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   1400篇
  免费   69篇
  国内免费   42篇
耳鼻咽喉   18篇
儿科学   29篇
妇产科学   5篇
基础医学   190篇
口腔科学   13篇
临床医学   79篇
内科学   568篇
皮肤病学   14篇
神经病学   69篇
特种医学   56篇
外科学   132篇
综合类   3篇
预防医学   32篇
眼科学   78篇
药学   61篇
中国医学   3篇
肿瘤学   161篇
  2023年   12篇
  2022年   17篇
  2021年   35篇
  2020年   16篇
  2019年   24篇
  2018年   35篇
  2017年   22篇
  2016年   37篇
  2015年   39篇
  2014年   34篇
  2013年   43篇
  2012年   66篇
  2011年   86篇
  2010年   57篇
  2009年   39篇
  2008年   73篇
  2007年   80篇
  2006年   80篇
  2005年   92篇
  2004年   90篇
  2003年   92篇
  2002年   93篇
  2001年   33篇
  2000年   39篇
  1999年   32篇
  1998年   29篇
  1997年   24篇
  1996年   20篇
  1995年   14篇
  1994年   10篇
  1993年   12篇
  1992年   22篇
  1991年   12篇
  1990年   10篇
  1989年   4篇
  1988年   12篇
  1987年   13篇
  1986年   7篇
  1985年   8篇
  1983年   4篇
  1982年   3篇
  1979年   5篇
  1978年   5篇
  1977年   4篇
  1975年   2篇
  1974年   2篇
  1972年   2篇
  1970年   4篇
  1968年   2篇
  1965年   2篇
排序方式: 共有1511条查询结果,搜索用时 15 毫秒
1.
2.
3.
The inhibitory effects of glycoproteins separated from a hot water extract of corn silk (U-CSE) on the formation of IgE antibodies after primarily and secondarily challenged responses with dinitrophenyl (DNP)-ovalbumin (OVA) antigen in mice were investigated using the passive cutaneous anaphylaxis (PCA) test. When U-CSE was given intranasally or intraperitoneally the day before primary immunization, IgE antibody production was strongly inhibited. Furthermore, it was found that new formation of IgE antibodies was readily inhibited by U-CSE administration in mice with high levels of IgE after primary immunization. It was also found that U-CSE markedly suppressed IgE antibody formation in secondarily challenged responses with the antigen. U-CSE may be clinically applicable to type I allergic diseases.  相似文献   
4.
PURPOSE: To clarify how the downward deviation of progressive addition lenses (PALs) reduces their near-addition effect in schoolchildren participating in a myopia control trial. METHODS: Among 95 schoolchildren wearing PALs for 6 months (age range: 6-12 years; refractive error range: -6.00 to -1.25 D), facial images were captured with a digital still camera placed 60 cm in front of the eyes while he or she was looking ahead with natural head posture. The vertical deviations of PALs from their ideal position (mm) were evaluated by analysing these images. RESULTS: The mean (+/-SD) downward deviations of PALs for the right and left eyes were 3.7 +/- 2.3 and 3.7 +/- 2.0 mm, respectively, and the largest downward deviation was 10.2 mm. For simulations using the average downward deviation, the near-addition effect of PALs was reduced to 30 and 63% of the expected value at the 10 degrees and 20 degrees downward eye positions, respectively. CONCLUSIONS: The downward deviation of PALs is a significant factor in reducing their therapeutic effect for near-addition. To ensure the proper alignment of PALs in children, the conventional spectacle-frame-fitting procedure is not sufficient, and repeated confirmation using a testing method similar to that used in this study is required.  相似文献   
5.
Bacteroides forsythus is a gram-negative, anaerobic, fusiform bacterium and is considered to be an etiological agent in periodontal disease. A lipoprotein fraction prepared from B. forsythus cells by Triton X-114 phase separation (BfLP) activated human gingival fibroblasts and a human monocytic cell line, THP-1, to induce interleukin-6 production and tumor necrosis factor alpha production. BfLP was found to be capable of inducing nuclear factor-kappaB translocation in human gingival fibroblasts and THP-1 cells. By using Chinese hamster ovary K1 cells transfected with Toll-like receptor genes together with a nuclear factor-kappaB-dependent CD25 reporter plasmid, it was found that signaling by BfLP was mediated by Toll-like receptor 2 but not by CD14 or Toll-like receptor 4. BfLP induced apoptotic cell death in human gingival fibroblasts, KB cells (an oral epithelial cell line), HL-60 cells (a human myeloid leukemia cell line), and THP-1 cells but not in MOLT4 cells (a T-cell leukemia cell line). Caspase-8, an initiator caspase in apoptosis, was found to be activated in these cells in response to BfLP stimulation. Thus, this study suggested that BfLP plays some etiological roles in oral infections, especially periodontal disease, by induction of cell activation or apoptosis.  相似文献   
6.
Mitotic figures of fibroblasts are seen within invasive ductal carcinoma (IDC) of the breast. This suggests that the proliferative activity of fibroblasts may play an important role in IDC tumor progression. The purpose of this study was to examine whether the proliferative activity of fibroblasts can predict lymph node metastasis (LNM) or distant-organ metastasis (DOM) of IDCs. Two hundred four consecutive patients with IDC of the breast surgically treated at the National Cancer Center Hospital East constituted the basis of this study. Proliferative activity of fibroblasts was immunohistochemically evaluated by the mouse MIB-1 monoclonal antibody against Ki-67 antigen. The MIB-1 labeling index was the percentage of fibroblasts with positively stained nuclei, and fields for cell counting were selected in inner and outer areas within IDCs. In both areas, 300 fibroblasts were counted in each high-power field. The significance of proliferative activity of fibroblasts on LNM or DOM was compared with well-known prognostic parameters. Multivariate analyses demonstrated that a MIB-1 labeling index of more than 10% of fibroblasts in the inner area of IDCs significantly increased the relative risk of LNM and hazard rate of DOM (P < 0.001 and P = 0.007, respectively). The present study indicated that the metastatic ability of IDCs is closely dependent on proliferative activity of fibroblasts in the inner area.  相似文献   
7.
1,2-Epoxycyclohexane ( 1 ) was found to behave differently from propylene oxide (PO) in polymerization reactions with organozinc compounds as initiators. A chair-type complex, [Zn-MP]2,2, is the only compound that shows high catalytic activity for both polymerization of 1 and PO, following an anionic coordination mechanism. On the other hand, the polymerization of 1 with ZnEt2 or (EtZnOMe)4 as initiator proceeds according to a cationic mechanism. Cationic polymerization of 1 with ZnEt2 has two modes of termination reaction resulting in the formation of terminal units containing vinyl ether and allyl ether moieties. The initiation and propagation mechanism of 1 by [Zn-MP]2;2 is similar to that of PO, but chain transfer reaction takes place in the polymerization of 1 owing to the low stability of the growing chain end. By using [Zn-MP]2,2 as initiator, it was possible to prepare a block copolymer consisting of an isotactic sequence of monomeric units of PO and a syndiotactic sequence of monomeric units of 1 .  相似文献   
8.
Sulfonated polyrotaxanes (PRx-SO(3)'s), in which sulfonated alpha-cyclodextrins (alpha-CDs) were threaded onto the poly(ethylene glycol) (PEG) segments in a PEG-b-poly(propylene glycol) (PPG)-b-PEG triblock copolymer (Pluronic) capped with benzyloxycarbonyl (Z)-L-phenylalanine (Z-L-Phe), were prepared as a novel surface-modifying biomaterial. Surface modification of the polyurethane (PU) was carried out by blending the PRx-SO(3)'s with a PU solution, followed by solution casting. The incorporated PRx-SO(3)'s led to the enhanced hydrophilicity by changing the surface properties of the PU matrix. Modified PUs showed the stable entrapment of the PRx-SO(3)'s with little extraction into water and enhanced mechanical properties after exposure to water compared to the PU control. The incorporated PRx-SO(3)'s repelled the proteins and kept them from closely approaching the surface areas, prevented platelet activation by thrombin, and effectively repelled bacteria. These results suggest that both the supramolecular structure of the polyrotaxanes and exposure of the sulfonated groups onto the surfaces contribute to these phenomena. Thus, surface modification with PRx-SO(3)'s is suggested to be useful for the fabrication of biocompatible medical devices.  相似文献   
9.
Little is known about the neuropathogenicity of equine herpesvirus-1 (EHV-1) in mice. No neurological signs were observed in 6-day-old mice inoculated intracerebrally with the HH1 strain (HH1) of EHV-1. However,6-day-old mice inoculated intracerebrally with a variant derived by serial passage of HH1 in mouse brain showed severe neurological symptoms and eventually died. Histological analyses were performed on 6-day-old mice inoculated with the neuroadapted HH1 (NHH1) and the parental HH1 strain by the intracerebral, intranasal or intraperitoneal route. All routes of inoculation with NHH1 caused encephalitis, but myelitis was observed only in mice inoculated intraperitoneally. Prominent histological findings were perivascular cuffing sometimes associated with small fibrin thrombi, neuronal and glial degeneration and necrosis, and intranuclear inclusion bodies in neurons, glial cells and ependymal cells. Intracerebral and intranasal inoculation, but not intraperitoneal inoculation, with HH1 induced central nervous system (CNS) lesions that were milder than those in mice inoculated with NHH1. The distribution of viral antigen was more widespread in mice inoculated with NHH1 than with HH1. No viral antigen was detected in the CNS of mice inoculated intraperitoneally with HH1. These results indicate that increased viral multiplication and spreading in the CNS were responsible for the enhanced neurovirulence of NHH1. Although EHV-1 has been considered to be primarily endotheliotropic in horses, both NHH1 and HH1 showed tropism for the parenchymal cells of the CNS in mice, namely neurons, glial cells and ependymal cells.  相似文献   
10.
Malignant phyllodes tumour with a noninvasive ductal carcinoma component   总被引:2,自引:0,他引:2  
 A malignant phyllodes tumour with a noninvasive ductal carcinoma component is reported. The patient was an 80-year-old Japanese woman with a breast tumour detected by routine physical examination. A simple mastectomy was performed. The excised tumour was 10.5×9.4×5.4 cm in size and bulged into the skin with ulceration. The macroscopic appearance was that of a phyllodes tumour. Histologically the tumour consisted mainly of stromal components with a leaf-like structure lined by atypical ductal epithelium. The epithelial component showed gradual evolution to intraductal papillary carcinoma in a few areas. The stromal component was composed mainly of fibrosarcoma with areas of osteosarcoma and rhabdomyosarcoma. Neither stromal invasion of intraductal carcinoma nor transition between the stromal and epithelial elements was seen. Three months after the operation, death occurred, with multiple pulmonary and subcutaneous metastases. This case probably represents malignant change in both the stromal and the epithelial components of a phyllodes tumour. Since the two elements were independent, the possibility that a phyllodes tumour may be one of the origins of true carcinosarcoma is raised. Received: 11 March 1997 / Accepted: 5 May 1997  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