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   9878篇
  免费   658篇
  国内免费   70篇
耳鼻咽喉   160篇
儿科学   263篇
妇产科学   226篇
基础医学   1391篇
口腔科学   290篇
临床医学   856篇
内科学   2442篇
皮肤病学   185篇
神经病学   984篇
特种医学   300篇
外科学   1321篇
综合类   78篇
一般理论   6篇
预防医学   560篇
眼科学   200篇
药学   556篇
中国医学   16篇
肿瘤学   772篇
  2023年   94篇
  2022年   176篇
  2021年   350篇
  2020年   214篇
  2019年   289篇
  2018年   325篇
  2017年   214篇
  2016年   266篇
  2015年   302篇
  2014年   369篇
  2013年   546篇
  2012年   742篇
  2011年   725篇
  2010年   397篇
  2009年   359篇
  2008年   632篇
  2007年   591篇
  2006年   529篇
  2005年   528篇
  2004年   455篇
  2003年   416篇
  2002年   391篇
  2001年   123篇
  2000年   95篇
  1999年   118篇
  1998年   83篇
  1997年   42篇
  1996年   46篇
  1995年   48篇
  1994年   51篇
  1993年   28篇
  1992年   70篇
  1991年   71篇
  1990年   66篇
  1989年   57篇
  1988年   51篇
  1987年   64篇
  1986年   51篇
  1985年   51篇
  1984年   45篇
  1983年   39篇
  1982年   27篇
  1981年   28篇
  1979年   45篇
  1978年   35篇
  1977年   35篇
  1976年   34篇
  1974年   36篇
  1973年   33篇
  1970年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Influenza is a disease responsible for thousands of deaths every year. Although healthcare workers (HCWs) represent a way of contagion for patients, vaccination coverage among them is low. Mandatory vaccination has been proposed, but controversies remain. This systematic review and meta-analysis aimed to assess the acceptance of mandatory vaccination by HCWs, and to investigate associated characteristics. MEDLINE, Scopus, Embase, PsycInfo, CINAHL and Web of Science were used to search for studies assessing the topic. PRISMA statements were followed. Of the 13,457 univocal records found, 52 studies were included in the systematic review and 40 in the meta-analysis. The pooled proportion of HCWs accepting the policy was of 61% (95% CI: 53%- 68%) but with great heterogeneity between continents (from 54% in Europe to 69% in Asia) and in different professionals (from 40% in nurses to 80% in students). Vaccinated HCWs agreed more frequently with mandatory vaccination than non-vaccinated ones. More studies that consider mandatory vaccination acceptance as the main outcome are needed, but the results of this study confirm that in some settings the majority of HCWs favour mandatory vaccination. This, combined with effects that a flu epidemic could have if overlapped to pandemics with similar symptoms, requires renewed considerations on mandatory vaccination.  相似文献   
93.
Samples of aqueous fluid were obtained from 35 controls who were people undergoing routine cataract surgery. Similar samples were taken from seven patients with clinically definite multiple sclerosis (MS) and a previous history of optic neuritis, either at cataract surgery or as an elective procedure. Oligoclonal bands were found in only one subject who suffered from the MS-uveitis syndrome.  相似文献   
94.
Plasma retinol and -carotene levels were measured in 502 preschool Guatemalan children from five rural hamlets. Their ages ranged from 6 to 78 months (mean: 42.9±19.2 months); 45% males and 55% females. The mean retinol value in the whole group was 0.9±0.4 µmol/1 (range: 0.1 to 8.4 µmol/1). There was no significant difference between sexes in retinol mean values nor in the incidence of retinol values less than 0.7 µmol/1 (22% in males, 18% in females). When grouped by age and community, significant low retinol mean values were found in two hamlets in the youngest age group (12 to 23 months) as compared to the other age-groups (p<0.05). In the other two hamlets, there were no significant differences among retinol means by age-group. The highest prevalence of deficient retinol values by age-group was in the 12 to 23 months group (40%), and decreased as age increased. The mean value for -carotene in the whole group was 0.13±0.18 µmol/1 (range: 0.01 to 2.23 µmol/1). There were no significant differences in -carotene means between sexes in the whole group. Stratifying the -carotene data by age-groups and community, values were significantly higher in the 48–59 months and 72–83 months groups, as compared with the other age groups in two of the communities (p<0.05). Significant differences across communities for -carotene were found only in the 12 to 23 months group.  相似文献   
95.
96.
PURPOSE: To evaluate excimer laser in situ keratomileusis (LASIK) for hyperopia and its predictability. METHODS: We performed a retrospective study of 100 eyes that had LASIK for hyperopia to assess predictability and long-term stability of refractive results. The Chiron Automated Corneal Shaper was used to create the flap and the Keracor 117CT Chiron-Technolas excimer laser with the plano-scan program was used to ablate all corneas. RESULTS: Mean baseline spherical equivalent manifest refraction was +4.50 +/- 1.73 D (range, +1.25 to +8.50 D). Six months after LASIK, mean manifest spherical equivalent refraction was +0.72 +/- 1.87 D (range, -1.75 to +2.50 D), at 1 year, +0.88 +/- 1.73 D (range, -1.25 to +2.50 D), and at 2 years, +0.85 +/- 1.74 D (range, -0.50 to +2.75 D). Two years after LASIK, 45 eyes (74%) were within +/-1.00 D of intended correction and within +/-1.00 D of emmetropia. Uncorrected visual acuity was 20/40 or better in 50 eyes (82%) at 2 years; 29 eyes (37%) saw 20/20 or better. Undercorrection occurred more frequently in eyes with preoperative keratometric power of more than 45.00 D, when ablation zones less than 6 mm were used and when higher amounts of hyperopic correction were required. CONCLUSION: LASIK with the Keracor 117CT excimer laser appears to be an effective and safe procedure to correct hyperopia. Preoperative keratometric power, amount of hyperopia, and ablation zone diameter affect the efficacy and long-term stability of the procedure.  相似文献   
97.
Fifteen patients with Stage IIIB or IV non-small cell lung cancer gave informed consent to receive three or more 96-hour infusions of ATP at a dose of 50 mcg/kg/min or higher to determine whether ATP has antineoplastic activity against this tumor type and to better define the spectrum of toxicity for ATP given as a single agent. There were no objective complete or partial responses observed. The median survival of the overall group was 187 days and the median time to tumor progression was 113 days. The major toxic side effects were chest pain and dyspnea, leading to the cessation of treatment in 5 patients. We conclude that ATP at this dose and schedule of administration is an inactive agent in patients with advanced non-small cell lung cancer.  相似文献   
98.
Nimesulide release from micronized and unmicronized drug particles was tested at pH 7.4 by measuring the transfer to dimyristoylphosphatidylcholine liposomes (multilamellar and unilamellar vesicles), chosen as a biomembrane model. The perturbing effect of increasing molar fractions of pure nimesulide on the thermotropic behaviour of dimyristoylphosphatidylcholine liposomes was investigated by differential scanning calorimetry. In order to study the drug dissolution process by its uptake into void liposomes, measurements were carried out on suspensions of blank liposomes added to weighed amounts of free powdered nimesulide (micronized and unmicronized). The amount of drug transferred was quantified by comparing the effect caused by the dissolved and released drug to that caused by the free drug that had been previously molecularly dissolved in the liposomes. The calorimetric results show that the dissolution rate depends on the nimesulide form (micronized or unmicronized), and that the transfer to the void liposomes is quicker when the drug is in a micronized form. The uptake was faster when unilamellar vesicles were used instead of multilamellar vesicles because of the greater lipid surface. The calorimetric technique could represent an alternative 'in vitro' method that can be applied to the study of the dissolution kinetics directly at the site of drug uptake, mimicking a biological system.  相似文献   
99.
PURPOSE: The human epidermal growth factor receptor (EGFR) plays an oncogenic role in solid cancer, including brain cancer. The present study was designed to prolong survival in mice with intracranial human brain cancer with the weekly i.v. injection of nonviral gene therapy causing RNA interference (RNAi) of EGFR gene expression. EXPERIMENTAL DESIGN: Human U87 gliomas were implanted in the brain of adult scid mice, and weekly i.v. gene therapy was started at day 5 after implantation of 500000 cells. An expression plasmid encoding a short hairpin RNA directed at nucleotides 2529-2557 within the human EGFR mRNA was encapsulated in pegylated immunoliposomes. The pegylated immunoliposome was targeted to brain cancer with 2 receptor-specific monoclonal antibodies (MAb), the murine 83-14 MAb to the human insulin receptor and the rat 8D3 MAb to the mouse transferrin receptor. RESULTS: In cultured glioma cells, the delivery of the RNAi expression plasmid resulted in a 95% suppression of EGFR function, based on measurement of thymidine incorporation or intracellular calcium signaling. Weekly i.v. RNAi gene therapy caused reduced tumor expression of immunoreactive EGFR and an 88% increase in survival time of mice with advanced intracranial brain cancer. CONCLUSIONS: Weekly i.v. nonviral RNAi gene therapy directed against the human EGFR is a new therapeutic approach to silencing oncogenic genes in solid cancers. This is enabled with a nonviral gene transfer technology that delivers liposome-encapsulated plasmid DNA across cellular barriers with receptor-specific targeting ligands.  相似文献   
100.
PURPOSE: Molecular antagonists of the inhibitor of apoptosis protein survivin have shown promise as novel anticancer strategies for triggering tumor cell apoptosis, dysregulating mitotic progression, and inhibiting tumor growth in preclinical models. However, how survivin couples to the cell death machinery has remained elusive, and the relevant cellular targets of survivin antagonists have not been completely elucidated. Experimental Design: Human umbilical vein and dermal microvascular endothelial cells were infected with replication-deficient adenoviruses encoding survivin (pAd-Survivin), green fluorescent protein (pAd-GFP), or a phosphorylation-defective survivin Thr(34)-->Ala (pAd-T34A) dominant negative mutant. The effect of wild-type or mutant survivin was investigated on capillary network stability, endothelial cell viability, and caspase activation in vitro and on kinetics of tumor growth and development of angiogenesis in a breast cancer xenograft model in vivo. The cell death pathway initiated by survivin targeting was mapped with respect to cytochrome c release, changes in mitochondrial transmembrane potential, and apoptosome requirements using mouse embryonic fibroblasts deficient in Apaf-1 or caspase-9. RESULTS: Adenoviral transduction of endothelial cells with pAd-Survivin inhibited growth factor deprivation- or ceramide-induced apoptosis, reduced caspase-3 and -7 generation, and stabilized three-dimensional capillary networks in vitro. Conversely, expression of pAd-T34A caused apoptosis in umbilical vein and dermal microvascular endothelial cells and resulted in caspase-3 activity. Cell death induced by survivin targeting exhibited the hallmarks of mitochondrial-dependent apoptosis with release of cytochrome c and loss of mitochondrial transmembrane potential and was suppressed in Apaf-1 or caspase-9 knockout mouse embryonic fibroblasts. When injected in human breast cancer xenografts, pAd-T34A inhibited growth of established tumors and triggered tumor cell apoptosis in vivo. This was associated with a approximately 60% reduction in tumor-derived blood vessels by quantitative morphometry of CD31-stained tumor areas, and appearance of endothelial cell apoptosis by internucleosomal DNA fragmentation in vivo. CONCLUSIONS: Survivin functions as a novel upstream regulator of mitochondrial-dependent apoptosis, and molecular targeting of this pathway results in anticancer activity via a dual mechanism of induction of tumor cell apoptosis and suppression of angiogenesis.  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