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   89910篇
  免费   8862篇
  国内免费   7299篇
耳鼻咽喉   657篇
儿科学   830篇
妇产科学   987篇
基础医学   10693篇
口腔科学   1598篇
临床医学   12984篇
内科学   13154篇
皮肤病学   723篇
神经病学   5307篇
特种医学   3170篇
外国民族医学   56篇
外科学   8335篇
综合类   15448篇
现状与发展   22篇
一般理论   13篇
预防医学   5820篇
眼科学   2975篇
药学   9254篇
  105篇
中国医学   5974篇
肿瘤学   7966篇
  2024年   481篇
  2023年   1573篇
  2022年   4313篇
  2021年   5196篇
  2020年   4041篇
  2019年   3249篇
  2018年   3456篇
  2017年   2901篇
  2016年   2851篇
  2015年   4302篇
  2014年   5281篇
  2013年   4465篇
  2012年   6560篇
  2011年   7602篇
  2010年   4564篇
  2009年   3580篇
  2008年   4582篇
  2007年   4444篇
  2006年   4622篇
  2005年   4648篇
  2004年   2737篇
  2003年   2660篇
  2002年   2220篇
  2001年   1935篇
  2000年   2058篇
  1999年   2155篇
  1998年   1442篇
  1997年   1367篇
  1996年   1099篇
  1995年   1016篇
  1994年   840篇
  1993年   533篇
  1992年   601篇
  1991年   509篇
  1990年   465篇
  1989年   420篇
  1988年   347篇
  1987年   296篇
  1986年   228篇
  1985年   178篇
  1984年   81篇
  1983年   50篇
  1982年   41篇
  1981年   36篇
  1980年   24篇
  1979年   21篇
  1964年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
BackgroundThe effect of caudal block (CB) on the incidence of urethroplasty complications in hypospadias repair remains controversial. The evidence is conflicting, and some confounding bias issues need to be addressed. We sought to study a more homogenous group of distal hypospadias patients undergoing primary tubularized incised plate (TIP) repair by a senior pediatric urology surgeon in the past 2 years to examine the relationship between urethroplasty complications and the use of CB.MethodsWe reviewed our database to identify consecutive patients who had undergone hypospadias repairs by a senior director surgeon at our Center between January 2018 and November 2020. To be eligible to participate in the study, patients had to meet the following inclusion criteria: (I) have distal hypospadias; (II) have undergone a primary TIP repair; and (III) have attended follow-up appointments for a minimum period of 6 months. The primary outcome was the development of urethroplasty complications during the follow-up period. The principal variable of interest was whether or not CB was used perioperatively. The patients were categorized into a CB group (general anesthesia combined with CB) or a control group (general anesthesia only). Other potential risk factors were analyzed, including patient age at operation, patient weight, glans width, and the length of the urethral plate defect.ResultsThirty (12.2%) of the distal patients developed postoperative surgical complications. The postoperative surgical complication rates were similar between the different anesthesia groups. Weight, the length of the urethral plate length, and glans width did not contribute to the risk. Age was the only independent risk factor for postoperative surgical complications, and the complication rates increased in older patients.ConclusionsOur data from consecutive TIP repairs in distal hypospadias patients indicated no association between the use of CB anesthesia and the postoperative urethroplasty complication rate. Patients who were older in age when they underwent surgery had a higher risk of complications.  相似文献   
132.

Although the carbendazim is widely used to manage spot blight in celery cultivation, information on residues identified is of interest. In this study, we examined the dissipation and residual amounts of carbendazim in celery and soil under different cultivation methods when using the suggested dose and ten times of that and the bioconcentration factor of carbendazim for celery. The results showed that when celery leaves were sprayed with the suggested dose, the half-lives in a celery field and greenhouse were 2.75 days and 3.29 days, respectively. When the soil matrix was sprayed with the recommended dose before cultivation, the half-lives of carbendazim residues were 16.86 days and 11.97 days. We also conducted a long-term dietary risk assessment using the corresponding criteria. The results showed that, in China, the use of carbendazim at a dose of 0.022 g/m2 is safer and more reasonable when the harvest interval is 28 days.

  相似文献   
133.
建立人微小病毒B19的PCR检测方法   总被引:1,自引:0,他引:1  
人微小病毒B19是微小病毒科中唯一能感染人的病毒。能够提供B19抗原的病毒体外培养系统尚未建成,因此限制了血清学实验的开发和普及。为此作者建立起B19病毒的PCR检测方法。设计引物在表达外壳蛋白VP1基因区,扩增长度为400bp。  相似文献   
134.
单片微机化微弱发光测量仪及其在肿瘤研究中的初步应用   总被引:2,自引:0,他引:2  
单片微机化微弱发光测量仪由中科院生物物理所和北京科龙生物医学技术开发公司研制成功。该仪器适用于肿瘤研究中生物医学样品的微弱发光的测量。测量样品的重复性优于0.8%,稳定性优于0.5%,线性相关系数达0.9997,不仅可以进行样品的发光强度测量,还可以进行动力学曲线的测量以及样品发射光谱的测量。光谱在400nm-750nm范围内。测量方式可选择手动、半自动和自动计时三种。测量结果表明,荷瘤裸鼠血液微  相似文献   
135.
呋喃唑酮厌恶疗法戒酒的初步报告   总被引:10,自引:1,他引:10  
对8例酒精依赖伴中毒男性患者,采用呋喃唑酮结合小量饮酒方法进行临床观察,因其产生不良躯体反应而达到厌恶戒酒目的。其成功率为87.5%。远期不良反应轻微。戒酒机制可能属厌恶条件反射的建立。  相似文献   
136.
本文介绍一种以386计算机为核心的心电心向量同步仪。阐述了仪器的工作原理、硬件组成、软件设计。  相似文献   
137.
Hippo pathway and its related genes are required for growth control in various somatic tissues. The mutations of Hippo pathway components lead to tissue overgrowth cell-autonomously. Surprisingly, when we generated germline mutant clones of Hippo-network genes such as fat, expanded, hippo, salvador, and warts, we did not observe any overgrowth of these mutant cells. Consistently, overexpression of the progrowth gene yorkie, which is normally inhibited by Hippo signaling, did not lead to germline overgrowth either. In contrast to previous studies in epithelial tissues, these tumor suppressor genes are dispensable in germline cells for their proliferation control. Furthermore, we demonstrate that expanded functions nonautonomously to regulate spermatogonial proliferation. It appears that expanded acts from the somatic support cells surrounding the germline to restrict spermatogonial amplification.  相似文献   
138.
BACKGROUNDS: Hemangiomas are highly prevalent in newborns and infants and can lead to severe complications. However, the pathogenesis of hemangiomas is still unknown. This study was designed to examine the potential of human monocytes to differentiate into hemangioma endothelial cells. METHODS: Purified monocytes from adult human peripheral blood were cultured under a conditional culture environment supplemented with basic fibroblast growth factor and vascular endothelial growth factor. Cells cultured for 2 weeks were subjected to histological and immunochemical examinations in order to determine the expression of specific markers for hemangioma endothelial cells. RESULTS: Monocytes cultured for 2 weeks in angiogenic medium expressed human erythrocyte-type glucose transporter protein, FcgammaRII, and several other endothelial markers, all of which are deemed specific markers for hemangioma endothelial cells. However, neither CD133 nor alpha smooth muscle actin was detected in our monocyte culture. CONCLUSION: Our data suggested that monocytes are capable of differentiating into hemangioma endothelial cells under the angiogenic stimulation from microenvironment of proliferative hemangioma.  相似文献   
139.
Exact BPF and FBP algorithms for nonstandard saddle curves   总被引:1,自引:0,他引:1  
Yu H  Zhao S  Ye Y  Wang G 《Medical physics》2005,32(11):3305-3312
A hot topic in cone-beam CT research is exact cone-beam reconstruction from a general scanning trajectory. Particularly, a nonstandard saddle curve attracts attention, as this construct allows the continuous periodic scanning of a volume-of-interest (VOI). Here we evaluate two algorithms for reconstruction from data collected along a nonstandard saddle curve, which are in the filtered backprojection (FBP) and backprojection filtration (BPF) formats, respectively. Both the algorithms are implemented in a chord-based coordinate system. Then, a rebinning procedure is utilized to transform the reconstructed results into the natural coordinate system. The simulation results demonstrate that the FBP algorithm produces better image quality than the BPF algorithm, while both the algorithms exhibit similar noise characteristics.  相似文献   
140.
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