni Feng Gong Zuoli Li 《Journal of the European Ceramic Society》2018,38(9):3096-3103
This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al2O3 nanostructured composite materials doped with Cr3C2/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr3C2/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al2O3 composites. Al2O3 crack deflection, transgranular Al2O3, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties. 相似文献