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   19215篇
  免费   1607篇
  国内免费   522篇
耳鼻咽喉   157篇
儿科学   143篇
妇产科学   606篇
基础医学   1547篇
口腔科学   1011篇
临床医学   2769篇
内科学   1381篇
皮肤病学   105篇
神经病学   440篇
特种医学   966篇
外科学   1539篇
综合类   3379篇
一般理论   5篇
预防医学   2498篇
眼科学   162篇
药学   2194篇
  71篇
中国医学   1816篇
肿瘤学   555篇
  2024年   138篇
  2023年   540篇
  2022年   1115篇
  2021年   1309篇
  2020年   1182篇
  2019年   830篇
  2018年   856篇
  2017年   860篇
  2016年   836篇
  2015年   759篇
  2014年   1484篇
  2013年   1696篇
  2012年   1348篇
  2011年   1339篇
  2010年   1004篇
  2009年   850篇
  2008年   875篇
  2007年   765篇
  2006年   710篇
  2005年   536篇
  2004年   442篇
  2003年   332篇
  2002年   229篇
  2001年   216篇
  2000年   170篇
  1999年   131篇
  1998年   98篇
  1997年   96篇
  1996年   98篇
  1995年   90篇
  1994年   89篇
  1993年   62篇
  1992年   50篇
  1991年   34篇
  1990年   28篇
  1989年   21篇
  1988年   23篇
  1987年   18篇
  1986年   16篇
  1985年   7篇
  1984年   10篇
  1983年   10篇
  1982年   12篇
  1981年   6篇
  1980年   6篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1976年   3篇
  1973年   2篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
91.
Summary Three-dimensional arteriography was used to analyse the arterial supply of the great and second toes of 100 cadaveric feet down to the microsurgical level. This information will aid in successful composite tissue transfers of these toes to the hand. The arterial blood supply of the great toe came principally from the first dorsal metatarsal a. (78%) and the first plantar metatarsal a. (22%), and secondarily from the medial tarsal aa. and the three terminal branches of the medial plantar a. For the second toe, the first dorsal metatarsal a. (78%) and the first plantar metatarsal a. (22%) supplied blood from the medial side, and the second dorsal metatarsal a. (78%) and the second plantar metatarsal a. (22%) supplied blood from the lateral side. Seven arterial patterns were found in the interdigital web space. The socalled general pattern was seen in the first web space in 65% of the feet examined. In the second web space it was found in 85%. The first intermetatarsal space sometimes contained a large artery arising directly from the dorsalis pedis or first proximal perforating a. as well as the first dorsal and first plantar metatarsal arteries. In this space, arterial patterns were classified into 4 types and 9 subtypes based on the origins and proximal courses of these arteries. The so-called standard pattern was found in only 19% of the feet, while an arterial pattern with a common proximal trunk on the plantar side for the first dorsal and first plantar metatarsal aa. was found most frequently (46%). In the second intermetatarsal space the second dorsal metatarsal a. was usually located on the dorsum.
Les artères de l'hallux et du deuxième orteil. Analyse tridimensionnelle de cent pieds de cadavres
Résumé L'artériographie en trois dimensions a été utilisée pour analyser la vascularisation artérielle de l'hallux et du deuxième orteil de cent pieds de cadavres jusqu'au niveau microchirurgical. Ces renseignements aideront au succès des transferts de tissus composites de ces orteils vers la main. La vascularisation artérielle de l'hallux vient principalement de la première artère métatarsienne dorsale (78 %) et de la première artère métatarsienne plantaire (22 %) et secondairement des artères tarsiennes médiales et des trois branches terminales de l'artère plantaire médiale. Pour le deuxième orteil, la première artère métatarsienne dorsale (78 %) et la première artère métatarsienne plantaire (22 %) vascularisent le versant médial, la deuxième artère métatarsienne dorsale (78 %) et la deuxième artère métatarsienne plantaire (22 %) vascularisent le versant latéral. Sept dispositions artérielles ont été trouvées dans la commissure interdigitale. Une disposition dénommée commune a été vue dans la premiere commissure sur 65 % des pieds examinés, dans la deuxième commissure dans 85 % des cas. Le premier espace intermétatarsien contient parfois une volumineuse artère, naissant directement de l'artère dorsale du pied ou de la première artère perforante proximale, mais aussi des premières artères métatarsiennes dorsale ou plantaire. Dans cet espace, les dispositions artérielles sont classées en 4 types et 9 sous-types, basés sur l'origine et le trajet proximal de ces artères. La disposition standard a été trouvée seulement sur 19 % des pieds, alors qu'une disposition comprenant un tronc proximal commun situé sur le versant plantaire, fournissant les premières artères métatarsiennes dorsale et plantaire, a été trouvée plus fréquemment (46 %). Dans le deuxième espace intermétatarsien, la deuxième artère métatarsienne dorsale était habituellement située sur le versant dorsal.
  相似文献   
92.
Lack of efficient culture systems for hepatitis C virus (HCV) has been a major obstacle in HCV research. Human liver cells grown in a three-dimensional radial-flow bioreactor were successfully infected following inoculation with plasma from an HCV carrier. Subsequent detection of increased HCV RNA suggested viral replication. Furthermore, transfection of HCV RNA transcribed from full-length cDNA also resulted in the production and release of HCV virions into supernatant. Infectivity was shown by successful secondary passage to a new culture. Introduction of mutations in RNA helicase and polymerase regions of HCV cDNA abolished virus replication, indicating that reverse genetics of this system is possible. The ability to replicate and detect the extracellular release of HCV might provide clues with regard to the persistent nature of HCV infection. It will also accelerate research into the pathogenicity of HCV, as well as the development of prophylactic agents and new therapy.  相似文献   
93.
Although there have been some reports that measured the size of mastoid pneumatization, only a few studies have reported the age-related variations in the mastoid air cell system using three-dimensional (3D) reconstruction techniques of computed tomography (CT) images. We performed a retrospective, cross-sectional study. A 3D reconstruction based on CT images was performed on 199 ears of 102 patients (age range 6–84 years) without otologic disease by a surface-rendering algorithm. The results showed that mastoid pneumatization continued to grow until the third decade. Thereafter, it declined slowly, and then rapidly after the seventh decade. No statistically significant difference was found between male and female or between right and left sides. There was a significant difference between the larger and smaller sides of individuals. The volume measurement technique based on the 3D reconstruction technique reported here is widely available, highly accurate and easy to perform.  相似文献   
94.
cDNA arrays are a powerful tool for the identification of differentially expressed genes in malignant tumors. We used this technique to study the gene expression profiles of anaplastic large cell lymphoma (ALCL) and Hodgkin's disease (HD). Gene expression of 11 lymphoma cell lines was analyzed covering 1176 cDNA sequences. Comparing these data to the expression profiles of B- and T-lymphocytes, we identified 27 genes that were deregulated in all cell lines or in a particular entity. For the establishment of gene expression profiles the 27 genes were assigned to four groups composed of genes deregulated in (i) all lymphoma cell lines, (ii) ALCL and HD, (iii) only HD, and (iv) ALCL exclusively. Our results indicate that ALCL and HD share the differential expression of at least five genes. In addition, both entities are characterized by the differentially deregulated expression of four genes in HD and seven genes in ALCL. Because the expression profiling was performed on cell lines, further studies are needed to clarify the biological significance of the differentially expressed genes.  相似文献   
95.
Impact of elective single embryo transfer on the twin pregnancy rate   总被引:9,自引:0,他引:9  
BACKGROUND: It is unclear how the implementation of elective single embryo transfer in clinical practice would affect clinical pregnancy and delivery rates and multiple birth rates. METHODS: This retrospective study analysed 1871 IVF/ICSI cycles carried out from 1997 to 2001 in the IVF programme of a single university infertility clinic. RESULTS: The number of elective single embryo transfers increased from 11 to 56%. At the same time the clinical pregnancy rate was relatively stable; mean 34.0% (range 28-42). The number of embryos per embryo transfer decreased from 1.8 to 1.3. The multiple pregnancy and delivery rates dropped markedly from 25 to 7.5% and from 25 to 5% respectively. CONCLUSIONS: An elective single embryo transfer programme can be adopted in daily practice that decreases the twinning rate to <10% and does not affect the overall pregnancy rate.  相似文献   
96.
目的: 探讨前列地尔脂微球(liposome prostaglandin E1,Lipo-PGE1) 不同用药时间和途径对肝脏血流灌注的作用机制。方法: 选取健康成年犬12只,经左小隐静脉注射Lipo-PGE11 μg/kg,速度均为0.05 μg·kg-1·min-1。分别于0 min、5 min、15 min、30 min后行肝脏CT灌注成像(computed tomography perfusion imaging,CTPI)扫描,计算肝动脉灌注量(hepatic arterial perfusion,HAP)、门静脉灌注量 (portal vein perfusion,PVP)、总肝灌注量(total liver perfusion,TLP),对照分析不同时间Lipo-PGE1对肝脏血流灌注的影响。选取健康成年犬24只,随机平均分成4组:对照组、外周静脉用药组、肝动脉组、肠系膜上动脉组。Lipo-PGE1的用药量均为1 μg/kg、用药速度均为0.05 μg·kg-1·min-1,0.9%生理盐水用量为20 mL。各组用药5 min后行肝脏CTPI,比较分析不同途径给予Lipo-PGE1对肝脏血流灌注的影响。结果: 经外周静脉注射Lipo-PGE10 min、5 min、15 min、30 min后CTPI测量的HAP(mL·min-1·mL-1)分别为:0.22 ±0.65、0.24±0.65、0.22±0.69、0.22±0.06;PVP (mL·min-1·mL-1):1.22±0.40、1.88±0.59、1.55±0.55、1.29 ±0.57;TLP (mL·min-1·mL-1)分别为:1.44±0.42、2.12±0.61、1.77±0.56、1.51±0.58。方差分析显示HAP组间比较无显著差异(F=0.249,P>0.05),而PVP、TLP组间比较有显著差异(F=3.812,P<0.05)、(F=3.805,P<0.05)。5 min组PVP、TLP增加最为显著,15 min、30 min时两者仍处于高值水平。对照组和外周静脉组、肝动脉组、肠系膜上动脉组的HAP (mL·min-1·mL-1)分别为:0.22±0.06、0.24±0.06、0.31±0.07、0.26±0.05;PVP (mL·min-1·mL-1)分别为1.28±0.38、2.33±0.41、2.37±0.55、2.83±0.94;TLP (mL·min-1·mL-1)分别为:1.50±0.40、2.57±0.42、2.67±0.58、3.09±0.94。方差分析显示HAP组间比较无显著差异(F=2.248,P>0.05),而PVP、TLP组间比较有显著差异(F=6.892,P<0.01)、(F=7.802,P<0.01)。经肠系膜上动脉给药较其它途径给药PVP、TLP增加趋势更为显著。结论: Lipo-PGE1能显著增强肝脏血流灌注,且主要影响门静脉灌注分量,介入技术可为快速改善肝血流灌注提供有效途径。  相似文献   
97.
Traditionally, radiology has been conceived as a support department providing patient scanning services to the other clinical departments in a hospital. However, recent advancements in networking technology and related information systems such as picture archiving and communication system (PACS) and radiology information system (RIS) provide new opportunities for inventing different types of diagnostic imaging businesses such as teleradiology. In this article, we examined the business processes of currently operating imaging centers and proposed a prototype of an information system that can facilitate their workflows in a more efficient way. The principal component of our proposed system is a report management module built on extensible markup language (XML) technologies that allows much flexibility and convenience for both imaging technicians and radiologists.  相似文献   
98.
99.
A form of three-dimensional X-ray imaging, called Object 3-D, is introduced, where the relevant subject material is represented as discrete ‘objects’. The surface of each such object is derived accurately from the projections of its outline, and of its other discontinuities, in about ten conventional X-ray views, distributed in solid angle. This technique is suitable for many applications, and permits dramatic savings in radiation exposure and in data acquisition and manipulation. It is well matched to user-friendly interactive displays.  相似文献   
100.
The legislative background and current responsibilities of the new National Center for Health Care Technology (NCHCT) are discussed. The NCHCT's charge is to consider the stage of development, the actual or potential risks, costs and rate of use of health care technology. The role of Government in supporting new technologies, stimulating innovation and encouraging application of research products is considered. These issues are discussed in the context of the uncertainty inherent in planning and the formulation of public policy.  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