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   6812篇
  免费   427篇
  国内免费   12篇
耳鼻咽喉   41篇
儿科学   277篇
妇产科学   251篇
基础医学   777篇
口腔科学   62篇
临床医学   1314篇
内科学   1180篇
皮肤病学   108篇
神经病学   504篇
特种医学   129篇
外科学   583篇
综合类   70篇
一般理论   9篇
预防医学   1032篇
眼科学   149篇
药学   313篇
  1篇
中国医学   5篇
肿瘤学   446篇
  2023年   34篇
  2022年   57篇
  2021年   135篇
  2020年   75篇
  2019年   148篇
  2018年   151篇
  2017年   143篇
  2016年   145篇
  2015年   141篇
  2014年   212篇
  2013年   344篇
  2012年   479篇
  2011年   542篇
  2010年   281篇
  2009年   239篇
  2008年   500篇
  2007年   498篇
  2006年   490篇
  2005年   452篇
  2004年   434篇
  2003年   423篇
  2002年   411篇
  2001年   48篇
  2000年   46篇
  1999年   54篇
  1998年   66篇
  1997年   76篇
  1996年   70篇
  1995年   51篇
  1994年   41篇
  1993年   49篇
  1992年   31篇
  1991年   14篇
  1990年   27篇
  1989年   29篇
  1988年   27篇
  1987年   17篇
  1986年   10篇
  1985年   17篇
  1984年   22篇
  1983年   19篇
  1982年   29篇
  1981年   16篇
  1980年   23篇
  1979年   13篇
  1978年   21篇
  1977年   15篇
  1976年   10篇
  1975年   15篇
  1966年   6篇
排序方式: 共有7251条查询结果,搜索用时 31 毫秒
51.
Equine protozoal myeloencephalitis is a progressive neurologic disease of horses most commonly caused by infection with the apicomplexan parasite Sarcocystis neurona. Factors affecting neuroinvasion and neurovirulence have not been determined. We investigated the pathogenesis of infection with S. neurona in horses with severe combined immune deficiency (SCID). Two immunocompetent (IC) Arabian horses and two Arabian horses with SCID were infected orally with 5 x 10(5) sporocysts of S. neurona. Four IC horses and one SCID horse were infected intravenously (i.v.) with 5 x 10(8) merozoites of the WSU-1 isolate of S. neurona. Despite prolonged parasitemia and persistent infection of visceral tissues (skeletal muscle, cardiac muscle, lung, liver, and spleen) as demonstrated by PCR and culture, SCID horses did not develop neurologic signs after oral or i.v. infection. S. neurona was undetectable in the neuronal tissues of SCID horses by either PCR, immunohistochemistry, or culture. In contrast, although parasitemia was undetectable in orally infected IC horses and of only short duration in i.v. infected IC horses, four of six IC horses developed neurologic signs. S. neurona was detectable by PCR and/or culture of neural tissue but not visceral tissue of IC horses with neurologic disease. Infected SCID horses are unable to clear S. neurona from visceral tissues, but the infection does not result in neurologic signs; in contrast, IC horses rapidly control parasitemia and infection of visceral tissues but frequently experience neuroinvasion and exhibit clinical signs of neurologic disease.  相似文献   
52.
53.
Summary We used the flourescent dye DAPI to visualize nucleoids of chloroplast DNA and follow their behavior through sexual reproduction by counting nucleoids in fixed cells at various stages. Nucleoid number varied greatly among cells at each stage. The mean number of nucleoids per cell was similar in mt + and mt vegetative cells, and declined similarly during gametogenesis. Longer periods of nitrogen starvation reduced the mean nucleoid number further. Mean nucleoid number declined again in mating pairs, and continued to drop in zygotes up to the latest stage that can be examined (24-h zygotes). The oldest zygotes had means of about 2 to 3 nucleoids in different experiments, significantly fewer than in the mt + gametes (usually 4 to 5). The quantitative data on nucleoid number, mating efficiency, and germination efficiency allowed us to show that the decrease in nucleoid number is not limited to gametes that do not mate, or to zygotes that do not germinate. These data are consistant with earlier biochemical studies showing loss of chloroplast DNA during gametogenesis in both mating types, and with the degradation of paternal chloroplast DNA detected biochemically and (in non-quantitative studies) by DAPI staining. There may also be some fusion of nucleoids, although if it occurs it is not complete by 24 h of zygote maturation.  相似文献   
54.
Inhibition of return (IOR) refers to an increase in time to react to a target in a previously attended location. Children with spina bifida meningomyelocele (SBM) and hydrocephalus have congenital dysmorphology of the midbrain, a brain region associated with the control of covert orienting in general and with IOR in particular. The authors studied exogenously cued covert orienting in 8- to 19-year-old children and adolescents (84 with SBM and 37 age-matched, typically developing controls). The exogenous cue was a luminance change in a peripheral box that was 50% valid for the upcoming target location. Compared with controls, children with SBM showed attenuated IOR in the vertical plane, a deficit that was associated with midbrain dysmorphology in the form of tectal beaking but not with posterior brain volume loss. The data add to the emerging evidence for SBM deficits in attentional orienting to salient information.  相似文献   
55.

Background  

Although back pain is the most common reason patients use complementary and alternative medical (CAM) therapies, little is known about the willingness of primary care back pain patients to try these therapies. As part of an effort to refine recruitment strategies for clinical trials, we sought to determine if back pain patients are willing to try acupuncture, chiropractic, massage, meditation, and t'ai chi and to learn about their knowledge of, experience with, and perceptions about each of these therapies.  相似文献   
56.
Genetic alterations leading to overactivation of mammalian target of rapamycin (mTOR) signaling result in brain overgrowth syndromes such as focal cortical dysplasia (FCD) and megalencephaly. Megalencephaly with cutis tri‐color of the Blaschko‐linear type pigmentary mosaicism and intellectual disability is a rare neurodevelopmental disorder attributed to the recurrent mosaic c.5930C > T (p.Thr1977Ile) MTOR variant. This variant was previously reported at low to intermediate levels of mosaicism in the peripheral blood of three unrelated individuals with consistent clinical findings. We report a fourth case of a 3‐year‐old female presenting with megalencephaly, obstructive hydrocephalus due to cerebral aqueductal stenosis, asymmetric polymicrogyria, dysgenesis of the corpus callosum, hypotonia, developmental delay, and cutaneous pigmentary mosaicism. Oligonucleotide and SNP chromosomal microarray (CMA), karyotype, and trio whole exome sequencing (WES) in the peripheral blood, as well as a targeted gene variant panel from fibroblasts derived from hyperpigmented and non‐hyperpigmented skin did not detect any abnormalities in MTOR or other genes associated with brain overgrowth syndromes. Unlike the previously reported cases, the de novo c.5930C > T (p.Thr1977Ile) MTOR variant was detected at 32% mosaicism in our patient only after WES was performed on fibroblast‐derived DNA from the hyperpigmented skin. This case demonstrates the tissue variability in mosaic expression of the recurrent p.Thr1977Ile MTOR variant, emphasizes the need for skin biopsies in the genetic evaluation of patients with skin pigmentary mosaicism, and expands the clinical phenotype associated with this pathogenic MTOR variant.  相似文献   
57.
Maternal and Child Health Journal - Perinatal mood and anxiety disorders can have far reaching negative impact on both maternal mental health and child growth and development. Multimodal group...  相似文献   
58.
Burton  Wendy  Sahota  Pinki  Twiddy  Maureen  Brown  Julia  Bryant  Maria 《Prevention science》2021,22(3):345-356
Prevention Science - Poor participant engagement threatens the potential impact and cost-effectiveness of public health programmes preventing meaningful evaluation and wider application. Although...  相似文献   
59.
High-risk combinations of recipient and graft characteristics are poorly defined for liver retransplantation (reLT) in the current era. We aimed to develop a risk model for survival after reLT using data from the European Liver Transplantation Registry, followed by internal and external validation. From 2006 to 2016, 85 067 liver transplants were recorded, including 5581 reLTs (6.6%). The final model included seven predictors of graft survival: recipient age, model for end-stage liver disease score, indication for reLT, recipient hospitalization, time between primary liver transplantation and reLT, donor age, and cold ischemia time. By assigning points to each variable in proportion to their hazard ratio, a simplified risk score was created ranging 0–10. Low-risk (0–3), medium-risk (4–5), and high-risk (6–10) groups were identified with significantly different 5-year survival rates ranging 56.9% (95% CI 52.8–60.7%), 46.3% (95% CI 41.1–51.4%), and 32.1% (95% CI 23.5–41.0%), respectively (< 0.001). External validation showed that the expected survival rates were closely aligned with the observed mortality probabilities. The Retransplantation Risk Score identifies high-risk combinations of recipient- and graft-related factors prognostic for long-term graft survival after reLT. This tool may serve as a guidance for clinical decision-making on liver acceptance for reLT.  相似文献   
60.
PurposeAssessing surgical accuracy and patient-recorded outcome measures for patients fitted with either the OPTY-LINE intramedullary realignment system or the Tomofix plate for medial opening wedge high tibial osteotomy (HTO).Patients and methodsTwo matched case series of patients with symptomatic medial compartment osteoarthritis without other significant knee pathology. One group comprised of 19 patients receiving the Tomofix plate, whereas another comprised of 12 patients receiving the OPTY-LINE intramedullary nail. Patella-centred long leg alignment radiographs were assessed to calculate surgical accuracy in all cases. Patients completed knee injury osteoarthritis outcome scores (KOOS) and osteotomy surgery patient satisfaction questionnaires pre-operatively and at 24 months post-surgery.ResultsAbsolute surgical accuracy at 2 years post-surgery was a mean 4.2 [standard deviation 3.7] for OPTY-LINE versus 9.2 [SD 7.8] for Tomofix (p = 0.11, Mann–Whitney U test). On average, patients in either the OPTY-LINE or Tomofix cohort reported at least a minimal perceptible clinical improvement—minimum average improvement of 15—for all five KOOS themes. No significant difference in change of KOOS scores over time or patient satisfaction levels were observed between the two cohorts.ConclusionThe OPTY-LINE device for HTO performs to a similar level as the Tomofix device. Surgical accuracy data are promising for OPTY-LINE, but does not seem to readily translate into difference in patient-reported outcomes compared to Tomofix. Even longer follow-up periods, to measure survival rates, and true randomised trials on larger samples can elucidate if there is a benefit for using one device over the other.  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