全文获取类型
收费全文 | 132149篇 |
免费 | 10618篇 |
国内免费 | 5787篇 |
专业分类
电工技术 | 7684篇 |
技术理论 | 13篇 |
综合类 | 9259篇 |
化学工业 | 22501篇 |
金属工艺 | 7628篇 |
机械仪表 | 8392篇 |
建筑科学 | 10086篇 |
矿业工程 | 3446篇 |
能源动力 | 3667篇 |
轻工业 | 9194篇 |
水利工程 | 2630篇 |
石油天然气 | 6775篇 |
武器工业 | 1003篇 |
无线电 | 15119篇 |
一般工业技术 | 15542篇 |
冶金工业 | 6812篇 |
原子能技术 | 1406篇 |
自动化技术 | 17397篇 |
出版年
2024年 | 477篇 |
2023年 | 1751篇 |
2022年 | 3316篇 |
2021年 | 4491篇 |
2020年 | 3378篇 |
2019年 | 2945篇 |
2018年 | 3281篇 |
2017年 | 3669篇 |
2016年 | 3459篇 |
2015年 | 4673篇 |
2014年 | 6214篇 |
2013年 | 7828篇 |
2012年 | 8613篇 |
2011年 | 9129篇 |
2010年 | 8406篇 |
2009年 | 8164篇 |
2008年 | 8130篇 |
2007年 | 8017篇 |
2006年 | 8024篇 |
2005年 | 6913篇 |
2004年 | 4891篇 |
2003年 | 4036篇 |
2002年 | 3618篇 |
2001年 | 3249篇 |
2000年 | 3290篇 |
1999年 | 3277篇 |
1998年 | 2871篇 |
1997年 | 2309篇 |
1996年 | 2101篇 |
1995年 | 1747篇 |
1994年 | 1492篇 |
1993年 | 1051篇 |
1992年 | 794篇 |
1991年 | 632篇 |
1990年 | 469篇 |
1989年 | 439篇 |
1988年 | 366篇 |
1987年 | 207篇 |
1986年 | 186篇 |
1985年 | 116篇 |
1984年 | 104篇 |
1983年 | 69篇 |
1982年 | 66篇 |
1981年 | 61篇 |
1980年 | 43篇 |
1979年 | 34篇 |
1978年 | 14篇 |
1977年 | 34篇 |
1976年 | 17篇 |
1975年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 27 毫秒
41.
42.
Yao‐Min Hung Neng‐Chyan Huang Jyh‐Seng Wang Shue‐Ren Wann 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(2):344-346
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions. 相似文献
43.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
44.
VASP(Vienna Ab-initio Simulation Package)是基于密度泛函理论的通用材料计算模拟软件。随着高性能计算平台的广泛使用和高通量计算的兴起,VASP计算任务的复杂性和数据量也大幅度提升。为了提高材料理论计算的方便程度,减少大量重复的指令和结果检查的复杂性,本文提供了一个基于Python语言的VASP计算辅助程序VaspCZ,能够大幅提高研究者的科研效率。该程序包含软件部分和API部分,软件部分提供了命令行用户界面,基于基本的Linux命令即可一键完成VASP计算的相关操作,为无编程语言基础的研究人员提供了便利。应用程序接口部分服务于具有Python语言基础的研究者,提供了底层库,使得自定义计算(如高通量计算、编写高级应用等)更为简单快捷。本程序包可以显著提高VASP的计算效率,并已经通过Github开源项目公开,提供了详细的使用文档、使用示例和API接口,有望能为广大材料理论研究者提供便利。 相似文献
45.
46.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
47.
48.
Wai-Ching Liu Huey-Yuan Wang Lung-Chien Chen Shih-Wei Huang Chengtie Wu Ren-Jei Chung 《Ceramics International》2019,45(5):5668-5679
Tricalcium silicate (C3S) and hydroxyapatite (HAp) composites were fabricated through the sol-gel process. The aim of this research is to improve the biocompatibility of C3S through HAp addition and study the potential of using this as coating materials. The composites (HAp/C3S) were characterised by Fourier transform infrared spectrometry, thermal gravity-differential thermal analysis and X-ray diffraction. The working and setting times of cement pastes were tested using Gillmore needle. Mechanical properties were examined by nanoindentation and material testing system. In vitro biocompatibility of the materials were studied by cell attachment and viability of L929 and MG-63 cells. HAp/C3S as a coating material on gelatin film were measured with the surface roughness and imaged by scanning electron microscope. With the addition of HAp, no undesirable free CaO was detected with the synthesis by the sol-gel preparation. The pH values of HAp added groups were between 7.54 and 8.76, which were much lower than pure C3S group (pH?=?11.75). For in vitro studies, the presence of HAp could effectively enhance the cell attachment and viability of both L929 and MG-63 cells grown in the extract or directly on the composites. However, the mechanical properties of the composites were impaired as compared to pure C3S. Lastly, HAp/C3S cement could be evenly coated on gelatin film. HAp is successfully demonstrated to improve C3S biocompatibility with this new composites HAp/C3S. C-75 (75% C3S and 25% HAp), in particular, has good biocompatibility, relatively high compressive strength and can be uniformly coated onto gelatin film. Thus, C-75 is a promising material for further investigation as a coating on other biopolymers. 相似文献
49.
50.