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   3262篇
  免费   271篇
  国内免费   15篇
耳鼻咽喉   11篇
儿科学   92篇
妇产科学   92篇
基础医学   446篇
口腔科学   94篇
临床医学   357篇
内科学   550篇
皮肤病学   15篇
神经病学   430篇
特种医学   142篇
外科学   444篇
综合类   100篇
预防医学   416篇
眼科学   28篇
药学   210篇
中国医学   2篇
肿瘤学   119篇
  2021年   40篇
  2020年   28篇
  2019年   48篇
  2018年   49篇
  2017年   53篇
  2016年   38篇
  2015年   55篇
  2014年   72篇
  2013年   101篇
  2012年   158篇
  2011年   150篇
  2010年   83篇
  2009年   74篇
  2008年   155篇
  2007年   192篇
  2006年   133篇
  2005年   150篇
  2004年   126篇
  2003年   138篇
  2002年   126篇
  2001年   95篇
  2000年   99篇
  1999年   90篇
  1998年   53篇
  1997年   45篇
  1996年   55篇
  1995年   44篇
  1994年   29篇
  1993年   31篇
  1992年   72篇
  1991年   67篇
  1990年   73篇
  1989年   85篇
  1988年   64篇
  1987年   48篇
  1986年   58篇
  1985年   58篇
  1984年   46篇
  1983年   36篇
  1982年   29篇
  1981年   24篇
  1979年   30篇
  1978年   23篇
  1977年   19篇
  1975年   21篇
  1974年   19篇
  1973年   23篇
  1972年   21篇
  1971年   38篇
  1969年   22篇
排序方式: 共有3548条查询结果,搜索用时 78 毫秒
71.
Transcutaneous oxygen and carbon dioxide pressure (PO2 and PCO2) foot monitoring was compared with ankle Doppler-derived systolic pressure regarding their respective abilities to discriminate the severity of limb ischemia before vascular reconstruction and to predict surgical outcome early in the postoperative period. Transcutaneous PO2 (tcPCO2), foot-chest tcPO2 index, transcutaneous PCO2 (tcPCO2), foot tcPO2/tcPCO2 index (tcPO2/tcPCO2), ankle Doppler systolic pressure (AP), and ankle-brachial pressure index (ABI) were determined in 89 revascularized limbs. The measurement of tcPO2 and foot-chest tcPO2 was found to be more sensitive to degrees of severity of limb ischemia and more closely associated with the outcome of revascularization than AP and ABI. TcPCO2 and tcPO2/tcPCO2 were not useful in assessment of the vascular patient undergoing reconstructive surgery. Before operation, tcPO2 less than or equal to 22 torr and foot-chest tcPO2 less than or equal to 0.46 indicate severe limb ischemia requiring urgent revascularization. After operation, tcPO2 less than or equal to 22 torr and foot-chest tcPO2 index less than or equal to 0.53 indicate that revascularization is likely to fail. We conclude that tcPO2 monitoring, as a metabolic test of actual tissue perfusion, is a more reliable indicator of preoperative limb ischemia and postoperative outcome of revascularization than hemodynamic, Doppler-derived pressure tests.  相似文献   
72.
Newer culture techniques have demonstrated that diabetic foot infections are polymicrobial, involving both anaerobic and aerobic bacteria. These infections are characteristically foul-smelling and create immense tissue destruction. Occasionally, despite the absence of clostridial organisms, subcutaneous gas may be present. The importance of adequate surgical debridement has been emphasized. In the event of advancing, unremitting infection involving the foot, ankle guillotine amputation may be a life-saving technique. Finally, the role of host-defense mechanism in diabetes is important. Polymorphonuclear leukocyte chemotaxis and phagocytosis are energy-dependent processes that are deficient in the diabetic. Better diabetic control with maintenance of normal blood sugars and avoidance of ketoacidosis may be the key to prevention of these morbid, lower extremity infections.  相似文献   
73.
The oral microbiota can contribute to the regulation of blood pressure by increasing the availability of nitric oxide through the reduction of nitrate to nitrite, which can be converted into nitric oxide in the stomach and then enter the circulation. It is unclear if the composition of the oral microbiota is different between women who do and do not develop preeclampsia. This study aimed to compare the composition of the buccal microbiota just prior to the development of symptoms at 36 weeks gestation in 12 women who developed late-onset preeclampsia and 24 matched women who remained normotensive throughout pregnancy by 16S rRNA gene amplicon sequencing. The abundance of the nitrate-reducing Veillonella spp V. parvula and V. dispar and a subunit of nitrate reductase narH was compared using real-time PCR. The abundance of bacteria was correlated with maternal blood pressure and dietary intake of nitrate-containing vegetables. The results showed that the abundance of nitrate-reducing bacteria including Veillonella, specifically V. parvula, and Prevotella was reduced in women who developed preeclampsia. Veillonella but not Prevotella abundance was negatively correlated with maternal blood pressure. The dietary intake of nitrate-containing vegetables did not differ between the groups and was not correlated with the abundance of Veillonella. There was no difference in the abundance of the nitrate reductase subunit narH between the groups. These results suggest that the abundance of nitrate-reducing bacteria is reduced in the oral microbiota of women who later develop preeclampsia, indicating a potential pathway for prevention.  相似文献   
74.
75.

Background  

It has been suggested that intrasphincteric injection of botulinum toxin (BTX) may represent an alternative therapy to balloon dilatation in achalasia. The aim of the present study was to test the effectiveness of botulinum toxin injections in achalasia patients, as assessed using lower oesophageal sphincter pressure (LOSP) and symptom scores, and to compare the response in patients with different types of pretreatment (no previous treatment, balloon dilatation, myotomy, BTX injection).  相似文献   
76.
OBJECTIVE: The aim of this study was to estimate the community prevalence of coughing symptoms, consistent with surveillance definitions for pertussis, and doctor-diagnosed pertussis in children aged 5-14 years. METHODOLOGY: A telephone survey of a cross-sectional community sample of parents regarding their child's cough symptoms in the previous 12 months was undertaken in a representative Australian urban region. RESULTS: In 2020 interviews, parents reported that 22% of children had a cough lasting 2 weeks or longer in the preceding 12 months, and 14% (283) had additional symptoms meeting the Centers for Disease Control (CDC) case definition for pertussis. A cough meeting the case definition was significantly more commonly reported by parents of children aged 5-9 years (17%; P < 0.001) but reported exposure to diagnosed pertussis in such cases was significantly more common in children aged 10-14 years (4.3%; odds ratio 12.8; P < 0.01). Parents of 90% of children meeting the CDC case definition sought medical advice. A diagnosis of pertussis was reported in only 1.2% of cases, which extrapolates to an annual incidence of doctor-diagnosed pertussis of 347/100,000 (95% confidence interval, 140-714 per 100,000). This contrasts with 29/100,000 notified cases in the same age group, time period and geographic area. CONCLUSION: Cough episodes meeting a clinical case definition for pertussis commonly used in surveillance are reported by a high proportion of carers of school-aged children in Australia. The majority of children who met the CDC and Australian case definitions for pertussis and sought medical attention were not identified as potentially having pertussis, suggesting underdiagnosis of pertussis. Even if less than half of this is true pertussis, the potential impact in terms of transmission of pertussis in the community is likely to be high. The reported incidence of doctor-diagnosed disease estimated from this survey was at least five and up to 20 times the official notification rate. More work needs to be done in raising awareness among medical practitioners of pertussis as a differential diagnosis in older children and adolescents with cough.  相似文献   
77.
Only three mutant cystic fibrosis (CF) alleles have to date been established as conferring a dominant mild effect on affected subjects who are compound heterozygotes. We now add a fourth, P67L, which occurs on about 1.4% of Scottish CF chromosomes. Among 13 patients (12 unrelated) with this allele, the average age at diagnosis was 22.5 +/- 11.3 years. None of the cases had consistently raised sweat chloride concentrations, the average value being 57 +/- 9 mmol/l; 77% of the patients were pancreatic sufficient. When compared to three other established mild CF alleles, R117H, A455E, and 3849 + 10kb C-T, a compound heterozygote for P67L has minimal disease and clinical suspicions are unlikely to be confirmed other than by DNA typing.  相似文献   
78.

Background

To describe the frequency of mixed specifier as proposed in DSM-5 in bipolar I patients with manic episodes, and to evaluate the effect of mixed specifier on symptom severity and treatment outcome.

Methods

This post-hoc analysis used proxies for DSM-5 mixed features specifier by using MADRS or PANSS items.

Results

Of the 960 patients analysed, 34%, 18% and 4.3% of patients, respectively, had ≥3 depressive features with mild (score ≥1 for MADRS items and ≥2 for PANSS item), moderate (score ≥2 MADRS, ≥3 PANSS) and severe (score ≥3 MADRS, ≥4 PANSS) symptoms. In patients with ≥3 depressive features and independent of treatment: MADRS remission (score ≤12) rate decreased with increasing severity (61–43%) and YMRS remission (score ≤12) was similar for mild and moderate patients (36–37%), but higher for severe (54%). In asenapine-treated patients, the MADRS remission rate was stable regardless of baseline depressive symptom severity (range 64–67%), whereas remission decreased with increasing severity with olanzapine (63–38%) and placebo (49–25%). Reduction in YMRS was significantly greater for asenapine compared with placebo at day 2 across the 3 severity cut-offs and continued to decrease throughout the treatment period. The difference between olanzapine and placebo was statistically significant in mild and moderate patients.

Limitations

Results are from post-hoc analyses.

Conclusions

These analyses support the validity of proposed DSM-5 criteria. They confirm that depressive features are frequent in bipolar patients with manic episodes. With increasing baseline severity of depressive features, treatment outcome was poorer with olanzapine and placebo, but remained stable with asenapine.  相似文献   
79.
Angiotropic large cell lymphoma is a rare neoplastic disorder associated with a high mortality. The hallmark of the disease is lymphoid proliferation confined to the intravascular compartment without local tissue or vessel wall infiltration [1]. This feature is so striking that the disease was originally thought to arise from endothelial tissue and early cases were described as malignant angioendotheliomatosis. However, application of immunohistochemical methods for detection of lymphoid markers such as the CD45 and CD20 cell surface markers has confirmed its lymphoid origin, usually of B-cell lineage [2]. Clinical manifestations of the disease are protean and are due to multifocal medium and small vessel occlusion by tumour cells [3]. Characteristic sites of involvement are skin and central nervous system and although an ante-mortem diagnosis can be made from a biopsy specimen, it is often unsuspected [4]. We present a case of angiotropic large B-cell lymphoma in a 74-year-old man who presented with urinary symptoms and had a neurological picture resembling subacute combined degeneration of the cord.  相似文献   
80.
OBJECTIVE: The authors sought to determine whether integrated mental health services or enhanced referral to specialty mental health clinics results in greater engagement in mental health/substance abuse services by older primary care patients. METHOD: This multisite randomized trial included 10 sites consisting of primary care and specialty mental health/substance abuse clinics. Primary care patients 65 years old or older (N=24,930) were screened. The final study group consisted of 2,022 patients (mean age=73.5 years; 26% female; 48% ethnic minority) with depression (N=1,390), anxiety (N=70), at-risk alcohol use (N=414), or dual diagnosis (N=148) who were randomly assigned to integrated care (mental health and substance abuse providers co-located in primary care; N=999) or enhanced referral to specialty mental health/substance abuse clinics (i.e., facilitated scheduling, transportation, payment; N=1,023). RESULTS: Seventy-one percent of patients engaged in treatment in the integrated model compared with 49% in the enhanced referral model. Integrated care was associated with more mental health and substance abuse visits per patient (mean=3.04) relative to enhanced referral (mean=1.91). Overall, greater engagement was predicted by integrated care and higher mental distress. For depression, greater engagement was predicted by integrated care and more severe depression. For at-risk alcohol users, greater engagement was predicted by integrated care and more severe problem drinking. For all conditions, greater engagement was associated with closer proximity of mental health/substance abuse services to primary care. CONCLUSIONS: Older primary care patients are more likely to accept collaborative mental health treatment within primary care than in mental health/substance abuse clinics. These results suggest that integrated service arrangements improve access to mental health and substance abuse services for older adults who underuse these services.  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