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   38023篇
  免费   2460篇
  国内免费   420篇
耳鼻咽喉   712篇
儿科学   556篇
妇产科学   536篇
基础医学   6173篇
口腔科学   1022篇
临床医学   3310篇
内科学   7519篇
皮肤病学   1363篇
神经病学   2884篇
特种医学   2129篇
外科学   4682篇
综合类   205篇
现状与发展   3篇
一般理论   9篇
预防医学   1817篇
眼科学   768篇
药学   3534篇
中国医学   561篇
肿瘤学   3120篇
  2024年   33篇
  2023年   281篇
  2022年   896篇
  2021年   1396篇
  2020年   739篇
  2019年   1065篇
  2018年   1280篇
  2017年   1018篇
  2016年   1477篇
  2015年   1977篇
  2014年   2144篇
  2013年   2495篇
  2012年   3683篇
  2011年   3449篇
  2010年   2089篇
  2009年   1661篇
  2008年   2331篇
  2007年   2079篇
  2006年   1804篇
  2005年   1695篇
  2004年   1376篇
  2003年   1167篇
  2002年   1012篇
  2001年   472篇
  2000年   439篇
  1999年   360篇
  1998年   188篇
  1997年   153篇
  1996年   104篇
  1995年   93篇
  1994年   90篇
  1993年   84篇
  1992年   128篇
  1991年   150篇
  1990年   123篇
  1989年   104篇
  1988年   104篇
  1987年   86篇
  1986年   92篇
  1985年   72篇
  1984年   51篇
  1983年   44篇
  1982年   35篇
  1979年   60篇
  1978年   40篇
  1975年   54篇
  1972年   41篇
  1971年   58篇
  1970年   36篇
  1968年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Background/purpose: Vitiligo and nevus depigmentosus (ND) present similar hypopigmented macules with significantly different prognoses. Although the distinction between the two diseases is important, differential diagnosis relies on medical history and physical examination, which is far from decisive in some cases. The Mexameter® is an objective skin color-measuring device, and has been reported to provide a reproducible and sensitive means of quantifying small skin color differences. In this study, we investigated the usefulness of a Mexameter® for discriminating these diseases.
Methods: A selection of 202 hypopigmented skin lesions (182 from vitiligo and 20 from ND) were the objects of this study. Using a Mexameter, MIs were obtained from lesions and symmetrically located control skin. RMIs, ratios of the MIs of lesional skins to control skins, were calculated.
Results: The mean MIs and RMIs were significantly different for vitiligo and ND. The mean RMI of ND lesions was 74±13, which was significantly higher than that of vitiligo lesions (50±24). No ND lesion had an RMI of <50%.
Conclusion: This study shows that the Mexameter®, an objective pigment-measuring device, can be used to achieve a more accurate diagnosis of hypopigmentary disorders, and that the relative melanin index (RMI), which represents the relative pigment levels, might be a more effective parameter than the melanin index (MI) itself for comparing pigmentation differences.  相似文献   
3.
4.
5.
The present study was designed to evaluate the hypothesis that nebulised budesonide (NB) might be an alternative to systemic corticosteroids (SC) in the treatment of patients with exacerbations of chronic obstructive pulmonary disease (ECOPD). Patients hospitalised with ECOPD (n = 159) were randomised into three groups. Group 1 received only standard bronchodilator treatment (SBDT), group 2 received SC (40 mg prednisolone) plus SBDT, and group 3 received NB (1,500 microg q.i.d.) plus SBDT. Improvement during 10-day hospitalisation was compared with exacerbation and rehospitalisation rates after discharge. While mean+/-sd age was 64.1+/-8.9 yrs (female/male = 0.1), mean forced expiratory volume in one second (FEV(1)) at admission was found to be 37.2+/-12.2% predicted. Arterial blood gases and spirograms recovered faster in groups 2 and 3. While improvements in arterial oxygen tension (P(a,O(2))) and forced vital capacity (FVC) in group 2, and improvements in P(a,O(2)), FVC and FEV(1) in group 3, became significant at 24-h control, the first significant improvement in group 1 appeared in arterial oxygen saturation at 72-h control. The mean improvement of P(a,O(2)) after 10 days was 1.20 and 1.06 kPa (9 and 8 mmHg) higher in group 2 and 3, respectively, than in group 1. Blood glucose exhibited an upward trend only in group 2. The study demonstrates that nebulised budesonide may be an effective and safe alternative to systemic corticosteroids in the treatment of exacerbations of chronic obstructive pulmonary disease.  相似文献   
6.
OBJECTIVE: To determine the location in soft tissues of the calcifications, similar to calcified carotid atheromas, that can be observed radiographically in the cervical region in panoramic radiographs. STUDY DESIGN: In each anatomic cadaver specimen preserved in formol, consisting of the head and neck, radiopaque spheres (made from gutta-percha) were positioned in anatomic structures of the cervical region that can be sites of calcification. For each anatomic structure marked in this way, panoramic radiography was performed, consisting of 17 radiographs. The images obtained were analyzed by 24 examiners who indicated which radiographs, in their opinion, presented the radiopaque reference projected in the region of bifurcation of the carotid artery. Analysis of 2 proportions from agreement and disagreement was used to determine radiopacities that could be confused in panoramic radiographs with calcified atheromas in the carotid artery. RESULTS: The results showed that 75% (18) of the examiners correctly indicated the reference in the bifurcation of the carotid artery and 79.2% (19) indicated a triticeous cartilage as calcified atheroma of the carotid artery. CONCLUSIONS: Calcified atheromas of the carotid artery are not the only features that can produce radiopaque images lateral to the panoramic radiograph; the presence of calcification in the triticeous cartilage also can induce an erroneous diagnosis of calcified carotid atheroma.  相似文献   
7.
Transforming growth factor-β1 (TGF-β1) is known to be a potent growth inhibitor for many cell types, including most epithelial cells. In skin keratinocytes, TGF-β1 has been shown to inhibit growth and to rapidly reduce c-mycexpression. However, the molecular mechanism of TGF-β1 action on cell growth of cervical carcinoma has not yet been elucidated. We thus assessed the effect of TGF-β1 on the growth of cervical carcinoma cell lines. Two cervical squamous carcinoma cell lines, CUMC-3 and CUMC-6, were incubated with varying concentrations of TGF-β1, and growth inhibition was evaluated with tetrazolium-based colorimetric assay. After culture in TGF-β1 for 24 h, inhibition of growth was detected in a dose-dependent manner at concentrations of 0.1–10 ng/ml in both cell lines. This effect of TGF-β1 on cultured carcinoma cells was associated with apoptotic process including oligonucleosomal ladder DNA and apoptotic body formations. Northern blot analysis revealed c-mycmRNA expression was suppressed by 10 ng/ml of TGF-β1 following 3 h of treatment in both cell lines. Western blot analysis showed that the level of p27Kip1protein was increased after TGF-β1 treatment in both cell lines. These results suggest that the mechanisms by which TGF-β1 inhibits the growth of cervical carcinoma are complex and may include effects on down-regulation of c-mycgene, and overexpression of p27Kip1protein.  相似文献   
8.
Replication-defective retroviruses expressing the t- neu oncogene, or a hybrid protein with the neu tyrosine kinase linked to the external region of the human epidermal growth factor receptor ( egfr-neu ), were used to establish lines of murine oligodendroglial precursor cells. Differentiation of the t- neu lines into myelin-associated glycoprotein (MAG)-positive oligodendrocytes was induced by dibutyryl cAMP, and the egfr-neu line showed limited differentiation in vitro upon withdrawal of epidermal growth factor. Cerebellar granule cell neurons expressed mitogens for the cell lines. Upon transplantation into demyelinated lesions, t- neu line cells engaged with the demyelinated axons whereas the egfr-neu line cells differentiated further and ensheathed the axons. These cell lines thus interact with neurons in vitro and in vivo and can be used as tools to define the molecules involved in different stages of neuron-glia interaction.  相似文献   
9.
10.
A reproducible liver lesion was caused in 28 pigs by intermittent, intraperitoneal administration of thioacetamide. The morphological degree of the liver lesion was checked by histological investigations (material drawn from the liver by biopsy). During a 3-day infusion period a so-called liver solution (Aminofusin hepar) was given to one group of animals, a normal solution (Infesol) to a second group, and only an electrolyte infusion solution under oral nutrition ad libitum to a third one. The solutions were labelled with (15N) glycine. The amounts of total N, total 15N, 15N with single non-protein fractions, a number of enzymes of 15N incorporated into the liver protein were measured in urine, and the following points were established: 1. The catabolic situation of metabolism is eliminated both by the so-called normal solution and the specific amino acid solution. The two mixtures of L-amino acids thus have a nutritive effect. 2. The toxic liver lesion is an indication for parenteral nutrition. Oral nutrition alone is not sufficient. 3. The so-called liver solution influences the liver metabolism of the protracted liver lesion more than the so-called normal solution does, and considerably more than an electrolyte infusion solution under oral nutrition ad libitum.  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