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   38547篇
  免费   2600篇
  国内免费   57篇
耳鼻咽喉   574篇
儿科学   1571篇
妇产科学   1252篇
基础医学   5434篇
口腔科学   1907篇
临床医学   3781篇
内科学   6837篇
皮肤病学   589篇
神经病学   3670篇
特种医学   1194篇
外科学   4989篇
综合类   197篇
一般理论   7篇
预防医学   3390篇
眼科学   665篇
药学   2699篇
中国医学   48篇
肿瘤学   2400篇
  2023年   258篇
  2022年   367篇
  2021年   644篇
  2020年   551篇
  2019年   720篇
  2018年   901篇
  2017年   754篇
  2016年   801篇
  2015年   835篇
  2014年   996篇
  2013年   1616篇
  2012年   1947篇
  2011年   1931篇
  2010年   1147篇
  2009年   1163篇
  2008年   1648篇
  2007年   1757篇
  2006年   1721篇
  2005年   1724篇
  2004年   1471篇
  2003年   1412篇
  2002年   1291篇
  2001年   1084篇
  2000年   1044篇
  1999年   989篇
  1998年   427篇
  1997年   363篇
  1996年   323篇
  1995年   323篇
  1994年   304篇
  1993年   245篇
  1992年   768篇
  1991年   721篇
  1990年   758篇
  1989年   742篇
  1988年   698篇
  1987年   674篇
  1986年   605篇
  1985年   561篇
  1984年   510篇
  1983年   393篇
  1982年   252篇
  1981年   219篇
  1979年   363篇
  1978年   265篇
  1977年   216篇
  1975年   237篇
  1974年   258篇
  1973年   224篇
  1972年   211篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A case, referred to the Department of Stomatognathic Physiology, G?teborg, with an unstable occlusion is presented. There was a facial asymmetry and the bony morphology differed markedly between the sides. No EMG activity in the masticatory muscles could be detected on the left side. It was diagnosed as a probable sequela to poliomyelitis in the childhood. The impact of altered muscle function on the bony structures and dentition is discussed.  相似文献   
62.
63.
Psychiatric disturbances are common in primary hyperparathyroidism (HPT), but their pathogenesis is essentially unknown. This study deals with cerebrospinal fluid (CSF) calcium homeostasis and its connection with parathyroid hormone (PTH), blood-brain barrier (BBB) function, and central monoamine and purine metabolites in patients with primary HPT. In 22 patients with primary HPT (serum calcium 2.85 +/- 0.21 mmol/l), the CSF concentrations of total and ionized calcium were higher (1.21 +/- 0.08 mmol/l, p less than 0.01, and 1.09 +/- 0.05 mmol/l, p less than 0.001, respectively) than in 11 normocalcemic reference subjects. The values correlated with serum calcium concentration (p less than 0.001) and CSF/serum albumin ratio, a measure of BBB permeability. The latter ratio was elevated in one-third of the patients with HPT, indicating BBB damage. CSF immunoreactive intact PTH was higher in the HPT patients than in the reference group (p less than 0.05), and serum and CSF PTH were positively correlated (p less than 0.05). The CSF levels of the monoamine metabolites 5-hydroxyindoleacetic acid (5HIAA) and homovanillic acid (HVA) were lower, and the level of urate in CSF was higher, in the HPT patients than in the reference subjects, while there were no consistent differences in CSF hypoxanthine or xanthine. CSF 5HIAA correlated inversely with CSF ionized calcium (r = -0.42, p = 0.02). After parathyroid surgery, CSF calcium and urate decreased significantly and CSF monoamine metabolites increased slightly. The decrease in CSF ionized calcium correlated with the alleviation of psychiatric symptoms. The results indicate the importance of increased CSF calcium concentrations in patients with primary HPT and suggest a relation between central calcium regulation and central turnover of monoamines.  相似文献   
64.
The work situation of 66 male patients who underwent elective coronary artery bypass surgery (CABS) and who had been randomly allocated to receive cardiac rehabilitation (group R) was compared with the work situation of 59 similar patients allocated to receive only standard care (group H). The follow-up time was one year. The proportions of subjects working in groups R and H were 26% and 20% (p=ns) before the CABS, 45% and 34% (p=ns) 6 months and 56% and 38% (p=ns) 12 months after the CABS, repectively. The increase in proportion of subjects who worked was significant in both groups at both 6 and 12 months after the CABS (p<0.05 for all changes). The increases were not significantly different between the whole groups, but in patients younger than 55 years of age, return to work was more frequent in group R than in group H (at 12 months 60% vs. 35%, p for the difference in change=0.02). Stepwise logistic regression analysis of the factors influencing return to work showed that a patient's judgement of his own working capacity as good 6 months after CABS (odds ratio (OR) 8.5, confidence interval (CI) 2.3–32.0), functional class 16 months after the CABS (OR 6.7, CI 1.8–24.5), his desire to work (OR 6.4, CI 1.6–26.0) and absence from work of less than 3 months before the CABS (OR 4.9, CI 1.2–20.2) were significant positive predictors of return to work 1 year after the CABS.  相似文献   
65.
Fifty renal biopsies were studied by immunoelectron microscopy after embedding in a partly hydrophilic polyacrylic resin (LR White). Immunofluorescence studies were carried out on frozen sections of parallel tissue samples. Polyacrylic embedding gave good preservation of the renal ultrastructure and precise localization of immunoglobulin and C3c antibodies within glomerular electron-dense deposits. Non-specific staining of plasma proteins within vascular lumina could easily be detected. There was good correlation between immunoelectron and immunofluorescence microscopy. Immunoelectron microscopy is a very sensitive method, which can detect small amounts of antigen. More cases were, however, positive by immunofluorescence than by immunoelectron microscopy. This discrepancy may be explained by difference in sample size, and by difference in resolution of morphological details (electron microscopy versus fluorescence microscopy).  相似文献   
66.
Factorial experimental design was used to study the protective effects of Zn and Cu on cadmium-metallothionein(CdMT)-induced nephrotoxicity in male Wistar rats. In the factorial design two levels of Zn (0 and 25 mg/kg body weight), two levels of Cu (0 and 12.5 mg/kg), and two levels of CdMT (0.1 and 0.4 mg of Cd/kg) were used as varied factors. The factorial design was complemented with a center point with all three variables at an intermediate setting, i.e., Zn at 12.5 mg/kg, Cu at 6.25 mg/kg, and CdMT at 0.25 mg Cd/kg. Each of the nine combinations of settings was administered to one of nine groups with six rats in each. Zn and Cu were injected sc 24 hr prior to the injection of CdMT. The concentrations of protein and Ca in urine and Ca in renal cortex were used as effects. The relationship between the experimental design settings and the effects were modeled with multiple regression. The multiple regression analysis revealed that for the high dose of CdMT (i) the enhanced values of protein in urine caused by CdMT injection could be more efficiently reduced by Zn than by Cu, and (ii) excessive Ca in urine and renal cortex could be more efficiently reduced by Cu than by Zn. No significant synergism or antagonism between Cu and Zn was found. These models can be used to estimate the dose levels of Zn and Cu which will reduce the toxic effects of CdMT. The treatment of 20.4 mg/kg Zn, for example, will reduce the effects of 0.4 mg Cd/kg as CdMT on protein in urine, and 2.8 mg/kg Cu will reduce the Ca in urine to the levels of those caused by 0.25 mg Cd/kg (no Zn and Cu). Similarly, the effect of 0.4 mg Cd/kg on Ca level in renal cortex can be reduced to that of 0.28 mg Cd/kg as CdMT by 7.98 mg Cu/kg, which is three times as efficient as Zn. The obtained results might be of importance in understanding the mechanism of cadmium toxicity and the potential risk to the health of the population exposed to cadmium occupationally or environmentally.  相似文献   
67.
The incidence of lymphoid malignancies (acute leukemias and myelomatosis excluded) during 1969-1987 in the County of Uppsala was calculated on the basis of the regional cancer register and local registers from the only oncological, hematological, dermatological and pathological departments in this well-defined geographical area. Of the 774 patients included, 639 had histopathological specimens available, all of which were re-examined. Seventy-nine patients were diagnosed on the basis of bone marrow investigations (greater than 70% re-examined, all had a low-grade non-Hodgkin's lymphoma = NHL) and 54 on fine-needle aspiration biopsies (not re-examined). Seventy-nine of the lymphoma diagnoses were based on autopsy specimens. The overall age standardized incidence was 16.2/100,000/year (NHL: 13.6, Hodgkin's disease = HD: 1.5) according to the Swedish 1970 census (according to world standard population: 10.2); male: 20.9 (12.9) and female: 12.4 (7.9). The annual change in trend was +3.0% +/- 2.6 (NHL: +3.6% +/- 2.4, HD: no change). The omission of the 54 'fine needle cases' led to an overall incidence of 15.0 (9.7) and an annual change in trend of +3.5% +/- 1.9. Among the histopathological specimens, an NHL was found in 524 patients and HD in 69. In 46 registered patients, the diagnosis malignant lymphoma was wrong. The diagnosis changed to NHL in 43 patients registered as HD.  相似文献   
68.
Rett syndrome (RS) is a disease of neurological development. First reported 30 years ago in 1966, its biological and genetic basis remains obscure. RS is commonly thought of as an X linked dominant disorder lethal to hemizygous males. The few familial cases would arise through mosaicism or because of occasional females failing to manifest the disorder through skewed X inactivation in relevant cell types. We have one family where the mother and daughter are affected with RS, and which can be explained according to this hypothesis. If the alternative proposal of Thomas (1996) is correct, that the lack of males affected by such disorders is the result of a high male to female ratio of germline mutations rather than of gestational lethality, then the RS gene should be located on the grandpaternal chromosome. Genomic screening with markers covering the whole X chromosome has been performed. Studies using multiple informative markers indicate that the RS locus is likely to be located close to one of the X chromosome telomeres. Further investigations in eight additional families suggest the most likely region for the RS gene to be is the distal part of Xq (Xq28).  相似文献   
69.
JC virus (JCV) infection is regularly asymptomatic in healthy individuals. In contrast, in immunocompromised individuals, highly activated virus replication may lead to PML. Peripheral blood cells (PBCs) are found to habor JCV DNA in healthy and diseased individuals and it is discussed that they might be responsible for dissemination of the virus to the central nervous system (CNS) during persistence. To better understand the role of JCV DNA in PBCs for persistent infection and pathogenesis, the authors characterized the extent of JCV infection in Ficoll-gradient purified blood cells (peripheral blood mononuclear cells [PBMCs]) of healthy and human immunodeficiency virus type 1 (HIV-1)-infected individuals. Virus activation in PBMCs from healthy JCV-infected individuals was found at a rate of 0% to 38% at low polymerase chain reaction (PCR) sensitivity. In progressive multifocal leukoencephalopathy (PML) patients, a stronger signal was found, indicating increased virus activation. JCV DNA was regularly detected in T and B lymphocytes and in monocytes at low levels. However, granulocytes were shown to be the predominant reservoir of JCV DNA harboring high copy numbers. Although the overall distribution of viral genomes holds true for the population studied, in the individual, a markedly changed pattern of distribution can be found.  相似文献   
70.
In knee arthroplasty, component malpositioning seems to be a fundamental cause for failure. The degree of malpositioning is important. To investigate this degree, 86 of 137 knee arthroplasties performed with the Townley semiconstrained bicondylar prosthesis were examined after a mean follow-up period of 6.5 years (range, 5.0-8.5 years). Five arthroplasties were excluded because of aseptic loosening, but none of these showed malalignment in postoperative roentgenograms. Clinical results and the patients' reports on deterioration of prosthetic function were correlated with positioning of the prosthetic components. Total alignment between 6 degrees of varus and 7 degrees of valgus was associated with good clinical results. Total alignment of more than 7 degrees of valgus, anterior tilting of the tibial component, or positioning of the femoral component in more than 12 degrees of valgus correlated with relatively poor clinical results.  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