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   37891篇
  免费   3862篇
  国内免费   1487篇
耳鼻咽喉   426篇
儿科学   590篇
妇产科学   579篇
基础医学   4016篇
口腔科学   542篇
临床医学   3188篇
内科学   4499篇
皮肤病学   803篇
神经病学   1462篇
特种医学   2822篇
外国民族医学   19篇
外科学   2625篇
综合类   6567篇
现状与发展   4篇
预防医学   3049篇
眼科学   1069篇
药学   3463篇
  12篇
中国医学   2008篇
肿瘤学   5497篇
  2024年   100篇
  2023年   532篇
  2022年   836篇
  2021年   1379篇
  2020年   1269篇
  2019年   1238篇
  2018年   1255篇
  2017年   1300篇
  2016年   1489篇
  2015年   1543篇
  2014年   2526篇
  2013年   2964篇
  2012年   2420篇
  2011年   2622篇
  2010年   2019篇
  2009年   1880篇
  2008年   1893篇
  2007年   1940篇
  2006年   1808篇
  2005年   1589篇
  2004年   1363篇
  2003年   1279篇
  2002年   984篇
  2001年   884篇
  2000年   807篇
  1999年   611篇
  1998年   480篇
  1997年   447篇
  1996年   407篇
  1995年   316篇
  1994年   310篇
  1993年   210篇
  1992年   199篇
  1991年   175篇
  1990年   163篇
  1989年   174篇
  1988年   137篇
  1987年   130篇
  1986年   109篇
  1985年   161篇
  1984年   171篇
  1983年   114篇
  1982年   114篇
  1981年   87篇
  1980年   108篇
  1979年   82篇
  1978年   59篇
  1977年   51篇
  1976年   58篇
  1975年   34篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
991.
Strabismus is a pathology that affects approximately 4 % of the population, causing aesthetic problems reversible at any age and irreversible sensory alterations that modify the vision mechanism. The Hirschberg test is one type of examination for detecting this pathology. Computer-aided detection/diagnosis is being used with relative success to aid health professionals. Nevertheless, the routine use of high-tech devices for aiding ophthalmological diagnosis and therapy is not a reality within the subspecialty of strabismus. Thus, this work presents a methodology to aid in diagnosis of syndromic strabismus through digital imaging. Two hundred images belonging to 40 patients previously diagnosed by an specialist were tested. The method was demonstrated to be 88 % accurate in esotropias identification (ET), 100 % for exotropias (XT), 80.33 % for hypertropias (HT), and 83.33 % for hypotropias (HoT). The overall average error was 5.6Δ and 3.83Δ for horizontal and vertical deviations, respectively, against the measures presented by the specialist.  相似文献   
992.
目的乳腺癌的早期发现对患者意义重大。为帮助医生进行乳腺癌的早期检查和诊断,本文提出利用小波分析与图像纹理特征提取相结合的方法来提取乳腺X线图像微钙化点区域,在提高检查准确性的同时避免漏检误检。方法首先利用灰度共生矩阵所提取的能量、熵、对比度、相关性以及小波分解后得到的各层高频系数的方差、能量作为图像的特征向量,然后利用支持向量机进行训练建立最优分类模型。最后利用建立的最优分类模型实现乳腺X线图像微钙化点区域的提取并利用检出率和误检率对结果进行评估。结果使用临床数据进行验证,结果表明利用小波分析与图像纹理特征提取相结合的方法能有效提取乳腺图像中的微钙化点区域。结论基于小波分析和灰度纹理特征的乳腺X线图像微钙化点区域的提取方法比单一的图像纹理特征提取或小波分析等方法,提取的效果更好。另外,该方法设计简单,更易于实现乳腺癌的自动化诊断。  相似文献   
993.
目的 应用有限元法研究仰卧位屈膝屈髋按压法对骨盆应力及骶髂关节应变分布特点的影响,讨论该手法扳动整个骶髂关节的可能性。方法 利用CT图像建立正常骨盆三维有限元模型。根据手法原理,将屈膝屈髋按压法分解为两个方向的力,将这两个力加载于三维有限元模型并进行计算分析,得到该加载下骨盆应力和骶髂关节应变的分布情况。结果 加载模拟手法后,骨盆的主要应力位于骶髂关节前下1/3处、坐骨大切迹及臀下线和臀前线的中1/3;骶髂关节的最大应变主要位于骶髂关节的后上缘、后下缘及上缘中部1/2。结论 屈膝屈髋按压法只能扳动骶髂关节的下1/3处,而不能扳动整个骶髂关节。  相似文献   
994.
The potential use of urinary nucleic acids as diagnostic markers in prostate cancer (PCa) was evaluated. Ninety-five urine samples and 234 prostate tissue samples from patients with PCa and benign prostatic hyperplasia (BPH) were analyzed. Micro-array analysis was used to identify candidate genes, which were verified by the two-gene expression ratio and validated in tissue mRNA and urinary nucleic acid cohorts. Real-time quantitative polymerase chain reaction (qPCR) was used to measure urinary nucleic acid levels and tissue mRNA expression. The TSPAN13-to-S100A9 ratio was selected to determine the diagnostic value of urinary nucleic acids in PCa (P = 0.037) and shown to be significantly higher in PCa than in BPH in the mRNA and nucleic acid cohort analyses (P < 0.001 and P = 0.013, respectively). Receiver operating characteristic (ROC) analysis showed that the area under the ROC curve was 0.898 and 0.676 in tissue mRNA cohort and urinary nucleic acid cohort, respectively. The TSPAN13-to-S100A9 ratio showed a strong potential as a diagnostic marker for PCa. The present results suggest that the analysis of urine supernatant can be used as a simple diagnostic method for PCa that can be adapted to the clinical setting in the future.  相似文献   
995.
996.
脂多糖和甲双吡丙酮诱发形成豚鼠运动性哮喘模型   总被引:2,自引:0,他引:2  
目的建立一种接近临床特点的运动性哮喘动物模型。方法豚鼠27只分4组。实验组(A组)用脂多糖(1mg/kg)和甲双吡丙酮(50mg/kg)腹腔注射,4天后测定气道阻力和动态肺顺应性基础值,8小时后进行运动试验并复测上述指标。对照组有3组(B、C、D组);分别为腹腔注射脂多糖和甲双吡丙酮不运动组、腹腔注射生理盐水运动组和腹腔注射生理盐水不运动组。结果实验组豚鼠在运动后肺阻力增高、动态肺顺应性降低,而3个对照组上述指标变化均无统计学意义。结论脂多糖和甲双吡丙酮腹腔注射可诱发形成豚鼠运动性哮喘模型  相似文献   
997.
PURPOSE: We retrospectively analyzed prognostic factors for surgical resection and intraoperative radiation therapy to identify indicators for this treatment strategy. METHODS: Thirty-nine consecutive patients with locally recurrent colorectal cancer who underwent surgical resection with intraoperative radiation therapy from January 1, 1987, to June 30, 1999, were analyzed. The mean electron energy was 10.5 MeV and the mean intraoperative radiation dose was 22.6 Gy. Kaplan-Meier survival estimates were obtained for the 37 patients who recovered postoperatively. Prognostic factors were analyzed univariately by log-rank test and multivariately by Coxs proportional hazards model. RESULTS: Three-year cumulative survival was 44 percent (standard error = 11) for 26 patients free of unresectable distant metastasis who underwent surgical resection and intraoperative radiation therapy for pelvic recurrence of colorectal cancer, but none of the 11 patients with unresectable distant metastasis survived 3 years. Preoperative prognostic factors which were significant on univariate and multivariate analysis were unresectable distant metastasis (P = 0.001) and elevated preoperative serum CA 19–9 (P = 0.02). Patients with synchronous resection of local recurrence and distant metastasis had a significant survival advantage over those without resection of metastases (P = 0.02). Univariate analysis in a subgroup of 26 patients without unresectable distant metastasis revealed pain (P = 0.0003) to be a useful preoperative prognostic indicator, whereas tumor fixation (P = 0.01) and amount of residual tumor after surgical resection (P = 0.01) were significant intraoperative and postoperative factors, respectively. Fluorouracil-based postoperative systemic chemotherapy produced a significant survival benefit (P = 0.04). CONCLUSIONS: Patients with unresectable distant metastasis are not suitable candidates for surgical resection and intraoperative radiation therapy, whereas those with resectable metastasis are potential candidates. Intraoperative radiation therapy may be less useful for patients with pain, elevated preoperative CA19–9, fixed tumors, or gross residual tumor after surgical resection. Multimodal treatment strategies combining preoperative and/or postoperative external beam radiation therapy and intraoperative radiation therapy with fluorouracil-based systemic chemotherapy are recommended for patients with these indicators.  相似文献   
998.
999.
1000.
Objective: To determine the frequency and clinical significance of sterile and microbial-associated intra-amniotic inflammation in asymptomatic patients with a sonographic short cervix.

Methods: Amniotic fluid (AF) samples obtained by transabdominal amniocentesis from 231 asymptomatic women with a sonographic short cervix [cervical length (CL) ≤25?mm] were analyzed using cultivation techniques (for aerobic and anaerobic as well as genital mycoplasmas) and broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). The frequency and magnitude of intra-amniotic inflammation [defined as an AF interleukin (IL)-6 concentration ≥2.6?ng/mL], acute histologic placental inflammation, spontaneous preterm delivery (sPTD), and the amniocentesis-to-delivery interval were examined according to the results of AF cultures, PCR/ESI-MS and AF IL-6 concentrations.

Results: Ten percent (24/231) of patients with a sonographic short cervix had sterile intra-amniotic inflammation (an elevated AF IL-6 concentration without evidence of microorganisms using cultivation and molecular methods). Sterile intra-amniotic inflammation was significantly more frequent than microbial-associated intra-amniotic inflammation [10.4% (24/231) versus 2.2% (5/231); p?p?p?Conclusion: Sterile intra-amniotic inflammation is more common than microbial-associated intra-amniotic inflammation in asymptomatic women with a sonographic short cervix, and is associated with increased risk of sPTD (<34 weeks). Further investigation is required to determine the causes of sterile intra-amniotic inflammation and the mechanisms whereby this condition is associated with a short cervix and sPTD.  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