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   14420篇
  免费   800篇
  国内免费   118篇
耳鼻咽喉   188篇
儿科学   291篇
妇产科学   187篇
基础医学   2210篇
口腔科学   351篇
临床医学   1309篇
内科学   2741篇
皮肤病学   529篇
神经病学   1139篇
特种医学   632篇
外科学   2061篇
综合类   55篇
一般理论   2篇
预防医学   628篇
眼科学   376篇
药学   1329篇
中国医学   188篇
肿瘤学   1122篇
  2023年   74篇
  2022年   253篇
  2021年   511篇
  2020年   279篇
  2019年   360篇
  2018年   403篇
  2017年   342篇
  2016年   488篇
  2015年   647篇
  2014年   752篇
  2013年   825篇
  2012年   1308篇
  2011年   1188篇
  2010年   730篇
  2009年   632篇
  2008年   837篇
  2007年   861篇
  2006年   740篇
  2005年   671篇
  2004年   555篇
  2003年   448篇
  2002年   418篇
  2001年   310篇
  2000年   294篇
  1999年   219篇
  1998年   72篇
  1997年   61篇
  1996年   39篇
  1995年   55篇
  1994年   28篇
  1993年   21篇
  1992年   84篇
  1991年   69篇
  1990年   83篇
  1989年   69篇
  1988年   64篇
  1987年   48篇
  1986年   50篇
  1985年   45篇
  1984年   30篇
  1983年   33篇
  1981年   24篇
  1980年   19篇
  1979年   37篇
  1978年   44篇
  1977年   25篇
  1976年   20篇
  1975年   30篇
  1974年   27篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
PURPOSE: Flavopiridol is a cyclin-dependent kinase inhibitor with preclinical activity against prostate cancer cell lines. A Phase II trial was conducted to determine the activity of flavopiridol in patients with metastatic hormone-refractory prostate cancer. EXPERIMENTAL DESIGN: A total of 36 patients was enrolled from several institutions and treated with a 72-h continuous infusion of flavopiridol every 14 days at the eventual starting dose of 40 mg/m(2)/day. Dose escalation up to 60 mg/m(2)/day was permitted if no significant toxicity was observed. Responses were assessed every 12 weeks. Only those patients completing four courses of the 72-h infusion were considered evaluable for response because the primary objective was to determine progression-free survival at 6 months given the cytostatic nature of the agent. RESULTS: This study was conducted in a two-stage fashion. During the first stage, at least 20 evaluable patients needed to be enrolled to assess response. There were 22 of 36 patients evaluable for response. No objective responses were observed. Only 4 patients had stable disease for 16, 26, 29, and 48 weeks, respectively, stopping the trial by design as only 3 of 22 (14%) of the patients met the 6-month progression-free survival end point. The most common toxicities were diarrhea (grade 1 and 2) and nausea, although some grade 3 and 4 diarrhea (11 and 6%, respectively) were evident. CONCLUSIONS: Flavopiridol has disappointing single-agent activity in hormone-refractory prostate cancer when administered at this dose and schedule. Its use in prostate cancer should be reserved for evaluation in combination therapies or alternative schedules.  相似文献   
132.
133.
BACKGROUND: Since 1990, we have treated patients with advanced nasopharyngeal cancer with induction chemotherapy and concomitant chemoradiotherapy. We herein report the results of our experience. PATIENTS AND METHODS: From 1990 to 1999, 27 patients with locoregionally advanced nasopharyngeal cancer were treated with induction chemotherapy followed by concomitant chemoradiotherapy. Using the American Joint Committee on Cancer's 1992 stage classification, all patients were stage III (11%) or IV (89%). By histology, 63% were poorly differentiated carcinoma and 37% squamous cell carcinoma. The median age was 42 years. Three cycles of induction chemotherapy consisting of cisplatin, 5-fluorouracil, leucovorin and interferon-alpha2b were administered, followed by concomitant chemoradiotherapy consisting of seven cycles of 5-fluorouracil, hydroxyurea and once-daily radiotherapy (FHX) on a week-on week-off schedule. The median radiotherapy dose was 70 Gy. RESULTS: Clinical response to induction chemotherapy was 100%, 54.2% complete response (CR) and 45.8% partial response. Clinical and/or pathological (37% of all patients had post-treatment biopsy with or without neck dissection) CR after FHX was 100%. At a median follow-up of 52 months, three failures were observed. Two patients have died of disease, one of local failure and one of distant metastases. One patient is alive with an isolated rib metastasis. At 5 years, actuarial locoregional control is 93% and actuarial distant control 92%. The overall survival at 3 and 5 years is 88% and 77%, respectively. Four patients died of unrelated illnesses and had no evidence of disease with respect to their nasopharyngeal cancer. The progression-free survival at 3 and 5 years is 92% and 86%, respectively. Thirty-three per cent of patients required a reduction in the chemotherapy dose due to acute toxicity. Chronic toxicity was not observed, with all patients able to eat orally without dietary restrictions. CONCLUSIONS: Treatment of locoregionally advanced nasopharyngeal cancer with induction chemotherapy followed by concomitant chemoradiotherapy resulted in excellent overall survival with acceptable toxicity. These results are encouraging and warrant further investigation of intensified approaches.  相似文献   
134.
135.
Won CL  Oh YS 《Brain research》2000,887(2):7275-258
It is well known that increased cAMP levels in cultured astrocytes can convert flat polygonal shaped astrocytes into process-bearing, stellate astrocytes. In this study, we have examined the possible existence of astrocyte regional heterogeneity in morphological changes in response to cAMP stimulation. Primary astrocyte cultures were prepared from six different regions of neonatal rat brains, including cerebral cortex, hippocampus, brain stem, mid brain, cerebellum, and hypothalamus. After about 2 weeks in culture, the astrocyte culture medium was changed to DMEM containing various concentrations of 8-CPT-cAMP, a membrane permeable cAMP analog, for 2 h. We found that 250 microM 8-CPT-cAMP produced a maximum effect causing >95% stellation in all regional astrocytes except hypothalamic astrocytes (56% stellation). At lower cAMP concentrations, cell stellation most effectively occurred in cerebellar astrocytes. To examine further the regional heterogeneity of astrocyte morphological changes, glutamate was added together with 8-CPT-cAMP to block cAMP-induced astrocyte stellation. Interestingly, glutamate blockage on cAMP-induced astrocyte stellation was brain region-specific in that cerebral and hippocampal astrocytes were effectively blocked by glutamate when compared to other regional astrocytes. Furthermore, glutamate inhibited isoproterenol-induced astrocyte stellation in a region-specific manner similarly as in cAMP-induced stellation. The present study demonstrates that astrocytes derived from different regions of the neonatal rat brain maintain different levels of morphological plasticity in culture.  相似文献   
136.
PURPOSE: Tumor necrosis factor-alpha (TNF-alpha) is involved in oncogenesis of several cancers. The purpose of this study was to investigate whether genotype changes of TNF-alpha promoter regions (-238, -308) and at the 488 region are associated with human prostate cancer. MATERIALS AND METHODS: The DNA from 73 cases of human prostate cancer was analyzed by allele-specific polymerase chain reaction to characterize the genotype changes of three regions of the TNF-alpha gene in prostate cancer patients. We also determined the genotype frequency in these patients. The relative risk of variant genotype was calculated by comparing with our previous data from healthy controls. RESULTS: Genetic changes were detected in 15.1% (11/73) of prostate cancer samples at 488 region of TNF-alpha. Seventy-three percent (53/73) of the patients showed genotype GA at -308 region of TNF-alpha. Genotype GA at 488 region in TNF-alpha was observed in 73% (53/73) of the cancer and 71% (52/73) of the normal tissue. The relative risks of incidence for prostate cancer was 14-fold higher in people with genotype GA at -308 region of TNF-alpha. The relative incidence for prostate cancer was a 17-fold higher in-patient with genotype GA at 488 region of TNF-alpha. Genotype GA at -308 of TNF-alpha was related to higher clinical tumor stage of prostate cancer than genotype G (p <0.05). CONCLUSIONS: The present study demonstrates, for the first time, that the genotype changes in -308 and 488 regions of TNF-alpha are associated with prostate cancer.  相似文献   
137.
Bilateral congenital eventration of the diaphragm almost uniformly presents in infancy with respiratory compromise and is associated with a high mortality rate. Delayed presentation of diaphragmatic eventration in older children and adults may be associated with acute gastric volvulus. Thus, any patient with abdominal pain, vomiting, or nonspecific gastrointestinal symptoms in association with abnormal diaphragmatic findings on chest x-ray should undergo further diagnostic workup with upper gastrointestinal series or computed tomography (CT) scan. Treatment of gastric volvulus requires immediate surgical repair to prevent subsequent necrosis and perforation. The authors describe a case report of bilateral congenital diaphragmatic eventration complicated by a perforated gastric volvulus in a 13-year-old boy. Emergent reduction of the volvulus, closure of the perforated stomach, plication of the diaphragm, and placement of gastrostomy was performed successfully.  相似文献   
138.
Tailgut cyst in a neonate   总被引:1,自引:0,他引:1  
Tailgut cyst is a rare lesion of developmental origin located in the retrorectal space, which usually presents as a multilocular cystic mass. It is usually found in adults, and neonatal cases are extremely rare. The authors report a tailgut cyst in a neonate that was found by prenatal ultrasonogram, which was like a teratoma in gross appearance.  相似文献   
139.
OBJECTIVE: To compare the perioperative outcomes of two cesarean section methods, the finger-assisted stretching technique (FAST), based on a modified Joel-Cohen method, with the traditional technique. METHODS: A retrospective review of the records of 416 women who underwent cesarean sections at Guro Hospital, Seoul, Korea, between May 1993 and December 2001 was performed. Of the 416 women, 283 underwent cesarean sections with FAST and 133 with the traditional technique. RESULTS: Operative time was significantly shorter with FAST (15.3 vs. 42.6 min, P<.05), and FAST was associated with lower blood loss (601 vs. 928 mL, P<.05) and shorter hospital stay (3.7 vs. 6.5 days, P<.05). There were no significant differences in wound infection, voiding difficulty, and postoperative adhesions between the two methods. CONCLUSION: These results suggest that FAST may be the better technique.  相似文献   
140.
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