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   598篇
  免费   0篇
化学工业   13篇
金属工艺   5篇
机械仪表   11篇
矿业工程   2篇
石油天然气   18篇
无线电   5篇
一般工业技术   16篇
冶金工业   501篇
原子能技术   18篇
自动化技术   9篇
  2021年   2篇
  2018年   4篇
  2017年   4篇
  2014年   4篇
  2013年   3篇
  2012年   4篇
  2011年   3篇
  2010年   1篇
  2009年   2篇
  2008年   4篇
  2007年   3篇
  2006年   2篇
  2003年   2篇
  2001年   2篇
  2000年   2篇
  1999年   7篇
  1998年   144篇
  1997年   70篇
  1996年   66篇
  1995年   35篇
  1994年   30篇
  1993年   43篇
  1992年   2篇
  1991年   8篇
  1990年   4篇
  1989年   10篇
  1988年   4篇
  1987年   3篇
  1986年   8篇
  1985年   8篇
  1984年   1篇
  1983年   1篇
  1982年   6篇
  1981年   6篇
  1980年   4篇
  1979年   3篇
  1978年   4篇
  1977年   16篇
  1976年   42篇
  1975年   3篇
  1974年   4篇
  1973年   5篇
  1972年   2篇
  1971年   2篇
  1970年   3篇
  1967年   1篇
  1966年   1篇
  1965年   2篇
  1964年   1篇
  1963年   2篇
排序方式: 共有598条查询结果,搜索用时 107 毫秒
51.
Surface-enhanced Raman scattering (SERS) spectroscopy was used to study the structure of carbohydrate chains in glycosylated forms of alpha 1-acid glycoprotein (AGP) and in pseudoglycoproteins obtained by transferring the carbohydrate chains of AGP to a polyacrylamide carrier. It was found that AGP-D glycoform and pseudoglycoproteins containing three or more glycans per molecule, which possess high immunomodulating activity, have a specific spatial organization of carbohydrate chains. This organization is maintained by the interaction of neighboring glycans with each other and does not depend on the nature of the carrier (whether it is polypeptide or polyacrylamide).  相似文献   
52.
Bacterial strains of Aeromonas salmonicida included in the recognized subsp. acromogenes, subsp. masoucida, and subsp. smithia in addition to the large number of strains not included in any of the described subspecies are referred to as atypical A. salmonicida. The atypical strains form a very heterogeneous group with respect to biochemical characteristics, growth conditions, and production of extracellular proteasess. Consequently, the present taxonomy of the species A. salmonicida is rather ambiguous. Atypical A. salmonicida has been isolated from a wide range of cultivated and wild fish species, non-salmonids as well as salmonids, inhabiting fresh water, brackish water and marine environments in northern and central Europe, South Africa, North America, Japan and Australia. In non-salmonid fish species, infections with atypical strains often manifest themselves as superficial skin ulcerations. The best known diseases associated with atypical A. salmonicida are carp Cyprinus carpio erythrodermatitis, goldfish Carassius auratus ulcer disease, and ulcer disease of flounder Platichthys flesus, but atypical strains are apparently involved in more disease outbreaks than previously suspected. Macroscopical and microscopical studies of ulcerated fish indicate internal organs are infrequently invaded by atypical A. salmonicida. This view is supported by the fact that atypical strains are irregularly isolated from visceral organs of ulcerated fish. High mortality caused by atypical A. salmonicida has been observed in populations of wild non-salmonids and farmed salmonids, although the association between the mortality in the wild fish stocks and atypical A. salmonicida has not always been properly assessed. In injection experiments the pathogenicity of the atypical strains examined showed large variation. An extacellular A-layer has been detected in different atypical strains, but virulence mechanisms different from those described for (typical) A. salmonicida subsp. salmonicida, for example an extracellular metallo-protease and a different iron utilization mechanism, have been described. Limited information is available about the ecology, spread and survival of atypical strains in water. The commonly used therapeutic methods for the control of diseases in farmed fish caused by atypical A. salmonicida are generally effective against the atypical strains. Resistance to different antibiotics and transferable plasmid encoding multiple drug resistance have been observed in atpical A. salmonicida. Studies aimed at producing a vaccine against atypical strains are in progress.  相似文献   
53.
The etiology of sleep disordered breathing is collapse or obstruction of the upper airway during sleep. This obstruction may be localized to one or two areas or may encompass the entire upper airway passages to include the nasal cavity, nasopharynx, oropharynx, hypopharynx, and larynx. The presurgical evaluation, which includes polysomnography, a comprehensive head and neck physical examination, fiberoptic nasopharyngoscopy, and lateral cephalometric analysis is essential in directing surgical therapy in a site specific approach. The surgical procedures available to address hypopharyngeal and base of the tongue collapse include inferior sagittal mandibular osteotomy and gengioglossus advancement, hyoid myotomy and suspension, laser midline glossectomy, lingualplasty, partial glossectomy, and maxillomandibular advancement surgery. The Riley-Powell-Stanford Surgical Protocol has proven to be an effective and safe method for controlling upper airway collapse in sleep disordered breathing.  相似文献   
54.
Bronchial rupture in blunt trauma is caused by sudden compression of the chest with dislocation of the lungs. The less pliant bronchi may thus rupture. Bronchial rupture is rare in patients admitted alive. Bronchial rupture has been diagnosed in two of the last 275 severe chest traumas admitted to Ullev?l hospital since 1993 (0.7%). A 19-year-old male had total atelectasis of the lung 19 days after the trauma. A four-year-old boy experienced total collapse of the lung and became critically ill the fourth day after initial normalisation of the chest X-ray. Both patients were successfully operated on, with reconstruction of the left main bronchus in both cases, after 29 and seven days, respectively. In the child an upper lobectomy was necessary. These patients illustrate that with expectative treatment in bronchial rupture, serious complications may be experienced.  相似文献   
55.
Apart from the retinoic acid nuclear receptor family, there are two low molecular weight (15 kD) cellular retinoic acid binding proteins, named CRABPI and II. Mouse monoclonal and rabbit polyclonal antibodies were raised against these proteins by using as antigens either synthetic peptides corresponding to amino acid sequences unique to CRABPI or CRABPII, or purified CRABP proteins expressed in E. coli. Antibodies specific for mouse and/or human CRABPI and CRABPII were obtained and characterized by immunocytochemistry and immunoblotting. They allowed the detection not only of CRABPI but also of CRABPII in both nuclear and cytosolic extracts from transfected COS-1 cells, mouse embryos, and various cell lines.  相似文献   
56.
METHODS: In a randomized double-blind study, 134 patients were given 500 mg metronidazole as an intravenous infusion immediately before operation for abdominal total hysterectomy and again 8 hours later and 124 patients received placebo. RESULTS: There was more wound infection, postoperative hospitalization was longer and the sedimentation rate on the sixth postoperative day was significantly higher in the placebo group. There was no difference in postoperative temperature. Postoperative wound infections occurred in 12% in the placebo group and 6% in the metronidazole group. Eight percent in the total material had urinary tract infections, the diagnosis was based on urine cultures. CONCLUSIONS: Prophylaxis with intravenous infusion of metronidazole is recommended in total hysterectomies.  相似文献   
57.
Epidemic outbreaks of group B meningococcal disease exhibit a clonal nature consisting of a common serotype-subtype. Subtype-specific monoclonal antibodies (MAbs) directed toward two variable regions (VR1 and VR2) of the class 1 protein of Neisseria meningitidis are used in this classification scheme. A new MAb was developed to classify a nonsubtypeable (NST) strain of N. meningitidis, 7967. This MAb bound to both the NST strain and the prototype subtype P1. 14 strain, S3446, by dot blot analysis. However, a MAb produced to the prototype P1.14 strain did not bind to strain 7967. Sixteen additional strains were further identified as P1.14 with the prototype MAb; of these, 15 strains bound both MAbs. Differences in the characteristics of binding of both antibodies to the three apparently diverse P1.14 strains were studied further by using outer membrane complex proteins, immobilized peptides, and soluble peptides. Deduced amino acid analysis suggested that both MAbs bind to VR2 and that single amino acid changes within VR2 (KM, NM, or KK) might explain the differences in binding characteristics. These results demonstrated that minor variations which exist within subtype variable regions may be clearly identified only by a combination of molecular and immunologic testing. The impact of subtype variation will become more evident as subtype-specific vaccines are developed and tested for efficacy.  相似文献   
58.
An algorithm and a personal computer program for automatic distinguishing between EEC records containing evoked and no potentials, based on the detected invariants reflecting experts' experience in evoked potential analysis have been developed. The efficiency of the programme (its high accuracy and speed, low volume) has been demonstrated in the system for automatic determination of the hearing level by long-latent evoked potentials. It is easily modifiable to identify evoked potentials from other modalities (visual, somatosensory ones) in the systems using the traditional and/or up-to-date computerized EEC equipment.  相似文献   
59.
The relationship between a range of prenatal and perinatal events and risk for psychopathology in offspring was examined. Prenatal and perinatal events investigated included maternal experiences, health, and substance use during pregnancy, obstetric complications, feeding practices, and infant health during the first year of life. Offspring diagnosis was based on structured interviews conducted with 579 adolescents on two occasions. Risk for later psychopathology was associated with a number of prenatal and perinatal factors. Major depression was associated with not being breast fed and maternal emotional problems during the pregnancy. Anxiety was chiefly associated with fever and illness during the first year of life and maternal history of miscarriage and stillbirth. Disruptive behavior disorder was associated with poor maternal emotional health during the pregnancy and birth complications. Risk for substance use disorder was associated with maternal use of substances during the pregnancy. Mediating effects of maternal depression, maternal-child conflict, and physical symptoms in the child, and moderating effects of gender of child and parental education were also evaluated. The limitations of this study are discussed and future research directions are suggested.  相似文献   
60.
Since the rapid expansion of managed care coupled with dramatic reductions in lengths of inpatient stay, there is widespread concern that the emphasis on cost containment is eclipsing attention to patient care. The present study was undertaken to evaluate speculations that the majority of short-stay (less than 48 hours) admissions to a psychiatric inpatient service at a large teaching hospital in the midwestern United States consisted of public pay patients who were rapidly transferred to area state hospitals. Using two cases mix measures, severity of illness and changes in acuity and clinical outcomes of a sample of short-stay (n = 77) and longer stay (n = 145) admissions were compared. Short-stay admissions, although similar to longer stay patients in terms of demographics, Axis I diagnosis, payer status, and appropriateness of admission, are clinically distinct. The use of nonhospital alternatives in treating a subsample of suicidal patients and the implications for improved mental health services delivery are discussed.  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