首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   350篇
  免费   1篇
化学工业   2篇
机械仪表   1篇
能源动力   5篇
轻工业   7篇
水利工程   2篇
无线电   1篇
一般工业技术   18篇
冶金工业   313篇
自动化技术   2篇
  2022年   1篇
  2021年   1篇
  2019年   2篇
  2016年   3篇
  2015年   1篇
  2014年   2篇
  2013年   6篇
  2012年   4篇
  2011年   3篇
  2010年   1篇
  2008年   1篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  1999年   3篇
  1998年   107篇
  1997年   56篇
  1996年   34篇
  1995年   30篇
  1994年   13篇
  1993年   13篇
  1992年   3篇
  1991年   3篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   5篇
  1980年   3篇
  1978年   3篇
  1977年   13篇
  1976年   22篇
  1975年   2篇
  1971年   1篇
  1954年   1篇
排序方式: 共有351条查询结果,搜索用时 125 毫秒
21.
BACKGROUND: The distinction between malignant mesothelioma (MM) and adenocarcinoma (ACA) in cytologic specimens frequently is difficult, often requiring immunocytochemistry to support the diagnosis. Recent reports have proposed the utilization of antibodies to mesothelial cell clone HBME-1 and thrombomodulin (TM), because they are immunoreactive in MM and less commonly reactive in ACA. Immunoreactivity for the monoclonal antibody CA 19-9 has been observed in many ACAs and reportedly is absent in MM. METHODS: In this study, immunostaining was performed on formalin fixed, paraffin embedded cell blocks from effusions or fine-needle aspirations using the avidin-biotin-peroxidase method. Thirty-eight MMs and 49 ACAs were tested using antibodies to CA 19-9, HBME-1, and TM. RESULTS: Anti-CA 19-9 stained only 1 of the 37 cases of MM tested (3%), but stained 24 of the 49 cases of ACA (49%). Anti-HBME-1 stained 34 of 38 cases of MM (89%), and 28 of 43 cases of ACA tested (65%). Anti-TM stained 24 of 36 cases of MM (67%), and 21 of 40 cases of ACA tested (53%). CONCLUSIONS: CA 19-9 has utility as part of an immunocytochemical panel for distinguishing ACA from MM, because a positive staining reaction would make the diagnosis of MM unlikely. Although HBME-1 and TM can identify MM positively, each frequently is detected in ACA, thus limiting the utility of these antibodies in cytologic specimens.  相似文献   
22.
BACKGROUND: Recently, endoaneurysomorrhaphy has been proposed as a more physiologic repair of postinfarction left ventricular aneurysm than is linear repair. There are only a few studies comparing the short-term and long-term results of the two techniques. METHODS: Clinical outcomes and echocardiographic measurements of left ventricular volume and sphericity in 27 patients who underwent endoaneurysmorrhaphy were compared with those in 20 patients who had linear repair. RESULTS: The two groups were matched with respect to age, gender, comorbid risk factors, functional class, urgency of the operation, and concomitant procedures. Preoperatively, left ventricular ejection fraction was lower in the endoaneurysmorrhaphy group (0.25 +/- 0.08 versus 0.30 +/- 0.09; p = 0.03). Follow-up was available in 44 patients (94%) and ranged from 2 to 86 months (mean, 41.0 +/- 26.5 months). Thirty-day operative mortality, perioperative complications, 5-year survival, and freedom from cardiac death were similar. Early postoperative percentage increase in left ventricular ejection fraction was greater after endoaneurysmorrhaphy (0.51 +/- 0.64 versus 0.18 +/- 0.48; p = 0.036). Long-term functional improvement was significantly better in the endoaneurysmorrhaphy group: At the time of last follow-up, 88% of patients were in New York Heart Association class I/II, compared with 53% after linear repair (p = 0.01). There were no measurable differences between the groups with respect to left ventricular ejection fraction (0.28 +/- 0.11 versus 0.27 +/- 0.11; p = 0.90), left ventricular volume (171.6 +/- 59.1 versus 169.9 +/- 54.4 mL; p = 0.94), and sphericity index (0.61 +/- 0.09 versus 0.61 +/- 0.12; p = 1.0). CONCLUSIONS: Despite having a similar effect on left ventricular geometry, endoaneurysmorrhaphy resulted in a greater increase in postoperative left ventricular ejection fraction and a substantially improved long-term clinical outcome.  相似文献   
23.
Seasonal fluctuations were studied in the incidence of characteristic abdominal fever symptoms, such as headache, insomnia, asthenia, skin pallor, roseolous eruptions, protracted fever, drop in blood pressure, relative bradycardia, dicrotia, typhoid tongue, enlargement of the liver and spleen, meteorism, constipation, palpable crepitation in the right iliac region, manifest leucopenia. Some symptoms occurred with almost equal frequency in different seasons of the year. In adults, severity of some typhoid symptoms was the greatest, duration the longest, degree the highest in spring, followed, in decreasing rank order by autumn > summer > winter; in children: spring > summer > autumn > winter.  相似文献   
24.
The Rieske protein II (Schmidt et al., 1996, FEBS Lett. 388, 43-46) from the thermoacidophilic crenarcheon Sulfolobus acidocaldarius (DSM 639) was expressed in E. coli cells. The full length protein was strictly bound to the E. coli membranes and could only be removed by detergent treatment indicating the presence of a membrane anchor. The iron sulfur cluster was correctly inserted into a fraction of the full length protein and much more effectively into a soluble form created by the deletion of the 45 N-terminal amino acids. The soluble form of the protein displayed the typical spectroscopic properties of a respiratory Rieske protein. The midpoint potential was +375 mV determined by CD redox potentiometry. The presented data demonstrate that the structure of the recombinant protein is very similar or identical to the authentic protein making this a powerful model system for the studies of Rieske proteins by site directed mutagenesis.  相似文献   
25.
26.
27.
The subperiosteal facelift is an excellent technique for remodeling particularly the central third of the face. The endoscope has allowed us to perform rejuvenation of the upper face or the total face without incisional scars. On the other hand, the introduction of the endoscopic techniques to the biplanar surgery allowed us to perform the deep dissection with more safety and accuracy and to eliminate or decrease some of the undesirable sequelae of the traditional approaches such as the numbness on the forehead beyond the hairline or scalp incisions. In the lower face, the endoscopic techniques allowed us to protect the marginal mandibular branch of the facial nerve, and, on the neck, these techniques allowed us to perform a very accurate subplatysma dissection. The endoscope has allowed us to create a new technique for facial rejuvenation that can be equal to and perhaps in some cases even more versatile than other traditional, nonendoscopic approaches. In this way, we can tailor the operative procedure to the patient's needs rather than to give one type of operation to every patient that walks in for an office consultation. It will become imperative to outline the indications, contraindications, and limitations of each variation and to determine the appropriate role of the endoscope in facial rejuvenation. Only then will we better serve our colleagues and our patients.  相似文献   
28.
Understanding interfaces between dissimilar materials is crucial to the development of modern technologies, for example, semiconductor–dielectric and thermoelectric–semiconductor interfaces in emerging electronic devices. However, the structural characterization of buried interfaces is challenging because many measurement techniques are surface sensitive by design. When interested in interface evolution during synthesis, the experimental challenges multiply and often necessitate in situ techniques. For solution‐derived lead zirconate titanate (PZT) ferroelectric thin films, the evolution of buried interfaces during synthesis (including dielectric–metal and metal–metal) is thought to dramatically influence the resultant dielectric and ferroelectric properties. In the present work, multiple experimental and computational methods are combined to characterize interface evolution during synthesis of ferroelectric PZT films on platinized Si wafers—including in situ X‐ray diffraction during thermal treatment, aberration‐corrected scanning transmission electron microscopy of samples quenched from various synthesis states, and calculations using density functional theory. Substantial interactions at buried interfaces in the PZT/Pt/Ti/SiO x /Si heterostructure are observed and discussed relative to their role(s) in the synthesis process. The results prove that perovskite PZT nucleates directly from the platinum (111)‐oriented bottom electrode and reveal the roles of Pb and O diffusion and intermetallic Pt3Pb and Pt3Ti phases.  相似文献   
29.
We describe a patient with polyostotic fibrous dysplasia and secondary malignant fibrous histiocytoma in a spinal lesion.  相似文献   
30.
Data were collected by telephone from a random sample of 762 students at the University of Northern Colorado to examine students' fear of human immunodeficiency virus (HIV) infection and their suggested approaches to prevent the spread of the disease. Of the 762 students interviewed, 177 (24.1%) believed that HIV/acquired immunodeficiency syndrome (AIDS) was a threat to socialization on campus. Fourteen percent of the female students considered HIV/AIDS to be a threat compared with 10.1% of their male counterparts. Among all interviewees, 573 (76.7%) believed HIV/AIDS was a threat to romance at the university. Statistically significant association was found between the perceived fear of HIV/AIDS and gender. With regard to actual sexual intercourse, 86.4% of the students believed that HIV/AIDS was a major threat compared with 13.6% who did not. The association between the perception about HIV/AIDS as a threat to on-campus sexual intercourse and gender was statistically significant. Of the entire sample, 69.3% suggested abstinence as an approach to avoid HIV infection. Slightly more than 24% suggested condom use. Eighteen (10.8%) students advised that sexual contact should be only with a trusted partner. More information about HIV/AIDS should be provided to all students, especially women, in institutions of higher learning. More information can reduce the fear associated with this deadly disease.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号