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   629篇
  免费   45篇
  国内免费   6篇
耳鼻咽喉   2篇
儿科学   7篇
妇产科学   8篇
基础医学   130篇
口腔科学   5篇
临床医学   67篇
内科学   97篇
皮肤病学   13篇
神经病学   82篇
特种医学   68篇
外科学   35篇
综合类   5篇
预防医学   43篇
眼科学   3篇
药学   73篇
中国医学   4篇
肿瘤学   38篇
  2023年   3篇
  2022年   4篇
  2021年   24篇
  2020年   23篇
  2019年   23篇
  2018年   39篇
  2017年   33篇
  2016年   21篇
  2015年   19篇
  2014年   28篇
  2013年   31篇
  2012年   61篇
  2011年   73篇
  2010年   23篇
  2009年   21篇
  2008年   33篇
  2007年   56篇
  2006年   48篇
  2005年   24篇
  2004年   26篇
  2003年   16篇
  2002年   12篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1990年   1篇
  1987年   1篇
  1986年   2篇
  1983年   2篇
  1982年   1篇
  1981年   3篇
  1980年   1篇
  1979年   4篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
  1933年   1篇
排序方式: 共有680条查询结果,搜索用时 15 毫秒
1.
Considering the relatively high heritability of schizophrenia and the fact that it significantly reduces the reproductive fitness of affected individuals, it is not clear how the disorder is still maintained in human populations at a disproportionally high prevalence. Many theories propose that the disorder is a result of a trade‐off between costs and benefits of the evolution of exclusively human adaptations. There have also been suggestions that schizophrenia risk alleles are accompanied with increase in fitness of affected persons or their relatives in both past and current social contexts. The discoveries of novel schizophrenia‐related genes and the advancements in comparative genomics (especially comparisons of the human genome and the genomes of related species, such as chimpanzees and extinct hominids) have finally made certain evolutionary theories testable. In this paper, we review the current understanding of the genetics of schizophrenia, the basic principles of evolution that complement our understanding of the subject, and the latest genetic studies that examine long‐standing evolutionary theories of schizophrenia using novel methodologies and data. We find that the origin of schizophrenia is complex and likely governed by different evolutionary mechanisms that are not mutually exclusive. Furthermore, the most recent evidence implies that schizophrenia cannot be comprehended as a trait that has elevated fitness in human evolutionary lineage, but has been a mildly deleterious by‐product of specific patterns of the evolution of the human brain. In other words, novel findings do not support previous hypotheses stating that schizophrenia risk genes have an evolutionary advantage.  相似文献   
2.
3.
Interaction between autoreactive immune cells and astroglia is an important part of the pathologic processes that fuel neurodegeneration in multiple sclerosis. In this inflammatory disease, immune cells enter into the central nervous system (CNS) and they spread through CNS parenchyma, but the impact of these autoreactive immune cells on the activity pattern of astrocytes has not been defined. By exploiting naïve astrocytes in culture and CNS-infiltrated immune cells (CNS IICs) isolated from rat with experimental autoimmune encephalomyelitis (EAE), here we demonstrate previously unrecognized properties of immune cell–astrocyte interaction. We show that CNS IICs but not the peripheral immune cell application, evokes a rapid and vigorous intracellular Ca2+ increase in astrocytes by promoting glial release of ATP. ATP propagated Ca2+ elevation through glial purinergic P2X7 receptor activation by the hemichannel-dependent nucleotide release mechanism. Astrocyte Ca2+ increase is specifically triggered by the autoreactive CD4+ T-cell application and these two cell types exhibit close spatial interaction in EAE. Therefore, Ca2+ signals may mediate a rapid astroglial response to the autoreactive immune cells in their local environment. This property of immune cell–astrocyte interaction may be important to consider in studies interrogating CNS autoimmune disease.  相似文献   
4.
In this paper, we present the methodology for determining the point model of the ilium bone in cases when volumetric data of the whole bone are not available. An extreme traumatic bone damage, osteoporosis, destruction of bone tissue by malignant bone tumors or the existence of only 2D medical image (X-ray) can be the reason for the lack of complete volumetric data. Points on the bone surface were defined at the curves that run through 26 previously defined parameters, at the edges of anteroposterior (A–P) and lateral projections and at the parts of the surface between some parameters. Those parts of the surface, enclosed by parameters, represent ten parametric regions. The values of coordinates, which represent the input data in the statistical program, were measured in a uniquely defined coordinate system. After establishing the correlations between the values of coordinates, 8869 different linear and nonlinear regression models were obtained. The prediction values for point coordinates were calculated and exported to a CAD program. Results obtained were tested on a randomly chosen male right ilium bone, applying the methodology for creating the prediction model using the method of parametric regions, which allows creating a complete polygonal model, for each region separately or just for some parts of the region. Results obtained in the form of regression equations for the right ilium bone can be applied to the left ilium bone. The results of the research were verified using a comparative deviation and distance analysis between the initial and obtained polygonal models.  相似文献   
5.
ABSTRACT

Objective: The aim of this study was to correlate degree of depression, somatization, and chronic pain in asymptomatic women with clinical findings, using Research Diagnostic Criteria/Temporomandibular disorders (RDC/TMD).

Methods: A total of 200 female participants, ages 18–65, filled out a standard RDC/TMD axis II form for the assessment of chronic pain, disability, depression, and non-specific physical symptoms and underwent clinical examination of the temporomandibular joint. Correlation of clinical findings (axis I) and axis II assessment was performed using Spearman’s correlation test, with significance set at p < 0.05.

Results: There was a significant correlation between depression scores (p < 0.04), chronic pain (p < 0.001), and non-specific physical symptoms without questions about pain (p = 0.008).

Discussion: The highest scores on the Graded Chronic Pain Scale were observed in patients with arthralgia, while patients with myofascial pain scored higher on depression and somatization tests.  相似文献   
6.
7.

Introduction

Coronary artery thrombosis in ST-elevation myocardial infarction (STEMI) is a dynamic process often preceded by episodes of silent plaque rupture and subocclusive thrombosis. Thrombus organization is achieved by ingrowth of endothelial and smooth muscle cells. Clinical significance and impact of thrombus neovascularization on primary percutaneous coronary intervention (pPCI) outcome remain unclear. Therefore we investigated composition and neovascularization of thrombi aspirated during pPCI and their association with clinical and angiographic parameters of STEMI patients.

Methods

Aspirated thrombi retrieved from 84 STEMI patients were classified as fresh (< 1 day), lytic (1-5 days) or organized (> 5 days). Thrombus neovascularization was evaluated immunohistochemically using CD34, CD31 and VEGF antibodies. CD34 and CD31 immunopositive (CD34/CD31 +) cells were organized as single, clusters and microvessels. VEGF positivity was graded as low or high, based on thrombus surface immunopositive area.

Results

CD34/CD31 + cells were present in 67% of all aspirated thrombi. Thrombus CD34/CD31 positivity was associated with previous history of angina pectoris (χ2 = 6.142, p = 0.013) and lower myocardial blush grade (MBG < 3, χ2 = 12.602, p < 0.001). Organization of CD34/CD31 + cells showed inverse association with the extent of VEGF positivity (χ2 = 10.607, p = 0.005). Fresh thrombi were associated with shorter ischemic time (U = 237.5, p = 0.002) and MBG 3 (χ2 = 6.379, p = 0.012).

Conclusions

Older thrombus age and neovascularization are associated with suboptimal myocardial perfusion in STEMI patients. Thrombus VEGF expression is inversely associated with degree of CD34 + cell organization. Therefore, neovascularization of aspirated thrombi may indicate the duration of thrombosis, coronary microcirculation status and outcome in STEMI patients.  相似文献   
8.
The aim of this study was to define features of Guillain‐Barré syndrome in a large cohort of patients from three Western Balkans countries. Data from adult Guillain‐Barré syndrome (GBS) cases from 2009 to 2013 were retrospectively obtained from all tertiary health care centers. During the 5‐year period, 327 new cases of GBS were identified with a male to female ratio of 1.7 : 1. The most common GBS variants were demyelinating (65%) and axonal (12%). At nadir 45% of patients were chair‐bound, confined to bed, or required assisted ventilation, while 5% died. The crude incidence of GBS in Serbia and Montenegro was 0.93 per 100,000 population, and age‐adjusted incidence according to the world standard population was 0.86 per 100,000. Incidence was particularly high in 50‐ to 80‐year‐old men. Statistically significant seasonal variations of GBS were not observed. This study of patients with GBS in the Western Balkans allows us to prepare the health system better and to improve the management of patients. This study also opens opportunities for international collaboration and for taking part in the multinational studies on GBS.  相似文献   
9.
Women with antiphospholipid syndrome (APS) experience pregnancy complications mostly due to impaired trophoblast cell functions. Antiphospholipid antibodies (aPL) affect extravillous trophoblast in vivo and in culture, but the mechanisms are still poorly understood. Previously, syncytiotrophoblast was shown to bind and internalize aPL, which was not replicated for extravillous cytotrophoblast in short term culture. Here, aPL binding and time dependent internalization was demonstrated with exposure to aPL in the extravillous cell line HTR-8/SVneo and isolated first trimester of pregnancy cytotrophoblast (CT) using immunocytochemistry and flow cytometry. Intracellular aPL were detectable from 2?h of culture, reaching 30.7?±?3.1% (p?<?0.001) positive cells in CT and 24.8?±?7% (p?<?0.01) in HTR-8/SVneo cells at 24?h and 33?±?4.2% (p?<?0.01) at 48?h. The data presented show that extravillous trophoblast cells internalize aPL in a time-dependent manner significantly more than control immunoglobulins after 24?h of exposure.  相似文献   
10.
As a major phytoestrogen of soy, genistein effectively prevents bone loss in both humans and rat models of osteoporosis. However, although the bone‐sparing effects of genistein are achieved directly through estrogen receptors, its mode of action on bone by modulation of other endocrine functions is not entirely clear. Thus, thyroid hormones and calcitonin (CT ) have an essential influence on bone metabolism. Besides its action on bones, in this study we examined the effect of genistein on the activity of two different endocrine cell populations, thyroid follicular and C‐cells. Fifteen‐month‐old Wistar rats were either bilaterally orchidectomized (Orx) or sham‐operated (SO ). Two weeks after surgery, half of the Orx rats were treated chronically with 30 mg kg?1 b.w. genistein (Orx + G) subcutaneously (s.c.) every day for 3 weeks, while the remaining Orx rats and the SO rats were given the same volume of sterile olive oil to serve as controls. For histomorphometrical analysis of the trabecular bone microarchitecture an ImageJ public domain image processing programme was used. Thyroid sections were analysed histologically and stereologically after visualization of follicular and C‐cells by immunohistochemical staining for thyroglobulin and CT . Thyroid follicular epithelium, interstitium, colloid and CT ‐immunopositive C‐cells were examined morphometrically. Serum concentrations of osteocalcin (OC ), triiodothyronine (T3), thyroxine (T4) and CT were determined as well as urinary calcium (Ca2+) concentrations. Genistein treatment significantly increased cancellous bone area (B.Ar), trabecular thickness (TbTh) and trabecular number (TbN) (P  < 0.05), but trabecular separation (Tb.Sp) was decreased (P  < 0.05) compared with control Orx rats. In the thyroid, genistein treatment significantly elevated the relative volume density (Vv) of the follicular cells (P  < 0.05) compared with Orx, whereas Vv of the colloid was lower (P  < 0.05) than in the Orx. Evaluation of the biochemical parameters showed significant reductions in serum OC , T3, T4 and urinary Ca2+ concentrations (P  < 0.05), compared with Orx rats. These data indicate that genistein treatment improves the trabecular microarchitecture of proximal tibia, induces histomorphometrical changes in thyroid glands, and decreases circulating thyroid hormone levels in orchidectomized rat model of male osteoporosis.  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