全文获取类型
收费全文 | 230662篇 |
免费 | 17696篇 |
国内免费 | 9207篇 |
专业分类
电工技术 | 12581篇 |
技术理论 | 24篇 |
综合类 | 14237篇 |
化学工业 | 39219篇 |
金属工艺 | 13214篇 |
机械仪表 | 14622篇 |
建筑科学 | 17741篇 |
矿业工程 | 7550篇 |
能源动力 | 6450篇 |
轻工业 | 13578篇 |
水利工程 | 3645篇 |
石油天然气 | 16737篇 |
武器工业 | 1667篇 |
无线电 | 25280篇 |
一般工业技术 | 27588篇 |
冶金工业 | 12864篇 |
原子能技术 | 2269篇 |
自动化技术 | 28299篇 |
出版年
2024年 | 1008篇 |
2023年 | 3830篇 |
2022年 | 6537篇 |
2021年 | 9190篇 |
2020年 | 7156篇 |
2019年 | 6058篇 |
2018年 | 6791篇 |
2017年 | 7592篇 |
2016年 | 6810篇 |
2015年 | 8931篇 |
2014年 | 11336篇 |
2013年 | 13377篇 |
2012年 | 14297篇 |
2011年 | 15584篇 |
2010年 | 13533篇 |
2009年 | 12776篇 |
2008年 | 12454篇 |
2007年 | 11938篇 |
2006年 | 12465篇 |
2005年 | 10844篇 |
2004年 | 7328篇 |
2003年 | 6268篇 |
2002年 | 5510篇 |
2001年 | 4923篇 |
2000年 | 5502篇 |
1999年 | 6497篇 |
1998年 | 5481篇 |
1997年 | 4474篇 |
1996年 | 4206篇 |
1995年 | 3520篇 |
1994年 | 2825篇 |
1993年 | 1983篇 |
1992年 | 1544篇 |
1991年 | 1229篇 |
1990年 | 937篇 |
1989年 | 742篇 |
1988年 | 538篇 |
1987年 | 336篇 |
1986年 | 280篇 |
1985年 | 196篇 |
1984年 | 139篇 |
1983年 | 114篇 |
1982年 | 125篇 |
1981年 | 98篇 |
1980年 | 71篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
RoleofREandMgonGraphitizationofSpheroidalGraphiteMalleableCastIron¥LiuJin-Hai(HebeiInstituteofTechnotogy,Mianjin300130,China)... 相似文献
92.
The changes in the intestinal mucosal permeability were observed by quantitatively assessing plasma to luminal clearance of 99mTc-labeled DTPA, and the influence of platelet activating factor (PAF) on it was investigated. The results showed that intestinal permeability was significantly elevated after severe burn and was positively correlated with increase in PAF in the intestinal tissue (r = 0.94, P < 0.01). PAF antagonist therapy could significantly attenuate postburn intestinal mucosal permeability. It is concluded that PAF is one of the important factors causing increased intestinal permeability after severe burn. 相似文献
93.
Microorganisms capable of degrading di-n-butyl phthalate (DBP) were isolated. The characteristics of DBP biodegradation by immobilized and free cells were investigated. The experimental results showed that the rate of DBP degradation of immobilized cells was higher than that of free cells. 相似文献
94.
Chun Hu Ji Zhao Li G.P. Liu P. Worley E. White J. Kjar R. 《Electron Device Letters, IEEE》1995,16(2):61-63
The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process 相似文献
95.
96.
Two kinds of biosensors for amino acids (one with nonspecific enzyme as bioelement, the other with specific enzyme(s) as bioelement),
including their principles, applications, recent researches and future trends were discussed in detail. 61 references were
given.
A part of work for gaining Ph. D in chemical and biochemical application at FPMs (Mons, Belgique)
Synopsis of the first author Xia Jinlan, Male, born in 1963, now at Facult’e Polytechnique de Mons, Belgique 相似文献
97.
Liu Y. Blostein S.D. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1992,38(1):177-182
Bayesian analysis is used to show that Wald's sequential probability ratio test with varying thresholds is optimal for the nonstationary situation, where the observed samples are independent but not identically distributed. Some important properties useful for the design of the test thresholds are discussed. Wald's lower bound, generalized to the nonstationary situation, is also presented. The results have important applications in situations where the observed signal is time-varying. such as in radar signal processing, image processing, and spread spectrum communications 相似文献
98.
99.
100.
单元系T—p相图的数学结构 总被引:1,自引:0,他引:1
作者以化学元素的稳定单质为基准,推演出了任意物质M_i(相态Ω)的热力学生成活度{相态Ω)的函数形式:?D_Ω数值的大小体现着相态Ω的热力学相对稳定性.根据集合论原理沿D(稳定性)座标取极大值的方法把物理性质互不连续的各个异相态连结在一起,建立了单元系在T-p面上的优势分布方程(PSDE):■作者以H_2O为实例,计算了T-p相图,与实验相图基本一致. 相似文献