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   2055篇
  免费   5篇
电工技术   2篇
化学工业   16篇
机械仪表   1篇
建筑科学   1篇
能源动力   3篇
轻工业   3篇
无线电   16篇
一般工业技术   25篇
冶金工业   1988篇
自动化技术   5篇
  2019年   2篇
  2018年   2篇
  2016年   3篇
  2015年   2篇
  2014年   2篇
  2013年   5篇
  2011年   2篇
  2010年   3篇
  2009年   3篇
  2008年   4篇
  2007年   3篇
  2006年   3篇
  2005年   2篇
  2004年   2篇
  2003年   1篇
  2002年   1篇
  2001年   1篇
  2000年   1篇
  1999年   55篇
  1998年   628篇
  1997年   319篇
  1996年   205篇
  1995年   142篇
  1994年   124篇
  1993年   131篇
  1992年   26篇
  1991年   26篇
  1990年   19篇
  1989年   26篇
  1988年   23篇
  1987年   20篇
  1986年   20篇
  1985年   21篇
  1983年   5篇
  1982年   11篇
  1981年   8篇
  1980年   29篇
  1979年   3篇
  1978年   7篇
  1977年   45篇
  1976年   108篇
  1975年   5篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1968年   2篇
  1967年   2篇
  1964年   1篇
  1963年   1篇
  1926年   1篇
排序方式: 共有2060条查询结果,搜索用时 15 毫秒
91.
Enterohemorrhagic Escherichia coli (EHEC) strains require intimin to induce attaching and effacing (A/E) lesions in newborn piglets. Infection of newborn calves with intimin-positive or intimin-negative EHEC O157:H7 demonstrated that intimin is needed for colonization, A/E lesions, and disease in cattle. These results suggest that experiments to determine if intimin-based vaccines reduce O157:H7 levels in cattle are warranted.  相似文献   
92.
The purpose of this investigation was to compare the levels of serum IgG antibody to 85 subgingival species in 32 refractory periodontitis, 56 successfully treated, and 33 periodontally healthy subjects. Refractory subjects showed mean full mouth attachment loss and/or >3 sites showing attachment loss >2.5 mm within 1 year after 2 treatment modalities, scaling and root planing and surgery plus systemically administered tetracycline. Successfully-treated subjects showed mean attachment level gain and no sites with attachment loss >2.5 mm, 1 year post-therapy. Periodontally healthy subjects exhibited no pocket or attachment level >3 mm, and no evidence of progressing attachment loss during 1 year of monitoring. Baseline serum was obtained from each subject and tested against 85 subgingival species, including reference strains and strains isolated from refractory subjects, using checkerboard immunoblotting. Significance of differences in levels of serum antibody among groups were sought using the Kruskal-Wallis test. Refractory subjects constituted a heterogeneous group based on their serum antibody response to subgingival species. Some individuals had antibody reactions to many subgingival species, while other subjects showed fewer or low numbers of responses. On average, refractory subjects exhibited higher numbers and levels of serum antibody reactions to a wide range of subgingival species than successfully treated or periodontally healthy subjects. Differences in serum antibody among clinical groups were more striking at higher threshold levels of antibody (>50 microg/ml and > 100 microg/ml). The data showed that a subject was 10.1 x more likely to be refractory if the subject exhibited antibody reactions with >9 subgingival species at >50 microg/ml (p<0.001, after adjusting for multiple comparisons). Serum antibody to a subset of the test species differed among the clinical groups. Porphyromonas gingivalis, Bacteroidesforsythus, and some strains isolated from refractory subjects (a novel Neisseria sp., Enterococcus faecalis, Prevotella loescheii and Prevotella oulora) elicited high serum antibody in the successfully treated and refractory subjects. High levels of serum antibody to a Microbacterium lacticum-like organism, Streptococcus oralis, Streptococcus constellatus, Actinobacillus actinonmycetemcomitans serotype c and Haemophilus aphrophilus significantly increased the likelihood of a subject being refractory to conventional periodontal therapy.  相似文献   
93.
94.
95.
96.
The electrophoretic mobility of prolactin obtained from canine pituitary extract was studied with the aid of polyacrylamide disc electrophoresis. Using a preparative gel electrophoretic system the immunoreactive material was purified on a quantitative scale which was then used to develop a homologous radioimmunoassay for canine prolactin. The radioimmunoassay system was able to detect prolactin in the plasma of dogs after the administration of agents which would be expected to affect prolactin secretion.  相似文献   
97.
Anatomic correction of transposition of the great vessels   总被引:1,自引:0,他引:1  
We present a new approach for anatomic correction of transposition of the great arteries. The two coronary arteries, with a piece of the aortic wall attached, are transposed to the posterior artery. The two aortic openings are closed with a patch. The aorta and pulmonary artery are transected, contraposed, ant then anastomosed. The interventricular septal defect is closed with a patch, through a right ventriculotomy approach, because the right ventricle is no longer part of the systemic circulation. Two patients, aged 3 months and 40 days weighing 4,200 and 3,700 grams, respectively, were operated upon with deep hypothermia and total circulatory arrest. There was good recovery from the operation, with normal cardiocirculatory conditions. Renal failure developed in the first patient, and she died on the third postoperative day. During this time the cardiocirculatory conditions were good. The second patient made an uneventful recovery. Hemodynamic studies 20 days after the operation showed complete correction of the malformation. Five and one-half months after the operation, he weighs 7,500 grams, and his development is very good. We believe that this operation will be reproducible by most cardiovascular septal defect and pulmonary hypertension.  相似文献   
98.
The band centers, rotational constants, absolute frequencies, and vacuum wavenumbers for12C16O2,13C16O2,12C18O2,13C18O2,12C16O18O,14C16O2, and14C18O2have been simultaneously computed from 590 beat frequency measurements between pairs of adjacent00deg1-[10deg0,02deg0]I and II band CO2laser transitions. The input data included the 56 beat frequencies measured between adjacent12C16O2rotational lines by Petersen et al. The absolute frequencies are directly related to the cesium frequency standard via the 29 442 483.315 (0.025) MHz 10.18 μm I-R (30) and the 32 134 266.891 (0.024) MHz 9.33 μm II-R(10) transitions in12C16O2which were measured by Evenson et al. The results described in this paper will provide the means for setting up easily reproducible secondary frequency standards in the8.9-12.3 mum wavelength band.  相似文献   
99.
During January 1971--June 1975 we examined 195 patients with pancytopenia. The cause was bone marrow failure in 67.7% of cases (classic aplastic anaemia in 11.3%) hypersplenism in 7.7%, massive blood transfusions in 1.5%, severe infections in 9.7% (Gram-negative in 3%), and various other conditions in 7.8%. Records were insufficient for diagnosis in 5.6% of cases. Analysis of the 22 patients with aplastic anaemia showed no apparent aetiology in 16 (72.7%), previous phenylbutazone ingestion in 2, and Fanconi-type anaemia in 4 of 7 children. One-year survival was 73.7%, 2-year survival 71.4%, 3-year survival 63.6% and 4-year survival 57.1%. Marrow-investigation of the 21 available samples showed that 6 were acellular, 11 hypocellular and 4 normocellular. All patients received at least temporary therapy with anabolic steroids but its effectivity could not be satisfactorily assessed. Five patients died within 7 months and 5 patients went into remission, needing no further therapy. The initial haematological features of the 5 patients who died were not significantly different from those of the rest of the patients.  相似文献   
100.
To compare the efficacy and unwanted effects of amoxycillin and ampicillin in the treatment of acute exacerbations of chronic bronchitis, 199 patients were recruited from 28 centres into a double-blind between-patient comparison of four regimens: ampicillin 250 mg or 500 mg, amoxycillin 250 mg or 500 mg, each given orally three times daily for seven days. In these doses, amoxycillin and ampicillin were equally effective and there was no apparent advantage in using the higher dose of either drug in preference to the lower dose. Unwanted effects were few. Only in five patients did diarrhoea lead to withdrawal of therapy and there was no significant difference between the two drugs in this respect. Rashes occurred in four patients, all on ampicillin.  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