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   21291篇
  免费   961篇
  国内免费   112篇
耳鼻咽喉   152篇
儿科学   309篇
妇产科学   204篇
基础医学   2581篇
口腔科学   524篇
临床医学   1310篇
内科学   4916篇
皮肤病学   1233篇
神经病学   2017篇
特种医学   801篇
外科学   3584篇
综合类   141篇
预防医学   482篇
眼科学   336篇
药学   1856篇
中国医学   62篇
肿瘤学   1856篇
  2023年   93篇
  2022年   187篇
  2021年   366篇
  2020年   187篇
  2019年   245篇
  2018年   368篇
  2017年   280篇
  2016年   389篇
  2015年   419篇
  2014年   505篇
  2013年   599篇
  2012年   967篇
  2011年   1051篇
  2010年   625篇
  2009年   516篇
  2008年   951篇
  2007年   1026篇
  2006年   1001篇
  2005年   1037篇
  2004年   1043篇
  2003年   1029篇
  2002年   1015篇
  2001年   647篇
  2000年   711篇
  1999年   689篇
  1998年   337篇
  1997年   247篇
  1996年   240篇
  1995年   197篇
  1994年   182篇
  1993年   165篇
  1992年   481篇
  1991年   431篇
  1990年   421篇
  1989年   442篇
  1988年   413篇
  1987年   389篇
  1986年   331篇
  1985年   299篇
  1984年   190篇
  1983年   162篇
  1982年   96篇
  1979年   173篇
  1978年   99篇
  1977年   94篇
  1976年   78篇
  1975年   79篇
  1974年   80篇
  1973年   85篇
  1972年   88篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Male F344 rats were treated with lead nitrate and changes inthe expression and induction of P450IA subfamily enzymes anda placental form of glutathione-S-transferase (GST-P) in theliver were assessed by means of a bacterial mutation test, immunoblottingwith a monoclonal antibody reactive to P450IA1/IA2 and anti-GST-Psera and Northern blotting with P450IA2 cDNA as a probe. Treatmentof rats with lead nitrate (20, 50 or 100 µmol/kg bodywt) decreased P450IA2 mRNA and protein in the liver in the dose-dependentfashion and also decreased the microsomal activity for P450IA2-dependentmutagenization of aromatic amines. Pretreatment of rats withlead nitrate suppressed the inductions of both P450IA2 mRNAand protein by an inducer of P450IA subfamily enzymes in theliver. In addition, amount of the induced P450IA2 was decreasedalong with increase in that of the induced GST-P.  相似文献   
52.
Background: Pancreatic carcinoma is one of the most lethal cancers. Because pancreatic carcinoma is still very difficult to diagnose in its early stage, many of these patients will be considered unsuitable for surgery. If a cytological diagnosis is obtained at initial endoscopic retrograde cholangiopancreatography (ERCP), suitable treatment will be initiated without delay. Methods: To increase the number of exfoliated cells from the pancreatic duct, we devised a new technique, pancreatic duct lavage fluid (PDLF), following bronchoalveolar lavage fluid. The present paper reports the effectiveness of cytological examination using PDLF in the diagnosis of pancreatic carcinoma. We examined 18 pancreatic carcinoma cases. After the endoscopic retrograde pancreatography (ERP), PDLF was collected from a double‐lumen catheter inserted into the main pancreatic duct. Saline injected from the lumen for the injection, and PDLF was aspirated from the other lumen for the guidewire at the same time. The cytological examination was performed using PDLF. Results: Exfoliated cells were more frequently found in PDLF from all patients. In 15 cases (83%), cytological examination of PDLF revealed positive cytological results as the diagnosis of pancreatic carcinoma. Conclusion: Cytological examination using PDLF has a high sensitivity for detection of pancreatic carcinoma. The new examination, PDLF, is simple, safe and effective, so we expect PDLF to become widely popular.  相似文献   
53.
OBJECTIVE: To evaluate the influence of the age at disease onset on the clinical symptoms, laboratory findings, treatment, and complications of microscopic polyangiitis (MPA). PATIENTS: From 1999 to 2001, we encountered 4 MPA patients with disease onset at age 65 or older (average 77.3, all were female: the elderly group). For comparison, 4 MPA patients with disease onset a 64 years or younger (average 44.7, two were male: the non-elderly group) were used. RESULTS: There was no statistically significant difference in clinical features between the two groups. All patients in the elderly group were referred to our hospital, because of fever of unknown origin or suspicion of connective tissue disease. The elderly group had a longer duration from the first admission to the start of treatment. Renal biopsies were done in all of the non-elderly group and one of the elderly group. The diagnosis of the other 3 patients of the elderly group was based on muscle or nerve biopsy, showing necrotizing vasculitis. At the time of diagnosis, antibodies to myeloperoidase (MPO-ANCA) were positive in 7 of 8 patients (87.5%). 2 patients of the non-elderly group were died of heart failure and hepatic failure by cyclophosphamide (CYC). The other 6 patients achieved substantial improvement. CONCLUSIONS: Muscle or nerve biopsy helped clinical management of elderly patients when renal biopsies could not be done. IVCY was relatively safe and effective treatment for MPA in elderly as well as non-elderly patients.  相似文献   
54.
55.
Summary We observed a rare cerebrovascular anomaly in a patient with brain-stem infarction. Two right vertebral arteries arose from the subclavian artery and communicated directly with each other under the transverse foramen of the fourth cervical vertebra. The left vertebral artery consisted of a rudimentary artery that arose from the left subclavian artery, ran through the transverse foramen of the sixth cervical vertebra and then tapered down to disappear at the fourth/fifth cervical vertebrae, plus a second, accessory artery that arose from a branch of the left thyrocervical trunk, ran through the transverse foramen of the fifth cervical vertebra and tapered off to disappear at the first/second cervical vertebrae.  相似文献   
56.
The absorption and endogenous excretion of iron in man was studied by monitoring the fecal excretion of a stable iron isotope (58Fe). The study was carried out for 12 healthy volunteers who were divided into two groups. Group I received 58Fe-labeled ferric ammonium citrate (III) (58FeAC) equivalent to 6 mg of iron as a control, and group II received a combination of 500 mg of vitamin C and 58FeAC. A new formula was used to calculate the 58Fe absorption ratio reflecting the pool of iron in the intestinal cells, and the ratio was compared with that obtained from Janghorbani's formula, which has been used as one of the common methods. As a result, the 58Fe absorption ratio in group II was statistically significantly higher than that of group I (34.4 +/- 6.1% vs. 15.0 +/- 5.5%, M +/- SD) using Janghorbani's formula. The similar absorption ratio (34.1 +/- 6.0% vs. 14.8 +/- 5.5%) was also obtained by our new formula. Our results confirmed the previous findings that the availability of iron is stimulated by the supplementation of vitamin C. Both formulae agreed in the absorption of iron, indicating that the endogenous excretion of iron (caused by the desquamated cells) in the intestine does not disguise the iron absorption.  相似文献   
57.
Development of a new wound dressing with antimicrobial delivery capability   总被引:1,自引:0,他引:1  
A bilaminar wound dressing composed of an outer membrane and an inner three-dimensional matrix of a fabric or a sponge may be considered to constitute an ideal structure that promotes wound healing: the outer membrane prevents body fluid loss, controls water evaporation, and protects the wound surface from bacterial invasion, and the inner matrix encourages adherence by tissue growth into the matrix. Using this concept, we developed a biosynthetic wound dressing with a drug delivery capability. This medicated wound dressing is composed of a spongy sheet of a chitosane derivative and collagen mixture that is laminated to an antimicrobial-impregnated polyurethane membrane. In this study, a gentamycin sulfate-impregnated wound dressing was prepared and evaluated. The antimicrobial efficacy of this wound dressing was examined on an agar plate seeded with Pseudomonas aeruginosa. Also, the cytotoxicity of an antimicrobial released from this wound dressing was examined in an in vitro system with cultured skin substitutes. Both in vitro tests have shown that this wound dressing is capable of suppressing bacterial growth and minimizing cellular damage. In addition, in the treatment of wounds inflicted on rats and rabbits, this wound dressing was shown to be efficacious in covering full-thickness and split-thickness skin defects. Finally, the efficacy of this wound dressing was evaluated in a nonrandomized open-label study of 31 clinical cases. In 31 cases treated with this wound dressing, good or excellent wound healing was achieved.  相似文献   
58.
Prostatic cancer is one of the most common malignant tumors in the field of urology. The number of patients is increasing rapidly and its importance as a mortal disease is gathering attention. In 1985, we organized a registration system for prostatic cancer patients found in and around Gunma prefecture. In this study, we analyzed the clinical characteristics of the 730 patients registered from 1985 to 1989. The results were as follows. Mean age was 74.0 years old and the number of the patients was the greatest in the eighth decade. Voiding disturbance was the most common chief complaint, followed by pollakisuria, gross hematuria and miction pain. Stage and grade distribution were as follows. Stage A 16.2%, B 21.1%, C 17.0%, D 45.7%, well differentiated 27.4%, moderately differentiated 48.2% and poorly differentiated 24.5%, respectively. A statistically significant relationship between stage and grade was observed. Bone was the most common metastatic site. The highest incidence of bone metastasis was in lumbar vertebra, followed by ribs, ilium, thoracic vertebra and ischium. The value of PAP, ALP and ESR tended to be higher in high stage patients, and that of Hb was lower. Fifty two patients were detected by mass screening. Most of these patients were in an early stage. Most of the patients were treated by hormonal therapy. LH-RH agonists constituted 39.2% of the cases given hormonal therapy.  相似文献   
59.
With the advent of magnetic resonance imaging (MRI), the neurohypophyseal system can be clearly delineated and its functional integrity can be predicted. The authors describe seven cases of central diabetes insipidus (DI) that occurred spontaneously. MRI revealed that the normal hyperintensity of the pituitary posterior lobe, which has been thought to be the neurosecretory material containing antidiuretic hormone, was absent in all cases. In addition, enlargement of a part of the neurohypophyseal system was recognized in five of seven cases on MRI. Three of the five patients with enlargement of a part of the neurohypophyseal tract underwent biopsy and were demonstrated to have chronic inflammation of the neurohypophyseal system. It was demonstrated that the enlarged parts of the neurohypophyseal system had shrunk either spontaneously or after the biopsy in four of the five cases. All patients are alive and have not experienced progression or remission of the disease. This study indicates that some cases of idiopathic DI result from a tiny mass lesion, usually nonneoplastic, localized in the neurohypophyseal system.  相似文献   
60.
US findings of 81 patients with breast cancer were analyzed respectively to evaluate the usefulness of US in the preoperative diagnosis of internal mammary mode metastases. The internal mammary area (I.M.A.) in which internal mammary nodes lie was shown as a hypoechoic stripe in a sagittal scan along the sternum and as a triangular or spindle-shaped hypoechoic area in a transverse scan in the intercostal space. The US features of each I.M.A. in the first three intercostal spaces were divided into three patterns: Pattern-A wad defined as widening of the ipsilateral side of the I.M.A. compared with the contralateral side; Pattern-C was defined as normal at both sides of the I.M.A. Pathological examination confirmed the node metastases in 85.7% of intercostal scans showing Pattern-A and in 35% of intercostal scans showing Pattern-B. Only one of 189 intercostal scans showing Pattern-C had nodal metastases. The overall accuracy was 88.1% in 243 intercostal scans and 90.1% in 81 patients. We conclude that US is useful in the detection of internal mammary node metastases in patients with breast cancer.  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