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   40173篇
  免费   3023篇
  国内免费   441篇
耳鼻咽喉   445篇
儿科学   1141篇
妇产科学   748篇
基础医学   6091篇
口腔科学   658篇
临床医学   3689篇
内科学   8284篇
皮肤病学   908篇
神经病学   3207篇
特种医学   1574篇
外国民族医学   16篇
外科学   4878篇
综合类   1308篇
现状与发展   1篇
一般理论   2篇
预防医学   3121篇
眼科学   792篇
药学   3210篇
  6篇
中国医学   657篇
肿瘤学   2901篇
  2023年   322篇
  2022年   734篇
  2021年   1230篇
  2020年   773篇
  2019年   1014篇
  2018年   1311篇
  2017年   968篇
  2016年   1007篇
  2015年   1156篇
  2014年   1454篇
  2013年   2023篇
  2012年   2831篇
  2011年   2893篇
  2010年   1770篇
  2009年   1316篇
  2008年   1790篇
  2007年   1835篇
  2006年   1735篇
  2005年   1609篇
  2004年   1415篇
  2003年   1334篇
  2002年   1249篇
  2001年   1164篇
  2000年   1150篇
  1999年   1033篇
  1998年   382篇
  1997年   338篇
  1996年   304篇
  1995年   248篇
  1994年   243篇
  1993年   197篇
  1992年   543篇
  1991年   519篇
  1990年   501篇
  1989年   455篇
  1988年   484篇
  1987年   399篇
  1986年   386篇
  1985年   390篇
  1984年   288篇
  1983年   220篇
  1982年   154篇
  1981年   134篇
  1979年   235篇
  1978年   136篇
  1977年   144篇
  1976年   138篇
  1975年   122篇
  1974年   145篇
  1972年   141篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background: Craniometric variation in humans reflects different genetic and environmental influences. Long-term climatic adaptation is less likely to show an impact on size and shape variation in a small local area than at the global level.

Aim: The aim of this work was to assess the contribution of the particular environmental factors to body height and craniofacial variability in a small geographic area of Croatia.

Subjects and methods: A total of 632 subjects, aged 18–21, participated in the survey. Body height, head length, head breadth, head height, head circumference, cephalic index, morphological face height, face breadth, and facial index were analysed regarding geographic, climatic and dietary conditions in different regions of the country, and correlated with the specific climatic variables (cumulative multiyear sunshine duration, cumulative multiyear average precipitation, multiyear average air temperatures) and calcium concentrations in drinking water. Significant differences between groups classified according to geographic, climatic or dietary affiliation, and the impact of the environmental predictors on the variation in the investigated traits were assessed using multiple forward stepwise regression analyses.

Results: Higher body height measures in both sexes were significantly correlated with Mediterranean diet type. Mediterranean diet type also contributed to higher head length and head circumference measures in females. Cephalic index values correlated to geographic regions in both sexes, showing an increase from southern to eastern Croatia. In the same direction, head length significantly decreased in males and head breadth increased in females. Mediterranean climate was associated with higher and narrower faces in females. The analysis of the particular climatic variables did not reveal a significant influence on body height in either sex. Concurrently, climatic features influenced all craniofacial traits in females and only head length and facial index in males. Mediterranean climate, characterized by higher average sunshine duration, higher average precipitation and higher average air temperatures, was associated with longer, higher and narrower skulls, higher head circumference, lower cephalic index, and higher and narrower faces (lower facial index). Calcium concentrations in drinking water did not correlate significantly with any dependent variable.

Conclusion: A significant effect of environmental factors on body height and craniofacial variability was found in Croatian young adult population. This effect was more pronounced in females, revealing sex-specific craniofacial differentiation. However, the impact of environment was low and may explain only 1.0–7.32% variation of the investigated traits.  相似文献   
992.
The key method for therapies of various cancer types could be the molecular-targeted therapy, based on individual gene profile for each patient. One of the main procedures used for genetic testing is the real-time polymerase chain reaction (real-time PCR).  相似文献   
993.
Obesity is one of the highest preventable causes of morbidity and mortality in the developed world [1]. It has been well known for a long time that exposure to cannabis produces an increase of appetite (a phenomenon referred to as the ‘munchies’). This phenomenon led to an exploration of the role of the endocannabinoid system in the regulation of obesity and associated metabolic syndrome. This effort subsequently led to the development of a successful therapeutic approach for obesity that consisted of blocking the cannabinoid CB1 receptors using ligands such as Rimonabant in order to produce weight loss and improve metabolic profile [2]. Despite being efficacious, Rimonabant was associated with increased rates of depression and anxiety and therefore removed from the market. We recently discovered that the prevalence of obesity is paradoxically much lower in cannabis users as compared to non-users and that this difference is not accounted for by tobacco smoking status and is still present after adjusting for variables such as sex and age. Here, we propose that this effect is directly related to exposure to the Δ9-tetrahydrocannabinol (THC) present in cannabis smoke. We therefore propose the seemingly paradoxical hypothesis that THC or a THC/cannabidiol combination drug may produce weight loss and may be a useful therapeutic for the treatment of obesity and its complications.  相似文献   
994.
995.
AimTo explore the relationships between transient structural brain patterns on MRI at preterm and at term-equivalent age (TEA) as a predictor of general movements (GMs) and motor development at 1-year corrected age (CA) in very preterm infants.MethodsIn this prospective study, 30 very preterm infants (median = 28wks; 16 males) had structural magnetic resonance imaging (MRI) at preterm (median = 31wks + 6d) and at TEA (median = 40wks) and neuromotor assessments. The quality of GMs was assessed by Prechtl’s general movements assessment and a detailed analysis of the motor repertoire was performed by calculating a motor optimality score (MOS), both at term age and at 3 months post-term. Motor development at 1-year CA was evaluated with the Infant Motor Profile (IMP). Associations between qualitative MRI findings and neuromotor scores were investigated.ResultsAbnormal GMs and low motor performance at 1-year CA were associated with the poor visibility of transient structural pattern, that is with sagittal strata.InterpretationTransient structural MRI pattern, sagittal strata, at preterm age is related to the quality of GMs and later motor development in preterm infants. This transient fetal brain compartment may be considered as a component of neurobiological basis for early neuromotor behavior, as expressed by GMs.  相似文献   
996.
997.
998.
Our previous studies revealed a considerably high level of chromosomal polymorphism in wild silkmoths, Samia cynthia ssp. (Lepidoptera: Saturniidae). Geographical populations of this species complex differ in chromosome numbers and show derived sex chromosome systems including Z0/ZZ in S. cynthia ricini (2n?=?27/28; Vietnam), neo-Wneo-Z/neo-Zneo-Z in S. cynthia walkeri (2n?=?26/26; Sapporo, Hokkaido) and neo-WZ1Z2/Z1Z1Z2Z2 in S. cynthia subsp. indet. (2n?=?25/26; Nagano, Honshu). In this study, we collected specimens of S. cynthia pryeri in Japanese islands Kyushu, Shikoku and Honshu, with an ancestral-like karyotype of 2n?=?28 in both sexes and a WZ/ZZ sex chromosome system, except for one population, in which females have lost the W chromosome. However, the S. cynthia pryeri W chromosome showed a very unusual morphology: It was composed of a highly heterochromatic body, which remained condensed throughout the whole cell cycle and of a euchromatin-like “tail.” We examined molecular composition of the W and neo-W chromosomes in S. cynthia subspecies by comparative genomic hybridisation and fluorescence in situ hybridisation with W chromosome painting probes prepared from laser-microdissected W chromatin of S. cynthia pryeri. These methods revealed that the molecular composition of highly heterochromatic part of the S. cynthia pryeri W chromosome is very different and lacks homology in the genomes of other subspecies, whereas the euchromatin-like part of the W chromosome corresponds to a heterochromatic part of the neo-W chromosomes in S. cynthia walkeri and S. cynthia subsp. indet. Our findings suggest that the curious WZ system of S. cynthia pryeri may represent an ancestral state of the Samia species complex but do not exclude an alternative hypothesis of its derived origin.  相似文献   
999.
BackgroundThe purpose of this study was to evaluate the influence of both bundles of the anterior cruciate ligament (ACL) on knee stability, anterior–posterior translation (APT) and internal (IR) and external (ER) rotation in cadaveric knees using a computer navigation system.MethodsThe APT, IR, and ER of the knees were recorded in the intact condition, the anterolateral bundle (AM) or the posterolateral bundle (PL) deficit condition and in the ACL-deficient condition. The KT-1000 arthrometer was used for APT evaluation. The measurement of rotational movements was done using a rollimeter. All tests were performed at 30°, 60° and 90° of flexion.ResultsAt 30° of flexion: In the intact knee APT was 5.8 mm, IR 12.1°, ER 10.1°. After the AM was cut, the APT increased to 9.1 mm, IR to 13.9° and ER to 12.6°. After the PL was cut, the APT was 6.4 mm, IR 13.1° and ER 10.6°. After the AM and PL were cut, the APT was 10.8 mm, IR 15.7° and the ER was 12.9° on average.ConclusionsThe AM has a greater impact on the APT than the PL in all knee joint flexion angles. The PL does not resist the rotational stability more than the AM. The rotational stability is better controlled by both bundles of ACL as compared to one bundle of the ACL.Clinical RelevanceThis study acknowledges the fact that the both bundles of the ACL are importants for AP and rotational stability of the knee joint.  相似文献   
1000.
Genome-wide association studies (GWAS) have identified over 46 SNPs associated with human prostate cancer (PCa). Some studies have shown correlation of the nitric oxide synthase (NOS) NOS3 gene polymorphisms with the risk and/or progression of PCa. This study aimed to evaluate the association of NOS3 gene polymorphisms (−786T>C, −764A>G, −714G>T, −690C>T, −649G>A and 894G>T) with PCa risk and progression. 150 patients with PCa, 150 patients with BPH and 100 age-matched healthy controls were recruited in this study. Genotyping of promoter polymorphisms was performed by bi-directional DNA sequencing, and for 894G>T by RFLP analysis. There was no significant association between the alleles and genotypes of these genetic variants and PCa risk. For −786T>C polymorphism, we found that C allele is associated with absence of metastases, assuming dominant genetic model (P = 0.049; OR, 0.50; 95% CI, 0.25–1.00). It was found that, compared with NOS3 −690C>T variant CC genotype, CT and TT genotypes confer decreased risk of developing metastases (dominant model, P = 0.015, OR, 0.24; 95% CI, 0.07–0.88) and show association with low clinical tumour stage, compared with stages T3 and T4 (dominant model, P = 0.046, OR, 0.20; 95% CI, 0.04–1.02). Genetic variants −764A>G, −714G>T, −649G>A were not detected in our study group. There is evidence of an inverse correlation of the NOS3 894G>T minor allele with high serum PSA (>20 ng/ml) (dominant model, P = 0.013, OR, 0.37; 95% CI, 0.17–0.82). Our results suggest that NOS3 gene polymorphisms are genetic susceptibility factors for the progression of PCa and patient outcome.  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