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   11989篇
  免费   699篇
  国内免费   138篇
耳鼻咽喉   117篇
儿科学   264篇
妇产科学   117篇
基础医学   1194篇
口腔科学   177篇
临床医学   865篇
内科学   3234篇
皮肤病学   227篇
神经病学   698篇
特种医学   494篇
外科学   2265篇
综合类   191篇
预防医学   313篇
眼科学   169篇
药学   825篇
中国医学   66篇
肿瘤学   1610篇
  2023年   101篇
  2022年   201篇
  2021年   351篇
  2020年   215篇
  2019年   267篇
  2018年   315篇
  2017年   287篇
  2016年   335篇
  2015年   384篇
  2014年   418篇
  2013年   503篇
  2012年   817篇
  2011年   837篇
  2010年   504篇
  2009年   410篇
  2008年   639篇
  2007年   686篇
  2006年   725篇
  2005年   725篇
  2004年   690篇
  2003年   705篇
  2002年   672篇
  2001年   199篇
  2000年   174篇
  1999年   191篇
  1998年   121篇
  1997年   106篇
  1996年   94篇
  1995年   80篇
  1994年   89篇
  1993年   71篇
  1992年   82篇
  1991年   100篇
  1990年   73篇
  1989年   85篇
  1988年   83篇
  1987年   59篇
  1986年   47篇
  1985年   31篇
  1984年   37篇
  1983年   42篇
  1982年   16篇
  1980年   14篇
  1979年   35篇
  1978年   13篇
  1975年   12篇
  1973年   20篇
  1971年   18篇
  1969年   14篇
  1966年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The apatite-forming ability of titania gels with different structures has been investigated in a simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Titania gels with an amorphous structure or with an anatase or rutile structure were prepared by the sol-gel process with a subsequent heat treatment at various temperatures. The titania gels with an amorphous structure did not induce apatite formation on their surfaces in the simulated body fluid, whereas gels with an anatase or rutile structure induced apatite formation on their surfaces. The deposition of apatite was more pronounced on the anatase gels than on the rutile gels. This indicates that a specific structure of titania is effective in inducing apatite formation in a body environment. Such a specific structure was assumed in this study to be the crystalline planar arrangement in the anatase structure, which facilitates epitaxy of the apatite crystal.  相似文献   
72.
Imai M  Hwang HY  Norris JS  Tomlinson S 《Immunology》2004,111(3):291-297
Dexamethasone has been shown to up-regulate human mucin 1 (MUC1) expression in certain types of cancer cell lines in vitro, suggesting that this gluocorticoid may enhance MUC1-based immunotherapies. Here we investigated the effect of dexamethasone on MUC1 expression in the DU145 human prostate cancer cell line in terms of antibody-mediated complement-dependent cell lysis. Cells treated with 1 x 10-8 m dexamethasone in vitro expressed maximal levels of MUC1 after 6 days, with an approximately 3-fold increase over MUC1 levels on untreated cells. DU145 cells were highly resistant to lysis by anti-MUC1 antibody and complement, and their susceptibility to antibody and complement was unaffected by dexamethasone treatment. However, dexamethasone also induced expression of the complement inhibitor decay accelerating factor (DAF) on DU145 cells. Blocking or overcoming the function of DAF resulted in enhanced complement-dependent lysis of dexamethasone-treated cells with anti-MUC1 antibodies, indicating that the failure of dexamethasone to enhance the complement susceptibility of DU145 cells was caused by the up-regulated expression of DAF. We also investigated MUC1 expression in vivo and found that MUC1 expression was significantly up-regulated on tumour cells isolated from immune-deficient mice that had been injected with dexamethasone. However, in contrast to in vitro data, there was no difference between the levels of DAF expressed on tumour-derived DU145 cells isolated from either phosphate buffered saline (PBS)-treated or dexamethasone-treated mice, and tumour cells isolated from dexamethasone-treated mice were more sensitive to complement-mediated lysis. In the broad context of immunotherapy, the in vivo data support the use of dexamethasone as an adjunct treatment. Up-regulated DAF expression would not be a favourable outcome of dexamethasone treatment in terms of complement-dependent antibody therapy, but the in vivo data caution against extrapolation of in vitro data with regard to the modulation of complement inhibitors reported here and elsewhere.  相似文献   
73.
急性髓系白血病血管内皮生长因子表达与预后的研究   总被引:1,自引:0,他引:1  
目的 :观察人白血病细胞系血管内皮生长因子 (VEGF)表达水平 ,研究急性髓系白血病 (AML)患者血清VEGF表达水平与预后的关系。方法 :采用酶联免疫吸附法 (ELISA)对 4 9例初治、10例复发AML患者血清及人白血病细胞系U937、K5 6 2、HL - 6 0、TF - 1和NB4培养上清液 (4 8小时 )VEGF表达水平进行检测。结果 :五种人白血病细胞系培养上清液中均测到VEGF高表达。 4 9例初治、10例复发AML患者的血清VEGF表达水平分别为 2 0 1 17± 110 93pg ml和 2 32 5 9± 118 6 2pg ml,均明显高于正常对照组 (12 5 6 2± 4 5 4 3pg ml;p <0 0 5 )。初治AML患者中VEGF高表达组 (>2 0 1 17pg ml)完全缓解 (CR)率为 4 8% ,低表达组 (<2 0 1 17pg ml)CR率为 77% ,两者比较差异显著 (p<0 0 5 )。结论 :血管内皮生长因子在刺激白血病细胞增殖、迁移中发挥重要作用。AML患者血清VEGF水平与预后具相关性  相似文献   
74.
To investigate how single neurons in the supplementary eye field (SEF) participate in sequential performance of multiple saccades, we analyzed presaccadic activity while monkeys were performing three saccades in six different orders from memory. The saccades in each sequence were separated by a fixation period and initiated from the same fixation point with intervening return saccades. We found that the majority of the presaccadic activity of the SEF neurons differed significantly depending on the numerical position of saccades in each sequence (rank order). This rank-order selectivity was found in parallel with the selectivity for the sequence of three saccades. Our data suggest a role for SEF neurons in the coding of temporally ordered saccadic eye movements.  相似文献   
75.
Campylobacter jejuni isolation is the standard for the diagnosis of this type of bacterial infection, but there have been no epidemiological studies of a large number of C. jejuni isolates from patients with Guillain-Barre syndrome (GBS) and Fisher syndrome (FS). For 13 years, stool specimens from GBS/FS patients have been sent from 378 hospitals throughout Japan to the Tokyo Metropolitan Institute of Public Health. A total of 113 strains (11%) were isolated from the stool specimens from 1,049 patients. The isolation rate did not differ by region. The rates were 22% for 449 patients with a history of diarrhea and 2% for the others. An additional 18 isolates were provided by various hospitals. There was no noticeable seasonal distribution in the onset of C. jejuni isolated from patients with GBS/FS. The male/female ratios were 1.7:1 for GBS and 2.2:1 for FS. The patient age range showed a peak in 10- to 30-year-old subjects who had GBS and in 10- to 20-year-old subjects who had FS. The predominance of young adults and male patients who had C. jejuni-associated GBS/FS may be related to the preponderance of young adults and male patients who had C. jejuni enteritis. The median interval from diarrhea onset to neurologic symptom onset was 10 days for GBS/FS. Penner's C. jejuni serotype HS:19 was more frequently present in GBS (67%) than in enteritis (6%) patients. HS:2 was more frequent in FS (41%) than in enteritis (14%) patients. These findings suggest that certain C. jejuni strains specifically trigger GBS and that others specifically trigger FS.  相似文献   
76.
The immunoreactivity of albumin (ALB) was observed in the hepatocytes of fetal rats on day 18 of gestation, and was especially observable in immature rough endoplasmic reticulum (rER) and Golgi apparatus (GA); by then, a small amount of silver grains of ALB mRNA could already be detected. Just after birth, immunoreactivity of ALB could be observed in fine granules or diffusely in all hepatocytes, and was present in rER and GA. One week after birth immunoreactivity of ALB was observed in all hepatocytes and was visible in developed rER and GA; the grains of ALB mRNA were present in all hepatocytes.  相似文献   
77.
BackgroundChronic kidney disease (CKD) has a negative impact on growth and development in children and is a risk factor for neurocognitive impairment; however, there is limited research on the cognitive function of children and adolescents with CKD. This study therefore aimed to investigate the mean intelligence and risk factors for low intelligence in children and adolescents with CKD.MethodsEighty-one patients with CKD under 18 years old were included in the KoreaN cohort study for Outcomes in patients With Pediatric Chronic Kidney Disease (KNOW-Ped CKD). Participants completed either the Wechsler Intelligence Scale for Children (6–16 years), or Wechsler Adult Intelligence Scale (> 16 years).ResultsThe mean full-scale intelligence quotient (IQ) was 91 ± 19; 24.7% of participants scored a full-scale IQ below 80. Participants with a short stature (height Z scores < −1.88), failure to thrive (weight Z scores < −1.65), more severe CKD stage (≥ IIIb), longer duration of CKD (≥ 5 years), and those who were Medicare or Medicaid beneficiaries, had significantly lower mean full-scale IQs.ConclusionOn linear regression analysis, the association between the full-scale IQ, and longer duration of CKD and growth failure, remained significant after controlling for demographic and clinical variables. It is therefore necessary to investigate cognitive impairment in pediatric patients with CKD who exhibit growth failure or for a longer postmorbid period. It is believed that early interventions, such as kidney transplantation, will have a positive effect on IQ in children with CKD, as the disease negatively affects IQ due to poor glomerular filtration rate over time.Trial RegistrationClinicalTrials.gov Identifier: NCT02165878  相似文献   
78.
79.
A case of primary seminal vesicle carcinoma is reported. The tumor was a CA125-producing adenocarcinoma consisting of fine papillary-tubular, intricate branching or anastomosing glandular structures and was composed of small cuboidal, but occasionally hobnailed, cells with mostly clear, but occasionally granular, cytoplasm. Some tumor cells showed evidence of secretion of seromucinous materials into the interpapillary and cystic space. lmmunohistochemically, almost half of the tumor cells expressed a positive reaction with anti-CAl25, a common serological marker for ovarian epithelial carcinomas; however, no tumor cells expressed any other serological tumor markers such as carcinoem-bryonic antigen, α-fetoprotein, human chorionic gonadotropin, prostatic specific acid phosphatase, or prostatic specific antigen. The patient showed a high level of serological CA125, which fluctuated parallel with the growth, removal and recurrence of the tumor. The morphological and immunohistochemical findings suggested a close relationship between the present tumor and clear cell carcinoma of the ovary, which is thought to be of a Müllerian-Wolfian duct origin.  相似文献   
80.
Attenuation of retinal photooxidative damage in thioredoxin transgenic mice   总被引:6,自引:0,他引:6  
Thioredoxin (TRX) is an endogenous redox (reduction/oxidation) regulator that has cytoprotective effects against various types of oxidative stresses. Exposure to excessive levels of white light induces retinal photoreceptor damage. To test the cytoprotective effect of overexpressed TRX against retinal photooxidative damage, both TRX transgenic (trx-tg) mice and C57BL/6 (wild type) mice were exposed to intense white fluorescent light. The amounts of oxidized and tyrosine-phosphorylated proteins decreased in the neural retinas of the trx-tg mice compared to the wild type mice after light exposure. The electroretinographic amplitudes were higher and the formation of oxidized DNA was lower in trx-tg mice compared to wild type mice after light exposure. These results suggest that overexpression of TRX suppresses retinal photooxidative damage. TRX intensification may be a useful therapeutic strategy to prevent retinal photic injury.  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