全文获取类型
收费全文 | 193346篇 |
免费 | 2867篇 |
国内免费 | 721篇 |
专业分类
电工技术 | 3517篇 |
综合类 | 110篇 |
化学工业 | 31076篇 |
金属工艺 | 8045篇 |
机械仪表 | 5399篇 |
建筑科学 | 5423篇 |
矿业工程 | 980篇 |
能源动力 | 5168篇 |
轻工业 | 17632篇 |
水利工程 | 1851篇 |
石油天然气 | 3318篇 |
武器工业 | 3篇 |
无线电 | 20831篇 |
一般工业技术 | 35999篇 |
冶金工业 | 36976篇 |
原子能技术 | 4437篇 |
自动化技术 | 16169篇 |
出版年
2021年 | 1506篇 |
2019年 | 1455篇 |
2018年 | 2347篇 |
2017年 | 2316篇 |
2016年 | 2486篇 |
2015年 | 1789篇 |
2014年 | 3076篇 |
2013年 | 8829篇 |
2012年 | 5168篇 |
2011年 | 7185篇 |
2010年 | 5677篇 |
2009年 | 6501篇 |
2008年 | 6675篇 |
2007年 | 6668篇 |
2006年 | 5655篇 |
2005年 | 5362篇 |
2004年 | 5007篇 |
2003年 | 4688篇 |
2002年 | 4577篇 |
2001年 | 4438篇 |
2000年 | 4208篇 |
1999年 | 4335篇 |
1998年 | 10657篇 |
1997年 | 7661篇 |
1996年 | 5934篇 |
1995年 | 4582篇 |
1994年 | 3870篇 |
1993年 | 3843篇 |
1992年 | 2857篇 |
1991年 | 2689篇 |
1990年 | 2640篇 |
1989年 | 2700篇 |
1988年 | 2568篇 |
1987年 | 2323篇 |
1986年 | 2262篇 |
1985年 | 2612篇 |
1984年 | 2417篇 |
1983年 | 2222篇 |
1982年 | 2081篇 |
1981年 | 2136篇 |
1980年 | 1954篇 |
1979年 | 1990篇 |
1978年 | 1937篇 |
1977年 | 2277篇 |
1976年 | 2819篇 |
1975年 | 1729篇 |
1974年 | 1704篇 |
1973年 | 1723篇 |
1972年 | 1453篇 |
1971年 | 1327篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
61.
D. Solís-Cortés E. Navarrete-Astorga J.L. Costa-Krämer J. Salguero-Fernandez R. Schrebler D. Leinen E.A. Dalchiele J.R. Ramos-Barrado F. Martín 《Ceramics International》2019,45(5):5577-5587
C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75?×?103 Ω?1 cm?1) were obtained for GIZO films with In/Zn ratio ≥?1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85–0.90 for the GIZO films. 相似文献
62.
Zhuang CHENG Jianfeng WANG Matthew Richard COOP Guanlin YE 《Frontiers of Structural and Civil Engineering》2020,14(2):357
The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for in situ investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). In situ triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils. 相似文献
63.
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
64.
D. M. Mukhammadiev F. Kh. Ibragimov T. D. Mukhammadiev 《Journal of Machinery Manufacture and Reliability》2020,49(3):256-262
The dynamic characteristics of a saw gin as a subsystem with lumped and distributed parameters are considered in the paper. On the basis of investigation of the machine assembly, graphs are drawn that allow establishing the maximum values of the angle of relative rotation and the angle of rotation of the saw cylinder shaft under torsion. 相似文献
65.
66.
67.
68.
69.
70.