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   8720篇
  免费   771篇
  国内免费   16篇
耳鼻咽喉   67篇
儿科学   247篇
妇产科学   145篇
基础医学   1279篇
口腔科学   186篇
临床医学   993篇
内科学   1746篇
皮肤病学   350篇
神经病学   722篇
特种医学   295篇
外国民族医学   2篇
外科学   1013篇
综合类   130篇
一般理论   13篇
预防医学   929篇
眼科学   199篇
药学   673篇
中国医学   20篇
肿瘤学   498篇
  2023年   46篇
  2022年   76篇
  2021年   187篇
  2020年   128篇
  2019年   151篇
  2018年   202篇
  2017年   147篇
  2016年   158篇
  2015年   170篇
  2014年   201篇
  2013年   329篇
  2012年   423篇
  2011年   456篇
  2010年   256篇
  2009年   230篇
  2008年   382篇
  2007年   446篇
  2006年   384篇
  2005年   425篇
  2004年   411篇
  2003年   368篇
  2002年   364篇
  2001年   278篇
  2000年   289篇
  1999年   225篇
  1998年   129篇
  1997年   87篇
  1996年   87篇
  1995年   75篇
  1994年   63篇
  1993年   56篇
  1992年   190篇
  1991年   164篇
  1990年   173篇
  1989年   172篇
  1988年   151篇
  1987年   138篇
  1986年   129篇
  1985年   108篇
  1984年   99篇
  1983年   70篇
  1982年   55篇
  1981年   55篇
  1980年   45篇
  1979年   73篇
  1978年   65篇
  1977年   62篇
  1976年   46篇
  1975年   54篇
  1973年   54篇
排序方式: 共有9507条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: Development of distant metastases is one of the primary characteristics of malignant tumours. During the last decades, lung metastasectomy has been progressively accepted as a therapeutic option in oncology patients. The present paper aims to evaluate the long-term results and factors influencing prognosis in patients submitted to lung resection for metastases from extrapulmonary epithelial tumours. METHODS: We retrospectively analysed data of 202 patients undergoing 207 procedures of lung metastasectomy between January 1980 and December 2003. Factors that may influence long-term prognosis such as completeness of resection, histology of the tumour, disease-free interval, number of resected lesions, involvement of hilar or mediastinal lymph nodes, systemic treatments were investigated. RESULTS: Complete resection was carried out in 169 patients (83.7%). The more frequent lung resection was sublobar in 67.6% of cases, but rarely in selected patients bilobectomy or pneumonectomy has been carried out too. Perioperative morbidity and mortality were 7.7% and 0.9%. Mean disease-free interval was 49+/-48 months. Mean follow-up was 33+/-31 months, 5-year and 10-year survival rates for completely resected patients were 43% and 17%, respectively. By univariate and multivariate analyses, completeness of resection, disease-free interval of 36 months or more, and single resected metastasis were found to be significant prognostic factors. CONCLUSIONS: Resection of epithelial lung metastases allows an acceptable prognostic result in appropriately selected patients with very low perioperative morbidity and mortality. Factors such as high disease-free interval, single metastasis and completeness of resection are demonstrated and confirmed to be significantly associated with long-term survival.  相似文献   
42.
The superior sagittal sinus (SSS) and the trigeminal ganglion (Vg) of anesthetized cats were stimulated electrically and field potentials in the upper cervical spinal cord and regional cerebral blood flow were recorded. Stimulation of the entire ganglion produced smaller field potential changes in two regions (medioventral area (MVA); dorsolateral area (DLA] of the upper spinal cord than did stimulation of the sagittal sinus (Vg/SSS response ratio = 17% for the MVA and 48% for the DLA). Stimulation of the trigeminal ganglion increased blood flow in only the frontal and parietal cortices (+93% and +33%), whereas stimulation of the sinus produced both larger changes in these areas (+137% and +139%) and also produced changes in regional cerebral blood flow in the thalamus (+122%).  相似文献   
43.
Molecular characterization of in vivo mutation at the human hypoxanthine phosphoribosyltransferase (hprt) locus has revealed a broad spectrum of mutation, both with regard to germ-line mutation in Lesch-Nyhan and gout patients, and somatic mutation in 6-thioguanine resistant T-lymphocytes from healthy individuals. The pattern of missense mutation shows a non-random distribution with a preferential location to codons for amino acids which are identical in human and the two parasites Schistosoma mansoni and Plasmodium falciparum. Although these 'evolutionary conserved' amino acids account for only 32% of the amino acids in the human hprt protein, they are involved in 76% of the missense mutations at the hprt locus in human T-lymphocytes, 67% in Lesch-Nyhan patients (with severe hprt-deficiency), but only 43% in gout patients (with partial hprt deficiency). This observation supports the notion that evolutionary conserved amino acids constitute functionally important sites in the hprt enzyme, and missense mutations affecting these amino acids will often lead to complete loss of enzyme activity. Substitutions of 'non-conserved' amino acids cause less severe hprt-deficiency (as seen in the gout patients), or may even escape clinical diagnosis. These considerations are important for the understanding of structure-activity relationships in the hprt protein, possible differences between hprt mutational spectra in germ-line and somatic cells, and the mutational spectra induced by specific exogeneous mutagens.  相似文献   
44.
1. The pharmacological and biophysical properties of a recombinant 5-HT3 receptor have been studied by use of patch-clamp techniques applied to HEK 293 cells stably transfected with the murine 5-HT3 R-A cDNA. 2. At a holding potential of -60 mV, 77% of cells investigated responded to ionophoretically applied 5-HT with an inward current. Such currents were unaffected by methysergide (1 microM), or ketanserin (1 microM), but were antagonized in a concentration-dependent and reversible manner by the selective 5-HT3 receptor antagonist, ondansetron (IC50 = 440 pM) and the non-selective antagonists (+)-tubocurarine (IC50 = 1.8 nM) and metoclopramide (IC50 50 nM). 3. The 5-HT-induced current reversed in sign (E5-HT) at approximately -2mV and exhibited inward rectification. The influence of extra- and intracellular ion substitutions upon E5-HT indicates the 5-HT-evoked current to be mainly mediated by a mixed monovalent cation conductance. 4. Calcium and magnesium (0.1-10 nM) produced a concentration-dependent, voltage-independent, inhibition of the 5-HT-induced response. Zinc (0.3-300 microM) exerted a biphasic effect with low concentrations enhancing, and high concentrations depressing, the 5-HT-evoked current. 5. Fluctuation analysis of inward currents evoked by a low (1 microM) concentration of 5-HT suggests the current to be mediated by the opening of channels with a conductance of 420 fS. 6. The pharmacological and biophysical properties of the 5-HT3 R-A are similar to those previously described for 5-HT3 receptors native to murine neuroblastoma cell lines, with the exception that the function of the recombinant receptor was enhanced by low concentrations of zinc. This observation suggests that the properties of the native receptor are not completely represented by the 5-HT3 R-A subunit alone.  相似文献   
45.
Single dose oral ciprofloxacin was given to all personnel in a naval training establishment as part of the management of an outbreak of meningococcal meningitis. Two thousand one hundred personnel received the drug and Neisseria meningitidis was eradicated from the pharynx of 97% of 570 who were swabbed two to four days later. In a cohort of 277 personnel who were followed for up to nine weeks, pharyngeal carriage was eliminated from 93% of 104 carriers. The overall prevalence of carriage fell from 19% to less than 1.5% as a result of the use of ciprofloxacin. Few side effects were encountered, compliance was good and meningococci resistant to the antibiotic were not found after therapy. A single oral dose of ciprofloxacin 500 mg eliminates pharyngeal carriage of N. meningitidis effectively and has few adverse reactions.  相似文献   
46.
47.
Recent research has found that measuring, monitoring and providing therapists with feedback about their clients' treatment progress improves treatment outcome. This study assessed the level of agreement between two outcome measures used to measure and monitor treatment progress. The Outcome Questionnaire (OQ‐45) was compared with a shorter, derivative measure, the OQ‐30. Each measure has an associated feedback system, which provides therapists with feedback about their clients' treatment progress. The OQ‐45 and the OQ‐30 demonstrated high levels of agreement in measurement of client outcome. The OQ‐45 feedback system emerged as the most accurate and clinically useful method for providing therapists with feedback about their clients' predicted treatment outcomes. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
48.
Background: Inhaled administration of milrinone reduces pulmonary artery pressure. Pulmonary hypertension (PH) and right heart failure are associated with difficult separation from cardiopulmonary bypass (CPB). Therefore, inhaled milrinone could facilitate separation from CPB. Objective: To determine the impact and timing of administration of inhaled milrinone. Methods: A retrospective analysis of our experience on high-risk patients receiving inhaled milrinone was conducted to evaluate the postoperative course after administration of the drug. Results: Seventy-three patients received inhaled milrinone from June 2002 to February 2005. Mean age was 64 ± 13 years, with a mean preoperative Parsonnet score of 27 ± 14. Inhaled milrinone (5 mg) was administered before (n = 30) or after (n = 40) CPB, three patients had off-pump procedures and were excluded. CPB time was 145 ± 78 min with cross-clamping times of 91 ± 56 min without any significant difference between groups. Fifty-four patients (74%) had difficult separation from CPB, 14 patients (19%) required an intra-aortic balloon pump and 10 patients (14%) needed emergency reinitiation of CPB for hemodynamic instability. Ten patients died in the perioperative period (13.7%). Patients receiving inhaled milrinone prior to CPB initiation had a lowering pulmonary artery pressure after CPB (p < .01) and had less emergency reinitiation of CPB after weaning (3% vs 23%, p = .02) as compared to those with administration after CPB. No detectable side effects were directly linked to the administration of the drug. Conclusion: In this high-risk cohort, use of inhaled milrinone was well tolerated. Administration before initiation of CPB could help weaning from CPB.  相似文献   
49.
BACKGROUND: According to the German Law on Infectious Diseases (Infektionsschutzgesetz or IfSG) German outpatient centres must provide evidence of maintaining certain standards of hygiene and record their nosocomial infection rates. To fulfill their legal obligations, the Commission for Hospital Hygiene and the Prevention of Infection recommends surveillance modules such as that known as AMBU-KISS. MATERIALS AND METHODS: The AMBU-KISS project centre implemented a survey to evaluate all procedures relevant to hygiene, surveillance of surgical site infections, and facilities available at centres participating in the AMBU-KISS surveillance programme. The questionnaire was returned by 99 of 110 participants. RESULTS AND DISCUSSION: All the centres possess cleaning and disinfection schemes, and practically all of them use written instructions on the processing of instruments and surgical hand disinfection procedure. Many of the participants spend too much time on surgical hand disinfection and presurgical skin disinfection. CONCLUSION: The survey demonstrates that hygienic conditions at centres participating in AMBU-KISS are largely satisfactory. However, there is nevertheless a need to optimise infection control measures.  相似文献   
50.
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