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   7997篇
  免费   623篇
  国内免费   14篇
耳鼻咽喉   30篇
儿科学   229篇
妇产科学   291篇
基础医学   984篇
口腔科学   97篇
临床医学   1448篇
内科学   1187篇
皮肤病学   156篇
神经病学   862篇
特种医学   173篇
外科学   870篇
综合类   124篇
一般理论   39篇
预防医学   947篇
眼科学   172篇
药学   486篇
中国医学   4篇
肿瘤学   535篇
  2023年   44篇
  2022年   90篇
  2021年   177篇
  2020年   99篇
  2019年   182篇
  2018年   205篇
  2017年   150篇
  2016年   149篇
  2015年   194篇
  2014年   278篇
  2013年   372篇
  2012年   511篇
  2011年   559篇
  2010年   310篇
  2009年   267篇
  2008年   411篇
  2007年   506篇
  2006年   474篇
  2005年   480篇
  2004年   459篇
  2003年   414篇
  2002年   412篇
  2001年   121篇
  2000年   99篇
  1999年   109篇
  1998年   100篇
  1997年   87篇
  1996年   70篇
  1995年   62篇
  1994年   49篇
  1993年   46篇
  1992年   79篇
  1991年   86篇
  1990年   78篇
  1989年   66篇
  1988年   57篇
  1987年   60篇
  1986年   72篇
  1985年   66篇
  1984年   62篇
  1983年   52篇
  1982年   43篇
  1981年   38篇
  1980年   38篇
  1979年   42篇
  1978年   35篇
  1977年   26篇
  1976年   22篇
  1975年   25篇
  1974年   22篇
排序方式: 共有8634条查询结果,搜索用时 15 毫秒
71.
The recovery of Clostridium difficile from the stools of patients with C. difficile-associated diarrhea was evaluated by use of an enrichment broth (cycloserine-cefoxitin fructose broth supplemented with 0.1% sodium taurocholate [TCCFB]) and was compared to that from selective agar (cycloserine-cefoxitin fructose agar [CCFA]) and alcohol shock followed by inoculation onto blood agar (AS-BA). TCCFB was superior to CCFA and AS-BA, and neither the storage time nor the storage temperature affected the recovery rate.  相似文献   
72.
The new 2017 diagnostic criteria for hypermobile Ehlers–Danlos Syndrome (hEDS) provide a framework for diagnosing hEDS but are more stringent than the previous Villefranche criteria. Our clinical experience at the GoodHope EDS clinic was that the 2017 criteria left many highly symptomatic patients without a diagnosis of hEDS. We conducted a retrospective cohort study to confirm our clinic experience and assess the accuracy of the 2017 diagnostic criteria for hEDS in patients who had a previous hEDS diagnosis based on the Villefranche criteria. Our study found that 15% (n = 20 of 131) of patients with a prior diagnosis of hEDS met the 2017 diagnostic criteria, and many of the traits used to distinguish hEDS were not significantly more frequent in patients who met 2017 criteria versus those who did not. In both groups objective systemic manifestations were found less frequently than subjective systemic manifestations. Beighton score (BS) as assessed by primary care practitioner was found to be higher than assessment by EDS practitioner in 81% (n = 74 of 91) of cases. Generalized joint hypermobility was confirmed in only 46% (n = 51 of 111) of patients who had a previous diagnosis of hEDS. Higher BS did not correlate with increased number of systemic manifestations in our cohort. Common comorbidities of hEDS were found with similar frequency in those who met 2017 criteria and those who did not. Based on our cohort, the 2017 hEDS diagnostic criteria require refinement to improve its diagnostic accuracy.  相似文献   
73.
The detection of anti-HBs antibody has been carried out using a new technique where a system for the detection of HBs antigen in the solid phase is adopted to demonstrate the presence of anti HBs antibody by inhibition of the immunoenzymatic reaction. The sensitivity of the method has been compared: with that of passive haemagglutination and with that of radioimmunoassay in liquid phase, for human serum obtained from 10 chronic antibody carriers and also serum from 1 rabbit, with that of solid phase radioimmunoassay for 91 positives serums. The method appears: in the range of sensitivity of passive haemagglutination and radioimmunoassay in the liquid phase, less sensitive than that of solid phase radioimmunoassay, far superior to that of electrosyneresis.  相似文献   
74.
Rabbits made acute phase by sub-cutaneous trauma with 2% croton oil (in mineral oil) were tested by intradermal (ID) injection with platelet-granule extracts containing platelet-derived permeability factor (PDPF). Compared with controls, skin reactivity to PDPF was enhanced in acute phase animals 3–7 days post-trauma, a period of acute inflammation as reflected by the occurrence in the circulation of C-reactive protein; maximal skin responses were observed 3–4 days post-trauma. Individual skin sites reached maximum intensity 15 min–1 hour post-ID injection of PDPF and were sensitive to chlorpheniramine maleate, suggesting a major role for histamine. Intradermal injection of histamine revealed that acute phase animals yielded an initially more intense skin reaction, and were markedly less capable of recovering from the effects of histamine. These data suggest that in the acute phase, there exists a heightened and prolonged sensitivity to the action of histamine which can be exploited by pro-inflammatory agents such as PDPF.This work was supported, in part, by grants from the NIH (HL-23457) and the Institut Pasteur de Lyon. B.A.F. is the recipient of NIH Career Development Award (HL-00614). The majority of these studies were performed on sabbatical at the Institut Pasteur de Lyon (B.A.F.).  相似文献   
75.
This report describes an adult male with a partial trisomy 6p(p211-pter) and a partial monosomy 9p(9p24-pter) resulting from a de novo unbalanced translocation. This patient does not show the classical featured of the 9p partial monosomy syndrome, thus disputing the claim of Hoo et al. (1982) that 9p24 is the critical segment for the monosomy syndrome. Partial trisomy for 6p has only been previously reported in children. In addition to the chromosomal anomalies, the patient has autosomal recessive spinal muscular atrophy with a different age of onset than two affected sibs. Finally, he shows unusual audiologic and ophthalmologic signs nor previously reported as part of the 9p monosomy or 6p trisomy syndromes.  相似文献   
76.
BACKGROUND: The introduction of expensive but very effective antiviral medications has led to questions about the effects on the total use of resources for the care of patients with human immunodeficiency virus (HIV) infection. We examined expenditures for the care of HIV-infected patients since the introduction of highly active antiretroviral therapy. METHODS: We interviewed a random sample of 2864 patients who were representative of all American adults receiving care for HIV infection in early 1996, and followed them for up to 36 months. We estimated the average expenditure per patient per month on the basis of self-reported information about care received. RESULTS: The mean expenditure was $1,792 per patient per month at base line, but it declined to $1,359 for survivors in 1997, since the increases in pharmaceutical expenditures were smaller than the reductions in hospital costs. Use of highly active antiretroviral therapy was independently associated with a reduction in expenditures. After adjustments for the interview date, clinical status, and deaths, the estimated annual expenditure declined from $20,300 per patient in 1996 to $18,300 in 1998. Expenditures among subgroups of patients varied by a factor of as much as three. Pharmaceutical costs were lowest and hospital costs highest among underserved groups, including blacks, women, and patients without private insurance. CONCLUSIONS: The total cost of care for adults with HIV infection has declined since the introduction of highly active antiretroviral therapy. Expenditures have increased for medications but have declined for other services. However, there are large variations in expenditures across subgroups of patients.  相似文献   
77.
Urethane anesthetized (< 1 .3 g/kg), Sprague-Dawley (SD) rats spontaneously cycled between a cortically desynchronized state (State I) and a cortically synchronized state (State III), which were very similar to awake and slow wave sleep (SWS) states in unanesthetized animals, based on EEG criteria. These low levels of urethane anaesthesia did not cause significant respiratory depression or reductions in sensitivity to hypoxia (10% O2 in nitrogen) or hypercapnia (5% CO2 in air) in rats in either State I or State III. Thus, breathing frequency (fR), tidal volume (VT) and total ventilation (VTOT) all increased on cortical activation in urethane-anaesthetized rats whether breathing air, the hypoxic or the hypercapnic gas mixture, in a manner that was very similar to that observed in unanaesthetized animals. The relative sensitivity to hypoxia was greater in State III than State I, the relative sensitivity to CO2, overall, was equal in both states, State III occurred less often during hypoxia and hypercapnia, and hypoxic, urethane-anaesthetized rats sighed frequently, particularly in State I. This is also similar to the situation seen in unanesthetized rats. Given the similarities seen between urethane anesthetized rats in the present study and literature values for unanesthetized rats, the data suggest that urethane-anaesthetized rats provide a good model system for studying respiratory patterns and chemoreflexes as a function of cortical activation state.  相似文献   
78.

Background  

In multiple sclerosis, inflammatory cells are found in both active and chronic lesions, and it is increasingly clear that cytokines are involved directly and indirectly in both formation and inhibition of lesions. We propose that cytokine mixtures typical of Th1 or Th2 lymphocytes, or monocyte/macrophages each induce unique molecular changes in glial cells.  相似文献   
79.
Nonspecific factors such as placebo or expectancy effects may materially influence therapeutic outcome in EMG relaxation training. Yet, controlling for the expectations of experimenters has received little attention even though Rosenthal's Experimenter Expectancy Effect is well-documented. This study examined the effects of experimenter expectancy on frontal EMG conditioning. During training, experimenters were given either no expectancy or led to believe that EMG conditioning would he either difficult (low expectancy) or easy (high expectancy) to achieve. Then, the three groups of experimenters collected data from subjects undergoing 20 min of either contingent or noncontingent reinforcement for frontal EMG decreases. Postexperimental credibility checks indicated that experimenters were unaware they were being studied but could identify their expectancy condition when informed of the three conditions. Differential EMG behavior was observed between groups conditioned by experimenters with no expectancies, with contingent subjects achieving significantly lower EMG levels than noncontingent subjects. Differences were not exhibited, however, between contingent and noncontingent subjects trained by experimenters with either low or high expectancies. These findings suggest that experimenters with prior expectations may covertly communicate to subjects response sets that interfere with acquisition of differential EMG behavior.  相似文献   
80.
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