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   4306篇
  免费   316篇
  国内免费   27篇
耳鼻咽喉   60篇
儿科学   57篇
妇产科学   111篇
基础医学   555篇
口腔科学   124篇
临床医学   400篇
内科学   771篇
皮肤病学   186篇
神经病学   685篇
特种医学   280篇
外科学   549篇
综合类   29篇
一般理论   3篇
预防医学   137篇
眼科学   197篇
药学   238篇
中国医学   4篇
肿瘤学   263篇
  2023年   30篇
  2022年   71篇
  2021年   114篇
  2020年   81篇
  2019年   88篇
  2018年   101篇
  2017年   90篇
  2016年   116篇
  2015年   107篇
  2014年   143篇
  2013年   191篇
  2012年   280篇
  2011年   292篇
  2010年   166篇
  2009年   166篇
  2008年   252篇
  2007年   252篇
  2006年   272篇
  2005年   242篇
  2004年   217篇
  2003年   221篇
  2002年   211篇
  2001年   81篇
  2000年   63篇
  1999年   92篇
  1998年   51篇
  1997年   52篇
  1996年   31篇
  1995年   18篇
  1994年   22篇
  1993年   17篇
  1992年   37篇
  1991年   35篇
  1990年   37篇
  1989年   35篇
  1988年   43篇
  1987年   28篇
  1986年   38篇
  1985年   40篇
  1984年   24篇
  1983年   17篇
  1982年   10篇
  1979年   14篇
  1978年   15篇
  1977年   16篇
  1976年   9篇
  1974年   12篇
  1972年   9篇
  1971年   8篇
  1968年   11篇
排序方式: 共有4649条查询结果,搜索用时 15 毫秒
101.
102.
Correction for ‘Tantalum(v) 1,3-propanediolate β-diketonate solution as a precursor to sol–gel derived, metal oxide thin films’ by Christopher Beale et al., RSC Adv., 2020, 10, 13737–13748, DOI: 10.1039/D0RA02558E.

The authors regret that the plasma treatment and printing parameters were reported incorrectly in the subsection “Deposition on a-SiO2 for UV/Vis spectrophotometry” in the Experimental section of the original article.Before printing, the substrate for both samples was subjected to an argon plasma treatment for 5 minutes (150 W, 0.6 mbar). The plasma power is now corrected to be the same as stated in the “Deposition on a-SiO2 for Raman/XRD” subsection, where originally it was incorrectly stated that “the power was set slightly higher” for the Raman/XRD samples. For both the acetylacetone and benzoylacetone inks, the inks were printed on their respective substrates with a 75 μm drop pitch having dimensions of 400 × 220 drops to create a uniform layer.The correct section is as follows:  相似文献   
103.
104.
105.
We report a case of posterior shoulder instability following anatomic total shoulder arthroplasty (TSA). In addition, we present guidelines to aid in the management of posterior instability after TSA. A 50-year-old male underwent anatomic TSA for glenohumeral osteoarthritis. Postoperatively, the patient developed posterior instability secondary to glenoid retroversion. He did not improve despite conservative treatment. He underwent an arthroscopic posterior bone block procedure, 4-month after his index arthroplasty. At 14-month follow-up, the patient had regained near full motion and strength, and radiographs demonstrated osseous integration with no evidence of component loosening. Posterior instability following TSA is a relatively rare complication and challenging to manage. The posterior, arthroscopic iliac crest bone block grafting procedure represents a treatment option for posterior instability in the setting of a stable glenoid prosthesis following TSA.  相似文献   
106.
Background & Aims: Inactivation of the CDKN2/p16INK4A tumor-suppressor gene is one of the most frequent genetic alterations in human malignancies. In esophageal adenocarcinomas, mutations of the p16 gene or homozygous deletions of the gene locus 9p21 are rare. This study investigated whether p16 promoter hypermethylation is an alternative mechanism for p16 gene inactivation during neoplastic progression in Barrett's esophagus. Methods: A methylation-specific polymerase chain reaction protocol was applied. A total of 95 specimens from 14 patients with Barrett's esophagus were analyzed longitudinally. The p16 promoter status was compared with histomorphological findings. Results: p16 promoter hypermethylation was detected in 9 of the 10 patients who had displayed dysplasia at some time during surveillance, whereas none of the patients who had not displayed dysplasia during surveillance had p16 promoter hypermethylation. p16 promoter hypermethylation was detected in 3% (2 of 67) of the samples without dysplasia, 60% (3 of 5) of the samples with lesions indefinite for dysplasia, 55.6% (10 of 18) of the specimens with low-grade dysplasia, and 75% (3 of 4) of the specimens with high-grade dysplasia. Conclusions: These data suggest that p16 promoter hypermethylation is a common mechanism of p16 gene inactivation during neoplastic progression in Barrett's esophagus.GASTROENTEROLOGY 1998;115:1381-1386  相似文献   
107.
108.
Skin wounds are associated with significant morbidity and mortality. Data are, however, not readily available for benchmarking, to allow prognostic evaluation, and to suggest when involvement of wound‐healing experts is indicated. We, therefore, conducted an observational cohort study to investigate wound healing and all‐cause mortality associated with different types of skin wounds. Consecutive skin wound patients who received wound care by home‐care nurses from January 2010 to December 2011 in a district in Eastern Denmark were included in this study. Patients were followed until wound healing, death, or the end of follow‐up on December 2012. In total, 958 consecutive patients received wound care by home‐care nurses, corresponding to a 1‐year prevalence of 1.2% of the total population in the district. During the study, wound healing was achieved in 511 (53.3%), whereas 90 (9.4%) died. During the first 3 weeks of therapy, healing was most likely to occur in surgical wounds (surgical vs. other wounds: adjusted hazard ratio [AHR] 2.21, 95% confidence interval 1.50–3.23), while from 3 weeks to 3 months of therapy, cancer wounds, and pressure ulcers were least likely to heal (cancer vs. other wounds: AHR 0.12, 0.03–0.50; pressure vs. other wounds: AHR 0.44, 0.27–0.74). Cancer wounds and pressure ulcers were further associated with a three times increased probability of mortality compared with other wounds (cancer vs. other wounds: AHR 3.19, 1.35–7.50; pressure vs. other wounds: AHR 2.91, 1.56–5.42). In summary, the wound type was found to be a significant predictor of healing and mortality with cancer wounds and pressure ulcers being associated with poor prognosis.  相似文献   
109.
110.
Genetic variants underlying life-threatening diseases, being unlikely to be transmitted to the next generation, are gradually and selectively eliminated from the population through negative selection. We study the determinants of this evolutionary process in human genes underlying monogenic diseases by comparing various negative selection scores and an integrative approach, CoNeS, at 366 loci underlying inborn errors of immunity (IEI). We find that genes underlying autosomal dominant (AD) or X-linked IEI have stronger negative selection scores than those underlying autosomal recessive (AR) IEI, whose scores are not different from those of genes not known to be disease causing. Nevertheless, genes underlying AR IEI that are lethal before reproductive maturity with complete penetrance have stronger negative selection scores than other genes underlying AR IEI. We also show that genes underlying AD IEI by loss of function have stronger negative selection scores than genes underlying AD IEI by gain of function, while genes underlying AD IEI by haploinsufficiency are under stronger negative selection than other genes underlying AD IEI. These results are replicated in 1,140 genes underlying inborn errors of neurodevelopment. Finally, we propose a supervised classifier, SCoNeS, which predicts better than state-of-the-art approaches whether a gene is more likely to underlie an AD or AR disease. The clinical outcomes of monogenic inborn errors, together with their mode and mechanisms of inheritance, determine the levels of negative selection at their corresponding loci. Integrating scores of negative selection may facilitate the prioritization of candidate genes and variants in patients suspected to carry an inborn error.

Negative (or purifying) selection is the natural process by which deleterious alleles are selectively purged from the population (1). In diploid species, the strength of negative selection at a given locus is predicted to increase with decreasing fitness and increasing dominance of the genetic variants controlling traits: Variation causing early death in the heterozygous state are the least likely to be transmitted to the next generation, as their carriers have fewer offspring than noncarriers (2). Human genetic variants that cause severe diseases are, thus, expected to be the primary targets of negative selection, particularly for diseases affecting heterozygous individuals. In humans, several studies have ranked protein-coding genes according to their levels of negative selection (35). Nevertheless, the extent to which negative selection affects human disease-causing genes, and the factors determining its strength, remain largely unknown, particularly because our knowledge of the severity, mode, and mechanism of inheritance of the corresponding human diseases remains incomplete (3, 68).The strength of negative selection at a given gene has been traditionally approximated by comparing the coding sequence of the gene in a given species with that of one or several closely related species; it depends on the proportion of amino acid changes that have accumulated during evolution (911). With the advent of high-throughput sequencing, intraspecies metrics have been developed, based on the comparison of the probability of predicted loss-of-function (pLOF) mutations for a gene under a random model with the frequency of pLOF mutations observed in population databases (5, 12, 13), which capture the species-specific evolution of genes. Using an interspecies-based method and a hand-curated version of the Online Mendelian Inheritance in Man (hOMIM) database, a previous study elegantly showed that most human genes for which mutations cause highly penetrant diseases, including autosomal dominant (AD) diseases in particular, evolve under stronger negative selection than genes associated with complex disorders (6). However, other studies based on OMIM genes have reported conflicting results (3, 1417), probably due to the incompleteness and heterogeneity of the datasets used. Moreover, no study has yet addressed this problem with intraspecies metrics, even though it has been suggested that the choice of the reference species for interspecies metrics contributes to discrepancies across studies (6).We aimed to improve the identification of the drivers of negative selection acting on human disease-causing genes, by developing a negative selection score combining several informative intraspecies and interspecies statistics, focusing on inborn errors of immunity (IEI). IEI, previously known as primary immunodeficiencies (18), are genetic diseases that disrupt the development or function of human immunity. They form a large and expanding group of genetic diseases that has been widely studied, and they are well characterized physiologically (immunologically) and phenotypically (clinically) (1921). IEI are often symptomatic in early childhood, and at least until the turn of the 20th century and the introduction of antibiotics, most individuals with IEI probably died before reaching reproductive maturity. Accordingly, IEI genes have probably been under strong negative selection from the dawn of humankind until very recently. In this study, we investigated whether the severity of IEI and their mode and mechanism of inheritance have left signatures of negative selection of various intensities in the corresponding human genes. Furthermore, we validated our model on genes underlying inborn errors of neurodevelopment (IEND), another group of well-characterized severe genetic diseases.  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