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   3246066篇
  免费   282043篇
  国内免费   14599篇
耳鼻咽喉   45608篇
儿科学   99425篇
妇产科学   82704篇
基础医学   512811篇
口腔科学   87956篇
临床医学   297023篇
内科学   567485篇
皮肤病学   89603篇
神经病学   283439篇
特种医学   129174篇
外国民族医学   199篇
外科学   516471篇
综合类   102069篇
现状与发展   92篇
一般理论   2273篇
预防医学   272490篇
眼科学   74301篇
药学   220195篇
  22篇
中国医学   9183篇
肿瘤学   150185篇
  2021年   55940篇
  2020年   37386篇
  2019年   58729篇
  2018年   73712篇
  2017年   56887篇
  2016年   62774篇
  2015年   77031篇
  2014年   113878篇
  2013年   179032篇
  2012年   90342篇
  2011年   88993篇
  2010年   119272篇
  2009年   125675篇
  2008年   75716篇
  2007年   77730篇
  2006年   89370篇
  2005年   83871篇
  2004年   85964篇
  2003年   76483篇
  2002年   65888篇
  2001年   85425篇
  2000年   77140篇
  1999年   81137篇
  1998年   64682篇
  1997年   62852篇
  1996年   60215篇
  1995年   55687篇
  1994年   49715篇
  1993年   46388篇
  1992年   57730篇
  1991年   55089篇
  1990年   52155篇
  1989年   51771篇
  1988年   48484篇
  1987年   47378篇
  1986年   45167篇
  1985年   45709篇
  1984年   43680篇
  1983年   40329篇
  1982年   40373篇
  1981年   38168篇
  1980年   36093篇
  1979年   36924篇
  1978年   33565篇
  1977年   30888篇
  1976年   28069篇
  1975年   26585篇
  1974年   27718篇
  1973年   26640篇
  1972年   25076篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Restriction fragment length polymorphism (RFLP) of human mitochondrial DNA was analysed in a sample of 87 subjects from Apulia (South Italy) by the restriction enzymes Hpa I, Bam HI, Hae II, Msp I, Ava II, and Hinc II using total blood cell DNA probed by human mtDNA from placenta. Five BamHI morphs were observed, two of which are new ( Bam HI-4 and -5), as well as one new Ava II morph ( Ava II-28). The association Bam HI-4/ Ava II-28 enables us to demonstrate for the first time two polymorphic Bam HI sites present together in the same mtDNA molecule. In agreement with historical data the Apulian sample has been shown to be the most heterogeneous Italian population so far tested.  相似文献   
992.
Department of Biology, Izhevsk Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR D. S. Sarkisov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 3, pp. 353–356, March, 1989.  相似文献   
993.
Plasma tumor necrosis factor and mortality in critically ill septic patients   总被引:23,自引:0,他引:23  
Tumor necrosis factor (TNF) cachectin has been implicated as an important host mediator responsible for shock and multiple organ failure (MOF) observed during sepsis. Using a sensitive enzyme-linked immunosorbent assay, we measured plasma TNF levels in 43 septic patients suffering from a broad range of diseases. Measurements were taken on the day that sepsis was diagnosed. Eleven patients had detectable TNF plasma levels ranging from 10 to 100 pg/ml (TNF-positive group); in 32 patients circulating TNF could not be detected (TNF-negative group). The groups did not differ significantly as to age, underlying disease, percentage positive bacteremia and bacteriologic profile, sepsis score, and extent of MOF. Eight (73%) of 11 TNF-positive patients died from sepsis during ICU stay, vs. 11 (34%) of 32 TNF-negative patients (p less than .05). This study demonstrates that sepsis is accompanied by detectable circulating TNF in 25% of the cases, and for these patients mortality is twice that for comparable TNF-negative patients.  相似文献   
994.
In 1981 a statewide program supplying free insulin to 3,720 patients of state health clinics was discontinued. We attempted to assess whether this action had an adverse effect medically and financially on those concerned. A computer randomized sample of 351 patients (9%) was studied by personal interview and questionnaire. Information obtained focused on certain events that occurred 18 months before and after the program ceased. Measurements used to determine medical impact were number of hospitalizations, emergency room and physician visits, changes in weight and glucose levels, and episodes of ketoacidosis. Financial impact was measured by cost of hospitalization and physician visits. Our results revealed no significant changes in any of the medical parameters studied except for fasting serum glucose levels above 300 mg/dl, which occurred less frequently after the free insulin program was discontinued. There were fewer hospitalizations, more visits to physicians, and no change in number of emergency room visits after discontinuance of the free program. The overall cost saving was estimated to be +883,558 for the 18-month study period, in addition to the +550,000 the plan had been costing the state.  相似文献   
995.
The aqueous, organic, and volatile oil extracts of leaves of Eugenia uniflora Linn. Family Myrtaceae were investigated for antibacterial properties using agar dilution techniques. The aqueous extract was the most active against the organisms compared to the organic and volatile oil extracts. The extracts were found to inhibit Gram positive Staphylococcus aureus and Bacillus subtilis and Gram negative Escherichia coli and Shigella dysentcriae. Pseudomonas aeruginosa, Klebsiella pneumoniac, and Salmonella typhi were not inhibited.  相似文献   
996.
The in vitro ability of bacterial purified antigenic fractions to interfere with the immune system has been investigated on human mononuclear cells from peripheral blood. Exposure of purified monocytes to the drug at concentrations from 1 to 1000 micrograms/ml, for different periods from 0 to 18 h, significantly increased cell-mediated cytotoxicity against TU5 target cells. Moreover, monocytes exposed for 1 to 18 h to drug concentrations from 0.1 to 1000 micrograms/ml released significant amounts of tumor necrosis factor alpha in a dose-dependent manner in the culture supernatants. The drug was also tested on natural killer (NK) cell activity; mononuclear cells exposed to antigenic fractions for different periods showed a significant increase of NK cytotoxic activity against K562 target cells after 3 and 6, but not 0 and 18 h. Active concentrations were from 1 to 100 micrograms/ml, higher and lower doses being ineffective. Bacterial purified antigenic fractions thus have some ability to interfere in vitro with mechanisms of cytolysis mediated by cells and soluble factors.  相似文献   
997.
Summary Split or full thickness eyelid defects resulting from tumor destruction or surgical excision present a dilemma for plastic and reconstructive surgeons. Full thickness eyelid replacement requires composite grafting of the skin, together with tarsal support of its substitute and mucosa. The flap described by Fricke in 1829 was used for reconstruction of anterior lamella in six lower eyelid defects. In three of our cases chondromucosal grafts taken from nasal septum were utilized for posterior lamella repair. The results have been satisfactory from a functional and cosmetic standpoint.  相似文献   
998.
999.
1000.
The administration of prophylactic antibiotics in surgery is appropriate for many patients. Data have shown extending the duration of prophylaxis beyond 48 hours does not lower the rate of postoperative-infection. The purpose of this project was to concurrently assess the duration of prophylactic antibiotic use. A total of 95 patients were monitored over 3 weeks. Eighty patients (84.2%) received antimicrobial therapy. In 23 of these patients (28.75%) the duration of antibiotic administration was longer than 2 days without clinical or microbiological evidence of infection. In 5 other patients only postoperative antibiotics were prescribed. The cost difference between the actual duration of antibiotic administration and 2 days of the same regimen was +1,364.58. Extrapolating for one year, it can be estimated that antibiotic costs could be reduced about +23,600. Pharmacists can focus on the duration of antibiotic prophylaxis as a cost containment measure.  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