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   82204篇
  免费   7083篇
  国内免费   3504篇
耳鼻咽喉   655篇
儿科学   1539篇
妇产科学   1500篇
基础医学   10348篇
口腔科学   1479篇
临床医学   9217篇
内科学   14057篇
皮肤病学   1193篇
神经病学   5141篇
特种医学   3037篇
外国民族医学   34篇
外科学   9258篇
综合类   9182篇
现状与发展   15篇
一般理论   43篇
预防医学   6198篇
眼科学   1846篇
药学   7750篇
  52篇
中国医学   3116篇
肿瘤学   7131篇
  2024年   201篇
  2023年   1029篇
  2022年   2421篇
  2021年   3491篇
  2020年   2486篇
  2019年   2494篇
  2018年   2713篇
  2017年   2332篇
  2016年   2398篇
  2015年   3181篇
  2014年   3989篇
  2013年   4348篇
  2012年   6117篇
  2011年   6385篇
  2010年   4011篇
  2009年   3353篇
  2008年   4828篇
  2007年   4827篇
  2006年   4457篇
  2005年   4191篇
  2004年   3476篇
  2003年   3316篇
  2002年   2963篇
  2001年   1797篇
  2000年   1678篇
  1999年   1558篇
  1998年   956篇
  1997年   932篇
  1996年   752篇
  1995年   653篇
  1994年   566篇
  1993年   413篇
  1992年   560篇
  1991年   479篇
  1990年   438篇
  1989年   391篇
  1988年   300篇
  1987年   303篇
  1986年   250篇
  1985年   214篇
  1984年   171篇
  1983年   130篇
  1982年   130篇
  1981年   126篇
  1980年   84篇
  1979年   109篇
  1978年   71篇
  1976年   58篇
  1974年   69篇
  1973年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
PURPOSE: Both the retinoblastoma and p53 pathways are often genetically altered in human cancers and their complex regulation is in part mediated by the three gene products p16, p14(ARF), and p15 of the INK4 locus on chromosome 9p21. Partial or complete biallelic deletions of the INK4 locus have been recognized in a variety of malignant tumors, including malignant melanoma. We have in the present study measured the frequency of INK4 deletions in a large number of melanoma metastases and determined their association with clinicopathologic variables and survival data. EXPERIMENTAL DESIGN: Quantitative real-time PCR, as well as fluorescence-based fragment analysis, has been used to perform measurements of the relative allelic concentrations of the INK4 genes in 112 human melanoma tumor samples from 86 patients. RESULTS: Thirty-eight of 86 melanoma patients (44%) had metastases with biallelic losses in INK4. Ten of 20 patients with multiple metastases showed similar deletion patterns in all analyzed tumors. There was no significant association between any of the clinicopathologic variables and loss of INK4. However, loss of INK4 had an adverse effect on median survival from time of diagnosis. Patients with tumors with diploid INK4 had a median survival of 142 months, whereas those with monoallelic or biallelic loss in INK4 had a median survival of only 47 months (P = 0.006). CONCLUSIONS: Our results point to homozygous deletions in the INK4 region as being one of the most common genetic alterations in malignant cutaneous melanoma. INK4 deletions are associated with an adverse prognosis.  相似文献   
992.
PURPOSE: To investigate the feasibility of combining concomitant boost accelerated radiation regimen (AFX-C) with cisplatin and to assess its toxicity and the relapse pattern and survival in patients with advanced head and neck carcinoma (HNC). PATIENTS AND METHODS: Between April and November of 2000, 84 patients with stage III to IV HNC who met the eligibility criteria were enrolled; 76 of these patients were analyzable. Radiation consisted of 72 Gy in 42 fractions over 6 weeks (daily for 3.5 weeks, then twice a day for 2.5 weeks). Cisplatin dose was 100 mg/m(2) on days 1 and 22. Tumor and clinical status were assessed, and acute late toxicities were graded. RESULTS: Sixty-five patients (86%) received both radiation and chemotherapy per protocol or with minor variations. The estimated 2-year locoregional relapse and distant metastasis rates were 34.7% and 16.1%, respectively. The estimated 2-year overall survival and disease-free survival rates were 71.6% and 53.5%, respectively. Three patients (4%) died of complications, 19 patients (25%) had acute grade 4 toxicity, and 49 patients (64%) had acute grade 3 toxicity. The 2-year cumulative incidence of late grade 3 to 5 toxicities was 51.3%. CONCLUSION: These data showed that it was feasible to combine AFX-C with cisplatin. The compliance to therapy was high, and the locoregional control and survival rates achieved compared favorably with AFX-C alone or other concurrent chemoradiation regimens tested by the Radiation Therapy Oncology Group. A phase III trial comparing AFX-C plus cisplatin against standard radiation plus cisplatin is ongoing to determine whether the use of AFX-C in the concurrent chemoradiation setting further improves outcome.  相似文献   
993.
Theoretically, a haplotype has a higher level of heterozygosity than individual single nucleotide polymorphism (SNP) and the association study based on the haplotype may have an increased power for detecting disease associations compared with SNP-based analysis. In this study, we investigated the effects of four haplotype-tagging SNPs (htSNP) and the inferred haplotype pairs of the X-ray cross-complementing group 1 (XRCC1) gene on chromosome damage detected by the cytokinesis-block micronucleus assay. The study included 141 coke-oven workers with exposure to a high level of polycyclic aromatic hydrocarbons and 66 nonexposed controls. The frequencies of total MN and MNed cells were borderline associated with the Arg(194)Trp polymorphism (P = 0.053 and P = 0.050, respectively) but not associated with the Arg(280)His, Arg(399)Gln and Gln(632)Gln polymorphisms among coke-oven workers. Five haplotypes, including CGGG, TGGG, CAGG, CGAG, and CGGA, were inferred based on the four htSNPs of XRCC1 gene. The haplotype CGGG was associated with the decreased frequencies of total MN and MNed cells, and the haplotypes TGGG and CGAG were associated with the increased frequencies of total MN and MNed cells with adjustment for covariates among coke-oven workers. This study showed that the haplotypes derived from htSNPs in the XRCC1 gene were more likely than single SNPs to correlate with the polycyclic aromatic hydrocarbon-induced chromosome damage among coke-oven workers.  相似文献   
994.
INTRODUCTION: Presence of circulating DNA in the serum of patients with cancer makes detection of tumour-specific genetic alterations feasible. OBJECTIVE: To study serum DNA concentration in patients diagnosed as having advanced Non-Small Cell Lung Cancer (NSCLC) and to evaluate its relationship with age, histology, stage, response, time-to-progression (TTP), and survival. METHODS: Serum DNA from 78 patients was purified and spectrophotometrically quantified. RESULTS: No significant correlations were found between serum DNA concentration and age, histology, response and survival. There was a significant correlation with respect to stage (IIIB = 408.75 ng/ml; IV = 478.74 ng/ml; p = 0.02). When patients were grouped according to DNA concentration, significant correlation with TTP was found; establishing a cut-off point at 500 ng/ml ([DNA] < 500 ng/ml TTP = 7.25 months, 95%CI: 3.5-5.25; [DNA ] > or = 500 ng/ml TTP = 4.25 months, 95%CI: 2-6.5; p = 0.05). CONCLUSIONS: Using the present method, DNA concentration quantification appears to be simple, but with certain deficiencies due to inter-sample variability and low specificity. This is because total DNA concentration is measured without distinguishing as to whether it is tumour-related. We suggest that there is a correlation between DNA concentration and prognosis which enables an analysis of the natural history of the disease.  相似文献   
995.
This study provides a closed form, analytical expression for the thermal dose delivered by a single heating pulse. The solution is derived using the effective cooling method and the non-linear Sapareto-Dewey equation to determine the thermal dose delivered by the time-temperature history of a treatment. The analytical solutions are used to determine the optimal treatment conditions, i.e. those that exactly deliver the desired thermal dose at a specified time. For purposes of illustration, this study focuses on a 'conservative' clinical approach in which the desired thermal dose is delivered at the end of the 'cool down' period. The analytical results show that, after a clinical strategy has been chosen (e.g. conservative, aggressive or intermediate), the user can only specify two free variables for such an optimal treatment. Results are presented which suggest that a practical approach would be to specify both (1) the desired thermal dose to be delivered to the target (the clinically relevant outcome) and (2) the peak temperature to be reached (a measurable, clinically useful, patient dependent response variable that can be employed in feedback control systems); and then determine the associated, optimal heating magnitude and duration that need to be used to reach that dose and temperature. The results also reveal that, with a given patient condition and power deposition distribution (together specifying an effective cooling time constant for the treatment) and a specified thermal dose, there is a maximum allowable peak temperature that, if exceeded, will result in 'over-dosing' the heated tissue. The results also show that avoiding such non-optimal 'over-dosing' will be difficult in most high temperature therapies since, when high temperatures are produced in tissues, the temperature decay must be very fast in order to avoid over-dosing during the cooling period. Such rapid cooling can only occur if short effective cooling time constants are present-either as a result of large tissue blood flows in the patient or due to large conduction effects induced by the use of highly localized power deposition sources.  相似文献   
996.
目的构建婴儿双歧杆菌/胞嘧啶脱氨酶靶向性基因治疗系统。方法 PCR 扩增 CD 基因,EcoR Ⅰ,BamH Ⅰ对 CD 基因和 pGEX-1LamdaT 质粒同时进行双酶切,获得4.9 kb、1.3 kh 两个 DNA 片段。T4 DNA 连接酶连接这两个片段构建重组的CD/pGEX-1LamdaT 质粒,然后用电穿孔法将重组质粒转染婴儿双歧杆菌。从阳性转染的婴儿双歧杆菌中提取重组质粒,双酶切后检测切取片段长度,采用 Sanger 双脱氧链终止法对提取的重组质粒中的插入片段进行测序。结果从阳性转染的婴儿双歧杆菌中获得了6.2 kb大小的重组质粒,该质粒经双酶切后,得到了4.9 kb 和1.3 kb 两个长度的片段,其长度分别与 pGEX-1LambdaT 及 CD 基因的长度相同。测序结果显示,提取的重组质粒中插入的基因片段全长及核苷酸序列与 CD 基因完全相同。结论外源性 CD 基因被准确插入 pGEX-1LambdaT 质粒并转入婴儿双歧杆菌中,婴儿双歧杆菌/胞嘧啶脱氨酶靶向性基因治疗系统被成功构建。  相似文献   
997.
AIMS: To report a clinicopathological series of cases of solitary fibrous tumor of the pleura from Taiwan. METHODS: Clinical data was collected from a review of medical records and telephone interviewing for follow-up. RESULTS: Eight patients, three men and five women aging from 34 to 71 years, underwent tumor resection and were followed in a period from 7 months to 13.5 years. Six patients underwent standard thoracotomy and two had VATS for tumor excision. Tumors were pathologically benign in seven patients and malignant in one. Patients were all alive with no evidence of tumor recurrence at the time of this report. CONCLUSIONS: One should always consider SFTPs as potentially malignant tumors. Complete resection remains the mainstay of cure. Standard thoracotomy should always be considered when a high suspicion of malignancy is raised, whereas VATS may be a preferred approach for smaller tumors.  相似文献   
998.
PURPOSE: Rituximab is an important therapeutic for Waldenstrom's macroglobulinemia (WM). Polymorphisms in FcgammaRIIIA (CD16) receptor expression modulate human immunoglobulin G1 binding and antibody-dependent cell-mediated cytotoxicity, and may therefore influence responses to rituximab. PATIENTS AND METHODS: Sequence analysis of the entire coding region of FcgammaRIIIA was undertaken in 58 patients with WM whose outcomes after rituximab were known. RESULTS: Variations in five codons of FcgammaRIIIA were identified. Two were commonly observed (FcgammaRIIIA-48 and FcgammaRIIIA-158) and predicted for amino acid polymorphisms at FcgammaRIIIA-48: leucine/leucine (L/L), leucine/arginine (L/R), and leucine/histidine (L/H). Polymorphisms at FcgammaRIIIA-158 were phenylalanine/phenylalanine (F/F), phenylalanine/valine (F/V), and valine/valine (V/V). A clear linkage between these polymorphisms was detected and all patients with FcgammaRIIIA-158F/F were always FcgammaRIIIA-48L/L, and patients with either FcgammaRIIIA-L/R or -L/H always expressed at least one valine at FcgammaRIIIA-158 (P < or = .001). The response trend was higher for patients with FcgammaRIIIA-48L/H (38.5%) versus -48L/R (25.0%) and LL (22.0%), and was significantly higher for patients with FcgammaRIIIA-158V/V (40.0%) and -V/F (35%) versus -158F/F (9.0%; P = .030). Responses for patients with FcgammaRIIIA-48L/L were higher when at least one valine was present at FcgammaRIIIA-158 (P = .057), thereby supporting a primary role for FcgammaRIIIA-158 polymorphisms in predicting rituximab responses. With a median follow-up of 13 months, no significant differences in the median time to progression and progression-free survival were observed when patients were grouped according to their FcgammaRIIIA-48 and -158 polymorphisms. CONCLUSION: The results of these studies therefore support a predictive role for FcgammaRIIIA-158 polymorphisms and responses to rituximab in WM.  相似文献   
999.
陈益昀主任中医师是全国第二、三批中医药专家学术经验继承指导老师,临床悬壶五十余载,治学严谨,注重实际。几十年的临床实践加之深厚扎实的理论功底,尤其能够结合现代医学知识,使其在治疗疾病,立法用药上独树一帜。笔者有幸随师学习,获益匪浅,兹将陈老师运用中西医结合治疗输卵管阻塞性不孕症的经验总结介绍如下:  相似文献   
1000.
Prospective cohort studies on breast cancer risk among premenopausal women and insulin-like growth factor I (IGF-I) concentrations have so far included only few cases, and have shown inconsistent relative risk estimates. We pooled 220 cases of breast cancer diagnosed before age 50, and 434 control subjects, from three prospective studies in New York (USA), Ume? (Northern Sweden) and Milan (Italy), and we measured IGF-I and insulin-like growth factor binding protein 3 (IGFBP-3) with common enzyme-linked immunosorbent assays. Overall, IGF-I and IGFBP-3 measurements obtained by the common method showed a positive but not significant relationship with breast cancer risk (odds ratios (ORs) 0.90 [95% confidence intervals (95% CI) 0.50-1.62], 1.63 [0.89-2.97], 1.46 [0.78-2.73] and 1.41 [0.75-2.63] for quintiles of IGF-I, and ORs 0.98 [0.54-1.75], 1.06 [0.59-1.91], 1.04 [0.58-1.87] and 1.77 [0.97-3.24] for quintiles of IGFBP-3). Our results give only moderate support for an association of blood IGF-I with breast cancer risk in young women.  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