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   31503篇
  免费   2559篇
  国内免费   72篇
耳鼻咽喉   544篇
儿科学   1253篇
妇产科学   1014篇
基础医学   4311篇
口腔科学   832篇
临床医学   2748篇
内科学   7344篇
皮肤病学   747篇
神经病学   3254篇
特种医学   996篇
外国民族医学   3篇
外科学   3899篇
综合类   534篇
一般理论   43篇
预防医学   2301篇
眼科学   633篇
药学   1769篇
中国医学   8篇
肿瘤学   1901篇
  2021年   413篇
  2020年   271篇
  2019年   454篇
  2018年   507篇
  2017年   363篇
  2016年   405篇
  2015年   461篇
  2014年   642篇
  2013年   971篇
  2012年   1266篇
  2011年   1338篇
  2010年   789篇
  2009年   682篇
  2008年   1209篇
  2007年   1307篇
  2006年   1303篇
  2005年   1234篇
  2004年   1237篇
  2003年   1123篇
  2002年   1192篇
  2001年   1096篇
  2000年   1167篇
  1999年   982篇
  1998年   365篇
  1997年   306篇
  1996年   320篇
  1995年   295篇
  1994年   289篇
  1993年   303篇
  1992年   863篇
  1991年   805篇
  1990年   685篇
  1989年   728篇
  1988年   676篇
  1987年   708篇
  1986年   650篇
  1985年   676篇
  1984年   536篇
  1983年   465篇
  1982年   300篇
  1980年   259篇
  1979年   457篇
  1978年   307篇
  1977年   258篇
  1976年   280篇
  1975年   268篇
  1974年   297篇
  1973年   294篇
  1972年   267篇
  1971年   261篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
B M Cohen 《Microsurgery》1987,8(2):68-77
Significant numbers of infertile women have congenital anomalies or anatomical distortion of the fimbrial-gonadal mechanism in their otherwise healthy oviducts. The diagnosis and surgical treatment of multiple congenital accessory tubal ostia, the elongated fimbria-ovarica syndrome, and management of paratubal cysts is described. Microsurgical correction of these defects was followed by term pregnancies in 46%, 57% and 28% of the three entities respectively and this data indicates that significant numbers of women with these defects may be helped by microsurgery. Failure to recognize these abnormalities may otherwise result in patients being diagnosed as idiopathic infertility, a decision which may exclude them from the possibility of undergoing a successful form of microsurgical treatment.  相似文献   
72.
A system proposed by Wing and coworkers for subtyping autistic individuals on the basis of social interaction is examined in 78 autistic, 39 atypical, and 32 nonautistic, developmentally disordered individuals. Clinical ratings and questionnaire data based on the proposed subtypology were employed. Clinicians were able to reliably group both autistic and nonautistic cases into the three subtypes; these subtypes were strongly related to IQ. Issues relating to the validity and utility of this subtypology are discussed.  相似文献   
73.
74.
Conventionally a confidence interval (CI) for the standardized mortality ratio is set using the conservative CI for a Poisson expectation, μ. Employing the mid-P argument we present alternative CIs that are shorter than the conventional ones. The mid-P intervals do not guarantee the nominal confidence level, but the true coverage probability is only lower than the nominal level for a few short ranges of μ. The implications for mid-P confidence intervals of various proposed definitions of two-sided tests for discrete data are discussed.  相似文献   
75.
Malignant thymomas are among the least common mediastinal tumors in the pediatric age group. Thymomas are considered malignant on the basis of macroscopic and microscopic invasiveness. As only 20 well-documented cases involving children have been reported in the literature, the pattern of responsiveness to therapy and the value of prognostic signs is obscure. Two cases of malignant pediatric thymomas are reported with pathognomonic histoimmunological features of aggressive thymoma. One was cured, with a follow-up of 70 months, and one died while on therapy. Analysis of the histological features and the immunoperoxidase staining displays the complexity of pediatric thymomas and the inability to prognosticate the outcome, respectively.  相似文献   
76.
In hypertrophic pyloric stenosis, the muscle is typically described as hypoechoic on sonography. However, we have frequently noted a nonuniform pattern; the pyloric muscle seen in the transverse plane is more echogenic in the near and far fields and less echogenic on the sides. The muscle also appears almost as echogenic as the liver on midline longitudinal sonograms. To establish the frequency of these findings, we reviewed the sonograms of 71 infants with hypertrophic pyloric stenosis. The muscle was imaged directly during surgery in three patients. In an in vitro experiment, muscle arranged to stimulate the pyloric ring was scanned in a water bath. Then, using two sections of muscle, we compared the echogenicity when scanning in a plane perpendicular to the long axis of the muscle fibers with that seen with the beam parallel to the long axis of the muscle fibers. In the transverse plane, nonuniform echogenicity of the pyloric muscle was seen in 59 (98%) of 60 patients. In the midline longitudinal plane, the muscle was equal to or slightly less echogenic than the liver in all patients. Both the in vivo and in vitro studies show that the echogenicity varies with the relationship of the ultrasound beam to the orientation of the circular muscle fibers; this phenomenon is known as the anisotropic effect. Our results show that nonuniform echogenicity of the hypertrophied pyloric muscle is a characteristic sonographic finding caused by the anisotropic effect, which is related to the orientation of the ultrasound beam with respect to the circular fibers of the pyloric muscle.  相似文献   
77.
Molluscum contagiosum virus (MCV) is an unclassified poxvirus which has recently become recognized as causing a major sexually transmitted disease. At present no assay is available for specific detection of MCV because the virus cannot be serially propagated in cell culture. Since MCV produces an abortive, limited growth with some cytopathic effect in certain cell lines, we were able to develop an in situ hybridization assay for detection of MCV genome in clinical specimens. Human fetal diploid lung cell monolayers were infected with clinical specimens, and after proper incubation and fixation in paraformaldehyde, hybridization was performed under full stringency conditions with a molecularly cloned biotinylated probe. Only MCV infected cells showed homology to the MCV probe with a purple-brown cytoplasmic staining. Additionally, we have described an in situ hybridization assay for direct detection of MCV genome in formalin-fixed, paraffin-embedded biopsies. Characteristic intracytoplasmic Molluscum bodies (Henderson-Paterson bodies) were detected in stratum spinosum cells of the epidermis. Striking staining similarities have been observed between in situ hybridization and haematoxylin-eosin cytostaining. These procedures are the first successful identification of MCV genome in clinical samples by molecular hybridization, with sensitivity and specificity equal to or greater than electron microscopy.  相似文献   
78.
It is now known that amputation results in reorganization of central motor pathways, but the mechanism for the changes is unclear. One possibility is alteration of the excitability of the alpha motoneurons. We studied motor reorganization and excitability of alpha motoneurons to Ia input in 6 subjects with unilateral lower limb amputation. A Cadwell MES-10 stimulator was used to deliver transcranial magnetic stimuli through a circular coil centered on the sagittal axis 4 cm anterior to Cz and through an 8-shaped coil positioned over scalp locations 1 cm apart along the coronal axis. Surface EMG was recorded bilaterally from quadriceps femoris, the first muscle immediately proximal to the site of amputation. Excitability of the spinal alpha motoneuron pool to Ia afferents was assessed by determining the ratio of the maximal H reflex to the maximal M response (H/M ratio) elicited in the quadriceps femoris. Stimuli of equal intensity delivered to optimal scalp positions recruited a larger percentage of the alpha motoneuron pool in muscles ipsilateral to the stump than in those contralateral to the stump (P less than 0.01). Mean onset latencies of motor evoked potentials were shorter in ipsilateral muscles than in contralateral muscles (P less than 0.01). Muscles ipsilateral to the stump showed a trend toward activation from a larger number of scalp positions than those contralateral to the stump (P = 0.06). There was no difference in the quadriceps H/M ratios (7.2% ipsilateral vs. 10.9% contralateral). The absence of changes in the excitability of the alpha motoneuron pool in the presence of motor reorganization targeting muscles proximal to the stump suggests that reorganization occurs proximal to the alpha motoneuron level.  相似文献   
79.
A relationship between teething and fever was sought by examining mothers' reports of the 20 days before the eruption of the first tooth in 46 healthy infants. Twenty infants had a fever of greater than 37.5 degrees C on day 0 compared with seven infants (or fewer) from day 19 to day 4. The danger of attributing fever to teething is emphasised.  相似文献   
80.
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