全文获取类型
收费全文 | 44025篇 |
免费 | 4546篇 |
国内免费 | 3113篇 |
专业分类
电工技术 | 2614篇 |
技术理论 | 1篇 |
综合类 | 4307篇 |
化学工业 | 6601篇 |
金属工艺 | 3173篇 |
机械仪表 | 1980篇 |
建筑科学 | 2960篇 |
矿业工程 | 2000篇 |
能源动力 | 1872篇 |
轻工业 | 3516篇 |
水利工程 | 1276篇 |
石油天然气 | 2616篇 |
武器工业 | 629篇 |
无线电 | 4487篇 |
一般工业技术 | 4801篇 |
冶金工业 | 3100篇 |
原子能技术 | 1057篇 |
自动化技术 | 4694篇 |
出版年
2024年 | 174篇 |
2023年 | 597篇 |
2022年 | 1172篇 |
2021年 | 1391篇 |
2020年 | 1610篇 |
2019年 | 1347篇 |
2018年 | 1359篇 |
2017年 | 1712篇 |
2016年 | 1891篇 |
2015年 | 1906篇 |
2014年 | 2819篇 |
2013年 | 3111篇 |
2012年 | 3398篇 |
2011年 | 3450篇 |
2010年 | 2583篇 |
2009年 | 2523篇 |
2008年 | 2290篇 |
2007年 | 2807篇 |
2006年 | 2357篇 |
2005年 | 2022篇 |
2004年 | 1760篇 |
2003年 | 1505篇 |
2002年 | 1269篇 |
2001年 | 1084篇 |
2000年 | 933篇 |
1999年 | 746篇 |
1998年 | 640篇 |
1997年 | 564篇 |
1996年 | 511篇 |
1995年 | 435篇 |
1994年 | 331篇 |
1993年 | 262篇 |
1992年 | 243篇 |
1991年 | 189篇 |
1990年 | 161篇 |
1989年 | 121篇 |
1988年 | 76篇 |
1987年 | 52篇 |
1986年 | 49篇 |
1985年 | 46篇 |
1984年 | 35篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 17篇 |
1978年 | 9篇 |
1975年 | 9篇 |
1966年 | 5篇 |
1959年 | 10篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
91.
Blatchford Kate E.; Diamond Keri; Westbrook R. Frederick; McNally Gavan P. 《Canadian Metallurgical Quarterly》2005,119(4):1034
The authors used rats to study the impact of a history of opiate exposures on behavioral and autonomic responses to restraint stress. Brief restraint (30 min) provoked tachycardia and a pressor response, anxiety (as indexed by social interaction), grooming, and reduced exploration. The pressor response was reduced at 1 day, but not 7 days, after last opiate exposure; tachycardia was unaffected (Experiment 1). Stress-induced anxiety was potentiated 1 and 7 days after last opiate exposure (Experiment 2), and this potentiation was a function of dose (Experiment 3) and duration (Experiment 4) of opiate exposure. The results show that a history of opiate exposures alters vulnerability to stress and has implications for understanding coping, anxiety, and emotionality in former opiate users. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
93.
R.C. Picu G. Vincze F. Ozturk J.J. Gracio F. Barlat A.M. Maniatty 《Materials Science and Engineering: A》2005,390(1-2):334-343
The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 °C and strain rates from 10−6 to 10−1 s−1. The strain rate sensitivity parameter is determined as a function of temperature and plastic strain, and the strain rate and temperature range in which dynamic strain aging leads to negative strain rate sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends. 相似文献
94.
A bending specimen that gives a constant energy release rate (independent on the crack length) under controlled displacement conditions is developed. It is assumed that engineering beam theory is applicable, i.e. that among other things, small deformations and linear elastic isotropic material can be assumed.A specific geometry is analyzed numerically by use of the finite element method and experimentally by manufacturing a specimen with the actual geometry in PMMA (polymethylmetacrylate) and then determining the specimen stiffness for different crack lengths.It is found that the geometry considered gives a constant energy release rate under controlled displacement conditions. 相似文献
95.
组合式空调系统设计中机组选型方法探讨 总被引:1,自引:0,他引:1
徐勇 《徐州建筑职业技术学院学报》2003,3(4):30-32
对目前组合式空调机组在选型设计及使用中出现的问题进行了分析,运用空气处理设备选型的有关理论和计算方法,对舒适性空调系统中机组选型的一些问题和数据进行了简化和近似处理,提出了能够满足工程设计的要求的简便实用的选型方法。 相似文献
96.
以一直径138cm的聚乙烯球作为中子慢化剂与全吸收探测器,采用全吸收法测量了钒球的14MeV中子的泄漏倍增率。用1支与H对热中子具有相同1/V吸收规律的^6Li玻璃探测器的测量子全吸收体的径向中子计数率分布。实验得到了钒球中心D-T中子时的Al、Fe、In和V一组阈探测器的绝对活化反应率的分布。用MCNP/4A程序、ENDF/B-Ⅵ和FENDL-2核数据进行了模拟计算。与实验结果相比较可知:用ENDF/B-Ⅵ库数据的计算结果与实验结果符合良好,而用FENDL-2库数据的计算结果比实验结果约高4%。 相似文献
97.
SABUL: A Transport Protocol for Grid Computing 总被引:5,自引:0,他引:5
This paper describes SABUL, an application-level data transfer protocol for data-intensive applications over high bandwidth-delay product networks. SABUL is designed for reliability, high performance, fairness and stability. It uses UDP to transfer data and TCP to return control messages. A rate-based congestion control that tunes the inter-packet transmission time helps achieve both efficiency and fairness. In order to remove the fairness bias between flows with different network delays, SABUL adjusts its sending rate at uniform intervals, instead of at intervals determined by round trip time. This protocol has demonstrated its efficiency and fairness in both experimental and practical applications. SABUL has been implemented as an open source C++ library, which has been successfully used in several Grid computing applications. 相似文献
98.
U. Rajendra AcharyaAuthor VitaeP. Subbanna BhatAuthor Vitae S.S. IyengarAuthor Vitae Ashok RaoAuthor VitaeSumeet DuaAuthor Vitae 《Pattern recognition》2003,36(1):61-68
The electrocardiogram is a representative signal containing information about the condition of the heart. The shape and size of the P-QRS-T wave, the time intervals between its various peaks, etc. may contain useful information about the nature of disease afflicting the heart. However, these subtle details cannot be directly monitored by the human observer. Besides, since bio-signals are highly subjective, the symptoms may appear at random in the time scale. Therefore, the signal parameters, extracted and analysed using computers, are highly useful in diagnostics. This paper deals with the classification of certain diseases using artificial neural network (ANN) and fuzzy equivalence relations. The heart rate variability is used as the base signal from which certain parameters are extracted and presented to the ANN for classification. The same data is also used for fuzzy equivalence classifier. The feedforward architecture ANN classifier is seen to be correct in about 85% of the test cases, and the fuzzy classifier yields correct classification in over 90% of the cases. 相似文献
99.
Some sufficient conditions concerning stability of solutions of stochastic differential evolution equations with general decay rate are first proved. Then, these results are interpreted as suitable stabilization ones for deterministic and stochastic systems. Also, they permit us to construct appropriate linear stabilizers in some particular situations. 相似文献
100.