全文获取类型
收费全文 | 4349篇 |
免费 | 44篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 446篇 |
金属工艺 | 31篇 |
机械仪表 | 59篇 |
建筑科学 | 100篇 |
矿业工程 | 5篇 |
能源动力 | 44篇 |
轻工业 | 175篇 |
水利工程 | 18篇 |
石油天然气 | 6篇 |
无线电 | 310篇 |
一般工业技术 | 330篇 |
冶金工业 | 2588篇 |
原子能技术 | 20篇 |
自动化技术 | 227篇 |
出版年
2021年 | 25篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 33篇 |
2017年 | 24篇 |
2016年 | 35篇 |
2015年 | 20篇 |
2014年 | 49篇 |
2013年 | 123篇 |
2012年 | 63篇 |
2011年 | 89篇 |
2010年 | 57篇 |
2009年 | 80篇 |
2008年 | 73篇 |
2007年 | 73篇 |
2006年 | 63篇 |
2005年 | 68篇 |
2004年 | 85篇 |
2003年 | 50篇 |
2002年 | 66篇 |
2001年 | 30篇 |
2000年 | 45篇 |
1999年 | 102篇 |
1998年 | 827篇 |
1997年 | 465篇 |
1996年 | 274篇 |
1995年 | 194篇 |
1994年 | 161篇 |
1993年 | 165篇 |
1992年 | 63篇 |
1991年 | 66篇 |
1990年 | 63篇 |
1989年 | 55篇 |
1988年 | 50篇 |
1987年 | 55篇 |
1986年 | 48篇 |
1985年 | 46篇 |
1984年 | 30篇 |
1983年 | 49篇 |
1982年 | 29篇 |
1981年 | 34篇 |
1980年 | 42篇 |
1979年 | 18篇 |
1978年 | 29篇 |
1977年 | 58篇 |
1976年 | 124篇 |
1975年 | 27篇 |
1974年 | 16篇 |
1973年 | 19篇 |
1972年 | 15篇 |
排序方式: 共有4398条查询结果,搜索用时 15 毫秒
1.
2.
3.
Joshua C. Price Simon J. Levett Valentin Radu David A. Simpson Aina Mogas Barcons Christopher F. Adams Melissa L. Mather 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits. 相似文献
4.
H.P. Kuo P.C. KnightD.J. Parker A.S. BurbidgeM.J. Adams J.P.K. Seville 《Powder Technology》2003,132(1):1-9
The motion of sand particles close to a single moving blade was investigated using Positron Emission Particle Tracking (PEPT) during the period in which the free bed surface profile was evolving to an equilibrium shape. The area affected by the blade was divided into active and inactive regions and these were analysed separately. The characteristic heart-shape of the active region in the plan view was determined. An approximately 10-particle-diameter wide velocity transition zone is found between the two regions. While the tracer particle is in the inactive region moving away from the blade, the time dependence of the axial displacement is well described by a logarithmic relationship. The probability of particle movement towards the centre of the blade was quantified using a “central tendency” index. The calculated central tendency shows maxima at each side of the blade. The separation of the two maxima, which indicates the width of the active region, increases with fill level but is independent of rotational speed. 相似文献
5.
Lead content of rice collected from various areas in the world 总被引:1,自引:0,他引:1
ZW Zhang CS Moon T Watanabe S Shimbo M Ikeda 《Canadian Metallurgical Quarterly》1996,191(1-2):169-175
Rice samples consumed by local populations were collected between 1990 and 1995 in 17 areas in the world, mostly from Asia (10 areas), but also from 7 areas outside of Asia. In total, 1528 samples were obtained (about one half from Japan) and were analyzed for lead (Pb) by electrothermal atomic absorption spectrometry. When the Pb contents in rice samples were classified into 10 areas in Asia, the highest and the lowest geometric means (GMs) were for Indonesia (38 ng/g) and Australia (2 ng/g), respectively. Among 7 regions outside Asia, the GM was highest for Spain (58 ng/g) and the lowest for the USA. (3 ng/g). Moreover, inter-regional differences were significant, when more than 100 samples from one area were divided into 3-9 regions and GMs for regions were compared. There was a marked difference in Pb contents in rice by areas and regions in the world. Nevertheless, comparison by area of the present results with those reported in literature show that there has been no substantial reduction in Pb in rice in the past decade either in Japan or elsewhere in the world. 相似文献
6.
7.
Pre-transplant nephrectomy was done in a 25-year-old man for calculous pyelonephritis using a retroperitoneal laparoscopic approach with a newly devised ligature applicator-dissector- kidney retractor. 相似文献
8.
E Bazopoulou-Kyrkanidou P Neou CS Bartsocas S Kyrkanides I Fanourakis 《Canadian Metallurgical Quarterly》1995,6(3):227-232
PURPOSE: To select ideal radiologic projections for mapping and ablation of tachycardias of right ventricular outflow tract (RVOT). METHODS: Ten hearts from human corpses were studied utilizing radiopaque material to identify the pulmonary valve and three distinct sites on this valve: septal anterior (A), septal posterior (P) and free-wall (L). Next, the hearts were filmed in the frontal plane and in oblique projections with 15 degrees increments to the right and to the left. The projections in which the sites were lateralized on the valve, eased radiologic interpretation and were considered ideal for mapping and ablation. Depending on the proximity of the sites to the lateral extremes of the pulmonary valve, the projections were considered ideal ( ), intermediary (++) and inadequate (+). RESULTS: Projections [table: see text] CONCLUSION: The A site of RVOT was best indicated in the 60 and 45 degrees left anterior oblique projections; the 0 degree postero anterior projection was best for mapping the P site; the L region was best explored in the 60 degrees right anterior oblique projection. 相似文献
9.
10.
The occurrence of fungi was investigated in the gut of 200 common garden lizards (Agama agama). The most important pathogenic fungus isolated was Basidiobolus haptosporus, an aetiological agent of subcutaneous zygomycosis. It was recovered from the intestinal contents of 112 (56%) lizards. Other important fungi isolated included Aspergillus spp. in 24 (12%) lizards, Candida spp. in 12 (6%), Penicillium spp. in 12 (6%) and Fusarium spp. in 12 (6%). Mucor spp. were isolated from eight (4%) male lizards only. Agamid lizards are plentiful in rural and urban areas of Nigeria. As they live in close vicinity to man, they are likely to play an important role in the spread of disease that may be caused by these fungi and its transmission to man. None of the animals investigated that yielded fungal cultures revealed any external fungal infection. 相似文献