全文获取类型
收费全文 | 40755篇 |
免费 | 3600篇 |
国内免费 | 2103篇 |
专业分类
电工技术 | 975篇 |
综合类 | 2868篇 |
化学工业 | 8272篇 |
金属工艺 | 1434篇 |
机械仪表 | 3759篇 |
建筑科学 | 1953篇 |
矿业工程 | 1240篇 |
能源动力 | 3063篇 |
轻工业 | 1365篇 |
水利工程 | 825篇 |
石油天然气 | 6726篇 |
武器工业 | 861篇 |
无线电 | 948篇 |
一般工业技术 | 4807篇 |
冶金工业 | 1068篇 |
原子能技术 | 666篇 |
自动化技术 | 5628篇 |
出版年
2024年 | 199篇 |
2023年 | 727篇 |
2022年 | 1257篇 |
2021年 | 1453篇 |
2020年 | 1366篇 |
2019年 | 1304篇 |
2018年 | 1160篇 |
2017年 | 1444篇 |
2016年 | 1688篇 |
2015年 | 1749篇 |
2014年 | 2428篇 |
2013年 | 2710篇 |
2012年 | 2501篇 |
2011年 | 3182篇 |
2010年 | 2177篇 |
2009年 | 2283篇 |
2008年 | 2021篇 |
2007年 | 2393篇 |
2006年 | 2286篇 |
2005年 | 1948篇 |
2004年 | 1660篇 |
2003年 | 1488篇 |
2002年 | 1228篇 |
2001年 | 943篇 |
2000年 | 803篇 |
1999年 | 705篇 |
1998年 | 621篇 |
1997年 | 495篇 |
1996年 | 433篇 |
1995年 | 374篇 |
1994年 | 282篇 |
1993年 | 205篇 |
1992年 | 162篇 |
1991年 | 143篇 |
1990年 | 122篇 |
1989年 | 115篇 |
1988年 | 81篇 |
1987年 | 50篇 |
1986年 | 48篇 |
1985年 | 38篇 |
1984年 | 32篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1959年 | 10篇 |
1955年 | 5篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
超临界流体中的酶催化 总被引:3,自引:0,他引:3
与其他非水相酶催化介质相比 ,超临界流体有其独特的优越性。阐述了超临界流体的概念、对超临界流体的选择原则以及在超临界流体中酶催化的各种影响因素 ,还讨论了在此类流体中酶催化的应用和发展前景 相似文献
92.
This clinical study illustrates the developmental nature of homoerotic transference, when the psychoanalyst is attuned to the evolving dynamics of the mourning process, in this case with a lesbian analysand. The analysand's psychic fantasies of the female analyst as a muse and a demon lover figure are seen to transform into discrete mother and father transferences, as split off feminine and aggressive parts of the self are reintegrated along with heterosexual desires and oedipal desires. Protosymbolic enactments in terms of romantic gift giving and other seductive overtures transform into symbolic expressions of love, concern, regret, and tenderness. A lesbian marriage is preserved, and the loss of intimacy with men is mourned so that desires for intimacy with men can be sublimated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
We constructed a probabilistic simulator that allows all the events in population dynamics such as death, birth, mutation,
and suppression/stimulation to be described by probabilistic rules. The simulator also facilitates a lattice used for expressing
distribution and diversity (number of distinct strains) of quasispecies. The simulator is used to investigate the diversity
threshold in HIV and T-cell interaction.
This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January
31–February 2, 2008 相似文献
94.
对Daleel油田作业5区三分支水平井DL-59井井下复杂情况分析,室内测定了引起复杂情况的Nahr Umr泥页岩地层的矿物组分和粘土矿物含量,优选了适应在该泥页岩地层215.9 mm造斜井段的钻井液配方中的各种处理剂,最后研制出钻井液配方,通过DL-73井应用后,取得了良好的防塌效果. 相似文献
95.
T.S. Gates G.M. Odegard S.J.V. Frankland T.C. Clancy 《Composites Science and Technology》2005,65(15-16):2416
The paper provides details on the current approach to multi-scale modeling and simulation of advanced materials for structural applications. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation are highlighted and discussed. 相似文献
96.
以塔河减压渣油(简称塔河减渣)为原料,在实验室小型试验装置和中型连续试验装置上,对在较高温度条件下催化临氢热转化加工塔河减渣的工艺操作条件及改质效果进行了系统研究。采用高分散的油溶性催化剂,在高压釜反应器中考察了反应温度、反应压力、催化剂添加量、溶剂油添加量、反应时间以及助剂添加量对塔河减渣催化临氢热转化反应的转化率和缩合率的影响,优化了操作参数。在优化的操作条件下,进行了塔河减渣催化临氢热转化中型试验,得到初馏点大于524 ℃组分的裂化率为85.2%,馏分油收率为80%,金属(Ni+V)和沥青质脱除率均大于90%。 相似文献
97.
This article presents results from a numerical study of pulsating jet impingement heat transfer. The motivation is to seek conditions offering a significant enhancement compared to steady flow impingement drying. The CFD software package FLUENT was used for simulating slot-type pulsating jet impingement flows with confinement. The parameter study included velocity amplitude ratio, mean jet velocity, and pulsation frequency. The distance from nozzle exit to surface was three times the hydraulic diameter of the nozzle. The Reynolds number based on the nozzle hydraulic diameter and jet temperature was 2,460 with a mean jet velocity of 30 m/s, which is the base case of the numerical experiments. Results showed that time-averaged surface heat transfer increased with increasing velocity amplitude for the same mean jet velocity. Large velocity amplitudes helped enhance heat transfer by two mechanisms: high jet velocity during the positive cycle and strong recirculating flows during the negative cycle. For the cases with different mean jet velocities but the same maximum velocity, time-averaged surface heat flux decreased with decreasing mean jet velocity. As for the effects of pulsation frequency, with high-velocity amplitude ratio, time-averaged surface heat fluxes were at the same level regardless of frequency. However, at low-velocity amplitude ratio, high frequency caused stronger recirculating flows resulting in greater heat transfer compared to the cases with a lower frequency. 相似文献
98.
99.
成品油储罐内的腐蚀及防护 总被引:1,自引:0,他引:1
对成品油储罐内各部位腐蚀情况进行了介绍,说明了产生腐蚀的原因和腐蚀机理。介绍了油罐内防护技术,采用节点加固,降低边缘应力,可减缓油罐金属腐蚀速度;对选用油罐内防腐涂料的原则进行了阐述。 相似文献
100.
Prediction of the effects on dynamic response due to distributed structural modification with additional degrees of freedom 总被引:1,自引:0,他引:1
Huajiang Hang Krishna Shankar Joseph C.S. Lai 《Mechanical Systems and Signal Processing》2008,22(8):1809-1825
The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic properties of a complex structure. The dynamic properties of the modified structure can be determined by experimental testing or numerical simulation, both of which are complex, expensive and time-consuming. Assuming that the original dynamic characteristics are already established and that the modification is a relatively simple attachment, the modified dynamic properties may be determined numerically without solving the equations of motion of the full-modified structure. The frequency response functions (FRFs) of the modified structure can be computed by coupling the original FRFs and a delta dynamic stiffness matrix for the modification introduced. The validity of this approach is investigated by applying it to a cantilever beam to which a smaller beam is attached as modification. The original FRFs were obtained experimentally as well as numerically. The delta dynamic stiffness matrix was determined numerically by modeling the attachment and part of the original structure including the attachment points. The FRFs of the modified beam were then computed. Good agreement is obtained by comparing the results to the FRFs of the modified beam determined experimentally as well as by numerical modeling of the complete modified structure. 相似文献