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   5398篇
  免费   316篇
  国内免费   308篇
耳鼻咽喉   28篇
儿科学   9篇
妇产科学   19篇
基础医学   670篇
口腔科学   1278篇
临床医学   455篇
内科学   1132篇
皮肤病学   38篇
神经病学   69篇
特种医学   117篇
外科学   295篇
综合类   559篇
预防医学   365篇
眼科学   48篇
药学   414篇
  1篇
中国医学   492篇
肿瘤学   33篇
  2024年   23篇
  2023年   137篇
  2022年   530篇
  2021年   626篇
  2020年   185篇
  2019年   139篇
  2018年   137篇
  2017年   109篇
  2016年   127篇
  2015年   181篇
  2014年   437篇
  2013年   610篇
  2012年   254篇
  2011年   272篇
  2010年   178篇
  2009年   186篇
  2008年   209篇
  2007年   191篇
  2006年   165篇
  2005年   161篇
  2004年   128篇
  2003年   137篇
  2002年   93篇
  2001年   90篇
  2000年   74篇
  1999年   62篇
  1998年   56篇
  1997年   43篇
  1996年   33篇
  1995年   24篇
  1994年   36篇
  1993年   26篇
  1992年   50篇
  1991年   29篇
  1990年   27篇
  1989年   25篇
  1988年   17篇
  1987年   25篇
  1986年   26篇
  1985年   35篇
  1984年   21篇
  1983年   18篇
  1982年   22篇
  1981年   7篇
  1980年   14篇
  1979年   5篇
  1978年   9篇
  1977年   11篇
  1976年   9篇
  1975年   8篇
排序方式: 共有6022条查询结果,搜索用时 15 毫秒
1.
Particle size analysis in the pharmaceutical industry has long been a source of debate regarding how best to define measurement accuracy; the degree to which the result of a measurement or calculation conforms to the true value. Defining a “true” value for the size of a particle can be challenging as the output of its measurement will differ because of variations in measurement approaches, instrumental differences and calculation methods. Consequently, for “real” particles, a universal “true” value does not exist and accuracy is therefore not a definable characteristic. Accordingly, precision is then a measure of the ability to reproducibly achieve a measurement of unknown relevance.This article proposes, in place of accuracy, a means to define the “appropriateness” of a measurement in line with the critical quality attributes (CQA) of the material being characterized. The decision as to whether the measurement is correct should involve a link to the CQA; that is, correlation should be demonstrated, without which the measured particle size cannot be defined as a critical material attribute.Correspondingly, methods should also be able to provide sufficient precision to demonstrate discrimination relating to variation in the CQA. The benefits and challenges of this approach are discussed.  相似文献   
2.
3.
具有A-π-D电子结构的苯胺衍生物掺杂的玻璃态高聚物PMMA的有机薄膜经极化取向后显示很强的二次非线性光学性能,其取向弛豫是实用化的一个有待解决的重要问题。木文通过几种苯胺衍生物以不同百分比与PMMA掺杂,用紫外-可见吸收光谱、二次谐波强度测量、动态力学粘弹谱等方法进行了取向弛豫的机理研究,结果表明分子尺寸和形状以及偶极矩的大小对取向弛豫有显著影响。  相似文献   
4.
以制备晶形、粒度、轴比等满足高性能磁粉要求的铁黄为目标,研究了碱法超细α-FeOOH合成的工艺配方和工艺条件对粒子性能的影响,包括碱比、气量、转速、Fe(OH)_2结晶条件、熟化时间等工艺参数的影响规律。重复稳定地制备出三类超微粒α-FeOOH粒子,其粒度分别为0.18、0.28、0.39μm,分布均匀,无枝叉。  相似文献   
5.
医用低值材料采供管理的探讨   总被引:4,自引:2,他引:2  
医疗消耗材料是医疗工作开展的基础,本文从医用低值消耗材料的计划制定、材料采购、库房库存结构、材料供应、成本核算等多方面探讨了如何对医疗消耗材料进行科学管理,这对医院的医疗发展和管理建设有着重要意义。  相似文献   
6.
Industrial back belts and low back pain: Mechanisms and outcomes   总被引:1,自引:0,他引:1  
The recent increased utilization of industrial back belts as personal protective equipment in the workplace has generated considerable controversy among occupational health and safety professionals in the United States. The purpose of this article is to review the literature regarding proposed mechanisms of action of these devices and studies related to outcome of belt utilization in the prevention of low back pain and disability in the workplace. At the present time, neither the suspected mechanisms of action nor the efficacy of these devices in the primary, secondary, and tertiary prevention of work-related low back pain has been adequately demonstrated in clinical trials. As a result, generally accepted guidelines regarding the safe use of belts in the occupational setting have not been established. Based on this review it is recommended that further well-controlled, prospective, randomized clinical trials are necessary to evaluate the effectiveness of these devices as personal protective equipment. During the interim, the decision to prescribe belts to employees in the workplace should be at the discretion of an adequately trained occupational health care provider. These devices should not be provided as an alternative to appropriate administrative and/or engineering controls.  相似文献   
7.
本文主要研究了无机玻璃纤维增强聚甲基丙烯酸甲酯(PMMA)/羟基磷灰石(HA)复合材料的制备及相关的性能测试,证明此复合材料性能稳定、物理机械强度高以及工艺简单,有良好的应用前景。  相似文献   
8.
In this paper an uncomplicated method for the simultaneous detection and semiquantitation of 11 of the 12 commonly studied antinuclear antibodies (ANA) in a single run is described. This new application of checkerboard immunoblotting (CBIB) is based upon available technology and employs purified antigens which can be either purchased or produced in-house. CBIB requires no electronic instrument, can be formatted to meet the needs of the user, is rapidly performed, and has acceptable labor and materials costs. Data on the use of the method to examine available reference antisera is presented. CBIB has also proven practical for the clinical study of 18 sera, at two dilutions per membrane, for each set of specific antinuclear antibodies, also at two or more dilutions.  相似文献   
9.
颌面赝复材料研究进展   总被引:5,自引:0,他引:5  
综述了目前口腔颌面赝复材料种类、性能要求及各种颌面赝复材料的组成、性能和应用过程,探讨了各种颌面赝复材料的优势及不足,指出目前临床应用的颌面赝复材料以硅橡胶类为主,其中又以中温硫化硅橡胶和室温硫化硅橡胶综合性能较好,应用最为广泛。  相似文献   
10.
Diagnosis of fetal rubella infection by nucleic acid hybridization   总被引:4,自引:0,他引:4  
The efficacy of nucleic acid hybridization for the diagnosis of rubella infection in experimental and clinical materials was compared with immunoblot and virus isolation techniques. Our results showed that nucleic acid hybridization is specific and rapid but gives false-negative results when compared with conventional virus isolation in some experimental although not in clinical materials so far examined. For this reason, a failure to demonstrate rubella virus in fetal specimens by this method alone cannot yet be taken as a sole criterion for ruling out fetal rubella infection.  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