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   3741篇
  免费   172篇
  国内免费   20篇
耳鼻咽喉   14篇
儿科学   60篇
妇产科学   28篇
基础医学   444篇
口腔科学   77篇
临床医学   234篇
内科学   1027篇
皮肤病学   195篇
神经病学   176篇
特种医学   338篇
外科学   573篇
综合类   14篇
预防医学   92篇
眼科学   14篇
药学   144篇
中国医学   6篇
肿瘤学   497篇
  2023年   28篇
  2022年   34篇
  2021年   76篇
  2020年   53篇
  2019年   66篇
  2018年   63篇
  2017年   71篇
  2016年   97篇
  2015年   85篇
  2014年   127篇
  2013年   142篇
  2012年   222篇
  2011年   261篇
  2010年   132篇
  2009年   106篇
  2008年   201篇
  2007年   262篇
  2006年   229篇
  2005年   228篇
  2004年   232篇
  2003年   240篇
  2002年   200篇
  2001年   74篇
  2000年   54篇
  1999年   49篇
  1998年   37篇
  1997年   44篇
  1996年   43篇
  1995年   31篇
  1994年   25篇
  1993年   23篇
  1992年   42篇
  1991年   27篇
  1990年   29篇
  1989年   32篇
  1988年   30篇
  1987年   24篇
  1986年   31篇
  1985年   25篇
  1984年   24篇
  1983年   21篇
  1982年   15篇
  1981年   11篇
  1980年   8篇
  1979年   10篇
  1978年   13篇
  1977年   8篇
  1970年   5篇
  1969年   6篇
  1968年   5篇
排序方式: 共有3933条查询结果,搜索用时 15 毫秒
991.
BACKGROUND:Invasive pancreatic carcinoma generally appears as poorly defined mass reflecting the infiltrative growth.We aimed to identify the histological and immunohistochemical features in a rare case of pancreatic carcinoma showing exophytic growth. METHODS:A 67-year-old woman presented with a mass of 5.0 cm in diameter in the pancreatic head.Preoperative computed tomography revealed a well-demarcated, primarily solid mass with a central low-density area. Magnetic resonance cholangiopancreatography revea...  相似文献   
992.
Soluble amyloid beta-protein (Abeta) does not aggregate to beta-amyloid fibrils (fAbeta) in the brain of normal humans. We recently found that the cerebrospinal fluid (CSF) from non-Alzheimer's disease (AD) subjects inhibited the formation of fAbeta(1-40) and fAbeta(1-42) more strongly than that from AD subjects, although the CSF obtained from both groups inhibited the fAbetas formation in vitro. Here, we examined the influence of plasma obtained from AD, non-AD and healthy control (CTL) subjects on the formation of fAbeta(1-40) and fAbeta(1-42) in vitro. Although the plasma obtained from all groups inhibited the formation of fAbeta(1-40) and fAbeta(1-42), the plasma from non-AD and CTL subjects inhibited the formation of fAbetas more strongly than that from AD subjects. These results indicate that the plasma as well as CSF in AD would provide a molecular environment favorable for fAbeta formation, suggesting a decrease of specific inhibitory factors and/or increase of specific accelerating factors.  相似文献   
993.
Bacterial tracheobronchitis is a rare cause of airway stenosis in adults. This report describes a 73-year-old woman with a recent history of polysialadenitis, who presented with severe airway obstruction due to infection and stenosis of tracheal and bronchial tissue. Tissue culture of the bronchial mucosa showed growth of methicillin resistant Staphylococcus epidermidis (MRSE). Sputum culture showed growth of MRSE, Pseudomonas aeruginosa, Enterobacter cloacae and Enterococcus faecalis ; the same organisms were cultured from the salivary glands. Tracheostomy and antibiotic therapy were effective in controlling the disease.  相似文献   
994.
The presence of white matter lesions (WML) is an important prognostic factor for the development of stroke. Plasma total homocysteine (tHcy), which increases with diabetes, has been flagged as a novel predictor for cerebrovascular events. We tested the hypothesis that the presence of WML correlates with tHcy in rheumatoid arthritis patients. Based on brain magnetic resonance imaging findings, 65 rheumatoid arthritis patients were divided into 2 groups: WML-positive group (61 ± 6 years, mean ± SD; n = 25) and WML-negative group (60 ± 7 years, n = 40). The level of metabolic parameters was assessed by total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, fasting plasma glucose, and homocysteine (tHcy). The duration of rheumatoid arthritis was longer in the WML-positive group than in the WML-negative group (P < .05). Plasma levels of triglyceride was higher whereas high-density lipoprotein cholesterol was lower in the WML-positive group than in the WML-negative group (P < .05 and P < .01, respectively). Fasting plasma glucose (P < .05) and tHcy (<.0001) levels were higher in the WML-positive group than in the WML-negative group. Multivariate logistic analysis revealed that WML was independently predicted by the tHcy (odds ratio, 1.35; 95% confidence interval, 1.12-1.63; P < .0001). Our findings indicate that the presence of WML was associated with the tHcy in Japanese patients with rheumatoid arthritis.  相似文献   
995.
996.
The aim of this study was to morphometrically analyze the tissue response to a customized pin obtained from devitalized bovine cortical bone (DBCB-pin) implanted in the subcutaneous tissue of rats, as well as to assess its microstructural aspect by scanning electron microscopy (SEM). The pins were implanted in the subcutaneous tissue of 20 rats, which were killed at 7, 14, 28 and 60 days (5 rats/period) after implantation. In the subcutaneous tissue, DBCB-pin promoted the formation of a fibrous capsule. At 7 days, capsule showed thickness of 70 ± 3.2 μm with higher density of newly formed capillaries and smaller density of collagen fibers. Between 14 and 60 days, more organized fibrous capsule exhibited smaller thickness (53 ± 5.5 μm) with higher density of fibroblasts and collagen fibers. In this period, a small and slow bioresorption of the DBCB-pin by macrophages and rare multinucleated giant cells without tissue damage was observed. The thickness of DBCB-pin resorbed was in mean only of 9.3 μm. During all experimental periods not occurred presence of immune reaction cells as lymphocytes and plasma cells. It was concluded that the pin derived from cortical bovine bone was well tolerated by subcutaneous tissue of rats and slowly resorbed could be an alternative material for membrane fixation in the guided tissue regeneration procedures.  相似文献   
997.
O(6)-Methylguanine and O(6)-chloroethylguanine, which are the primary cytotoxic DNA lesions produced by 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide (dacarbazine) and 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU), respectively, can be repaired by O(6)-methylguanine-DNA methyltransferase (MGMT), coded by the MGMT gene. However, the two types of drugs exhibit different effects on cells defective in both MGMT and MLH1 functions, the latter being related to the cellular activity to recognize mismatched bases of DNA for inducing apoptosis. Human cells deficient in both MGMT and MLH1 are resistant to the killing effect of dacarbazine and exhibit an increased mutant frequency after treatment with dacarbazine. On the other hand, these doubly deficient cells are sensitive to the killing action of ACNU and there is no significant increase in ACNU-induced mutant frequency. A mismatch recognition complex, composed of MSH2, MSH6, MLH1, PMS2 and PCNA, is formed after exposing MGMT-deficient cells to dacarbazine, but not in cells treated with ACNU. In contrast, the phosphorylation of Chk1 efficiently occurs in cells treated with dacarbazine as well as with ACNU, the former being in MLH1-dependent manner, whereas the latter in MLH1-independent manner. Therefore, the signals delivered from different sources would merge at the step of Chk1 activation or at an earlier step, and the subsequent process leading to apoptosis appears to be common.  相似文献   
998.
The objective of this study was to evaluate the coexpression patterns of hormonal markers in breast cancer tissue and their relationship with pathologic characteristics and epidemiologic risk factors. We evaluated the expression of 17 markers by immunohistochemistry in 842 invasive breast carcinomas collected in a population-based case-control study conducted in Poland. Based on marker correlations, factor analysis identified four major coexpression patterns (factors): "nuclear receptor factor" [estrogen receptor (ER)-alpha, progesterone receptor, androgen receptor, cyclin D1, and aromatase], "estrogen metabolism/ER-beta factor" (ER-beta, peroxisome proliferator-activated receptor-gamma, steroid sulfatase, estrogen sulfonotransferase, and cytochrome P450 1B1), "HER2 factor" (human epidermal growth factor receptor 2, E-cadherin, cyclooxygenase-2, aromatase, steroid sulfatase), and "proliferation factor" (cytokeratin 5, cytokeratin 5/6, epidermal growth factor receptor, P53). Three of these factors corresponded to molecular subtypes previously defined by expression profiling; however, the estrogen metabolism/ER-beta factor seemed to be distinctive. High scores for this factor were associated with high tumor grade (P heterogeneity = 0.02), younger age at menarche (P heterogeneity = 0.04), lower current body mass index among premenopausal women (P heterogeneity = 0.01), and older age at menopause (P heterogeneity = 0.04). High scores for the proliferation factor were also associated with early menarche (P heterogeneity < 0.0001), and in contrast to the estrogen metabolism/ER-beta factor, higher current body mass index among premenopausal women (P heterogeneity = 0.03). Our analysis of hormonal pathway markers independently confirmed several previously defined molecular subtypes identified by gene expression profiling and augmented these findings by suggesting the existence of additional relationships related to ER-beta and enzymes involved in hormone metabolism.  相似文献   
999.
Monitoring changes in cerebral blood flow in association with neuronal activity has widely been used to evaluate various brain functions. However, current techniques do not directly measure blood flow changes in specified blood vessels. The present study identified arterioles within the cerebral cortex by echoencephalography and color Doppler imaging, and then measured blood flow velocity (BFV) changes in pulsed-wave Doppler mode. We applied this "transdural Doppler ultrasonography (TDD)" to examine BFV changes in the cortical motor-related areas of monkeys during the performance of unimanual (right or left) and bimanual key-press tasks. BFV in the primary motor cortex (MI) was increased in response to contralateral movement. In each of the unimanual and bimanual tasks, bimodal BFV increases related to both the instruction signal and the movement were observed in the supplementary motor area (SMA). Such BFV changes in the SMA were prominent during the early stage of task training and gradually decreased with improvements in task performance, leaving those in the MI unchanged. Moreover, BFV changes in the SMA depended on task difficulty. The present results indicate that TDD is useful for evaluating regional brain functions.  相似文献   
1000.
PURPOSE: To use transabdominal sonography to determine the frequency of visualization of the adult normal appendix in patients with suspected acute infectious enteritis (AIE) compared with patients with acute appendicitis (AA) and a control group. METHODS: A total of 296 patients divided into 3 different groups underwent sonographic examination, including 120 randomly selected asymptomatic patients, 91 consecutive patients with AIE, and 85 consecutive patients with AA. In the 3 groups, visualization rate, outer appendiceal diameter, presence or absence of inflamed periappendiceal fat, and location of the appendix were recorded. RESULTS: The visualization rates of the appendix were 49.2%, 70.3%, and 96.5% for the control, AIE, and AA groups, respectively (P < 0.05). The mean +/- SD outer appendiceal diameters for the 3 groups were 4.5 +/- 1.2 mm, 4.5 +/- 1.4 mm, and 7.9 +/- 2.0 mm, respectively. The difference between outer appendiceal diameter in the control and AIE groups was not statistically significant. Periappendiceal inflamed fat was detected in all AA cases, but in none of the AIE cases. CONCLUSION: The appendix was visualized more often in patients with AIE than in the control group, although the outer appendiceal diameter of the AIE group was not significantly different from that of the normal appendix seen in the control group.  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