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   21994篇
  免费   1080篇
  国内免费   202篇
耳鼻咽喉   261篇
儿科学   485篇
妇产科学   237篇
基础医学   2821篇
口腔科学   331篇
临床医学   1319篇
内科学   6199篇
皮肤病学   433篇
神经病学   1602篇
特种医学   908篇
外科学   3589篇
综合类   86篇
预防医学   573篇
眼科学   421篇
药学   1288篇
中国医学   34篇
肿瘤学   2689篇
  2023年   162篇
  2022年   353篇
  2021年   608篇
  2020年   304篇
  2019年   393篇
  2018年   568篇
  2017年   459篇
  2016年   515篇
  2015年   548篇
  2014年   662篇
  2013年   852篇
  2012年   1333篇
  2011年   1548篇
  2010年   928篇
  2009年   806篇
  2008年   1366篇
  2007年   1438篇
  2006年   1455篇
  2005年   1449篇
  2004年   1467篇
  2003年   1319篇
  2002年   1316篇
  2001年   250篇
  2000年   195篇
  1999年   257篇
  1998年   282篇
  1997年   239篇
  1996年   177篇
  1995年   179篇
  1994年   161篇
  1993年   158篇
  1992年   151篇
  1991年   151篇
  1990年   115篇
  1989年   120篇
  1988年   94篇
  1987年   84篇
  1986年   82篇
  1985年   68篇
  1984年   75篇
  1983年   66篇
  1982年   46篇
  1981年   52篇
  1980年   56篇
  1979年   45篇
  1978年   43篇
  1977年   33篇
  1975年   27篇
  1974年   25篇
  1969年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
Background and Aims  It has been widely accepted that sperm hyperactivation is regulated by protein phosphorylations. But, the sperm hyperactivation phosphorylation pathway is not well understood yet because several different proteins have been detected in other studies. In order to understand the phosphorylation pathway that regulates hyperactivation, we established how to extract sperm protein completely and detected proteins that were phosphorylated during hyperactivation. Methods  Protein phosphorylation of hamster spermatozoa was detected by western blotting using antiphospho-amino acid monoclonal antibodies or the SELDI ProteinChip system with IMAC-Ga(III). Results  We detected 75 protein/peptide phosphoryations using the method established in the present study. Tyrosine phosphorylations occurred during hyperactivation. Serine or threonine phosphorylations occurred for 30 min. Furthermore, four of the serine or threonine phosphorations were phosphorylated by A-kinase. As for peptides, 15 peptides were dephosphorylated for 30 min. Other peptides were phosphorylated during hyperactivation. Conclusions  Because most of the proteins detected in the present study have been described previously, we could detect comprehensive protein phosphorylations. Moreover, we also detected many novel phosphopeptides. Although we did not understand the role of peptide, it was likely that motility was basically regulated by serine/threonine phosphorylations and hyperactivation was mainly regulated by tyrosine phosphorylations. (Reprod Med Biol 2006; 5: 123–135)  相似文献   
123.
OBJECTIVE: To show the positional nystagmus in a patient who had suffered from benign paroxysmal positional vertigo (BPPV) that was thought to be caused by involvement of the anterior semicircular canal (ASCC) (A-BPPV). STUDY DESIGN: Retrospective case report. SETTING: City hospital. PATIENT: The present study reports a rare case of A-BPPV in a 41-year-old woman. CASE REPORT: The patient is 41-year-old woman who developed a positional vertigo after playing volleyball on March 22, 2005 and consulted our hospital the next day. When left Dix-Hallpike maneuver was performed, she showed a positional nystagmus of which fast phase direction of the torsional component was clockwise while that of the vertical component was downward. We plotted the slow phase eye velocity of the positional nystagmus during the left Dix-Hallpike maneuver on three-dimensional coordinates that showed the axis of the positional nystagmus to be perpendicular to the plane of the right ASCC. CONCLUSION: These results suggested that the patient was suffering from A-BPPV.  相似文献   
124.
Caffeine is known to modulate placental and fetal umbilical circulation. It is demonstrated that apoptosis of human umbilical vein endothelial cells (HUVECs) is associated with placental umbilical vascular diseases. The present study was conducted to investigate the effects of caffeine on apoptosis of HUVECs. Isolated HUVECs were cultured under serum-free conditions for 24 h, and then treated with graded concentrations of caffeine (30, 100 and 300 microM) for additional 24 h and 48 h. The number of viable HUVECs was determined by cell counting. Apoptotic HUVECs were assessed by Hoechst33342 dye staining. The expression of caspase-9, caspase-8, caspase-3 and poly(ADP-ribose) polymerase (PARP) was assessed by Western blot analysis. Caffeine induced a dose- and time-dependent decrease in the number of viable HUVECs. Caffeine at concentrations higher than 100 microM significantly increased the percentage of apoptotic HUVECs. Caffeine at concentrations higher than 100 microM significantly increased cleaved caspase-9, caspase-3 and PARP expression in HUVECs at 24-h treatment compared with untreated cultures, whereas 30 microM caffeine significantly increased only caspase-3 expression at 24 h. Caffeine did not affect cleaved caspase-8 expression at 48 h. These results suggest that high concentrations of caffeine inhibit cell growth of HUVECs and induce apoptosis through the caspase-9 pathway.  相似文献   
125.
126.
127.
L-leucine, an essential amino acid, is one of the most popular ingredients in dietary supplements. To investigate a possibility of its embryo-fetal toxicity in rats, 11- to 12-week old dams were orally administered an aqueous solution of L-leucine at doses of 300 or 1000 mg/kg body weight on gestational days 7-17. Body weight and feed intake was evaluated throughout the whole course of pregnancy (days 0-20). L-Leucine did not influence body weight, but at a dose of 1000 mg/kg, slightly enhanced feed intake on days 14 and 18 of pregnancy. Caesarean section (day 20) revealed no influences on the litter size and weight of live-born fetuses, the number of corpora lutea, implantation index or the quality of placenta, and the minor increase in feed intake was considered irrelevant to the pregnancy outcomes. Fetuses were evaluated in a battery of external, visceral and skeletal examinations. No effects of L-leucine on gender ratio and external abnormalities, and no significant treatment-related variations in visceral and skeletal pathologies were observed. These results suggested that L-leucine, administered orally during organogenesis at doses up to 1000 mg/kg body weight, did not affect the outcome of pregnancy and did not cause fetotoxicity in rats.  相似文献   
128.
A 78-year-old woman complained of severe pain in the left costal region. Her body mass index was 23.1 kg/m2. Lateral cutaneous nerve entrapment syndrome (LACNES) was the suspected diagnosis because the affected area was 2×2 cm and positive for pinch sign. Seventeen days later, the patient again presented with complaints of lower back pain accompanied by back pain upon extending the spine. Magnetic resonance imaging of the spine showed a fracture of the vertebral body of T11. We herein discuss our errors in the diagnostic process and critical tactics for avoiding such errors in the future.  相似文献   
129.

Objective

To determine the value of using the Roter Interaction Analysis System during objective structured clinical examinations (OSCEs) to assess pharmacy students'' communication competence.

Methods

As pharmacy students completed a clinical OSCE involving an interview with a simulated patient, 3 experts used a global rating scale to assess students'' overall performance in the interview, and both the student''s and patient''s languages were coded using the Roter Interaction Analysis System (RIAS). The coders recorded the number of utterances (ie, units of spoken language) in each RIAS category. Correlations between the raters'' scores and the number and types of utterances were examined.

Results

There was a significant correlation between students'' global rating scores on the OSCE and the number of utterances in the RIAS socio-emotional category but not the RIAS business category.

Conclusions

The RIAS proved to be a useful tool for assessing the socio-emotional aspect of students'' interview skills.  相似文献   
130.
Anastomotic leakage (AL) after colorectal surgery is a serious complication. This study aimed to evaluate the effectiveness of the EEA™ circular stapler, a new triple-row circular stapler (TCS), relative to a conventional, double-row circular stapler (DCS).A total of 285 patients who underwent anastomosis with the double stapling technique at the Tokyo Medical University Hospital between 2017 and 2021 were included in this nonrandomized clinical trial with historical controls using a propensity score (PS) analysis. The primary endpoint was the risk of AL.We performed a 1:2 PS matching analysis. Before case matching, AL occurred in 15 (7.4%) and 2 (2.4%) patients in the DCS and TCS groups, respectively, with no significant difference (P = .17). After case matching, AL occurred in 13 patients (11.6%) and 1 patient (1.8%) in the DCS and TCS groups, respectively, revealing a significant difference (P = .04). Cox models were created by applying PS to adjust for group differences via regression adjustment. Odds ratios for AL in the DCS group versus the TCS group were 0.31 (95% confidence interval [CI]: 0.07–1.38) in the entire cohort, 0.15 (95% CI: 0.02–0.64) in the regression adjustment cohort, and 0.14 (95% CI: 0.02–1.09) in the 1:2 PS-matched cohort.PS analysis of clinical data suggested that the use of TCS contributes to a reduced risk of AL after colorectal anastomosis CTwith the double stapling technique.  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