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   11984篇
  免费   655篇
  国内免费   3篇
  2023年   85篇
  2022年   64篇
  2021年   145篇
  2020年   109篇
  2019年   127篇
  2018年   404篇
  2017年   328篇
  2016年   419篇
  2015年   358篇
  2014年   468篇
  2013年   744篇
  2012年   959篇
  2011年   1120篇
  2010年   662篇
  2009年   353篇
  2008年   624篇
  2007年   586篇
  2006年   536篇
  2005年   422篇
  2004年   344篇
  2003年   336篇
  2002年   254篇
  2001年   161篇
  2000年   279篇
  1999年   226篇
  1998年   142篇
  1997年   88篇
  1996年   83篇
  1995年   94篇
  1994年   78篇
  1993年   64篇
  1992年   91篇
  1991年   81篇
  1990年   55篇
  1989年   79篇
  1988年   58篇
  1987年   77篇
  1986年   52篇
  1985年   86篇
  1984年   79篇
  1983年   70篇
  1982年   74篇
  1981年   70篇
  1980年   77篇
  1979年   75篇
  1978年   62篇
  1977年   85篇
  1976年   63篇
  1975年   57篇
  1973年   51篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
To gain insight into the role and association of cell cycle and apoptosis regulatory proteins and telomerase activity in the course of progression of melanocitic lesions we have examined immunohistochemicaly, expression and the distribution of p53, bcl-2, Ki-67 and telomerase in 25 samples of common and dysplastic nevi, and 45 samples of primary invasive melanomas. Protein p53 expression was significantly increased in dysplastic as compared with common nevi and melanomas (p < 0.001). Bcl-2 protein expression was significantly increased in melanomas as compared with common aquired and dysplastic nevi (p = 0.001). Nevi and melanomas exhibited clear-cut differences in terms of Ki-67 expression. Telomerase expression was significantly increased in melanomas as compared with common acquired (p = 0.014) and dysplastic nevi (p < 0.001). Enhanced telomerase activity in association with increased bcl-2 expression in the course of melanoma progression could contribute to development and progression of melanoma.  相似文献   
972.
On a small island of Rab, geographical latitude 44 degrees 40' N, with the highest solar radiation among Adriatic islands, 1371 patients were examined in 2003-2005 period, with the aim of estimating the frequency of the patients number with Age-related Macular Degeneration (AMD), and further if the peripheral retina is damaged similarly as the macular region. In the first group of agriculturists and fishermen (n = 1300) we estimated the AMD, initial and middle stage of AMD, in 18% of population, but in urban population only by 2 patients. Perimetric analysis with computerized Kowa perimeter, estimated that the peripheral retina is affected similarly as the macular region. Author concludes that for this reason, the usual term of "Age-related Macular Degeneration" should necessarily be named with the suffix "Peripheral", or "Age-related Retinopathy".  相似文献   
973.
This paper describes a case of asymptomatic multifocal actinomycosis of the greater omentum which was detected accidentally in a patient who was suspected of uterus myoma. The patient was a 40 year old woman who had a copper intrauterine contraceptive device (IUCD) for three years. After the gynecological examination and pelvic ultrasound she was diagnosed with sub serous myoma of uterus. Since she did not give a birth it was suggested to have myoma enucleating. However during the surgery a dermoid teratoma of the right ovary was detected so it was removed together with tumor and there were two thickenings on the greater omentum, suspicious of inflammation, whereas one grew together with the front abdominal wall. Due to these conditions, she had partial omentectomy done and omentum was sent for path histological examination. The path histological examination confirmed it to be actinomycosis. The patient had an intensive antibiotic therapy prescribed (Penicillin) in order to prevent a disease relapse because we could not be sure whether the remaining part of omentum was affected by microscopic actinomycosis.  相似文献   
974.
The aim of the study was to determine a combination of anthropometric variables that would enable better differentiation between benign and malignant ovarian masses. Prospective study has been performed in a two year period in which 208 women with ovarian lesions were analyzed and correlated with histopathologic surgical findings. We examined the relation between self-reported anthropometric and other variables (height, weight, body mass index--BMI, parity, marital status, education, age, rural versus urban residence, menopausal status) and incidence of ovarian cancer. Age, parity, marital status and menopausal status individually showed statistical significance.  相似文献   
975.
The aim of this research was to assess the clinical and biochemical efficacy of the octreotide in the treatment of patients with various functional gastroenteropancreatic neuroendocrine tumors (GEP-NETs). The study included 14 patients treated with octreotide for 6 months. They were diagnosed with VIPoma, glucagonoma, gastrinoma, medullary thyroid carcinoma (solitary and as a part of MEN-II syndrome), pancreatic carcinoids (solitary and as a part of multiple endocrine neoplasia type-1 syndrome-MEN-1 syndrome) and midgut carcinoids. The patients presented with Verner-Morrison, glucagonoma, Zollinger Ellison and carcinoid syndrome respectively. All had a metastatic disease at the time of diagnosis and a positive octreoscan finding. Initially elevated chromogranin A (CgA) levels were detected in 11 (78.6%) and elevated 5-hydroxyindolacetic acid (5-HIAA) levels in 8 (57.1%) patients. Symptomatic efficacy assessments were made by diarrhea reductions during treatment course, and laboratory efficacy was assessed through changes in 5-HIAA and CgA levels. Assessments were made initially and following 6 months of therapy. Median urinary 5-HIAA and the number of stools decreased significantly (p = 0.016 and p = 0.009 respectively, p < 0.05) while CgA levels had the decreasing tendency but not statistically significant (p = 0.14). There was a positive correlation between the 5-HIAA reduction and the decrease in stool number at baseline and during treatment course (p < 0.05). No correlation was observed between 5-HIAA and CgA levels and also there was no correlation between CgA reduction and symptomatic improvement. The results prove octreotide to be effective in reducing symptoms and biochemical markers associated with hypersecretory syndromes of GEP-NETs.  相似文献   
976.
The aim of the study was to assess the relationship between systolic blood pressure during maximal treadmill test (SBP9mtt)) and flow-mediated vasodilation (FMD). Abnormal rise of SBP(mtt) is the phenomenon more frequent in hypertensive persons but it could be found in normotensive subjects too. 199 subjects referred to treadmill test were enrolled in the study. Four groups were formed: hypertensives with abnormal SBP(mtt) (group A), hypertensives with normal SBP(mtt) (group B), normotensives with abnormal SBP(mtt) (group C) and normotensives with normal SBP(mtt) (group D). Rise of SBP(mtt) above 200 mmHg was considered abnormal reaction. Simple linear regression analysis showed significant inverse relationship between SBP(mtt) and FMD (F = 20.2036, p < 0.001, R2 = 0.0956). Mean FMD index was worst in hypertensive subjects with abnormal SBP(mtt) (group A), followed by normotensives with abnormal SBP(mtt) (group C), hypertensives with normal SBP(mtt) (group B) and the best was in normotensives with normal SBP(mtt) (3.56 +/- 5.17, 4.19 +/- 5.14, 6.81 +/- 8.43 and 10.92 +/- 7.48%, respectively). In multivariate regression analysis FMD showed significant association with abnormal SBP(mtt) (p < 0.001) along with brachial artery diameter (p < 0.001), male gender (p < 0.001), but not with hypertension (p = 0.073), BMI (p = 0.137) and total cholesterol (p = 0.23) (coefficients: -0.26, -0.40, -0.27, -0.13, -0.11 and -0.07, respectively). There was a significant inverse relationship between SBP(mtt) and FMD. An impairment of FMD exists in normotensive subjects with abnormal SBP(mtt). In hypertensives with abnormal SBP(mtt) an additional impairment of FMD exists when compared to hypertensives with normal SBP(mtt). Abnormal SBP(mtt) should be taken into account in global cardiovascular risk assessment.  相似文献   
977.
Multislice helical CT generated virtual bronchoscopy (VB) represents one of the most recent developments in three-dimensional computer aided visualisation techniques. VB allows non-invasive and relatively accurate 3D evaluation of tracheobronchal tree. We performed virtual bronchoscopy and in-space 3D volume analysis on CT-data set acquired from sixty-four-year old male with bronchial cancer in order to demonstrate advantages and disadvantages of these methods in diagnostics and preoperative management of metastatic bronchial cancer. Siemens Somatom Emotion 16 helical CT scanner was used for data acquisition. Data post-processing was done with 3D Syngo 2006G software package from Siemens medical systems. CT scanning of the thorax was performed in heavy smoker with an expansive T4N1M1 malignant process in a superior lobe of the right lung accompanied with large metastatic lesion attached on the right lateral chest wall. Metastatic lesions were also found in vertebral column. In-space 3D analysis followed with virtual bronchoscopy had revealed obstruction of apical branch of superior lobe segmental bronchus. External compression done by tumor to the superior segmental and right main bronchus was found. We concluded that multi-slice CT in connection with VB became a possible non-invasive alternative to bronchoscopy, if tissue samples are not required.  相似文献   
978.
The investigation was performed on 113 adolescents in the age between 15 and 18 years (63 boys, 50 girls). Corah Dental Anxiety Scale (CDAS) and Children's Fear Survey Schedule - Dental Subscale (CFSS-DS) were used for evaluation of dental fear and Child Medical Fear Questionnaire (CMFQ) for evaluation of the fear of medical treatment. Achenbach Youth Self Report questionnaire (YSR) was used for evaluation of emotional and behavioral problems. The tests were filled in by children. The aim of the study was to evaluate the level of dental anxiety in adolescents and to assess a cause--consequence relationship between dental anxiety and emotional and behavioral problems in adolescents. The results of CDAS, CFSS-DS and CMFQ tests showed that dental anxiety scores and the total internalizing problems were higher in girls. Girls displayed more physical problems (p < 0.001) and were more prone to anxiety/depression disorders (p < 0.05). Both boys and girls were more aggressive, more prone to delinquent behaviour and had more externalizing problems in comparison with the average values obtained for the Croatian population. Significant correlation coefficients for boys were calculated for age and anxiety/depression, and delinquent behaviour and aggression (p < 0.05). Significant correlations were observed between physical problems and dental anxiety measured by the CFSS-DS test (p < 0.01), and between physical problems and the total internalizing problems (p < 0.05). In girls, the CMFQ scores showed significant correlations between dental anxiety and physical problems (p < 0.05), and anxiety/ depression (p < 0.01) and the total internalizing and externalizing problems (p < 0.05). Significant correlations were calculated for age and the total internalizing and externalizing problems for boys (p < 0.05). According to the results of both CDAS and CMFQ tests, anxiety in girls showed significant correlations with delinquent behaviour (p < 0.01). CDAS scores for girls showed significant correlations with aggression (p < 0.05) and the total externalizing problems (p < 0.01).  相似文献   
979.
Opportunistic screening based on the Pap smear has been undertaken in Croatia since 1953. However, cervical cancer remains an important health problem in Croatia when compared to European countries with organised screening programmes. In Croatia, in addition to screening based on well established cytology, Human papillomavirus (HPV) testing is widely used as secondary test as a triage to borderline cytology and as a follow-up after treatment of severe cervical lesions. Many different approaches for HPV testing arose in Croatia over the last decade depending on the needs of each medical institution involved. Presently, there is an urgent need for better networking between the laboratories, the implementation of quality assessment and the adaptation of a uniform system of referring to and reporting of HPV testing. In conclusion, the best possible organisation for HPV testing would be essential for implementation of HPV testing as primary screening test in Croatia, an thus ultimately and hopefully, the more successful cervical cancer control.  相似文献   
980.
The aim of this study was to determine the virulence characteristics and resistance pattern of the extended-spectrum/lactamases (ESBLs)-producing Escherichia coli strains isolated from urine of outpatients in the Zagreb region during a five-month period, and to compare them with the non ESBLs-producing E. coli strains isolated in the same period. Out of 2451 E. coli strains isolated from urine of nonhospitalized patients with significant bacteriuria, a total of 39 ESBLs-producing strains (1.59%) were detected by a double-disk diffusion technique and by the broth-dilution minimal inhibitory concentration reduction method. The 45 non ESBLs-producing strains were randomly chosen, and phenotype of the two groups of strains was characterized and compared. Serogroup O4, hemolysin production, expression of P- and type 1 fimbriae as well as resistance to gentamicin and amikacin were significantly more prevalent characteristics among the ESBLs-producing strains than among non ESBLs-producing strains (p < 0.01), while higher prevalence of trimethoprim-sulfamethoxazole resistance among ESBLs-producing strains was not statistically significant (p > 0.05). Chromosomal DNA analysis by pulsed-field gel electrophoresis exhibited a great genomic similarity among ESBLs-producing strains and revealed that those highly virulent and resistant E. coli strains isolated from urine of outpatients in the Zagreb region had a clonal propagation.  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