全文获取类型
收费全文 | 9812篇 |
免费 | 497篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 100篇 |
综合类 | 4篇 |
化学工业 | 1954篇 |
金属工艺 | 145篇 |
机械仪表 | 194篇 |
建筑科学 | 631篇 |
矿业工程 | 24篇 |
能源动力 | 320篇 |
轻工业 | 904篇 |
水利工程 | 110篇 |
石油天然气 | 27篇 |
无线电 | 709篇 |
一般工业技术 | 1976篇 |
冶金工业 | 1390篇 |
原子能技术 | 37篇 |
自动化技术 | 1804篇 |
出版年
2023年 | 64篇 |
2022年 | 104篇 |
2021年 | 216篇 |
2020年 | 176篇 |
2019年 | 213篇 |
2018年 | 233篇 |
2017年 | 235篇 |
2016年 | 260篇 |
2015年 | 231篇 |
2014年 | 341篇 |
2013年 | 673篇 |
2012年 | 558篇 |
2011年 | 793篇 |
2010年 | 512篇 |
2009年 | 478篇 |
2008年 | 593篇 |
2007年 | 518篇 |
2006年 | 440篇 |
2005年 | 391篇 |
2004年 | 333篇 |
2003年 | 308篇 |
2002年 | 287篇 |
2001年 | 155篇 |
2000年 | 161篇 |
1999年 | 141篇 |
1998年 | 165篇 |
1997年 | 161篇 |
1996年 | 156篇 |
1995年 | 127篇 |
1994年 | 103篇 |
1993年 | 97篇 |
1992年 | 83篇 |
1991年 | 64篇 |
1990年 | 78篇 |
1989年 | 65篇 |
1988年 | 45篇 |
1987年 | 67篇 |
1986年 | 56篇 |
1985年 | 59篇 |
1984年 | 56篇 |
1983年 | 74篇 |
1982年 | 54篇 |
1981年 | 45篇 |
1980年 | 39篇 |
1979年 | 43篇 |
1978年 | 32篇 |
1977年 | 33篇 |
1976年 | 38篇 |
1975年 | 25篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
To examine the separate effects of viscosity and sweetness on astringency, aqueous solutions of grape seed tannin (GST) were thickened with carboxymethyl cellulose (CMC) from 2 to 45 cP (experiment 1) or sweetened with 0 to 1.8 g/L aspartame (experiment 2). Trained subjects continuously rated astringency and bitterness in duplicate. Subjects were categorized by the salivary flow induced by citric acid and ability to taste n-propyl thiouracil (PROP). In experiment 1, maximum intensity and total duration of astringency were significantly decreased as viscosity rose, although time to maximum intensity of astringency was not affected. Maximum intensity and total duration of bitterness were not significantly affected by increasing viscosity; however, the onset of bitterness was significantly delayed. In experiment 2, increasing sweetness had no affect on any astringency parameter, although maximum intensity of bitterness was significantly decreased. Neither PROP nor salivary flow-status had any effect on perception of bitterness or astringency in either experiment. 相似文献
42.
Assembly of the higher-order structure of mitotic chromosomes is a prerequisite for proper chromosome condensation, segregation and integrity. Understanding the details of this process has been limited because very few proteins involved in the assembly of chromosome structure have been discovered. Using a human autoimmune scleroderma serum that identifies a chromosomal protein in human cells and Drosophila embryos, we cloned the corresponding Drosophila gene that encodes the homologue of vertebrate titin based on protein size, sequence similarity, developmental expression and subcellular localization. Titin is a giant sarcomeric protein responsible for the elasticity of striated muscle that may also function as a molecular scaffold for myofibrillar assembly. Molecular analysis and immunostaining with antibodies to multiple titin epitopes indicates that the chromosomal and muscle forms of titin may vary in their NH2 termini. The identification of titin as a chromosomal component provides a molecular basis for chromosome structure and elasticity. 相似文献
43.
Prednisolone therapy of idiopathic feline lower urinary tract disease: a double-blind clinical study
CA Osborne JM Kruger JP Lulich GR Johnston DJ Polzin LK Ulrich J Sanna 《Canadian Metallurgical Quarterly》1996,26(3):563-569
A double-blind clinical study was performed to evaluate prednisolone as treatment for idiopathic feline lower urinary tract disease. No differences in response were observed in prednisolone- and placebo-treated cats. 相似文献
44.
PURPOSE: To assess the clinical performance of 2-year old gallium alloy restorations. Parameters evaluated include: (1) fracture at the margins, (2) tarnish, (3) surface roughness, (4) tooth fracture, (5) fracture through the body of the restoration, and (6) any medical or dental conditions arising during the study. MATERIALS AND METHODS: Nine patients received 30 Class I restorations of Galloy gallium alloy. These were placed as conservatively as possible under a rubber dam. Fifteen of the preparations were lined with a Bis-GMA resin to seal the restoration from moisture. The other 15 preparations were sealed with Amalgambond. After placement of the gallium alloy, the exposed surfaces of all restorations were sealed with the Bis-GMA resin, and the occlusion was checked. The restorations were examined at 2 weeks, 3 months, 6 months, 1 year and 2 years. RESULTS: At the 2-year recall, all restorations were intact with the exception of one tooth fracture (cause unknown). Forty-five percent of the restorations exhibited tarnish and 60% had a rough surface. The fracture at the margins of these restorations was minimal, and no significant difference could be found between those using Amalgambond and those sealed with the resin system. No medical problems were reported by the patients, and postoperative sensitivity was minimal. 相似文献
45.
Tomarken Andrew J.; Davidson Richard J.; Wheeler Robert E.; Doss Robert C. 《Canadian Metallurgical Quarterly》1992,62(4):676
Assessed whether individual differences in anterior brain asymmetry are linked to differences in basic dimensions of emotion. In each of 2 experimental sessions, separated by 3 wks, resting EEG activity was recorded from female adults during 8 60-sec baselines. Mean alpha power asymmetry across both sessions was extracted in mid-frontal and anterior temporal sites. Across both regions, groups demonstrating stable and extreme relative left anterior activation reported increased generalized positive affect (PAF) and decreased generalized negative affect (NAF) compared with groups demonstrating stable and extreme relative right anterior activation. Additional correlational analyses revealed robust relations between anterior asymmetry and PAF and NAF, particularly among Ss who demonstrated stable patterns of EEG activation over time. Anterior asymmetry was unrelated to individual differences in generalized reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Domjan Michael; Mahometa Michael J.; Mills Andrew D. 《Canadian Metallurgical Quarterly》2003,117(4):391
Two contrasting investigative techniques provided evidence consistent with the interpretation that female quail (Coturnix japonica) regulate male copulatory behavior by the duration of their immobility and through this behavioral mechanism they also control the rate of fertilization of their eggs. In Experiment 1, copulation tests with males and females from different genetic lines showed that the type of female that participated in a copulatory test significantly influenced the latency of the male's grab, mount, and cloacal contact responses and also determined the efficiency of the male's copulatory behavior. These measures of male performance were correlated with female immobility in Experiment 2, which used a more homogeneous population of quail. Furthermore, 2 of these measures (copulatory efficiency and the latency to make cloacal contact) were correlated with fertilization rate. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Marcela Brugnach Andrew Tagg Florian Keil Wim J. de Lange 《Water Resources Management》2007,21(7):1075-1090
The use of computer models offers a general and flexible framework that can help to deal with some of the complexities and
difficulties associated with the development of water management plans as prescribed by the Water Framework Directive. However,
despite the advantages modelling presents, the integration of information derived from models into policy is far away from
being trivial or the norm. Part of the difficulties of this integration is rooted in the lack of confidence policy makers
have on the incorporation of modelling information into policy formulation. In this paper we examine the reasons for this
apparent lack of confidence and explore how some tools, presently in use, address this problem. We conclude that public confidence
in models is highly dependent on the way uncertainties are addressed and suggest possible directions of action to improve
the current situation. Four real case studies illustrate how computer models have been used in The Netherlands for carrying
out management plans at regional and national scale. We suggest that the solution to integrate modelling information into
policy formulation lies on both the modelling and the policy-making communities. 相似文献
48.
The group scanning model of feature integration theory suggests that Ss search visual displays serially by groups, but process items within each group in parallel. Group size is determined by the discriminability of the targets in the background of distractors. When the target is poorly discriminable, the size of the scanned group will be small, and search will be slow. The model predicts that group size will be smallest when targets of an intermediate value on a perceptual dimension are presented in a heterogeneous background of distractors that have higher and lower values on the same dimension. Experiment 1 (30 Ss) demonstrates this effect; Exp 2 (12 Ss) controls for a possible confound of decision complexity in Exp 1. For simple feature targets, the group scanning model provides a good account of the visual search process. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
Assessed whether resting anterior asymmetry would discriminate individual differences in repressive-defensive coping styles. In 2 sessions, resting electroencephalogram was recorded from female adults during 8 60-sec baselines. Ss were classified as repressors or nonrepressors on the basis of scores on the Marlowe-Crowne Social Desirability Scale (MC), the State-Trait Anxiety Inventory (STAI), and the Beck Depression Inventory (BDI). In midfrontal and lateral frontal sites, repressors demonstrated relative left hemisphere activation when compared with other groups. The MC, but not the STAI or the BDI, contributed unique variance to frontal asymmetry. Relative left frontal activation may be linked to a self-enhancing regulatory style that promotes lowered risk for psychopathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Andrew Klapper 《Journal of Cryptology》1994,7(1):33-51
A new method of cryptologic attack on binary sequences is given, using their linear complexities relative to odd prime numbers. We show that, relative to a particular prime number p, the linear complexity of a binary geometric sequence is low. It is also shown that the prime p can be determined with high probability by a randomized algorithm if a number of bits much smaller than the linear complexity is known. This determination is made by exploiting the imbalance in the number of zeros and ones in the sequences in question, and uses a new statistical measure, the partial imbalance.This project was sponsored by the National Security Agency under Grant No. MDA904-91-H-0012. The United States Government is authorized to reproduce and distribute reprints notwithstanding any copyright notation hereon. 相似文献