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   1425074篇
  免费   114102篇
  国内免费   3402篇
耳鼻咽喉   18447篇
儿科学   46742篇
妇产科学   41159篇
基础医学   202602篇
口腔科学   37993篇
临床医学   127030篇
内科学   288119篇
皮肤病学   33614篇
神经病学   118041篇
特种医学   54641篇
外国民族医学   464篇
外科学   213052篇
综合类   32833篇
现状与发展   3篇
一般理论   488篇
预防医学   110309篇
眼科学   31789篇
药学   99388篇
  1篇
中国医学   3369篇
肿瘤学   82494篇
  2021年   11070篇
  2019年   11814篇
  2018年   16798篇
  2017年   12844篇
  2016年   14437篇
  2015年   16231篇
  2014年   22838篇
  2013年   33739篇
  2012年   45859篇
  2011年   48527篇
  2010年   28475篇
  2009年   27332篇
  2008年   44825篇
  2007年   47394篇
  2006年   47923篇
  2005年   46413篇
  2004年   44297篇
  2003年   42299篇
  2002年   40772篇
  2001年   73552篇
  2000年   75105篇
  1999年   62085篇
  1998年   17187篇
  1997年   15600篇
  1996年   15717篇
  1995年   14917篇
  1994年   13532篇
  1993年   12678篇
  1992年   46297篇
  1991年   43822篇
  1990年   41876篇
  1989年   39932篇
  1988年   36540篇
  1987年   35681篇
  1986年   33163篇
  1985年   31612篇
  1984年   24012篇
  1983年   20209篇
  1982年   12287篇
  1981年   10832篇
  1979年   20859篇
  1978年   14670篇
  1977年   12186篇
  1976年   11443篇
  1975年   11705篇
  1974年   14062篇
  1973年   13629篇
  1972年   12701篇
  1971年   11555篇
  1970年   10991篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ninety-seven inpatients with tardive dyskinesia (average AIMS score = 13), the majority of whom were schizophrenic, were studied. Forty patients were Caucasian, and 57 were African-American. The APOE genotypes of these patients were compared to previously published genotypes of controls and with previously published studies of APOE genotypes in patients with schizophrenia. There were no significant differences in APOE allele frequencies comparing the African-American tardive dyskinesia population and the African-American control groups. In contrast, significant (< 0.05) P values were obtained comparing the Caucasian tardive dyskinesia population to the Caucasian controls, when comparing allele frequencies and genotypic frequencies. This study suggests that Caucasians bearing an APOE2 allele are at increased risk of developing tardive dyskinesia, whereas African-Americans are not. APOE genotype-specific risks of both tardive dyskinesia and Alzheimer's disease that vary across populations could be due to recruitment of patients or controls or could be due to modifying effects of differing genetic or environmental backgrounds. The mechanism by which the APOE2 allele increases risk of tardive dyskinesia is not known. Further information about the mechanisms of increased risk of tardive dyskinesia could result in stratification of prescribing practices weighing the costs of medications against the relative risk of side effects.  相似文献   
42.
43.
44.
Antipsychotics have been found to induce recurrent psychotic episodes lasting minutes to hours, mostly accompanied by oculogyric crisis (OGC). To characterize this side effect, antipsychotic-induced and postencephalitic OGCs that were reported in the literature were compared to find out common characteristics of OGCs and their associated symptoms. Both postencephalitic and antipsychotic-induced OGCs were found to occur late in the day and at regular intervals, and were associated with autonomic symptoms such as profuse sweating, facial flushing, transitory hypertension and difficulty in micturition. They were often associated also with transient psychiatric episodes: visual hallucinations and illusions, auditory hallucinations, delusions, catatonic phenomena, obsessive thoughts and panic attacks. These (OGC) characteristics will be useful in recognizing antipsychotic-induced psychiatric episodes. The associated psychiatric episodes were noted to recur occasionally also without OGC in a few postencephalic cases, and during gradual dose reduction or after a switch to a novel or low-potency antipsychotic in drug-induced cases. These findings suggest that episodes with the OGC characteristics but without OGC per se, may be less severe reactions to antipsychotic medication than those with OGC, and may represent manifestations of subclinical OGC.  相似文献   
45.
46.
47.
Background: Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.

Methods: In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded.

Results: The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion.  相似文献   

48.
49.
50.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  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