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   9927篇
  免费   560篇
  国内免费   101篇
耳鼻咽喉   117篇
儿科学   287篇
妇产科学   451篇
基础医学   1156篇
口腔科学   216篇
临床医学   1088篇
内科学   2197篇
皮肤病学   130篇
神经病学   610篇
特种医学   322篇
外科学   1497篇
综合类   207篇
现状与发展   1篇
一般理论   1篇
预防医学   469篇
眼科学   166篇
药学   706篇
  4篇
中国医学   85篇
肿瘤学   878篇
  2024年   30篇
  2023年   91篇
  2022年   186篇
  2021年   306篇
  2020年   206篇
  2019年   360篇
  2018年   355篇
  2017年   273篇
  2016年   304篇
  2015年   344篇
  2014年   438篇
  2013年   505篇
  2012年   675篇
  2011年   718篇
  2010年   454篇
  2009年   403篇
  2008年   548篇
  2007年   537篇
  2006年   490篇
  2005年   480篇
  2004年   425篇
  2003年   368篇
  2002年   374篇
  2001年   238篇
  2000年   215篇
  1999年   171篇
  1998年   68篇
  1997年   77篇
  1996年   63篇
  1995年   47篇
  1994年   55篇
  1993年   29篇
  1992年   98篇
  1991年   77篇
  1990年   77篇
  1989年   70篇
  1988年   56篇
  1987年   32篇
  1986年   40篇
  1985年   50篇
  1984年   31篇
  1983年   26篇
  1982年   19篇
  1981年   28篇
  1979年   17篇
  1977年   17篇
  1976年   12篇
  1975年   14篇
  1973年   13篇
  1972年   12篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Objective:  The purpose of the present study was to build a database of reference ranges of fetal nasal bone length (NBL) in a Chinese population. The accuracy rate of detecting Down syndrome was also analyzed using fetal NBL as a marker.
Methods:  The control group of fetuses included 342 normal singleton pregnancies with no chromosomal or congenital anomalies. The present study was a cross-section study and the control group was used to construct percentile values of NBL from 13 to 29 gestational weeks of age. Two-dimensional ultrasonography was used for the nasal bone studies. Measurements of NBL were collected and each fetus contributed a single value to the reference sample. During the study period, 14 fetuses with Down syndrome were examined. Measurement of fetal NBL was made during amniocentesis, with gestational age ranging from 13 to 19 weeks.
Results:  From 342 normal fetuses with gestational age ranging from 13 to 29 weeks, reference ranges of NBL were constructed. The reference ranges were constructed from the 100(1 − p)% reference range:     , where Ŷ  = 25 − exp(3.58 − 0.044 ×  t  + 0.0006 ×  t 2), with Ŷ being the fitted mean of regression model and t being gestational age (weeks). Using fetal NBL, the regression model was Pr (Down syndrome) = exp( W )/[1 + exp( W )], where W  = 0.62–4.80 × NBL (multiples of the median) in predicting Down syndrome. Fetal NBL was found to have a sensitivity and specificity of 0.78 and 0.78, respectively, in predicting Down syndrome in the second trimester of pregnancy.
Conclusions:  Fetal NBL measurement can provide a simple and useful algorithm to predict Down syndrome during the second trimester of pregnancy.  相似文献   
63.
Group B streptococcus infection in pregnancy   总被引:1,自引:0,他引:1  
Group B streptococcus (streptococcus agalactiae), a gram-positive coccus, is one of the major causes of maternal or neonatal severe infection and sepsis. Maternal infection associated with GBS includes acute chorioamnionitis, endometritis, and urinary tract infection.  相似文献   
64.
65.
66.
Deception detection can be of great value during the juristic investigation. Although the neural signatures of deception have been widely documented, most prior studies were biased by difficulty levels. That is, deceptive behavior typically required more effort, making deception detection possibly effort detection. Furthermore, no study has examined the generalizability across instructed and spontaneous responses and across participants. To explore these issues, we used a dual‐task paradigm, where the difficulty level was balanced between truth‐telling and lying, and the instructed and spontaneous truth‐telling and lying were collected independently. Using Multivoxel pattern analysis, we were able to decode truth‐telling versus lying with a balanced difficulty level. Results showed that the angular gyrus (AG), inferior frontal gyrus (IFG), and postcentral gyrus could differentiate lying from truth‐telling. Critically, linear classifiers trained to distinguish instructed truthful and deceptive responses could correctly differentiate spontaneous truthful and deceptive responses in AG and IFG with above‐chance accuracy. In addition, with a leave‐one‐participant‐out analysis, multivoxel neural patterns from AG could classify if the left‐out participant was lying or not in a trial. These results indicate the commonality of neural responses subserved instructed and spontaneous deceptive behavior as well as the feasibility of cross‐participant deception validation.  相似文献   
67.
Background: Prior studies have suggested a number of the subjective visual characteristics that help distinguish between spinal meningiomas and schwannomas on magnetic resonance imaging and computed tomography; however, objective quantification of the signal intensity can be useful information. This study assessed whether quantitative magnetic resonance imaging (MRI) signal intensity (SI) measurements could distinguish intradural-extramedullary schwannomas from meningiomas.Methods: From July 2019 to September 2021, 54 patients with intradural-extramedullary tumors (37 meningiomas and 17 schwannomas) underwent surgery, and tumors were verified pathologically. Defined regions of interest were used to quantify SI values on T1- (T1W) and T2-weighted images (T2W). Receiver operating characteristic curve analysis was used to obtain cutoff values and calculate the area under the curve (AUC), sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV).Results: Both Maximum (T2max) and mean (T2mean) T2W SI values demonstrated outstanding (AUC: 0.91) abilities to differentiate meningiomas from schwannomas with Se, Sp, PPV, and NPV values of 94.6%, 70.6%, 87.5%, and 85.7%, respectively, for T2max and 81.1%, 88.2%, 93.8%, and 68.2% for T2mean. The maximum SI value on contrast-enhanced T1W (T1CEmax) and the T2W tumor: fat SI ratio (rTF) demonstrated acceptable abilities (AUC: 0.73 and 0.79, respectively) to differentiate meningiomas from schwannomas with Se, Sp, PPV, and NPV values of 94.6%, 70.6%, 87.5%, and 85.7%, respectively, for T1CEmax and 81.1%, 88.2%, 93.8%, and 68.2% for rTF.Conclusions: Quantitative SI values (T2max, T2mean, T2min, T1CEmax, rTF) can be used to differentiate intradural-extramedullary schwannomas from meningiomas.  相似文献   
68.
69.
We present a case of histologically confirmed lipomatous meningioma, the first to our knowledge reported in Hong Kong. A 75‐year‐old woman presented to us with on and off dizziness for 1 month. Computed tomography (CT) of the brain showed an extra‐axial mass lesion containing fat and solid enhancing foci at her right frontal region. The definitive diagnosis could be made preoperatively. Postoperative histological examination of the tumour revealed the diagnosis of lipomatous meningioma. We have reviewed the literature and discussed the diagnostic clues, clinical presentation and pathology of this rare tumour.  相似文献   
70.
Asian American women's historically low breast cancer mortality rate has remained constant as rates decreased for all other races. From 2000 to 2004, a randomized controlled trial explored the Asian grocery store-based breast cancer education program's impact on Chinese, Filipino, Korean, and Vietnamese women (n?=?1,540). Women aged 40 and older and non-adherent for annual screening mammograms were more likely to schedule a mammogram after receiving the breast cancer education program than women randomized to the prostate cancer program (X 2?=?3.85, p?=?0.05). With the right program ingredients, late adopters of breast cancer screening can be prompted to change.  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