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   8172篇
  免费   645篇
  国内免费   22篇
耳鼻咽喉   124篇
儿科学   245篇
妇产科学   150篇
基础医学   1037篇
口腔科学   218篇
临床医学   825篇
内科学   1623篇
皮肤病学   188篇
神经病学   711篇
特种医学   213篇
外国民族医学   1篇
外科学   1152篇
综合类   46篇
一般理论   3篇
预防医学   764篇
眼科学   152篇
药学   488篇
中国医学   29篇
肿瘤学   870篇
  2023年   53篇
  2022年   90篇
  2021年   229篇
  2020年   129篇
  2019年   253篇
  2018年   292篇
  2017年   198篇
  2016年   213篇
  2015年   247篇
  2014年   322篇
  2013年   404篇
  2012年   484篇
  2011年   515篇
  2010年   302篇
  2009年   270篇
  2008年   445篇
  2007年   448篇
  2006年   402篇
  2005年   386篇
  2004年   361篇
  2003年   325篇
  2002年   304篇
  2001年   189篇
  2000年   215篇
  1999年   168篇
  1998年   82篇
  1997年   64篇
  1996年   45篇
  1995年   52篇
  1994年   50篇
  1993年   56篇
  1992年   110篇
  1991年   119篇
  1990年   106篇
  1989年   121篇
  1988年   79篇
  1987年   83篇
  1986年   67篇
  1985年   55篇
  1984年   59篇
  1983年   29篇
  1982年   37篇
  1981年   38篇
  1980年   26篇
  1979年   47篇
  1977年   30篇
  1976年   31篇
  1974年   22篇
  1972年   21篇
  1971年   27篇
排序方式: 共有8839条查询结果,搜索用时 15 毫秒
991.
The radiosensitivity of two variants of the Dunning Copenhagen rat prostatic tumor R3327 was investigated. The R3327-AT variant, which is a poorly differentiated anaplastic, fast-growing tumor, was irradiated both in vivo and in vitro. Following irradiation, monodispersed cells were plated in vitro and colonies were counted after 7 days. The survival curve of R3327-AT cells irradiated in vivo showed an initial shoulder (Dq-value 0.97 Gy), followed by two exponential parts. The D0-value for the first part of the curve (0-10 Gy) was 2.76 Gy and for the second part of the curve (greater than 10 gy) 9.05 Gy. Extrapolation of the second part of the curve to the Y-axis indicated that the proportion of more radioresistant cells was about 10%. The survival curve for R3327-AT cells irradiated in vitro also suggested the presence of a radioresistant subpopulation, although the proportion was lower (about 3%). This difference might be due to the presence of an hypoxic fraction in the tumors irradiated in vivo, but not in vitro. Tumor cells from the R3327 tumor variant metastatic to lymph nodes and lungs (R3327-MATLyLu), were irradiated in vitro. The radiation effect was evaluated by in vitro colony formation in agar and by in vivo lung colony assay. The colony formation in agar yielded a D0-value of 1.09 Gy. No radioresistant subpopulation was identified in this variant. A similar radiosensitivity was observed by the in vivo lung colony assay (D0 1.39 Gy). The mean inactivation dose calculated for R3327-AT cells (3.45 Gy) was significantly higher than for the metastatic variant (2.00 Gy).  相似文献   
992.
The objective of this study was to develop an anthropometry-based prediction model for the assessment of bone mineral content (BMC) in children. Dual-energy X-ray absorptiometry (DXA) was used to measure whole-body BMC in a heterogeneous cohort of 982 healthy children, aged 5-18 years, from three ethnic groups (407 European- American [EA], 285 black, and 290 Mexican-American [MA]). The best model was based on log transformations of BMC and height, adjusted for age, gender, and ethnicity. The mean +/- SD for the measured/predicted in ratio was 1.000 +/- 0.017 for the calibration population. The model was verified in a second independent group of 588 healthy children (measured/predicted In ratio = 1.000 +/- 0.018). For clinical use, the ratio values were converted to a standardized Z score scale. The whole-body BMC status of 106 children with various diseases (42 cystic fibrosis [CF], 29 juvenile dermatomyositis [JDM], 15 liver disease [LD], 6 Rett syndrome [RS], and 14 human immunodeficiency virus [HIV]) was evaluated. Thirty-nine patients had Z scores less than -1.5, which suggest low bone mineral mass. Furthermore, 22 of these patients had severe abnormalities as indicated by Z scores less than -2.5. These preliminary findings indicate that the prediction model should prove useful in determining potential bone mineral deficits in individual pediatric patients.  相似文献   
993.
We present a case of dorsoradial skin loss over the middle phalanx of the middle finger with section of the central slip of the extensor tendon and loss of one lateral band following mechanical injury. Successful primary reconstruction of the central slip was performed by retrograde flap from the central slip of the extensor tendon tied with barb-wire over a padded button, splinted for 2 weeks with a K-wire, and skin cover with a dorsocommissural flap based on the second web space. Other reconstructive options are discussed.  相似文献   
994.
 A 1-year prospective analysis of patient adherence to antiretroviral therapy (zidovudine plus zalcitabine [55 patients] or zidovudine plus zalcitabine plus saquinavir [32 patients]) was performed in human immunodeficiency virus (HIV)-infected patients attended at a tertiary care hospital. Adherence to therapy was measured jointly by pharmacy records, patients' self-recording, and an increase in mean corpuscular volume. Likewise, the effects of therapy on clinical parameters, HIV load, CD4+ cell count, and serum levels of tumor necrosis factor alpha (TNF-α) and its soluble receptors were analyzed. Twenty-seven patients of those on a double-agent regimen and 12 of those on a triple-agent regimen adhered to the treatment. Ten opportunistic events occurred in noncompliant patients versus none in compliant individuals. A significant increase in CD4+ cell count and a decrease in HIV viral load were observed only in patients who adhered to therapy. TNF and its soluble receptors remained elevated at the end of follow-up, even in patients in whom the HIV viral load decreased to <400 copies/ml. In conclusion, adherence to therapy must be considered a major factor influencing the results of antiretroviral therapy. Although these treatments have been demonstrated to be efficacious, they are not able to normalize the immune activation markers. These data suggest a suboptimal effect of antiretroviral therapy on the eradication of HIV-1.  相似文献   
995.
The modulating effect of As (As2O3) in drinking water plus dietary fatty acids on benzo-a-pyrene (BP) induced forestomach tumorigenesis was assayed in mice fed with corn oil (CO), Olein (O), palmstearin (PS) and cod liver oil (CLO) enriched formulae, and a mixed-fat (S-stock) diet during 28 weeks. Neither pre-or neoplastic lesions were recorded in esophagus or forestomach of mice treated with As alone. CLO diet showed a protective effect. Indeed, multiple epidermal hyperplasia were significantly reduced compared to S group and a reduction in papillomas multiplicity with respect to S, CO and O groups was also observed. Mice fed on PS formula showed minor papillomas per mouse with respect to CO and O. These results indicate that As plus BP did not exhibit any synergistic effect on the development of epidermoid tumor lesions, whereas CLO diet exerted antipromoting activity . In spite of their common essential fatty acid deficiency (EFAD) condition, PS and O lots showed contradictory results. Hence, the dietary enrichment in 18:1 n-9 (O diet) per se, and not the EFAD state, may play a deleterious role. Corn diet showed no promoting activity on the epidermoid tumor development in this model.  相似文献   
996.
Abnormalities in the cAMP-dependent protein kinase (PKA), a central component of cAMP signaling, have been reported in several psychiatric disorders. Previous studies showed cAMP signaling alterations in schizophrenic patients but less is known about the involvement of PKA in such disorder. Therefore, we investigated the PKA subunits by Western blot analysis in platelets from 12 patients with schizophrenia and 13 controls. The results showed that the immunolabeling of the PKA regulatory subunits type I (RI) and type II (RII) was significantly reduced in patients compared with controls whereas no differences were observed in the catalytic (C) subunit of the enzyme. These preliminary data suggest that schizophrenic patients have altered PKA levels, thus supporting that dysfunctions in the components of cAMP signaling may contribute to the pathophysiology of schizophrenia.  相似文献   
997.
OBJECTIVE: At this moment, in the Netherlands, rescue workers are not given any specific standardized training in disaster response or disaster management.After the café fire in Volendam, the Netherlands, on New Year's Eve 2000, around 200 rescue workers were deployed on-site. The aim of this study is to investigate the rescue workers' experiences with regard to their level of preparation for the emergency response. METHODS: In 2002, 30 members of the medical and paramedical personnel were requested to participate in a structured interview, focused on education, task perception, triage and registration. RESULTS: Twenty-seven participated. Twenty-two rescue workers received previous training in emergency medicine. During the alarm phase, 11 rescue workers had a clear perception of their tasks. Twenty-four were involved in triage and injury assessment. Three rescue workers used a protocol for triage and 15 for injury assessment. Twenty-five rescue workers gave on-scene treatment and 15 used a protocol. Eight registered their findings. CONCLUSIONS: Preparation for the emergency response lacked standardized procedures. The use of triage protocols was extremely poor, as was documentation of actions. Slightly more than half of the personnel followed treatment protocols. It is advisable that all rescue workers become familiar with the basic uniform principles and protocols regarding disaster management. A dedicated and standardized national disaster management course is needed for all rescue workers.  相似文献   
998.
Thirteen patients with clinically and radiographically defined right middle cerebral artery infarction were studied using EEG, quantitative electroencephalographic (QEEG) spectra, and multi-channel evoked potentials. The purpose of this effort was to develop QEEG rules that related to the patient's neurologic status. Three QEEG relative delta spectral patterns were identified in the right hemisphere which related to neurologic residua. These include limited perisylvian involvement, mixed involvement of perisylvian and extrasylvian regions, and extrasylvian involvement only. While there were parallels between QEEG spectral patterns and auditory, visual and somatosensory evoked potentials, there were modality specific features consistent with functional differences.  相似文献   
999.
1000.
Since 1987, 10 patients have been treated with irradiation to a limited pelvic volume for elevation of serum prostate-specific antigen (PSA) level above expected post-radical prostatectomy levels without clinical or radiological evidence of either metastatic or locoregional disease. The patients were treated 3 to 43 months after radical prostatectomy, using bilateral 120 degrees arcs to deliver 6000 cGy to the prostatic bed. The pathologic findings of the initial surgical specimens for all patients were reviewed. Eight patients had pathologic Stage C disease, and five patients had one or more positive margins. All patients had negative staging lymphadenectomies. After irradiation, eight patients had decreases in PSA levels indicative of response of isolated local disease. Through preliminary, these results suggest that post-prostatectomy PSA levels are useful for detecting subclinical local recurrence or persistence in the prostatic bed, as well as monitoring these patients' response to therapy. The value of this elective treatment remains to be documented.  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