全文获取类型
收费全文 | 105136篇 |
免费 | 7573篇 |
国内免费 | 3018篇 |
专业分类
电工技术 | 4164篇 |
技术理论 | 10篇 |
综合类 | 4551篇 |
化学工业 | 19658篇 |
金属工艺 | 4227篇 |
机械仪表 | 4583篇 |
建筑科学 | 6525篇 |
矿业工程 | 1883篇 |
能源动力 | 2805篇 |
轻工业 | 12137篇 |
水利工程 | 1664篇 |
石油天然气 | 3810篇 |
武器工业 | 527篇 |
无线电 | 9735篇 |
一般工业技术 | 14291篇 |
冶金工业 | 10050篇 |
原子能技术 | 866篇 |
自动化技术 | 14241篇 |
出版年
2024年 | 395篇 |
2023年 | 1507篇 |
2022年 | 2763篇 |
2021年 | 3982篇 |
2020年 | 3069篇 |
2019年 | 2686篇 |
2018年 | 3591篇 |
2017年 | 3602篇 |
2016年 | 3623篇 |
2015年 | 3810篇 |
2014年 | 4779篇 |
2013年 | 6703篇 |
2012年 | 6563篇 |
2011年 | 6931篇 |
2010年 | 5634篇 |
2009年 | 5291篇 |
2008年 | 5260篇 |
2007年 | 4884篇 |
2006年 | 4319篇 |
2005年 | 3718篇 |
2004年 | 2909篇 |
2003年 | 2614篇 |
2002年 | 2375篇 |
2001年 | 2030篇 |
2000年 | 2109篇 |
1999年 | 2465篇 |
1998年 | 4073篇 |
1997年 | 2892篇 |
1996年 | 2333篇 |
1995年 | 1686篇 |
1994年 | 1423篇 |
1993年 | 1124篇 |
1992年 | 681篇 |
1991年 | 526篇 |
1990年 | 453篇 |
1989年 | 411篇 |
1988年 | 340篇 |
1987年 | 264篇 |
1986年 | 210篇 |
1985年 | 193篇 |
1984年 | 154篇 |
1983年 | 108篇 |
1982年 | 125篇 |
1981年 | 137篇 |
1980年 | 128篇 |
1979年 | 56篇 |
1978年 | 56篇 |
1977年 | 150篇 |
1976年 | 275篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
61.
I Hutás 《Canadian Metallurgical Quarterly》1996,137(12):619-622
The author expounds the fairly obscure history of BCG vaccination. Summarises the efficiency of accomplished vaccinations of different geographical areas. He accounts the diversity of results by the distinction of technical and methodical conditions and disparity in virulence of BCG strains. Overviews the Inland and European routine and the risk of possible complications. The favourable position of domestic childhood tuberculosis is due to the effective preventive arrangements. Considering the international and national epidemiology of tuberculosis in adults the administration of BCG vaccine, by chance in modified form, is recommended further on. 相似文献
62.
The results of study of the effects of yttria stabilization (0–6 mol.%) on the room-temperature fracture behavior and toughening mechanisms in zirconia-reinforced MoSi2 are presented in this paper. Transformation toughening is shown to occur only in composites reinforced with zirconia particles stabilized with 2 mol.% yttria. However, the fracture toughness levels are comparable in the other composites with yttria levels between 0 and 6 mol.%. Toughening in the other composites is attributed to the combined effects of residual stress, microcrack shielding/anti-shielding and/or crack deflection. A rigorous micromechanics-based model is presented for the estimation of residual stress levels in brittle materials reinforced with phases that can transform during cooling or under stress. The model is applied successfully to the rationalization of the observed fracture and toughening phenomena. 相似文献
63.
Subsequent to the implementation of a severity marker stamp in case notes, an audit was performed in 86 admissions with acute asthma to a specialist centre over a 12 month period. Compared to previous audit the documentation of severity markers was significantly better (PEFR: 52% vs 83% p = 0.001, Respiratory rate: 44% vs 81% p = 0.001, ABG: 72% vs 80% p = 0.04, air entry: 58% vs 86% p = 0.001, speech: 27% vs 86% p = 0.001, exhaustion: 4% vs 86% p = 0.001). In contrast to the previous audit where no patient received FiO2 > 0.35, 66% of the cases in the repeat audit received FiO2 0.60 (p = 0.001). The mean duration of admission was five days and showed highest partial correlation (r = 0.6) to the time in hours for the pulse to fall to 80/min. Multiple linear regression showed that this was the only variable best predicting the duration of admission (R2 = 0.3). Admission pulse rate (p = 0.04) and serum K+ (p = 0.04) best discriminated between patients admitted for over and under five days. Logistic regression identified only the admission pulse as significant in calculating the odds of the patient staying in the hospital for > 5 days. 相似文献
64.
65.
OBJECTIVE: Experiences obtained with nonoperative treatment (NOT), i.e. total prohibition of per oral food intake for a minimum of 7 days, administration of combinations of broad-spectrum antibiotics, and parenteral hyperalimentation, are described in the management of esophageal perforations. SUMMARY BACKGROUND DATA: The place, value, and indication of NOT in the management of esophageal perforation has not yet been unequivocally defined. As a result, contradictory data have been published regarding the outcome of NOT. METHODS: During the past 15 years (1979 to 1994), 20 of 86 patients (23.3%) with esophageal perforation have been treated nonoperatively from the outset. In this group, perforations were located to the upper, middle, and lower third of the esophagus in 50%, 30%, and 20%, respectively. In the operative management group (OT)--in which conservative (drainage, endeprothesis), reconstructive (suture, reinforced suture), and radical (resection) surgical methods were applied--lesions were preponderantly located in the lower one third of the esophagus (56.1%--37/66). As to the interval between the perforation and the onset of treatment, 14 patients had been diagnosed within 24 hours, whereas in 6 cases treatment had been begun beyond 24 hours. RESULTS: NOT could be successfully carried out in 16 patients; the decision to use NOT had to be revised in 4 other cases (Table 1). Two patients were lost; the mortality rate was 10% (2 of 20). The rate of complications was lower in the NOT group (20%, or 4 of 20) than in the OT group (50%, or 33 of 66). CONCLUSIONS: NOT can be suggested for the treatment of intramural perforations. In the case of transmural perforation, this approach should be taken into consideration if the esophageal lesion is circumscribed, is not in neoplastic tissue, is not in the abdominal cavity, and is not accompanied by simultaneous obstructive esophageal disease; in addition, symptoms and signs of septicemia should be absent. 相似文献
66.
A cryptic multidrug resistance (MDR) system in Stenotrophomonas maltophilia, the expression of which is selectable by tetracycline, is described. Tetracycline resistance was the consequence of active efflux of the antibiotic, and it was associated with resistance to quinolones and chloramphenicol, but not to aminoglycosides or beta-lactam antibiotics. MDR is linked to the expression of an outer membrane protein (OMP54) both in a model system and in multidrug-resistant clinical isolates. 相似文献
67.
JA Carballido Rodríguez 《Canadian Metallurgical Quarterly》1997,21(7):641-643
A case of a large dentigerous cyst containing a canine tooth in the maxillary antrum is presented. This case is of interest due because of its extensiveness and the presence of a canine tooth in the roof of the maxillary sinus. In addition, this caused a right-sided epiphora. Enucleation of the cyst containing the ectopic tooth was made. 相似文献
68.
A Serrano Pascual C Merino Hernáez R Ochoa Mejías A Escolano Chamois J Golbano Ablanque I Otero Tejero M Sanz Redondo F Román Ruiz 《Canadian Metallurgical Quarterly》1997,21(6):631-635
BACKGROUND AND AIMS OF THE STUDY: Surgical treatment of functional tricuspid regurgitation associated with advanced valvular disease remains controversial, mainly due to the difficulty in choosing between valve replacement or reconstructive surgery. Failure to correct tricuspid regurgitation during valvular surgery carries a poor prognosis, as reoperation may represent a significant risk to the patient. Thus correct tricuspid valve surgery is vital to achieve improved early and long-term clinical results. METHODS: A total of 142 patients underwent concomitant tricuspid annuloplasty with mitral valve replacement and their clinical outcome was assessed. RESULTS: Overall hospital mortality rate was 11.3%. Seven patients died during follow up. The overall actuarial survival rate for 10 years was 74.1 +/- 14.2%. Postoperatively, 75.8% of the patients had no residual tricuspid insufficiency, while 24.2% had first- or second-degree tricuspid insufficiency and were treated medically. All patients were in NHYA functional class I or II postoperatively. CONCLUSION: Clinically, it is important to assess the severity of functional tricuspid insufficiency before and/or during the operation. Bicuspidalization annuloplasty for functional tricuspid insufficiency has provided good results, with a low incidence of reoperation and significant clinical improvement. The technique could be used in most patients with functional tricuspid regurgitation. 相似文献
69.
M Beksa? MS Beksa? VB Tipi HA Duru MU Karakás AN Cakar 《Canadian Metallurgical Quarterly》1997,30(3):145-150
The endothelium participates actively in homeostatic mechanisms such as the regulation of vascular tone and maintenance of a nonthrombotic environment, as well as directing biological responses such as leukocyte trafficking to inflammatory sites. Disruption of these processes leads to disease. In the antiphospholipid antibody syndrome autoantibodies provoke the endothelium to develop a prothrombotic surface. In systemic vasculitides associated with presence of antineutrophil cytoplasm antibodies, it is likely that the autoantibodies incite premature neutrophil activation, disrupted neutrophil-endothelium interactions and endothelial damage. This review considers how normal endothelial functions may be subverted in disease and how active endothelial responses may contribute to disease. 相似文献
70.
The hypothesis of Geisler (Brain Res. 212 (1981) 198-201), in which the different spontaneous-rate classes of primary auditory neurons were accounted for by the different sizes of uniquantal EPSPs relative to the gap between resting membrane and threshold potentials, was represented with an expanded model which included relative refractory effects. The spike rates generated by the expanded model, when plotted vs. estimated sound level, are qualitatively similar to those of experimentally obtained rate-level curves. The hypothesis is also consistent with recent ultrastructural data which suggest that average quantal-release rates for any particular primary auditory neuron are inversely related to its spontaneous rate. The model's recovery processes following spike generation (hazard functions) are also similar to those observed experimentally. 相似文献