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   45351篇
  免费   5699篇
  国内免费   846篇
耳鼻咽喉   165篇
儿科学   1370篇
妇产科学   1047篇
基础医学   2858篇
口腔科学   1212篇
临床医学   5465篇
内科学   9885篇
皮肤病学   448篇
神经病学   3083篇
特种医学   1063篇
外国民族医学   1篇
外科学   4395篇
综合类   4160篇
现状与发展   8篇
一般理论   9篇
预防医学   8674篇
眼科学   648篇
药学   3382篇
  26篇
中国医学   330篇
肿瘤学   3667篇
  2024年   102篇
  2023年   1151篇
  2022年   1357篇
  2021年   2785篇
  2020年   2680篇
  2019年   2496篇
  2018年   2427篇
  2017年   2235篇
  2016年   2235篇
  2015年   2046篇
  2014年   3536篇
  2013年   4308篇
  2012年   2550篇
  2011年   2804篇
  2010年   2100篇
  2009年   2078篇
  2008年   2113篇
  2007年   1909篇
  2006年   1685篇
  2005年   1474篇
  2004年   1188篇
  2003年   980篇
  2002年   824篇
  2001年   764篇
  2000年   590篇
  1999年   473篇
  1998年   443篇
  1997年   376篇
  1996年   302篇
  1995年   284篇
  1994年   235篇
  1993年   237篇
  1992年   177篇
  1991年   146篇
  1990年   120篇
  1989年   104篇
  1988年   92篇
  1987年   80篇
  1986年   62篇
  1985年   84篇
  1984年   67篇
  1983年   25篇
  1982年   45篇
  1981年   31篇
  1980年   28篇
  1979年   19篇
  1978年   10篇
  1977年   13篇
  1976年   9篇
  1974年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
《Human immunology》2020,81(9):550-552
We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) alleles by PCR-SSP based typing in 144 Mexicans from the state of Guerrero to obtain information regarding allelic and haplotypic frequencies. We find that the ten most frequent haplotypes in the state of Guerrero include eight Native American and two European haplotypes. Admixture estimates revealed that the main genetic components in the state of Guerrero are Native American (61.36 ± 2.69% by ML; 54.17% of Native American haplotypes) and European (35.01 ± 4.59% by ML; 32.29% of European haplotypes), and a relatively low African genetic component (3.63 ± 2.38% by ML; 5.90% of African haplotypes).  相似文献   
42.
ABSTRACT

Objectives: The present study investigated the relationships of enculturation and depressive symptoms with health risk behavior engagement in Mexican-American college students and examined how these relationships differed by gender. Previous research has noted consistent gender differences in health risk behavior (e.g. alcohol use, substance use, and risky sexual behavior) among Latina/os, and emphasized the role of U.S. acculturation in this difference. Research examining the role of heritage cultural retention (i.e. enculturation), and including the added influence of mental health variables, such as depressive symptoms, is currently lacking. This study sought to address this gap.

Design: A large sample (N?=?677) of Mexican-American college students from four universities (located in New York, California, Florida, and Texas) completed an online questionnaire assessing health risk behaviors and corresponding variables.

Results: We found that males who endorsed more behavioral enculturation and depressive symptoms were more likely to engage in health risk behavior than all others in the sample. Contrary to previous literature, no relationship was found between behavioral enculturation and health risk behavior in females.

Conclusion: The current study found behavioral enculturation to be associated with depressive symptoms, and in turn with health risk behaviors among the males in our sample. Additional research will be needed to identify the mechanism underlying the relationship between enculturation and depressive symptoms as well as between depressive symptoms and risky behavior.  相似文献   
43.
44.
Several tools to facilitate the risk assessment and management of manufactured nanomaterials (MN) have been developed. Most of them require input data on physicochemical properties, toxicity and scenario-specific exposure information. However, such data are yet not readily available, and tools that can handle data gaps in a structured way to ensure transparent risk analysis for industrial and regulatory decision making are needed. This paper proposes such a quantitative risk prioritisation tool, based on a multi-criteria decision analysis algorithm, which combines advanced exposure and dose-response modelling to calculate margins of exposure (MoE) for a number of MN in order to rank their occupational risks. We demonstrated the tool in a number of workplace exposure scenarios (ES) involving the production and handling of nanoscale titanium dioxide, zinc oxide (ZnO), silver and multi-walled carbon nanotubes. The results of this application demonstrated that bag/bin filling, manual un/loading and dumping of large amounts of dry powders led to high emissions, which resulted in high risk associated with these ES. The ZnO MN revealed considerable hazard potential in vivo, which significantly influenced the risk prioritisation results. In order to study how variations in the input data affect our results, we performed probabilistic Monte Carlo sensitivity/uncertainty analysis, which demonstrated that the performance of the proposed model is stable against changes in the exposure and hazard input variables.  相似文献   
45.
46.
目的:分析对一代表皮生长因子受体酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitors,EGFR-TKIs)原发耐药的EGFR突变肺腺癌患者的临床特征,为预测肺腺癌患者是否对一代EGFR-TKIs原发耐药提供依据。方法:收集2014年01月至2019年04月于本院住院,一线使用一代EGFR-TKIs且随访时间超过6个月的EGFR敏感突变(19Del/21L858R)肺腺癌患者,根据疗效纳入原发性耐药组(NR=40)和敏感组(NS=237),比较两组患者的临床、影像特征及实验室指标之间的差异,分析对一代EGFR-TKIs原发耐药的危险因素。结果:EGFR敏感突变患者的原发性耐药发生率为14.4%。原发性耐药组与敏感组患者相比,二者在吸烟指数(P=0.004)及淋巴结转移(P=0.03)的差异有统计学意义。血清神经元特异性烯醇化酶(neuron specific enolase,NSE)≥10.725 ng/mL、肿瘤直径≥3.55 cm的患者更易对一代EGFR-TKIs耐药(P<0.05),各因素AUC值分别为0.615、0.716。联合NSE+肿瘤直径两项指标时AUC为0.735(95%CI:0.665~0.804),联合NSE+肿瘤直径+吸烟指数三项指标时AUC为0.751(95%CI:0.679~0.822),均优于单项指标。多因素Logistics回归分析证实,血清NSE浓度、肿瘤直径及吸烟指数是预测EGFR敏感突变患者对一代EGFR-TKI原发耐药的独立影响因素(P<0.05)。结论:吸烟指数≥400、病灶直径≥3.55 cm、血清NSE浓度≥10.725 ng/mL的患者更易对一代EGFR-TKIs原发耐药。单因素对预测EGFR突变患者是否对一代EGFR-TKIs原发耐药准确性较低,综合上述三项指标预测效果更好。  相似文献   
47.
48.
49.
Worldwide, researchers routinely study children indirectly through adults who act as proxies for such children. The call for researchers to rather study children directly and adopt less intrusive child-friendly methodologies has become louder. The draw-and-write technique is regarded as a less intrusive child-friendly method of collecting data that can be used for this purpose. This paper reports the findings of a qualitative study that sought to establish the feasibility of the draw-and-write technique in exploring the resilience of children orphaned by AIDS. This study involved a convenience sample of 23 IsiXhosa-speaking orphaned children aged from 13 to 17. The participants were in grades 6 to 10 and they resided in two child and youth care centres in the Eastern Cape province of South Africa. As part of the draw-and-write technique the participants were asked to make drawings of what enabled them to cope with their lives and to write short narratives in which they explained their drawings. Inductive content analysis was used to analyse the data and this process yielded two main themes, namely: personal protective resources and socio-ecological protective resources. The findings show that complex combinations of personal and socio-ecological resilience resources enabled the resilience of the orphaned children. The findings challenge researchers not to be oblivious to alternative child-friendly methods of research such as the draw-and-write technique when young people are the unit of analysis. The findings of this study have implications for research as well as practice in the field of education and psychology.  相似文献   
50.
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