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   271991篇
  免费   24538篇
  国内免费   19440篇
耳鼻咽喉   2067篇
儿科学   2331篇
妇产科学   3022篇
基础医学   33394篇
口腔科学   4341篇
临床医学   38849篇
内科学   39318篇
皮肤病学   2439篇
神经病学   15397篇
特种医学   9655篇
外国民族医学   198篇
外科学   25971篇
综合类   44486篇
现状与发展   74篇
一般理论   27篇
预防医学   16079篇
眼科学   8363篇
药学   28543篇
  383篇
中国医学   16030篇
肿瘤学   25002篇
  2025年   88篇
  2024年   3959篇
  2023年   5927篇
  2022年   11784篇
  2021年   14358篇
  2020年   11520篇
  2019年   9956篇
  2018年   9740篇
  2017年   8654篇
  2016年   8221篇
  2015年   12237篇
  2014年   15009篇
  2013年   12553篇
  2012年   18779篇
  2011年   21529篇
  2010年   13028篇
  2009年   10064篇
  2008年   13334篇
  2007年   13362篇
  2006年   13596篇
  2005年   13848篇
  2004年   8200篇
  2003年   7602篇
  2002年   6374篇
  2001年   5695篇
  2000年   6423篇
  1999年   7171篇
  1998年   4736篇
  1997年   4752篇
  1996年   3680篇
  1995年   3514篇
  1994年   2898篇
  1993年   1963篇
  1992年   2213篇
  1991年   1842篇
  1990年   1566篇
  1989年   1333篇
  1988年   1133篇
  1987年   990篇
  1986年   748篇
  1985年   608篇
  1984年   349篇
  1983年   214篇
  1982年   115篇
  1981年   126篇
  1980年   85篇
  1979年   91篇
  1965年   1篇
  1962年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
吴立克  张茁  毕齐  王晓娟 《北京医学》2006,28(11):670-672
目的 通过测定大鼠局灶性脑缺血-再灌流后不同时点脑组织中髓过氧化物酶(MPO)和神经元特异性烯醇化酶(NSE)活性的变化,探讨炎症反应与脑缺血损伤的关系.方法 用线栓法制备大鼠左侧大脑中动脉缺血-再灌流模型,检测缺血3h再灌流后6h、12h、24h、48h、72h和7d脑组织中MPO和NSE活性、脑梗死体积的变化.结果 缺血组脑组织中NSE和MPO活性升高,再灌流后48h的NSE为(5.44±0.95)ng/ml,MPO为4.49±0.22;72h分别为(5.36±0.65)ng/l和5.96±0.19,升高最为明显.脑梗死体积随再灌流时间延长而增加,第7d梗死体积百分比为(39.18±0.63)%.局灶性缺血脑组织中MPO活性与组织损伤(NSE活性)间具有高度正相关性.结论 炎症反应是加重脑缺血损伤的重要因素.  相似文献   
22.
23.
24.
The objective of this study was to explore the association of sperm mitochondrial ND2 (MT-ND2) gene variants with total fertilization failure (TFF). A retrospective comparative study of 246 cases of fresh in vitro fertilization (IVF) cycles or half-intracytoplasmic sperm injection cycles in the Han Chinese population was performed from July 2011 to May 2017. A total of 59 cases undergoing TFF, and 187 control cases with normal fertilization (fertilization rates >50%) were included. The sperm mitochondrial genovariation was determined using nested sequencing. A total of 32 homoplasmic variants and 47 heteroplasmic variants of MT-ND2 gene were observed in this study. There were no significant differences in the frequencies of the 32 homoplasmic variants of MT-ND2 gene between the TFF and control groups. A total of 53 pair-wise comparisons were performed, and the general characteristics of the IVF failure and control subjects were adjusted in logistic models. Data suggested that there were no significant differences in the frequencies of point 4914, 5320, and 5426 heteroplasmic variants of MT-ND2 gene between the TFF and control groups. In addition, no significant difference was observed in the frequency of mtDNA haplogroup D or haplogroup G between the IVF failure group and the normal fertilization group. This study suggests that the MT-ND2 gene variants might not be associated with TFF.

Abbreviations: ATP: adenosine triphosphate; dNTP: deoxy-ribonucleoside triphosphate; FADH2: flavin adenine dinucleotide; FDR: false discovery rate; FSH: follicle-stimulating hormone; IVF: in vitro fertilization; LH: luteinizing hormone; MTATP6: mitochondrially encoded ATP synthase 6; MTCYB: mitochondrially encoded cytochrome b; mtDNA: mitochondrial DNA; MT-ND2: mitochondrial ND2; NADH: nicotinamide adenine dinucleotide; ND2: NADH dehydrogenase subunit 2; OXPHOS: oxidative phosphorylation; PCR: single nucleotide polymorphisms; SNPs: single nucleotide polymorphisms; TFF: total fertilization failure  相似文献   

25.
The transdermal delivery of 2 fluorescent probes with similar molecular weight but different lipophilicity, into and through the skin from 2 commercially available transdermal bases, pluronic lecithin organogel, and Lipoderm® has been evaluated. First, in vitro penetration of fluorescein sodium and fluorescein (free acid) through porcine skin was evaluated. Retention and depth distribution profiles in skin were obtained by tape stripping and then followed by optical sectioning using multiphoton microscopy. The results showed that Lipoderm® led to an enhanced penetration of the hydrophilic compound, fluorescein sodium. For the lipophilic compound fluorescein (free acid), Lipoderm® performed similar to pluronic lecithin organogel base, where minimal drug was detected in either receptor phase. The skin retention and depth distribution results also showed that the hydrophilic fluorescein sodium had high skin retention with Lipoderm®, whereas fluorescein (free acid) had very low penetration and retention with increasing skin depth. Moreover, optical sectioning by multiphoton microscopy revealed an uneven distribution of probes across the skin in the x-y plane for both transdermal bases. This work showed that a hydrophilic compound has significantly increased skin penetration and retention when formulated with Lipoderm®, and the skin retention of the probe was the main determinant of its skin flux.  相似文献   
26.
Pharmacokinetics and tissue distribution of crotonoside   总被引:1,自引:0,他引:1  
1.?Crotonoside is a bioactive ingredient from Croton Herba with a strong antitumour activity. This study aimed to develop a highly sensitive and selective high-performance liquid chromatography (HPLC) method to quantify crotonoside in biological samples for pharmacokinetics and distribution studies.

2.?Protein precipitation by perchloric acid was used to separate crotonoside from the biological samples, and the recovery rates for crotonoside and the internal standard (luteoloside) were >80%. All calibration curves examining the crotonoside levels in plasma and tissues were linear (all correlation coefficients >?0.99).

3.?The response to crotonoside appeared to be dose disproportional to the maximum plasma concentration and the area under the time–concentration curve in plasma over the range of 12.5–50.0?mg/kg, and crotonoside was highly distributed in tissues after intravenous administration. The highest crotonoside level was detected in the liver (28.79?±?14.96?μg/g), whereas crotonoside was undetected in the brain.  相似文献   
27.
Aims: To investigate the value of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in a cohort of a community’s residents who were diagnosed as pre-diabetes, and to evaluate the association of VAT and SAT with insulin resistance.

Methods: This study was based on cross-sectional analysis of data from 107 adults. VAT and SAT were assessed by computed tomography. Insulin resistance was defined by homeostasis model assessment of insulin resistance >2.69. The relationship of VAT and SAT with insulin resistance were examined by linear regression. Logistic regression was used to analyze the association of VAT and SAT with insulin resistance.

Results: A total of 87 subjects had VAT ≥100?cm2. Thirty-six out of 107 (33.6%) subjects were detected to have insulin resistance, 71 were normal (66.4%), and all had insulin resistance with VAT ≥100?cm2. VAT (r?=?0.378, p?r?=?0.357, p?p?=?.003), but that of SAT was lost.

Conclusion: Pre-diabetic subjects with insulin resistance had elevated levels of VAT. VAT was more strongly associated with insulin resistance than SAT in Chinese subjects with pre-diabetes.  相似文献   
28.
29.
30.
摘 要 目的:明确我院三级抗菌药物(非限制使用级、限制使用级、特殊使用级)不合理使用情况的特点及差异,为临床规范使用抗菌药物提供理论依据。 方法:对我院736份出院病历的1 228条抗菌药物医嘱逐条进行合理性点评,并对三级抗菌药物医嘱不合理使用率、分布特点、类型进行比较。 结果:我院三级抗菌药物不合理使用率差异不全相同,以限制使用级为最高(25.0%),特殊使用级最低(9.8%),两者比较差异有统计学意义(P<0.01)。以头孢菌素为主的β内酰胺类抗菌药物的不合理医嘱最多。三级抗菌药物不合理用药类型差异有统计学意义(P<0.05)。“抗菌药物用法用量不适宜”、“围手术期预防性使用抗菌药物不合理”为非限制使用级及限制使用级抗菌药物的主要不合理医嘱构成。而“遴选抗菌药物不适宜”则为特殊使用级抗菌药物的主要不合理医嘱构成。结论:我院抗菌药物不合理使用情况较普遍。医院需针对各级抗菌药物使用中存在的主要问题加强抗菌药物的管理。  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