全文获取类型
收费全文 | 7410篇 |
免费 | 351篇 |
国内免费 | 171篇 |
专业分类
电工技术 | 193篇 |
综合类 | 252篇 |
化学工业 | 733篇 |
金属工艺 | 223篇 |
机械仪表 | 205篇 |
建筑科学 | 335篇 |
矿业工程 | 139篇 |
能源动力 | 111篇 |
轻工业 | 255篇 |
水利工程 | 87篇 |
石油天然气 | 150篇 |
武器工业 | 46篇 |
无线电 | 679篇 |
一般工业技术 | 690篇 |
冶金工业 | 3227篇 |
原子能技术 | 50篇 |
自动化技术 | 557篇 |
出版年
2024年 | 23篇 |
2023年 | 82篇 |
2022年 | 148篇 |
2021年 | 197篇 |
2020年 | 114篇 |
2019年 | 123篇 |
2018年 | 143篇 |
2017年 | 152篇 |
2016年 | 119篇 |
2015年 | 181篇 |
2014年 | 178篇 |
2013年 | 225篇 |
2012年 | 230篇 |
2011年 | 285篇 |
2010年 | 250篇 |
2009年 | 240篇 |
2008年 | 280篇 |
2007年 | 214篇 |
2006年 | 197篇 |
2005年 | 151篇 |
2004年 | 103篇 |
2003年 | 100篇 |
2002年 | 95篇 |
2001年 | 104篇 |
2000年 | 116篇 |
1999年 | 210篇 |
1998年 | 1105篇 |
1997年 | 657篇 |
1996年 | 367篇 |
1995年 | 237篇 |
1994年 | 219篇 |
1993年 | 226篇 |
1992年 | 43篇 |
1991年 | 48篇 |
1990年 | 42篇 |
1989年 | 61篇 |
1988年 | 56篇 |
1987年 | 43篇 |
1986年 | 49篇 |
1985年 | 36篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 28篇 |
1981年 | 24篇 |
1980年 | 30篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 63篇 |
1976年 | 171篇 |
1975年 | 9篇 |
排序方式: 共有7932条查询结果,搜索用时 15 毫秒
961.
成对电离室相对中子灵敏度的确定及在(n,γ)混合场中吸收剂量的测定 总被引:1,自引:0,他引:1
本文对用铅减弱法测 k_u 的历史情况作了简短回顾,并介绍了处理铅减弱法实验数据的方法。在由 Sames 静电加速器上 T(d,n)~4He 反应产生的(n,γ)混合场中,用铅减弱法对自己设计制作的平行板流气电离室(TE-TE,Mg-Ar 和 Al-Ar)作了测量。由计算给出了组织等效电离室的 k_T值,且确定出:k_U(Mg-Ar)=0.193±0.010及 k_U(Al-Ar)=0.160 0.011。同时,对窄束、宽束(n,γ)混合场相应的中子、γ组分的吸收剂量作了测定。 相似文献
962.
RY Lin AE Rappoport LM Deppisch NS Natividad W Katz 《Canadian Metallurgical Quarterly》1977,118(6):1066-1067
The third documented case of primary squamous cell carcinoma of the urachus in the English literature is reported. The interesting coincidental occurrence of the dermoid cyst of the right ovary and a complete longitudinal septum of the vagina and uterine cervix is described. 相似文献
963.
964.
965.
If one listens to a meaningless syllable that is repeated over and over, he will hear it undergo a variety of changes that can be described systematically in terms of reorganization of the phones constituting the syllable and changes in a restricted set of phonetic distinctive features. When the repeated syllable is followed by a different syllable but in the same voice, the new (test) syllable will be misperceived in a manner related to the perceptual misrepresentation of the repeated syllable. In the present experiment subjects (N = 24) listened to 72 different experimental sequences of repeated syllables in a male voice followed by test syllables in a female voice. Identification of penultimate and test syllables was independent and in no instance were the phone constituting the syllables reorganized. These results are interpreted as evidence against both auditory and phonetic feature detector theories of speech perception. 相似文献
966.
The results of a two-year study on durability and cause of failure of electromyographic monopolar electrodes are reported. The electrodes were obtained from the regular stock of three different manufacturing sources. Durability is defined on the basis of the number of patients that could be examined before failure. The range was 3 to 110 with the averages 19.7, 33.8, and 62.5 for the three different manufacturers. Common causes of electrode failure included: Teflon retraction, 40.6%; tip dullness or burrs, 34.8%; structural failure of wire or pin, 13.1%; electrical artifacts, 9.7%; and bending of needle shank, 5.7%. Variations in manufactures' tip contour and bevel correlated with tip durability. 相似文献
967.
LM Silver 《Canadian Metallurgical Quarterly》1993,9(7):250-254
Mouse t haplotypes are descendents of a variant form of chromosome 17 that evolved the ability to propagate itself at the expense of the wild-type homolog from heterozygous +/t males. Although once enigmatic, these widespread selfish chromosomes have revealed many of their secrets in response to a combined assault with molecular, genetic and phylogenetic techniques. This review summarizes the current understanding of t haplotypes and their raison d'être. 相似文献
968.
969.
970.
J. P. Das et al (see record 1975-08765-001) claim that A. R. Luria's (1966) distinction between simultaneous and successive modes of information processing provides a more fruitful way of classifying cognitive processes than (a) the hierarchical models of C. Burt (see record 1973-10531-001) and P. E. Vernon (see record 1963-03855-001), A. R. Jensen's (see record 1969-09740-001) Levels 1 and 2, or A. Paivio's (see record 1976-01839-001) dual coding system of imagery and verbal mediation. Their published factor analyses are surveyed, and shown to yield only partial support for their views. A broader battery of 14 tests was given to 91 university students, and responses were factor analyzed. Two of the obtained factors involved various kinds of rote memorizing, and thus could be regarded as successive processing. Four other factors did not yield a general simultaneous factor, but classified the tests under Number-Spatial, Verbal-Spatial, Perceptual Reasoning, and a specific Digit Memory factor. Overall, the 6 factors tend to follow a multiple-factor, or a hierarchical model, rather than a dichotomous classification. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献