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   29061篇
  免费   1924篇
  国内免费   85篇
耳鼻咽喉   249篇
儿科学   770篇
妇产科学   495篇
基础医学   4273篇
口腔科学   363篇
临床医学   2680篇
内科学   7080篇
皮肤病学   710篇
神经病学   2382篇
特种医学   905篇
外国民族医学   6篇
外科学   4229篇
综合类   274篇
一般理论   28篇
预防医学   2163篇
眼科学   587篇
药学   1767篇
  1篇
中国医学   56篇
肿瘤学   2052篇
  2022年   125篇
  2021年   390篇
  2020年   253篇
  2019年   414篇
  2018年   485篇
  2017年   320篇
  2016年   396篇
  2015年   464篇
  2014年   693篇
  2013年   1037篇
  2012年   1523篇
  2011年   1725篇
  2010年   1013篇
  2009年   1017篇
  2008年   1613篇
  2007年   1767篇
  2006年   1782篇
  2005年   1871篇
  2004年   1709篇
  2003年   1636篇
  2002年   1629篇
  2001年   510篇
  2000年   455篇
  1999年   505篇
  1998年   412篇
  1997年   380篇
  1996年   316篇
  1995年   305篇
  1994年   274篇
  1993年   255篇
  1992年   384篇
  1991年   370篇
  1990年   322篇
  1989年   319篇
  1988年   264篇
  1987年   260篇
  1986年   269篇
  1985年   254篇
  1984年   236篇
  1983年   226篇
  1982年   234篇
  1981年   250篇
  1980年   196篇
  1979年   168篇
  1978年   155篇
  1977年   156篇
  1976年   129篇
  1975年   125篇
  1974年   121篇
  1973年   117篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
41.
An ultra-short-time heating system was used to process blood plasma spiked with various viruses (HIV, vesicular stomatitis virus, encephalomyocarditis virus). Virus reduction and recovery of plasma proteins were measured at various temperatures from 65 to 85 degrees C. Processing at 77 degrees C and 0.006 s resulted in a high level of virus kill, including greater than or equal to 4.4 log10 HIV, while maintaining protein structure and activity essentially intact.  相似文献   
42.
P Icard  Y Chapuis  B Andreassian  A Bernard  C Proye 《Surgery》1992,112(6):972-9; discussion 979-80
BACKGROUND. Because of the rarity of adrenocortical carcinoma, survival rates and prognosis for patients who have undergone operation are not well known. The purpose of the French Association of Endocrine Surgery was to evaluate these factors in all patients treated during a 12-year period by its members. METHODS. One hundred fifty-six patients (95 women, 61 men) with a mean age of 47 years were included. Functional symptoms were found in 52% of patients, and hormonal studies revealed secreting tumors in 62% of cases. Ninety-four percent of the patients underwent resection of the adrenal tumor, and 20% of them had extensive resection because of invasive cancers. Complete resection was achieved in 127 patients (81%) and incomplete resection in 29 patients. Mean tumor weight was 714 gm (range, 12 to 4750 gm), and the mean diameter was 12 cm (range, 3 to 30 cm). The results of the tumor staging were stage I, eight patients (5%); stage II (local disease), 75 patients (48%); stage III (locoregional disease), 39 patients (25%); and stage IV (metastases), 34 patients (22%). RESULTS. The 5-year actuarial survival rates were 34% overall, 42% in curative group, 53% in local cancer group, 24% in regional disease group, and 27% in the reoperated group. One-year actuarial survival rate of the palliative group was 9% (median survival, 6 months). Multivariate analysis showed that better prognosis occurred in patients younger than 35 years of age (p = 0.01) and in patients with androgen-secreting tumors, precursor-secreting tumors, or nonsecreting tumors (p = 0.003). Mitotane improved the survival rate only in patients with metastases who received it after operation (vs non-mitotane-treated patients [p < 0.05]). CONCLUSIONS. In this study age, extent of disease, aspect of the surgical resection, and type of hormonal secretion influenced survival.  相似文献   
43.
The aim of laboratory screening in Phase I is to exclude subjects with subclinical illness, who might be at increased risk in the study, and who might also adversely influence interpretation of the results. A new method for laboratory screening, based on Bayesian probability theory, is proposed, which consists of: 1. Drawing up a list of diseases to be excluded. 2. Defining for each disease, the maximum acceptable risk that an included subject could be affected by it. 3. Identifying one test for each disease. 4. Using a contingency table to calculate the specificity of the test and integrating the estimated prevalence of the disease from epidemiological data. 5. Applying the percentage obtained by the calculation of specificity to the previously determined distribution of values in the volunteer population to identify the threshold value for inclusion. Use of this deductive method in screening volunteers for Phase I trials affords increased security of selection, while reducing the number of non-pertinent exclusions because of laboratory findings.  相似文献   
44.
Although acute thyroiditis often has a distinctive clinical presentation, this relatively uncommon entity can occasionally be confused with other inflammatory processes. In general, the earlier the diagnosis of acute thyroiditis is established, the lower is the frequency and severity of its attendant complications. Computed tomography (CT) is an extremely useful modality in establishing the diagnosis early because it can evaluate iodine content of the thyroid gland and provides more accurate mapping than ultrasound and nuclear medicine techniques. Three patients with acute thyroiditis--two with suppuration--are presented and the CT findings and clinical aspects of this disease are reviewed.  相似文献   
45.
46.
Background: Oncogenes and other molecular tumor markers that predict tumor aggressiveness may allow individualization and optimization of surgical therapy of intermediate-thickness malignant melanoma. We examined the expression of selected markers, including the HLA-DR antigen, the heat shock protein-70 (HSP-70), and the c-myc oncogene in primary melanoma and regional nodes and related these findings to metastatic potential and survival. Methods: Forty patients with primary melanoma (1.5–4.0 mm) were studied, all of whom had prophylactic lymph node dissection and were followed for 18 months to 7 years. The primary tissue and nodes were examined using immunohistochemical techniques for the presence of HLA-DR antigen and HSP-70 protein and the expression of the c-myc oncogene. Results: Of 40 patients, there were 23 with lesions 1 to 2.9 mm thick and 17 with lesions 3 to 4 mm thick. Nodal metastases were present in 25 of the 40 patients who had elective node dissection. HLA-DR antibody stained the primary tumor in 10 patients (25%), but there was no correlation with survival in this group. HLA-DR antibody stained the stroma and cellular infiltrates surrounding the primary tumor in 28 of 40 patients; in this group there was a correlation of HLA-DR staining of the peritumoral stroma with improved survival overall. HLA-DR staining of the peritumoral stroma also influenced survival when patients were stratified by tumor thickness groups 1 to 2.9 mm and 3 to 4 mm and presence of nodal metastases. HSP-70 was demonstrated in the primary tumor in 25% of patients, who were also shown to have significantly improved survival when compared with those whose primary tumor did not stain with HSP-70. C-myc was expressed in the primary tumor in 25%, but showed no correlation with survival. None of these proteins correlated with or predicted the presence of nodal metastases. Conclusion: We conclude that the use of specific molecular-oncogene markers in intermediate-thickness primary melanoma may identify patients at high risk for conventional treatment failure and reduced survival who may profit from more aggressive surgery, adjuvant therapy, or both.Presented at the 48th Annual Cancer Symposium of The Society of Surgical Oncology, Boston, Massachusetts, March 23–26, 1995.  相似文献   
47.
48.
The efficient and non-toxic nuclear delivery of steric-block oligonucleotides (ON) is a prerequisite for therapeutic strategies involving splice correction or exon skipping. Cationic cell penetrating peptides (CPPs) have given rise to much interest for the intracellular delivery of biomolecules, but their efficiency in promoting cytoplasmic or nuclear delivery of oligonucleotides has been hampered by endocytic sequestration and subsequent degradation of most internalized material in endocytic compartments. In the present study, we compared the splice correction activity of three different CPPs conjugated to PMO(705), a steric-block ON targeted against the mutated splicing site of human beta-globin pre-mRNA in the HeLa pLuc705 splice correction model. In contrast to Tat48-60 (Tat) and oligoarginine (R(9)F(2)) PMO(705) conjugates, the 6-aminohexanoic-spaced oligoarginine (R-Ahx-R)(4)-PMO(705) conjugate was able to promote an efficient splice correction in the absence of endosomolytic agents. Our mechanistic investigations about its uptake mechanisms lead to the conclusion that these three vectors are internalized using the same endocytic route involving proteoglycans, but that the (R-Ahx-R)(4)-PMO(705) conjugate has the unique ability to escape from lysosomial fate and to access to the nuclear compartment. This vector, which has displays an extremely low cytotoxicity, the ability to function without chloroquine adjunction and in the presence of serum proteins. It thus offers a promising lead for the development of vectors able to enhance the delivery of therapeutic steric-block ON in clinically relevant models.  相似文献   
49.
We showed that unloading markedly diminished the effects of IGF-I to activate its signaling pathways, and the disintegrin echistatin showed a similar block in osteoprogenitor cells. Furthermore, unloading decreased alphaVbeta3 integrin expression. These results show that skeletal unloading induces resistance to IGF-I by inhibiting activation of the IGF-I signaling pathways at least in part through downregulation of integrin signaling. INTRODUCTION: We have previously reported that skeletal unloading induces resistance to insulin-like growth factor-I (IGF-I) with respect to bone formation. However, the underlying mechanism remains unclear. The aim of this study was to clarify how skeletal unloading induces resistance to the effects of IGF-I administration in vivo and in vitro with respect to bone formation. MATERIALS AND METHODS: We first determined the response of bone to IGF-I administration in vivo during skeletal unloading. We then evaluated the response of osteoprogenitor cells isolated from unloaded bones to IGF-I treatment in vitro with respect to activation of the IGF-I signaling pathways. Finally we examined the potential role of integrins in mediating the responsiveness of osteoprogenitor cells to IGF-I. RESULTS: IGF-I administration in vivo significantly increased proliferation of osteoblasts. Unloading markedly decreased proliferation and blocked the ability of IGF-I to increase proliferation. On a cellular level, IGF-I treatment in vitro stimulated the activation of its receptor, Ras, ERK1/2 (p44/42 MAPK), and Akt in cultured osteoprogenitor cells from normally loaded bones, but these effects were markedly diminished in cells from unloaded bones. These results were not caused by altered phosphatase activity or changes in receptor binding to IGF-I. Inhibition of the Ras/MAPK pathway was more impacted by unloading than that of Akt. The disintegrin echistatin (an antagonist of the alphaVbeta3 integrin) blocked the ability of IGF-I to stimulate its receptor phosphorylation and osteoblast proliferation, similar to that seen in cells from unloaded bone. Furthermore, unloading significantly decreased the mRNA levels both of alphaV and beta3 integrin subunits in osteoprogenitor cells. CONCLUSION: These results indicate that skeletal unloading induces resistance to IGF-I by inhibiting the activation of IGF-I signaling pathways, at least in part, through downregulation of integrin signaling, resulting in decreased proliferation of osteoblasts and their precursors.  相似文献   
50.
OBJECTIVE: To describe investigation of a tightly clustered outbreak of invasive group A streptococcal (GAS) disease associated with a high mortality rate in a long-term care facility (LTCF). DESIGN: Cross-sectional carriage survey and epidemiologic investigation of LTCF resident and employee cohorts. SETTING: A 104-bed community LTCF between March 1 and April 7, 2004. PATIENTS: A cohort of LTCF residents with assigned beds at the time of the outbreak. INTERVENTIONS: Reinforcement of standard infection control measures and receipt of chemoprophylaxis by GAS carriers. RESULTS: Four confirmed and 2 probable GAS cases occurred between March 16 and April 1, 2004. Four case patients died. The final case occurred during the investigation, before the patient was determined to be a GAS carrier. No case occurred during the 6 months after the intervention. Disease was caused by type emm3 GAS; 16.5% of residents and 2.4% of employees carried the outbreak strain. Disease was clustered in 1 quadrant of the LTCF and associated with nonintact skin. GAS disease or carriage was associated with having frequent personal visitors. CONCLUSIONS: Widespread carriage of a virulent GAS strain likely resulted from inadequate infection control measures. Enhanced infection control and targeted prophylaxis for GAS carriers appeared to end the outbreak. In addition to employees, regular visitors to LTCFs should be trained in hand hygiene and infection control because of the potential for extended relationships over time, leading to interaction with multiple residents, and disease transmission in such residential settings. Specific attention to prevention of skin breaks and proper wound care may prevent disease. The occurrence of a sixth case during the investigation suggests urgency in addressing severe, large, or tightly clustered outbreaks of GAS infection in LTCFs.  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