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   5355篇
  免费   392篇
  国内免费   41篇
耳鼻咽喉   71篇
儿科学   210篇
妇产科学   130篇
基础医学   781篇
口腔科学   51篇
临床医学   758篇
内科学   929篇
皮肤病学   89篇
神经病学   477篇
特种医学   231篇
外科学   675篇
综合类   73篇
一般理论   3篇
预防医学   452篇
眼科学   129篇
药学   365篇
中国医学   4篇
肿瘤学   360篇
  2021年   80篇
  2020年   51篇
  2019年   87篇
  2018年   84篇
  2017年   69篇
  2016年   68篇
  2015年   102篇
  2014年   102篇
  2013年   177篇
  2012年   228篇
  2011年   241篇
  2010年   141篇
  2009年   131篇
  2008年   200篇
  2007年   227篇
  2006年   231篇
  2005年   209篇
  2004年   232篇
  2003年   195篇
  2002年   192篇
  2001年   164篇
  2000年   160篇
  1999年   183篇
  1998年   64篇
  1997年   50篇
  1996年   60篇
  1995年   59篇
  1994年   44篇
  1993年   40篇
  1992年   112篇
  1991年   104篇
  1990年   119篇
  1989年   104篇
  1988年   90篇
  1987年   88篇
  1986年   101篇
  1985年   86篇
  1984年   64篇
  1983年   50篇
  1982年   42篇
  1981年   42篇
  1979年   83篇
  1978年   58篇
  1977年   54篇
  1976年   49篇
  1974年   47篇
  1973年   55篇
  1972年   49篇
  1969年   38篇
  1967年   36篇
排序方式: 共有5788条查询结果,搜索用时 15 毫秒
81.
PURPOSE: This phase III randomized trial evaluated survival as well as neurologic and neurocognitive function in patients with brain metastases from solid tumors receiving whole-brain radiation therapy (WBRT) with or without motexafin gadolinium (MGd). PATIENTS AND METHODS: Patients were randomly assigned to 30 Gy of WBRT +/- 5 mg/kg/d MGd. Survival and time to neurologic progression determined by a blinded events review committee (ERC) were coprimary end points. Standardized investigator neurologic assessment and neurocognitive testing were evaluated. RESULTS: Four hundred one (251 non-small-cell lung cancer) patients were enrolled. There was no significant difference by treatment arm in survival (median, 5.2 months for MGd v 4.9 months for WBRT; P =.48) or time to neurologic progression (median, 9.5 months for MGd v 8.3 months for WBRT; P =.95). Treatment with MGd improved time to neurologic progression in patients with lung cancer (median, not reached for MGd v 7.4 months for WBRT; P =.048, unadjusted). By investigator, MGd improved time to neurologic progression in all patients (median, 4.3 months for MGd v 3.8 months for WBRT; P =.018) and in lung cancer patients (median, 5.5 months for MGd v 3.7 months for WBRT; P =.025). MGd improved neurocognitive function in lung cancer patients. CONCLUSION: The overall results did not demonstrate significant differences by treatment arm for survival and ERC time to neurologic progression. Investigator neurologic assessments demonstrated an MGd treatment benefit in all patients. In lung cancer patients, ERC- and investigator-determined time to neurologic progression demonstrated an MGd treatment benefit. MGd may improve time to neurologic and neurocognitive progression in lung cancer.  相似文献   
82.
The transplantation of chondrogenic cells in a supportive carrier structure proved to be a promising alternative for the treatment of cartilage defects. In the study presented we focused on the transplantation of allogeneic chondrocytes in a biodegradable polymer scaffold (PGLA/Polydioxanon) in articular cartilage defects in a rabbit defect model. Isolated allogeneic chondrocytes embedded in a PGLA polymer scaffold were transplanted into osteochondrogenic defects of the patellar groove and compared with empty defects and transplants of polymer scaffolds without cells. The histological and histochemical analysis was performed after 4 and 12 weeks. The transplant integration and the architecture of the newly formed cartilage were evaluated with a semiquantitative score. After 4 weeks the development of a hyaline-like cartilage tissue of the cell-polymer-transplants was observed, after 12 weeks the defects were nearly completely filled with hyaline-like cartilage. The biodegradation of the polymer construct did not affect the histological structure of the transplant area. Defects of the groups with empty defect and polymer transplants without cells revealed no or insufficient healing indices. The study demonstrated that biodegradable polymers served as suitable carriers for the chondrocyte transplantation, which is due to the in-vitro establishment of a semi-solid cartilage transplant and the resulting effective transplant fixation into the defect. In-vivo the polymer cell transplants seem to provide a supportive microenvironment for the development of hyaline cartilage. The controlled release of morphogenic factors or bioactive molecules and the use of pluripotent mesenchymal progenitor cells opens new perspectives for the optimization of cartilage repair procedures.  相似文献   
83.
Purpose: Cell cycle-related events in CCRF-CEM lymphocytic leukemia cells were examined subsequent to inhibition of thymidylate synthase (TS) or GAR formyltransferase (GARFT) and prior to cell death or stasis. Methods: Cell populations were treated with the GARFT inhibitors 6R-5,10-dideazatetrahydrofolate (lometrexol) or LY309887, the TS inhibitor ZD1694, or the multitargeted antifolate LY231514. DNA content, nucleoside precursor incorporation and proliferating cell nuclear antigen (PCNA) expression as functions of drug treatment were assessed by multiparameter flow cytometry. Cellular respiration was measured by MTT analysis and apoptosis was detected by extraction of DNA fragments. Results: Cell populations treated for up to 96 h with lometrexol or LY309887 did not replicate and maintained a cell cycle distribution with distinct G1, S and G2/M regions. The number of S phase cells in treated populations was slightly elevated relative to control as measured by DNA content and PCNA. However, these cells were unable to incorporate 5-bromodeoxyuridine (BrdU). Throughout treatment, cells incubated with GARFT inhibitors maintained intact membranes and respired at a level comparable to untreated cells. In contrast, ZD1694 as well as LY231514, induced synchronization of the treatment population at the G1/S interface within 12 h of drug addition. This was followed by synchronous entry of the population into S phase. After 24 h of treatment, more than 90% of the cells were capable of incorporating BrdU and stained positive for PCNA. DNA fragmentation occurred in cells treated with ZD1694 or LY231514 but not in those treated with GARFT inhibitors. In addition, the viable cells remaining after 24–48 h of treatment with ZD1694 or LY231514 were respiring at twice the level of untreated cells. Conclusion: These results demonstrate that the distinct endpoints of GARFT and TS inhibition are preceded by distinct cell cycle and metabolic alterations. Received: 1 April 1996 / Accepted: 5 September 1996  相似文献   
84.
85.
We report on the case of a 9-year-old girl who presented vaginal bleeding which led to the diagnosis of vaginal hemangioma. Such localisation is rare, and requires a clinical follow-up by vaginoscopy. A spontaneous regression can be expected but, at this time, the progress of puberty and future fertility are unknown.  相似文献   
86.
Polygonum multiflorum stilbeneglycoside (PMS) is a water-soluble fraction of Polygonum multiflorum Thunb. , one of the most famous tonic traditional Chinese medicines, that has protective effects on the cardiovascular system. The purpose of the present study is to elucidate the effects of PMS on macrophage-derived foam cell functions and the reduction of severity of atherosclerosis in hypercholesterolemic New Zealand White (NZW) rabbits. NZW rabbits were fed for 12 weeks with a normal diet, a high cholesterol diet, or a high cholesterol diet associated with irrigation with different doses of PMS (25, 50, or 100 mg/kg). Treatment of NZW rabbits fed with high cholesterol diet with 100 mg/kg PMS attenuated the increase in plasma cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and plasma triglyceride. Treatment with 50 and 100 mg/kg PMS caused 43% and 60% decrease in atherosclerotic lesioned area ratio to total surface area, respectively. In U937 foam cells, PMS could decrease the high expression of intercellular adhesion molecule (ICAM)-1 protein and the vascular endothelial growth factor (VEGF) protein levels in the medium induced by oxidized lipoprotein when analyzed by flow cytometry. The results proved that PMS is a powerful agent against atherosclerosis and that PMS action could possibly be through the inhibition of the expression of ICAM-1 and VEGF in foam cells.  相似文献   
87.
Chromosome aberrations have a major role in pediatric acute lymphoblastic leukemia (ALL) risk assignment. The Children's Cancer Group (CCG) and the Pediatric Oncology Group (POG) independently assessed the significance of trisomy for chromosomes 4, 10, and 17 in National Cancer Institute (NCI) Standard- and High-Risk ALL. Data from 1582 (CCG) and 3902 (POG) patients were analyzed. Eight-year event-free survivals (EFS) of 91% (CCG) and 89% (POG) (P < 0.001) were achieved in patients assigned to NCI Standard Risk whose leukemic cells had simultaneous trisomies 4, 10, and 17. Both groups showed the degree of favorable prognostic importance increased with the actual number of favorable trisomies. POG analyses also demonstrated hyperdiploidy (> or =53 chromosomes) was less of an independently significant prognostic factor in the absence of these key trisomies. This finding supported conclusions from previous CCG and POG studies that specific trisomies are more important than chromosome number in predicting outcome in pediatric B-precursor ALL. In NCI Higher Risk patients, the number of favorable trisomies was not prognostically significant, but showed the same trend. Moreover, specific trisomies 4, 10, and 17 remain associated with favorable prognosis in Standard-Risk B-precursor ALL, even in the context of very different treatment approaches between the groups.  相似文献   
88.
PURPOSE: This study examined a pretarget radioimmunotherapy strategy for treatment of an i.p. tumor model (LS174T). EXPERIMENTAL DESIGN: The strategy used regional administration (i.p.) of a novel targeting molecule composed of four CC49 anti-tumor-associated glycoprotein 72 (TAG-72) single-chain antibodies linked to streptavidin as a fusion protein (CC49 fusion protein); 24 hours later, a synthetic clearing agent was administered i.v. to produce hepatic clearance of unbound CC49 fusion protein/synthetic clearing agent complexes. Four hours later, a low molecular weight radiolabeled reagent composed of biotin conjugated to the chelating agent 7,10-tetra-azacyclododecane-N,N',N',N'-tetraacetic acid (DOTA) complexed with (111)In-, (90)Y-, or (177)Lu-DOTA-biotin was injected. RESULTS: Radiolocalization to tumor sites was superior with i.p. administration of radiolabeled DOTA-biotin as compared with i.v. administration. Imaging and biodistribution studies showed excellent tumor localization of radioactivity with (111)In- or (177)Lu-DOTA-biotin. Tumor localization of (111)In-DOTA-biotin was 43% ID/g and 44% ID/g at 4 and 24 hours with the highest normal tissue localization in the kidney with 6% ID/g at 48 and 72 hours. Therapy studies with (90)Y-DOTA-biotin at doses of 400 to 600 microCi or (177)Lu-DOTA-biotin at doses of 600 to 800 microCi produced significant prolongation of survival compared with controls (P = 0.03 and P < 0.01). CONCLUSIONS: Pretarget radioimmunotherapy using regional administration of CC49 fusion protein and i.p. (90)Y- or (177)Lu-DOTA-biotin represents a successful therapeutic strategy in the LS174T i.p. tumor model and this strategy may be applicable to human trials in patients with i.p. ovarian cancer.  相似文献   
89.
Specific binding of iodine 125-labeled epidermal growth factor was measured in membrane homogenates of third-trimester and term human placentas of male and female fetuses. All placentas (n = 35) generated curvilinear Scatchard plots, and all placentas had similar equilibrium dissociation constants for both high-affinity (210 pmol/L) and low-affinity (830 pmol/L) binding sites. Mean maximum number of available binding sites of term placentas from male fetuses (330 +/- 110 fmol/mg protein; n = 11) was significantly higher (p less than 0.001) than that of female fetuses (170 +/- 80 fmol/mg protein, n = 13). Occupation of epidermal growth factor receptors by endogenous epidermal growth factor could not account for the difference in levels of epidermal growth factor binding. Kendall's rank order correlation test demonstrated a significant positive correlation of the gestational age in weeks with the maximum number of epidermal growth factor receptors in placentas from male fetuses (p less than 0.002; T = 0.527; n = 17) and female fetuses (p less than 0.01; T = 0.404; n = 18). These results indicate that there is a sexual dimorphism in the level of epidermal growth factor receptors in placentas of male and female fetuses during the third trimester and that the level of epidermal growth factor receptors increases during the third trimester for placentas of both male and female fetuses.  相似文献   
90.
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