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   171994篇
  免费   6509篇
  国内免费   319篇
耳鼻咽喉   3040篇
儿科学   6423篇
妇产科学   4362篇
基础医学   24180篇
口腔科学   4813篇
临床医学   12851篇
内科学   31265篇
皮肤病学   4719篇
神经病学   15825篇
特种医学   8820篇
外国民族医学   24篇
外科学   28502篇
综合类   1088篇
一般理论   37篇
预防医学   8169篇
眼科学   4616篇
药学   11862篇
中国医学   357篇
肿瘤学   7869篇
  2021年   1267篇
  2020年   1146篇
  2019年   1321篇
  2018年   2856篇
  2017年   2356篇
  2016年   3290篇
  2015年   3657篇
  2014年   3842篇
  2013年   5411篇
  2012年   8351篇
  2011年   7771篇
  2010年   4612篇
  2009年   3717篇
  2008年   7721篇
  2007年   8558篇
  2006年   8603篇
  2005年   9004篇
  2004年   8569篇
  2003年   8466篇
  2002年   8357篇
  2001年   6235篇
  2000年   6309篇
  1999年   5448篇
  1998年   1605篇
  1997年   1313篇
  1996年   1013篇
  1995年   812篇
  1994年   761篇
  1992年   2429篇
  1991年   2339篇
  1990年   2305篇
  1989年   2169篇
  1988年   1887篇
  1987年   1870篇
  1986年   1740篇
  1985年   1667篇
  1984年   1314篇
  1983年   1043篇
  1979年   1406篇
  1978年   1023篇
  1977年   872篇
  1975年   1096篇
  1974年   1144篇
  1973年   1036篇
  1972年   1041篇
  1971年   1007篇
  1970年   910篇
  1969年   837篇
  1968年   807篇
  1967年   766篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
21.
Polyploidization and centrosome hyperamplification in inflammatory bronchi   总被引:1,自引:0,他引:1  
OBJECTIVE AND DESIGN: Inflammatory and tumorous bronchi were screened in order to obtain new tumor relevant cytogenetic parameters. MATERIAL OR SUBJECTS: Bronchial cells of 32 patients were cultivated by standard cell culture procedures. METHODS: Tetraploidy and aneuploidy was determined by enumeration of chromosome 7 and 8 versus the number of centrosomes. The resulting data were correlated with histopathological data. RESULTS: Tetra- and aneuploidy of epithelial cells were detectable in 76% of tumor cell cultures, 75% of high grade inflammatory tissues and 40% of non- and low grade-inflammatory tissues. Additionally, we observed centrosome hyper-amplification and multipolar mitoses not only in the tumor but also in the early stages of inflammation. CONCLUSION: Inflammatory bronchi already show tumor-specific features and may consequently represent the preliminary genetic stage of cancer development in bronchi.  相似文献   
22.
23.
The experimental infection of immunocompetent and immunodeficient athymic mice with an avirulent encephalitogenic Toxoplasma strain (DX strain) was employed to study the ensuing encephalitic process by use of histological and immunocytochemical methods. In the acute phase of the infection Toxoplasma cysts and tachyzoites were accompanied by an infiltrate composed of macrophages, CD4+ and CD8+ T cells. In the chronic stage a granulomatous encephalitis developed. In contrast to immunocompetent NMRI mice, athymic nude NMRI mice died 3 weeks post-infection because of a generalized toxoplasmosis with predominant involvement of the brain. A salient feature of murine Toxoplasma encephalitis was up-regulation of class I and II major histocompatibility complex (MHC) gene products. Class I antigen was widely expressed on microglial cells and astrocytes. Class II antigen was only expressed on microglial cells despite a considerable astrogliosis. Our results indicate a differential expression of MHC-determined antigens on brain cells in acute and chronic murine Toxoplasma encephalitis.  相似文献   
24.
25.
Synthesis of Estradiol Haptens Two estradiol haptens, 4-(3β,17β-dihydroxyestran-7α-yl)butanoic acid ( 9 ) and 7α-(4-aminobutyl)-3β,17β-estradiols ( 13 ), were prepared from 19-nortestosterone by partial synthesis. The binding activity for the cytosol estrogen receptor was determined by competition against [3H]-estradiol; at a concentration of 2×10?7mol/l, compound 9 displaces 50% of [3H]-estradiol. Attached to AH-Sepharose 4B compound 9 allows the cytosol estrogen receptor from calf uterus to be concentrated 1800-fold by affinity chromatography.  相似文献   
26.
Wir berichten über den ersten Fall von polyzystischer lipomembran?ser Osteodysplasie oder “brain, bone and fat disease” in Deutschland. Die nach dem Erstbeschreibern auch als Morbus J?rvi-Hakola-Nasu bezeichnete Erkrankung ist bisher vor allem in Japan und in Finnland beschrieben worden. Einzelne F?lle wurden aus Schweden, Norwegen, Italien, Südafrika, Belgien und den USA berichtet. Im deutschsprachigen Raum ist bisher ein Fall aus ? ver?ffentlicht worden.  相似文献   
27.
Summary The prevalence of smoking, hypertension and diabetes mellitus was assessed in 221 patients suffering from internal carotid stenosis and compared with the prevalences in two sex- and age-matched control groups composed of subjects having normal Doppler findings and from non-neurological outpatients. Of the subjects with carotid stenosis 27.6% were hypertensive smokers in comparison with 9.5% and 17.2% in the two control groups. The difference of the stenosis cohort from the two control groups was significant (P<0.01 and P=0.016 respectively). There was no statistically significant differences between the occurrence of diabetes and hypertension in non-smokers and patients who smoked. In 394 investigated patients suffering from carotid stenosis or occlusion an obstruction index, based on the Doppler shift frequency, was calculated. This index was lowest in the normotentive non-smokers. It was only insignificantly higher in the hypertensive non-smokers but significantly so in the normotensive smokers. The index was highest in the hypertensive non-smokers. It was concluded that cigarette smoking, especially if associated with hypertension, is a determinant risk factor for carotid stenosis and occlusion.  相似文献   
28.
29.
Cerebral infarction is rare in premature newborns and is most commonly the result of arterial embolization from the placenta. A focal echodense area was identified on prenatal cranial ultrasonography (US) in a premature infant (34 weeks of gestation). After birth, cerebral infarction was confirmed by magnetic resonance imaging (MRI). The clinical findings, imaging findings and pathogenesis are discussed. New diagnostic methods such as MRI show to be a useful approach in the neonatal period facilitating recognition of cerebrovascular accidents also in low-birth-weight infants.  相似文献   
30.
The authors' 5-year experience in the management and care of prostatic carcinoma are summarized. Their method differs essentially from earlier practice. They have found a new diagnostic and therapeutic method by introducing the TECO irradiation therapy, extensively using bone scintigraphy, by introducing cytostatics, extensively applying the prostate-specific acid phosphatase and by performing rectal biopsy of the prostate. They describe their own observations on the diagnostics and therapy of prostatic carcinoma. They stress that none of the therapies is the method of choice, the use of the various kinds of treatment are defined by strict indications. They state that care of prostatic cancer patients is highly important because only observation of the course of the disease may ensure the evaluation of treatment results and the indication of the adequate therapeutic method.  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