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   3766篇
  免费   248篇
  国内免费   9篇
耳鼻咽喉   63篇
儿科学   190篇
妇产科学   46篇
基础医学   527篇
口腔科学   133篇
临床医学   281篇
内科学   684篇
皮肤病学   200篇
神经病学   371篇
特种医学   140篇
外科学   412篇
综合类   13篇
一般理论   3篇
预防医学   413篇
眼科学   78篇
药学   238篇
中国医学   2篇
肿瘤学   229篇
  2023年   14篇
  2022年   25篇
  2021年   56篇
  2020年   54篇
  2019年   53篇
  2018年   84篇
  2017年   87篇
  2016年   74篇
  2015年   72篇
  2014年   117篇
  2013年   140篇
  2012年   215篇
  2011年   200篇
  2010年   147篇
  2009年   135篇
  2008年   219篇
  2007年   210篇
  2006年   213篇
  2005年   202篇
  2004年   205篇
  2003年   162篇
  2002年   159篇
  2001年   95篇
  2000年   87篇
  1999年   72篇
  1998年   41篇
  1997年   34篇
  1996年   39篇
  1995年   29篇
  1994年   31篇
  1993年   34篇
  1992年   67篇
  1991年   72篇
  1990年   63篇
  1989年   60篇
  1988年   57篇
  1987年   48篇
  1986年   41篇
  1985年   41篇
  1984年   29篇
  1983年   24篇
  1982年   16篇
  1981年   17篇
  1980年   24篇
  1979年   14篇
  1977年   9篇
  1975年   13篇
  1974年   11篇
  1972年   11篇
  1971年   9篇
排序方式: 共有4023条查询结果,搜索用时 15 毫秒
91.
The objectives of this study were to identify causal and contributing factors of serious patient safety incidents in a paediatric university hospital, to report on ensuing recommendations and to assess the extent of implementation of the recommendations. The possible causal and contributing factors identified in 17 incidents were classified by a system devised by Vincent et al. Proposed recommendations were classified by the same system, and degrees of implementation were established. A median of 5 causal and contributing factors per incident were identified. Twenty-two percent of all factors were related to teamwork and 22 % to task factors. A median of 5 recommendations per analysis were formulated. Most recommendations were related to task factors (36 %). The time load of each analysis was a mean of 27 h. One third of the recommendations have been acted upon, mostly those related to task and team factors. Conclusion: Incident analysis is time-consuming but yields indispensable information on causal and contributing factors, presenting numerous opportunities for quality improvement. The value of these analyses could be improved by appointing responsibilities and setting up time frames for implementation. A bottom-up approach with managerial support appears to be a key to turning incident analysis and quality improvement into an ongoing process.  相似文献   
92.
93.
94.
Zusammenfassung Es wird ein Trennungsgang zur systematischen Fraktionierung von Crotonöl beschrieben, der unter Anwendung multiplikativer Verteilungs- und chromatographischer Verfahren sowie geeigneter biologischer Teste die Isolierung von zwei hochwirksamen Substanzen A und B in reproduzierbarer Weise ermöglicht. Diese Substanzen enthalten praktisch die gesamte toxische, entzündliche und cocarcinogene Aktivität des Crotonöls. Die beiden harzartigen Wirkstoffe unterscheiden sich signifikant im R f-Wert, wandern aber jeweils als einheitliche Flecken und zeigen sehr ähnliche physikalische, chemische und biologische Eigenschaften. Sie stellen die wirksamsten bisher beschriebenen Cocarcinogene dar.
Summary For systematic fractionation of Croton Oil a separation scheme is described employing multiple distribution and chromatography in combination with suitable biological assays. In a reproducible manner two highly active compounds have been isolated which represent together practically all the toxic, irritant and cocarcinogenic activity of Croton Oil. In thin layer chromatography the resinous compounds show significantly different R f-values but migrate as one single spot respectively. They show very similar physical, chemical and biological properties and represent the most potent cocarcinogens described as yet.


Herrn Prof. Dr. H. Hamperl zum 65. Geburtstag in dankbarer Verehrung gewidmet.  相似文献   
95.
C A Bos 《Vaccine》1988,6(4):309-314
The apparently increasing evidence of herpes simplex virus infections of the genital tract has focused attention on preventing the infection by vaccination. Herpes genitalis is not, however, the most quantitatively important clinical manifestation of herpes simplex virus infections. Because 41% of the hospitalized patients are younger than 20 years, vaccination of birth cohorts would be more favourable. In this paper the financial benefits of a hypothetical herpes simplex virus vaccination were calculated with the use of a population projection model. For the Netherlands, if the price of the hypothetical herpes simplex virus vaccine equals the cost price of the mumps component of the combined mumps-measles-rubella vaccine, the herpes vaccine would be profitable within 8 years.  相似文献   
96.
Segmented filamentous bacteria (SFB) are autochthonous bacteria inhabiting the intestinal tracts of many species, including humans. We studied the effect of SFB on the mucosal immune system by monoassociating formerly germfree C3H/HeN mice with SFB. At various time points during 190 days of colonization, fragment cultures of small intestine and Peyer's patches (PP) were analyzed for total immunoglobulin A (IgA) and SFB-specific IgA production. Also, phenotypic changes indicating germinal center reactions (GCRs) and the activation of CD4(+) T cells in PP were determined by using fluorescence-activated cell sorter analyses. A second group of SFB-monoassociated mice was colonized with a gram-negative commensal, Morganella morganii, to determine if the mucosal immune system was again stimulated and to evaluate the effect of prior colonization with SFB on the ability of M. morganii to translocate to the spleen and mesenteric lymph nodes. We found that SFB stimulated GCRs in PP from day 6 after monoassociation, that GCRs only gradually waned over the entire length of colonization, that natural IgA production was increased to levels 24 to 63% of that of conventionally reared mice, and that SFB-specific IgA was produced but accounted for less than 1.4% of total IgA. Also, the proportion of CD4(+), CD45RBlow T cells, indicative of activated cells, gradually increased in the PP to the level found in conventionally reared mice. Secondary colonization with M. morganii was able to stimulate GCRs anew, leading to a specific IgA antibody response. Previous stimulation of mucosal immunity by SFB did not prevent the translocation of M. morganii in the double-colonized mice. Our findings generally indicate that SFB are one of the single most potent microbial stimuli of the gut mucosal immune system.  相似文献   
97.
98.
A mitochondrial myopathy in an infant with lactic acidosis   总被引:1,自引:0,他引:1  
We describe a girl with mitochondrial myopathy, who presented with general muscle weakness, muscle hypotonia and motor retardation. The level of blood lactate and pyruvate was consistently increased. Enzymatic studies showed impairment of NADH-dehydrogenase activity (complex I of the respiratory chain) in skeletal muscle. Electron-microscopy of a muscle biopsy showed abnormalities of a mitochondrial myopathy. The girl, now aged 30 months, has been treated with riboflavine (vitamin B2) since the age of 14 months, and lactate and pyruvate levels have decreased to normal. The patient still shows mild muscle hypotonia and weakness, but good motor progress and normal cognitive development.  相似文献   
99.
Background and ObjectivesIntrusive images after a traumatic event, a hallmark feature of post-traumatic stress disorder, are suggested to develop because the trauma memory is disorganized and not integrated into autobiographical memory. Unconscious Thought Theory predicts that information can be conceptually organized after a period of unconscious thought (UT), more so than after conscious thought (CT). We aimed to test the hypothesis that UT decreases intrusions and increases conceptual organization in memory.MethodsParticipants were shown a stressful film and were required to perform an UT task, a CT task, or a distraction task. Intrusions of the film, intrusion qualities, and sequence memory were measured afterwards.ResultsWe confirmed our hypothesis that UT (versus CT or mere distraction) leads to fewer intrusions, thereby replicating earlier research. Contrary to prediction, we found no difference between the conditions on sequence memory. In addition, conscious thought appeared to increase intrusion nowness and arousal.LimitationsThe analogue design and healthy participant sample prevent from generalizing results to other populations. Intrusion frequency and qualities were assessed immediately after the film thereby prohibiting us from drawing conclusions about any long-term effects.ConclusionsEngaging in unconscious thought after a stressful film can reduce intrusion frequency. This has potential implications for clinical interventions to prevent initial stress symptoms. The underlying mechanism remains unclear for now and provides an avenue for future research.  相似文献   
100.
Objectives: We investigated the haemodynamic effect of percutaneous closure of an intra‐atrial shunt, using non‐invasive finger pressure measurements. Background: Percutaneous closure of both patent foramen ovale (PFO) and atrial septal defect (ASD) is widely practised. Currently no data are available on short‐term haemodynamic changes induced by closure. Methods: Twenty‐five consecutive patients (mean age 49 ± 17 years, 10 men) who underwent a percutaneous closure of a PFO (n = 15) or ASD (n = 10) were included in this study. During the procedure blood pressure and heart rate (HR) were monitored continuously with a Finometer®. Changes in systolic, mean, and diastolic pressure, stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were computed from the pressure registrations using Modelflow® methodology. Results: Baseline characteristics were similar for the PFO and ASD patients. After PFO closure none of the haemodynamic parameters changed significantly. After ASD closure the systolic, mean, and diastolic pressures increased 7·1 ± 5·4 (P = 0·003), 3·8 ± 3·5 (P = 0·007) and 2·0 ± 3·0 mmHg (P = ns) respectively. HR decreased 5·1 ± 5·3 beats per minute (P = 0·01). SV, CO and TPR increased 8·5 ± 6·4 ml (13·5%; P = 0·002), 0·21 ± 0·45 l min?1 (5·6%; P = ns) and 0·02 ± 0·14 dynes (4·1%; P = ns) respectively. The changes in SV differ between the PFO and ASD patients (P = 0·009). Conclusions: Using non‐invasive finger pressure measurements, we found that SV, mean and systolic blood pressure increased immediately after percutaneous closure of an ASD in adults, whereas the percutaneous PFO closure had no effect on haemodynamic characteristics.  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