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   5196篇
  免费   327篇
  国内免费   37篇
耳鼻咽喉   82篇
儿科学   132篇
妇产科学   154篇
基础医学   695篇
口腔科学   212篇
临床医学   491篇
内科学   992篇
皮肤病学   185篇
神经病学   214篇
特种医学   153篇
外科学   900篇
综合类   83篇
一般理论   3篇
预防医学   381篇
眼科学   85篇
药学   514篇
中国医学   35篇
肿瘤学   249篇
  2024年   7篇
  2023年   53篇
  2022年   150篇
  2021年   206篇
  2020年   144篇
  2019年   199篇
  2018年   248篇
  2017年   184篇
  2016年   198篇
  2015年   206篇
  2014年   285篇
  2013年   332篇
  2012年   474篇
  2011年   477篇
  2010年   267篇
  2009年   210篇
  2008年   284篇
  2007年   256篇
  2006年   229篇
  2005年   205篇
  2004年   165篇
  2003年   149篇
  2002年   126篇
  2001年   38篇
  2000年   45篇
  1999年   38篇
  1998年   23篇
  1997年   23篇
  1996年   26篇
  1995年   22篇
  1994年   16篇
  1993年   18篇
  1992年   18篇
  1991年   24篇
  1990年   24篇
  1989年   18篇
  1988年   15篇
  1987年   26篇
  1986年   24篇
  1985年   13篇
  1984年   8篇
  1983年   10篇
  1982年   9篇
  1981年   8篇
  1980年   12篇
  1979年   5篇
  1978年   5篇
  1971年   8篇
  1970年   4篇
  1966年   4篇
排序方式: 共有5560条查询结果,搜索用时 15 毫秒
51.
The development of children over time is one of the continuing aims of psychological inquiry. Many studies have concluded that children who grew up in dysfunctional households show inconsistent development across various developmental pathways. Previous studies have consistently concluded how different family factors, such as interparents relationship, parent–child relationships, and emotional relations in families, can explain the outcomes of child behavior problems. Therefore, this paper attempts to review the empirical findings of previous studies that assess the effects of marital relations on child behavioral development by reviewing the literature that supports the association between marital relations and behavioral problems of children. Twenty-seven studies were chosen for their outcomes. This review used online databases such as Google Scholar, Scopus, ProQuest, Psychological and Behavioral Science collection, SAGE full-text collection in psychology, and PsycINFO. The key words used were marital relation, marital conflict, marital satisfaction, child behavior problem, and offspring behavior adjustment. All articles hypothesized that marital relation affects child adjustment and behavior outcomes directly and indirectly. Approximately all the research samples were in the developmental stage (ages 3 to 12). Various methodologies were used in the studies, but some methodological defects in the literature in some way diminished the interpretation of their findings. Results revealed that children who come from families high in conflict are at risk of psychopathological developmental problems in their adolescent years. This review adds to a large collection of literature that highlights the damaging effects of marital conflict on children. Research limitations and suggestions for future studies are outlined. The study provides a concrete basis for further research on this topic considering that married couples and child behavior problems are varied. This review can benefit married and soon-to-be married couples by revealing perceptions into the experiences of others as regards marriage problem solving.  相似文献   
52.

Background:

Infection with Trichostrongylus spp. is common among human and herbivorous in most parts of Iran, especially in southern and northern areas. The aim of present study was to identify Trichostrongylus spp. among human population using excreted egg specimens, by the molecular method, in Mazandaran Province, northern Iran.

Methods:

Overall, 33 positive fecal specimens were randomly sampled and examined. PCR amplification of ITS2-rDNA region was performed on the isolated egg and then a restriction fragment length polymorphism (RFLP) profile was considered to discriminate of Trichostrongylus spp.

Results:

A total of 33 positive fecal specimens, 29(78.9%), 4(12.1%) were found T. colubriformis and T. axei respectively. Our data appear the molecular evidence of both human T. colubriformis and T. axei infections in North of Iran.

Conclusion:

T. colubriformis was the probable most common zoonotic species causing human trichostrongylosis infection in the area  相似文献   
53.

Background:

The trematodes of the genus Fasciola (the liver flukes) are among the well-known instances of food-borne parasites worldwide. Differentiation of Fasciola species is important because of their different transmission and epidemiological characteristics. The current study was undertaken to discriminate Fasciola species in the domestic ruminants of Urmia city, Iran.

Methods:

Adult flukes were isolated from the naturally infected livers of the slaughtered water buffaloes and sheep. The flukes were initially identified based on morphological and morphometric parameters. A 618-bp-long fragment of the 28SrRNA gene of Fasciola was amplified by polymerase chain reaction (PCR). The amplified fragment was digested by DraII or AvaII enzymes for a restriction fragment length polymorphism (RFLP) analysis and sequenced for the phylogenetic tree construction.

Results:

Based on the morphometric examination, the flukes belonged to F. hepatica, F. gigantica and an intermediate Fasciola form. The PCR-RFLP analysis was able to differentiate F. hepatica from F. gigantica. While the phylogenetic reconstruction justified, to some extent, the morphological diagnosis, it failed to segregate F. hepatica from F. gigantica identified in this and the previous studies.

Conclusion:

To resolve fully the problem of taxonomy and evolution in Fasciola species, employing a broad range of molecular and morphological approaches is necessary. This is crucial for epidemiological surveys and successful clinical management of their infection.  相似文献   
54.

Objectives

Widespread use of β-lactam antibiotics could cause resistance to this group of antibiotics in pathogenic bacteria through the production of the enzyme β-lactamases. The aim of this study is to determine the molecular detection of AmpC β-lactamases among clinical Escherichia coli isolated from Ilam hospitals in Ilam, Iran.

Methods

One hundred and twelve clinical isolates of E. coli were collected from hospitalized patients and were identified by biochemical tests. They were evaluated for extended spectrum beta-lactamases (ESBLs) production, and the positive strains were subjected to AmpC enzymes; for detection of AmpC cluster genes, multiplex polymerase chain reaction was applied.

Results

The analysis showed 62.5% of isolates were ESBLs positive and that five strains revealed the AmpC cluster genes. This is the first report of FOXM cluster genes in E. coli in Iran.

Conclusion

Based on our results, the prevalence of AmpC β-lactamases is increasing in Iran, which caused failure in antibiotic therapy. So, the current study recommended the revision of antibiotic policy in Iranian hospitals.  相似文献   
55.
Recently, nanosized metal-oxides have been extensively investigated for their ability to remove metal ions from aqueous media. However, the activity and capacity of these nanosized metal-oxides for removing metal ions decrease owing to their agglomeration in aqueous media. Herein, we synthesized a highly stable and magnetically separable rosin-biochar-coated (RBC) TiO2@C nanocomposite through a facile and environment-friendly wet chemical coating process, followed by a one-step heating route (pyrolysis) for efficient removal of Cr(vi) from aqueous solution. An array of techniques, namely, TEM, HRTEM, TEM-EDS, XRD, FTIR, VSM, BET and TGA, were used to characterize the prepared nanocomposite. The pyrolysis of rosin into biochar and the fabrication of Fe onto the RBC-TiO2@C nanocomposite were confirmed by FTIR and XRD examination, respectively. Moreover, TEM and HRTEM images and elemental mapping using TEM-EDS showed good dispersion of iron and carbon on the surface of the RBC-TiO2@C nanocomposite. Sorption of Cr(vi) ions on the surface of the RBC-TiO2@C nanocomposite was very fast and efficient, having a removal efficiency of ∼95% within the 1st minute of reaction. Furthermore, thermodynamic analysis showed negative values of Gibb''s free energy at all five temperatures, indicating that the adsorption of Cr(vi) ions on the RBC-TiO2@C nanocomposite was favorable and spontaneous. Conclusively, our results indicate that the RBC-TiO2@C nanocomposite can be used for efficient removal of Cr(vi) from aqueous media due to its novel synthesis and extraordinary adsorption efficacy during a short time period.

A biochar-coated RBC-TiO2@C nanocomposite was synthesized using a wet chemical coating followed by a one-step heating route (pyrolysis) for the efficient removal of Cr(vi).  相似文献   
56.
Background

Long-acting reversible contraceptives, such as the intrauterine device (IUD), remain underutilised in Pakistan with high discontinuation rates. Based on a 24-month prospective client follow-up (nested within a larger quasi-experimental study), this paper presents the comparison of two intervention models, one using private mid-level providers branded as “Suraj” and the other using community midwives (CMWs) of Maternal Newborn and Child Health Programme, for method continuation among IUD users. Moreover, determinants of IUD continuation and the reasons for discontinuation, and switching behaviour were studied within each arm.

Methods

A total of 1,163 IUD users, 824 from Suraj and 339 from the CMW model, were enrolled in this 24-month prospective client follow-up. Participants were followed-up by female community mobilisers physically every second month to ascertain continued IUD usage and to collect information on associated factors, switching behaviour, reasons for discontinuation, and pregnancy occurrence. The probabilities of IUD continuation and the risk factors for discontinuation were estimated by life table analysis and Cox proportional-hazard techniques, respectively.

Results

The cumulative probabilities of IUD continuation at 24 months in Suraj and CMW models were 82% and 80%, respectively. The difference between the two intervention areas was not significant. The probability distributions of IUD continuation were also similar in both interventions (Log rank test: χ2 = 0.06, df = 1, P = 0.81; Breslow test: χ2 = 0.6, df = 1, P = 0.44). Health concerns (Suraj = 57.1%, CMW = 38.7%) and pregnancy desire (Suraj = 29.3%, CMW = 40.3%) were reported as the most prominent reasons for IUD discontinuation in both intervention arms. IUD discontinuation was significantly associated with place of residence in Suraj and with age (15–25 years) in the CMW model.

Conclusion

CMWs and private providers are equally capable of providing quality IUD services and ensuring higher method continuation. Pakistan’s National Maternal Newborn and Child Health programme should consider training CMWs and providing IUDs through them. Moreover, private sector mid-level providers could be engaged in promoting the use of IUDs.

  相似文献   
57.
Clinical Rheumatology - Considering the pathologic significance of inflammation and oxidative stress in rheumatoid arthritis (RA) as well as the antioxidant, anti-inflammatory and hypolipidemic...  相似文献   
58.
Metabolic Brain Disease - Chronic methamphetamine (meth) abuse can lead to certain deficits in the hippocampal function by affecting the hippocampal neurogenesis and plasticity. To determine...  相似文献   
59.
Biogerontology - Increasing age has a major detrimental impact on female fertility, which, with an ageing population, has major sociological implications. This impact is primarily mediated through...  相似文献   
60.
Abstract

The aim of this study was to estimate the effect of ambient air pollutants on cardiovascular deaths in Tehran, Iran. In this time series study, air pollutant data were acquired from the Environmental Protection Agency. Meteorological data were acquired from the meteorological organization, and death data were acquired from the Tehran’s cemetery registration. Generalized Additive Models (GAM) were used for estimating the Rate Ratio. NO2, SO2 and PM10 were associated with total cardiovascular deaths. PM10 and NO2 showed stronger relations with deaths in the elder age group. The result of this study showed that NO2, SO2, PM10 and O3 are probably responsible for part of the cardiovascular deaths that happen daily in Tehran.  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