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   16048篇
  免费   1011篇
  国内免费   54篇
耳鼻咽喉   341篇
儿科学   519篇
妇产科学   436篇
基础医学   2247篇
口腔科学   329篇
临床医学   1408篇
内科学   2707篇
皮肤病学   611篇
神经病学   1517篇
特种医学   951篇
外科学   2747篇
综合类   171篇
一般理论   19篇
预防医学   889篇
眼科学   431篇
药学   772篇
中国医学   6篇
肿瘤学   1012篇
  2022年   90篇
  2021年   189篇
  2020年   107篇
  2019年   190篇
  2018年   278篇
  2017年   224篇
  2016年   287篇
  2015年   302篇
  2014年   446篇
  2013年   564篇
  2012年   681篇
  2011年   715篇
  2010年   498篇
  2009年   484篇
  2008年   646篇
  2007年   748篇
  2006年   691篇
  2005年   672篇
  2004年   608篇
  2003年   572篇
  2002年   595篇
  2001年   520篇
  2000年   519篇
  1999年   483篇
  1998年   294篇
  1997年   275篇
  1996年   259篇
  1995年   208篇
  1994年   211篇
  1993年   153篇
  1992年   343篇
  1991年   341篇
  1990年   283篇
  1989年   318篇
  1988年   267篇
  1987年   251篇
  1986年   278篇
  1985年   249篇
  1984年   179篇
  1983年   144篇
  1982年   105篇
  1981年   106篇
  1979年   130篇
  1978年   104篇
  1977年   92篇
  1976年   94篇
  1975年   93篇
  1974年   101篇
  1973年   109篇
  1971年   95篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
51.
OBJECTIVE: Although cutaneous leishmaniasis (CL) occurs mostly in the facial area, periocular involvement accounts for 2-5% of the facial lesions. CL lesions localized in the periocular region can easily be confused with various other diseases. The aim of this study was to examine the frequency of periocular involvement in CL in the Cukurova region of Turkey, as well as the clinical characteristics, diagnosis and methods of treatment of this disease. METHODS: Between December 1998 and December 2004, patients who were diagnosed with CL were evaluated prospectively with respect to periocular involvement. RESULTS: From the 2066 patients evaluated with CL, 2622 lesions were identified. In 59 (2.9%) of these patients, a total of 66 (2.5%) lesions were located in the periocular area. Thirty-two (48.5%) of these lesions were of the papular type, 15 (22.7%) the nodulo-ulcerative type, 10 (15.2%) the plaque type, and nine (13.6%) the nodular type. Dacryocystitis was identified in four patients with periocular involvement. Over the follow-up period, no ocular or periocular deformities or complications developed in these patients. CONCLUSION: Patients suspected of CL should be evaluated and treated early in the course of their disease to prevent any permanent ocular or periocular deformities.  相似文献   
52.
53.
Between 1974 and 1984, 173 patients were treated for squamous cell carcinoma of the tongue base. Fifty-four patients had T1 or T2 primaries, while 115 patients had T3 or T4 tumors (4 were not staged). Lymph node metastasis was present in 120 patients. Early primary tumors treated with surgery or radiotherapy had a control rate of 83% (5 of 6 tumors) and 89% (40 of 45 tumors), respectively. For advanced primary tumors, definitive radiotherapy produced a local control rate of 55% (42 of 76 tumors), compared with 79% (23 of 29 tumors) for surgery and postoperative radiotherapy. If primary control was obtained, the regional failure rate was less than 10%. Tumor growth patterns were predictive of the response to radiotherapy. The primary control rate at 2 years for 21 patients with exophytic tumors was 84% as opposed to 58% for 62 patients with ulcerative-infiltrative tumors (p = 0.04). Radiotherapy is effective for early stage or exophytic tumors, whereas for advanced or deeply invasive tumors combined therapy enhances local control.  相似文献   
54.
Marked neovascularization is a hallmark of many neoplasms in the nervous system. Recent reports indicate that the endothelial mitogen vascular endothelial growth factor (VEGF) may play a critical role in the regulation of vascular endothelial proliferation in malignant gliomas. Using novel monoclonal antibodies to the VEGF polypeptide we have determined the expression and cellular distribution of VEGF protein in a representative series of 171 human central nervous system (CNS) tumors by immunohistochemistry and immunoblotting. In agreement with previous in situ hybridization data, 19 out of 20 glioblastomas (95%) showed immunoreactivity for VEGF, whereas both the percentage of immunoreactive tumors and the extent of immunoreactivity for VEGF were significantly lower in astrocytomas. Of the pilocytic astrocytomas (WHO grade I) 44% were immunoreactive for VEGF, but we observed several cases with pronounced vascular proliferates in the absence of VEGF. In ependymomas, meningiomas, hemangioblastomas, and primitive neuroectodermal tumors, there was no correlation between VEGF expression, vascular endothelial proliferation and the grade of malignancy. Oligodendrogliomas and the oligodendroglial component of mixed gliomas lacked immunoreactive VEGF, indicating that endothelial growth factors other than VEGF may regulate tumor angiogenesis in these neoplasms. Western blot analysis showed a predominant VEGF protein species of 23 kDa and confirmed the immunohistochemical data in all cases. Our findings demonstrate that VEGF is expressed in a wide spectrum of brain tumors in which it may induce neovascularization. However, other angiogenic factors also appear to contribute to the vascularization of CNS neoplasms. Received: 18 April 1996 / Revised, accepted: 20 August 1996  相似文献   
55.
The pharmacokinetic behaviour of the 131-iodine-labelled title compound 3 * and its metabolites in mice was investigated. A two phase, 1st order elimination profile was observed. The second phase is very slow leaving about 35% of radioactivity in the mice even 100h after i.v. injection, because of high affinity to liver and spleen, caused by strong binding of oligoamines to phospholipids of liver and blood cell membranes. The blood-brain-barrier is not passed. No deep compartments were observed. The doses necessary for antithrombotic effects in vivo were calculated from the blood levels to be 20.5–39.7 μmol/kg for a time interval of 1–6 h after administration.  相似文献   
56.
Zolmitriptan (ZomigTM) is a 5HT1B/1D agonist which has the ability to cross the intact blood-brain barrier to access central as well as peripheral receptors. Because of the potential for central nervous system side effects, this randomized, double-blind, placebo-controlled, 6-period crossover study evaluated the effects of 2.5 and 5 mg doses of zolmitriptan on psychomotor performance and investigated any pharmacodynamic or pharmacokinetic interaction with diazepam. Twelve healthy volunteers received the following "treatments" as single doses: zolmitriptan 2.5 mg, zolmitriptan 5 mg, diazepam 10 mg, zolmitriptan 2.5 mg+diazepam 10 mg, zolmitriptan 5 mg+diazepam 10 mg and placebo. Pre-dose and at 1, 4, 8, and 24 h post-dose, the following validated battery of psychomotor tests was performed: Bond-Lader visual analogue scales (calmness, contentedness, and alertness factors), critical flicker fusion test, choice reaction time (recognition, motor, and total reaction times), finger-tapping test, number cancellation test and digit symbol substitution test. Plasma concentrations of zolmitriptan, its active metabolite, and diazepam and its active metabolites were measured at the same timepoints. Zolmitriptan 2.5 and 5 mg had no effect on psychomotor function when given alone. In contrast, diazepam 10 mg had profound effects, consistent with its sedative properties, but there was no synergism on concomitant administration of either dose of zolmitriptan. Plasma concentrations of zolmitriptan, diazepam, and their respective active metabolites were similar when the two drugs were given alone or in combination.  相似文献   
57.
The molecules involved in homotypic aggregation of the human Burkitt-lymphoma cell line Raji were investigated by inhibition of reaggregation with carbohydrates and glycoconjugates, by inhibition of glycosylation, and enzyme treatment of the cell surface. Complete inhibition of reaggregation was achieved with bovine submaxillary mucin. Asialomucin, on the other hand, was not effective in this assay. Another potent inhibitor of reaggregation was the ganglioside GMI. The common carbohydrate structure of these molecules is NeuNAc-(gal)-galNAc. Lactosamine, fucosyllactosamine, sialyllactosamine, complex mannose type, or Thomsen-Friedenreich antigen sequences are not involved in aggregation. Neuraminidase and chloroquine also abolished agglutination of cells. The finding that mucin, but not asialomucin, inhibits the reaction, demonstrates the importance of sialic acid in this process. Homotypic aggregation was shown to be resistant to trypsin. Using the glycosylation inhibitor tunicamycin we show that N-glycosidically linked carbohydrate chains are involved in aggregation. Swainsonine or castanospermine, which inhibit processing of terminal sialyllactosamines to the mannose core, did not interfere with the reaction supporting the results of the inhibition assay. The data presented suggest the involvement of 2 molecules in homotypic aggregation of human Burkitt-lymphoma cells. One component is a lectin-like molecule containing N-linked carbohydrate chains. The other component carries the neuraminidase-sensitive and trypsin-resistant determinant NeuNAc-(gal)-galNAc and, therefore, appears to be a glycolipid. This proposed lectin-carbohydrate interaction in homotypic aggregation is further supported by the frequently observed dependence of lectins on divalent cations as indicated by inhibition of aggregation with EDTA and EGTA.  相似文献   
58.
In this study a new dynamic method is introduced allowing the estimation of blood cell adhesion on flat test surfaces by measuring the cell loss in the bulk phase of surface contacting test blood under defined rheological conditions. This was achieved by constructing a novel test chamber permitting the contact of small amounts of blood with a large geometrical test surface. The construction consists of a spiral-shaped flow channel of 0.3 cm width, 0.02 cm height and 78 cm length covered with the biomaterials to be tested from both sides. Laminarity of blood flow in the conduit was confirmed theoretically by the calculation of an equivalent to the Reynolds number for curved systems the so-called Dean number. Furthermore, flow laminarity was proved experimentally finding that the flow rate of blood with different hematocrit values was proportional to the hydrostatic pressure applied. The applicability of the novel 'spiral method' for the estimation of hemocompatibility was demonstrated by evaluation of platelet adhesion onto different polymers in comparison to siliconized and fibrinogen coated glass as reference surfaces. Additionally, it was possible under distinct conditions to determine the adhesion of leucocytes and the detachment of platelet aggregates. Therefore, it was concluded that the spiral method can be used for the assessment of the hemocompatibility of flat biomedical polymers. As main advantages of the new method can be considered the high time efficiency and accuracy without labelling or optical detection of adherent cells.  相似文献   
59.
This study assessed types and sources of perceived mistreatment among graduating dental students. A total of 38 of 46 (83 percent) students anonymously completed a mistreatment questionnaire. All 38 students perceived experiencing at least one type of mistreatment from some source and reported an average of about 35 separate incidents. Psychological mistreatment was most frequent with physical mistreatment reported relatively infrequently. Classmates and clinical faculty were the most frequent sources of mistreatment. Sexual harassment was perceived by about one-third of the students. The potentially adverse effects of perceived mistreatment were discussed with a view to improving dental education through an emphasis on stress management, environmental change, and self-responsibility for health designed to enhance the personal growth of each dental student.  相似文献   
60.
PURPOSE: Some researchers (F. R. Vellutino, F. M. Scanlon, & M. S. Tanzman, 1994) have argued that the different domains comprising language (e.g., phonology, semantics, and grammar) may influence reading development in a differential manner and at different developmental periods. The purpose of this study was to examine proposed causal relationships among different linguistic subsystems and different measures of reading achievement in a group of children with reading disabilities. METHODS: Participants were 279 students in 2nd to 3rd grade who met research criteria for reading disability. Of those students, 108 were girls and 171 were boys. In terms of heritage, 135 were African and 144 were Caucasian. Measures assessing pre-reading skills, word identification, reading comprehension, and general oral language skills were administered. RESULTS: Structural equation modeling analyses indicated receptive and expressive vocabulary knowledge was independently related to pre-reading skills. Additionally, expressive vocabulary knowledge and listening comprehension skills were found to be independently related to word identification abilities. CONCLUSION: Results are consistent with previous research indicating that oral language skills are related to reading achievement (e.g., A. Olofsson & J. Niedersoe, 1999; H. S. Scarborough, 1990). Results from this study suggest that receptive and expressive vocabulary knowledge influence pre-reading skills in differential ways. Further, results suggest that expressive vocabulary knowledge and listening comprehension skills facilitate word identification skills.  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