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   1108篇
  免费   11篇
  国内免费   2篇
电工技术   3篇
综合类   3篇
化学工业   124篇
金属工艺   14篇
机械仪表   3篇
建筑科学   4篇
能源动力   12篇
轻工业   14篇
水利工程   2篇
石油天然气   1篇
无线电   24篇
一般工业技术   86篇
冶金工业   808篇
原子能技术   8篇
自动化技术   15篇
  2024年   5篇
  2023年   2篇
  2022年   4篇
  2021年   8篇
  2020年   8篇
  2019年   10篇
  2018年   17篇
  2017年   20篇
  2016年   9篇
  2015年   5篇
  2014年   10篇
  2013年   19篇
  2012年   21篇
  2011年   21篇
  2010年   16篇
  2009年   9篇
  2008年   9篇
  2007年   13篇
  2006年   11篇
  2005年   5篇
  2004年   2篇
  2003年   4篇
  2002年   8篇
  2001年   9篇
  2000年   6篇
  1999年   30篇
  1998年   270篇
  1997年   162篇
  1996年   91篇
  1995年   49篇
  1994年   36篇
  1993年   52篇
  1992年   6篇
  1991年   10篇
  1990年   10篇
  1989年   11篇
  1988年   8篇
  1987年   4篇
  1986年   8篇
  1985年   3篇
  1983年   5篇
  1982年   2篇
  1981年   6篇
  1980年   4篇
  1978年   2篇
  1977年   31篇
  1976年   56篇
  1974年   6篇
  1971年   4篇
  1968年   1篇
排序方式: 共有1121条查询结果,搜索用时 15 毫秒
41.
AIMS/BACKGROUND: To characterise clinically a large kindred segregating retinitis pigmentosa and sensorineural hearing impairment in an autosomal dominant pattern and perform genetic linkage studies in this family. Extensive linkage analysis in this family had previously excluded the majority of loci shown to be involved in the aetiologies of RP, some other forms of inherited retinal degeneration, and inherited deafness. METHODS: Members of the family were subjected to detailed ophthalmic and audiological assessment. In addition, some family members underwent skeletal muscle biopsy, electromyography, and electrocardiography. Linkage analysis using anonymous microsatellite markers was performed on DNA samples from all living members of the pedigree. RESULTS: Patients in this kindred have a retinopathy typical of retinitis pigmentosa in addition to a hearing impairment. Those members of the pedigree examined demonstrated a subclinical myopathy, as evidence by abnormal skeletal muscle histology, electromyography, and electrocardiography. LOD scores of Zmax = 3.75 (theta = 0.10), Zmax = 3.41 (theta = 0.10), and Zmax = 3.25 (theta = 0.15) respectively were obtained with the markers D9S118, D9S121, and ASS, located on chromosome 9q34-qter, suggesting that the causative gene in this family may lie on the long arm (q) of chromosome 9. CONCLUSIONS: These data indicate that the gene responsible for the phenotype in this kindred is located on chromosome 9 q. These data, together with evidence that a murine deafness gene is located in a syntenic area of the mouse genome, should direct the research community to consider this area as a candidate region for retinopathy and/or deafness genes.  相似文献   
42.
Two cases of cavitary lung cancer with pulmonary aspergillosis were experienced. Case 1 was a 45-year-old male. Chest X-ray and Chest CT revealed a round shadow in the thin-wall cavity of the upper lobe of the right lung. Upper lobectomy of the right lung was performed. Histologically large cell carcinoma was found to invade the entire cavity wall, and aspergillus was not detected in the intracavitary space. Case 2 was a 75-year-old male. Chest X-ray and Chest CT revealed a round shadow in the thin-wall cavity of the upper lobe S1 + 2 of the left lung. As a result of upper lobectomy of the left lung and S6 partial resection, large cell carcinoma was found to invade the entire cavity wall, and aspergillus was not detected in the intracavitary space. Only 19 cases including ours are reported about cases of lung cancer complicated by pulmonary aspergillosis at the same site in Japan. The mechanism of aspergillus infection had not been clarified in the discussions of the reported literature and nothing characteristic could be pointed out in our cases except for the assumption that the presence of cancer was a factor triggering Aspergillus implantation.  相似文献   
43.
LA Smith  DE Barker  CW Chase  LB Somberg  WB Brock  RP Burns 《Canadian Metallurgical Quarterly》1997,63(12):1102-7; discussion 1107-8
The purpose of this review is to present a 4-year experience with the vacuum pack technique of temporary abdominal closure. From April 1992 to December 1996, 171 vacuum packs were performed on 93 patients. Eighty-seven vacuum packs were performed on 38 general surgical patients, and 84 vacuum packs were performed on 55 trauma patients. Overall hospital mortality was 32 per cent. Methods of achieving permanent wound closure varied in 73 patients. Four patients (4.3%) developed enterocutaneous fistulae; four patients developed intra-abdominal abscesses (4.3%). There were no eviscerations. Management of the complicated intra-abdominal process is discussed: 1) the decision to manage the abdomen in an open fashion; 2) which method of temporary closure to use; 3) subsequent explorations; 4) when the abdomen should be closed; 5) which type of closure to use; and 6) when the abdominal wall should be revised (herniorrhaphy). The vacuum pack is the method of choice for open abdomen management and temporary abdominal closure at our institution. With careful subsequent management, good patient outcome can be achieved.  相似文献   
44.
The effect of phenylephrine-induced reflex parasympathetic stimulation on QT interval and its dispersion was studied in 16 healthy subjects with a history of paroxysmal supraventricular tachycardia, both during sinus rhythm and during atrial pacing. Results demonstrate that rapid reflex parasympathetic stimulation does not influence QT interval duration or QT dispersion, and also emphasize the inappropriateness of Bazett's formula, the need for comparison of QT intervals during identical heart rates, and the importance of analyzing all 12 leads of a standard electrocardiogram when assessing the effects of various interventions on the QT interval.  相似文献   
45.
OBJECTIVE: To examine specifically the influence of estimated perioperative mortality and stroke rate on the assessment of appropriateness of carotid endarterectomy. DATA SOURCES/STUDY SETTING: An expert panel convened to rate the appropriateness of a variety of potential indications for carotid endarterectomy based on various rates of perioperative complications. We then applied these ratings to the charts of 1,160 randomly selected patients who had carotid endarterectomy in one of the 12 participating academic medical centers. STUDY DESIGN: An expert panel evaluated indications for carotid endarterectomy using the modified Delphi approach. Charts of patients who received surgery were abstracted, and clinical indications for the procedure as well as perioperative complications were recorded. To examine the impact of surgical risk assessment on the rates of appropriateness, three different definitions of risk strata for combined perioperative death or stroke were used: Definition A, low risk < 3 percent; Definition B, low risk < 5 percent; and Definition C, low risk < 7 percent. PRINCIPAL FINDINGS: Overall hospital-specific mortality ranged from 0 percent to 4.0 percent and major complications, defined as death, stroke, intracranial hemorrhage, or myocardial infarction, varied from 2.0 percent to 11.1 percent. Most patients (72 percent) had surgery for transient ischemic attack or stroke; 24 percent of patients were asymptomatic. Most patients (82 percent) had surgery on the side of a high-grade stenosis (70-99 percent). When the thresholds for operative risk were placed at the values defined by the expert panel (Definition A), only 33.5 percent of 1,160 procedures were classified as "appropriate." When the definition of low risk was shifted upward, the proportion of cases categorized as appropriate increased to 58 percent and 81.5 percent for Definitions B and C, respectively. CONCLUSIONS: Despite the high proportion of procedures performed for symptomatic patients with a high degree of ipsilateral extracranial carotid artery stenosis and generally low rates of surgical complications at the participating institutions, the overall rate of "appropriateness" using a perioperative complication rate of < 3 percent was low. However, the rate of "appropriateness" was extremely sensitive to judgments about a single clinical feature, surgical risk. These data show that before applying such "appropriateness" ratings, it is crucial to perform sensitivity analyses in order to assess the stability of the results. Results that are robust to moderate in variation in surgical risk provide a much sounder basis for policy making than those that are not.  相似文献   
46.
Peptide 10 (NATAEGRAINRRVE, residues 305-318 of mature protein F) is one of two linear B-cell epitopes within outer membrane protein F of Pseudomonas aeruginosa both of which have been shown to elicit whole cell-reactive antibodies and to afford protection in animal models against P. aeruginosa infection. Influenza A virus was chosen as a vector to present this epitope in a human-compatible vaccine. Various lengths of the peptide 10 epitope ranging from a 5-mer (GRAIN), 7-mer (AINRRVE), 8-mer (TAEGRAIN), 9-mer (GRAINRRVE), 11-mer (AEGRAINRRVE) to a 12-mer (TAEGRAINRRVE) were attempted to be presented into the antigenic B-site of the hemagglutinin (HA) of live recombinant influenza virus. Using PCR, DNA sequences encoding these various peptide 10 lengths were inserted into the HA gene of influenza A/WSN/33 virus. By using a reverse-genetics transfection system, RNA transcribed in vitro from these chimeric HA genes was reassorted into infectious virus. To date chimeric viruses have been rescued and purified containing the peptide 10 5-mer, 7-mer, 8-mer, and 11-mer. RT-PCR and sequencing have confirmed the presence of P. aeruginosa sequences in the HA RNA segment of each chimeric virus. Each of the four chimeric viruses produced to date was used to immunize mice to determine the ability of each chimeric virus to elicit antibodies reactive with whole cells of P. aeruginosa. The immunization protocol consisted of a series of three intranasal inoculations, followed by two intramuscular injections of the chimeric virus. The chimeric virus incorporating the 11-mer elicited IgG antibodies that reacted with various immunotype strains of P. aeruginosa in a whole cell ELISA at titers of 80 to 2,560, whereas the chimeric virus incorporating the 8-mer elicited whole cell-reactive IgG antibodies at titers of 320 to 2,560. These data suggest that these two chimeric viruses may have vaccine efficacy against P. aeruginosa infection. These studies may result in the development of a chimeric influenza virus-protein F vaccine which would prove to be suitable for use in children with cystic fibrosis for the prevention of pulmonary colonization of these children with P. aeruginosa.  相似文献   
47.
There is now strong evidence that the chorioretinal degeneration associated with ornithine-delta-aminotransferase (OAT) deficiency is a consequence of hyperornithinemia. Therefore development of a metabolic system for clearing ornithine from the circulation is being pursued as a potential treatment. The skin is considered an attractive location for such a metabolic system because autologous cells can be safely and easily utilized. This study was undertaken to determine the ornithine metabolizing capacity of epidermal keratinocytes expressing normal and superphysiologic amounts of OAT. The data show that overexpression of OAT in keratinocytes cultured from a gyrate atrophy patient restores ornithine metabolism and results in a rate of ornithine disappearance from the medium that is significantly higher than the rate of disappearance from the medium bathing normal keratinocytes. In addition, OAT activity determined in soluble protein prepared from sonicates suggests that the capacity to maintain plasma ornithine within the normal range is contained within an accomplishable graft of keratinocytes overexpressing OAT. However, the actual rate of ornithine disappearance from the media was significantly less than predicted from enzyme activity assays. Following ornithine metabolite production by intact cells suggests that ornithine metabolism is limited primarily by clearance of downstream metabolites, as opposed to substrate delivery.  相似文献   
48.
The response to antigen is an important factor in the development of airway inflammation. Segmental bronchoprovocation (SBP) with antigen and subsequent bronchoalveolar lavage (BAL) have provided valuable insight into the mechanisms of allergic inflammation. To determine the features of allergic airway response in asthma, 19 subjects with mild asthma underwent antigen SBP in a dose-dependent manner. The amount of antigen used in SBP was 0 (saline), and 1, 5, or 20% of the antigen dose required to drop the FEV1 by 20% (APD20). BAL was done at 5 min and 48 h after SBP. BAL histamine levels increased modestly 5 min after antigen SBP. At 48 h, there was a marked increase in eosinophils and IL-5 concentration even in airway segments where the release of histamine was small. Moreover, eosinophils correlated with IL-5 levels at 48 h (r = 0.63; p < 0.001), but not with BAL histamine concentrations at 5 min. GM-CSF levels did not increase after antigen SBP and did not correlate with eosinophils. These observations indicate that asthmatic subjects can develop a dose-dependent response to antigen SBP that is characterized by a modest increase in histamine immediately after antigen exposure, and marked eosinophilia, which appears proportionately greater than the histamine response and relatively greater than what is seen in allergic nonasthmatic subjects. This feature might be important to the eventual development of airway inflammation in asthma.  相似文献   
49.
The analytical performance of the Tandem-R free PSA assay available from Hybritech Inc. was evaluated. Comparison of recoveries of purified free (unbound) prostate-specific antigen (PSA) diluted in female serum in the Tandem-R free PSA assay and the Tandem-R (total) PSA assay demonstrated a link in calibration between the assays and an accurate determination of percent free PSA. The cross-reactivity of the assay to purified PSA-alpha 1-antichymotrypsin was determined to be < 1%. The minimum-detectable concentration was < 0.05 microgram/L. The within-run and between-day CVs were < or = 5% for samples with > 0.3 microgram/L free PSA. Dilution and recovery showed no significant deviations from linearity across the assay range. The assay was insensitive to interference from blood components. The Tandem-R free PSA kit was shown to be an accurate, precise, and reliable assay for the measurement of free PSA.  相似文献   
50.
The hemolytic uremic syndrome (HUS) comprises hemolytic anemia, acute renal failure, and thrombocytopenia. It is the most frequent cause of acute renal failure in childhood. Ninety percent of the patients have a diarrheal prodrome, and are referred to as having typical HUS. Approximately 10% exhibit the so-called atypical HUS. Typical HUS is caused by shigatoxin-producing Escherichia coli. The toxin, bound to the globotriosyl ceramide cell receptor and internalized, interferes with protein synthesis, predominantly of endothelial cells. The main target is the kidney, but nearly every organ system can be involved. The most common extrarenal involvement is damage to the central nervous system. The central event is probably an insult to the endothelial cell with consecutive loss of antithrombogenic properties. The von Willebrand factor, activation of platelets via platelet-activating factor, other growth factors (e.g., interleukins 1, 6, 8), nitric oxide, lipopolysaccharides, activated polymorphonucleated neutrophils, and the metabolites of the arachidonic acid cascade (e.g., prostaglandin I2) are believed to be involved in the pathogenic cascade. Controlled therapeutic trials with heparin, dipyridamole, aspirin, and urokinase have not been associated with improved outcome. Antibiotics have not yielded any benefit. Plasma infusions and plasma exchange appear to be efficacious, and are justified in cases of atypical HUS and thrombotic thrombocytopenic purpura. Binding of the toxin to the intestinal lumen, and thereby inhibition of enteral reabsorption, is under investigation.  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