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   1035篇
  免费   74篇
  国内免费   36篇
耳鼻咽喉   3篇
儿科学   35篇
妇产科学   17篇
基础医学   159篇
口腔科学   9篇
临床医学   121篇
内科学   136篇
皮肤病学   21篇
神经病学   141篇
特种医学   76篇
外科学   102篇
综合类   34篇
一般理论   1篇
预防医学   132篇
眼科学   41篇
药学   80篇
中国医学   1篇
肿瘤学   36篇
  2023年   7篇
  2021年   14篇
  2020年   19篇
  2019年   19篇
  2018年   23篇
  2017年   18篇
  2016年   27篇
  2015年   24篇
  2014年   38篇
  2013年   49篇
  2012年   58篇
  2011年   51篇
  2010年   37篇
  2009年   24篇
  2008年   40篇
  2007年   55篇
  2006年   38篇
  2005年   51篇
  2004年   35篇
  2003年   29篇
  2002年   28篇
  2001年   22篇
  2000年   34篇
  1999年   23篇
  1998年   19篇
  1997年   23篇
  1996年   22篇
  1995年   20篇
  1994年   15篇
  1993年   9篇
  1992年   25篇
  1991年   22篇
  1990年   18篇
  1989年   11篇
  1988年   20篇
  1986年   13篇
  1985年   17篇
  1984年   8篇
  1983年   7篇
  1982年   13篇
  1979年   9篇
  1978年   6篇
  1977年   7篇
  1976年   6篇
  1975年   7篇
  1974年   11篇
  1973年   6篇
  1971年   8篇
  1970年   10篇
  1968年   7篇
排序方式: 共有1145条查询结果,搜索用时 15 毫秒
61.
Genetic and hormonal factors have been suggested to influence human sexual orientation. Previous studied proposed brain differences related to sexual orientation and that these follow cross‐sex shifted patterns. However, the neurobiological correlates of sexual orientation and how genetic factors relate to brain structural variation remains largely unexplored. Using the largest neuroimaging‐genetics dataset available on same‐sex sexual behavior (SSB) (n = 18,645), we employed a data‐driven multivariate classification algorithm (PLS) on magnetic resonance imaging data from two imaging modalities to extract brain covariance patterns related to sex. Through analyses of latent variables, we tested for SSB‐related cross‐sex shifts in such patterns. Using genotype data, polygenic scores reflecting the genetic predisposition for SSB were computed and tested for associations with neuroimaging outcomes. Patterns important for classifying between males and females were less pronounced in non‐heterosexuals. Predominantly in non‐heterosexual females, multivariate brain patterns as represented by latent variables were shifted toward the opposite sex. Complementary univariate analyses revealed region specific SSB‐related differences in both males and females. Polygenic scores for SSB were associated with volume of lateral occipital and temporo‐occipital cortices. The present large‐scale study demonstrates multivariate neuroanatomical correlates of SSB, and tentatively suggests that genetic factors related to SSB may contribute to structural variation in certain brain structures. These findings support a neurobiological basis to the differences in human sexuality.  相似文献   
62.
Global cerebral hypoperfusion may be involved in the aetiology of brain atrophy; however, long-term longitudinal studies on this relationship are lacking. We examined whether reduced cerebral blood flow was associated with greater progression of brain atrophy. Data of 1165 patients (61 ± 10 years) from the SMART-MR study, a prospective cohort study of patients with arterial disease, were used of whom 689 participated after 4 years and 297 again after 12 years. Attrition was substantial. Total brain volume and total cerebral blood flow were obtained from magnetic resonance imaging scans and expressed as brain parenchymal fraction (BPF) and parenchymal cerebral blood flow (pCBF). Mean decrease in BPF per year was 0.22% total intracranial volume (95% CI: –0.23 to –0.21). Mean decrease in pCBF per year was 0.24 ml/min per 100 ml brain volume (95% CI: –0.29 to –0.20). Using linear mixed models, lower pCBF at baseline was associated with a greater decrease in BPF over time (p =0.01). Lower baseline BPF, however, was not associated with a greater decrease in pCBF (p =0.43). These findings indicate that reduced cerebral blood flow is associated with greater progression of brain atrophy and provide further support for a role of cerebral blood flow in the process of neurodegeneration.  相似文献   
63.
64.
Affordable early screening in subjects with high risk of lung cancer has great potential to improve survival from this deadly disease. We measured gene expression from lung tissue and peripheral whole blood (PWB) from adenocarcinoma cases and controls to identify dysregulated lung cancer genes that could be tested in blood to improve identification of at-risk patients in the future. Genome-wide mRNA expression analysis was conducted in 153 subjects (73 adenocarcinoma cases, 80 controls) from the Environment And Genetics in Lung cancer Etiology study using PWB and paired snap-frozen tumor and noninvolved lung tissue samples. Analyses were conducted using unpaired t tests, linear mixed effects, and ANOVA models. The area under the receiver operating characteristic curve (AUC) was computed to assess the predictive accuracy of the identified biomarkers. We identified 50 dysregulated genes in stage I adenocarcinoma versus control PWB samples (false discovery rate ≤0.1, fold change ≥1.5 or ≤0.66). Among them, eight (TGFBR3, RUNX3, TRGC2, TRGV9, TARP, ACP1, VCAN, and TSTA3) differentiated paired tumor versus noninvolved lung tissue samples in stage I cases, suggesting a similar pattern of lung cancer-related changes in PWB and lung tissue. These results were confirmed in two independent gene expression analyses in a blood-based case-control study (n = 212) and a tumor-nontumor paired tissue study (n = 54). The eight genes discriminated patients with lung cancer from healthy controls with high accuracy (AUC = 0.81, 95% CI = 0.74-0.87). Our finding suggests the use of gene expression from PWB for the identification of early detection markers of lung cancer in the future.  相似文献   
65.
Endovascular intervention to exclude popliteal artery aneurysms (PAA) achieves results comparable to surgical intervention with less associated morbidity and mortality. However, the biomechanical forces inherent to this region pose unique impediments that can limit successful endovascular exclusion. Herein, we present a case of recurrent thrombotic occlusion of a PAA endoprosthesis secondary to dynamic extrinsic compression from the excluded PAA in the absence of an endoleak. Multimodality imaging proved vital in elucidating this novel etiology and enabled an appropriate definitive intervention. © 2010 Wiley‐Liss, Inc.  相似文献   
66.
Exposure to trauma and stress has been linked with poor health, while forgiveness appears to be positively associated with health outcomes. The current study investigates whether traits such as forgiveness and ruminative tendencies predict levels of trauma and stress experienced by New York City residents on the 1‐year anniversary of the September 11th terrorist attack. Seventy‐one students and staff members (57 females, 14 males) of a graduate school in New York City were administered the Impact of Events Scale, the Perceived Stress Scale, and questionnaires designed for the purpose of this study to measure ruminative tendencies and forgiveness on September 11, 2002. Rumination predicted levels of trauma (p < 0.05) and perceived stress (p < 0.01). Lower levels of forgiveness predicted perceived stress (p < 0.05), but not trauma. Rumination mediated the relationship between forgiveness and perceived stress. These findings suggest that individuals with higher levels of rumination have an elevated risk of experiencing trauma and stress‐related symptoms following a traumatic event. Forgiveness is associated with lower levels of stress, but not trauma, perhaps because trauma is an extreme form of stress. Forgiveness appears to serve as a buffer against stress more so in individuals with low levels of rumination than in individuals with high levels of rumination. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
67.
灰毡毛忍冬化学成分研究V灰毡毛忍冬素F和G的结构测定   总被引:1,自引:0,他引:1  
灰毡毛忍冬化学成分研究V灰毡毛忍冬素F和G的结构测定陈敏,吴威巍,沈国强,罗思齐,李惠庭(上海医药工业研究院200040)灰毡毛忍冬(LoinceramacranthoidesHand.-Mazz)系忍冬科忍冬属植物,别名大花忍冬,分布于贵州、广西、...  相似文献   
68.
Background Processing multiple tissue sections in large Mohs cases is time consuming and labor intensive.
Objective To present innovative laboratory techniques to facilitate processing of large Mohs cases.
Methods A method for processing a large dermatofibrosarcoma protuberans Mohs case is outlined.
Results Modifications in tissue processing and equipment employed in a large Mohs case are presented.
Conclusion Innovative modifications to the standard Mohs laboratory technique can facilitate processing of large Mohs cases, resulting in high-quality, rapid frozen sections while optimizing efficiency.  相似文献   
69.
In high-field MRI severe problems with respect to B(1) (+) uniformity and specific absorption rate (SAR) deposition pose a great challenge to whole-body imaging. In this study the potential of a phased array transmit coil is investigated to simultaneously reduce B(1) (+) nonuniformity and SAR deposition. This was tested by performing electromagnetic simulations of a phased array TEM coil operating at 128 MHz loaded with two different homogeneous elliptical phantoms and four dielectric patient models. It was shown that the wave interference of a circularly polarized RF field with an ellipse and a pelvis produces largely identical B(1) (+) and electric field patterns. Especially for obese patients, this results in large B(1) (+) nonuniformity and global areas with elevated SAR deposition. It is demonstrated that a phased array transmit coil can reduce these phenomena. The technique was especially successful in suppressing SAR hotspots with a decrease up to 50%. The application of optimized settings for an ellipse to the patient models leads to comparable results as obtained with the patient-specific optimizations. This suggests that generic phase/amplitude port settings are possible, requiring no preinformation about patient-specific RF fields. Such a scheme would, due to its simultaneous B(1) (+) homogenization and extra SAR margin, have many benefits for whole-body imaging at 3 T.  相似文献   
70.
Anti-harm-reduction advocates sometimes resort to pseudo-analogies to ridicule harm reduction. Those opposed to the use of smokeless tobacco as an alternative to smoking sometimes suggest that the substitution would be like jumping from a 3 story building rather than 10 story, or like shooting yourself in the foot rather than the head. These metaphors are grossly inappropriate for several reasons, notably including the fact that they are misleading about the actual risk levels. Based on the available literature on mortality from falls, we estimate that smoking presents a mortality risk similar to a fall of about 4 stories, while mortality risk from smokeless tobacco is no worse than that from an almost certainly non-fatal fall from less than 2 stories. Other metaphors are similarly misleading. These metaphors, like other false and misleading anti-harm-reduction statements are inherently unethical attempts to prevent people from learning accurate health information. Moreover, they implicitly provide bad advice about health behavior priorities and are intended to persuade people to stick with a behavior that is more dangerous than an available alternative. Finally, the metaphors exhibit a flippant tone that seems inappropriate for a serious discussion of health science.  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