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   14622篇
  免费   551篇
  国内免费   41篇
耳鼻咽喉   183篇
儿科学   251篇
妇产科学   361篇
基础医学   3025篇
口腔科学   288篇
临床医学   814篇
内科学   1644篇
皮肤病学   508篇
神经病学   1173篇
特种医学   1710篇
外科学   1915篇
综合类   63篇
预防医学   1046篇
眼科学   171篇
药学   1547篇
中国医学   100篇
肿瘤学   415篇
  2023年   72篇
  2022年   58篇
  2021年   131篇
  2020年   124篇
  2019年   168篇
  2018年   377篇
  2017年   254篇
  2016年   319篇
  2015年   281篇
  2014年   448篇
  2013年   676篇
  2012年   1123篇
  2011年   1451篇
  2010年   704篇
  2009年   273篇
  2008年   878篇
  2007年   1022篇
  2006年   975篇
  2005年   776篇
  2004年   682篇
  2003年   690篇
  2002年   597篇
  2001年   411篇
  2000年   515篇
  1999年   302篇
  1998年   116篇
  1997年   85篇
  1996年   74篇
  1995年   82篇
  1994年   53篇
  1993年   40篇
  1992年   48篇
  1991年   51篇
  1990年   65篇
  1989年   44篇
  1988年   51篇
  1985年   56篇
  1984年   55篇
  1982年   61篇
  1981年   53篇
  1980年   45篇
  1979年   44篇
  1978年   42篇
  1977年   36篇
  1976年   40篇
  1975年   47篇
  1974年   37篇
  1973年   43篇
  1969年   35篇
  1967年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Left Bochdalek hernia is a serious and complex condition with high mortality. In most cases, it presents in the neonatal period and is seldom found later in life when symptomatology, usually after an asymptomatic period, is quite different and the prognosis excellent. The embryological development of left Bochdalek hernia suggests the presence of abdominal content in the left pleural cavity before birth. The type of clinical presentation and the prognosis depend on the time of visceral herniation. This study presents two cases of left Bochdalek hernia with delayed presentation. In both cases, after surgical reposition of the hernia, a small congenital diaphragmatic defect was found hidden between the rims of diaphragm. This indicates the possibility for the abdominal content to enter the left pleural cavity at the time of presentation.  相似文献   
63.
Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detect the presence of neutrons in the photon beam and to estimate the spatial distribution of thermal and fast neutrons in the patient plane as a function of collimator opening.  相似文献   
64.
2 mg/kg melanotan II (MTII, administered i.p.), a cyclic peptide analog of α-melanocyte stimulating hormone, at a single dose increased grooming in naive rats placed in an unfamiliar open-field device without changing locomotion or rearing. Male rats exposed to restraint/immobilization stress (IS) for 1 h on three consecutive days displayed increased grooming after the second stressor exposure, compared to pre-stress levels. MTII, administered to the rats after IS, enhanced the grooming response compared both to the pre- and post-stress values. The increase was greatest after the first dose and declined over the following two applications. As to the locomotion of rats in the entire experimental space, IS reduced the distance moved only after the first two stressor exposures; MTII did not influence these alterations. Locomotion in the central part of arena was not reduced by the stressor or by MTII, on the contrary, there was an increase in both groups after the third intervention. The only observed change in rearing was an increase in the MTII group after the third restraint exposure. Thus, MTII selectively increased grooming without markedly affecting the spatio-temporal structure of locomotor behavior in the open-field. The decline of MTII enhanced grooming over the three test days may be interpreted in terms of adaptation to the stressor and of the developing tolerance to the peptide.  相似文献   
65.
Procedures for flow cytometric analysis and sorting of mitotic chromosomes (flow cytogenetics) have been developed for chickpea (Cicer arietinum). Suspensions of intact chromosomes were prepared from root tips treated to achieve a high degree of metaphase synchrony. The optimal protocol consisted of a treatment of roots with 2mmol/L hydroxyurea for 18h, a 4.5-h recovery in hydroxyurea-free medium, 2h incubation with 10µmol/L oryzalin, and ice-water treatment overnight. This procedure resulted in an average metaphase index of 47%. Synchronized root tips were fixed in 2% formaldehyde for 20min, and chromosome suspensions prepared by mechanical homogenization of fixed root tips. More than 4×105 morphologically intact chromosomes could be isolated from 15 root tips. Flow cytometric analysis of DAPI-stained chromosomes resulted in histograms of relative fluorescence intensity (flow karyotypes) containing eight peaks, representing individual chromosomes and/or groups of chromosomes with a similar relative DNA content. Five peaks could be assigned to individual chromosomes (A, B, C, G, H). The purity of sorted chromosome fractions was high, and chromosomes B and H could be sorted with 100% purity. PCR on flow-sorted chromosome fractions with primers for sequence-tagged microsatellite site (STMS) markers permitted assignment of the genetic linkage group LG8 to the smallest chickpea chromosome H. This study extends the number of legume species for which flow cytogenetics is available, and demonstrates the potential of flow cytogenetics for genome mapping in chickpea.  相似文献   
66.
67.
68.
69.
70.
Anatomical variations in the dimensions of different brain structures have been correlated with clinical syndromes. This study on the parameters of normal and abnormal cavum septi pellucidi (CSP) can be of clinical significance. We obtained 479 brains from autopsied persons (310 males and 169 females, 377 normal or asymptomatic and 102 abnormal or symptomatic persons, aged 22-89 years) and observed that 110 brains (75 males and 35 females) had CSP. These cava were classified into two groups depending on the past medical histories of the autopsied person: 40 asymptomatic and 70 symptomatic cava. We have defined symptomatic cava as those in autopsied persons who had known past medical history of psychiatric or neurological disease. Asymptomatic cava were in autopsied persons who had no known past medical history of psychiatric or neurological disease. The CSP parameters (length, width, depth) of the symptomatic and asymptomatic groups were measured and were statistically analyzed. Analysis showed that the cava in the symptomatic group were significantly longer and wider. Discriminant function analysis was used to derive a mathematical formula to classify CSP into an asymptomatic or symptomatic group based on length and width measurements of the cavum.  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