全文获取类型
收费全文 | 16812篇 |
免费 | 234篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 186篇 |
综合类 | 4篇 |
化学工业 | 1989篇 |
金属工艺 | 361篇 |
机械仪表 | 338篇 |
建筑科学 | 512篇 |
矿业工程 | 60篇 |
能源动力 | 306篇 |
轻工业 | 1216篇 |
水利工程 | 89篇 |
石油天然气 | 118篇 |
无线电 | 1512篇 |
一般工业技术 | 2348篇 |
冶金工业 | 6474篇 |
原子能技术 | 159篇 |
自动化技术 | 1396篇 |
出版年
2021年 | 97篇 |
2019年 | 102篇 |
2018年 | 135篇 |
2017年 | 101篇 |
2016年 | 94篇 |
2015年 | 107篇 |
2014年 | 224篇 |
2013年 | 569篇 |
2012年 | 304篇 |
2011年 | 406篇 |
2010年 | 333篇 |
2009年 | 337篇 |
2008年 | 450篇 |
2007年 | 439篇 |
2006年 | 432篇 |
2005年 | 386篇 |
2004年 | 323篇 |
2003年 | 361篇 |
2002年 | 308篇 |
2001年 | 321篇 |
2000年 | 315篇 |
1999年 | 436篇 |
1998年 | 1838篇 |
1997年 | 1121篇 |
1996年 | 816篇 |
1995年 | 529篇 |
1994年 | 464篇 |
1993年 | 508篇 |
1992年 | 293篇 |
1991年 | 263篇 |
1990年 | 272篇 |
1989年 | 248篇 |
1988年 | 239篇 |
1987年 | 225篇 |
1986年 | 210篇 |
1985年 | 267篇 |
1984年 | 208篇 |
1983年 | 207篇 |
1982年 | 213篇 |
1981年 | 189篇 |
1980年 | 206篇 |
1979年 | 128篇 |
1978年 | 138篇 |
1977年 | 293篇 |
1976年 | 433篇 |
1975年 | 138篇 |
1974年 | 127篇 |
1973年 | 108篇 |
1972年 | 78篇 |
1970年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 601 毫秒
41.
We could not imagine a more appropriate inauguration of the Psychology of Aesthetics, Creativity, and the Arts (PACA) going to four issues per year than with a special issue honoring the life and work of the great aesthetician and psychologist, Rudolf Arnheim. PACA is off to a great start. With this move to four issues per year, we are restarting our numbering system, so this special issue is Volume 1, Issue 1. As you read the articles in this issue, we hope that you enjoy reflecting on how much Rudolf Arnheim has contributed to the field of psychology of aesthetics. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
Chwen-Jyh Jeng Warren B. Kindzierski Daniel W. Smith 《Canadian Metallurgical Quarterly》2007,133(3):331-339
This paper presents a particle penetration model predicting particle penetration coefficient (Pp) through a narrow crack of arbitrary incline angles (θ). The objective was to simulate Pp for outdoor-to-indoor particle penetration for residential infiltration conditions. This model assumes laminar infiltration flow and considers particle deposition from both gravitational sedimentation and Brownian diffusion. For micron-sized particles, modeling results indicate that gravitational sedimentation is the major deposition mechanism. Pp increases monotonically with ∣θ∣ because effective particle sedimentation velocity (vs?cos?θ) decreases monotonically with ∣θ∣. For submicron-sized particles (0.1?μm), Brownian diffusion is the major particle deposition mechanism. Because Brownian diffusion is a nondirectional deposition mechanism, crack inclination did not affect Pp. This study applied this model to estimate Pp for L-shaped cracks, and validated modeling results with experiments. Experimental results indicated that inertial impaction and crack entrance cutoff effects were not significant particle deposition mechanisms for the test micron-sized particles. Gravitational sedimentation was the major deposition mechanism. An L-shaped crack can be simulated as the combination of horizontal and vertical sections. This model agreed reasonably with experimental results. 相似文献
43.
44.
Canham R.O. Smith S.L. Tyrrell A.M. 《Vision, Image and Signal Processing, IEE Proceedings -》2005,152(6):741-749
Complex and highly distorted line drawings are produced by subjects attempting the Rey Complex Figure test, a clinical test of neuropsychological assessment. However, the marking scheme conventionally employed can be subjective and unreliable. In this paper, the first stages in automating this scoring system are investigated using a robust technique to locate a reduced set of scoring sections and a knowledge-based system that employs spatial metrics and fuzzy approximation techniques. Testing the technique using clinical data produced encouraging results that support the argument that this is a feasible approach for implementing a fully automated system, and that in its current state, can be immediately applied in a semi-automated system. 相似文献
45.
PJ Jenkins MA Satta M Simmgen WM Drake C Williamson DG Lowe K Britton SL Chew RV Thakker GM Besser 《Canadian Metallurgical Quarterly》1997,47(6):747-751
We report a patient with a metastatic parathyroid carcinoma and medullary carcinoma of the thyroid. This patient represents a variation of the multiple endocrine neoplasia syndrome (MEN) type 2A. There was no evidence of a phaeochromocytoma. The case illustrates the difficulties that may be encountered in localising the source of PTH secretion; the patient underwent four unsuccessful exploratory operations of the neck and mediastinum before further investigations revealed a single metastatic deposit of parathyroid carcinoma involving the first thoracic vertebra. PCR amplification and sequencing of the RET oncogene from the metastatic parathyroid carcinoma and genomic DNA revealed a heterozygous mutation (Cys634Tyr) in exon 11, as has previously been described to occur in MEN 2A. In addition, loss of tumour heterozygosity was demonstrated at loci from chromosomes 1, 2, 3p, 13q and 16p. This represents the first report of a parathyroid carcinoma in a MEN2A patient, in which the multiple allelic deletions are consistent with the generalised losses observed in aggressive tumours. 相似文献
46.
47.
A Notghi R Hutchinson D Kumar NB Smith LK Harding 《Canadian Metallurgical Quarterly》1994,35(7):976-981
Segmental colonic transit has been measured in 101 patients. Two MBq of 111Indium absorbed on resin pellets and encapsulated in an enteric coated capsule was given at 7 00 am. Hourly images during the first day, and three images during each subsequent day were acquired for up to three days. Using all scan and patient data the scans were categorised in one of the five patterns of colonic transit: normal, rapid, right delay, left delay, or generalised delay. The geometric centres and per cent activity at each time point was compared between the five groups of colonic transit patients to find the best time for imaging and so to distinguish the five groups. During the first day, early images did not help in diagnosis of patterns of transit, however, in the later images (six hours onwards after the ingestion of the activity) the rapid transit groups could be identified. Images at 27 and 51 hours were both required to distinguish all five groups of patients from each other. Only in the 'normal' transit patients was there some excretion of the activity during the course of the second day, otherwise there was no difference in the images taken in the course of a day (second or third day). A simplified protocol requires a minimum of three images to distinguish all five patterns of colonic transit. The activity should be ingested in the morning (7 00 am) and the first image taken at the end of the working day (8-10 hours after ingestion), the second image on the morning of the second day, and the third image during the course of the third day. This simple protocol would provide all the clinically relevant information necessary for correct classification of the colonic transit. 相似文献
48.
J Smith 《Canadian Metallurgical Quarterly》1993,306(6891):1524-1526
49.
50.
The iron status of 22 children and adolescents with Crohn's disease (mean age: 13 years) was evaluated. Eleven patients were suffering from active disease with inflammation, identified by at least one abnormal value for serum orosomucoid, C-reactive protein or sedimentation rate (group I). Eleven patients were in clinical remission and showed no biological evidence of inflammation (group II). Hemoglobin and red cell indices, erythrocyte protoporphyrin, serum iron, transferrin, serum ferritin and basic red cell ferritin were determined in all patients. The usual indicators of iron status, particularly serum ferritin, were affected by the inflammatory processes, but basic red cell ferritin appeared to be independent of inflammation. Basic red cell ferritin can therefore be considered to be a reliable indicator of iron status in children and adolescents with Crohn's disease. 相似文献