全文获取类型
收费全文 | 525435篇 |
免费 | 7096篇 |
国内免费 | 1470篇 |
专业分类
电工技术 | 9560篇 |
综合类 | 526篇 |
化学工业 | 78679篇 |
金属工艺 | 19964篇 |
机械仪表 | 15194篇 |
建筑科学 | 12667篇 |
矿业工程 | 2270篇 |
能源动力 | 14528篇 |
轻工业 | 47066篇 |
水利工程 | 5220篇 |
石油天然气 | 9334篇 |
武器工业 | 37篇 |
无线电 | 59918篇 |
一般工业技术 | 101774篇 |
冶金工业 | 103503篇 |
原子能技术 | 10558篇 |
自动化技术 | 43203篇 |
出版年
2022年 | 3160篇 |
2021年 | 4900篇 |
2020年 | 3485篇 |
2019年 | 4561篇 |
2018年 | 7814篇 |
2017年 | 7615篇 |
2016年 | 7938篇 |
2015年 | 5566篇 |
2014年 | 9249篇 |
2013年 | 24073篇 |
2012年 | 14631篇 |
2011年 | 20150篇 |
2010年 | 15804篇 |
2009年 | 17703篇 |
2008年 | 18092篇 |
2007年 | 17782篇 |
2006年 | 15507篇 |
2005年 | 14208篇 |
2004年 | 13602篇 |
2003年 | 13397篇 |
2002年 | 12633篇 |
2001年 | 12831篇 |
2000年 | 11867篇 |
1999年 | 12595篇 |
1998年 | 32813篇 |
1997年 | 22898篇 |
1996年 | 17450篇 |
1995年 | 13033篇 |
1994年 | 11284篇 |
1993年 | 10973篇 |
1992年 | 7913篇 |
1991年 | 7417篇 |
1990年 | 7262篇 |
1989年 | 7013篇 |
1988年 | 6470篇 |
1987年 | 5767篇 |
1986年 | 5655篇 |
1985年 | 6265篇 |
1984年 | 5900篇 |
1983年 | 5170篇 |
1982年 | 4900篇 |
1981年 | 4967篇 |
1980年 | 4705篇 |
1979年 | 4609篇 |
1978年 | 4408篇 |
1977年 | 5334篇 |
1976年 | 6971篇 |
1975年 | 3796篇 |
1974年 | 3550篇 |
1973年 | 3665篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The author relates his experiences in a small software development company. These experiences show that project management is challenging and if the project manager is an obstacle, the project is bound to fail. When it does, it can spell disaster for the manager and anyone who accompanies him or her on a software development journey. 相似文献
122.
A. M. Kozodaev O. V. Shvedov V. N. Konev B. Yu. Sharkov V. V. Vasil'ev E. B. Volkov N. V. Lazarev A. M. Raskopin G. G. Shimchuk P. V. Bogdanov A. I. Kiryushin V. V. Petrunin E. I. Azhnin E. I. Tyurin I. I. Titaev Yu. P. Severgin A. Yu. Konstantinov 《Atomic Energy》2003,94(1):56-60
The purpose and current construction status, at the Institute of Theoretical and Experimental Physics, of an experimental electronuclear setup, combining a pulsed proton linear accelerator (36 MeV, 0.5 mA) and a subcritical blanket thermal-power assembly 100 kW, are discussed. The main equipment is already available or is being built in industry. The setup can be used to investigate the dynamics of the interaction of a linac–driver and a subcritical reactor and problems concerning the accelerator–driver and the target–blanket assembly. The proton beams and neutron fluxes will be used for applied purposes. In the future it will be possible to increase substantially the current and energy of the proton beam. 相似文献
123.
Some methods determine the non-indolyl glucosinolates content in rapeseed as their hydrolysates: the isothiocyanates and the
oxazolidinethiones. These methods in their present form underestimate the amount of the glucosinolates content. In this investigation,
a modified method was developed to give a better quantitative estimate, indicating a glucosinolate level five times that obtained
by a typical existing method. 相似文献
124.
Modeling and assimilation of root zone soil moisture using remote sensing observations in Walnut Gulch Watershed during SMEX04 总被引:1,自引:0,他引:1
Soil moisture status in the root zone is an important component of the water cycle at all spatial scales (e.g., point, field, catchment, watershed, and region). In this study, the spatio-temporal evolution of root zone soil moisture of the Walnut Gulch Experimental Watershed (WGEW) in Arizona was investigated during the Soil Moisture Experiment 2004 (SMEX04). Root zone soil moisture was estimated via assimilation of aircraft-based remotely sensed surface soil moisture into a distributed Soil-Water-Atmosphere-Plant (SWAP) model. An ensemble square root filter (EnSRF) based on a Kalman filtering scheme was used for assimilating the aircraft-based soil moisture observations at a spatial resolution of 800 m × 800 m. The SWAP model inputs were derived from the SSURGO soil database, LAI (Leaf Area Index) data from SMEX04 database, and data from meteorological stations/rain gauges at the WGEW. Model predictions are presented in terms of temporal evolution of soil moisture probability density function at various depths across the WGEW. The assimilation of the remotely sensed surface soil moisture observations had limited influence on the profile soil moisture. More specifically, root zone soil moisture depended mostly on the soil type. Modeled soil moisture profile estimates were compared to field measurements made periodically during the experiment at the ground based soil moisture stations in the watershed. Comparisons showed that the ground-based soil moisture observations at various depths were within ± 1 standard deviation of the modeled profile soil moisture. Density plots of root zone soil moisture at various depths in the WGEW exhibited multi-modal variations due to the uneven distribution of precipitation and the heterogeneity of soil types and soil layers across the watershed. 相似文献
125.
I. Revilla & M. L. González-San José 《International Journal of Food Science & Technology》2003,38(1):29-36
Summary The effect of the addition of four commercial pectolytic preparations on the visual characteristics (colour and turbidity) of red wines has been evaluated. The effect of both clarifying and colour extracting enzymes and the effect of different doses used, were evaluated and compared. All the red wines treated enzymatically, independent of the type of enzyme and dose, present chromatic characteristics which can be considered better than those of the control wines. Also, those wines treated with enzymes had greater stability during 2 years storage in bottles, in particular the turbidity was better than untreated wines. 相似文献
126.
127.
128.
A simulation of flow field and tracer homogenization was performed using the commercial CFD software FLUENT 6.1. The aim is to investigate the potential of CFD software to predict concentration distribution of added tracer in cylindrical vessels. The calculated results – dimensionless velocity profiles, power and pumping numbers, dimensionless concentration curves, and mixing times – were compared with experiments in stirred vessels. In Part I, the study was performed for vessels agitated by one or two impellers on a centric shaft. Two different impellers were used – a 6‐bladed 45° pitched blade turbine and a standard Rushton turbine. The standard k‐? turbulence model and multiple reference frames method were used for the simulations. The influence of the grid type was also investigated; three types of grid – a structured, unstructured and a special user‐defined grid – were studied. 相似文献
129.
130.
This paper examines Total Quality Management (TQM) as defined by Dr. W. Edwards Deming including Deming's fourteen points and explains how the United States' Department of Defense (DOD) defines TQM and why TQM is necessary. It also covers how the DOD is planning on implementing TQM and the policy that has been established as guidance in the implementation process. 相似文献