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   7356篇
  免费   487篇
  国内免费   23篇
耳鼻咽喉   125篇
儿科学   195篇
妇产科学   188篇
基础医学   943篇
口腔科学   368篇
临床医学   561篇
内科学   1835篇
皮肤病学   162篇
神经病学   512篇
特种医学   318篇
外科学   881篇
综合类   31篇
一般理论   4篇
预防医学   621篇
眼科学   102篇
药学   540篇
中国医学   42篇
肿瘤学   438篇
  2023年   49篇
  2022年   146篇
  2021年   246篇
  2020年   142篇
  2019年   230篇
  2018年   288篇
  2017年   180篇
  2016年   232篇
  2015年   256篇
  2014年   308篇
  2013年   361篇
  2012年   522篇
  2011年   524篇
  2010年   283篇
  2009年   260篇
  2008年   390篇
  2007年   382篇
  2006年   317篇
  2005年   290篇
  2004年   268篇
  2003年   256篇
  2002年   221篇
  2001年   190篇
  2000年   170篇
  1999年   176篇
  1998年   70篇
  1997年   64篇
  1996年   39篇
  1995年   39篇
  1994年   31篇
  1993年   27篇
  1992年   79篇
  1991年   82篇
  1990年   81篇
  1989年   40篇
  1988年   38篇
  1987年   58篇
  1986年   46篇
  1985年   57篇
  1984年   40篇
  1983年   33篇
  1980年   19篇
  1979年   38篇
  1978年   20篇
  1975年   24篇
  1974年   27篇
  1973年   26篇
  1972年   19篇
  1969年   23篇
  1968年   19篇
排序方式: 共有7866条查询结果,搜索用时 0 毫秒
51.
Food labels are the first information tool used by consumers in the purchase and consumption of food products. Food labeling is a tool that can influence the consumers’ perception of quality and, in turn, their food choice. This study characterizes and demonstrates the importance of labeling and the degree of consumers’ perception and literacy about food labels through the application of an online questionnaire. The results obtained, in a sample of n = 467, showed that Portuguese consumers have the habit of reading the label and recognizing its importance but do not understand all the information contained in the label. They have an easier time understanding the front-of-pack labeling systems, especially those presented through symbols/colors. Thus, it demonstrates the need for greater education and literacy in the areas of food and nutrition so that through the reading and interpretation of labels, consumers can make informed food choices.  相似文献   
52.
53.
54.
ObjectiveTo describe the seminiferous epithelium cycle (SEC) by tubular morphology method, and the acrosomal development of individualizing spermatids, and to explore the distinction of the stages between two generations of spermatids.MethodsTesticular fragments were fixed in Karnovsky, embedded in glycol methacrylate and examined under light microscopy and transmission electron microscopy. Sections in 3 μm thickness were stained with toluidine blue for the characterization of the stages of the SEC by the tubular morphology method, or submitted to the PAS reaction for the visualization of the acrosomal formation. Additional details on the acrosomal formation were observed under transmission electron microscopy.ResultsThrough the eight stages described by tubular morphology method, 10 steps of acrosomal formation were observed in the spermatid development, called acrosomal steps. As the spermatids were produced in stage V of the tubular morphology method, it was at this stage from which began the steps of acrosomal development.ConclusionsWe propose association of the acrosomal steps for the first time, with the different stages by tubular morphology method. This method presents an alternative to the existent Methods, allowing interspecific comparisons of the SEC, not only among different species of bats, but also among the other mammals.  相似文献   
55.
56.
ObjectiveTo examine the influence of a preventative training program (PTP) on sagittal plane kinematics during different landing tasks and vertical jump height (VJH) in males.DesignSix weeks prospective exercise intervention.ParticipantsFifteen male volleyball athletes (13 ± 0.7 years, 1.70 ± 0.12 m, 60 ± 12 kg).InterventionsPTP consisting of plyometric, balance and core stability exercises three times per week for six weeks. Bilateral vertical jumps with double leg (DL) and single leg (SL) landings were performed to measure the effects of training.Main outcome measurementsKinematics of the knee and hip before and after training and VJH attained during both tasks after training. The hypothesis was that the PTP would produce improvements in VJH, but would not generate great changes in biomechanical behavior.ResultsThe only change identified for the SL was the longest duration of landing, which represents the time spent from initial ground contact to maximum knee flexion, after training, while increased angular displacement of the knee was observed during DL. The training did not significantly alter the VJH in either the SL (difference: 2.7 cm) or the DL conditions (difference: 3.5 cm).ConclusionsDespite the PTP’s effectiveness in inducing some changes in kinematics, the changes were specific for each task, which highlights the importance of the specificity and individuality in selecting prevention injury exercises. Despite the absence of significant increases in the VJH, the absolute differences after training showed increases corroborating with the findings of statistically powerful studies that compared the results with control groups. The results suggest that short-term PTPs in low risk young male volleyball athletes may enhance performance and induce changes in some kinematic parameters.  相似文献   
57.
American cutaneous leishmaniasis (ACL) caused by Leishmania (Viannia) braziliensis is a neglected disease of humans in the New World that may also cause irreversible skin and eventually mucocutaneous lesions. This parasite can also infect dogs and represents a diagnostic challenge for veterinarians. Methods currently available for the diagnosis of ACL have a low sensitivity and may be time-consuming, representing a limit for treatment expedition of ACL. Quantitative real time PCR assays (qPCR) for the detection of L. (V.) braziliensis in canine blood samples were developed herein, and the detection limit and specificity of different molecular targets (kDNA and rDNA) evaluated. Of the protocols assessed, two qPCR assays, one targeting the kDNA and other the SSU rDNA of L. (V.) braziliensis, performed better, with detection limits of 100 fg and 10 pg, respectively. These assays were also used to test skin samples from humans with suspected ACL. The results indicate that the qPCR protocols developed represent an advance for the diagnosis of ACL in dogs and humans from this region, and provide a rapid and non-invasive diagnosis of the infection by L. (V.) braziliensis. Considering the quantitative nature of the assays, they will also be useful for monitoring treatment efficacy and preventing relapses in human patients in Brazil, although further studies are needed to critically evaluate the specificity of the qPCRs for their capacity to distinguish different Leishmania species and subspecies (represented by zymodemes) in other countries. Finally, molecular assays established may represent new tools for future basic and applied research focused on species identification, host–parasite associations, and infection dynamics in host and vector populations.  相似文献   
58.
59.
60.
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