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   3281篇
  免费   166篇
  国内免费   15篇
耳鼻咽喉   80篇
儿科学   227篇
妇产科学   155篇
基础医学   333篇
口腔科学   103篇
临床医学   322篇
内科学   647篇
皮肤病学   126篇
神经病学   170篇
特种医学   112篇
外科学   382篇
综合类   72篇
预防医学   254篇
眼科学   73篇
药学   248篇
中国医学   18篇
肿瘤学   140篇
  2024年   1篇
  2023年   52篇
  2022年   97篇
  2021年   145篇
  2020年   95篇
  2019年   146篇
  2018年   137篇
  2017年   104篇
  2016年   160篇
  2015年   128篇
  2014年   164篇
  2013年   221篇
  2012年   292篇
  2011年   276篇
  2010年   143篇
  2009年   135篇
  2008年   178篇
  2007年   213篇
  2006年   186篇
  2005年   175篇
  2004年   152篇
  2003年   81篇
  2002年   81篇
  2001年   11篇
  2000年   9篇
  1999年   12篇
  1998年   9篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1994年   6篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   2篇
  1988年   3篇
  1987年   4篇
  1986年   1篇
  1985年   1篇
  1984年   3篇
  1983年   2篇
  1980年   1篇
  1974年   1篇
  1973年   1篇
  1971年   2篇
  1960年   1篇
  1958年   1篇
排序方式: 共有3462条查询结果,搜索用时 16 毫秒
41.

Introduction

Facial candidal abscess is an infection with a fungal cause which was presented in this case such a rarity. We report a rare case of facial abscess due to Candida species in a patient with unknown diabetes.

Materials and Methods

The patient presented with a longstanding firm swelling which occurred 2 weeks ago and did not show any improvement of healing process in spite of surgical and medical treatments. MRI examinations were conclusive and compatible with abscess, so she underwent surgical intervention. Facial candidal abscess was the final diagnosis.

Conclusions

We concluded that, in persistent abscesses, invasive candidiasis should be considered in the differential diagnosis of bacterial infections as it generally affects individuals with diabetes or general defects in the immune system, or those who use widespread antibiotics and steroids.  相似文献   
42.
Hashitoxicosis is generally differentiated from Graves’ hyperthyroidism by its shorter course and absence of ophthalmopathy. In this case report, we describe an adolescent girl who presented with significant clinical findings of hyperthyroidism, a diffuse goiter with homogenously increased uptake in scintigraphy, and with ocular findings of ophthalmopathy. The thyroid stimulating hormone receptor antibody test was positive, and the family history revealed thyroid-associated ophthalmopathy. Clinical findings supported the diagnosis of Hashimoto’s disease (HD) in the follow-up period. Radioactive iodine uptake investigation was found to be a reliable method for differential diagnosis. Attention was drawn to the rarity of pediatric cases of HD who present with ophthalmopathy.  相似文献   
43.
Essential tremor is one of the most frequent movement disorders of humans and can be associated with substantial disability. Some but not all persons with essential tremor develop signs of Parkinson disease, and the relationship between the conditions has not been clear. In a six-generation consanguineous Turkish kindred with both essential tremor and Parkinson disease, we carried out whole exome sequencing and pedigree analysis, identifying HTRA2 p.G399S as the allele likely responsible for both conditions. Essential tremor was present in persons either heterozygous or homozygous for this allele. Homozygosity was associated with earlier age at onset of tremor (P < 0.0001), more severe postural tremor (P < 0.0001), and more severe kinetic tremor (P = 0.0019). Homozygotes, but not heterozygotes, developed Parkinson signs in the middle age. Among population controls from the same Anatolian region as the family, frequency of HTRA2 p.G399S was 0.0027, slightly lower than other populations. HTRA2 encodes a mitochondrial serine protease. Loss of function of HtrA2 was previously shown to lead to parkinsonian features in motor neuron degeneration (mnd2) mice. HTRA2 p.G399S was previously shown to lead to mitochondrial dysfunction, altered mitochondrial morphology, and decreased protease activity, but epidemiologic studies of an association between HTRA2 and Parkinson disease yielded conflicting results. Our results suggest that in some families, HTRA2 p.G399S is responsible for hereditary essential tremor and that homozygotes for this allele develop Parkinson disease. This hypothesis has implications for understanding the pathogenesis of essential tremor and its relationship to Parkinson disease.Essential tremor is one of the most frequent movement disorders in humans (1). It is characterized primarily by postural or kinetic tremor of the arms and hands, but head, legs, voice, and other regions of the body may also be affected (2). The worldwide prevalence is 0.9%, increasing to more than 4% in elderly populations (1). Familial essential tremor is genetically heterogeneous. Genetic linkage studies of multiply affected families revealed three genomic regions segregating with the condition, on chromosomes 3q13 [ETM1; Online Mendelian Inheritance in Man (OMIM) 190300], 2p22-24 (ETM2; OMIM 602134), and 6p23 (ETM3; OMIM 611456) (35). No clearly causal mutations have been identified in these regions, although the common variant DRD3 p.S9G in the ETM1 region has been proposed as a risk factor and HS1BP3 p.A265G in the ETM2 region appeared in two multiply affected families (6, 7). Genomewide association studies of essential tremor reported associations with common variants in an intron of LINGO1 and in an intron of SLC1A2 (810). Recently, DNAJC13 p.N855S, which had been identified in Parkinson disease patients, was also found in two unrelated patients with essential tremor (11). Nonsense mutation p.Q290X in the RNA-binding protein FUS was identified by whole exome sequencing in a large family with essential tremor (ETM4; OMIM 614782) (12). Screening other subjects with essential tremor for FUS revealed two rare missense variants, suggesting that mutations in FUS explain a subset of cases with the condition (13, 14).In this study, we examined a six-generation family segregating essential tremor, and in multiple relatives, essential tremor as a feature of Parkinson disease. We carried out whole exome sequencing of genomic DNA from three severely affected family members and subsequent pedigree analysis to identify the genetic basis of essential tremor and Parkinson disease in the family.  相似文献   
44.
Functional limitations for the vitamin K cycle, caused either by mutations in gamma-glutamyl carboxylase or vitamin K epoxide reductase genes, result in hereditary deficiency of vitamin K-dependent coagulation factors (VKCFD1 and VKCFD2, respectively). Patients suffering from VKCFD often share several other anatomical irregularities which are not related to haemostasis. Here we report on nine patients, eight of them previously unreported, who presented with VKCFD1. All were examined with special attention to vitamin K-dependent coagulation factors as well as to bone and heart development and to other anatomical signs of embryonal vitamin K deficiency. In total, we detected ten mutations in the gamma-glutamyl carboxylase gene of which seven have not been previously reported. Most interestingly, additional non-bleeding phenotypes were observed in all patients including midfacial hypoplasia, premature osteoporosis, cochlear hearing loss, heart valve defects, pulmonary stenosis, or pseudoxanthoma elasticum-like phenotype. Undercarboxylated matrix Gla protein, osteocalcin, and periostin appear to be responsible for these defects which are also observed in cases of fetal warfarin syndrome.  相似文献   
45.
46.
The aim of this study was to investigate the effects of aging on the central nervous system steroid and myelin basic protein (MBP) profiles. Forty-seven male Sprague-Dawley rats (newborn, 1, 6, 12 and 24-monthsold) were studied. Tissues were obtained from the cerebellum and parietal, frontal, temporal cortex of the central nervous system of the rats for steroid extraction. The estradiol, progesteron, testosterone and dehydroepiandrosterone (DHEA) levels were measured by Enzyme Linked Immunosorbent Assay (ELISA). The average levels of estradiol (pg/g), progesteron (ng/g), DHEA (ng/g) and testosterone (ng/g) in the brain tissues were respectively 24.29, 4.59, 0.27, 0.92 in the newborn-rats; 4.18 ± 1.10, 1.54 ± 0.30, 0.28 ± 0.01, 0.57 ± 0.10 in the 1 month-old-rats; 11.02 ± 1.10, 2.96 ± 0.30, 0.27 ± 0.01, 0.61 ± 0.10 in the 6 month-old-rats; 15.80 ± 1.10, 4.80 ± 0.30, 0.28 ± 0.10, 0.67 ± 0.10 in the 12 monthold- rats; 20.07 ± 1.10, 4.12 ± 0.30, 0.28 ± 0.01, 0.55±0.10 in the 24 month-old-rats. The myelin basic protein levels were determined by immunohistochemical staining and an elevation was observed in conjunction with the aging process. The results of the study indicate that the alterations in MBP, DHEA, progesterone, testosterone and estrodiol concentrations in the central nervous system of the rats during aging can be considered fundamental for future animal and human studies.  相似文献   
47.
Zn–Al layered double hydroxides (LDHs) were synthesized by a chemical method, while polyvinyl alcohol (PVA) nanofibers were fabricated by an electrospinning approach; we also synthesized Zn–Al LDH/cefotaxime (cefotax), Zn–Al LDH@PVA, and Zn–Al LDH/cefotax@PVA (LCP). Characterizations were performed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis techniques, dynamic light scattering, X ray-florescence, and carbon, hydrogen, and nitrogen (CHN) analyses. The adsorption isotherm of cefotax and its entrapment percentage, release, and kinetics were also investigated. The results confirmed the elemental constituents of the mentioned formulas, which exhibited different degrees of crystallinity and different morphologies. Besides, these formulas were tested in vitro as antimicrobial agents and applied in vivo against second-degree wound burns induced in rats'' skin. The adsorption of cefotax occurred chemically, and the experimental data were fitted with different isotherm models, where the Freundlich and Toth models gave the best fits. The entrapment percentage in LDH/cefotax was 77.41% and in LDH/cefotax@PVA, it was 67.83%. The sustained release of cefotax from LDH and LCP was attainable; the release percentages were 89.31% and 81.55% in up to 12 h, respectively. The release kinetics of cefotax from LDH fitted well with first-order kinetics, while that for LCP was parabolic. The formulas showed uneven antimicrobial effects against Gram-positive and Gram-negative bacteria; the best effect was exhibited by Zn–Al LDH/cefotax@PVA due to its sustained release. Finally, investigating the possibility of using these formulas in the clinical setting should be considered.

This study succeeded to formulate, characterize, and investigate cefotax release and kinetics, and to compare cetofax with other known antibacterial agents.  相似文献   
48.
We investigated the possible use of D -lactate as a predictor in the diagnosis of appendicitis. C-reactive protein level (CRP) and leukocyte counts were also evaluated. Venous blood D -lactate, CRP, and leukocyte counts were measured preoperatively in 53 patients undergoing surgery for appendicitis, as well as in 20 healthy subjects. Levels of all three parameters in the surgical patients were significantly higher than in the control group ( p < .05). Previous studies have shown that venous D -lactate is more specific to the intestine than CPR or leukocyte count. Based on our data, venous D -lactate, which had the lowest false-negative rate among these laboratory parameters, may be a useful diagnostic marker for appendicitis. None of these parameters were helpful in identifying the type of the appendicitis.  相似文献   
49.
Objective: We examined the cardioprotective effects of propofol and ketamine with and without N-acetylcysteine (NAC). Methods: 60 rats were divided into six groups of 10 rats each. Anesthesia induction was produced with an intraperitonal injection of ketamine in Groups 1–3 and propofol in Groups 4–6. NAC (200 mg kg? 1) was given intraperitonally during anesthesia induction in Groups 3 and 6. Groups 2, 3, 5, and 6 were subjected to 90 s of myocardial ischemia by clamping the ascending aorta, and then reperfusion was begun by unclamping the ascending aorta. After 60 min of reperfusion, blood samples were taken from the ascending aorta for biochemical analyses, and heart tissue samples were taken for biochemical and histopathological analyses. Results: Creatine kinase (CK), myocardial band of creatine kinase (CK-MB), and troponin-I (Tn-I) levels were significantly higher in the ischemia–reperfusion groups (2, 3, 5, 6) compared to the nonischemic groups (1, 4). CK, CK-MB, and Tn-I levels did not differ significantly between the ketamine groups (1–3) and the propofol groups (4–6) p >. 05). Malondialdehyde levels were significantly higher in Groups 2 and 3 than in Group 1 and were significantly lower in Groups 4 and 6 than in Group 5 (p <. 05). Malondialdehyde levels in the propofol groups (4–6) were significantly lower than in the ketamine groups (1–3; p <. 05). Catalase levels in propofol groups were higher than ketamine groups. Superoxide dismutase levels were significantly higher in Group 6 than in Group 3 (p <. 05). Conclusions: In this rat model of global cardiac ischemia, propofol with NAC attenuates myocardial injury more than ketamine (with or without NAC).  相似文献   
50.
ABSTRACT

Purpose/Aim: Acute mesenteric ischemia is a syndrome characterized by sudden onset abdominal pain followed by intestinal necrosis. Morbidity and mortality increase with delayed diagnosis. Even with the latest radiological diagnostic methods, early diagnosis and initiation of treatment can be delayed. Using an experimental model, here we aim to determine the relationship between the laboratory parameters used to detect acute mesenteric ischemia and the duration of irreversible ischemia. Materials and Methods: A total of 30 male Wistar albino rats were divided into five groups, all of which underwent general anesthesia: (i) Superior mesenteric artery (SMA) dissection with laparotomy was performed, and blood samples and intestinal segment samples were taken after 2 hr (Sham group); (ii) volvulus of one-third of the small intestines was performed manually by laparotomy, and blood samples and intestinal segment samples were taken after 2 hr (Volvulus group); (iii) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 2 hr (SMA+ligated 2-hr group); (iv) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 4 hr (SMA+ligated 4-hr group); and (v) SMA was ligated with laparotomy, and blood samples and intestinal segment samples were taken after 6 hr (SMA+ligated 6-hr group). Results: The mean lactate dehydrogenase (LDH) activities of the SMA+ligated 2-hr and SMA+ligated 6-hr groups were statistically higher than the control group (p = .004). Compared to the Sham and Volvulus groups, the mean lactate level of the SMA+ligated 6-hr group was significantly higher (p = .004). Compared to the Sham and Volvulus groups, the mean D-dimer levels of the SMA+ligated 4-hr and SMA+ligated 6-hr groups were significantly higher (p = .004 and .003, respectively). By histopathological evaluation, we found that pathological damage increased as the ischemia lengthened. Conclusions: Mesenteric ischemia leads to an irreversible loss of intestinal perfusion and an increase in parameters of ischemia. Irreversible tissue damage occurs after 4 hr of ischemia and peaks after 6 hr, whereas parameters of ischemia (D-dimer, LDH, and L-Lactate levels) are highest at 2 hr after the onset of ischemia.  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