全文获取类型
收费全文 | 976篇 |
免费 | 2篇 |
专业分类
电工技术 | 1篇 |
综合类 | 3篇 |
化学工业 | 14篇 |
金属工艺 | 4篇 |
机械仪表 | 3篇 |
建筑科学 | 2篇 |
能源动力 | 6篇 |
轻工业 | 12篇 |
水利工程 | 1篇 |
无线电 | 14篇 |
一般工业技术 | 5篇 |
冶金工业 | 909篇 |
自动化技术 | 4篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2015年 | 1篇 |
2013年 | 7篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 3篇 |
1999年 | 17篇 |
1998年 | 259篇 |
1997年 | 158篇 |
1996年 | 105篇 |
1995年 | 72篇 |
1994年 | 58篇 |
1993年 | 51篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1978年 | 1篇 |
1977年 | 36篇 |
1976年 | 76篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有978条查询结果,搜索用时 15 毫秒
51.
Some 114 patients (median age 52 years) underwent laparoscopic hernia repair as a day-case procedure. Twenty-one patients had bilateral and 11 recurrent hernias. Some 113 patients underwent transabdominal preperitoneal mesh repair but one required conversion to open operation. Mean operating time was 24 min for unilateral and 38 min for bilateral repair. In an operating session of 3.5 h, up to five patients (mean 4.4) underwent surgery and as many as seven hernias were repaired. More than 10 per cent of patients were found to have a previously undiagnosed hernia on the opposite side. A total of 111 patients were discharged home on the day of surgery. Major complications included one omental bleed and one small bowel obstruction. Seroma was the commonest minor complication and occurred in 7 per cent of patients. More than 35 per cent of patients needed no postoperative analgesia. To date there has been one recurrence (follow-up range 2-18 months). 相似文献
52.
IM Robbins EV Colvin TP Doyle WE Kemp JE Loyd WS McMahon GN Kay 《Canadian Metallurgical Quarterly》1998,98(17):1769-1775
BACKGROUND: This report describes the complication of pulmonary vein stenosis with resultant severe pulmonary hypertension that developed in 2 patients after successful catheter ablation of chronic atrial fibrillation. METHODS AND RESULTS: Three months after successful catheter ablation of atrial fibrillation, both patients developed progressive dyspnea and pulmonary hypertension. Both were found to have severe stenosis of all 4 pulmonary veins near the junction with the left atrium. Balloon dilation of the stenotic pulmonary veins was performed in these patients, with improvement in dyspnea and pulmonary hypertension. CONCLUSIONS: The complication of pulmonary vein stenosis is potentially life-threatening, and the application of radiofrequency current within the pulmonary veins with standard catheter technology should be avoided. This complication can be treated with balloon dilation, although the long-term course is unknown. 相似文献
53.
Qualitative and quantitative characteristics of chronic pain syndrome and their possible use in assessing analgetic effects of treatment were studied in 16, 49, 26 and 17 patients with gastric ulcer, duodenal ulcer, chronic pancreatitis, chronic colitis, respectively. Pain was measured with the use of McHill's questionnaire modification and visual-verbal-analog scale. In addition to routine analysis of the data from the respondents, graphic mean profiles of pain for each group have been devised. There were differences in quantitative parameters of pain syndrome depending on nosological unity and profiles of patients. The questionnaire proved rather informative in evaluation and gradation of analgetic effects of therapeutic factors in ulcer patients. 相似文献
54.
It is known that drugs are not unlimitedly stable. Dilutions of the antineoplastic agent daunoblastin used in the clinic and experimental work, were examined, whether they could be stored for several days. By means of impulscytophotometry, spectral-photometric measurements, counting of surviving cells and estimation of DNA-synthesis after culturing pieces of tissue in the presence of daunoblastin it could be established that this drug, diluted even four days ago, still possesses sufficient activity. 相似文献
55.
56.
A preview tracking task has been developed which has particular application to neurological assessment and rehabilitation. Generated and monitored by a graphic display computer, it permits accurate global quantification of the upper-limb sensory-motor system. The incorporation of 'preview' into the tracking task is considered to significantly increase its effectiveness and relevance in relation to normal daily activities. Applied to three groups of normal subjects, several features of normal psychomotor performance and learning were identified or verified: hand dominance is not significant in overall arm control; learning does not completely plateau; increase in age (15-59 years) results in only a minor overall decrement in performance; an initial wide performance distribution decreases dramatically in subsequent sessions. Applied to brain-damaged patients, particularly head injury or stroke, the preview tracking task allows assessment at regular intervals enabling sensory-motor recovery curves to be generated. The potential of this technique, to help determine the efficacy of therapeutic procedures on the recovery process, is illustrated with the presentation of results from three brain-damaged patients demonstrating zero, significant and disjointed recovery of sensory-motor function. The usefulness of the preview tracking task can be expanded by combination with a less frequently applied but more component specific neurological assessment battery. 相似文献
57.
水解淫羊藿苷糖基的土壤细菌筛选 总被引:1,自引:0,他引:1
从20种土壤细菌中筛选出了对淫羊藿苷水解能力高的菌株Rhodanobncter sp.GS3054.该菌株30℃下发酵3~4d的发酵液提酶后对淫羊藿苷水解能力最佳;水解淫养藿苷成低糖基苷的最适反应条件为:50℃、pH6.0、底物20mg/mL,反应时间24h. 相似文献
58.
Kil-Sung LEE Hyeon-Kyeong SEO Yong-June YANG Woo-Chae HWANG Kwang-Hee IM In-Young YANG 《中国有色金属学会会刊》2011,(Z1):135-140
The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is rep... 相似文献
59.
Coherent detection of HIPERLAN Gaussian minimum-shift keying signals calls for complex and expensive receivers. However, when the channel delay spread is limited to at the most 50% of the symbol time and a reliable line-of-sight component of the radiated signal exists (Rician fading model), noncoherent detectors are capable of achieving a good performance. Based on the above motivations, we compare four different demodulation techniques, namely the following: (1) one-bit differential detector; (2) discriminator detector; (3) limiter discriminator detector; and (4) limiter discriminator integrator detector (LDID). The intersymbol interference introduced by these demodulators is nonlinear (with respect to the data symbols) and a decision-feedback equalizer (DFE) based on a mean square-error criterion may not be appropriate. Moreover, at this high speed, a DFE may be very complex to implement. Hence, we propose a new DFE design method that increases the eye-diagram aperture by removing the worst case interference. Performance of the above demodulators in the presence of a simple nonlinear DFE (with feedback part only) is computed in terms of the bit-error rate (BER) by means of the saddle-point approximation. This procedure, for static channels, turns out to be a very general tool with a simple and robust implementation. The same method can be applied, for multipath fading channels, to the BER evaluation as part of a semianalytic approach. The main conclusion from this work is that for LDID demodulators and in the presence of Rician fading channels with an average normalized root mean square delay spread of 0.3 and dual antenna diversity, the new equalizer lowers the outage probability from 60% to 10% at a BER of 10-4 相似文献
60.
AM Castellino P Cantalupo IM Marks JV Vartikar KW Peden JM Pipas 《Canadian Metallurgical Quarterly》1997,71(10):7549-7559
Simian virus 40 (SV40) DNA replication requires the coordinated action of multiple biochemical activities intrinsic to the virus-encoded large tumor antigen (T antigen). We report the preliminary biochemical characterization of the T antigens encoded by three SV40 mutants, 5030, 5031, and 5061, each of which have altered residues within or near the ATP binding pocket. All three mutants are defective for viral DNA replication in cultured cell lines. However, while 5030 and 5031 can be complemented in vivo by providing a wild-type T antigen in trans, 5061 exhibits a strong trans-dominant-negative phenotype. In order to determine the basis for their replication defects and to explore the mechanisms of trans dominance, we purified the T antigens encoded by each of these mutants and examined their activities in vitro. The 5061 T antigen had no measurable ATPase activity and failed to hexamerize in response to ATP, and its affinity for the SV40 origin of DNA replication (ori) DNA was not increased by ATP. In contrast, the 5030 and 5031 T antigens exhibited at least some ATPase activity and both readily formed hexamers in the presence of ATP. These mutants differed in that 5030 was very defective in an ori-dependent unwinding assay while 5031 retained significant activity. Both the 5030 and 5031 T antigens bound to ori-containing DNA, but the binding was less efficient than that of wild-type T antigen and was not affected by the presence of ATP. These results suggest that 5030 and 5031 are defective in some aspect of communication between the ATP binding and DNA binding domains and that the ability of ATP to induce T-antigen hexamerization is distinct from its action to increase the affinity for ori. Finally, all three mutants were defective for the ability to support SV40 DNA replication in vitro. Both the 5031 and 5061 T antigens inhibited wild-type-T-antigen-stimulated replication in vitro, while the 5030 T antigen did not. The fact that the 5031 T antigen was trans dominant in the in vitro assays but not in vivo indicates that the in vitro system does not accurately reflect events occurring in vivo. 相似文献