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   5656篇
  免费   302篇
  国内免费   35篇
耳鼻咽喉   66篇
儿科学   117篇
妇产科学   101篇
基础医学   769篇
口腔科学   81篇
临床医学   354篇
内科学   1640篇
皮肤病学   128篇
神经病学   363篇
特种医学   238篇
外科学   998篇
综合类   32篇
预防医学   139篇
眼科学   62篇
药学   307篇
中国医学   21篇
肿瘤学   577篇
  2023年   28篇
  2022年   86篇
  2021年   126篇
  2020年   73篇
  2019年   104篇
  2018年   130篇
  2017年   94篇
  2016年   115篇
  2015年   106篇
  2014年   164篇
  2013年   201篇
  2012年   319篇
  2011年   346篇
  2010年   207篇
  2009年   174篇
  2008年   287篇
  2007年   318篇
  2006年   331篇
  2005年   319篇
  2004年   261篇
  2003年   284篇
  2002年   240篇
  2001年   150篇
  2000年   158篇
  1999年   146篇
  1998年   58篇
  1997年   68篇
  1996年   48篇
  1995年   50篇
  1994年   34篇
  1993年   37篇
  1992年   95篇
  1991年   96篇
  1990年   82篇
  1989年   88篇
  1988年   65篇
  1987年   51篇
  1986年   54篇
  1985年   51篇
  1984年   31篇
  1983年   44篇
  1982年   17篇
  1981年   23篇
  1980年   17篇
  1979年   19篇
  1976年   15篇
  1975年   21篇
  1970年   18篇
  1969年   22篇
  1968年   18篇
排序方式: 共有5993条查询结果,搜索用时 0 毫秒
41.
Ultrastructual characteristics of the dorsal skin responses to a single irradiation of UVA (1100 kJ/m2) were examined in Wistar-derived hypotichotic WBN/ILA-Ht rats (HtRs). In the epidermis, mitochondrial swelling of some keratinocytes and dissociation of keratinocytes due to intercellular edema developed at 3 hours (h) after irradiation and continued to 48 h. At 6 h, in addition to these changes, necrosis of keratinocytes accompanied with infiltration of neutrophils was also observed in some portions, and epidermal hyperplasia with many keratinocytes showing nucleolar hypertrophy and some mitotic keratinocytes was observed at 48 h. In the dermis, mitochondrial swelling and/or partial cytoplasmic destruction in capillary endothelial cells and edema with inflammatory cell infiltration were observed at and after 3 h, and extravasation of erythrocytes was found in some capillaries at 48 h. Mitochondrial swelling was also frequently found in pericytes and fibroblasts. Inflammatory cells were mainly composed of neutrophils throughout the experimental period. Mild degranulation of mast cells which also showed mitochondrial swelling was observed at and after 3 h, and a close special relationship between mast cells and fibroblasts or neutrophils was sometimes observed. In conclusion, the most prominent change in the dorsal skin of HtRs exposed to UVA was degeneration of capillary endothelial cells, resulting in edema and inflammatory cell infiltration, and the most characteristic cytopathic effect of UVA was mitochondrial swelling, and it was common to keratinocytes, capillary endothelial cells, pericytes, mast cells, and fibroblasts.  相似文献   
42.
Gastrin-releasing peptide (GRP) has been proposed as a novel regulatory peptide in the reproductive tract. We previously demonstrated that GRP immunoreactivities are found predominantly in the uterine gland epithelial cells of nonpregnant and pregnant cows. The present study focused on the distribution of GRP immunoreactivity and the expression of GRP mRNA in the bovine endometrium during the estrous cycle. Tissues were collected from 21 uterine horns and bodies during the estrous cycle. RT-PCR showed the expected GRP mRNA fragments (284 bp) in the tissues from all stages of the cycle. In situ hybridization results ascertained the expression of the GRP mRNA in the uterine gland epithelial cells and superficial epithelial cells of the endometrium. Positive staining of GRP immunoreactivity in the uterine gland epithelial cells was detected in both the uterine horn and body from all stages of the cycle. In metestrus and diestrus stages, GRP was also detected in the superficial epithelial cells of horn, but not in the body. The degrees of GRP mRNA expression and intensities of GRP immunoreactivity in the endometrium increased from proestrus to diestrus stages. These findings suggest that GRP may be important both in the endometrial remodeling during the estrous cycle and in the implantation and development of blastocysts.  相似文献   
43.
Recently nutrition support team (NST) has been established for the purpose of prevention of complications which are caused by nutrition disorders and reduction of the medical expenses. Although physical examinations and blood biochemical data had been used as the indexes evaluating nutritional of patients, they were not suitable for the evaluation for the short-term in-patient. On the contrary, serum albumin (ALB) has been wildly used as a nutritional marker. However, it is impossible to evaluate nutrition state for the short-term in-patient and acute phase disease patient accurately, because the plasma half-life is 21 days and it takes long time to detect the change in nutritional state by its value. Rapid turnover proteins (RTP), whose plasma half-life is shorter, has paid attention to evaluate nutritional state for the short-term in-patients and acute phase disease patients. Although, prognostic inflammatory and nutritional index (PINI) was considered as a useful maker for evaluating inflammatory and nutritional states using the concentrations of transthyretin (TTR), a RTP, alpha1-acid glycoprotein (alpha1-AG), a chronic inflammation marker, C reactive protein (CRP), a acute inflammation marker, and ALB, However, it has several pitfalls. We newly made serum amyloid A (SAA) index using SAA instead of CRP. When we compared SAA index with PINI in many diseases, it turned out that SAA index became a more effective index which reflected the patient condition than did PINI. As for this index, it is expected to be used by NST while further alternation may be needed.  相似文献   
44.
We describe a case of hepatocellular carcinoma in which a tumor embolus in the portal vein and 3 of 4 intrahepatic metastases were necrosed completely by Lipiodol transcatheter chemo-embolization (Lipiodol-TCE). Tumor emboli in the portal vein and intrahepatic metastases usually cannot be necrosed by conventional transcatheter chemo-embolization alone, because small nodules such as intrahepatic metastases and tumor emboli in the portal vein are supplied blood from the portal vein. However, in this case, Lipiodol-TCE was effective against tumor emboli in the portal vein and intrahepatic metastases. ACTA PATHOL JPN 38: 1363-1367, 1988.  相似文献   
45.
Three monoclonal antibodies (mAbs), termed SN2, SN2a and SN2b, were used in the present work to study a human T-cell leukemia-associated cell surface glycoprotein, GP37. Strong specificity of mAbs SN2, SN2a and SN2b for T leukemia cells was demonstrated by radioimmunoassay and fluorescence-activated cell sorter (FACS) analysis. GP37 was not detected on normal human peripheral blood lymphocytes, purified normal T-cells, normal thymocytes nor normal bone marrow cells. Furthermore, GP37 was barely detectable on phytohemagglutinin (PHA)- and Concanavalin A (Con A)-activated T-cells. The results indicate clinical utility of these mAbs. Competitive binding experiments show that the epitopes recognized by SN2 and SN2a are sufficiently close to each other to allow complete reciprocal inhibition of binding whereas the epitopes recognized by SN2 and SN2b are less close to allow only partial reciprocal binding inhibition. The biochemical nature of antigenic determinants defined by these mAbs was studied by treating T leukemia cells with trypsin, chymotrypsin, thermolysin, neuraminidase and mixed glycosidases. The results suggest that the antigenic determinants defined by these mAbs all consist of the protein moiety of the glycoprotein GP37. No significant antigenic modulation was observed when T leukemia cells were reacted with SN2. In a sequential immunoprecipitation experiment, a 125I-labeled leukemia antigen preparation was first treated with a rabbit anti-T leukemia antiserum. The latter had been prepared by immunizing a rabbit with a partially purified human T leukemia antigen preparation and showed a good specificity for T leukemia cells. Subsequent treatment of the labeled antigen preparation with SN2 showed that SN2 antigen had been precleared. Thus, both mouse mAb SN2 and the rabbit anti-T leukemia antiserum react with the same GP37 molecule.  相似文献   
46.
The cationic, ring-opening copolymerization of 1,6-anhydro-2,3,4-tri-O-benzyl-ß-D -glucopyranose with epichlorohydrin, 3,3-bis(chloromethyl)oxetane and 1,3-dioxolane was investigated with phosphorus pentafluoride as catalyst at low temperatures. Besides, copolymerization of 1,6-anhydro-2,3,4-tri-O-methyl-ß-D -glucopyranose with epichlorohydrin was studied. Structure and composition of the copolymers were determined by 1H and 13C NMR spectroscopy, indicating that copolymerization occurred in each combination of monomers. Number-average molecular weights of copolymers were in the range of 1 400 to 22 800. From the specific rotation and 13C NMR spectrum of copolymers, it was revealed that the ring-opening copolymerization of the benzylated 1,6-anhydro-glucopyranose with the cyclic monomers occurred in a stereoregular manner to give the C-1 carbon of glucose unit with α-configuration. Debenzylation of a copolymer prepared from 1,6-anhydro-2,3,4-tri-Obenzyl-ß-D -glucopyranose and 1,3-dioxolane gave a copolymer composed of free sugar units in the polymer main chain. Assignment of 13C NMR spectra of 2,3,4-tri-O-benzyl-ß-D -glucopyranan and of a copolymer of 1,6-anhydro-2,3,4-tri-O-benzyl-ß-ß-glucopyranose with 1,3-dioxolane was attempted.  相似文献   
47.
Erythropoietin (Epo) is an important regulator of erythropoiesis and stimulates the proliferation of early erythroid precursors as well as the differentiation of late erythroid precursors of the erythroid lineage. However, recent studies have indicated that Epo also has angiogenic properties and plays an important role in the oestrogen-dependent cyclical angiogenesis within the mouse uterus. It was therefore postulated that Epo may be an important angiogenic factor in endometriosis. In order to address this hypothesis the concentration of Epo in peritoneal fluid (PF) was determined in patients with or without endometriosis. PF was collected from patients with endometriosis (n = 42) or without endometriosis (n = 18). Detectable concentrations of Epo were found in all PF samples analysed. The concentration of Epo in PF from patients with endometriosis was significantly higher than that in the control group (13.1 +/- 1.2 mIU/ml versus 7.2 +/- 0.7 mIU/ml, mean +/- SE respectively, P < 0.01). Furthermore, in patients with endometriosis the Epo concentrations in PF from patients with stage I disease (n = 17, 16.6 +/- 3.0 mIU/ml) were significantly higher than those with stage II (n = 8, 10.7 +/- 1.2 mIU/ml, P < 0.03), III (n = 13, 8.4 +/- 1.0 mIU/ml, P < 0.01), IV disease (n = 7, 7.5 +/- 1.0 mIU/ml, P < 0.01). These data suggest that Epo may play a role in the pathogenesis of endometriosis particularly in the initiation of the disease.  相似文献   
48.
49.
OBJECTIVE: To investigate the mechanism of staurosporine-induced glioma cell death and cell cycle arrest using adenovirus-mediated gene transfection, as well as the function of retinoblastoma (Rb) and genetic instability induced by staurosporine. METHODS: Cell cycle regulation, cell death and nuclear abnormalities induced by staurosporine were examined using an adenovirus vector expressing Rb, p16 or p21 genes in human glioma cell lines. RESULTS: The Rb-defective SF-539 cell line was resistant to staurosporine compared with cell lines expressing intact Rb. SF-539 glioma cells exposed to staurosporine became multinucleated and then died. Multinucleation was prevented in SF-539 cells transfected with the Rb gene, thus decreasing the death rate of these cells. CONCLUSIONS: These results imply that enforced Rb expression protects cells from genomic instability induced by staurosporine regardless of its upstream molecular effects.  相似文献   
50.
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