首页 | 官方网站   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   8191篇
  免费   444篇
  国内免费   61篇
医药卫生   8696篇
  2024年   9篇
  2023年   76篇
  2022年   103篇
  2021年   237篇
  2020年   135篇
  2019年   187篇
  2018年   249篇
  2017年   183篇
  2016年   195篇
  2015年   238篇
  2014年   288篇
  2013年   363篇
  2012年   570篇
  2011年   596篇
  2010年   359篇
  2009年   331篇
  2008年   531篇
  2007年   560篇
  2006年   555篇
  2005年   490篇
  2004年   505篇
  2003年   482篇
  2002年   425篇
  2001年   95篇
  2000年   87篇
  1999年   111篇
  1998年   89篇
  1997年   73篇
  1996年   58篇
  1995年   44篇
  1994年   30篇
  1993年   37篇
  1992年   34篇
  1991年   26篇
  1990年   26篇
  1989年   41篇
  1988年   43篇
  1987年   29篇
  1986年   25篇
  1985年   17篇
  1984年   18篇
  1983年   16篇
  1982年   16篇
  1981年   9篇
  1979年   14篇
  1978年   7篇
  1977年   9篇
  1974年   7篇
  1970年   10篇
  1967年   7篇
排序方式: 共有8696条查询结果,搜索用时 15 毫秒
81.

Conclusion

Geographical differences in morbidity of asthma and asthmalike complaints were ascertained and remained stable after adjustment for potential confounders. However, the choice of the way of presentation (relative risk versus deviation from the weighted mean of the prevalences) can provoke different suggestive effects.  相似文献   
82.
Based on the hypothesis that free radicals play a general role in the neurodegenerative process in motor neuron disease, we tested selegiline in a group of patients affected by amyotrophic lateral sclerosis (ALS) to examine whether it might modify the progression of the disease. Patients were admitted if they were 25–80 years old and had a confirmed diagnosis of ALS with symptoms lasting no longer than 24 months. Patients with familial ALS, pure progressive bulbar palsy, primary lateral sclerosis or progressive muscle atrophy were excluded; a total of 111 patients were recruited. Fifty-three patients were randomly assigned to receive the drug (selegiline 10 mg/day orally for 6 months) and the remaining 58 were considered ALS controls. Mortality was similar in the two groups (4 and 5 patients respectively), though the difference was not statistically significant. Among the survivors, mean MRC and Norris disability scores and forced vital capacity were fairly similar in the two groups at all times and no statistically significant difference between treated and untreated patients was found. The results did not change when the data were related to age, duration and characteristics of onset of the disease. The rate of progression was significantly more rapid in patients with bulbar symptoms in both groups. Our data do not show any significant effect of selegiline in modifying the progression of ALS.  相似文献   
83.
We reviewed 34 patients with histologically proven anaplastic thyroid carcinoma, representing 3.1% of all thyroid carcinomas treated from 1970 to 1992 in our Institution. Mean age at diagnosis was 63.1+/-10.3 years. Initial treatment consisted of near total thyroidectomy in 14 patients, partial thyroidectomy in 6 and no more than a biopsy in 14. After surgery 11 patients received external radiotherapy associated with chemotherapy (R+C), 8 patients had only chemotherapy (C), and 11 patients had only radiotherapy (R). Two patients, both in the group treated with R+C, are still alive, with a survival from the diagnosis of 23 and 26 months, respectively. Mean survival of the group treated with R+C (16.1+/-8.2 months) was significantly higher than that of patients treated only with C (6.2+/-4.4 months; p<0.01) or only with R (5.1+/-2.6 months; p<0.0004). In the group treated with R+C, patients submitted to near total or partial thyroidectomy had a mean survival of 15.0+/-8.8 months, similar to that of patients who had only a biopsy (17.2+/-7.9 months), suggesting that the outcome was affected by post-surgical therapy rather than by surgery per se. Twenty-two tumors were also assayed by immunohistochemistry for p53 and PCNA expression. p53 was expressed in 16/22 (72.2%) cases, with no correlation with sex, age, presence of differentiated component or survival. Comparing tumors with <30% or >30% p53 positive cells a tendency to longer (but not significant) survival was found in tumors with lower p53 expression. PCNA was expressed in all cases, with a percentage of positive cells ranging from 15% to 90%, and was not correlated with sex, age, differentiation, or survival. A positive correlation was found between PCNA and p53 expression (r=0.58; p=0.0039). In conclusion, our data indicate that in anaplastic thyroid carcinoma the use of combined R+C has some advantages with respect to single therapy. As in other aggressive malignancies; p53 and PCNA expression is increased irrespective of the response to therapy or the outcome.  相似文献   
84.
Endoscopic thyroid and parathyroid surgery   总被引:5,自引:0,他引:5  
  相似文献   
85.
86.
The Authors, after a short introduction concerning the primary carcinoma of the cystic duct and the exact definition according to Farrar's criteria, report a case occurred to their observation, the 35th case of international literature. In particular the importance of some hemato-clinical parameters and instrumental investigation (ERCP, angio-CT) to underlined in order to surgical indication. In the case here reported cholecystectomy uses informed with partial resection of the hepato-choledochus and excision of some periductal and pericholedochus lymph nodes. Finally, the Authors discuss about clinical data and diagnostic and therapeutic trends, on the case of their experience and literature review.  相似文献   
87.
Polyamine metabolism in gliomas   总被引:2,自引:0,他引:2  
Summary Biosynthesis of the polyamines putrescine, spermidine, and spermine has been found to be activated in tissues with cellular proliferation. In the present study we have investigated polyamine levels and the activity of the first rate-limiting enzyme ornithine decarboxylase (ODC) in tumour samples obtained during operation of 202 patients with gliomas. Biochemical data were closely related to the grading of malignancy and to the morphological characteristics of each sample. Mean ODC activity was significantly higher in all gliomas as compared to peritumoural non-neoplastic brain. Furthermore, it was significantly higher (p 0.001) in anaplastic gliomas who grade III and IV (9.0 ± 9.6 nmol/g/h) than in gliomas WHO grade I and II (3.3 ± 4.2 nmol/g/h). Highest enzyme activity (58.5 nmol/g/h) was found in solid and vital parts of malignant tumours, whereas predominantly necrotic areas exhibited low ODC activity (< 1 nmol/g/h). Thus, intra- and interindividual variability of ODC activity corresponded well to histomorphological heterogeneity in high-grade gliomas. Putrescine levels also increased with rising grade of malignancy, whereas spermidine and spermine levels did not correlate with the histological grading. In conclusion, high ODC activity represents a biochemical marker of malignancy in gliomas, but low values do not prove benignity. The present study reinforces the need of further and more extensive tumour sampling closely related to follow-up investigations in the heterogeneous group of gliomas.  相似文献   
88.
AIMS AND BACKGROUND: Isolated vaginal recurrences of endometrial carcinoma are rare, and prognostic factors that predict treatment outcome are still not well defined. The aim of the present study was to evaluate the results of brachytherapy in isolated vaginal recurrences from endometrial carcinoma. METHODS: Thirty-five patients with isolated vaginal recurrences were treated with brachytherapy with intravaginal ovoids or cylinders that were calculated to deliver 6000 to 7000 cGy at the surface. Patients were assessed for size and location of recurrence at presentation, response and complications from therapy. RESULTS: Treatment was well tolerated by most patients. Grade 2 toxicity occurred in 4 patients (3 cases of partial vaginal stenosis and one proctitis). Complete response to radiation was observed in all patients, and an overall 9 failures were observed (4 local, 4 distant and 1 local plus distant). Twenty patients (57%) were alive without evidence of disease at 3 to 11 years following treatment. Site of vaginal recurrence (upper third versus others) and long (more than 12 months versus less than 12 months) interval from hysterectomy were the only factors significantly related to local failures. CONCLUSIONS: Isolated vaginal recurrences following hysterectomy for endometrial carcinoma can be treated with brachytherapy with a low rate of severe toxicity.  相似文献   
89.
A major aflatoxin G1 (AFG1)-albumin adduct has been identifiedand characterized in rats following exposure to AFG1. The productisolated from a Pronase digest of in vivomodified albumin wasidentical by chromatographic retention time to the syntheticproduct obtained by the acylase-catalysed deacetylation productof N-acetyl-L-lysine with 8,9-dihydro- 8,9-dibromo-AFG1. Thein vitro product, AFG1-lysine, was characterized by UV, fluorescence,1H- and 13C-NMR spectroscopy and fast atom bombardment MS. Acompetitive enzyme-linked immunoassay for this adduct was establishedusing polyclonal antibodies to AFB, and this was used togetherwith an HPLC-fluorescence technique to quantitate the in vivoformation of AFG1–albumin adducts in comparison to AFB1.A linear dose–response relationship was observed in ratsfollowing single exposures to 0.1– 3 mg AFG1/kg body wt.The levels of AFG1-albumin adducts were determined to be 5.7-and 2.8-fold lower than with equivalent doses of AFB1 as determinedby immunoassay and HPLC fluorescence respectively. The lowerbinding of AFG1 and the lower levels in the human food supplycompared to AFB, suggest that the newly identified adduct couldbe added as an internal standard for methods using the measurementof aflatoxin-albumin adducts to quantitate human exposure toaflatoxin.  相似文献   
90.
The effects of a single dose of TCDD on the testis were studied in rats. The animals were treated (subcutaneously) once with TCDD doses of 0, 0.5, 1.0, 3.0, 5.0 g/kg body weight. Doses of 3.0 or 5.0 g TCDD/kg reduced the number of spermatids/testis significantly (60% of the controls). Electron microscopic inspection revealed that both doses led to a dissolution on the germinal epithelium. Altered germ cells at all developmental stages occurred in all testes evaluated. Doses of 0.5 or 1.0 g TCDD/kg did not induce any effects in the testis; therefore, under these experimental conditions of single exposure to rats the dose of 1.0 g TCDD/kg can be considered as NOAEL.  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-23

京公网安备 11010802026262号