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   290篇
  免费   1篇
综合类   1篇
化学工业   2篇
轻工业   3篇
冶金工业   285篇
  2018年   1篇
  2014年   2篇
  2013年   1篇
  2003年   1篇
  1999年   5篇
  1998年   76篇
  1997年   56篇
  1996年   25篇
  1995年   15篇
  1994年   15篇
  1993年   24篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1986年   1篇
  1982年   3篇
  1981年   1篇
  1980年   6篇
  1978年   2篇
  1977年   15篇
  1976年   37篇
排序方式: 共有291条查询结果,搜索用时 343 毫秒
41.
The prevalence rates and serovar distributions of Chlamydia trachomatis cervical infections were investigated in two different groups of women. Group I consisted of 393 asymptomatic young women (aged 17 to 30 years) who were invited to participate in a C. trachomatis screening program. Group II consisted of 734 randomly selected patients (aged 17 to 68 years) attending an inner-city gynecological outpatient clinic. C. trachomatis was detected in cervical scrapes by PCR specific for endogenous plasmid. These plasmid PCR-positive samples were subsequently subjected to genotyping by C. trachomatis-specific omp1 PCR-based restriction fragment length polymorphism analysis (J. Lan, J. M. M. Walboomers, R. Roosendaal, G. J. van Doornum, D. M. MacLaren, C. J. L. M. Meijer, and A. J. C. van den Brule, J. Clin. Microbiol. 31:1060-1065, 1993). The overall prevalence rates of C. trachomatis found in patients younger than 30 years were 9.2 and 11.8% in groups I and II, respectively. A clear age dependency was seen in group II, with the highest prevalence rate (20%) found in patients younger than 20 years, while the rate declined significantly after 30 years of age (5.9%). In women younger than 30 years, the genotyping results showed that serovars E, I, and D (in decreasing order) were frequent in group I, while serovars F, E, and G (in decreasing order) were predominantly found in group II. The study shows that C. trachomatis infections are highly prevalent in asymptomatic young women. The different serovar distributions found most likely reflect the different compositions of the study groups, but additional analysis of the case histories of individual patients suggests that certain serovars might be associated with symptomatic (i.e., serovar G) or asymptomatic (i.e., serovars D and I) infections.  相似文献   
42.
Two methods were used to compare the biodegradation of six polychlorinated biphenyl (PCB) congeners by 12 white rot fungi. Four fungi were found to be more active than Phanerochaete chrysosporium ATCC 24725. Biodegradation of the following congeners was monitored by gas chromatography: 2,3-dichlorobiphenyl, 4,4'-dichlorobiphenyl, 2,4',5-trichlorobiphenyl (2,4',5-TCB), 2,2',4,4'-tetrachlorobiphenyl, 2,2',5,5'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl. The congener tested for mineralization was 2,4',5-[U-14C]TCB. Culture supernatants were also assayed for lignin peroxidase and manganese peroxidase activities. Of the fungi tested, two strains of Bjerkandera adusta (UAMH 8258 and UAMH 7308), one strain of Pleurotus ostreatus (UAMH 7964), and Trametes versicolor UAMH 8272 gave the highest biodegradation and mineralization. P. chrysosporium ATCC 24725, a strain frequently used in studies of PCB degradation, gave the lowest mineralization and biodegradation activities of the 12 fungi reported here. Low but detectable levels of lignin peroxidase and manganese peroxidase activity were present in culture supernatants, but no correlation was observed among any combination of PCB congener biodegradation, mineralization, and lignin peroxidase or manganese peroxidase activity. With the exception of P. chrysosporium, congener loss ranged from 40 to 96%; however, these values varied due to nonspecific congener binding to fungal biomass and glassware. Mineralization was much lower, 相似文献   
43.
OBJECTIVE: To determine the outcome of DSM-III-R schizophreniform disorder with good prognostic features. METHOD: A 6-year follow-up of 20 cases was conducted with structured interviews (comprehensive assessment of symptoms and history) and assessments of functioning scales (global assessment of functioning, Strauss-Carpenter Scale). RESULTS: Thirty-five percent of the cases had major affective disorders, 35% had schizophreniform episodes and major affective disorders, 5% had schizophreniform episodes only, 10% developed schizophrenia, and 15% had no disorders. CONCLUSION: The findings suggest an association between schizophreniform disorder with good prognostic features and affective illness.  相似文献   
44.
45.
46.
47.
CONTEXT: Multiple comprehensive, risk-adjusted studies evaluating short-term surgical mortality have been reported previously. This report analyzes short-term and long-term outcomes, both nationally and at each individual transplant program, for all solid organ transplantations performed in the United States. OBJECTIVES: To report graft and patient survival rates for all solid organ transplantations, both nationally and at each specific transplant program in the United States, and to compare the expected survival rate with the actual survival rate of each individual program. DESIGN AND SETTING: Multivariate regression analysis of donor and recipient factors affecting graft and patient survival of all kidney, liver, pancreas, heart, lung, and heart-lung transplants reported to the United Network for Organ Sharing from 742 separate transplant programs. PATIENTS: A cohort of 97587 solid organ transplantations performed on 92966 recipients in the United States from January 1988 through April 1994. MAIN OUTCOME MEASURES: Short-term and conditional 3-year national and individual transplant program graft and patient survival rates overall and from 2 separate eras (era 1, January 1988-April 1992; era 2, May 1992-April 1994); comparison of actual center-specific performance with risk-adjusted expected performance and identification of centers with better-than-expected or worse-than-expected survival rates. RESULTS: One-year graft follow-up exceeded 98% and conditional 3-year follow-up exceeded 91% for all organs. Graft and patient survival improved significantly in era 2 compared with era 1 for all cadaver organs except heart, which remained the same. One-year cadaveric graft survival ranged from 81.5% for heart to 61.9% for heart-lung and 3-year conditional graft survival ranged from 91.3% for pancreas to 74.7% for lung. The percentage of programs whose actual 1-year graft survival was not different from or was better than their risk-adjusted expected survival ranged from 98.3% for heart-lung to 75.7% for liver. Most kidney, liver, and heart programs whose actual survival was significantly less than expected performed small numbers (less than the national average) of transplantations per year. CONCLUSIONS: Graft and patient survival for solid organ transplantations showed improvement over time. Conditional 3-year graft and patient survival rates were approximately 90% for all organs except for lung and heart-lung. The conditional 3-year survival rates were better than 1-year survival rates, indicating the major risk after transplantation occurs in the first year. The majority of transplant programs achieved actual survival rates not significantly different from their expected survival rates. Center effects were most significant within the first year after transplantation and had much less influence on long-term survival outcomes.  相似文献   
48.
Bowen's disease of the anal region is a rare, slow-growing, intraepidermal squamous-cell carcinoma (carcinoma in situ). If surgical excision is incomplete, there is a risk of subsequent development of malignancy and metastasis. Between 1980 and 1995 we treated 11 patients (8 female, 3 male) with anal Bowen's disease. The mean age was 55 (34-75) years. The main reason for excision was: pain (4), itching (3), bleeding (3) and a disturbing lump (3). The intraoperative findings were in all cases a lesion at the anocutaneous line: perianal or intra-anal tumor (6), erosion (2) or ulceration (2) as well as lichenoid lesion (4) or hyperpigmentation (3). The procedure was excision of the lesion in 10 cases. Only in one case was a biopsy taken. 3 patients had to be operated on a second time for reasons of radicality. 5 years after primary diagnosis, one patient developed a recurrent invasive squamous-cell carcinoma and had to undergo perineo-abdominal rectum amputation with postoperative radiotherapy (2 years after operation). Only one patient underwent a biopsy, which produced the diagnosis of invasive squamous-cell carcinoma. He underwent combined chemo-radiotherapy. The symptoms of anal Bowen's disease are unspecific and the clinical findings are uncharacteristic. The recommended therapy is complete surgical excision. With complete excision no recurrences do occur.  相似文献   
49.
The effects of alpha-tocopherol (50 mg/d) and beta-carotene (20 mg/d) supplementation on symptoms of chronic obstructive pulmonary disease were studied among the 29,133 participants of the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study undertaken to investigate the effects of these two substances in the prevention of lung and other cancers. During the follow-up the supplementations did not affect the recurrence or incidence of chronic cough, phlegm, or dyspnea. The prevalence of chronic bronchitis and dyspnea at baseline was lower among those with high dietary intake of beta-carotene (OR = 0.78 and 0.67, respectively) or vitamin E (OR = 0.87 and 0.77) and high serum beta-carotene (OR = 0.59 and 0.62) and alpha-tocopherol (OR = 0.76 and 0.82). High intake and serum levels of retinol were associated with low prevalence of dyspnea (OR = 0.84 and 0.80, respectively) but not with chronic bronchitis. The results indicate no benefit from supplementation with alpha-tocopherol or beta-carotene on the symptoms of chronic obstructive pulmonary disorders but support the beneficial effect of dietary intake of fruits and vegetables rich in these compounds.  相似文献   
50.
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