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   14771篇
  免费   1101篇
  国内免费   91篇
耳鼻咽喉   111篇
儿科学   316篇
妇产科学   192篇
基础医学   2127篇
口腔科学   237篇
临床医学   1420篇
内科学   3067篇
皮肤病学   267篇
神经病学   1595篇
特种医学   638篇
外科学   2397篇
综合类   328篇
现状与发展   1篇
一般理论   8篇
预防医学   884篇
眼科学   363篇
药学   984篇
中国医学   29篇
肿瘤学   999篇
  2023年   97篇
  2022年   295篇
  2021年   498篇
  2020年   253篇
  2019年   299篇
  2018年   419篇
  2017年   274篇
  2016年   335篇
  2015年   396篇
  2014年   532篇
  2013年   658篇
  2012年   1043篇
  2011年   1111篇
  2010年   603篇
  2009年   558篇
  2008年   906篇
  2007年   896篇
  2006年   813篇
  2005年   814篇
  2004年   718篇
  2003年   704篇
  2002年   657篇
  2001年   227篇
  2000年   212篇
  1999年   193篇
  1998年   143篇
  1997年   126篇
  1996年   90篇
  1995年   94篇
  1994年   86篇
  1993年   77篇
  1992年   103篇
  1991年   113篇
  1990年   83篇
  1989年   108篇
  1988年   85篇
  1987年   81篇
  1986年   77篇
  1985年   90篇
  1984年   80篇
  1983年   74篇
  1982年   64篇
  1981年   59篇
  1980年   68篇
  1979年   62篇
  1978年   53篇
  1976年   46篇
  1975年   51篇
  1973年   44篇
  1971年   48篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE AND IMPORTANCE: True duplication of the A1 segment of the anterior cerebral artery is extremely rare, as is finding a true A1 segment saccular aneurysm. We report the angiographic and surgical findings of such a case with the additional association of a hypoplastic ipsilateral M1 segment of the middle cerebral artery. CLINICAL PRESENTATION: A 68-year-old man presented with a Hunt and Hess Grade II subarachnoid hemorrhage and symptoms of headache, nuchal rigidity, and facial paresis. INTERVENTION: Angiographic evaluation with superselective exploration revealed a small ruptured aneurysm located on a duplicated hypoplastic A1 segment of the left anterior cerebral artery with associated middle cerebral artery stenosis and secondary early moyamoya changes. Surgical clipping of the aneurysm was performed successfully while sparing the hypoplastic A1 segment. CONCLUSION: A1 aneurysms occurring on a duplicated anterior cerebral artery segment probably develop from a congenital weakness of the parent vessel and increased local shear stress. Superselective angiography was helpful in the preoperative planning and facilitated the decision to treat with surgical clipping instead of embolization.  相似文献   
92.
PURPOSE: Oncolytic herpes simplex viruses (HSVs) may have significant antitumor effects resulting from the direct lysis of cancer cells. HSVs may also be used to express inserted transgenes to exploit additional therapeutic strategies. The ability of an interleukin (IL)-12-expressing HSV to treat squamous cell carcinoma (SCC) by inhibition of tumor angiogenesis is investigated in this study. EXPERIMENTAL DESIGN: A replication-competent, attenuated, oncolytic HSV carrying the murine IL-12 gene (NV1042), its non-cytokine-carrying analog (NV1023), or saline was used to treat established murine SCC flank tumors by intratumoral injection. The expression of secondary antiangiogenic mediators was measured. Angiogenesis inhibition was assessed by in vivo Matrigel plug assays, flank tumor subdermal vascularity, and in vitro endothelial cell tubule formation assay. RESULTS: Intratumoral injections of NV1042 (2 x 10(7) plaque-forming units) into murine SCC VII flank tumors resulted in smaller tumor volumes as compared with NV1023 or saline. IL-12 and IFN-gamma expression in tumors was 440 and 2.2 pg/mg, respectively, at 24 h after NV1042 injection, but both IL-12 and IFN-gamma were undetectable (<0.2 pg/mg) after NV1023 or saline injections. Expression of two antiangiogenesis mediators, monokine induced by IFN-gamma and IFN-inducible protein 10, was elevated after NV1042 treatment. Matrigel plug assays of NV1042-transfected SCC VII tumor cells demonstrated significantly decreased hemoglobin content and microvessel density as compared with NV1023 and PBS. Excised murine flank tumors treated with NV1042 had decreased subdermal vascularity as compared with NV1023 and PBS. Both splenocytes and IL-12 expression by NV1042 were required for in vitro inhibition of endothelial tubule formation. CONCLUSIONS: IL-12 expression by an oncolytic herpes virus enhances therapy of SCC through antiangiogenic mechanisms. Strategies combining HSV oncolysis with angiogenesis inhibition merit further investigation for potential clinical application.  相似文献   
93.
BACKGROUND: Sodium picosulphate (Picolax) is considered by most British surgeons as standard preparation for colonoscopy and elective surgery. Oral sodium phosphate may be better tolerated and more efficient as bowel preparation. METHODS: A randomized trial was performed to compare oral sodium phosphate (n = 76) with Picolax (n = 77) as bowel preparation for elective colorectal surgery. A parallel study randomized colonoscopy patients to sodium phosphate (n = 51) or Picolax (n = 52). Patient acceptability was measured for seven symptoms with a linear analogue score. Quality of preparation was graded by the surgeon and faecal residue was measured in resection specimens. During colonoscopy, bowel preparation has graded 0-24 using an endoscopic score. RESULTS: Abdominal pain, nausea, vomiting, embarrassment, fear and fatigue did not differ significantly between the groups. Surgeons grade of quality was judged poor or awful in 5 of 76 in the sodium phosphate group (9%) compared with 13 of 73 in the Picolax group (18%, p = 0.084). Mean faecal residue in the resection specimen was 0.1 g/cm after sodium phosphate compared with 0.45 g/cm after Picolax (p < 0.01). The endoscopic score was significantly lower using sodium phosphate (2.0 +/- 2.2) than picolax (3.1 +/- 2.9; p < 0.05). CONCLUSIONS: These results suggest that oral sodium phosphate is well tolerated and superior to Picolax in elective colorectal surgery and colonoscopy.  相似文献   
94.
This article summarizes principal findings from a conference convened by the American Cancer Society in June 1998 to examine the health risks of cigar smoking. State-of-the-science reports were presented and 120 attendees (representing government and private agencies, academia, health educators, and tobacco control experts) participated in panels and summary development discussions. The following conclusions were reached by consensus: (1) rates of cigar smoking are rising among both adults and adolescents; (2) smoking cigars instead of cigarettes does not reduce the risk of nicotine addiction; (3) as the number of cigars smoked and the amount of smoke inhaled increases, the risk of death related to cigar smoking approaches that of cigarette smoking; (4) cigar smoke contains higher concentrations of toxic and carcinogenic compounds than cigarettes and is a major source of fine-particle and carbon monoxide indoor air pollution; and (5) cigar smoking is known to cause cancers of the lung and upper aerodigestive tract. JAMA. 2000;284:735-740  相似文献   
95.
To determine the postoperative incidence, extent and recurrence rate of exostoses of the external auditory canal in a cohort of patients involved in different water sports. A cross‐sectional study of 31 patients (46 ears), with exostoses treated by surgery in the Royal Cornwall Hospital between 1980 and 1999. A questionnaire was used to obtain information about the type of water exposure pre‐ and postoperatively. The extent of recurrent stenosis was assessed. The mean postoperative time interval was 10 years (sd = 4.5 years). The degree of stenosis was assessed as: minimal (<30%) in 42.6%, moderate (30–60%) in 31% and severe (>60%) in 25% of ears. The Cox regression model was used to identify factors associated with a reduction in the recurrence rate of stenosis. The use of ear plugs was highly significant (P = 0.015), as was the age of the patient at the time of operation (P = 0.004), i.e. the older the patient, the faster recurrent disease developed. There was no evidence to show that either the type or seasonal pattern of water sport activity influenced recurrence of the disease postoperatively, although preoperatively, the stenosis was more marked in association with surfing and sailing. Exostoses developed faster preoperatively in those who were in the water all year round rather than just the summer months. Of five patients who stopped water sport activity completely after surgery, four of them developed significant recurrent exostoses (>50% stenosis).  相似文献   
96.
PURPOSE: To explore the safety and therapeutic activity of combination anti-B-cell monoclonal antibody therapy in non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS: Twenty-three patients with recurrent B-cell lymphoma received anti-CD22 epratuzumab 360 mg/m(2) and anti-CD20 rituximab 375 mg/m(2) monoclonal antibodies weekly for four doses each. Sixteen patients had indolent histologies (15 with follicular lymphoma) and seven had aggressive NHL (all diffuse large B-cell lymphoma [DLBCL]). Indolent patients had received a median of one (range, one to six) prior treatment, with 31% refractory to their last therapy and 81% with high-risk Follicular Lymphoma International Prognostic Index scores. Patients with DLBCL had a median of three (range, one to eight) prior regimens (14% resistant to last treatment) and 71% had high intermediate-risk or high-risk International Prognostic Index scores. All patients were rituximab na?ve. RESULTS: Treatment was well tolerated, with toxicities principally infusion-related and predominantly grade 1 or 2. Ten (67%) patients with follicular NHL achieved an objective response (OR), including nine of 15 (60%) with complete responses (CRs and unconfirmed CRs). Four of six assessable patients (67%) with DLBCL achieved an OR, including three (50%) CRs. Median time to progression for all indolent NHL patients was 17.8 months. CONCLUSION: The full-dose combination of epratuzumab with rituximab was well tolerated and had significant clinical activity in NHL, suggesting that this combination should be tested in comparison with single-agent treatment.  相似文献   
97.
98.
99.
This study aimed to investigate the influence of silicone oil on the retinal nerve fiber layer (RNFL) thickness in patients with primary rhegmatogenous retinal detachment who underwent vitreoretinal surgery. The study included 47 patients (eyes), who underwent a pars plana vitrectomy with the silicone oil tamponade. The control group included unoperated eye of all participants. Spectral-domain optical coherence tomography (SD-OCT) was used for the measurements of peripapilar and macular RNFL thickness. The average peripapillary RNFL thickness was significantly higher in the silicone oil filled eyes during endotamponade and after its removal. The eyes with elevated IOP had less thickening of the RNFL in comparison to the eyes with normal IOP. Central macular thickness and macular volume were decreased in the silicone oil filled eyes in comparison to the control eyes. In conclusion, silicone oil caused peripapilar RNFL thickening in the vitrectomized eyes during endotamponade and after silicone oil removal.  相似文献   
100.
A recent study showed that tetrahydrofuran (THF), a widely used solvent, is carcinogenic in experimental animals. Despite its carcinogenic activity, there is a paucity of information regarding cellular toxicity, biomolecular damage, and genotoxicity induced by THF. We describe here the structural characterization of adducts produced by the reaction of oxidized THF with 2'-deoxyguanosine (dGuo-THF 1 and dGuo-THF 2), 2'-deoxyadenosine (dAdo-THF), and 2'-deoxycytidine (dCyd-THF). Adducts were isolated from in vitro reactions by reverse-phase HPLC and fully characterized on the basis of spectroscopic measurements. The stable derivatives obtained by the reduction of adducts with NaBH(4) (the case of dGuo-THF 1, dCyd-THF, and dAdo-THF) and the stable adduct dGuo-THF 2 were used as standards for optimization of chromatographic separations for adduct detection in DNA through HPLC/ESI/MS-MS. Using this methodology, we successfully detected the four adducts in calf thymus DNA reacted with oxidized THF. The present study also provides evidence that rat liver microsomal monooxigenases oxidize THF to the reactive electrophilic compounds that are able to damage the DNA molecule, as indicated by a significant increase in adduct dGuo-THF 1 level when NADPH was added to the THF/microsomes/dGuo incubation mixtures. Our data point to DNA-THF adducts as possible contributing factors to the toxicological effects of THF exposure.  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