全文获取类型
收费全文 | 126678篇 |
免费 | 11091篇 |
国内免费 | 8406篇 |
专业分类
电工技术 | 4731篇 |
技术理论 | 3篇 |
综合类 | 7574篇 |
化学工业 | 41806篇 |
金属工艺 | 10834篇 |
机械仪表 | 3513篇 |
建筑科学 | 2986篇 |
矿业工程 | 1993篇 |
能源动力 | 4896篇 |
轻工业 | 10439篇 |
水利工程 | 1146篇 |
石油天然气 | 5977篇 |
武器工业 | 764篇 |
无线电 | 11990篇 |
一般工业技术 | 17018篇 |
冶金工业 | 5190篇 |
原子能技术 | 1723篇 |
自动化技术 | 13592篇 |
出版年
2024年 | 325篇 |
2023年 | 2078篇 |
2022年 | 4229篇 |
2021年 | 5657篇 |
2020年 | 3672篇 |
2019年 | 3482篇 |
2018年 | 3154篇 |
2017年 | 3772篇 |
2016年 | 4324篇 |
2015年 | 4351篇 |
2014年 | 6131篇 |
2013年 | 7128篇 |
2012年 | 8164篇 |
2011年 | 10287篇 |
2010年 | 7811篇 |
2009年 | 9017篇 |
2008年 | 7811篇 |
2007年 | 8834篇 |
2006年 | 8051篇 |
2005年 | 6378篇 |
2004年 | 5358篇 |
2003年 | 4556篇 |
2002年 | 3718篇 |
2001年 | 2943篇 |
2000年 | 2622篇 |
1999年 | 2120篇 |
1998年 | 1674篇 |
1997年 | 1346篇 |
1996年 | 1274篇 |
1995年 | 1123篇 |
1994年 | 1027篇 |
1993年 | 746篇 |
1992年 | 583篇 |
1991年 | 483篇 |
1990年 | 410篇 |
1989年 | 309篇 |
1988年 | 213篇 |
1987年 | 148篇 |
1986年 | 157篇 |
1985年 | 112篇 |
1984年 | 101篇 |
1983年 | 61篇 |
1982年 | 82篇 |
1981年 | 76篇 |
1980年 | 65篇 |
1979年 | 58篇 |
1978年 | 26篇 |
1977年 | 24篇 |
1975年 | 23篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
41.
To overcome the drawbacks of solid microporous materials for CO2 capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO2 through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO2 uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder. 相似文献
42.
43.
44.
中国石化海南炼油化工有限公司0.2 Mt/a C5/C6烷烃异构化装置以连续重整装置的拔头油为原料,使用NNI-1催化剂,采用一次通过流程,不设脱异戊烷塔和稳定塔,经设在连续重整装置内的脱丁烷塔稳定处理后作为汽油调合组分。该装置于2006年9月开工投产,截至2015年3月已连续运行3个周期。长周期运行分析结果表明:前两个周期中NNI-1催化剂具有较高的异构化活性及选择性,C5异构化率为60%左右,C6异构化率为80%左右,C6选择性为15%左右,产品辛烷值基本达到技术指标要求(RON≥78);而在第三周期运行中,催化剂积炭增加等原因导致其异构化活性及选择性降低,异构化产品辛烷值提升能力呈现逐步衰减的趋势,提高反应苛刻度已不能弥补催化剂活性下降造成的产品辛烷值降低。为保证装置长周期运行,建议择机停工对催化剂进行再生,或是直接换用与装置原料性质匹配的异构化催化剂。 相似文献
45.
Mohammad Afshari Amir-Reza Rouhani Isfahani Saeed Hasani Fatemeh Davar Khadijeh Jahanbani Ardakani 《International Journal of Applied Ceramic Technology》2019,16(4):1612-1621
In the present study, spinel structure CoFe2O4 nanoparticles were successfully synthesized by the sol-gel auto-combustion technique. The effect of apple cider vinegar (ACV) addition as an organic biocompatible agent on the size, morphology, and magnetic properties of CoFe2O4 nanoparticles was investigated in detail. The phase evolution, particle size, and lattice parameter changes of the synthesized phase have been estimated by using Rietveld structure refinement analysis of X-ray powder diffraction data. Also, Fourier transform infrared spectra (FT-IR) of the samples verified the presence of two expected bands correspond to tetrahedral and octahedral metal-oxygen complexes within the spinel structure. Furthermore, microstructural observations revealed that ultrafine particles have a semi-spherical morphology. It was shown that the particles size decreased from ~45 to ~17 nm with an increase in the amount of ACV. Magnetic properties were carried out by vibrating sample magnetometer (VSM) at room temperature. Both the saturation magnetization (Ms) and coercivity (Hc) were found to be significantly dependent on the crystallite size and the amount of ACV. 相似文献
46.
47.
48.
49.
Wojciech Jó?wicki Anna A. Bro?yna Jerzy Siekiera Andrzej T. Slominski 《International journal of molecular sciences》2015,16(2):3783-3803
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape. 相似文献
50.