全文获取类型
收费全文 | 408153篇 |
免费 | 4805篇 |
国内免费 | 1377篇 |
专业分类
电工技术 | 7628篇 |
综合类 | 318篇 |
化学工业 | 60473篇 |
金属工艺 | 16477篇 |
机械仪表 | 13572篇 |
建筑科学 | 8533篇 |
矿业工程 | 2163篇 |
能源动力 | 11656篇 |
轻工业 | 28852篇 |
水利工程 | 4291篇 |
石油天然气 | 7928篇 |
武器工业 | 17篇 |
无线电 | 49691篇 |
一般工业技术 | 83471篇 |
冶金工业 | 76442篇 |
原子能技术 | 9235篇 |
自动化技术 | 33588篇 |
出版年
2022年 | 2574篇 |
2021年 | 3938篇 |
2020年 | 2974篇 |
2019年 | 3859篇 |
2018年 | 6542篇 |
2017年 | 6535篇 |
2016年 | 6988篇 |
2015年 | 4362篇 |
2014年 | 7200篇 |
2013年 | 20272篇 |
2012年 | 11515篇 |
2011年 | 15398篇 |
2010年 | 12271篇 |
2009年 | 13821篇 |
2008年 | 14183篇 |
2007年 | 13951篇 |
2006年 | 12545篇 |
2005年 | 11207篇 |
2004年 | 10588篇 |
2003年 | 10514篇 |
2002年 | 9902篇 |
2001年 | 9823篇 |
2000年 | 9216篇 |
1999年 | 9622篇 |
1998年 | 24696篇 |
1997年 | 16943篇 |
1996年 | 12972篇 |
1995年 | 9623篇 |
1994年 | 8478篇 |
1993年 | 8522篇 |
1992年 | 6102篇 |
1991年 | 5746篇 |
1990年 | 5745篇 |
1989年 | 5380篇 |
1988年 | 5116篇 |
1987年 | 4482篇 |
1986年 | 4341篇 |
1985年 | 4874篇 |
1984年 | 4460篇 |
1983年 | 4037篇 |
1982年 | 3703篇 |
1981年 | 3777篇 |
1980年 | 3482篇 |
1979年 | 3370篇 |
1978年 | 3372篇 |
1977年 | 3810篇 |
1976年 | 4945篇 |
1975年 | 2894篇 |
1974年 | 2693篇 |
1973年 | 2756篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
Docherty Nancy M.; Cohen Alex S.; Nienow Tasha M.; Dinzeo Thomas J.; Dangelmaier Ruth E. 《Canadian Metallurgical Quarterly》2003,112(3):469
This study examined the degree to which different types of communication disturbances in the speech of 48 schizophrenia patients and 28 controls were variable and state related versus stable and traitlike. Clinically rated formal thought disorder and 5 types of referential disturbance showed substantial stability within participants over time. The sixth type of referential disturbance, the vague reference, was not stable over time. Formal thought disorder was associated with the severity of core psychotic symptoms in patients, whereas referential disturbances showed little or no association with positive or negative symptom severity. Furthermore, changes in psychotic symptoms over time were accompanied by corresponding changes in formal thought disorder but not referential disturbances. These results support the idea that some types of referential disturbances are traitlike and may be reflective of vulnerability as well as manifest illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
953.
954.
Mazzocco Michèle M. M.; Freund Lisa S.; Baumgardner Thomas L.; Forman Lisa; Reiss Allan L. 《Canadian Metallurgical Quarterly》1995,9(4):470
An extensive evaluation was conducted with 16-yr-old monozygotic twins concordant for the fragile X full mutation but discordant for mental retardation. The clearly affected twin had an IQ score of 47; 77% of her neuropsychological z scores were at least 2 SDs below average. Her sister had an IQ score of 105 and average neuropsychological performance. However, each girl demonstrated relative verbal strengths and visual-spatial weaknesses. Their parents rated each girl as having significant problems with attention, conduct, anxiety-withdrawal, and hyperactivity. The girls did not rate themselves as having significant anxiety. These findings are consistent with group data on females with fragile X and demonstrate the wide range of effects associated with the fragile X full mutation. This case report implicates the importance of a psychosocial phenotype of fragile X independent of cognitive ability level. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
955.
J Macas J Dolezel G Gualberti U Pich I Schubert S Lucretti 《Canadian Metallurgical Quarterly》1995,19(3):402-4; 407-8
A protocol for primed in situ DNA labeling (PRINS) was optimized for pea (Pisum sativum L.) and field bean (Vicia faba L.) chromosomes attached to coverslips. Cloned DNA or synthetic oligonucleotides were used as probes for repetitive DNA sequences (rDNA, Fok-element) and different reaction conditions were tested to achieve the highest specific signal-to-background ratio. A procedure based on direct labeling by fluorescein-dUTP was compared with an indirect one using digoxigenin detected by fluorescently labeled antibody. Under optimal conditions, strong and specific signals were obtained exclusively on chromosome regions known to contain respective DNA sequences. Compared to the direct labeling, significantly stronger signals were obtained when the indirect procedure was used. Both types of labeling were successfully applied to chromosomes in suspension and were shown to produce signals comparable to that obtained with chromosomes attached to coverslips. It is expected that primed in situ DNA labeling en suspension (PRINSES) will provide a basis for flow-cytometric discrimination and sorting of otherwise indistinguishable chromosomes according to their specific fluorescent labeling. 相似文献
956.
A. S. Fouda A. A. Elshafei A. H. Elasklany L. H. Madkour 《Materialwissenschaft und Werkstofftechnik》1995,26(6):342-346
The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicarbazide and sym.diphenylcarbazide as corrosion inhibitors has been studied using thermometric, weight-loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive. The adsorption of these compounds were found to obey Frumkin adsorption isotherm. Cathodic polarization measurements showed that these compounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption. 相似文献
957.
Yan R.-H. Lee K.F. Jeon D.Y. Kim Y.O. Park B.G. Pinto M.R. Rafferty C.S. Tennant D.M. Westerwick E.H. Chin G.M. Morris M.D. Early K. Mulgrew P. Mansfield W.M. Watts R.K. Voshchenkov A.M. Bokor J. Swartz R.G. Ourmazd A. 《Electron Device Letters, IEEE》1992,13(5):256-258
The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region 相似文献
958.
Ahluwalia Jasjit S.; Nollen Nicole; Kaur Harsohena; James Aimee S.; Mayo Matthew S.; Resnicow Ken 《Canadian Metallurgical Quarterly》2007,26(2):214
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
959.
960.