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   34232篇
  免费   3417篇
  国内免费   143篇
耳鼻咽喉   414篇
儿科学   1072篇
妇产科学   958篇
基础医学   4714篇
口腔科学   784篇
临床医学   3671篇
内科学   7133篇
皮肤病学   446篇
神经病学   2724篇
特种医学   1152篇
外国民族医学   9篇
外科学   4378篇
综合类   782篇
一般理论   28篇
预防医学   3926篇
眼科学   829篇
药学   2429篇
中国医学   38篇
肿瘤学   2305篇
  2021年   458篇
  2020年   255篇
  2019年   458篇
  2018年   521篇
  2017年   455篇
  2016年   428篇
  2015年   462篇
  2014年   721篇
  2013年   1115篇
  2012年   1562篇
  2011年   1623篇
  2010年   866篇
  2009年   771篇
  2008年   1422篇
  2007年   1617篇
  2006年   1521篇
  2005年   1424篇
  2004年   1289篇
  2003年   1260篇
  2002年   1283篇
  2001年   1133篇
  2000年   1187篇
  1999年   992篇
  1998年   394篇
  1997年   356篇
  1996年   385篇
  1995年   323篇
  1994年   329篇
  1993年   304篇
  1992年   925篇
  1991年   912篇
  1990年   832篇
  1989年   776篇
  1988年   687篇
  1987年   703篇
  1986年   701篇
  1985年   677篇
  1984年   551篇
  1983年   428篇
  1982年   333篇
  1981年   285篇
  1980年   256篇
  1979年   531篇
  1978年   322篇
  1977年   261篇
  1976年   283篇
  1975年   317篇
  1974年   354篇
  1973年   293篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 818 毫秒
991.
ContextPain can be a debilitating side effect of radiation therapy (RT). Data from the general population have shown that sleep disturbance can influence pain incidence and severity; however, less is known about this relationship in patients with breast cancer receiving RT.ObjectivesThis secondary analysis examined the association of pretreatment moderate/severe levels of sleep disturbance with subsequent RT-induced pain after adjusting for pre-RT pain.MethodsWe report on 573 female patients with breast cancer undergoing RT from a previously completed Phase II clinical trial for radiation dermatitis. Sleep disturbance, total pain, and pain subdomains—sensory pain, affective pain, and perceived pain intensity were assessed at pre-RT and post-RT. At pre-RT, patients were dichotomized into two groups: those with moderate/severe sleep disturbance (N = 85) vs. those with no/mild sleep disturbance (control; N = 488).ResultsAt pre-RT, women with moderate/severe sleep disturbance were younger, less likely to be married, more likely to have had mastectomy and chemotherapy, and more likely to have depression/anxiety disorder and fatigue than the control group (all Ps < 0.05). Generalized estimating equations model, after controlling for pre-RT pain and other covariates (e.g., trial treatment condition and covariates that were significantly correlated with post-RT pain), showed that women with moderate/severe sleep disturbance at pre-RT vs. control group had significantly higher mean post-RT total pain as well as sensory, affective, and perceived pain (effect size = 0.62, 0.60, 0.69, and 0.52, respectively; all Ps < 0.05).ConclusionThese findings suggest that moderate/severe disturbed sleep before RT is associated with increased pain from pre-to-post-RT in patients with breast cancer.  相似文献   
992.

In the 50 years since it was first introduced, cognitive therapy has been shown to be as efficacious as antidepressant medications (on average) in the acute treatment of nonpsychotic depression, although some patients will do better on one than on the other. Moreover, patients treated to remission with cognitive therapy are less than half as likely to relapse following treatment termination as patients treated to remission with medications. However, a recent study suggests that adding medications interferes with any such enduring effect and medications themselves may have an iatrogenic effect that suppresses symptoms at the expense of prolonging the underlying episode. Neural imaging suggests that cognitive therapy works from the “top down” to facilitate cortical regulation of affect processes whereas medications work from the “bottom up” to dampen the stress response. Adaptationist theory suggests that depression is an evolved adaptation that served to keep our ancestors ruminating about complex social problems until they arrived at a solution; if true then any intervention that facilitates problem solving is likely preferable to one that merely anesthetizes distress.

  相似文献   
993.
994.
MS2 phage (MS2 Ø) is a coli phage, non-pathogenic to eukaryotic cells, which has been used as a simulant for viral biothreats, such as those causing smallpox and hemorrhagic fever. MS2 Ø consists of an icosahedral capsid, 28 nm in diameter, and a single stranded RNA genome; the viral capsid is composed of 180 copies of coat protein (CP). In this study, we isolated anti-MS2 Ø single domain antibodies (sdAbs) for the sensitive detection of the MS2 Ø. To achieve this, a first immune sdAb library was prepared from llamas immunized with purified coat protein and a second from animals immunized with MS2 Ø. By panning the two libraries against CP, MS2 Ø, or alternating between the two targets, anti-MS2 Ø and anti-CP sdAbs were selected, sequenced, and characterized for their binding affinity. Both direct binding assays and capture sandwich assays were performed on the MAGPIX platform. One of the best anti-MS2 Ø sdAb, Lib2CP12H, could detect MS2 Ø concentrations as low as 1.45 ng/mL (~5.0E+6 pfu/mL), providing equivalent detection to conventional antibodies. This sdAb is thermally stable with a melting temperature around 60 °C and recovered 80% of its secondary structure after heat denaturation.  相似文献   
995.
Functional magnetic resonance imaging was used to compare brain activation associated with basic-level (e.g. bird) and subordinate-level (e.g. eagle) processing for both visual and semantic judgements. We localised the putative face area for 11 subjects, who also performed visual matching judgements for pictures and aurally presented words. The middle fusiform and occipital gyri were recruited for subordinate minus basic visual judgements, reflecting additional perceptual processing. When the face area was localised individually for each subject, analyses in the middle fusiform gyri revealed that subordinate-level processing activated the individuals face area. We propose that what is unique about the way faces engage this region is the focal spatial distribution of the activation rather than the recruitment of the face per se. Eight subjects also performed semantic judgements on aurally presented basic- and subordinate-level words. The parahippocampal gyri were more activated for subordinate-level than basic-level semantic judgements. Finally, the left posterior inferior temporal gyrus was activated for subordinate-level judgements, both visual and semantic, as well as during passive viewing of faces.  相似文献   
996.
Abstract

The authors investigated the relationship between brief warm social and physical contact among cohabitating couples and blood pressure (BP) reactivity to stress in a sample of healthy adults (66 African American, 117 Caucasian; 74 women, 109 men). Prior to stress, the warm contact group underwent a 10-minute period of handholding while viewing a romantic video, followed by a 20-second hug with their partner, while the no contact group rested quietly for 10 minutes and 20 seconds. In response to a public speaking task, individuals receiving prestress partner contact demonstrated lower systolic BP, diastolic BP, and heart rate increases compared with the no contact group. The effects of warm contact were comparable for men and women and were greater for African Americans compared with Caucasians. These findings suggest that affectionate relationships with a supportive partner may contribute to lower reactivity to stressful life events and may partially mediate the benefit of marital support on better cardiovascular health.  相似文献   
997.
PurposeBrachytherapy (BT) after surgical resection of keloids reduces the risk of local recurrence, but standardization of dose/technique is lacking. Typical keloid BT treatment utilizes a single-channel source prescribed to 5-mm depth. We investigated the dosimetry of a volume-based target definition for interstitial high-dose-rate BT treatment of keloids.Methods and MaterialsWe retrospectively identified consecutive 14 patients who had a total of 20 keloids treated with interstitial high-dose-rate BT for keloids at our institution between 2004 and 2014. Keloids were treated with a single 8 Gy fraction prescribed to 5 mm beneath the scar within 36 h of surgery. Retrospectively, a 3-mm skin high-risk clinical target volume (HR-CTV) was contoured under the scar for volume-based dose calculations.ResultsMean (SD) HR-CTV was 3.91 cm3 (3.1) and mean (SD) HR-CTV dose was 11.3 Gy (3.6). Mean D90 (SD) was 62.9% (25.8) and mean V100 (SD) was 56.5% (26.4). The mean V150 (SD), V200 (SD), and V300 (SD) were as follows: 37.6% (19.9), 25.1% (14.4), and 11.3% (6.5), respectively. No local failures were reported at 9 months median followup. There were no Grade 2 or higher late toxicities.ConclusionsUsing a volume-based target definition, a wide range of target coverage was observed. This is likely a consequence of the curvature of the skin and the challenges of keeping the catheter equidistant from the skin across the target. Additional data are needed to define the potential clinical impact on outcomes/toxicities of dosimetric correlates with single-catheter BT keloid treatment.  相似文献   
998.
Understanding how and where in the brain sentence-level meaning is constructed from words presents a major scientific challenge. Recent advances have begun to explain brain activation elicited by sentences using vector models of word meaning derived from patterns of word co-occurrence in text corpora. These studies have helped map out semantic representation across a distributed brain network spanning temporal, parietal, and frontal cortex. However, it remains unclear whether activation patterns within regions reflect unified representations of sentence-level meaning, as opposed to superpositions of context-independent component words. This is because models have typically represented sentences as “bags-of-words” that neglect sentence-level structure. To address this issue, we interrogated fMRI activation elicited as 240 sentences were read by 14 participants (9 female, 5 male), using sentences encoded by a recurrent deep artificial neural-network trained on a sentence inference task (InferSent). Recurrent connections and nonlinear filters enable InferSent to transform sequences of word vectors into unified “propositional” sentence representations suitable for evaluating intersentence entailment relations. Using voxelwise encoding modeling, we demonstrate that InferSent predicts elements of fMRI activation that cannot be predicted by bag-of-words models and sentence models using grammatical rules to assemble word vectors. This effect occurs throughout a distributed network, which suggests that propositional sentence-level meaning is represented within and across multiple cortical regions rather than at any single site. In follow-up analyses, we place results in the context of other deep network approaches (ELMo and BERT) and estimate the degree of unpredicted neural signal using an “experiential” semantic model and cross-participant encoding.SIGNIFICANCE STATEMENT A modern-day scientific challenge is to understand how the human brain transforms word sequences into representations of sentence meaning. A recent approach, emerging from advances in functional neuroimaging, big data, and machine learning, is to computationally model meaning, and use models to predict brain activity. Such models have helped map a cortical semantic information-processing network. However, how unified sentence-level information, as opposed to word-level units, is represented throughout this network remains unclear. This is because models have typically represented sentences as unordered “bags-of-words.” Using a deep artificial neural network that recurrently and nonlinearly combines word representations into unified propositional sentence representations, we provide evidence that sentence-level information is encoded throughout a cortical network, rather than in a single region.  相似文献   
999.
Journal of Neurology - Sleep disorders can occur in early Parkinson’s disease (PD). However, the relationship between different sleep disturbances and their longitudinal evolution has not...  相似文献   
1000.
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