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   1127篇
  免费   1篇
化学工业   12篇
金属工艺   1篇
机械仪表   2篇
能源动力   2篇
轻工业   2篇
无线电   1篇
一般工业技术   2篇
冶金工业   1098篇
原子能技术   1篇
自动化技术   7篇
  2020年   1篇
  2017年   1篇
  2015年   2篇
  2013年   8篇
  2012年   1篇
  2011年   1篇
  2008年   1篇
  2003年   3篇
  2002年   1篇
  1999年   41篇
  1998年   357篇
  1997年   206篇
  1996年   113篇
  1995年   73篇
  1994年   65篇
  1993年   65篇
  1992年   11篇
  1991年   15篇
  1990年   12篇
  1989年   16篇
  1988年   12篇
  1987年   8篇
  1986年   10篇
  1985年   6篇
  1984年   2篇
  1983年   5篇
  1982年   4篇
  1981年   5篇
  1980年   4篇
  1978年   5篇
  1977年   20篇
  1976年   51篇
  1955年   2篇
  1954年   1篇
排序方式: 共有1128条查询结果,搜索用时 78 毫秒
111.
OBJECTIVE: To assess the outcome after transthoracic endoscopic sympathectomy (TES) for upper limb hyperhidrosis. DESIGN: Prospective cohort study. SETTING: District general hospital. SUBJECTS: Consecutive patients undergoing TES for upper limb hyperhidrosis over a fifteen month period. INTERVENTIONS: One-stage bilateral TES. MAIN OUTCOME MEASURES: Change in quality of life as shown by the Short Form-36 health assessment questionnaire. RESULTS: Sixteen patients (11 women and 5 men, median age 26 years) underwent operation without complications. At median follow-up of 6.2 months, symptomatic improvement was found in 26 of 32 limbs treated (82%). Truncal compensatory hyperhidrosis was reported by 13 patients but was severe in only three. There were significant improvements in social function (p = 0.01) and mental health (p = 0.025) as assessed by the SF-36. CONCLUSION: Despite a high incidence of compensatory hyperhidrosis, TES improved both the symptoms and overall quality of life in patients with upper limb hyperhidrosis.  相似文献   
112.
PURPOSE: Diagnostic strategies designed to identify the underlying primary malignancies in patients with unknown primary tumors (UPTs) have relied on retrospective analyses. We analyzed 879 consecutive patients referred with suspected UPTs to determine the yield and cost of a limited diagnostic evaluation, assess the contribution of specific studies to diagnosis, and analyze the survival patterns of patients in whom the primary tumor was diagnosed. PATIENTS AND METHODS: Data from patients with a suspected UPT were entered into a computerized data base, and the patients underwent a predefined limited diagnostic evaluation. Primary malignancies were diagnosed by pathologic review alone or by pathologic criteria plus a physical or radiographic finding. Survival was measured from diagnosis, estimated using the Kaplan-Meier method, and compared using the Cox-Mantel log-rank test. RESULTS: A primary tumor was found in 179 of 879 patients (20%). The survival duration of patients in whom the primary tumor was diagnosed was superior to that of patients in whom the primary tumor remained unknown. Specific patient subsets contributed most to the improved survival duration of the group in which the primary tumor was found, including lymphoma patients diagnosed solely by pathologic criteria and female patients with primary breast or ovarian cancer. The cost of diagnosis was mostly due to the extensive use of computed tomography. Except for ovarian cancer, computed tomography rarely identified treatable primary tumors. CONCLUSION: The limited diagnostic evaluation used in this study identified patients with treatable malignancies and increased the survival duration of a population of suspected UPT patients. Primary malignancies with the best survival can be diagnosed through careful pathologic review and focused evaluations for breast and ovarian cancer in women.  相似文献   
113.
The frequent occurrence of degenerative joint disease following complete or partial meniscectomy is well recognized. Meniscal repair has been shown to lead to a lower prevalence of degenerative changes in the knee. Arthroscopically assisted inside-to-outside meniscal repair is a safe, reproducible technique for for salvaging the torn meniscus.  相似文献   
114.
This paper is an introduction to this issue of review papers on the biological role of nitric oxide. The history, modern state, and promising directions for research in this field are briefly considered.  相似文献   
115.
An allele-specific polymerase chain reaction (ASPCR) assay for prenatal genotyping of the Kidd antigen system in order to identify pregnancies at risk for haemolytic disease of the newborn (HDN) was developed. Oligonucleotide primers were designed for ASPCR of JKA and JKB. A validation study was performed using DNA isolated from 54 serotyped whole blood samples and 8 amniocentesis samples. A concordance rate of 100 per cent was observed between serotyping and ASPCR detection of the JKA and JKB alleles. Experiments were conducted to quantify the maternal contamination that could be tolerated in Kidd ASPCR assays. The sensitivity of this assay ranged from 0.2 per cent when detecting the presence of JKB and JKA background, to 2 per cent for detecting the presence of JKA in a JKB background. This sensitive assay is particularly useful for rapid genotyping of fetal amniotic cells to identify pregnancies at risk for HDN due to incompatibilities within the Kidd blood group system.  相似文献   
116.
OBJECTIVE: To investigate patterns of attendance and non-attendance at National Health Service antenatal classes of first-time mothers in the indigenous white population of a large northern city of the UK. DESIGN: Survey using questionnaires, and selected participants were then given an in-depth interview. SETTING: Five maternity wards in two large northern hospitals in the UK. In-depth interviews took place in the respondents' homes. PARTICIPANTS: Fifty newly delivered women were surveyed of whom 18 took part in the follow-up interviews. FINDINGS: There was a clear hierarchy in attendance and non-attendance based on social class, with middle class women being the most regular attenders, closely followed by older, married, working class women. However, overall social class differences were found to be accounted for by the overwhelming non attendance of young, unmarried, working class women. Older, married, working class women were found to have attendance patterns which were close to their middle class counterparts, and what differences there were seemed to be based on material factors. KEY CONCLUSIONS: The majority of women felt that antenatal classes were too technical and did not address emotional and psychological issues. However, young, single unmarried women perceived the classes most negatively. If midwives are to attract such young women, their fears and their need for peer support will have to be recognised.  相似文献   
117.
BACKGROUND: Previously, we have shown that a premature stimulus can significantly modulate spatial gradients of ventricular repolarization (ie, modulated dispersion), which result from heterogeneous electrophysiological properties between cells. The role modulated dispersion may play in determining electrical instability in the heart is unknown. METHODS AND RESULTS: To determine if premature stimulus-induced changes in repolarization are a mechanism that governs susceptibility to cardiac arrhythmias, optical action potentials were recorded simultaneously from 128 ventricular sites (1 cm2) in 8 Langendorff-perfused guinea pig hearts. After baseline pacing (S1), a single premature stimulus (S2) was introduced over a range of S1S2 coupling intervals. Arrhythmia vulnerability after each premature stimulus was determined by measurement of a modified ventricular fibrillation threshold (VFT) during the T wave of each S2 beat (ie, S2-VFT). As the S1S2 interval was shortened to an intermediate value, spatial gradients of repolarization and vulnerability to fibrillation decreased by 51+/-9% (mean+/-SEM) and 73+/-45%, respectively, compared with baseline levels. As the S1S2 interval was further shortened, repolarization gradients increased above baseline levels by 54+/-30%, which was paralleled by a corresponding increase (37+/-8%) in vulnerability. CONCLUSIONS: These data demonstrate that modulation of repolarization gradients by a single premature stimulus significantly influences vulnerability to ventricular fibrillation. This may represent a novel mechanism for the formation of arrhythmogenic substrates during premature stimulation of the heart.  相似文献   
118.
Oral administration of large doses of protein antigen generally induces a state of systemic unresponsiveness currently termed mucosally induced tolerance. In this study, we used human milk protein (HMP) without casein as a multi-protein antigen for the study of mucosally induced tolerance. The HMP utilized in this study mainly contained secretory (S) IgA, lactoferrin (Lf) and alpha-lactalbumin (Lact). When mice were given 1 or 25 mg of HMP orally 3 times or 25 mg orally four consecutive weeks prior to systemic immunization, antigen-specific serum IgG responses to HMP were induced by subsequent parenteral immunization with 100 microg of HMP. Analysis of IgG subclasses revealed that IgG1 followed by IgG2b accounted for the IgG responses noted. When both HMP and ovalbumin (OVA) were fed to mice, tolerance developed to OVA but not to HMP. To further investigate the nature of immune responses seen following oral gavage of HMP, we examined responses to individual protein of HMP. Brisk serum IgG1 and IgG2b responses to both S-IgA and Lf were induced by oral followed by systemic immunization with HMP. Analysis of splenic CD4+ T cells from mice given oral HMP revealed production of Th2- but not Th1-type cytokines. These results show that oral administration of HMP preferentially induces exclusive Th2-type immune responses, which may prevent the development of HMP (S-IgA and Lf)-specific mucosally induced tolerance.  相似文献   
119.
A carnivore, the ferret possesses a vomeronasal organ--accessory olfactory bulb (VNO-AOB) projection to the hypothalamus; however, little is known about its function. Pheromones in soiled bedding from estrous female ferrets or an artificial peppermint odor significantly augmented nuclear Fos protein immunoreactivity (Fos-IR), a marker of neural activation, in several main olfactory bulb (MOB) sites but not in the AOB of gonadectomized male and females. Testosterone propionate (TP) significantly augmented the MOB's neuronal Fos responses to estrous females' pheromones, but not to peppermint. Estrous odors, but not peppermint, also augmented neuronal Fos-IR in the medial preoptic area (mPOA) of female, but not male, subjects. Pheromones in soiled bedding from breeding male ferrets significantly augmented neuronal Fos-IR in the MOB and in the medial amygdala of gonadectomized, TP-treated male and female subjects. Again, male pheromones failed to influence neuronal Fos-IR in the AOB of either sex, and only females showed significant increases in neuronal Fos-IR in the lateral aspect of the ventromedial nucleus and mPOA. These results point to an essential role among higher mammals of the main olfactory epithelium-MOB projection to the hypothalamus in detecting and processing pheromones. Gonadectomized ferrets showed significant increases in sniffing behavior when placed on either female or male bedding. This occurred regardless of whether they had received TP or oil vehicle, suggesting that testosterone's facilitation of neuronal Fos responses to estrous females' odors in the MOB of both sexes cannot be attributed to increased scent gathering. Androgen receptor-IR was present in the MOB granule cell layer of male and female ferrets, raising the possibility that testosterone acts directly on these cells to augment their responsiveness to pheromones.  相似文献   
120.
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