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   63491篇
  免费   4878篇
  国内免费   1739篇
耳鼻咽喉   833篇
儿科学   1187篇
妇产科学   2229篇
基础医学   8028篇
口腔科学   1161篇
临床医学   6817篇
内科学   11842篇
皮肤病学   1186篇
神经病学   3945篇
特种医学   2610篇
外国民族医学   6篇
外科学   8548篇
综合类   4187篇
现状与发展   7篇
一般理论   11篇
预防医学   3431篇
眼科学   1396篇
药学   5319篇
  20篇
中国医学   1675篇
肿瘤学   5670篇
  2023年   463篇
  2022年   1099篇
  2021年   2144篇
  2020年   1295篇
  2019年   1617篇
  2018年   1995篇
  2017年   1515篇
  2016年   1565篇
  2015年   2330篇
  2014年   2915篇
  2013年   3395篇
  2012年   4820篇
  2011年   4699篇
  2010年   2992篇
  2009年   2619篇
  2008年   3548篇
  2007年   3548篇
  2006年   3398篇
  2005年   3135篇
  2004年   2833篇
  2003年   2711篇
  2002年   2358篇
  2001年   1843篇
  2000年   1609篇
  1999年   1335篇
  1998年   551篇
  1997年   456篇
  1996年   417篇
  1995年   377篇
  1994年   348篇
  1993年   242篇
  1992年   711篇
  1991年   582篇
  1990年   531篇
  1989年   484篇
  1988年   421篇
  1987年   423篇
  1986年   355篇
  1985年   295篇
  1984年   229篇
  1983年   191篇
  1982年   114篇
  1981年   122篇
  1980年   99篇
  1979年   205篇
  1978年   161篇
  1977年   103篇
  1976年   110篇
  1975年   102篇
  1974年   99篇
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
991.
Meningiomas are slow‐growing neoplasms that recur locally. Their morphologic grading does not always correlate with patient outcome. We evaluated the status of several immunohistochemical markers with histopathologic parameters in various grades of meningioma.Eighty‐eight meningioma specimens were examined immunohistochemically to determine the status of Ki‐67, cyclin D1, epidermal growth factor receptor (EGFR), cyclooxygenase‐2 (COX‐2), vascular endothelial growth factor (VEGF), and bcl‐2. Several clinical and pathological parameters were investigated.Forty‐nine Grade I, 33 Grade II, and 6 Grade III meningiomas were observed. VEGF and Ki‐67 expression was correlated with higher tumor grade. The association between grade and other immunohistochemical markers expression was not significant. A correlation was observed between COX‐2 expression and invasiveness to the brain or adjacent soft tissue. Tumor recurrence was correlated with brain or adjacent soft tissue invasion. We also observed a relationship between VEGF level and COX‐2 expression, and they were both correlated with necrosis.Immunohistochemical evaluation of VEGF, COX‐2, and Ki‐67 expression can provide information regarding the behavior of meningiomas, particularly for cases in which histological grading is not straightforward.  相似文献   
992.
993.
Seventeen case series investigating the effects of omalizumab on patients with atopic dermatitis included patients whose pretreatment serum IgE was above 700 IU/ml, the upper inclusion limit specified in the product label. In all, 107 patients received omalizumab at doses of ≤375 mg every 2 weeks, which is recommended for patients with IgE <700 IU/ml. Among them, 87 improved in clinical symptoms and some did so after the first dose. Among these 87 patients, 35 and 12 had pretreatment serum IgE in the range 700–7000 IU/ml and 7000–121,000 IU/ml, respectively. These results not only suggest the pathogenic roles of IgE and the potential utility of omalizumab in atopic dermatitis, but also raise questions concerning the pharmacological mechanisms of omalizumab in patients with very high IgE levels. If omalizumab at regular doses is proven to treat patients with ultra high IgE (e.g. above 7000 IU/ml) effectively, it probably achieves this without neutralizing most of the IgE produced in the patients and downregulating the high-affinity IgE-Fc receptors on basophils and mast cells. Herein, we propose that a potential main pharmacological mechanism of omalizumab in patients with ultra high IgE is the ability of the rapidly accumulated IgE:omalizumab complexes to trap allergens.  相似文献   
994.
995.
Background The prevalence of depressive disorders is high among patients with skin disease. The PC‐SAD is a 37‐item self‐administered depression screening questionnaire that has been validated in dermatological patients. Objective The aim of this study was to develop and validate a brief depression severity instrument derived from the PC‐SAD that can be used to assess severity and monitor ongoing clinical course. Methods Two patient samples participated in the study: 72 adult dermatological inpatients and 73 adults attending six primary care practices. Psychiatric assessment included the Structured Clinical Interview for DSM‐IV and an 18‐item version of the PC‐SAD; moreover, dermatological patients completed the Patient Health Questionnaire depression scale (PHQ‐9), while primary care patients were administered the Montgomery‐Asberg Depression Rating Scale (MADRS). A subset of five PC‐SAD items showing the best psychometric properties were selected, and the reliability and validity of the resulting instrument (PC‐SAD5) were examined. Results The PC‐SAD5 showed satisfactory internal consistency in both samples. There was a high correlation between PC‐SAD5 and PHQ‐9 and MADRS scores. Multiple regression analysis revealed a gradient of PC‐SAD5 scores from patients with no mental disorder, those with milder forms of depression, to those with Major Depressive Disorder. Similar results were observed for the 18‐item version of the PC‐SAD. Conclusion The availability of valid and reliable continuous measures of depression severity derived from the PC‐SAD extends its field of application from depression screening to use as a follow‐up measure of depression severity in routine clinical practice. A validated very short instrument such as the PC‐SAD5 may have substantial clinical value.  相似文献   
996.
997.
Dynamic contrast‐enhanced MRI (DCE MRI) has been used to study tumor response to treatment for many years. In this study, the modified full width at half‐maximum (mFWHM), calculated from the wash‐in slope histogram, is proposed as a parameter for the evaluation of changes in tumor heterogeneity which respond to radiotherapy. Twenty‐five patients with brain tumors were evaluated and divided into the nonresponder group (n = 11) and the responder group (n = 14) according to the Response Evaluation Criteria in Solid Tumors (RECIST). All selected tumors were evaluated by mFWHM ratios of post‐ to pre‐therapy (the ratio was defined as the therapeutic mFWHM ratio, TMR). The changes in kurtosis of the histograms and the averaged Ktrans within a tumor were also calculated for comparison. The receiver operating characteristic analysis and Kaplan–Meier curves were used to examine the diagnosis ability. The TMR values were significantly higher in nonresponders than in responders (p < 0.001). When compared with the other two parameters, the proposed method also demonstrated better sensitivity and specificity. When adopting the TMR for the estimation of prognosis after therapy, there was a significant difference between the population survival curves. In conclusion, the derived mFWHM reflects tumor heterogeneity, and the ability to depict patient survival probability from TMR corresponds well with that from RECIST. The results reveal that, in brain tumors, progression may be exhibited not only by tumor size, but also by tumor heterogeneity. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
998.
999.
Low-intensity transcranial focused ultrasound (tFUS) has emerged as a non-invasive brain neuromodulation tool with high spatial specificity. Previous studies attributed tFUS-enhanced sensory performance to the ultrasound-induced inhibitory neural effects. However, to date there is no direct evidence validating the neural mechanism underlying ultrasound-mediated somatosensory enhancement. In this study, healthy human subjects (N = 9) were asked to perform tactile vibration frequency discrimination tasks while tFUS was directed onto the primary somatosensory cortex. During this task, we simultaneously recorded 64-channel electroencephalography (EEG) signals and investigated the brain responses at both EEG sensors and source domains by means of electrophysiological source imaging (ESI). The behavioral results indicated that the subjects' discrimination ability was improved by tFUS with an increased percentage of correct responses. EEG and ESI results revealed that tFUS neuromodulation was able to improve sensory discrimination capability through excitatory effects at the targeted sensory cortex.  相似文献   
1000.
We report the three‐dimensional ultrashort‐TE (3D UTE) and adiabatic inversion recovery UTE (IR‐UTE) sequences employing a radial trajectory with conical view ordering for bi‐component T2* analysis of bound water (T2*BW) and pore water (T2*PW) in cortical bone. An interleaved dual‐echo 3D UTE acquisition scheme was developed for fast bi‐component analysis of bound and pore water in cortical bone. A 3D IR‐UTE acquisition scheme employing multiple spokes per IR was developed for bound water imaging. Two‐dimensional UTE (2D UTE) and IR‐UTE sequences were employed for comparison. The sequences were applied to bovine bone samples (n = 6) and volunteers (n = 6) using a 3‐T scanner. Bi‐component fitting of 3D UTE images of bovine samples showed a mean T2*BW of 0.26 ± 0.04 ms and T2*PW of 4.16 ± 0.35 ms, with fractions of 21.5 ± 3.6% and 78.5 ± 3.6%, respectively. The 3D IR‐UTE signal showed a single‐component decay with a mean T2*BW of 0.29 ± 0.05 ms, suggesting selective imaging of bound water. Similar results were achieved with the 2D UTE and IR‐UTE sequences. Bi‐component fitting of 3D UTE images of the tibial midshafts of healthy volunteers showed a mean T2*BW of 0.32 ± 0.08 ms and T2*PW of 5.78 ± 1.24 ms, with fractions of 34.2 ± 7.4% and 65.8 ± 7.4%, respectively. Single‐component fitting of 3D IR‐UTE images showed a mean T2*BW of 0.35 ± 0.09 ms. The 3D UTE and 3D IR‐UTE techniques allow fast volumetric mapping of bound and pore water in cortical bone. Copyright © 2016 John Wiley & Sons, Ltd.  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