全文获取类型
收费全文 | 10971篇 |
免费 | 1011篇 |
国内免费 | 400篇 |
专业分类
电工技术 | 193篇 |
技术理论 | 1篇 |
综合类 | 702篇 |
化学工业 | 2987篇 |
金属工艺 | 441篇 |
机械仪表 | 318篇 |
建筑科学 | 977篇 |
矿业工程 | 306篇 |
能源动力 | 399篇 |
轻工业 | 1996篇 |
水利工程 | 430篇 |
石油天然气 | 710篇 |
武器工业 | 50篇 |
无线电 | 434篇 |
一般工业技术 | 1016篇 |
冶金工业 | 669篇 |
原子能技术 | 205篇 |
自动化技术 | 548篇 |
出版年
2024年 | 39篇 |
2023年 | 142篇 |
2022年 | 337篇 |
2021年 | 365篇 |
2020年 | 428篇 |
2019年 | 329篇 |
2018年 | 303篇 |
2017年 | 356篇 |
2016年 | 402篇 |
2015年 | 413篇 |
2014年 | 563篇 |
2013年 | 723篇 |
2012年 | 749篇 |
2011年 | 828篇 |
2010年 | 619篇 |
2009年 | 680篇 |
2008年 | 554篇 |
2007年 | 683篇 |
2006年 | 601篇 |
2005年 | 426篇 |
2004年 | 381篇 |
2003年 | 340篇 |
2002年 | 272篇 |
2001年 | 227篇 |
2000年 | 203篇 |
1999年 | 205篇 |
1998年 | 159篇 |
1997年 | 127篇 |
1996年 | 123篇 |
1995年 | 121篇 |
1994年 | 95篇 |
1993年 | 72篇 |
1992年 | 69篇 |
1991年 | 71篇 |
1990年 | 56篇 |
1989年 | 49篇 |
1988年 | 49篇 |
1987年 | 36篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 35篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1962年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
Claes-Gran Johansson 《Journal of the Institute of Brewing》1996,102(4):249-250
A combustion method, relying on the Dumas principle, for the determination of total nitrogen in barley and malt, has been collaboratively tested by the Analysis Committee of the European Brewery Convention. Repeatability, r95, and reproducibility, R95, values were 0.063 and 0.116% of dry matter, respectively, for samples with nitrogen contents in the range 1.23 to 1.86% N of dry matter. There was no significant difference between these values for barley and malt. The Analysis Committee approved the adoption of the combustion method for inclusion in Analytica EBC as an alternative method. 相似文献
14.
雁翎油田注氮气提高采收率工艺技术 总被引:10,自引:0,他引:10
在现有的提高采收率方法中,注气驱是应用较广、效果较好的方法,特别是注氮气驱由于其气源广泛、价廉经济、无腐蚀性,以及要求的油藏地质结构特征和原油的物理性质等因素的变化范围广泛等特产,这种提高采收率的方法应用的最为普及,代表了目前提高采收率的发展方向。结合雁翎油田实例,简要介绍了注氮气提高采收率的机理、注气井组建设、制氮工艺及注气后的采油完井方式、方法。 相似文献
15.
The energies of various steps on the As-terminated GaAs(001)-2 × 4 surface are evaluated using a novel, approximate method of “linear combination of structural motifs”. It is based on the observation that previous total energy minimizations of semiconductor surfaces produced invariably equilibrium structures made of the same recurring local structural motifs, e.g. tetrahedral fourfold Ga, pyramidal threefold As, etc. Furthermore, such surface structures were found to obey consistently the octet rules as applied to the local motifs. We thus express the total energy of a given semiconductor surface as a sum of (i) the energies M of the local structural motifs appearing in the surface under consideration and (ii) an electrostatic term representing the Madelung energy of point charges resulting from application of the octet rule. The motif energies are derived from a set of pseudopotential total energy calculations for flat GaAs(001) surfaces and for point defects in bulk GaAs. This set of parameters suffices to reproduce the energies of other (001) surfaces, calculated using the same pseudopotential total energy approach. Application to GaAs(001)-2 × 4 surfaces with steps reveals the following. (i) “Primitive steps”, defined solely according to their geometries (i.e. step heights, widths and orientations) are often unstable. (ii) Additional, non-geometric factors beyond step geometries such as addition of surface adatoms, creation of vacancies and atomic rebonding at step edges are important to lower step energies. So is step-step interaction. (iii) The formation of steps is generally endothermic. (iv) The formation of steps with edges parallel to the direction of surface As dimers (A steps) is energetically favored over the formation of steps whose edges are perpendicular to the As dimers (B steps). 相似文献
16.
刘跃委 《石油化工安全环保技术》2002,18(4):26-28,31
重质糠醛精制装置设备腐蚀严重与糠醛氧化变质有关,通过分析装置设备腐蚀机理和糠醛氧化、变质的原因,提出了用N_2汽提回收和原料脱水等改进措施。 相似文献
17.
介绍近年来美国生物能源的开发进展情况及其先进的支撑系统,提出如何使我国氮肥工业在发展我国生物能源中起促进作用。 相似文献
18.
19.
Johan M. Thevelein 《Yeast (Chichester, England)》1994,10(13):1753-1790
20.
Simulation of water and nitrogen dynamics in soils during wastewater applications by using a finite-element model 总被引:4,自引:0,他引:4
Vassilis Z. Antonopoulos 《Water Resources Management》1993,7(3):237-251
A mathematical model was developed to simulate water movement, mass transport, and nitrogen transformations in soils during wastewater applications. The model is one-dimensional and based on the Galerkin finite-element method. The submodel of mass transport of nitrogen incorporates the convection-dispersion processes of ammonium and nitrate nitrogen, nitrification, denitrification, ammonium exchange and uptake of ammonium and nitrate ions. The accuracy and validity of the proposed model was examined by comparison with an explicit-implicit finite-difference model results. The model was used for simulation of water and nitrogen dynamics during wastewater application in homogeneous and multi-layered soils under different N concentration, rate, duration and scheduling of application. 相似文献