全文获取类型
收费全文 | 285810篇 |
免费 | 9427篇 |
国内免费 | 4052篇 |
专业分类
电工技术 | 8971篇 |
技术理论 | 5篇 |
综合类 | 5818篇 |
化学工业 | 42324篇 |
金属工艺 | 12828篇 |
机械仪表 | 10910篇 |
建筑科学 | 11877篇 |
矿业工程 | 3325篇 |
能源动力 | 7004篇 |
轻工业 | 19721篇 |
水利工程 | 3258篇 |
石油天然气 | 8088篇 |
武器工业 | 690篇 |
无线电 | 36503篇 |
一般工业技术 | 47733篇 |
冶金工业 | 49787篇 |
原子能技术 | 4615篇 |
自动化技术 | 25832篇 |
出版年
2023年 | 1781篇 |
2022年 | 3141篇 |
2021年 | 4559篇 |
2020年 | 3539篇 |
2019年 | 3446篇 |
2018年 | 4640篇 |
2017年 | 4945篇 |
2016年 | 4606篇 |
2015年 | 4738篇 |
2014年 | 6718篇 |
2013年 | 12967篇 |
2012年 | 9959篇 |
2011年 | 11997篇 |
2010年 | 9926篇 |
2009年 | 10693篇 |
2008年 | 10855篇 |
2007年 | 10742篇 |
2006年 | 10485篇 |
2005年 | 9611篇 |
2004年 | 8112篇 |
2003年 | 7557篇 |
2002年 | 7164篇 |
2001年 | 7302篇 |
2000年 | 7189篇 |
1999年 | 8090篇 |
1998年 | 17754篇 |
1997年 | 12066篇 |
1996年 | 9713篇 |
1995年 | 7243篇 |
1994年 | 6206篇 |
1993年 | 5868篇 |
1992年 | 4078篇 |
1991年 | 3806篇 |
1990年 | 3615篇 |
1989年 | 3367篇 |
1988年 | 3051篇 |
1987年 | 2418篇 |
1986年 | 2423篇 |
1985年 | 2693篇 |
1984年 | 2368篇 |
1983年 | 2099篇 |
1982年 | 1941篇 |
1981年 | 2077篇 |
1980年 | 1813篇 |
1979年 | 1665篇 |
1978年 | 1658篇 |
1977年 | 2021篇 |
1976年 | 2702篇 |
1975年 | 1422篇 |
1974年 | 1369篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
41.
Puneet Parmar Nicolas Lopez-Villalobos John T. Tobin Eoin Murphy Frank Buckley Shane V. Crowley Alan L. Kelly Laurence Shalloo 《International Journal of Food Science & Technology》2021,56(5):2415-2422
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally. 相似文献
42.
Polymer Bulletin - Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic... 相似文献
43.
44.
45.
46.
47.
48.
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
49.
50.
Qingna Gong Songtao Cao Yu Zhou Ruixin Wang Weizhou Jiao 《International Journal of Hydrogen Energy》2021,46(41):21442-21453
Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g?1 h?1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles. 相似文献