全文获取类型
收费全文 | 586059篇 |
免费 | 108723篇 |
国内免费 | 76438篇 |
专业分类
电工技术 | 62498篇 |
技术理论 | 1篇 |
综合类 | 66702篇 |
化学工业 | 72373篇 |
金属工艺 | 52846篇 |
机械仪表 | 37207篇 |
建筑科学 | 43011篇 |
矿业工程 | 30514篇 |
能源动力 | 18033篇 |
轻工业 | 63223篇 |
水利工程 | 20563篇 |
石油天然气 | 26344篇 |
武器工业 | 9455篇 |
无线电 | 70121篇 |
一般工业技术 | 59040篇 |
冶金工业 | 23229篇 |
原子能技术 | 8534篇 |
自动化技术 | 107526篇 |
出版年
2024年 | 3973篇 |
2023年 | 10531篇 |
2022年 | 21345篇 |
2021年 | 26857篇 |
2020年 | 22665篇 |
2019年 | 25032篇 |
2018年 | 26986篇 |
2017年 | 30141篇 |
2016年 | 28415篇 |
2015年 | 35285篇 |
2014年 | 39339篇 |
2013年 | 43214篇 |
2012年 | 50569篇 |
2011年 | 49328篇 |
2010年 | 46304篇 |
2009年 | 42044篇 |
2008年 | 41616篇 |
2007年 | 40101篇 |
2006年 | 34323篇 |
2005年 | 28563篇 |
2004年 | 24167篇 |
2003年 | 16784篇 |
2002年 | 15625篇 |
2001年 | 13913篇 |
2000年 | 11840篇 |
1999年 | 6962篇 |
1998年 | 4543篇 |
1997年 | 3980篇 |
1996年 | 3826篇 |
1995年 | 3746篇 |
1994年 | 3043篇 |
1993年 | 2861篇 |
1992年 | 2782篇 |
1991年 | 2019篇 |
1990年 | 1614篇 |
1989年 | 1531篇 |
1988年 | 1124篇 |
1987年 | 383篇 |
1986年 | 319篇 |
1985年 | 240篇 |
1984年 | 174篇 |
1983年 | 139篇 |
1982年 | 186篇 |
1981年 | 221篇 |
1980年 | 220篇 |
1979年 | 139篇 |
1976年 | 226篇 |
1975年 | 203篇 |
1972年 | 235篇 |
1960年 | 205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
薄层反射波非零炮检距的属性特征 总被引:1,自引:0,他引:1
本文从薄层顶、底界面反射波的走时入手,研究了薄层反射波在非零炮检距集上出现的干涉现象,导出了薄层反射波在出现干涉时的炮检距计算公式,说明薄层干涉出现的炮检距是多变量函数,即随着埋藏深度h、地层速度v、薄层厚度Δh以及地震波的主频f*的变化而改变。本文重点分析了地层厚度Δh和地震子波主频f*对反射波振幅特性和频率特性的影响。在充分分析薄层反射的振幅、频谱随炮检距变化关系的基础上,指出在应用叠前信息(如AVO分析)进行储层预测等方面的研究时,应充分考虑薄层反射波的干涉和调谐现象带来的振幅和频率特征的变化。 相似文献
952.
953.
954.
This paper introduces the research progress of the State Key Laboratory of Information Security (SKLOIS) in China during 2002–2006.
This introduction covers four selected areas with each covering some selected research findings. The four selected areas are:
the fundamentals of cryptography; the design, analysis and testing of block cipher algorithms; the design and analysis of
security protocols based on computational intractability; authentication, authorization and their applications. 相似文献
955.
Vincenzo Augelli Teresa Ligonzo Roberto Murri Luigi Schiavulli 《Thin solid films》1989,170(2):163-170
Hydrogenated and chlorinated silicon films were used to deposit Schottky barrier solar cells. Photovoltaic characterization, together with the results of electronic transport measurements, led to the conclusion that the presence of chlorine is detrimental to the properties of this kind of device. 相似文献
956.
Sidhartha R. Das Basheer M. Khumawala 《International Journal of Flexible Manufacturing Systems》1991,3(2):121-147
Flexible manufacturing systems (FMSs) are a class of automated systems that can be used to improve productivity in batch manufacturing. Four stages of decision making have been defined for an FMS—the design, planning, scheduling, and control stages. This research focuses on the planning stage, and specifically in the area of scheduling batches of parts through the system.The literature to date on the FMS planning stage has mostly focused on the machine grouping, tool loading, and parttype selection problems. Our research carries the literature a step further by addressing the problem of scheduling batches of parts. Due to the use of serial-access material-handling systems in many FMSs, the batch-scheduling problem is modeled for a flexible flow system (FFS). This model explicitly accounts for setup times between batches that are dependent on their processing sequence.A heuristic procedure is developed for this batch-scheduling problem—the Maximum Savings (MS) heuristic. The MS heuristic is based upon the savings in time associated with a particular sequence and selecting the one with the maximum savings. It uses a two-phase method, with the savings being calculated in phase I, while a branch-and-bound procedure is employed to seek the best heuristic solution in phase II. Extensive computational results are provided for a wide variety of problems. The results show that the MS heuristic provides good-quality solutions. 相似文献
957.
Zinc-containing nanoparticles stable in the liquid phase are synthesized by the radiation chemical reduction of zinc ions
in solutions of inverse micelles. The effects of the absorbed radiation dose and the size of the micelle water pool on the
spectral characteristics of samples are studied. The HPLC and electron microscopy results indicate that the composition of
nanoparticles synthesized depends on the salt nature.
Original Russian Text ? A.A. Revina, E.V. Oksentyuk, A.A. Fenin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No.
6, pp. 613–618. 相似文献
958.
BT项目实施模式分析 总被引:1,自引:0,他引:1
根据实践中出现的各种BT项目管理模式,归纳出了具有代表性的“施工二次招标型BT模式,直接施工型BT模式,施工同体型BT模式,带资承包型BT模式”四种BT项目管理模式,并根据现行法律法规对其适用性和实施中应注意的问题进行了论述。 相似文献
959.
Li Yonghua Wang Chunbo Chen Hongwei 《Frontiers of Energy and Power Engineering in China》2007,1(1):96-100
Power plants in China have to burn blended coal instead of one specific coal for a variety of reasons. So it is of great necessity
to investigate the combustion of blended coals. Using a test rig with a capacity of 640 MJ/h with an absolute milling system
and flue gas online analysis system, characteristics such as burnout, slag, and pollution of some blended coals were investigated.
The ratio of coke and slag as a method of distinguishing coal slagging characteristic was introduced. The results show that
the blending of coal has some effect on NO
x
but there is no obvious rule. SO
x
emission can be reduced by blending low sulfur coal.
Translated from Proceedings of the CSEE, 2005, 25(18): 97–103 [译自: 中国电机工程学报] 相似文献
960.