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   353篇
  免费   22篇
  国内免费   1篇
耳鼻咽喉   6篇
儿科学   14篇
妇产科学   19篇
基础医学   39篇
口腔科学   6篇
临床医学   57篇
内科学   58篇
皮肤病学   9篇
神经病学   31篇
特种医学   3篇
外科学   58篇
综合类   3篇
预防医学   14篇
眼科学   4篇
药学   25篇
中国医学   1篇
肿瘤学   29篇
  2023年   4篇
  2022年   23篇
  2021年   22篇
  2020年   9篇
  2019年   17篇
  2018年   16篇
  2017年   12篇
  2016年   13篇
  2015年   11篇
  2014年   9篇
  2013年   23篇
  2012年   28篇
  2011年   16篇
  2010年   9篇
  2009年   13篇
  2008年   11篇
  2007年   19篇
  2006年   12篇
  2005年   13篇
  2004年   12篇
  2003年   7篇
  2002年   14篇
  2001年   8篇
  2000年   5篇
  1999年   6篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1993年   1篇
  1991年   1篇
  1989年   2篇
  1987年   1篇
  1986年   5篇
  1985年   4篇
  1984年   6篇
  1983年   3篇
  1981年   1篇
  1979年   3篇
  1978年   3篇
  1977年   1篇
  1975年   1篇
  1973年   1篇
  1972年   2篇
  1971年   2篇
  1967年   3篇
  1966年   1篇
排序方式: 共有376条查询结果,搜索用时 15 毫秒
21.
22.
OBJECTIVE: The authors attempted to estimate the occurrence, frequency, and pattern (winter versus summer) of seasonal affective disorder in African American college students. They hypothesized that winter seasonal affective disorder would be more prevalent than summer seasonal affective disorder. METHOD: Undergraduate and graduate college students who identified themselves as African Americans living in the Washington, D.C., metropolitan area were invited to participate in the study. The Seasonal Pattern Assessment Questionnaire was used to calculate a global seasonality score and to estimate the frequency of seasonal affective disorder and subsyndromal seasonal affective disorder. The frequency of the summer versus winter pattern of seasonality of seasonal affective disorder was compared by using multinomial probability distribution tests. The effects of gender and the awareness of seasonal affective disorder were evaluated with a two-way analysis of variance. RESULTS: Of 646 students who were invited to participate, 597 returned the questionnaires, and 537 (83.1%) fully completed them. Winter seasonal affective disorder was significantly more prevalent than summer seasonal affective disorder. The mean global seasonality score was 8.3 (SD=5.3). The majority of the subjects (80%) were not aware of the existence of seasonal affective disorder. CONCLUSIONS: The authors found that the frequency, magnitude, and pattern of seasonality of mood in African American students were similar to those previously reported in the general population at similar latitude, but that awareness of the existence of seasonal affective disorder, a condition with safe and effective treatment options, was lower.  相似文献   
23.
A study on the prevalence of accessory auricle anomaly in Turkey   总被引:4,自引:0,他引:4  
OBJECTIVE: Accessory auricular anomaly is a small elevation of skin containing a bar of elastic cartilage localized most commonly just anterior to the tragus or ascending crus of the helix. The anomaly may exist isolated or may be associated with other congenital anomalies of the first arch. The purpose in this study is to detect prevalence of accessory auricle in Turkey and find out whether it is associated with other craniofacial anomalies or hearing loss. METHODS: The study was performed on 850 children from the age of 7 to 9 during a screening program in primary schools. Complete otolaryngologic examination and acoustic reflectometry measurements were performed on all the children. Full physical examination, tympanometric and audiometric evaluation and EEG measurements were added to the cases with accessory auricle anomaly. RESULTS: Among 850 children examined, four had accessory auricle anomaly and prevalence of the anomaly was calculated as 0.47% (95% confidence interval (CI), 0.13-1.20%). Children were developmentally normal, and no other congenital craniofacial or systemic anomaly was detected in any of the cases. Further, tympanometric, audiometric evaluations and EEG tests were in normal limits. CONCLUSIONS: In this study, the prevalence rate of the condition was calculated as 0.47%. Although one study from China reported this prevalence as 0.22%, the difference between the reported prevalances was not statistically significant. Further, although external ear anomalies may present together with cranifacial anomalies and neurologic disorders like epilepsy, neuromotor retardation and EEG disorders, in our cases, mental and motor development was normal and epilepsy history or abnormal EEG patterns do not exist. On the other hand, no hearing loss was found to be associated with accessory auricles.  相似文献   
24.
The hypothesis that immunodepression favors a carcinogenetic process and thus subsequent tumor development remains controversial in spite of numerous experimental studies. This is due, on one hand, to the difficulty in demonstrating the presence of tumor-associated antigens and, on the other, to the complex immunological mechanisms which lead to the destruction of tumors cells. With respect to immunosurveillance, the present situation can be summarized as follows: the development of virus-induced tumors is under the control of a T-cell dependent system; a T-cell depression (thymectomy, congenital absence of thymus, anti-lymphocytic serum) increases the number of these tumors; chemically induced tumors or spontaneous tumors are under the control of non-specific effectors such as macrophages and NK cells; NK cell deficiency (of congenital origin such as in beige mice) or acquired (chemically induced) increases tumor growth; carcinogens can induce general immunodepression (chemical carcinogenesis) or stimulate specific suppressive cells (U.V. radiation) thus allowing tumors development. The tumors being established, it may itself contribute to an immunodepressive state thus fostering its growth through the activity of: immune complexes; specific or non specific suppressive cells; an increase in the level of alpha 2-globulin immunosuppressive molecules which are present under normal conditions; a release of several factors acting at different levels such as prostaglandin E, anti-inflammatory factors acting on monocytes, etc. The apparition of an antigenic and immunogenic tumor heterogeneity due to development of new clones will also modify host-tumor relationships. The complexity of the immunological mechanisms which are involved in the control of tumor growth may explain the variable results of immune prevention and of the immunotherapy of cancer.  相似文献   
25.
Metformin (MTF), an effective biguanide and oral antihyperglycemic agent, is utilized to control blood glucose levels in patients with type II diabetes mellitus, and the determination of its concentration in biological fluids is one of the main issues in pharmacology and medicine. In this work, highly luminescent nitrogen-doped graphene quantum dots (N-GQDs) were modified using terbium (Tb3+)–1,10-phenanthroline (Phen) nanoparticles (NPs) to develop a dual-emission ratiometric fluorescent sensor for the determination of MTF in biological samples. The synthesized N-GQDs/Tb–Phen NPs were characterized using different techniques to confirm their physicochemical properties. The N-GQDs/Tb–Phen NPs showed two characteristic emission peaks at 450 nm and 630 nm by exciting at 340 nm that belong to N-GQDs and Tb–Phen NPs, respectively. The results indicated that the emission intensity of both N-GQDs and Tb–Phen NPs enhanced upon interaction with MTF in a concentration-dependent manner. Also, a good linear correlation between the enhanced fluorescence intensity of the system and MTF concentration was observed in the range of 1.0 nM–7.0 μM and the limit of detection (LOD) value obtained was 0.76 nM. In addition, the prepared probe was successfully used for the estimation of MTF concentration in spiked human serum samples. In conclusion, the reported dual-emission ratiometric fluorescent sensor can be used as a sensitive and simple fluorimetric method for the detection of MTF in real samples.

Shcematic representation of the MTF detection by an enhancing mechanism.  相似文献   
26.

Purpose

To investigate the effect of polymerization method on the stability and drug release properties of polymeric micelles formed using stereo-active block copolymers.

Methods

Diblock copolymers consisting of methoxy poly ethylene oxide (MePEO) and poly(lactide)s (PLA)s of different stereochemistry were synthesized by bulk or solution polymerization. Polymers and micelles were characterized for their chemical structure by 1H NMR, optical rotation by polarimetry, critical micellar concentration by fluorescence spectroscopy, thermal properties by differential scanning calorimetry, morphology by transmission electron microscopy and size as well as kinetic stability by dynamic light scattering. Release of encapsulated nimodipine from polymeric micelles at different levels of loading was also investigated.

Results

Solution polymerization yielded a higher degree of crystallinity for stereo-regular PLA blocks. Consequently, the related polymeric micelles were kinetically more stable than those prepared by bulk polymerization. At high drug loading levels, the release of nimodipine was more rapid from polymeric micelles with crystalline cores. At lower levels of drug loading, drug release was slower and independent of the stereochemistry of the core.

Conclusions

The results underline the effect of polymerization method in defining core crystallinity in stereoregular block copolymer micelles. It also shows the impact of core crystallinity on enhancing micellar stability and drug release.  相似文献   
27.
Our study aimed to determine anti-HBc total (IgG+IgM) seroprevalence in the adult population aged ≥15 and to compare the cost of testing for HBsAg and anti-HBs in only anti-HBc positive (+) subpopulation to that in the whole population for HBV screening. The study involved a face-to-face survey and peripheral blood sampling from 452 adult subjects for HBV tests. HBV-DNA PCR was studied only in anti-HBc(+)subjects. Of the 452 subjects anti-HBc total was positive in 192 (42.47%), of which: (a) 27 (14.06%) were HBsAg(+), anti-HBs negative (-), (b) 126 (65.62%) were HBsAg(-), anti-HBs(+), (c) 39 were HBsAg(-), anti-HBs(-). This last group (c) were tested for HBV-DNA PCR and six (15.38%) were positive. When we perform HBsAg and anti-HBs tests in all 452 subjects as in routine practice in blood banks, the cost is 3320 Euros. However, when all subjects are tested for anti-HBc total at first and then only anti-HBc total(+) ones are tested for HBsAg and anti-HBs, the cost is 2929 Euros. The cost difference between the two methods is 391 Euros for 452 subjects. Accordingly, our HBV screening algorithm brings a financial saving of 11.78% and helps to identify the isolated anti-HBc total(+) subjects who carry potential risk for spreading HBV.  相似文献   
28.
29.
A total of 39 women with metastatic breast cancer entered a pilot phase II study of the vindesine-mitoxantrone-mitomycin (VMMc) combination chemotherapy. Most of them had received previous chemotherapy [including doxorubicin (27 patients)] for their primary or metastatic disease. The VMMc drugs were given at usual doses. Hematologic side effects were the most serious, leading mainly to leukopenia (five episodes of infection were successfully treated). A 33% partial response rate was obtained (95% confidence limits, 18%-48%), with a median duration (not yet reached) of greater than 510 days (range, 150-720) for the overall population. The median for pretreated patients was greater than 420 days (range, 150-720) which compares favorably with those previously reported in similar patients treated by mitomycin and vindesine or vinblastine.  相似文献   
30.
Placenta increta complicated pregnancy in a woman with a history of endometrial resection. Placentation in women with prior endometrial ablation carries a high risk for placenta accreta, increta and percreta. Contraceptive measures must be implemented after endometrial ablation and pursued until proven menopause, even in women who develop amenorrhoea postoperatively.  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