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   7196篇
  免费   507篇
  国内免费   37篇
耳鼻咽喉   61篇
儿科学   163篇
妇产科学   77篇
基础医学   1119篇
口腔科学   71篇
临床医学   841篇
内科学   1937篇
皮肤病学   131篇
神经病学   627篇
特种医学   241篇
外科学   1035篇
综合类   21篇
预防医学   532篇
眼科学   45篇
药学   382篇
中国医学   9篇
肿瘤学   448篇
  2023年   31篇
  2022年   48篇
  2021年   190篇
  2020年   102篇
  2019年   175篇
  2018年   195篇
  2017年   118篇
  2016年   129篇
  2015年   192篇
  2014年   265篇
  2013年   329篇
  2012年   540篇
  2011年   521篇
  2010年   313篇
  2009年   278篇
  2008年   476篇
  2007年   479篇
  2006年   468篇
  2005年   474篇
  2004年   451篇
  2003年   447篇
  2002年   422篇
  2001年   85篇
  2000年   88篇
  1999年   115篇
  1998年   109篇
  1997年   62篇
  1996年   56篇
  1995年   58篇
  1994年   52篇
  1993年   23篇
  1992年   41篇
  1991年   42篇
  1990年   49篇
  1989年   42篇
  1988年   40篇
  1987年   33篇
  1986年   24篇
  1985年   16篇
  1984年   17篇
  1983年   10篇
  1982年   12篇
  1981年   10篇
  1980年   7篇
  1979年   12篇
  1978年   8篇
  1975年   8篇
  1973年   11篇
  1970年   11篇
  1967年   7篇
排序方式: 共有7740条查询结果,搜索用时 31 毫秒
981.
982.
Some clinical studies in liver transplantation have recently reported safety advantages and similar acute rejection rates with early steroid withdrawal. The aim of this study was to evaluate the efficacy and safety of an immunosuppressive regimen with steroid withdrawal at day 14. A multicenter, 1-year, comparative, double blind, placebo-controlled study was performed. Patients undergoing a first cadaveric liver transplantation were recruited and all received basiliximab + cyclosporine + intravenous methylprednisolone. Patients without severe postoperative complications were randomized at day 7 to receive a maintenance regimen with Neoral (cyclosporine) + prednisolone (group 1) or without steroids (Neoral + placebo; group 2), after a 7-day blinded oral steroid tapering period. A total of 174 patients were randomized at day 7 (group 1: n = 90; group 2: n = 84). The incidence of biopsy-confirmed and treated acute rejection at 6 months was 38.1% in group 2 vs. 24.4% in group 1 (P = .03) with a trend for a higher incidence of Grade II / III acute rejection (28.6% vs. 18.9%; P = .12). Changes from baseline were similar with regard to metabolic parameters (glycemia, total cholesterol, and triglycerides). A trend toward a better glucose tolerance was observed, as fewer patients received an antidiabetic treatment in the placebo group (2 vs. 10). In conclusion, this first double-blind, placebo-controlled study of steroid withdrawal at day 14 showed a higher incidence of acute rejection, only balanced by a trend of a lower need of antidiabetic treatment.  相似文献   
983.
Acute splenoportal and superior mesenteric venous thrombosis were diagnosed on sonography and computed tomography (CT) in six patients. Sonography demonstrated the presence of echoic material filling the involved vessels in all patients. Precontrast CT scans demonstrated an increased, intra luminal density of the clots in four patients with splenoportal thrombosis. However, in two cases of superior mesenteric venous thrombosis, no hyperdensity was observed within the lumens. Nevertheless, the clots were always visualized as low-density regions in the vessel lumens after bolus injection. Intravenous anticoagulant therapy was started immediately after the diagnosis. All patients were evaluated twice a week with sonography and/or CT until recanalization occurred. The patency of the previously involved vessels was assessed from 6 days to 4 weeks after the acute episode (average time of recanalization: 17 days) without development of collateral pathways. It is concluded that, in the absence of clinical signs of a life-threatening process, a conservative management of acute splanchnic thrombosis can be successfully achieved by (1) early diagnosis, (2) efficacious intravenous anticoagulant therapy, (3) careful imaging follow-up of these patients by sonography and/or CT during the acute phase and, finally, (4) by an extensive search for a hypercoagulable state.  相似文献   
984.
This study evaluates the efficiency of fluid-air exchange on the reattachment of the retina and clarifies the possibility that a posterior retinotomy is a cause for intra- and postoperative complications. A consecutive series of 211 eyes with retinal detachments due to P.V.R. (47%), diabetic traction, perforating trauma, macular hole or giant tears is presented. All eyes underwent pars plana vitrectomy, fluid-air exchange, internal drainage of subretinal fluid, laser endophotocoagulation and scleral buckling of the tears; 56% of the eyes were phakic and 55% underwent a posterior retinotomy, 54% underwent tamponade with C3F8 and 46% with silicone oil. Intraoperatively the retina was completely flattened in 91% cases. The causes of incomplete reattachment were residual membranes (6.6%), poor visualization (1.4%) and suprachoroidal hemorrhage (1%). These complications were isolated as being the cause of the bad final results (p < 0.001). Postoperatively, the retina remained attached in 66% of cases after the first procedure and with further surgery in 81% (mean follow up 16 months). Best corrected visual acuity was improved in 73% of eyes, unchanged in 17%, and worse in 10%. Complications were retraction of the retinotomy site in 3 cases and peripheral choroidal hemorrhage in 4 cases. We concluded that fluid air exchange with internal subretinal fluid drainage was an efficient and safe technique even if a posterior retinotomy was necessary.  相似文献   
985.
A case is reported of ectopic pregnancy occurring within an ovary with the morphologic appearance of polycystic ovary syndrome (PCOS). The hyperandrogenism and elevated LH/FSH ratio characteristic of PCOS were noted 2 months after removal of the ovarian gestation. The thickened ovarian cortex of the PCOS ovary and a defect in oocyte-cumulus complex detachment within the follicle are suggested as possible factors contributing to intraovarian fertilization in PCOS.  相似文献   
986.
987.
Because the use of radioactive fibrinogen uptake test (FUT) has become questionable both for ethical (risk of virus transmission) and technical (lack of sensitivity) reasons, we investigated the potential value of two alternative methods for screening of asymptomatic deep venous thrombosis following elective digestive surgery: liquid crystal contact thermography (LCCT) and measurement of plasma concentration of D-dimer (DD), as compared with bilateral ascending phlebography. Out of 194 patients, 185 underwent phlebography on the 8th (0-19, median and range) postoperative day. Despite prophylaxis with low-molecular-weight heparin and elastic stockings, DVT was detected on phlebography in 58 legs of 45 patients. Sensitivity of LCCT with respect to the presence of DVT was 55% (n = 184 patients) or 28% (n = 368 legs) with a specificity of 67% and 82%, respectively. These poor performances were obtained despite a good interobserver agreement for the LCCT assessments (overall kappa coefficient of 0.66 between three experts). The most accurate cut-off of DD for discriminating patients with or without DVT was 3,000 micrograms/l, as determined by ROC curve analysis. Sensitivity of a DD level of more than 3,000 micrograms/l for the presence of phlebographically documented DVT on the 8th postoperative day was 89% for a specificity of 48%. Thus, LCCT cannot be used for screening of postoperative, mainly asymptomatic DVT following general surgery. On the other hand, measurement of plasma DD may be useful for initial screening, a negative result (level less than 3,000 micrograms/l) allowing to exclude DVT (negative predictive value of 93%) and a positive result (positive predictive value of 35%) requiring confirmation by phlebography.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
988.
Introduction For liver transplant candidates with hepatocellular carcinoma (HCC), the ability of neoadjuvant transarterial chemoembolization (TACE) to improve outcomes remains unproven. The objective of our study was to determine if there was a specific time interval where neoadjuvant TACE would decrease the number of HCC patients removed from the pretransplant waitlist. Materials and Methods A decision model was developed to simulate a randomized trial of neoadjuvant treatment with TACE vs. no TACE in 600 virtual patients with HCC and cirrhosis. Transition probabilities for TACE morbidity (1 ± 1%), TACE response rates (30 ± 20%), and disease progression (7 ± 7% per month) were assigned by systematic review of the literature (18 reports). Sensitivity analyses were performed to determine time thresholds where TACE would decrease the number of delisted patients. Results TACE treatment had statistical benefit at waitlist time breakpoints of 4 and 9 months (P < 0.05). When waitlist times were less than 4 months, waitlist attrition was similar (20% vs. 34%, P = 0.08). When waitlist times exceed 9 months, waitlist dropout rates re-equilibrated (33% vs. 46%, P = 0.06). Review of the current literature determined that only those studies reporting on patients with waitlist times between 4 and 9 months found a benefit to neoadjuvant TACE. Conclusions This analysis indicates that the benefit of neoadjuvant TACE may be limited to those patients transplanted from 4 to 9 months from first TACE. These data may help transplant programs to tailor TACE treatments based on predicted waitlist times to achieve optimal resource utilization and improved organ allocation efficiency. Presented at the 7th World Congress of the International Hepato Pancreato Biliary Association Meeting, September 6, 2006, Edinburgh, Scotland.  相似文献   
989.
Calcofluor white 2MR, modified trichrome blue, and indirect immunofluorescent antibody (IFA) staining methods were evaluated and compared for detecting microsporidia in stool. Serial 10-fold dilutions of Encephalitozoon (Septata) intestinalis were prepared in three formalinized stool specimens or in Tris-buffered saline. Ten-microliter aliquots were smeared onto glass slides, fixed with methanol, stained, and read by at least three individuals. The results indicated that the calcofluor stain was the most sensitive method, required approximately 15 min to perform, but did generate some false-positive results due to similarly staining small yeast cells. The modified trichrome blue stain was nearly as sensitive as the calcofluor stain and allowed for easier distinction between microsporidia and yeast cells. This stain, however, required approximately 60 min to perform. The IFA stain with polyclonal murine antiserum against E. intestinalis was the least sensitive of the methods and required approximately 130 min to perform. The lower limit of detection with the calcofluor and modified trichrome stains was a concentration of about 500 organisms in 10 microliters of stool to detect one microsporidian after viewing 50 fields at a final magnification of x1,000. Reliability was also addressed by use of 74 stool, urine, and intestinal fluid specimens, 50 of which were confirmed for the presence of microsporidia by transmission electron microscopy (TEM). All TEM-positive specimens were detected by calcofluor and modified trichrome blue staining. Ten specimens were not detected by the IFA stain. An additional seven TEM-negative specimens were read positive for microsporidia with the calcofluor stain, and of these, five also were read positive with the modified trichrome blue stain. The resulting diagnostic paradigm was to screen specimens with the calcofluor stain and to confirm the results with the modified trichrome stain. IFA, which was less sensitive, may become useful for microsporidian species identification as specific antibodies become available.  相似文献   
990.
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