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   7873篇
  免费   292篇
  国内免费   20篇
耳鼻咽喉   134篇
儿科学   191篇
妇产科学   189篇
基础医学   1642篇
口腔科学   132篇
临床医学   669篇
内科学   1258篇
皮肤病学   355篇
神经病学   622篇
特种医学   259篇
外科学   1169篇
综合类   38篇
一般理论   1篇
预防医学   449篇
眼科学   228篇
药学   610篇
中国医学   7篇
肿瘤学   232篇
  2022年   45篇
  2021年   67篇
  2020年   52篇
  2019年   72篇
  2018年   80篇
  2017年   78篇
  2016年   106篇
  2015年   97篇
  2014年   168篇
  2013年   231篇
  2012年   319篇
  2011年   372篇
  2010年   222篇
  2009年   207篇
  2008年   304篇
  2007年   313篇
  2006年   300篇
  2005年   345篇
  2004年   342篇
  2003年   322篇
  2002年   342篇
  2001年   210篇
  2000年   186篇
  1999年   149篇
  1998年   84篇
  1997年   67篇
  1996年   56篇
  1995年   45篇
  1994年   49篇
  1993年   46篇
  1992年   98篇
  1991年   84篇
  1990年   100篇
  1989年   84篇
  1988年   76篇
  1987年   59篇
  1986年   68篇
  1985年   65篇
  1984年   49篇
  1983年   48篇
  1979年   49篇
  1935年   42篇
  1933年   51篇
  1931年   46篇
  1929年   50篇
  1926年   47篇
  1925年   42篇
  1923年   51篇
  1913年   47篇
  1912年   44篇
排序方式: 共有8185条查询结果,搜索用时 15 毫秒
1.
2.
Peacekeeping missions involve experiences that may impact the mental health of participating soldiers. However, research on the long-term mental health consequences of peacekeeping is sparse. The present study aimed to find the prevalence of mental health problems (MHPs), possible MHP predictors, and associations between predictors and MHPs in Norwegian peacekeepers 18–38 years after deployment to a United Nations peacekeeping mission. We used data from a cross-sectional, postdeployment survey of Norwegian peacekeepers who served in Lebanon between 1978 and 1998 (N = 10,605). Participants were assessed for posttraumatic stress disorder (PTSD); anxiety; depression; insomnia; alcohol misuse; drug misuse; and exposure to pre-, peri-, and postdeployment stressors. Logistic regressions were executed to explore key variables associated with MHPs. Total MHP prevalence was 15.1%, 95% CI [14.4, 15.8]. The estimates for specific disorders were 0.1% for drug misuse, 3.4% for alcohol misuse, 4.0% for depression, 6.2% for PTSD, 6.4% for anxiety, and 9.3% for insomnia. Postdeployment stressors, OR = 1.91, 95% CI [1.79, 2.04]; employment status, OR = 1.41, 95% CI [1.33, 1.48]; and traumatic exposure during deployment, OR = 1.11, 95% CI [1.09, 1.12], were positively related to PTSD, χ2(17, N = 8,568) = 1,791.299, p < .001. Similar patterns were found for the other MHPs. Considering that most participants (84.9%) reported low symptom levels, our findings challenge the widespread public perception that most peacekeepers have MHPs. Moreover, our results indicate that future peacekeepers should be prepared for challenges they may face not only during deployment but also in the years following their homecoming.  相似文献   
3.
BACKGROUND: 1Alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2) Vitamin D(3)] induces growth inhibition in squamous cell carcinoma (SCC) cell lines of the head and neck by arresting the cells in the G0/G1 phase of the cell cycle, probably due to an enhanced expression of p21, which could be demonstrated in other cell lines (JPPA, SCC9) before. In SCC25, a SCC cell line isolated from tongue, growth inhibition but no overexpression of p21 was detected. The retinoblastoma gene, as a direct target of G1 cyclin-CDK complexes, showed an obvious shift from the hyperphosphorylated to the hypophosphorylated form under 1,25(OH)(2)Vitamin D(3), which indicates that the growth inhibition takes place in the G0/G1 phase. To explore the possible pathway of growth inhibition in SCC25 we investigated other cell cycle inhibitors (p18, p19, p27). METHODS: Synchronized cells were treated with 1,25(OH)(2)Vitamin D(3) over 96 h. The cell cycle status and expression of cell cycle-regulating proteins was determined by fluorescence-activated cell sorting (FACS) and Western blotting. An overexpression of p18 in 1,25(OH)(2)Vitamin D(3) vs. ethanol-treated cells was determined until 30 h in SCC25. No influence was detectable on the expression of p27 and p19. CONCLUSION: One mechanism by which 1,25(OH)(2)Vitamin D(3) controls cell growth might be the upregulation of p21. As p21 was unsusceptible to 1,25(OH)(2)Vitamin D(3) in SCC25, other inhibiting proteins were necessary to be tested. The proven upregulation of p18 seems to be the responsible step for growth inhibition of 1,25(OH)(2)Vitamin D(3) in SCC25.  相似文献   
4.
BACKGROUND: The efficacy of nasal continuous positive airway pressure (nCPAP) as a prophylactic method for preventing cardiopulmonary complications after major vascular surgery has not been investigated. PATIENTS/METHODS: In a prospective randomized trial, 204 patients undergoing elective midline laparotomy for vascular surgery were randomized to receive standard therapy ( n=105) or additional prophylactic nCPAP ( n=99) for the first postoperative night. Postoperative oxygenation, incidence of severe cardiac, and pulmonary complications, length of intensive care surveillance and length of total postoperative hospital stay (LOS) were compared. RESULTS: Prophylactic nCPAP significantly reduced the number of patients with severe oxygenation disturbances defined as paO(2) < 70 mmHg with FiO(2) > or = 0.7 (5 versus 17, P=.01). There were no differences with respect to death, cardiac and pulmonary complications, length of intensive care surveillance or LOS. CONCLUSION: Prophylactic 12 h nCPAP significantly reduces the occurrence of postoperative oxygenation disturbances but has no effect on cardiac or pulmonary complications, need for intensive care, LOS or mortality after major vascular surgery.  相似文献   
5.
6.
Peripheral immune responses can be sensitive indicators of disease pathology. We evaluated the autoimmune reactions to endocrine (insulin) and astrocytical (S100B) biomarkers in the blood sera of 26 Parkinson's disease (PD) patients compared with controls by using ELISA. We found a statistically significant increase of the autoimmune responses to both antigens in PD patients compared with controls with a mean increase of 70% and 50% in the autoimmune reactions towards insulin and S100B, respectively. Heterogeneity of the immune responses observed in patients may reflect the modulating effect of multiple variables associated with neurodegeneration and also changes in the basic mechanisms of individual autoimmune reactivity. We did not detect any pronounced immune reactions towards insulin amyloid fibrils and oligomers in PD patients, indicating that an amyloid-specific conformational epitope is not involved in immune recognition of this amyloid type, while sequential epitope of native insulin is hidden within the amyloid structures. Immune reactions towards S100B and insulin may reflect the neurodegenerative brain damaging processes and impaired insulin homeostasis occurring in PD.  相似文献   
7.
Migraine is considered to be a functional neurological disorder. In classical migraine (headache associated with prodromal visual field disturbances) and migraine accompagnée (headache associated with transient neurological symptoms), disturbances of cerebral blood flow and amine metabolism are thought to be pathogenetic factors. However, conventional methods of neuroimaging (CAT, NMR) usually do not yield any pathological findings in patients. Since 123I-iodoamphetamine (123I-IMP) crosses the intact blood brain barrier, 123I-IMP-SPECT is used for the assessment of cerebral perfusion in various neurological diseases, including functional disorders. 123I-IMP-SPECT was performed on 5 patients with classical migraine and 18 patients with migraine accompagnée. At the time of investigation, all patients were symptom-free. Cerebral blood flow was decreased in all patients with migraine accompagnée, and often corresponded to the site of headache as well as to the topography of transient neurological symptoms. This reduction was most obvious in a patient with persisting neurological symptoms. Most patients with classical migraine, however, did not show any alteration of cerebral perfusion. It appears that migraine--and in particular migraine accompagnée--is characterized by a permanent alteration not only of cerebral blood flow but also of neuronal activity. Migraine attacks may occur in connection with exacerbations of preexisting metabolic alterations.  相似文献   
8.
Chemically distinct rat olivocochlear neurons.   总被引:6,自引:0,他引:6  
We have produced a neurochemical map of the cell bodies of origin of the cochlear efferent terminals in rat by combining glutamic acid decarboxylase (GAD), choline acetyltransferase (ChAT), or calcitonin gene-related peptide (CGRP) immunocytochemistry with retrograde transport of horseradish peroxidase. The locations of cochlear efferent cell bodies are in general agreement with the medial and lateral systems described by White and Warr (J. Comp. Neurol. 219:203-214, 1983) with some minor modifications. The lateral system consists of at least two pools of chemically distinct neurons located within the lateral superior olive (LSO) ipsilateral to the injected cochlea. One pool immunostains with an antibody to GAD while the other immunostains with antibodies to ChAT and to CGRP. The medial efferent system consists of periolivary neurons that are almost exclusively large and ChAT-positive but CGRP-negative. They are located both ipsilateral and contralateral to the cochlea they project to. There are a few GAD-positive small neurons in the medioventral and rostral periolivary regions that project ipsilaterally, but these may prove tobe ectopic neurons. The ipsilateral lateroventral periolivary region (LVPO) contains some efferent neurons, all of which are ChAT-positive but CGRP-negative. Additional cochlear efferent neurons, some of which are ChAT-positive and others GAD-positive, are present within and immediately dorsal to the fiber capsule surrounding the medial limb, and to a lesser extent the lateral limb, of the ipsilateral LSO. Not all GAD-positive or ChAT-positive olivary cells project to the cochlea. We have complemented the results in the brainstem by demonstrating two immunocytochemically distinct populations of efferent terminals in the cochlea simultaneously, one CGRP-positive and the other GAD-positive. Approximately equal numbers of boutons immunoreactive for both markers are present beneath inner hair cells throughout the entire length of the cochlea. Surprisingly high numbers of GAD-positive and CGRP-positive boutons are also present on outer hair cells, with each class having its spatially and morphologically distinct features. The lack of CGRP-positive periolivary cells that are retrogradely labeled by cochlear injections of HRP suggests that the lateral olivocochlear system sends projections to outer hair cells. Our results raise questions about species differences in the organization of targets of the lateral and medial olivocochlear systems.  相似文献   
9.
A survey of 402 normal subjects (203 men, 199 women) was conducted to assist in distinguishing potential differences in norms of hand strength. Norm data had previously been collected from mixed occupational groups, but in the present study it was hypothesised that people involved in heavy manual work on a daily basis might possess greater hand strength than others. The volunteers were adults working in industry and agriculture; they were subdivided into occupational categories. Measurements of grip, key and palmar pinch using the Jamar dynamometer and B and L pinch gauge were collected, using the protocol described by Mathiowetz. Volunteers also rated their individual hand strength job requirements subjectively. Mean values were established with regard to age, sex, dominance, occupational group and subjective rating. Significant differences were found with regard to age and sex but not to dominance; there was no evidence of differences between occupational groups or between subjective rating and individual scoring, i.e. volunteers who perceived their job as requiring a high degree of strength did not achieve higher test measurements than others. A high interrater reliability was demonstrated when comparing these follow-up measurements with the original data. It was concluded that, for clinical and rehabilitative purposes, therapists can interpret assessment of outcome most accurately by comparing patients' results with the existing norm data.  相似文献   
10.
Conventional radiographs do not always make it possible to confirm a diagnosis of ischemic necrosis of the lunate in the early stages of disease. For these doubtful cases MRI is justifiable in addition, to diagnose or to rule out ischemic necrosis of the lunate.  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