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   14738篇
  免费   818篇
  国内免费   132篇
耳鼻咽喉   147篇
儿科学   416篇
妇产科学   277篇
基础医学   1866篇
口腔科学   457篇
临床医学   1262篇
内科学   3287篇
皮肤病学   409篇
神经病学   1594篇
特种医学   633篇
外国民族医学   3篇
外科学   1963篇
综合类   129篇
一般理论   3篇
预防医学   790篇
眼科学   243篇
药学   1084篇
  1篇
中国医学   29篇
肿瘤学   1095篇
  2023年   71篇
  2022年   162篇
  2021年   354篇
  2020年   187篇
  2019年   256篇
  2018年   299篇
  2017年   216篇
  2016年   269篇
  2015年   310篇
  2014年   424篇
  2013年   539篇
  2012年   881篇
  2011年   896篇
  2010年   515篇
  2009年   428篇
  2008年   787篇
  2007年   795篇
  2006年   743篇
  2005年   762篇
  2004年   674篇
  2003年   604篇
  2002年   559篇
  2001年   485篇
  2000年   504篇
  1999年   400篇
  1998年   152篇
  1997年   147篇
  1996年   150篇
  1995年   128篇
  1994年   133篇
  1993年   103篇
  1992年   307篇
  1991年   248篇
  1990年   244篇
  1989年   204篇
  1988年   179篇
  1987年   159篇
  1986年   169篇
  1985年   159篇
  1984年   115篇
  1983年   80篇
  1982年   61篇
  1981年   62篇
  1980年   53篇
  1979年   90篇
  1977年   48篇
  1974年   47篇
  1973年   47篇
  1972年   67篇
  1971年   49篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
PURPOSE: The aim of this prospective study was to determine whether sonography with a hydration test to induce diuresis can be used to reliably differentiate between excretory renal obstruction and renal sinus cysts. METHODS: We performed sonographic examination of all patients diagnosed with minimal or moderate obstruction of the intrarenal collecting system or renal sinus cysts on the basis of excretory urography, CT, or both between September 1, 1998, and October 31, 1999. The largest fluid-filled structures in the renal sinus were sonographically measured before and after each patient ingested 1.5 l of water. Cases in which the maximum diameters of the largest anechoic structures increased by at least 10% after hydration were diagnosed with excretory renal obstruction. The sonographic diagnoses were compared with the final diagnoses on excretory urography, CT, or both. RESULTS: Both kidneys were affected in 16 of the 36 patients examined, for a total of 52 kidneys. The sonographic diagnosis was consistent with the results of urography or CT in 48 (92%) of the 52 kidneys. The sonographic approach had a specificity of 92% and a sensitivity of 93% for the diagnosis of excretory renal obstruction, with only 1 false-negative and 3 false-positive results. CONCLUSIONS: When used with the stimulated diuresis test, sonography can reliably distinguish between excretory renal obstruction and renal sinus cysts and can be used as an alternative to other imaging techniques such as urography.  相似文献   
992.
BACKGROUND: The comparatively high acquisition costs of the newer antipsychotic medications have caused the mental health community to look closely at their potential benefits. OBJECTIVE: The purpose of this study was to perform a naturalistic analysis of changes in mental health service utilization, economic costs, and clinical outcomes after the initiation of olanzapine therapy for psychotic symptoms in an indigent patient population from a large county-operated mental health care system. METHODS: This was a prospective, uncontrolled investigation using a mirror-image cohort design. All captured costs from patients who began olanzapine therapy between November 1, 1996, and April 30, 1998, were analyzed in an intent-to-treat fashion to compare resource utilization in the 12 months immediately before and after the intervention. Clinical function was assessed at baseline and 6 months using the Positive and Negative Syndrome Scale (PANSS). In a subgroup analysis, the baseline characteristics of patients who completed 12 months of olanzapine treatment were compared with those of patients who (1) changed medication or (2) changed pay or source or were lost to follow-up. RESULTS: One hundred eighty-nine patients were started on olanzapine treatment during the 18-month study entry phase. Patients were primarily male (63.5%) and had a mean age of 35.9 years. Most (66.3%) had a formal diagnosis of thought disorder. Fifty-six patients received olanzapine for 12 consecutive months, and 22 were switched to other psychotropic medications. Of the remaining 111 patients, 70 changed payors (ie, qualified for Medicaid), and 41 were lost to follow-up. In the subgroup analysis, patients who completed 12 months of treatment (ie, responders) had significantly lower mean PANSS total scores at baseline compared with those who changed payors or were lost to follow-up (P = 0.047), and were significantly more likely to have a formal diagnosis of thought disorder (P = 0.039). Responders demonstrated a significant reduction in PANSS total and negative subscale scores at 6-month follow-up (both measures, P < 0.001). In the intent-to-treat analysis of resource utilization in all patients with complete data sets (n = 78), hospitalization costs and crisis costs decreased significantly during the 12-month follow-up period (P = 0.003 and P = 0.009, respectively), and both outpatient and medication costs increased significantly (P = 0.035 and P < 0.001, respectively). Overall, the change in total annual resource utilization during the 12 months after initiation of olanzapine was not statistically significant (mean decrease per patient, $1,991; 95% CI, -$5,258 to $1,122). CONCLUSIONS: Initiation of olanzapine therapy was associated with favorable clinical outcomes in this population, particularly in patients with a formal diagnosis of thought disorder. Overall, there was a cost shift away from hospital and crisis costs toward medication and outpatient services costs. The decline in total resource utilization was not statistically significant, although it may be of practical importance.  相似文献   
993.
994.
995.
In the present high-resolution electroencephalographic (EEG) study, we computed event-related desynchronization and synchronization (ERD/ERS) of alpha (about 10 Hz) and beta (about 20 Hz) rhythms in association with the execution (with visual feedback) and observation of brisk unilateral right and left aimless finger movements. A first scope was to test the topographical "functional equivalence" of cortical rhythmicity related to movement execution and observation, which would represent an ideal cortical observation/execution matching system. A second scope was to evaluate the hypothesis of a left or right hemisphere prevalence of the cortical rhythmicity related to the movement observation compared to the movement execution. EEG (128 electrodes) was recorded in 10 healthy right-handed volunteers. Surface Laplacian estimation spatially enhanced EEG data over a MRI-constraint head model. Under both conditions, ERD peaked during the movement execution or observation and was replaced by a ERS "rebound" or "recovery," which peaked during the postevent period. Topographical results are in favor of a "functional equivalence" (i.e., similar ERD/ERS values in magnitude and timing) of alpha and beta rhythmicity in central scalp regions overlying premotor/primary sensorimotor cortex. On the contrary, the functional equivalence of alpha rhythmicity was negligible (i.e., different ERD/ERS values in magnitude and timing) in parietal-occipital scalp regions overlying posterior parietal and parieto-occipital cortex, which could be the neural substrate to distinguish among the own motor intensions and others' aimless movements (i.e., visuomotor transformation integrated with sensorimotor, postural, and kinematics representations). Finally, the pattern of hemispherical cortical rhythmicity did not support a "simple concentration" of movement observation functions in the left or right hemisphere.  相似文献   
996.
997.
OBJECTIVE: The present study was undertaken to evaluate the possible occurrence of immunological abnormalities in thalassaemia major patients treated with deferiprone (L1). METHODS: Longitudinal observational cohort study. RESULTS: The absolute number of CD8+ lymphocytes was high and the CD4/CD8 ratio low before L1 treatment; these parameters returned to normal after 3 months of L1 treatment. TNF-alpha, IL-2 and IL-2sRalpha were elevated before L1 treatment (11.83 +/- 1.75, 11.75 +/- 3.91, 1,409 +/- 621 pg/ml, respectively), while IL-6 was normal (2.58 +/- 0.79 pg/ml). After 12 months of treatment, IL-10 was higher than in previous periods, although always within the normal range. TNF-alpha, IL-2 and IL-2sRalpha returned to normal after 12, 6, and 3 months of L1 treatment, respectively.  相似文献   
998.
999.
Well-fitted dentures prevent hyperplasic lesions, provide chewing efficiency and promote patient's comfort. Several factors may affect final adaptation of dentures, as the type of the acrylic resin, the flask cooling procedure and the water uptake. This investigation evaluated the effect of water storage and two different cooling procedures [bench cooling (BC) for 2 h; running water (RW) at 20 degrees C for 45 min] on the final adaptation of denture bases. A heat-cured acrylic resin (CL, Clássico, Clássico Artigos Odontológicos) and two microwave-cured acrylic resins [Acron MC, (AC) GC Dent. Ind. Corp.; Onda Cryl (OC), Clássico Artigos Odontológicos] were used to make the bases. Adaptation was assessed by measuring the weight of an intervening layer of silicone impression material between the base and the master die. Data was submitted to ANOVA and Tukey's test (0.05). The following means were found: (BC) CL=0.72 +/- 0.03 a; AC=0.70 +/- 0.03 b; OC=0.76 +/- 0.04 c//(RW) CL= 1.00 +/- 0.11 a; AC=1.00 +/- 0.12 a; OC=0.95 +/- 0.10 a. Different labels join groups that are not statistically different (P > 0.05). Comparisons are made among groups submitted to the same cooling procedure (BC or RW). The conclusions are: interaction of type of material and cooling procedure had a statistically significant effect on the final adaptation of the denture bases (P < 0.05); water storage was not detected as a source of variance (P > 0.05) on the final adaptation.  相似文献   
1000.
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