全文获取类型
收费全文 | 70281篇 |
免费 | 3585篇 |
国内免费 | 1558篇 |
专业分类
电工技术 | 2271篇 |
综合类 | 2602篇 |
化学工业 | 9455篇 |
金属工艺 | 2002篇 |
机械仪表 | 2554篇 |
建筑科学 | 2711篇 |
矿业工程 | 1115篇 |
能源动力 | 1476篇 |
轻工业 | 4142篇 |
水利工程 | 1131篇 |
石油天然气 | 1378篇 |
武器工业 | 175篇 |
无线电 | 5377篇 |
一般工业技术 | 6649篇 |
冶金工业 | 22628篇 |
原子能技术 | 490篇 |
自动化技术 | 9268篇 |
出版年
2024年 | 140篇 |
2023年 | 573篇 |
2022年 | 835篇 |
2021年 | 1103篇 |
2020年 | 715篇 |
2019年 | 723篇 |
2018年 | 1175篇 |
2017年 | 1462篇 |
2016年 | 1819篇 |
2015年 | 1870篇 |
2014年 | 1834篇 |
2013年 | 2118篇 |
2012年 | 3926篇 |
2011年 | 4371篇 |
2010年 | 2414篇 |
2009年 | 2360篇 |
2008年 | 2256篇 |
2007年 | 2182篇 |
2006年 | 2113篇 |
2005年 | 4661篇 |
2004年 | 3601篇 |
2003年 | 3112篇 |
2002年 | 2131篇 |
2001年 | 1821篇 |
2000年 | 985篇 |
1999年 | 1307篇 |
1998年 | 6615篇 |
1997年 | 4208篇 |
1996年 | 2866篇 |
1995年 | 1714篇 |
1994年 | 1278篇 |
1993年 | 1261篇 |
1992年 | 375篇 |
1991年 | 396篇 |
1990年 | 378篇 |
1989年 | 337篇 |
1988年 | 331篇 |
1987年 | 239篇 |
1986年 | 226篇 |
1985年 | 183篇 |
1984年 | 84篇 |
1983年 | 90篇 |
1982年 | 151篇 |
1981年 | 189篇 |
1980年 | 203篇 |
1979年 | 66篇 |
1978年 | 100篇 |
1977年 | 616篇 |
1976年 | 1325篇 |
1975年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Tongling Xia Yue Qi Xilei Dai Jinyu Liu Can Xiao Ruoyu You Dayi Lai Junjie Liu Chun Chen 《Indoor air》2021,31(6):2020-2032
To evaluate the separate impacts on human health and establish effective control strategies, it is crucial to estimate the contribution of outdoor infiltration and indoor emission to indoor PM2.5 in buildings. This study used an algorithm to automatically estimate the long-term time-resolved indoor PM2.5 of outdoor and indoor origin in real apartments with natural ventilation. The inputs for the algorithm were only the time-resolved indoor/outdoor PM2.5 concentrations and occupants’ window actions, which were easily obtained from the low-cost sensors. This study first applied the algorithm in an apartment in Tianjin, China. The indoor/outdoor contribution to the gross indoor exposure and time-resolved infiltration factor were automatically estimated using the algorithm. The influence of outdoor PM2.5 data source and algorithm parameters on the estimated results was analyzed. The algorithm was then applied in four other apartments located in Chongqing, Shenyang, Xi'an, and Urumqi to further demonstrate its feasibility. The results provided indirect evidence, such as the plausible explanations for seasonal and spatial variation, to partially support the success of the algorithm used in real apartments. Through the analysis, this study also identified several further development directions to facilitate the practical applications of the algorithm, such as robust long-term outdoor PM2.5 monitoring using low-cost light-scattering sensors. 相似文献
3.
Ava Kwong Cecilia Y. S. Ho Vivian Y. Shin Chun Hang Au Tsun Leung Chan Edmond S. K. Ma 《International journal of molecular sciences》2021,22(2)
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers. 相似文献
4.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation. 相似文献
5.
6.
ABSTRACT In this study, effect of calcium and gypsum on scheelite and fluorite was investigated using sodium oleate as collector. Micro-flotation and contact angle results showed that the adsorption of calcium could inhibit the hydrophobicity of scheelite and fluorite. Moreover, sulfate could enhance the inhibition. FT-IR results showed that calcium could be priori precipitated into calcium oleate and adsorb on mineral surface. The adsorption of calcium could increase the scheelite potential to IEP, while it showed limited effect on fluorite potential. However, the interaction of calcium on scheelite and fluorite in gypsum solution was more complex than that in calcium solution. 相似文献
7.
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
8.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
9.
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