全文获取类型
收费全文 | 55268篇 |
免费 | 6006篇 |
国内免费 | 4190篇 |
专业分类
电工技术 | 6305篇 |
技术理论 | 4篇 |
综合类 | 5659篇 |
化学工业 | 4377篇 |
金属工艺 | 4065篇 |
机械仪表 | 7551篇 |
建筑科学 | 2164篇 |
矿业工程 | 2417篇 |
能源动力 | 1201篇 |
轻工业 | 3574篇 |
水利工程 | 721篇 |
石油天然气 | 1123篇 |
武器工业 | 518篇 |
无线电 | 4720篇 |
一般工业技术 | 4577篇 |
冶金工业 | 2210篇 |
原子能技术 | 376篇 |
自动化技术 | 13902篇 |
出版年
2024年 | 361篇 |
2023年 | 1065篇 |
2022年 | 1750篇 |
2021年 | 1950篇 |
2020年 | 2107篇 |
2019年 | 1758篇 |
2018年 | 1505篇 |
2017年 | 1859篇 |
2016年 | 2062篇 |
2015年 | 2186篇 |
2014年 | 3443篇 |
2013年 | 3102篇 |
2012年 | 3883篇 |
2011年 | 4087篇 |
2010年 | 2984篇 |
2009年 | 2979篇 |
2008年 | 2914篇 |
2007年 | 3613篇 |
2006年 | 3512篇 |
2005年 | 2966篇 |
2004年 | 2436篇 |
2003年 | 2111篇 |
2002年 | 1872篇 |
2001年 | 1605篇 |
2000年 | 1340篇 |
1999年 | 1128篇 |
1998年 | 809篇 |
1997年 | 727篇 |
1996年 | 595篇 |
1995年 | 533篇 |
1994年 | 472篇 |
1993年 | 381篇 |
1992年 | 275篇 |
1991年 | 201篇 |
1990年 | 187篇 |
1989年 | 148篇 |
1988年 | 132篇 |
1987年 | 58篇 |
1986年 | 60篇 |
1985年 | 32篇 |
1984年 | 38篇 |
1983年 | 40篇 |
1982年 | 36篇 |
1981年 | 19篇 |
1980年 | 16篇 |
1979年 | 23篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1960年 | 7篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Yu. A. Radin I. A. Grishin T. S. Kontorovich O. B. Panshina A. V. Chugin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):113-119
Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of
flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine
units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW
upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced
stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace
boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer)
is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order
of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit
of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined.
__________
Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17. 相似文献
22.
23.
给定拓扑结构的网络的可靠性设计 总被引:6,自引:0,他引:6
本文首先讨论了网络链路堵概率的加权平均值,提出了网络分配的一般准则,并在考虑了网络链路生存链路概率的因素后,提出了更一般的网络链路堵塞概率的加权平均值,以此为基础,分别讨论了网络在给定点的费用条件下,使得网络可靠性最大的网络设计问题,以及在给定网络可靠性指标的前提下,使得网络费用最小的网络设计问题。 相似文献
24.
25.
陈小余 《中国计量学院学报》1997,(2)
用相干态的方法得到旋转磁场中自旋为j的粒子的态矢量的严格表达式,由此可计算相干态和叠加相干态的Abaronov-Anandan相位(AA相让).并具有清楚的物理图象. 相似文献
26.
简并量子拍频三能级系统中的光场压缩效应 总被引:10,自引:1,他引:9
本文讨论了V-型简并量子拍频三能级原子与单模相干辐射场相互作用时的动力学行为,并研究了光场的压缩效应。 相似文献
27.
An equation of state for 1,1-difluoroethane (HFC 152a, CH3CHF2) has been developed on the basis of reliable experimental data including PVT, liquid Cp, and saturated-liquid-density data measured by our group. It is a non-dimensionalized virial equation whose functional form is the same as that originally developed for 1,1,1,2-tetrafluoroethane (HFC 134a) in our group. The effective range is for pressures up to 15 MPa, temperatures from 230 to 450 K, and densities to 1000 kg m−3. The equation represents reliable PVT measurements within ± 1% in pressure for the superheated vapour and supercritical fluid, while within ±0.5% in density for the compressed liquid. In addition, it should be noted that the equation represents the other essential thermodynamic properties including vapour pressures, saturated-liquid/ vapour densities, isobaric/isochoric specific heats and sound velocity in both the liquid and gaseous phase of HFC 152a. 相似文献
28.
Francis E. Powell Brian W. Brooks 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,57(1):65-71
Dimensionless material balance equations describing an uninhibited enzyme hydrolysis process in a semi-batch reactor (i.e. fed-batch reactor) are formulated; numerical solution of these equations provided concentration profiles of the enzyme-substrate complex by using published kinetic parameters. The unrestricted values obtained are compared with estimates based separately on the reaction steady state and stationary state assumptions. Results are discussed in terms of the enzyme/substrate inventory used and it is found that the reaction steady state is a satisfactory approximation only when this ratio is sufficiently small. The stationary state may be a better approximation at other values, particularly when enzyme is added to substrate or when an empty tank is being filled. Reaction yields from semi-batch and batch operations are compared. Processing takes longer in the semi-batch operations and complete conversions are only practical in this mode when enzyme is added to substrate. 相似文献
29.
Sensitivity analysis is used to show how uncertainties in basic factors, such as heat transfer, pressure drop, compressor efficiency, and thermophysical properties, influence the result of heat pump cycle performance estimations. By comparing the results of this analysis with uncertainty levels of estimations and experimental determinations, it is established to what extent improvements in accuracy are needed. The investigation was carried out for several different applications and, as working fluids, both pure substances and non-azeotropic mixtures were examined. It was found that evaporation heat transfer and compressor efficiency are two areas where improvements are needed. It is also shown that estimates using very accurate, substance-specific, equations of state differ from those using more general types by up to 1 % for COP and 2% for capacity. 相似文献
30.