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   48651篇
  免费   2306篇
  国内免费   394篇
耳鼻咽喉   537篇
儿科学   1006篇
妇产科学   591篇
基础医学   6441篇
口腔科学   937篇
临床医学   2875篇
内科学   12392篇
皮肤病学   1059篇
神经病学   3775篇
特种医学   2003篇
外科学   8584篇
综合类   185篇
一般理论   6篇
预防医学   1338篇
眼科学   1074篇
药学   3025篇
中国医学   184篇
肿瘤学   5339篇
  2023年   231篇
  2022年   518篇
  2021年   941篇
  2020年   512篇
  2019年   724篇
  2018年   986篇
  2017年   762篇
  2016年   951篇
  2015年   1048篇
  2014年   1348篇
  2013年   1709篇
  2012年   2744篇
  2011年   3084篇
  2010年   1753篇
  2009年   1597篇
  2008年   2899篇
  2007年   3160篇
  2006年   3161篇
  2005年   3180篇
  2004年   3274篇
  2003年   3292篇
  2002年   3290篇
  2001年   662篇
  2000年   601篇
  1999年   711篇
  1998年   807篇
  1997年   686篇
  1996年   642篇
  1995年   542篇
  1994年   486篇
  1993年   525篇
  1992年   448篇
  1991年   443篇
  1990年   384篇
  1989年   349篇
  1988年   339篇
  1987年   269篇
  1986年   242篇
  1985年   227篇
  1984年   197篇
  1983年   168篇
  1982年   149篇
  1981年   170篇
  1980年   146篇
  1979年   125篇
  1978年   118篇
  1977年   103篇
  1976年   77篇
  1975年   68篇
  1974年   58篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
71.
The pulmonary lesions were studied in 24 autopsy cases of Japanese patients with AIDS. The major pathological findings were opportunistic infections, which were the major clinical symptoms in some patients. The pathogens identified were as follows; Pneumocystis carinii (PC) in 10, cytomegalovirus (CMV) in 14, atypical mycobacterium in 5, cryptococcus in 2, candida in 2, and nocardia in 1. PC pneumonia was prominent in 8 cases and was the cause of death. In such patients, the lung were heavy and appeared parenchymatous. Histological examination revealed numerous protozoa in the foamy material in the alveolar spaces, associated with swelling of the alveolar lining cells and edematous thickening of the alveolar septa. In some cases, only hyaline membrane formation was prominent without foamy material in the alveolar spaces. Immunostaining with anti-PC monoclonal antibody or in-situ hybridization with oligopeptide demonstrated pathogens in the hyaline membranes. Many cases with PC pneumonia had concomitant opportunistic infections such as CMV, Herpes simplex virus, and atypical mycobacterium. Extrapulmonary infection of PC was seen in only one case. CMV infection was found in 14 cases; 7 had innumerable inclusion bodies, and in some cases the lesions were most prominent around the bronchioles. Of the 5 cases of atypical mycobacterial infection, 2 were caused by M. kansaii (MK) and 3 by M. avium intracellulare (MAI). Both lesions of MK infection showed necrosis and cavitation. One of three cases of MAI infection showed cavitation. Around the cavitary lesions, numerous cytomegalic inclusion bodies were identified in the mesenchymal cells, which may have been the cause of necrosis and cavitation of the lesions. MAI infection was systemic and pronounced in the lymph nodes, spleen, and intestinal mucosa. Neoplastic lesions comprised 2 cases of Kaposi's sarcoma and 4 of extranodal non-Hodgkin lymphoma in other organs. Lung involvement was seen in only one case of Kaposi's sarcoma although very small in size. The lesion was situated along the pulmonary vein and appeared hemorrhagic macroscopically. Pulmonary lesions in AIDS are complicated, and many of opportunistic pathogens were identified in single patients.  相似文献   
72.
Reduced expression of nm23 gene is implicated in high metastatic potential In a variety of malignancies. To elucidate the role of nm23 in human gastric carcinomas, we examined loss of heterozygosity (LOH) of nm23 gene by Southern blotting, nm23 mRNA expression by Northern blotting and nm23 protein expression by Western blotting as well as immunohistochemistry in both primary and metastatic tumors. LOH of nm23 gene was found in 2 (8%) out of the 23 informative gastric carcinomas. Twenty-two (84%) out of the 26 cases expressed nm23 mRNA at higher levels in primary tumor tissue than in corresponding non-neoplastic mucosa. No obvious correlation was observed between clinico-pathological features and LOH of nm23 gene or nm23 mRNA expression. On the other hand, 52% of the gastric carcinomas showed reduction of nm23 immunoreactivity in the metastatic tumor of regional lymph nodes, as compared to the primary tumor. Interestingly, 71% of the gastric carcinomas showed weaker nm23 immunoreactivity in the liver metastasis than in the primary tumor. These results suggest that nm23 overexpression is linked with development of gastric carcinomas and the decrease in expression of nm23 participates in metastasis.  相似文献   
73.
74.
An avulsion fracture of the tibial tubercle is a common injury in traffic accident. If the fracture is closed, then a comparatively good prognosis can be expected through reinforcement of the bone via osteosynthesis and the use of artificial ligaments. In this case, an open wound was observed in the tibial tubercle, and the wound was so polluted that the healing process was significantly delayed. It was therefore difficult to provide simultaneous surgical treatment and so three operations were required to perform the reconstruction of the extensor mechanism. The reconstruction of extensor mechanism and the frame fixation between the patella and tibia was performed. Six months after the injury, the patient was able to walk without aid, had a range of movement from 5°to 130°, and did not show any indications of ADL disorder. Using this method of frame fixation between the patella and tibia proved to be an effective technique for the reconstruction of the open knee extension mechanism injury.  相似文献   
75.
Off-pump surgery was performed in a patient with post-infarction angina complicated with aneurysmal coronary-pulmonary arterial fistula. Epicardial echocardiography localized the artery feeding the fistula in the myocardium, which had not been revealed by visual inspection, palpation, or transesophageal echocardiography. The patient underwent off-pump coronary artery bypass grafting concomitant with aneurysmectomy. The feeding arteries were dissected easily using a Harmonic Scalpel and ligated. The flow in the aneurysm disappeared immediately and aneurysmectomy was performed without bleeding.  相似文献   
76.
Background: Although isoflurane, a volatile anesthetic, can block the motor response to noxious stimulation (immobility and analgesia) and suppress autonomic responsiveness, how it exerts these effects at the neuronal level in the spinal cord is not fully understood.

Methods: The effects of a clinically relevant concentration (1 rat minimum alveolar concentration [MAC]) of isoflurane on electrically evoked and spontaneous excitatory/inhibitory transmission and on the response to exogenous administration of the [gamma]-aminobutyric acid type A receptor agonist muscimol were examined in lamina II neurons of adult rat spinal cord slices using the whole cell patch clamp technique. The effect of isoflurane on the action potential-generating membrane property was also examined.

Results: Bath-applied isoflurane (1.5%, 1 rat MAC) diminished dorsal root-evoked polysynaptic but not monosynaptic excitatory postsynaptic currents. Glutamatergic miniature excitatory postsynaptic currents were also unaffected by isoflurane. In contrast, isoflurane prolonged the decay phase of evoked and miniature [gamma]-aminobutyric acid type A receptor-mediated inhibitory postsynaptic currents and increased the amplitude of the muscimol-induced current. Isoflurane had little effect on action potential discharge activity.  相似文献   

77.
BACKGROUND: Mutations in the human SLC4A1 (AE1/band 3) gene are associated with hereditary spherocytic anaemia and with distal renal tubular acidosis (dRTA). The molecular diagnosis of AE1 mutations has been complicated by the absence of highly polymorphic genetic markers, and the pathogenic mechanisms of some dRTA-associated AE1 mutations remain unclear. Here, we characterized a polymorphic dinucleotide repeat close to the human AE1 gene and performed an immunocytochemical study of kidney tissue from a patient with inherited dRTA with a defined AE1 mutation. METHODS: One CA repeat region was identified in a phage P1-derived artificial chromosome (PAC) clone containing most of the human AE1 gene and the upstream flanking region. We determined its heterozygosity value in multiple populations by PCR analysis. Genotyping of one family with dominant dRTA identified the AE1 R589H mutation, and family member genotypes were compared with the CA repeat length. AE1 and vH(+)-ATPase polypeptides in kidney tissue from an AE1 R589H patient were examined by immunocytochemistry for the first time. RESULTS: This CA repeat, previously reported as D17S1183, is approximately 90 kb upstream of the AE1 gene and displayed considerable length polymorphism, with small racial differences, and a heterozygosity value of 0.56. The allele-specific length of this repeat confirmed co-segregation of the AE1 R589H mutation with the disease phenotype in a family with dominant dRTA. Immunostaining of the kidney cortex from one affected member with superimposed chronic pyelonephritis revealed vH(+)-ATPase-positive intercalated cells in which AE1 was undetectable, and proximal tubular epithelial cells with apparently enhanced apical vH(+)-ATPase staining. CONCLUSIONS: The highly polymorphic dinucleotide repeat adjacent to the human AE1 gene may be useful for future studies of disease association and haplotype analysis. Intercalated cells persist in the end-stage kidney of a patient with familial autosomal dominant dRTA associated with the AE1 R589H mutation. The absence of detectable AE1 polypeptide in those intercalated cells supports the genetic prediction that the AE1 R589H mutation indeed causes dominant dRTA.  相似文献   
78.
Morphological analyses in and around the epiphyseal cartilage of mice deficient in insulin receptor substrate-1 (IRS-1) showed IRS-1 signaling to be important for skeletal growth by preventing early closure of the epiphyseal cartilage and maintaining the subsequent bone turnover at the primary spongiosa. Introduction: IRS-1 is an essential molecule for intracellular signaling by IGF-I and insulin, both of which are potent anabolic regulators of cartilage and bone metabolism. To clarify the role of IRS-1 signaling in the skeletal growth, morphological analyses were performed in and around the epiphyseal cartilage of mice deficient in IRS-1 (IRS-1(-/-)), whose limbs and trunk were 20-30% shorter than wildtype (WT) mice. MATERIALS AND METHODS: The epiphyseal cartilage and the primary spongiosa at proximal tibias of homozygous IRS-1(-/-) and WT male littermates were compared using histological, immunohistochemical, enzyme cytohistochemical, ultrastructural, and bone histomorphometrical analyses. RESULTS: In and around the WT epiphyseal cartilage, IRS-1 and insulin-like growth factor (IGF)-1 receptors were widely expressed, whereas IRS-2 was weakly localized in bone cells. Chronological observation revealed that height of the proliferative zone and the size of hypertrophic chondrocytes were decreased in WT mice as a function of age, and these decreases were accelerated in the IRS-1 (-/-) cartilage, whose findings at 12 weeks were similar to those of WT at 24 weeks. In the IRS-1(-/-) cartilage, proliferating chondrocytes with positive proliferating cell nuclear antigen (PCNA) or parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor immunostaining had almost disappeared by 12 weeks. Contrarily, TUNEL+ apoptotic cells were increased in the hypertrophic zone, at the bottom of which most of the chondrocytes were surrounded by the calcified matrix, suggesting the closure of the cartilage. In the primary spongiosa, bone volume, alkaline phosphatase (ALP)+ osteoblasts, TRACP+ osteoclasts, and the osteopontin-positive cement line were markedly decreased. Bone histomorphometrical parameters for both bone formation and resorption were significantly lower in IRS-1(-/-) mice, indicating the suppression of bone turnover. CONCLUSION: The IRS-1(-/-) epiphyseal cartilage exhibited insufficient proliferation of chondrocytes, calcification of hypertrophic chondrocytes, acceleration of apoptosis, and early closure of the growth plate. Thus, the data strongly suggest that IRS-1 signaling is important for the skeletal growth by preventing early closure of the epiphyseal cartilage and by maintaining the subsequent bone turnover at the primary spongiosa.  相似文献   
79.
Adamantinoma is a rare low-grade malignant bone tumor with an indolent course. The tibia is involved in 85%–90% of long-bone cases. We encountered a patient with primary adamantinoma of the proximal femur. A 60-year-old woman fell and fractured her proximal left femur in the area of a cystic lesion. She underwent an osteosynthesis procedure, and bone union was obtained. After 3 years she developed pain in the left thigh, and a radiographic abnormality was found at the fracture site. A metastatic bone tumor was suspected, and curettage and cementing were carried out. Histologically, we found an epithelial component but failed to detect any primary cancer. Local recurrence became evident after another 6 years. A marginal excision was performed and a bipolar femoral prosthesis was implanted. We finally diagnosed the patient with adamantinoma. In this report we describe the characteristics of this tumor and discuss the reasoning concerning the differential diagnosis and therapeutic plan.  相似文献   
80.
Effects of dominant and nondominant eyes in binocular rivalry.   总被引:1,自引:0,他引:1  
PURPOSE: To investigate the relation between sighting and sensory eye dominance and attempt to quantitatively examine eye dominance using a balance technique based on binocular rivalry. METHODS: The durations of exclusive visibility of the dominant and nondominant eye target in binocular rivalry were measured in 14 subjects. The dominant eye was determined by using the hole-in-card test (sighting dominance). In study 1, contrast of the target in one eye was fixed at 100% and contrast of the target in the other eye was varied from 100% to 80% to 60% to 40% to 20%, when using rectangular gratings of 1, 2, and 4 cycles per degree (cpd) at 2 degrees, 4 degrees , and 8 degrees in size. In study 2, contrast of the target in the nondominant eye was fixed at 100% and contrast of the target in the dominant eye was varied from 100% to 80% to 60% to 40% to 20%, when using a rectangular grating of 2 cpd at 4 degrees in size. RESULTS: In study 1, the total duration of exclusive visibilities of the dominant eye target; that is, the target seen by the eye that had sighting dominance was longer compared with that of the nondominant eye target. When using rectangular gratings of 4 cpd, mean total duration of exclusive visibility of the dominant eye target was statistically longer than that of the nondominant eye target (p < 0.05). In study 2, reversals (in which duration of exclusive visibility of the nondominant eye becomes longer than the dominant eye when the contrast of the dominant eye target is decreased) were observed for all contrasts except for 100%. CONCLUSIONS: The dominant sighting eye identified by the hole-in-card test coincided with the dominant eye as determined by binocular rivalry. The contrast at which reversal occurs indicates the balance point of dominance and seems to be a useful quantitative indicator of eye dominance to clinical applications.  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