全文获取类型
收费全文 | 4773704篇 |
免费 | 320315篇 |
国内免费 | 180368篇 |
专业分类
电工技术 | 255867篇 |
技术理论 | 125篇 |
综合类 | 255757篇 |
化学工业 | 702009篇 |
金属工艺 | 228527篇 |
机械仪表 | 254451篇 |
建筑科学 | 260584篇 |
矿业工程 | 108873篇 |
能源动力 | 134135篇 |
轻工业 | 397759篇 |
水利工程 | 97767篇 |
石油天然气 | 141789篇 |
武器工业 | 35163篇 |
无线电 | 513056篇 |
一般工业技术 | 587805篇 |
冶金工业 | 567812篇 |
原子能技术 | 62900篇 |
自动化技术 | 670008篇 |
出版年
2024年 | 14615篇 |
2023年 | 45625篇 |
2022年 | 106954篇 |
2021年 | 145615篇 |
2020年 | 106513篇 |
2019年 | 86661篇 |
2018年 | 103708篇 |
2017年 | 115665篇 |
2016年 | 104762篇 |
2015年 | 123191篇 |
2014年 | 167443篇 |
2013年 | 269764篇 |
2012年 | 277691篇 |
2011年 | 315776篇 |
2010年 | 282341篇 |
2009年 | 282895篇 |
2008年 | 289404篇 |
2007年 | 280746篇 |
2006年 | 255020篇 |
2005年 | 212554篇 |
2004年 | 150260篇 |
2003年 | 115052篇 |
2002年 | 108128篇 |
2001年 | 99202篇 |
2000年 | 97365篇 |
1999年 | 80721篇 |
1998年 | 142496篇 |
1997年 | 100474篇 |
1996年 | 85356篇 |
1995年 | 66923篇 |
1994年 | 58219篇 |
1993年 | 49846篇 |
1992年 | 33198篇 |
1991年 | 30012篇 |
1990年 | 29863篇 |
1989年 | 28898篇 |
1988年 | 26824篇 |
1987年 | 24468篇 |
1986年 | 23784篇 |
1985年 | 25533篇 |
1984年 | 22147篇 |
1983年 | 20347篇 |
1982年 | 19171篇 |
1981年 | 19523篇 |
1980年 | 18760篇 |
1979年 | 16820篇 |
1978年 | 16238篇 |
1977年 | 22921篇 |
1976年 | 33658篇 |
1975年 | 14036篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
161.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
162.
Khadijeh Pourkhanali Gholam Khayati 《Theoretical Foundations of Chemical Engineering》2021,55(6):1169-1177
Theoretical Foundations of Chemical Engineering - The importance of aqueous two-phase systems has been increased recently as a method with greater performance capability in separation and... 相似文献
163.
164.
Catalysis Letters - In the present paper, an efficient Cu-catalyzed regioselective acylation of indoles with phenylglyoxals was developed which is the first example of indolyl diketones synthesis... 相似文献
165.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns. 相似文献
166.
Multimedia Tools and Applications - In geometry-based point cloud compression, the geometry information is typically compressed using octree coding. In octree coding, the size of the blocks in the... 相似文献
167.
Moghadam Seyedeh Hadis Ashofteh Parisa-Sadat Loáiciga Hugo A. 《Water Resources Management》2022,36(9):3181-3205
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in... 相似文献
168.
169.
Pengfei Chen Honggang Chang Tao Peng Yongfan Tang Youquan Liu Chao Xiang 《应用聚合物科学杂志》2021,138(30):50314
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters. 相似文献
170.
Ping-Chi Hsu Jia-Ying Jhong Li-Ping Huang Kuo-Hsin Lee Hsin-Pao Chen Yue-Leon Guo 《International journal of molecular sciences》2021,22(8)
Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system. 相似文献