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   9380篇
  免费   426篇
  国内免费   48篇
耳鼻咽喉   44篇
儿科学   241篇
妇产科学   112篇
基础医学   1501篇
口腔科学   340篇
临床医学   833篇
内科学   1646篇
皮肤病学   112篇
神经病学   788篇
特种医学   805篇
外科学   1257篇
综合类   29篇
一般理论   1篇
预防医学   438篇
眼科学   69篇
药学   777篇
中国医学   23篇
肿瘤学   838篇
  2023年   29篇
  2022年   60篇
  2021年   84篇
  2020年   58篇
  2019年   113篇
  2018年   131篇
  2017年   109篇
  2016年   134篇
  2015年   201篇
  2014年   268篇
  2013年   404篇
  2012年   561篇
  2011年   607篇
  2010年   357篇
  2009年   366篇
  2008年   523篇
  2007年   602篇
  2006年   576篇
  2005年   587篇
  2004年   553篇
  2003年   558篇
  2002年   612篇
  2001年   141篇
  2000年   105篇
  1999年   154篇
  1998年   145篇
  1997年   143篇
  1996年   123篇
  1995年   96篇
  1994年   92篇
  1993年   89篇
  1992年   65篇
  1991年   68篇
  1990年   64篇
  1989年   50篇
  1988年   52篇
  1987年   43篇
  1986年   53篇
  1985年   66篇
  1984年   61篇
  1983年   48篇
  1982年   53篇
  1981年   60篇
  1980年   50篇
  1979年   32篇
  1978年   40篇
  1977年   32篇
  1976年   35篇
  1975年   40篇
  1974年   30篇
排序方式: 共有9854条查询结果,搜索用时 0 毫秒
91.
Most nonsyndromic congenital heart malformations (CHMs) in humans are multifactorial in origin, although an increasing number of monogenic cases have been reported recently. We describe here four new families with presumed autosomal dominant inheritance of left ventricular outflow tract obstruction (LVOTO), consisting of hypoplastic left heart (HLHS) or left ventricle (HLV), aortic valve stenosis (AS) and bicuspid aortic valve (BAV), hypoplastic aortic arch (HAA), and coarctation of the aorta (CoA). LVOTO in these families shows a wide clinical spectrum with some family members having severe anomalies such as hypoplastic left heart, and others only minor anomalies such as mild aortic valve stenosis. This supports the suggestion that all anomalies of the LVOTO spectrum are developmentally related and can be caused by a single gene defect.  相似文献   
92.
93.
The natural transmission of microdeletions of the Y chromosome is occasionally reported in the literature. Here we describe the natural transmission of a partial AZFb deletion over three generations. PCR amplification of several sequence tagged site markers in the three AZF regions of the Y chromosome was carried out in a patient with oligoasthenoteratozoospermia, his father and his naturally conceived son. The deletion was confirmed by Southern blotting. The propositum, his father and his son showed a probably identical, partial deletion of the distal part of the AZFb region, involving sY130 and sY143. The deletion was confirmed by Southern blotting using the sY130 probe. Partial AZFb microdeletions can be associated with moderate oligozoospermia allowing natural conception and therefore natural transmission of this genetic anomaly. Further studies are needed to define the pathogenetic significance of microdeletions involving sY130 and sY143.  相似文献   
94.
Duchenne and Becker muscular dystrophy (DMD and BMD) are caused by mutations in the dystrophin gene. Large rearrangements in the gene are found in about two-thirds of DMD patients, with approximately 60% carrying deletions and 5-10% carrying duplications. Most of the remaining 30-35% of patients are expected to have small nucleotide substitutions, insertions, or deletions. To detect these subtle changes within the coding and splice site determining sequences of the dystrophin gene, we established a semiautomated denaturing gradient gel electrophoresis (DGGE) mutation scanning system. The DGGE scan covers the dystrophin gene with 95 amplicons, PCRed either individually or in a multiplex setup. PCR and pooling were performed semiautomatically, using a pipetting robot and 384-well plates, enabling concurrent amplification of DNA of four patients in one run. Amplification of individual fragments was performed using one PCR program. The products were pooled just before gel loading; DGGE requires only a single gel condition. Validation was performed using DNA samples harboring 39 known DMD variants, all of which could be readily detected. DGGE mutation scanning was applied to analyze 135 DMD/BMD patients and potential DMD carriers without large deletions or duplications. In DNA from 25 out of 44 DMD patients (57%) and from 5 out of 39 BMD patients (13%), we identified clear pathogenic changes. All mutations were different, with the exception of one DMD mutation, which occurred twice. In DNA from 10 out of 44 potential DMD carriers, including four obligate carriers, we detected causative changes, including one pathogenic change in every obligate carrier. In addition to these pathogenic changes, we detected 15 unique unclassified variants, i.e., changes for which a pathogenic nature is uncertain.  相似文献   
95.
96.
97.
98.
BACKGROUND: Personality structure obtained from the psychobiological Temperament and Character Inventory (TCI) was studied in relation to self-reported seasonal variations in mood and behavior measured by the Seasonal Pattern Assessment Questionnaire (SPAQ). METHODS: The subjects comprised 1761 adults (57.6% women) in the age range 35-85 years, enrolled in the Betula prospective random cohort study of Umea, Sweden. RESULTS: Personality profiles of subjects who reported the occurrence of a high degree of seasonal variation as such were associated with a combination of high self-transcendence (ST) and high persistence (PS), irrespective of the level of harm avoidance (HA). Subjects who reported feeling worst in winter were associated with high HA, irrespective of the levels of ST and PS. Also, subjects feeling worst in summer or experiencing overall problems with seasonal variation were associated with high HA in their personality profiles. Using the SPAQ criteria to define seasonal affective disorder (SAD) or subsyndromal SAD (S-SAD), subjects with these disorders often had combinations of high self-transcendence (ST) and high persistence (PS), but with different associations with HA. LIMITATIONS: No evaluations were made for SAD or subsyndromal SAD according to the DSM-IV or ICD 10 criteria. CONCLUSIONS: Our results relating SPAQ with TCI give support for a dual vulnerability hypothesis for seasonal depression proposed in the literature, where it is attributed to a combination of a seasonal factor and a depression factor. Examining the literature regarding the relationships between the different TCI scales and monoamine neurotransmitter functions, those relationships suggest that these two vulnerability factors for seasonal depression may be modulated by different neurotransmitter systems.  相似文献   
99.
Two monoclonal antibodies (mAbs) raised against the macrogamonts of Eimeria tenella identified antigens located in the wall-forming bodies of type I (WF I) and type II (WF II) by indirect immunofluorescence and by immunoelectron microscopy. With these mAbs, the involvement of both types of wall-forming body at the protein level in the formation of the inner and outer oocyst walls of E. tenella was shown by indirect immunofluorescence assay. On Western blots of pure macrogamont, mAb E1D8 against WF I reacted with a series of bands between 42 kDa and 105 kDa. In pure, unsporulated extract, this mAb recognized a complex of bands between 26 kDa and 153 kDa. mAb E2E5 against WF II, on Western blots of pure extract of macrogamonts, recognized an antigen of 51 kDa. Later in the development, after the formation of the inner oocyst wall, mAb E2E5 reacted with three polypeptide of 23, 25 and 30 kDa. Proteolytic processing may be forwarded as the mechanism regulating the distinct regulation protein involved in the oocyst wall.  相似文献   
100.
Summary Varying host reaction of the house fly, Musca domestica L., to parasitism by the braconid Aphaereta pallipes (Say) was chiefly correlated with the diet of the host. Some evidence was found that implicated the strain of the host, the rearing temperatures, the ages of the parasitoid and the host, and the site of oviposition. Though development of A. pallipes embryos was inhibited before they became encapsulated with melanin within the host, the presence of the parasitoid and (or) the effect of its paralyzing toxin that was injected into the host just before oviposition prevented normal larval, pupal, or adult development of the six house fly strains tested. A considerable increase of parasitoid survival occurred when M. domestica larvae were reared on a chemically defined diet.
Zusammenfassung Musca domestica L. reagierte unterschiedlich auf die Parasitierung durch die Braconide Aphaereta pallipes (Say). Die verschiedenen Reaktionen waren im wesentlichen mit der Art der Wirtsnahrung korreliert. Daneben finden sich Hinweise, daß auch der Wirtsstamm, dessen Zuchttemperatur, das Alter von Parasit und Wirt und der Eiablageort des Parasiten die Reaktionen beeinflussen. Obgleich die Entwicklung von Parasitenembryonen bereits gehemmt war, ehe sie innerhalb des Wirtes von Melanin eingeschlossen wurden, so verhinderten doch die Parasiten-embryonen und/oder die Wirkung der vor der Eiablage abgegebenen Paralysierungstoxine die normale Entwicklung der Wirte aus sechs Fliegenstämmen. Eine beträchtliche Steigerung der Überlebensrate der Parasiten trat ein, wenn M. domestica-Larven in einem Gemisch chemisch genau definierter Nahrung gezogen wurden.


With 8 Figures in the Text

Formerly National Research Council Postdoctorate Fellow, Research Institute, Belleville, Ontario.  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