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   19021篇
  免费   1084篇
  国内免费   147篇
耳鼻咽喉   220篇
儿科学   502篇
妇产科学   664篇
基础医学   2071篇
口腔科学   534篇
临床医学   1567篇
内科学   3788篇
皮肤病学   379篇
神经病学   887篇
特种医学   724篇
外国民族医学   11篇
外科学   3350篇
综合类   341篇
现状与发展   2篇
一般理论   11篇
预防医学   1637篇
眼科学   545篇
药学   1753篇
中国医学   138篇
肿瘤学   1128篇
  2024年   17篇
  2023年   249篇
  2022年   778篇
  2021年   1120篇
  2020年   608篇
  2019年   758篇
  2018年   1022篇
  2017年   600篇
  2016年   627篇
  2015年   637篇
  2014年   895篇
  2013年   1037篇
  2012年   1513篇
  2011年   1656篇
  2010年   941篇
  2009年   679篇
  2008年   956篇
  2007年   966篇
  2006年   883篇
  2005年   851篇
  2004年   733篇
  2003年   679篇
  2002年   604篇
  2001年   139篇
  2000年   112篇
  1999年   95篇
  1998年   76篇
  1997年   73篇
  1996年   72篇
  1995年   64篇
  1994年   59篇
  1993年   50篇
  1992年   48篇
  1991年   56篇
  1990年   55篇
  1989年   46篇
  1988年   49篇
  1987年   46篇
  1986年   38篇
  1985年   38篇
  1984年   39篇
  1983年   36篇
  1982年   33篇
  1981年   23篇
  1980年   21篇
  1978年   16篇
  1977年   14篇
  1976年   17篇
  1974年   13篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Sixty eight infants and newborns were included in the present study being consisted of 55 cases with congenital anomalies and 13 cases of apparently healthy infants acting as controls. Three types of congenital anomaly cases were studied; 17 cases of microcephaly, 17 cases of cerebral palsy and 21 cases with jaundice. All serum samples were tested for cytomegalovirus IgM antibodies (CMV IgM) by microassay ELISA technique to explore the role of CMV infection in inducing congenital anomalies. Six out of the 68 serum samples were found to be positive for CMV IgM. Four of them were detected among the congenital cases (5 our to 55; 7.3%), while 2 cases were among the controls (2 out of 13; 15.4%). The microcephalic group showed 5.9% positivity (one out of 17). The jaundiced infants showed 14.3% positivity (3 out of 21), while all the cerebral palsy cases were negative for CMV IgM. Such a high percentage of CMV IgM in the control group may be attributed to asymptomatic infection, with liability for long term sequelae, particularly hearing loss or ocular abnormalities by 2 years of age. So, continuous follow-up of such asymptomatic cases is essential to control any possible congenital abnormality as early as possible.  相似文献   
42.
BACKGROUND: Monophosphoryl lipid-A (MLA) has a late window (24 hours) of cardioprotection against acute myocardial infarction. It is not known whether MLA, administered, 24 hours before surgery, attenuates intraoperative ventricular dysfunction "stunning" associated with aortic cross-clamping and reperfusion during elective cardiac surgery. We determined the dose-response relationship between MLA and ventricular function in a canine model of global myocardial stunning in the absence of necrosis. The role of expression of inducible heat shock protein 70 (HSP 70i) was also investigated. METHODS: Mongrel dogs (n = 32) were intravenously injected with either a vehicle solution or 3, 5, 10, 35 ug/kg MLA. Twenty four hours later, dogs were anesthetized and instrumented, in situ, to monitor the left ventricular performance (the slope of regression between stroke-work and end diastolic length). Tissue samples were obtained to determine HSP70i using immunoblot analysis. After a period of equilibration on cardiopulmonary bypass, the aortic cross-clamp was applied at normothermia for 30 minutes followed by 60 minutes of reperfusion. ATP and catabolites were determined in transmural myocardial biopsies. Triphenyl-tetrazolium chloride (TTC) staining was used to determine myocardial necrosis. RESULTS: MLA treatment did not alter myocardial contractility or ATP metabolism. Global ischemia resulted in about 50% depletion of ATP and remained depressed during reperfusion in all groups. MLA-treated hearts had improved functional recovery in a dose dependent-manner. Significant recovery was observed at the highest dose (35 ug/kg) compared to the control group. Immunoblot analysis demonstrated significant increase in HSP 70i in the MLA-treated hearts. CONCLUSIONS: MLA exhibits a delayed (24 hours) window of protection against myocardial stunning associated with aortic cross-clamping. HSP70i expression may play a role in MLA-mediated cardioprotection.  相似文献   
43.
Periictal diffusion-weighted imaging in a case of lesional epilepsy   总被引:8,自引:1,他引:7  
PURPOSE: Diffusion-weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period. METHODS: A periictal DWI study was performed on a 35-year-old patient during focal status epilepticus with repetitive prolonged focal motor seizures originating from a lesion in the right frontal lobe. DWI results were analyzed visually and by calculating apparent diffusion coefficient (ADC) maps. RESULTS: On DWI, a single area of signal increase (decrease in ADC) was found in the region of focal electrocorticographic seizures that was mapped intraoperatively. CONCLUSIONS: Ictal/postictal DWI may be a useful technique for seizure localization in patients with lesional epilepsy.  相似文献   
44.

Purpose

We attempted to determine how patients with an orthotopic bladder perceive the desire to void and the force achieved to evacuate the bladder.

Materials and Methods

A total of 24 men who had undergone post-cystectomy bladder substitution (ileocecal in 12, sigmoid in 6 and ileal in 6) was evaluated subjectively and objectively by pressure-flow study 1 to 3 years postoperatively.

Results

Desire to void was felt at the base of the penis or in the perineum by 20 men (83 percent). Abdominal pressure contributed to intra-reservoir pressure by 51 to 54 percent in ileocecal, 20 to 24 percent in sigmoid and 23 to 25 percent in ileal neobladders.

Conclusions

Patients perceive the desire to void when drops of urine leak into the proximal urethra from an overfilled neobladder. Urine is evacuated mainly by abdominal straining for ileal neobladders, mainly by contraction for sigmoid neobladders, and by approximately equal contributions of contraction and straining for ileocecal neobladders.  相似文献   
45.

Purpose

We determined if the behavior of germ cell tumors metastatic to the mediastinum is different from that of primary mediastinal germ cell tumors, a group known to have distinct clinical features.

Materials and Methods

A search of the computerized data base for germ cell tumors metastatic to the mediastinum at our university revealed 80 patients, 65 of whom underwent concomitant retroperitoneal lymph node dissection at mediastinal surgery.

Results

Of the patients 60 (75 percent) are free of disease, 14 (18 percent) died of cancer and 6 (8 percent) are living with disease. Mediastinal pathology included teratoma in 65 percent of the patients, cancer in 26 percent and fibrosis in 9 percent. Of the 65 patients who underwent retroperitoneal lymph node dissection 75 percent had teratoma, 15 percent had fibrosis and 10 percent had cancer. Mediastinal relapses after dissection were rare (4 of 80 patients).

Conclusions

Germ cell tumors metastatic to the mediastinum appear to behave similarly to those metastatic to the retroperitoneum. Primary mediastinal germ cell tumors have an entirely different clinical course. Teratoma is the predominant pathological type of post-chemotherapy germ cell cancer metastatic to the mediastinum.  相似文献   
46.
We retrospectively analyzed the prognostic significance of mixed chimerism and associated clinical parameters in 80 patients following unmanipulated allogenic stem cell transplantation. Chimerism studies were performed on marrow aspirates using fluorescent in situ hybridization and variable number tandem repeats techniques at day +30, day +90 and +12 months. The median overall survival (OS) was 24 months (range, 1-56 months). Mixed chimerism was found in 23, 28 and 14% of patients at day +30 (1 month), +90 (3 months), and +12 months, respectively. Day +30 chimerism studies failed to provide any prognostic information. Day +90 mixed chimeras (MC) had significantly higher relapse rates compared to day +90 complete chimeras (CC) at 6 months (P=0.03) and 18 months when compared to MC (P=0.03) following transplant. The median OS in day +90 MC and day+90 CC were, respectively (95% CI, 2-35 months), compared to 47 months (95% CI, 20-74 months) (P=0.02). In conclusion, chimerism studies on day +30 could be reserved for patients who fail to demonstrate engraftment. Day +90 MC had higher relapse rates and lower OS, and therefore may be considered for novel therapies and future studies.  相似文献   
47.
Diffuse neurological manifestations of preeclampsia are due to endothelial involvement that lead to ischemia, hemorrhage, or edema. We analyzed clinical and radiological features and the course of brainstem ischemic strokes in a preeclampsia patient. We report a case of severe preeclampsia in a 30-year-old woman who was admitted 10 hr after a vaginal delivery at home. The pregnancy was at 39 wk, with no prenatal care. At her admission, she was conscious, and she had tetraparesia, swinging deep tendon reflex testing, drowsiness, and dysarthria; the BP was at 160/100 mmHg and 4 + proteinuria; magnetic resonance imaging revealed brainstem ischemic stroke. The evolution was favorable with symptomatic treatment. The patient was discharged on the 16th day; 2 months later she had a normal recovery. Brainstem strokes are rare. They are frequently due to hemorrhage; sometimes, they can also be ischemic. Their course is favorable.  相似文献   
48.
BACKGROUND: Osteopenia of prematurity is a known source for morbidity in preterm infants. Premature infants have shown favorable outcomes in response to massage and physical activity. Whether such intervention can stimulate bone formation or decrease bone resorption is yet to be determined. OBJECTIVE: To test the hypothesis that massage combined with physical activity can stimulate bone formation and ameliorate bone resorption in premature infants. DESIGN/METHODS: A prospective double-blinded randomized trial was conducted at the Neonatal Intensive Care Unit of Ain Shams University in Cairo, Egypt. Thirty preterm infants (28 to 35 weeks' gestation) were randomly assigned to either control group (Group I, n=15) or intervention group (Group II, n=15). Infants in the intervention group received a daily protocol of combined massage and physical activity. Serum type I collagen C-terminal propeptide (PICP) and urinary pyridinoline crosslinks of collagen (Pyd) were used as indices for bone formation and resorption, respectively. PICP and Pyd were measured at enrollment and at discharge for all subjects. t-Test, ANOVA and linear regression analysis were used for statistical analyses. RESULTS: There was no difference between groups I and II in gestational age (32.1+/-1.8 vs 31.5+/-1.4 weeks) or birth weight (1.429+/-0.148 vs 1.467+/-0.132 g). In the control group, serum PICP decreased over time from 82.3+/-8.5 to 68.78+/-14.6 (p<0.01), while urinary Pyd increased from 447.7+/-282.8 to 744.9+/-373.6 (p<0.01) indicating decreased bone formation and increased bone resorption, respectively. In the intervention group, serum PICP increased over time from 62.5+/-13.8 to 73.84+/-12.9 (p<0.01). Urinary Pyd also increased over time from 445.7+/-266.5 to 716.8+/-301.8 (p<0.01). In a linear regression model including gestational age and intervention, serum PICP increased significantly in the intervention group (regression coefficient 18.8+/-4.6, p=0.0001) while urinary Pyd did not differ between groups (regression coefficient=5.6+/-114.3, p=0.961). CONCLUSIONS: A combined massage and physical activity protocol improved bone formation (PICP) but did not affect bone resorption (Pyd). Pyd increased over time in both groups, possibly due to continuous bone resorption and Ca mobilization.  相似文献   
49.
A prospective observational study was designed to evaluate the effect of the different techniques of hysterectomy on urinary and sexual function. One hundred and eighty-seven women aged 29-73 years and admitted for hysterectomy for various indications were recruited to the study. Women presenting primarily with major uterine prolapse and those requiring radical hysterectomy were excluded. Patients underwent one of four different techniques of hysterectomy: total abdominal, vaginal, laparoscopic or subtotal. All patients completed a standardised questionnaire addressing urinary and sexual symptoms and underwent urodynamic testing using the Lectromed 6000 System (Lectromed, Letchworth, Herts, UK) before and 6 months after surgery. Out of 187 women, 184 (98.4%) had completed data. Seventy-three patients (39%) had a total abdominal hysterectomy, 62 (34%) had vaginal, 38 (21%) had laparoscopic and 11 (6%) had subtotal hysterectomy. At 6 months after surgery, urinary symptoms occurred less frequently (P<0.01) and urodynamic studies remained unchanged. Moreover, patients reported significantly lower rates of stress incontinence (P=0.005), urgency (P=0.03) and deep dyspareunia (P<0.001) than before the operation, regardless of the hysterectomy technique used. The route of hysterectomy did not influence the outcome of surgery. We conclude that simple hysterectomy, whether performed abdominally, vaginally or laparoscopically, does not adversely affect urinary or sexual function at 6 months after surgery.  相似文献   
50.
BackgroundShared and divergent predictors of clinical severity across respiratory viruses may support clinical and community responses in the context of a novel respiratory pathogen.MethodsWe conducted a retrospective cohort study to identify predictors of 30‐day all‐cause mortality following hospitalization with influenza (N = 45,749; 2010‐09 to 2019‐05), respiratory syncytial virus (RSV; N = 24 345; 2010‐09 to 2019‐04), or severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2; N = 8988; 2020‐03 to 2020‐12; pre‐vaccine) using population‐based health administrative data from Ontario, Canada. Multivariable modified Poisson regression was used to assess associations between potential predictors and mortality. We compared the direction, magnitude, and confidence intervals of risk ratios to identify shared and divergent predictors of mortality.ResultsA total of 3186 (7.0%), 697 (2.9%), and 1880 (20.9%) patients died within 30 days of hospital admission with influenza, RSV, and SARS‐CoV‐2, respectively. Shared predictors of increased mortality included older age, male sex, residence in a long‐term care home, and chronic kidney disease. Positive associations between age and mortality were largest for patients with SARS‐CoV‐2. Few comorbidities were associated with mortality among patients with SARS‐CoV‐2 as compared with those with influenza or RSV.ConclusionsOur findings may help identify patients at greatest risk of illness secondary to a respiratory virus, anticipate hospital resource needs, and prioritize local prevention and therapeutic strategies to communities with higher prevalence of risk factors.  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