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   4182篇
  免费   262篇
  国内免费   21篇
耳鼻咽喉   37篇
儿科学   138篇
妇产科学   69篇
基础医学   555篇
口腔科学   110篇
临床医学   332篇
内科学   1047篇
皮肤病学   166篇
神经病学   373篇
特种医学   83篇
外科学   458篇
综合类   14篇
预防医学   391篇
眼科学   54篇
药学   323篇
中国医学   17篇
肿瘤学   298篇
  2023年   36篇
  2022年   76篇
  2021年   160篇
  2020年   72篇
  2019年   144篇
  2018年   154篇
  2017年   104篇
  2016年   99篇
  2015年   122篇
  2014年   140篇
  2013年   200篇
  2012年   281篇
  2011年   298篇
  2010年   172篇
  2009年   128篇
  2008年   234篇
  2007年   230篇
  2006年   219篇
  2005年   237篇
  2004年   221篇
  2003年   200篇
  2002年   200篇
  2001年   82篇
  2000年   91篇
  1999年   87篇
  1998年   39篇
  1997年   23篇
  1996年   25篇
  1995年   16篇
  1994年   12篇
  1993年   16篇
  1992年   25篇
  1991年   35篇
  1990年   34篇
  1989年   27篇
  1988年   21篇
  1987年   18篇
  1986年   17篇
  1985年   26篇
  1984年   11篇
  1983年   12篇
  1982年   7篇
  1981年   7篇
  1980年   7篇
  1979年   16篇
  1977年   8篇
  1975年   8篇
  1973年   12篇
  1972年   11篇
  1971年   9篇
排序方式: 共有4465条查询结果,搜索用时 31 毫秒
31.
Micronuclei and other biomarkers were evaluated in oral cells from 11- to 16-year-old girls living in a foster home in the central area of México City. Variables analyzed for possible association with these biomarkers include smoking habits, body mass index, metabolic polymorphisms for NAT1 and GSTM1 and whether the cells were obtained from the cheek or pharynx. The results indicated that individuals having the NAT1*10 homozygous genotype showed a significant increase in chromatin buds and binucleated cells. When the damage in the cheek was compared with damage in the pharynx, a significant increase in micronuclei and binucleated cells was found for the latter tissue in all the individuals analyzed.  相似文献   
32.
We describe two sibs with tetraectrodactyly and oligomeganephronic renal hypoplasia. The parents were unaffected. This syndrome of apparently autosomal recessive origin appears to be the first Mendelian form of the acrorenal developmental field defect identified so far. © 1992 Wiley-Liss, Inc.  相似文献   
33.
Liquid chromatographic procedure with fluorimetric detection for chiral separation and quantification of salbutamol enantiomers in urine samples has been developed. The extraction of free salbutamol from urine has been considered using liquid-liquid and solid-phase procedures. The effect of pH, salting-out effect and organic solvent has been studied in liquid-liquid extraction from aqueous and urine samples. For solid-phase extraction, different mechanisms (polar, non-polar, cation-exchange and interactions with a polymeric phase) have been tested and the effect of the urine matrix on the extraction recoveries has been considered. Bond-Elut Certify extraction cartridges provided the best specificity and good recoveries for salbutamol in urine. The sample is acidified, applied to the preconditioned cartridges and, after a washing step, salbutamol enantiomers are eluted with a mixture of chloroform and 2-propanol (80:20, v/v) containing 2% ammonia. Atenolol is used as external standard. Enantioselective separation is accomplished with a Chirex 3022 stationary phase (urea type silica-bonded chiral phase) using a mobile phase containing hexane-dichloromethane-methanol-trifluoroacetic acid (250:218:31:1, v/v) and fluorimetric detection with excitation and emission wavelengths set at 230 and 309 nm, respectively. The method proposed is rapid, selective and sensitive, and seems to be useful to differentiate between an authorized and a prohibited use of the drug in doping control.  相似文献   
34.
We describe the case of a 15‐year‐old girl with multiple congenital anomalies, dysmorphic features, severe kyphoscoliosis, growth and mental retardation, and the absence of speech, in whom 35% of the cells carried a supernumerary ring chromosome 1. Fluorescence in situ hybridization (FISH) analysis using YAC/BAC clones spanning the region from 1p13 to 1q21 made it possible to determine the genomic content and structure of the ring(1), which was found to consist of the cytogenetic bands 1q21–22. A complex structure was delineated in the ring chromosome with a partial inverted duplication delimited by markers WI‐7732 and WI‐607, with WI‐7396 and WI‐8386 being the boundaries of the single copy segment. Comparison of the clinical signs of other patients with mosaic r(1) reported in the literature allowed the identification of a patient sharing a number of clinical signs including cataracts. Given that mutations of the GJA8 gene encoding connexin 50 (Cx50) and mapping to 1q21 have been associated with the presence of cataracts, it is possible that a gain in copy number or a rearrangement of GJA8 may contribute to cataractogenesis.  相似文献   
35.
36.
Streptococcus suis serotype 2 is known to be a major pathogen of swine, causing mainly meningitis. It is also a zoonotic agent leading predominantly to meningitis in humans working in close contact with pigs. In this study, we investigated the ability of S. suis to up-regulate the expression of adhesion molecules involved in inflammation, using an enzyme-linked immunosorbent assay. S. suis serotype 2 stimulated the up-regulation of the expression of intercellular adhesion molecule-1 (ICAM-1, CD54), CD11a/CD18 and CD11c/CD18 on human THP-1 monocytes, but did not change that of ICAM-1, vascular cell adhesion molecule-1 (VCAM-1, CD106) and E-selectin (CD62E) on human endothelial cells. The up-regulation of adhesion molecules was time- and bacterial concentration-dependent, and cell wall components were largely responsible for such stimulation. To a lesser extent, purified haemolysin of S. suis also stimulated adhesion molecule expression. Stimulation of monocytes with strains of different origin showed that there was no clear tendency for human strains to induce a higher expression of adhesion molecules than strains from diseased pigs. Finally, monocytes stimulated with S. suis also showed an increase in adherence to endothelial cells. Hence, S. suis is capable of up-regulating important adhesion molecules involved in inflammation, which may result in an increased leucocyte recruitment into sites of infection, thus providing a possible mechanism for some of the inflammatory features of meningitis caused by this pathogen.  相似文献   
37.
Although B-cell chronic lymphocytic leukemia (B-CLL) is the most common form of leukemia in Western countries, little is known about its underlying molecular abnormalities and their prognostic significance, particularly for use in early therapeutic interventions in young patients. As TP53 tumor suppressor gene abnormalities and 11q23 deletions are reported to be prognostically adverse in hematologic malignancies, we used interphase fluorescence in situ hybridization to analyze their incidence and prognostic significance in young B-CLL patients. Bone marrow samples from 40 untreated B-CLL patients at diagnosis were studied using five yeast artificial chromosome clones from the 11q23.1 approximately q23.3 chromosomal region and a probe specific for the 17p13.1 locus. Twenty-three patients (58%) carried 11q deletions. Interestingly, 16 of 17 patients (94%) who showed early disease progression exhibited this chromosomal abnormality, suggesting that 11q deletions may help to identify more aggressive disease in early stage patients. In contrast, monoallelic TP53 deletions were found in all of the patients. The TP53 and 11q deletions were only present in a proportion of the clonal B-cells, which suggests that they are secondary events in B-CLL.  相似文献   
38.
Beer is a popular beverage and some beneficial effects have been attributed to its moderate consumption. We carried out a pilot study to test if beer and non-alcoholic beer consumption modify the levels of a panel of 53 cardiometabolic microRNAs in plasma and macrophages. Seven non-smoker men aged 30–65 with high cardiovascular risk were recruited for a non-randomised cross-over intervention consisting of the ingestion of 500 mL/day of beer or non-alcoholic beer for 14 days with a 7-day washout period between interventions. Plasma and urine isoxanthohumol were measured to assess compliance with interventions. Monocytes were isolated and differentiated into macrophages, and plasma and macrophage microRNAs were analysed by quantitative real-time PCR. Anthropometric, biochemistry and dietary parameters were also measured. We found an increase in plasma miR-155-5p, miR-328-3p, and miR-92a-3p after beer and a decrease after non-alcoholic beer consumption. Plasma miR-320a-3p levels decreased with both beers. Circulating miR-320a-3p levels correlated with LDL-cholesterol. We found that miR-17-5p, miR-20a-5p, miR-145-5p, miR-26b-5p, and miR-223-3p macrophage levels increased after beer and decreased after non-alcoholic beer consumption. Functional analyses suggested that modulated microRNAs were involved in catabolism, nutrient sensing, Toll-like receptors signalling and inflammation. We concluded that beer and non-alcoholic beer intake modulated differentially plasma and macrophage microRNAs. Specifically, microRNAs related to inflammation increased after beer consumption and decreased after non-alcoholic beer consumption.  相似文献   
39.
BackgroundSleeve gastrectomy (SG) leads to esophageal mucosal damage in an elevated percentage of cases, configuring a clinical condition of Barrett’s esophagus (BE) in a proportion as high as 15–18.8%. BE may rarely evolve into esophageal adenocarcinoma (EAC).ObjectivesTo raise awareness of BE as a precancerous lesion which may progress toward malignancy after this popular bariatric procedure.SettingBariatric referral centers, Italy.MethodsAll patients referred to our bariatric center who developed an EAC after SG between 2012 and 2019 were reviewed and consecutively included in this study. The available scientific literature regarding this complication is additionally reviewed.ResultsThe 3 male patients comprised in this case series underwent laparoscopic SG between 2012 and 2015 in different bariatric referral centers. Age and body mass index at baseline ranged from 21–54 years and 43.1–75.6 kg/m2, respectively. All patients were lost to follow-up early after surgery (3.7 ± 1.4 months), and were diagnosed with EAC at a mean of 27.3 ± 7.6 months after SG. The 4 reported cases in the scientific literature developed an EAC at a mean of 32.5 ± 23 months from SG. Overall, a diagnosis of EAC was made approximately 30.3 ± 17.1 months postoperatively, which seems relatively and worryingly early after surgery.ConclusionAlthough the rate and probability of progression from BE to EAC is still not well defined, assuming that the rising popularity and execution of SG leads to a growth in the BE incidence, then the preoperative identification and stratification of cancer risk factors in this subset of patients is strongly encouraged. Clinical and endoscopic follow-ups are essential to allow for prevention and early diagnosis and for epidemiologic data collection purposes.  相似文献   
40.
BackgroundThis is the first-in-human study of icenticaftor, an oral potentiator of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) channel. Restoration of CFTR activity has shown significant clinical benefits, but more studies are needed to address all CFTR mutations.MethodsSafety, pharmacodynamics/pharmacokinetics of icenticaftor were evaluated in a randomized, double-blind, placebo-controlled study in healthy volunteers. Efficacy was assessed in adult CF patients with ≥1 pre-specified CFTR Class III or IV mutation (150 and 450 mg bid), or homozygous for F508del mutation (450 mg bid). Primary efficacy endpoint was change from baseline in lung clearance index (LCI2.5). Secondary endpoints included %predicted FEV1 and sweat chloride level.ResultsClass IV mutations were present in 22 patients, Class III in 2 (both S549N), and 25 were homozygous for F508del. Icenticaftor was well-tolerated in healthy and CF subjects with no unexpected events or discontinuations in the CF groups. The most frequent study-drug related adverse events in CF patients were nausea (12.2%), headache (10.2%), and fatigue (6.1%). Icenticaftor 450 mg bid for 14 days showed significant improvements in all endpoints versus placebo in patients with Class III and IV mutations; mean %predicted FEV1 increased by 6.46%, LCI2.5 decreased by 1.13 points and sweat chloride decreased by 8.36 mmol/L. No significant efficacy was observed in patients homozygous for a single F508del.ConclusionsIcenticaftor was safe and well-tolerated in healthy volunteers and CF patients, and demonstrated clinically meaningful changes in lung function and sweat chloride level in CF patients with Class III and IV CFTR mutations.ClinicalTrials.gov: NCT02190604  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