全文获取类型
收费全文 | 14066篇 |
免费 | 1718篇 |
国内免费 | 1400篇 |
专业分类
电工技术 | 214篇 |
技术理论 | 1篇 |
综合类 | 847篇 |
化学工业 | 7132篇 |
金属工艺 | 640篇 |
机械仪表 | 408篇 |
建筑科学 | 393篇 |
矿业工程 | 195篇 |
能源动力 | 443篇 |
轻工业 | 379篇 |
水利工程 | 168篇 |
石油天然气 | 270篇 |
武器工业 | 1163篇 |
无线电 | 556篇 |
一般工业技术 | 1481篇 |
冶金工业 | 303篇 |
原子能技术 | 204篇 |
自动化技术 | 2387篇 |
出版年
2024年 | 32篇 |
2023年 | 229篇 |
2022年 | 299篇 |
2021年 | 441篇 |
2020年 | 443篇 |
2019年 | 493篇 |
2018年 | 446篇 |
2017年 | 500篇 |
2016年 | 516篇 |
2015年 | 747篇 |
2014年 | 1081篇 |
2013年 | 1034篇 |
2012年 | 1169篇 |
2011年 | 1252篇 |
2010年 | 1041篇 |
2009年 | 1032篇 |
2008年 | 866篇 |
2007年 | 989篇 |
2006年 | 780篇 |
2005年 | 684篇 |
2004年 | 586篇 |
2003年 | 493篇 |
2002年 | 339篇 |
2001年 | 272篇 |
2000年 | 234篇 |
1999年 | 189篇 |
1998年 | 124篇 |
1997年 | 101篇 |
1996年 | 104篇 |
1995年 | 88篇 |
1994年 | 72篇 |
1993年 | 57篇 |
1992年 | 85篇 |
1991年 | 52篇 |
1990年 | 41篇 |
1989年 | 52篇 |
1988年 | 18篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 21篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 12篇 |
1976年 | 5篇 |
1959年 | 7篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
微波萃取在食品化学中的应用 总被引:16,自引:0,他引:16
介绍了微波萃取技术在食品化学中的应用。其实质是用微波对萃取溶剂及物料加热,使溶剂的渗透率和扩散率大大提高,因此对食品营养成分或风味物质可以有铲地萃取分离。 相似文献
53.
54.
Ken Kato Yasuhiro Kasuga Masanori Fujiwara Kazuo Onda 《Electrical Engineering in Japan》1996,116(4):94-108
Laboratory-scale and parametric experiments of SO2 and NOx removal from the simulated combustion gas by pulsed corona discharge have been performed by changing the combustion gas composition and temperature, the electrode configuration of plasma reactor, and the polarity of high-voltage electrode. The following results are obtained: 1) the higher the concentration of H2O and O2, the higher the efficiency of desulfurization and denitrification at the same specific input; 2) the pulsed corona discharge with a voltage pulsewidth as short as 200 ns of negative polarity shows the possibility to attain almost 90 percent deSOx and deNOx efficiency at the specific discharge input of 20 J/g, which is almost the same as the specific input in the electron-beam process; 3) the deNOx characteristics show a little temperature dependence in the range of 70 to 130°C, but the deSOx efficiency increases rapidly in the temperature region below 100°C suggesting the thermochemical dependence of deSOx reaction; 4) when desulfurization and denitrification proceed, the white dendritic powder deposits on the plasma reactor whose composition is identified to be 49 mol% (NH4)2SO4 and 47 mol% of 2NH4NO3 · (NH4)2SO4, and the ratio of SO2, NO and NH3 of the deposit is almost equal to that of supplied gas. 相似文献
55.
Stress Concentration Factors for a Circular Hole in Curved Beams Under Bending Loads 总被引:1,自引:0,他引:1
Abstract: As a contribution to the field of stress concentration studies, the case of circular hole in curved bar elements under bending is hereby studied. Trend values of stress concentration factors (SCF) are presented based on selected variables of the problem for two critical hole locations. The results will help to identify an SCF law for practical use by applying the statistical method of regression analysis. Two approximations obtained by means of computational methods are compared with those obtained by photoelastic experimental method. 相似文献
56.
The electronic structures of rare earth cluster halides R(R_6X_(12)) and their interstitial compounds R_7X_(12)Zwere studied by the DV-X_(?) method (R=Sc,Y,Pr,Gd or Er;X=Cl,Br or I;Z=B,C,N,Fe,Co or Ru).Theresults show that because f electrons in empty rare earth cluster are screened,their orbitals are more difficult tooverlap each other,a deficiency of skeleton orbitals in cluster causing the system to be unstable.They are easilycondensed into chain compound R_2X_3 or R_5X_8.If a light atom of main group is embedded into octahedralcluster,bonding orbitals formed from interstitial atom and rare earth cluster strengthen clusterskeleton bond in the system to reach structural stability.If embedded atom belongs to transition metal,bondingorbitals composed of that of interstitial atom and rare earth cluster take the place of original cluster skeletonorbitals to form heteronuclear metal cluster (or double-coordination compound). 相似文献
57.
求解机械装配规划的新方法 总被引:6,自引:0,他引:6
本文提出一个求解机械装配规划的算法,其计算量~O(sN~2),其中s是零件所有可能装配方向的个数,N是工件的零件数(一般s~O(N)).而现行的求机械装配规划的算法,其计算量均随N的增加按指数律增加. 相似文献
58.
Makoto Kohga 《含能材料》2006,14(6):471-474
1 IntroductionThe ammonium perchlorate ( AP)-based compositepropellant is currently the most widely used one becausethis propellant has good burning characteristics and me-chanical properties. One of the few serious drawbacks ofthe AP-based propellant is that its products of combus-tion, which include HCl, chlorine, and chlorine oxides,cause atmospheric pollution. Increasing concern for aclean atmosphere in recent years has resulted in a com-pelling need for developing a chlorine-free,enviro… 相似文献
59.
A. Samuelsson O. C. Zienkiewicz 《International journal for numerical methods in engineering》2006,67(2):149-157
This paper presents a brief history of the development of the stiffness method. We start by tracing the evolution of the method to solve discrete‐type problems such as trusses and frames composed of two node members. We then describe the method as it is applied to solve continuum problems modelled by finite‐difference and finite‐element methods. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
60.
We consider the problem of finding a transitive orientation of a comparability graph, such that the edge set of its covering graph contains a given subset of edges. We propose a solution which employs the classical technique of modular tree decomposition. The method leads to a polynomial time algorithm to construct such an orientation or report that it does not exist. 相似文献