全文获取类型
收费全文 | 112720篇 |
免费 | 6482篇 |
国内免费 | 2995篇 |
专业分类
电工技术 | 3991篇 |
技术理论 | 10篇 |
综合类 | 4733篇 |
化学工业 | 16844篇 |
金属工艺 | 4376篇 |
机械仪表 | 5210篇 |
建筑科学 | 6805篇 |
矿业工程 | 2402篇 |
能源动力 | 2485篇 |
轻工业 | 6502篇 |
水利工程 | 1707篇 |
石油天然气 | 4423篇 |
武器工业 | 544篇 |
无线电 | 10100篇 |
一般工业技术 | 12349篇 |
冶金工业 | 24867篇 |
原子能技术 | 979篇 |
自动化技术 | 13870篇 |
出版年
2024年 | 249篇 |
2023年 | 1324篇 |
2022年 | 1962篇 |
2021年 | 2728篇 |
2020年 | 2068篇 |
2019年 | 1853篇 |
2018年 | 2421篇 |
2017年 | 2918篇 |
2016年 | 3067篇 |
2015年 | 3495篇 |
2014年 | 3713篇 |
2013年 | 4356篇 |
2012年 | 6491篇 |
2011年 | 7028篇 |
2010年 | 4650篇 |
2009年 | 4498篇 |
2008年 | 4274篇 |
2007年 | 4275篇 |
2006年 | 4406篇 |
2005年 | 6636篇 |
2004年 | 4835篇 |
2003年 | 4021篇 |
2002年 | 2762篇 |
2001年 | 2481篇 |
2000年 | 2028篇 |
1999年 | 2624篇 |
1998年 | 7940篇 |
1997年 | 5271篇 |
1996年 | 3901篇 |
1995年 | 2520篇 |
1994年 | 2086篇 |
1993年 | 1803篇 |
1992年 | 784篇 |
1991年 | 733篇 |
1990年 | 624篇 |
1989年 | 531篇 |
1988年 | 520篇 |
1987年 | 354篇 |
1986年 | 294篇 |
1985年 | 236篇 |
1984年 | 101篇 |
1983年 | 110篇 |
1982年 | 167篇 |
1981年 | 196篇 |
1980年 | 205篇 |
1979年 | 64篇 |
1978年 | 98篇 |
1977年 | 608篇 |
1976年 | 1320篇 |
1975年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
22.
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
23.
24.
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from... 相似文献
25.
26.
Klaus Reinhardt Hans Georg Breunig Aisada Uchugonova Karsten K?nig 《Journal of the Royal Society Interface》2015,12(110)
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype. 相似文献
27.
本研究针对水泥窑余热发电系统的工作条件,根据耐磨材料的损毁机理,采用高铝矾土、煅烧氧化铝粉、黏土、硅微粉等为原料,以磷酸二氢铝为结合剂,以铝酸钙水泥为促硬剂,通过添加掩蔽剂和优化配料工艺,制备了水泥窑余热发电系统用耐磨材料,并对不同处理温度对耐磨材料的性能影响进行了分析。结果表明增强骨料与基质的结合能力有利于耐磨性的提高,磷酸及磷酸盐与氧化铝之间会随着温度的升高生成不同的磷酸铝相,都能够起到结合作用,比采用水泥结合更有利于提高材料在不同温度下的强度和耐磨性。使用结果表明,制备的耐磨材料施工性能优良,凝结硬化时间适当,强度高,抗冲刷性能好,在水泥窑余热发电系统中取得了良好的使用效果。 相似文献
28.
29.
30.