全文获取类型
收费全文 | 125220篇 |
免费 | 12201篇 |
国内免费 | 8079篇 |
专业分类
电工技术 | 9371篇 |
技术理论 | 9篇 |
综合类 | 9981篇 |
化学工业 | 18460篇 |
金属工艺 | 7984篇 |
机械仪表 | 8589篇 |
建筑科学 | 10166篇 |
矿业工程 | 4060篇 |
能源动力 | 3765篇 |
轻工业 | 8946篇 |
水利工程 | 3029篇 |
石油天然气 | 6210篇 |
武器工业 | 1436篇 |
无线电 | 15063篇 |
一般工业技术 | 13451篇 |
冶金工业 | 5148篇 |
原子能技术 | 1795篇 |
自动化技术 | 18037篇 |
出版年
2024年 | 559篇 |
2023年 | 1742篇 |
2022年 | 3407篇 |
2021年 | 4909篇 |
2020年 | 3720篇 |
2019年 | 3094篇 |
2018年 | 3355篇 |
2017年 | 3941篇 |
2016年 | 3659篇 |
2015年 | 5291篇 |
2014年 | 6735篇 |
2013年 | 7820篇 |
2012年 | 9249篇 |
2011年 | 10182篇 |
2010年 | 9173篇 |
2009年 | 8818篇 |
2008年 | 8913篇 |
2007年 | 8632篇 |
2006年 | 8095篇 |
2005年 | 6493篇 |
2004年 | 4716篇 |
2003年 | 3926篇 |
2002年 | 3887篇 |
2001年 | 3256篇 |
2000年 | 2672篇 |
1999年 | 2108篇 |
1998年 | 1384篇 |
1997年 | 1148篇 |
1996年 | 1003篇 |
1995年 | 830篇 |
1994年 | 700篇 |
1993年 | 499篇 |
1992年 | 357篇 |
1991年 | 280篇 |
1990年 | 210篇 |
1989年 | 183篇 |
1988年 | 116篇 |
1987年 | 93篇 |
1986年 | 81篇 |
1985年 | 33篇 |
1984年 | 36篇 |
1983年 | 38篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1959年 | 18篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
A novel fully conjugated polymer containing 1,10‐phenanthroline (DAPcDOD) was first synthesized by the polycondensation of 2,7‐dimethyl‐2,4,6‐octatriene‐1,8‐dial with 5,6‐diamine‐1,10‐phenanthroline. Three polymeric complexes were first prepared by the reaction of DAPcDOD with NiSO4, CoCl2, and FeSO4, respectively. The structures of the polymer and the complexes were characterized by IR, 1H‐NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0–50 kOe) at 5 K and as a function of temperature (5–300 K) at a magnetic field strength of 30 kOe. The results show that DAPcDOD–Ni2+ and DAPcDOD–Co2+ were soft ferromagnets, whereas DAPcDOD–Fe2+ exhibited the features of an antiferromagnet. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
42.
A simple and novel ultra-wideband microstrip-fed antenna with dual band-notched characteristic is presented. By etching a pair of asymmetrical spurlines on the feedline, two notched bands of 600 MHz (3.95? 4.55 GHz) and 650 MHz (5.35?6.0 GHz) are achieved. Measured results show that this antenna operates from 2.5 to 12.0 GHz for voltage standing wave ratio less than 2, except two frequency notched bands of 3.95?4.55 GHz and 5.35?6.0 GHz. Moreover, this antenna has good omnidirectional radiation patterns in the H-plane. 相似文献
43.
44.
Woo Yong Sung Seung Min Lee Wal Jun Kim Jong Girl Ok Ho Young Lee Yong Hyup Kim 《Diamond and Related Materials》2008,17(6):1003-1007
Complementary electroplating combined with electrophoresis enhanced the field emission characteristics of emitters by improving the adhesions between CNT emitters and substrate. The emitting current of the CNT emitters prepared by our combined method increased nine times higher than that of CNT emitters prepared by electrophoresis only, since electroplating improved the adhesion of CNT emitters. During the life-time measurement for 10 h, the emitting current of CNT emitters fabricated by electrophoresis only was drastically decreased to 13% of the initial current, while that prepared by the combination of electrophoresis and successive electroplating decreased to 64% of the initial current. We suggest that our method is a promising approach for the efficient fabrication of reliable CNT emitters. 相似文献
45.
Wenying Wei Zhen Wang Yanhua Yin Jinyu Han Wen Xu 《Korean Journal of Chemical Engineering》2008,25(3):562-567
Composition Group Vector Space (CGVS) method for estimating melting and boiling point T
m
, T
b
of organic compound has been proposed, and the principle of this method has been elucidated. The models for estimating T
m
, T
b
have been established and the numerical values of relative parameters have been presented. The average percentage deviations
of T
m
, T
b
estimation are 7.53 and 1.58, respectively, which show that the present method demonstrates significant improvement in applicability
to predict the above properties, compared to conventional group methods. 相似文献
46.
47.
48.
化学镀Ni—P镀层的X射线衍射研究 总被引:2,自引:0,他引:2
根据X射线衍射分析结果,对化学镀高P(含P>11wt%或19at%)Ni-P镀层加热时效时,镀层成分和加热温度对结构转变的影响作了研究,结果表明,高P共晶、过共晶(含P>11wt%或19at%)合金的结构转变有如下特征:(1)相同加热时效条件下,Ni-P合金的结构转变与成分有密切关系:(2)对同一成分的过共晶合金,Ni-P合金的结构转变与时效温度密切相关;(3)过共晶合金在290~360℃温度范围内时效处理,出现Ni_xP_y介稳相,X射线衍射分析认为Ni_xP_y为Ni_(12)P_5。 相似文献
49.
Plasmapropertiesoflaser-ablatedSttargetinairWangXiang-Tai(王象泰);ManBao-Yuan(满宝元);WangGong-Tang(王公堂);FanXi-Jun(樊锡君);WangJun(王军)... 相似文献
50.
BID: a novel BH3 domain-only death agonist 总被引:1,自引:0,他引:1
K Wang XM Yin DT Chao CL Milliman SJ Korsmeyer 《Canadian Metallurgical Quarterly》1996,10(22):2859-2869
The BCL-2 family of proteins consists of both antagonists (e.g., BCL-2) and agonists (e.g., BAX) that regulate apoptosis and compete through dimerization. The BH1 and BH2 domains of BCL-2 are required to heterodimerize with BAX and to repress cell death; conversely, the BH3 domain of BAX is required to heterodimerize with BCL-2 and to promote cell death. To extend this pathway, we used interactive cloning to identify Bid, which encodes a novel death agonist that heterodimerizes with either agonists (BAX) or antagonists (BCL-2). BID possesses only the BH3 domain, lacks a carboxy-terminal signal-anchor segment, and is found in both cytosolic and membrane locations. BID counters the protective effect of BCL-2. Moreover, expression of BID, without another death stimulus, induces ICE-like proteases and apoptosis. Mutagenesis revealed that an intact BH3 domain of BID was required to bind the BH1 domain of either BCL-2 or BAX. A BH3 mutant of BID that still heterodimerized with BCL-2 failed to promote apoptosis, dissociating these activities. In contrast, the only BID BH3 mutant that retained death promoting activity interacted with BAX, but not BCL-2. This BH3-only molecule supports BH3 as a death domain and favors a model in which BID represents a death ligand for the membrane-bound receptor BAX. 相似文献