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   7578篇
  免费   394篇
  国内免费   49篇
耳鼻咽喉   40篇
儿科学   181篇
妇产科学   65篇
基础医学   1004篇
口腔科学   115篇
临床医学   487篇
内科学   2204篇
皮肤病学   103篇
神经病学   597篇
特种医学   287篇
外科学   1271篇
综合类   27篇
预防医学   221篇
眼科学   157篇
药学   477篇
中国医学   27篇
肿瘤学   758篇
  2023年   37篇
  2022年   71篇
  2021年   133篇
  2020年   73篇
  2019年   99篇
  2018年   108篇
  2017年   110篇
  2016年   148篇
  2015年   170篇
  2014年   186篇
  2013年   224篇
  2012年   399篇
  2011年   474篇
  2010年   223篇
  2009年   243篇
  2008年   403篇
  2007年   525篇
  2006年   443篇
  2005年   502篇
  2004年   481篇
  2003年   507篇
  2002年   455篇
  2001年   126篇
  2000年   102篇
  1999年   128篇
  1998年   147篇
  1997年   113篇
  1996年   128篇
  1995年   121篇
  1994年   95篇
  1993年   72篇
  1992年   72篇
  1991年   78篇
  1990年   78篇
  1989年   71篇
  1988年   63篇
  1987年   46篇
  1986年   52篇
  1985年   33篇
  1984年   43篇
  1983年   43篇
  1982年   33篇
  1981年   40篇
  1980年   39篇
  1979年   26篇
  1978年   46篇
  1977年   40篇
  1976年   20篇
  1975年   24篇
  1974年   22篇
排序方式: 共有8021条查询结果,搜索用时 15 毫秒
1.
BACKGROUND Minimally invasive surgery for gastric cancer(GC) has gained widespread use as a safe curative procedure especially for early GC.AIM To determine risk factors for postoperative complications after minimally invasive gastrectomy for GC.METHODS Between January 2009 and June 2019, 1716 consecutive patients were referred to our division for primary GC. Among them, 1401 patients who were diagnosed with both clinical and pathological Stage Ⅲ or lower GC and underwent robotic gastrectomy(RG) or laparoscopic gastrectomy(LG) were enrolled. Retrospective chart review and multivariate analysis were performed for identifying risk factors for postoperative morbidity.RESULTS Morbidity following minimally invasive gastrectomy was observed in 7.5% of the patients. Multivariate analyses demonstrated that non-robotic minimally invasive surgery, male gender, and an operative time of ≥ 360 min were significant independent risk factors for morbidity. Therefore, morbidity was compared between RG and LG. Accordingly, propensity-matched cohort analysis revealed that the RG group had significantly fewer intra-abdominal infectious complications than the LG group(2.5% vs 5.9%, respectively; P = 0.038), while no significant differences were noted for other local or systemic complications.Multivariate analyses of the propensity-matched cohort revealed that non-robotic minimally invasive surgery [odds ratio = 2.463(1.070–5.682); P = 0.034] was a significant independent risk factor for intra-abdominal infectious complications.CONCLUSION The findings showed that robotic surgery might improve short-term outcomes following minimally invasive radical gastrectomy by reducing intra-abdominal infectious complications.  相似文献   
2.
3.
4.
Fibroblastic connective tissue nevus (FCTN) is a benign cutaneous mesenchymal lesion characterized by proliferation of CD34‐positive fibroblastic/myofibroblastic spindle‐shaped cells. We report a case of agminated FCTN on the right lower abdomen of a 1‐year‐old boy.  相似文献   
5.
In Cryptococcus neoformans the DNA content of cells having tiny buds varied rather widely, depending on growth phases and strains used. Typically, buds of C. neoformans emerged soon after initiation of DNA synthesis in the early exponential phase. However, bud emergence was delayed to G2 during transition to the stationary phase, and in the early stationary phase budding scarcely occurred, although roughly half of the cells completed DNA synthesis. The timing of budding in C. neoformans was shifted to later cell cycle points with progression of the growth phase of the culture. Similarly, a deficit in oxygen was demonstrated to delay the timing of budding, prolong the G2 phase and cause accumulation of cells after DNA synthesis, but before commitment to budding. The C. neoformans homologue of the main cell cycle control gene CDC28/Cdc2 was isolated using degenerate RT-PCR. The full-length coding region was then amplified using primers to target the regions around the start and stop codons. The gene was called CnCdk1 and was found to have high homologies to S. cerevisiae CDC28 and S. pombe cdc2. To determine its function, its ability to rescue S. cerevisiae cdc28-temperature sensitive mutants was tested. S. cerevisiae cdc28-4 and cdc28-1N strains transformed with the pYES2-CnCdk1 construct exhibited growth at the restrictive temperature. Results of the sequence analysis and the ability of CnCdk1 to complement the S. cerevisiae cdc28-ts mutations support its assumed role as the CDC28/cdc2 homologue in C. neoformans.  相似文献   
6.
7.
Effects of a newly introduced polyoxyethylene-modified superoxide dismutase (SOD-POE) on reperfusion induced arrhythmias were examined in the pentobarbital anesthetized rat. Reperfusion induced arrhythmias were elicited by occlusion of the left anterior descending coronary artery (LAD) for 15 min and subsequent release. The LAD occlusion was performed by compressing the artery using a suction cup of 2 mm in diameter placed on the LAD to which negative pressure was applied. The LAD occlusion and release was repeated at an interval of 30 min. SOD-POE or human SOD (h-SOD) (1000 U/kg) was injected intravenously 15 min prior to the occlusion at the second trial of the occlusion. In the control group, various types of arrhythmias including ventricular fibrillation (Vf), ventricular tachycardia (VT), premature ventricular contraction (PVC) and premature atrial contraction (PAC) were elicited immediately after release of the occlusion. In the SOD-POE-treated group, Vf and VT were completely prevented and the numbers of PVC and PAC significantly decreased, while pretreatment with h-SOD did not prevent the occurrence of reperfusion induced arrhythmias. The protective effects of SOD-POE lasted for more than 90-120 min. The plasma half life for SOD-POE was 10.8 hr, while that for h-SOD was 8.6 min. Results indicate that intravenous administration of SOD-POE would provide a new means of preventing reperfusion induced arrhythmias occurring in clinical situations.  相似文献   
8.
The role of intracellular Zn2+ in the translocation of protein kinase C from cytosol to membrane fractions was examined by the [3H]phorbol 12,13-dibutyrate (PDBu) binding method in guinea pig cerebral synaptoneurosomes. N-methyl-d-aspartate (NMDA, 100 μM) and calcium ionophore A23187 (0.3–30 μM) decreased the binding activity in the cytosol with a concomitant increase in the membrane fractions. Pretreatment of synaptoneurosomes with a heavy metal chelator, N,N,N′,N′-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN), inhibited the NMDA- and A23187-induced changes of the distribution of [3H]PDBu binding sites in cytosol and membrane fractions. The inhibitory effect of TPEN was negated by a preincubation of TPEN with equimolar Zn2+ but not by that with Ca2+. The addition of 500 μM Zn2+ to the lysate of synaptoneurosomes induced an increase of [3H]PDBu binding activity in the membrane fraction with a concomitant decrease in the cytosol fraction, as did 100 μM Ca2+. Low concentrations of Zn2+ (10 μM), which alone had no effect on the distribution of the binding, significantly enhanced the effect of 10 μM Ca2+ in the lysate. Under those conditions TPEN inhibited the Zn2+-potentiated Ca2+-dependent changes in the binding. These results suggest that intracellular Zn2+ is essential for the agonist-induced translocation of protein kinase C in guinea pig synaptoneurosomes.  相似文献   
9.
OBJECTIVE: To examine the influence of in-season injury prevention training on hip and knee kinematics during a landing task. DESIGN: Longitudinal pre-post intervention study. SETTING: Testing sessions were conducted in a biomechanics research laboratory. PARTICIPANTS: Eighteen female soccer players between the ages of 14 and 17 participated in this study. All subjects were healthy with no current complaints of lower extremity injury. INTERVENTIONS: Testing sessions were conducted prior to and following a season of soccer practice combined with injury prevention training. MAIN OUTCOME MEASUREMENTS: During each testing session three-dimensional kinematics were collected while each subject performed a drop landing task. Peak hip and knee joint angles were measured during the early deceleration phase of landing and compared between pre- and post-training using paired t-tests. RESULTS: Following a season of soccer practice combined with injury prevention training, females demonstrated significantly less hip internal rotation (7.1 degrees vs. 1.9 degrees; P = 0.01) and significantly greater hip abduction (-4.9 degrees vs. -7.7 degrees; P = 0.02). No differences in knee valgus or knee flexion angles were found post-season. CONCLUSIONS: Female soccer players exhibited significant changes in hip kinematics during a landing task following in-season injury prevention training. Our results support the premise that a season of soccer practice combined with injury prevention training is effective in altering lower extremity motions that may play a role in predisposing females to ACL injury.  相似文献   
10.
Humoral hypercalcemia of malignancy (HHM) in neoplastic syndrome has been most commonly reported in squamous cell carcinoma. Gallbladder carcinoma with HHM is uncommon. In this report, we describe a male case of gallbladder carcinoma with marked hypercalcemia and a high level of serum parathyroid hormone-related peptide (PTHrP). An immunohistochemical examination using PTHrP was also positive.  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