全文获取类型
收费全文 | 17521篇 |
免费 | 1402篇 |
国内免费 | 668篇 |
专业分类
电工技术 | 895篇 |
综合类 | 1169篇 |
化学工业 | 3110篇 |
金属工艺 | 1047篇 |
机械仪表 | 1098篇 |
建筑科学 | 1384篇 |
矿业工程 | 468篇 |
能源动力 | 408篇 |
轻工业 | 1077篇 |
水利工程 | 301篇 |
石油天然气 | 1160篇 |
武器工业 | 107篇 |
无线电 | 1825篇 |
一般工业技术 | 2229篇 |
冶金工业 | 835篇 |
原子能技术 | 242篇 |
自动化技术 | 2236篇 |
出版年
2024年 | 77篇 |
2023年 | 316篇 |
2022年 | 485篇 |
2021年 | 722篇 |
2020年 | 588篇 |
2019年 | 455篇 |
2018年 | 581篇 |
2017年 | 627篇 |
2016年 | 559篇 |
2015年 | 653篇 |
2014年 | 813篇 |
2013年 | 985篇 |
2012年 | 1132篇 |
2011年 | 1182篇 |
2010年 | 1030篇 |
2009年 | 958篇 |
2008年 | 973篇 |
2007年 | 884篇 |
2006年 | 964篇 |
2005年 | 844篇 |
2004年 | 576篇 |
2003年 | 481篇 |
2002年 | 428篇 |
2001年 | 346篇 |
2000年 | 389篇 |
1999年 | 457篇 |
1998年 | 369篇 |
1997年 | 347篇 |
1996年 | 299篇 |
1995年 | 234篇 |
1994年 | 191篇 |
1993年 | 155篇 |
1992年 | 127篇 |
1991年 | 86篇 |
1990年 | 93篇 |
1989年 | 42篇 |
1988年 | 46篇 |
1987年 | 23篇 |
1986年 | 27篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1959年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献
12.
通过对氨汽提尿素装置高压系统合成操作压力的理论分析,结合实际工况降低高压系统操作压力,使装置的设备运转状况得到有效改善。 相似文献
13.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
14.
In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN. 相似文献
15.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
16.
17.
Dr. Yahu A. Liu Dr. Qihui Jin Qiang Ding Dr. Xueshi Hao Tingting Mo Shanshan Yan Dr. Yefen Zou Dr. Zhihong Huang Xiaoyue Zhang Wenqi Gao Dr. Tom Y.-H. Wu Chun Li Dr. Badry Bursalaya Dr. Michael Di Donato Dr. You-Qing Zhang Lisa Deaton Dr. Weijun Shen Dr. Brandon Taylor Anwesh Kamireddy Dr. George Harb Dr. Jing Li Dr. Yong Jia Dr. Andrew M. Schumacher Dr. Bryan Laffitte Dr. Richard Glynne Dr. Shifeng Pan Dr. Peter McNamara Dr. Valentina Molteni Dr. Jon Loren 《ChemMedChem》2020,15(16):1562-1570
Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation. 相似文献
18.
Maimaitiaili Tayier Yunfeng Zhao Dengle Duan Rongge Zou Yunpu Wang Roger Ruan 《木材化学与工艺学杂志》2020,40(3):190-199
AbstractLignin biochar-catalytic depolymerization using biochar Fe-600, Fe-800, Ni-600, Ni-800 catalysts under microwave-heating (180?°C for 30?min) was explored in an ethanol/formic acid (1:1) media. Non-catalyst depolymerization was also studied and compared with the biochar-catalysts results. Characteristics of the bio-char catalysts were analyze by BET, XRD, and FT-IR. GPC, FT-IR, and MALDI-TOF MS spectrometry were also used to characterize the depolymerization products. The experimental results showed that the SBET, Vt, and Vmec and average pore diameter of the biochars are considerably dependent on the preparation temperature and type of cation (Ni2+ or Fe3+). The maximum yield of bio-oil product was obtained as 85?wt% with the addition of biochar Ni-600 and the total amount of oligomers or monomers with a molecular weight of 164 to 446 reaches 80.4%. 相似文献
19.
Li Lei Limin Li Shasha Wang Gaoyang Zhao Yoshifumi Oshima Yang Ren Lei Zhao Lihua Jin Yao Wang Chengshan Li Pingxiang Zhang 《Journal of the European Ceramic Society》2018,38(14):4694-4700
Highly (100)-oriented Ce1-x(Y0.2Zr0.8)xOδ (CYZO) films were prepared on biaxially textured NiW substrates by a chemical solution deposition approach using metal inorganic salts as starting materials. It has been found that both the preferential orientation and surface roughness of CYZO films decrease gradually with increasing of the doping percentage of Y3+ and Zr4+ ions. The epitaxial growth relationship of (220)CYZO//(200)NiW and [00?l]CYZO//[001]NiW was demonstrated by XRD texture measurement as well as atomic resolution STEM observation. XRD, Raman and XPS spectra results indicate that Y3+ and Zr4+ ions were indeed introduced into CeO2 lattice to substitute Ce4+ ions and form cubic fluorite CYZO solid solution. Moreover, CeO2 buffer layer can be endowed a strong enough capability to prevent element diffusion through co-doping of yttrium and zirconium, provided that an optimal doping ratio of them is adopted. This will provide a new approach to fabricating strong-barrier single buffer layer for coated conductor. 相似文献
20.