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   13764篇
  免费   1030篇
  国内免费   38篇
耳鼻咽喉   183篇
儿科学   355篇
妇产科学   363篇
基础医学   1727篇
口腔科学   231篇
临床医学   1476篇
内科学   2695篇
皮肤病学   97篇
神经病学   1244篇
特种医学   475篇
外科学   2187篇
综合类   174篇
一般理论   13篇
预防医学   1222篇
眼科学   846篇
药学   696篇
中国医学   9篇
肿瘤学   839篇
  2023年   64篇
  2022年   126篇
  2021年   311篇
  2020年   160篇
  2019年   235篇
  2018年   335篇
  2017年   243篇
  2016年   239篇
  2015年   343篇
  2014年   450篇
  2013年   636篇
  2012年   955篇
  2011年   1016篇
  2010年   557篇
  2009年   496篇
  2008年   904篇
  2007年   904篇
  2006年   933篇
  2005年   906篇
  2004年   864篇
  2003年   797篇
  2002年   775篇
  2001年   147篇
  2000年   105篇
  1999年   162篇
  1998年   148篇
  1997年   132篇
  1996年   103篇
  1995年   107篇
  1994年   105篇
  1993年   84篇
  1992年   92篇
  1991年   75篇
  1990年   81篇
  1989年   74篇
  1988年   65篇
  1987年   77篇
  1986年   64篇
  1985年   82篇
  1984年   92篇
  1983年   73篇
  1982年   88篇
  1981年   104篇
  1980年   84篇
  1979年   53篇
  1978年   49篇
  1977年   32篇
  1976年   35篇
  1975年   28篇
  1974年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
GM1 ganglioside is believed to be important in promoting the recovery of neurons from injury. The present study assesses the ability of GM1 to repair or prevent the damage of dopamine neurons caused by the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Treatment of mesencephalic cell cultures with 2.5 μM MPP+ resulted in the loss of 30% of tyrosine hydoxylase (TH) immunoreactive neurons. In contrast, cultures administered 100 μM GM1 ganglioside for 3 days after toxin treatment contained nearly control numbers of TH+ neurons (97%). This reparative effect of GM1 was reflected in parallel increases in TH enzyme activity, dopamine and dopac levels. Cultures sustaining greater insult from higher doses of MPP+ (5.0–10.0 μM) did not benefit from ganglioside treatment, suggesting that rescue by GM1 depended on the degree of initial damage to cells. Moreover, the timing of ganglioside treatment was critical; pretreatment with GM1 alone did not prevent or attenuate the damage caused by subsequent incubation in 2.5 μM MPP+.  相似文献   
52.
A crescentic osteotomy of the first metatarsal is unstable during the preliminary healing stage. The authors present a modification in the direction of the cut of the osteotomy. This alteration increases stability at the first metatarsal base.  相似文献   
53.
54.
The Central Arkansas Veterans Healthcare System (CAVHS) spends $1 million annually on occupational illnesses and injuries. To address the problem of injuries among hospital employees, a retrospective case-control study was conducted to examine select risk factors for work-related injuries (WRI) among CAVHS employees. Study methods included a review of employee health charts and computer and manual databases from 1997 to 2002 (N = 2,050). The researchers found that WRI increased with age; WRI occurred more often in women than in men; WRI was greater among maintenance and custodial staff compared to direct caregivers, and less among clerical staff; WRI occurred less often in part-time than full-time staff; and WRI increased with increasing body mass index. Developing standards, guidelines, and policies for preplacement screening, preventive measures, training, and education may help to minimize WRI and associated costs.  相似文献   
55.

Background  

Late stage cancer malignancies may result in severe skeletal muscle wasting, fatigue and reduced quality of life. Resistance training may attenuate these derangements in cancer patients, but how this hypertrophic response relates to normal muscle adaptations in healthy subjects is unknown. Here, we determined the effect of resistance training on muscle mass and myosin heavy chain (MHC) isoform composition in plantaris muscles from tumor-bearing (TB) rats.  相似文献   
56.
57.
Gender differences in informal caring   总被引:1,自引:0,他引:1  
Men have hitherto largely been invisible in research on informal care. This paper examines gender differences in informal caring, focusing on gender differences according to the relationship between the carer and care-recipient and the location of caring. The paper uses secondary analysis of the 1990–91 General Household Survey, which identified over 2700 adults as informal carers. Four per cent of men and women provide care for someone living in the same household. More women than men, 13% compared with 10%, provide care for someone living in another household. Men carers are less involved in care provision than women, providing fewer hours of care each week, and are less likely to be the main carer. However, gender differences are most marked among married carers, apart from those caring for their spouse, and least among unmarried carers. Married men can often rely on their wives to perform caring roles rather than performing them personally. Women carers are more likely to provide personal care than men carers, but the gender difference is least among those caring for their spouse or for disabled children. Cross-sex personal care is performed within the marital relationship and by parents caring for disabled children, but seldom by adult children caring for their parents or in more distant caring relationships. Evidence of cross-sex taboos in giving personal care is largely restricted to care provided in another household. Since the majority of elderly people in need of care are women, such cultural taboos may reinforce the pressure on mid-life women to care for mothers and mothers-in-law.  相似文献   
58.
BACKGROUND: The purpose of this paper is to use demographic and clinical data from a large diverse group of outpatients diagnosed with non-psychotic major depression to investigate the validity of the DSM-IV concept of melancholic depression. METHODS: Baseline clinical and demographic data were collected on 1500 outpatients (1456 of whom melancholia could be determined) with non-psychotic major depressive disorder (MDD) participating in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Depressive symptom severity was assessed by clinical telephone interview using the 17-item Hamilton Rating Scale for Depression (HRS-D17) and the 30-item Inventory of Depressive Symptomatology (IDS-C30). The types and degrees of concurrent psychiatric symptoms were measured using a self report, the Psychiatric Diagnostic Screening Questionnaire (PDSQ), by recording the number of items relevant to each diagnostic category endorsed by study participants. RESULTS: Adjusting for severity of depression (as measured by the total HRS-D17 scores), no differences were found in the rate of melancholic depression by race, marital status, education, employment status, family history of depression, primary care versus specialty care, monthly income, and degree of psychiatric and medical co-morbidity. Melancholic depression was significantly more likely in men than women. Melancholic depression after adjustment for severity was associated with a slightly younger age at study entry, as well as with greater illness severity, and slightly shorter duration of current episode. Hispanic ethnicity was associated with lower melancholic depression rates at the .06 level of significance. CONCLUSIONS: Among outpatients with MDD, melancholic features were less likely in Hispanic patients, but more likely in slightly younger patients and in men. Melancholic features were also related to a slightly shorter current episode. These findings are consistent with the notion that external socio-demographic factors do not play an important role in the pathophysiology of melancholic depression.  相似文献   
59.
Three years after receiving a Baerveldt tube implant for neovascular glaucoma, a 50-year-old man presented to the Wills Eye Hospital Glaucoma Service with pain and decreased vision in his left eye. On examination, a 4-0 nylon ripcord suture was seen to have migrated posteriorly through the pupil and in front of the intraocular lens. The distal end of the suture was not seen on dilated indirect ophthalmoscopic examination or by standard B-scan ultrasonography. Ultrasound biomicroscopy examination was performed, and the distal end of the suture was found to lie just anterior to the pars plana. Careful removal of the suture was performed intraoperatively through two paracentesis incisions using Kelman forceps. Posterior ripcord migration is a rare complication after glaucoma drainage implant surgery, and ultrasound biomicroscopy imaging may be helpful in determining its proper management.  相似文献   
60.
Background: Magnetic resonance neurography (MRN) is an imaging method by which nerves can be selectively highlighted. Using commercial software, the authors explored a variety of approaches to develop a three-dimensional volume-rendered MRN image of the entire brachial plexus and used it to evaluate the accuracy of infraclavicular block approaches.

Methods: With institutional review board approval, MRN of the brachial plexus was performed in 10 volunteer subjects. MRN imaging was performed on a GE 1.5-tesla magnetic resonance scanner (General Electric Healthcare Technologies, Waukesha, WI) using a phased array torso coil. Coronal STIR and T1 oblique sagittal sequences of the brachial plexus were obtained. Multiple software programs were explored for enhanced display and manipulation of the composite magnetic resonance images. The authors developed a frontal slab composite approach that allows single-frame reconstruction of a three-dimensional volume-rendered image of the entire brachial plexus. Automatic segmentation was supplemented by manual segmentation in nearly all cases. For each of three infraclavicular approaches (posteriorly directed needle below midclavicle, infracoracoid, or caudomedial to coracoid), the targeting error was measured as the distance from the MRN plexus midpoint to the approach-targeted site.

Results: Composite frontal slabs (coronal views), which are single-frame three-dimensional volume renderings from image-enhanced two-dimensional frontal view projections of the underlying coronal slices, were created. The targeting errors (mean +/- SD) for the approaches-midclavicle, infracoracoid, caudomedial to coracoid-were 0.43 +/- 0.67, 0.99 +/- 1.22, and 0.65 +/- 1.14 cm, respectively.  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