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   996篇
  免费   50篇
  国内免费   3篇
耳鼻咽喉   8篇
儿科学   34篇
妇产科学   16篇
基础医学   151篇
口腔科学   11篇
临床医学   80篇
内科学   337篇
皮肤病学   10篇
神经病学   82篇
特种医学   26篇
外科学   69篇
综合类   5篇
预防医学   56篇
眼科学   17篇
药学   103篇
中国医学   1篇
肿瘤学   43篇
  2024年   2篇
  2023年   12篇
  2022年   105篇
  2021年   155篇
  2020年   52篇
  2019年   48篇
  2018年   57篇
  2017年   25篇
  2016年   60篇
  2015年   45篇
  2014年   35篇
  2013年   44篇
  2012年   57篇
  2011年   49篇
  2010年   21篇
  2009年   21篇
  2008年   33篇
  2007年   46篇
  2006年   38篇
  2005年   19篇
  2004年   12篇
  2003年   15篇
  2002年   13篇
  2001年   3篇
  2000年   7篇
  1999年   4篇
  1998年   7篇
  1997年   1篇
  1996年   5篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   6篇
  1991年   7篇
  1990年   3篇
  1989年   1篇
  1988年   5篇
  1987年   6篇
  1986年   5篇
  1985年   2篇
  1984年   1篇
  1983年   4篇
  1982年   1篇
  1981年   3篇
  1979年   3篇
  1977年   1篇
  1974年   1篇
  1972年   2篇
  1970年   1篇
排序方式: 共有1049条查询结果,搜索用时 15 毫秒
41.
42.
A key challenge for carbon dioxide reduction on Cu-based catalysts is its low faradic efficiency (FE) and selectivity towards higher-value products, e.g., ethylene. The main factor limiting the possibilities of long-term applications of Cu-based gas diffusion electrodes (GDE) is a relatively fast drop in the catalytic activity of copper layers. One of the solutions to the catalyst stability problem may be an in situ reconstruction of the catalyst during the process. It was observed that the addition of a small amount of copper lactate to the electrolyte results in increased Faradaic efficiency for ethylene formation. Moreover, the addition of copper lactate increases the lifetime of the catalytic layer ca. two times and stabilizes the Faradaic efficiency of the electroreduction of CO2 to ethylene at ca. 30%. It can be concluded that in situ deposition of copper through reduction of copper lactate complexes present in the electrolyte provides new, stable, and selective active sites, promoting the reduction of CO2 to ethylene.  相似文献   
43.
OBJECTIVE: To document infection with HIV type 1 (HIV-1) group M non-B subtypes in individuals living in New York City. DESIGN: From October 1999 through April 2003, HIV-1-seropositive individuals were selected from 3 clinics in New York City based on having risk factors for infection with HIV-1 non-B subtypes. METHODS: HIV-1 RNA was extracted from plasma samples, and partial gag, pol, or env genes were amplified by PCR analysis. The infecting HIV-1 group M subtype was determined based on results of either heteroduplex mobility assay or sequencing and phylogenetic analysis. RESULTS: Ninety-seven subjects were enrolled in the study. Of the 97 subjects, 91 (94%) were selected based on having emigrated from a non-European country, while 6 (6%) were native United States citizens. Subtypes were successfully determined in 53 (55%) of the 97 plasma samples tested. The subtypes in 2 plasma samples were unclassifiable. HIV-1 infections were classified as those due to the following group M subtypes: A (n = 4; 7%), B (n = 12; 22%), C (n = 8; 15%), F (n = 2; 4%), CRF01_AE-like (n = 7; 13%), CRF02_AG-like (n = 19; 34%), an intersubtype recombinant form G/A (n = 1; 2%), and unclassifiable viruses (n = 2; 4%). CONCLUSION: This study reveals infection with a broad variety of HIV-1 group M subtypes mostly in the immigrant population of New York City as well as how several non-B subtypes are being introduced into the United States.  相似文献   
44.
45.
IntroductionHuman sexuality is a multidimensional phenomenon related to several factors, such as self-esteem, awareness of sexual needs, and ability to communicate them to others.AimTo examine the sexual characteristics of patients seeking treatment for compulsive sexual behavior disorder (CSBD)—a clinical diagnosis recently included in the 11th edition of the International Classification of Diseases classification.MethodsWe have investigated the sexual characteristics of 72 Polish men seeking treatment for CSBD compared with 208 men from the Polish general population.Main Outcome MeasuresThe Multidimensional Sexual Questionnaire–PL was used to examine 12 sexual aspects of human sexuality. The severity of CSBD symptoms was assessed using Sexual Addiction Screening Test–PL, and the severity of problematic pornography use was measured by Brief Pornography Screener.ResultsResults show that CSBD patients (when compared with the general population) exhibit higher sexual anxiety, sexual depression, external sexual control, and fear of sexual relationship. Furthermore, CSBD severity is negatively related to sexual esteem, internal sexual control, sexual consciousness, sexual assertiveness, and sexual satisfaction.Clinical ImplicationsOur findings suggest that the impairment of the abovementioned dimensions warrant attention during clinical work and future studies on CSBD.Strengths & LimitationsThis study was limited to men, most of whom self-identified as heterosexual. Future research should include women and non-heterosexual identified individuals.ConclusionSexual esteem, consciousness, assertiveness, satisfaction and internal sexual control are commonly affected among CSBD individuals and should be properly addressed during the clinical interview and treatment intervention.Kowalewska E, Kraus SW, Lew-Starowicz M, et al. Which Dimensions of Human Sexuality Are Related to Compulsive Sexual Behavior Disorder (CSBD)? Study Using a Multidimensional Sexuality Questionnaire on a Sample of Polish Males. J Sex Med 2019;16:1264–1273.  相似文献   
46.
47.

Purposes

A satisfactory understanding of the clavicle development may be contributing to both the diagnosis of its congenital defects and prevention of perinatal damage to the shoulder girdle. This study was carried out to examine the transverse and sagittal diameters, cross-sectional area and volume of the two fused primary ossification centers of the clavicle.

Methods

Using the methods of CT, digital-image analysis and statistics, the size for two fused primary ossification centers of the clavicle in 42 spontaneously aborted human fetuses at ages of 18–30 weeks was studied.

Results

Without any male–female and right-left significant differences, the best fit growth models for two fused primary ossification centers of the clavicle were as follows: y = ?31.373 + 15.243 × ln(age) ± 1.424 (R 2 = 0.74) for transverse diameter, y = ?7.945 + 3.225 × ln(age) ± 0.262 (R 2 = 0.78), y = ?4.503 + 2.007 × ln(age) ± 0.218 (R 2 = 0.68), and y = ?4.860 + 2.117 × ln(age) ± 0.200 (R 2 = 0.73) for sagittal diameters of the lateral, middle and medial ends respectively, y = ?31.390 + 2.432 × age ± 4.599 (R 2 = 0.78) for cross-sectional area, and y = 28.161 + 0.00017 × (age)4 ± 15.357 (R 2 = 0.83) for volume.

Conclusions

With no sex and laterality differences, the fused primary ossification centers of the clavicle grow logarithmically in both transverse and sagittal diameters, linearly in cross-sectional area, and fourth-degree polynomially in volume. Our normative quantitative findings may be conducive in monitoring normal fetal growth and screening for inherited faults and anomalies of the clavicle in European human fetuses.
  相似文献   
48.
49.
Fetal ovarian cysts are the most frequent type of abdominal tumors in female fetuses with prenatal detection rate of more than 30%. The etiology of fetal ovarian cysts is unclear, but hormonal stimulation as well as presence of maternal diabetes, hypothyroidism, Rh iso-immune hemolytic disease and toxemia has been generally considered responsible for the disease. Complications of fetal ovarian cysts include compression of other viscera, cyst rupture, hemorrhage and, most frequently, ovarian torsion with consequent loss of the ovary. Management is controversial with several options described in the literature, including watchful expectancy, antenatal aspiration of simple cysts to prevent torsion and ovarian loss and finally, resection of all complex cysts in the neonatal period. To date, no case report has described recurrent complex cysts with rupture in the fetal period and recurrence of simple cyst in neonatal period. By presenting this case, we wanted to show that surgical intervention in case of prenatally diagnosed fetal ovarian cyst should be considered postnatally and only in symptomatic or complicated cases.  相似文献   
50.
The genetic risk factors for chronic obstructive pulmonary disease (COPD) are still largely unknown. To date, genome-wide association studies (GWASs) of limited size have identified several novel risk loci for COPD at CHRNA3/CHRNA5/IREB2, HHIP and FAM13A; additional loci may be identified through larger studies. We performed a GWAS using a total of 3499 cases and 1922 control subjects from four cohorts: the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); the Normative Aging Study (NAS) and National Emphysema Treatment Trial (NETT); Bergen, Norway (GenKOLS); and the COPDGene study. Genotyping was performed on Illumina platforms with additional markers imputed using 1000 Genomes data; results were summarized using fixed-effect meta-analysis. We identified a new genome-wide significant locus on chromosome 19q13 (rs7937, OR = 0.74, P = 2.9 × 10(-9)). Genotyping this single nucleotide polymorphism (SNP) and another nearby SNP in linkage disequilibrium (rs2604894) in 2859 subjects from the family-based International COPD Genetics Network study (ICGN) demonstrated supportive evidence for association for COPD (P = 0.28 and 0.11 for rs7937 and rs2604894), pre-bronchodilator FEV(1) (P = 0.08 and 0.04) and severe (GOLD 3&4) COPD (P = 0.09 and 0.017). This region includes RAB4B, EGLN2, MIA and CYP2A6, and has previously been identified in association with cigarette smoking behavior.  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