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   1333篇
  免费   56篇
耳鼻咽喉   42篇
儿科学   99篇
妇产科学   33篇
基础医学   164篇
口腔科学   66篇
临床医学   96篇
内科学   226篇
皮肤病学   14篇
神经病学   97篇
特种医学   64篇
外科学   208篇
综合类   38篇
预防医学   73篇
眼科学   8篇
药学   101篇
中国医学   9篇
肿瘤学   51篇
  2023年   8篇
  2022年   27篇
  2021年   43篇
  2020年   22篇
  2019年   32篇
  2018年   39篇
  2017年   27篇
  2016年   35篇
  2015年   38篇
  2014年   48篇
  2013年   68篇
  2012年   56篇
  2011年   86篇
  2010年   52篇
  2009年   41篇
  2008年   69篇
  2007年   69篇
  2006年   71篇
  2005年   63篇
  2004年   57篇
  2003年   47篇
  2002年   40篇
  2001年   27篇
  2000年   32篇
  1999年   30篇
  1998年   11篇
  1997年   8篇
  1996年   5篇
  1995年   8篇
  1994年   5篇
  1992年   24篇
  1991年   14篇
  1990年   17篇
  1989年   18篇
  1988年   8篇
  1987年   14篇
  1986年   10篇
  1985年   19篇
  1984年   13篇
  1983年   8篇
  1982年   6篇
  1979年   9篇
  1978年   6篇
  1977年   4篇
  1974年   5篇
  1973年   7篇
  1972年   6篇
  1971年   5篇
  1970年   6篇
  1965年   3篇
排序方式: 共有1389条查询结果,搜索用时 15 毫秒
1.
2.
We studied 14 patients with obsessive-compulsive disorder (OCD) by positron emission tomography and the fluorodeoxyglucose method, looking for abnormalities in local cerebral metabolic rates for glucose in brain structures that have been hypothesized to function abnormally in OCD. These patients were compared with 14 normal controls and 14 patients with unipolar depression. The patients with unipolar depression and OCD did not differ in levels of anxiety, tension, or depression. In OCD, metabolic rates were significantly increased in the left orbital gyrus and bilaterally in the caudate nuclei. This was apparent on all statistical comparisons with both controls and unipolar depression. The right orbital gyrus showed at least a trend to an increased metabolic rate in all comparisons. The metabolic rate in the left orbital gyrus, relative to that in the ipsilateral hemisphere (orbital gyrus/hemisphere ratio), was significantly elevated compared to controls and subjects with unipolar depression, and stayed high even with successful drug treatment. Though it was in the normal range in the morbid state, with improvement in OCD symptoms after drug treatment, the caudate/hemisphere metabolic ratio increased uniformly and significantly bilaterally. This ratio did not increase in patients who did not respond to treatment. Thus, OCD showed cerebral glucose metabolic patterns that differed from controls in both the symptomatic and recovered states.  相似文献   
3.
Gastric teratoma is a very rare benign tumor. Fifty-three cases, only two of which were females, have previously been reported. This report concerns two cases of teratoma arising from stomach. One of them is the third female case described in the literature.  相似文献   
4.
5.
We show here that T cell cross-reactivity between heterologous viruses influences the immunodominance of virus-specific CD8(+) T cells by two mechanisms. First, T cells specific for cross-reactive epitopes dominate acute responses to viral infections; second, within the memory pool, T cells specific for cross-reactive epitopes are maintained while those specific for non-cross-reactive epitopes are selectively lost. These findings suggest an immunological paradigm in which viral infections shape the available T cell repertoire, causing alterations in the hierarchies of both the primary and memory CD8(+) T cell responses elicited by subsequent viral infections. Thus, immunodominance is a function of the host's previous exposure to unrelated pathogens, and this may have an impact on protective immunity and immunopathology.  相似文献   
6.
7.
Administration of caffeine (1,3,7-trimethylxanthine), a major component of coffee, to Swiss mice at doses of 80 or 100 mg/kg body weight 60 min prior to whole-body lethal dose of gamma-irradiation (7.5 Gy) resulted in the survival of 70 and 63% of animals, respectively, at the above doses in contrast to absolutely no survivors (LD-100/25 days) in the group exposed to radiation alone. Pre-treatment with a lower concentration of caffeine (50 mg/kg) did not confer any radioprotection. The protection exerted by caffeine (80 mg/kg), however, was reduced from 70 to 50% if administered 30 min prior to irradiation. The trend statistics reveal that a dose of 80 mg/kg administered 60 min before whole-body exposure to 7.5 Gy is optimal for maximal radioprotection. However, caffeine (80 mg/kg) administered within 3 min after irradiation offered no protection. While there is documentation in the literature that caffeine is an antioxidant and radioprotector against the oxic pathway of radiation damage in a wide range of cells and organisms, this is the first report demonstrating unequivocally its potent radioprotective action in terms of survival of lethally whole-body irradiated mice.  相似文献   
8.
Guineaworm control case study: planning a multi-strategy approach   总被引:2,自引:0,他引:2  
The planned global eradication of guineaworm (dracunculiasis) offers opportunities to learn about relatively complicated disease control situations. Unlike smallpox, which was eradicated over 10 years ago through immunization, the guineaworm problem has no one solution, but must rely on a variety of technologies to protect, treat or replace existing unsafe community water supplies which harbour the disease. Experiences in rural Nigeria have shown that a multi-strategy approach is necessary to account for differences in geographical settlement patterns, local culture and beliefs, geology of the area, economy of the villages and political clout of town leaders among the five major segments of the community. Through a self-help primary health care programme, residents of the Idere community were able to dig wells, produce and distribute cloth water filters bringing a reduction in disease incidence in some areas. It was also seen that generally low standards of living exacerbated by scattered outlying settlements made self-help difficult. Unfortunately occasional government and private efforts did not succeed because of a lack of community participation. Programme planners must involve the consumers in diagnosing these community characteristics and in planning, supervising and maintaining the resulting projects. The multi-strategy approach will help avoid wasted resources and false expectations that arise when project staff attempt to apply a "magic bullet" solution to a complex problem.  相似文献   
9.
Objective. To review imaging studies of isolated involvement of the sacrum due to tuberculosis and determine the role of imaging in the diagnosis and management of these patients. Design and patients. A retrospective analysis of 15 cases of isolated sacral tuberculosis imaged with MR imaging was performed. The CT images were also reviewed where available, and the various lesion characteristics were identified. We also reviewed the medical records in an attempt to determine the impact of the imaging studies on the management of these patients. Results. Fifteen patients (5 male, 10 female) presented with symptoms of 3–15 months’ duration. Chronic localized backache with muscle spasm was the commonest presenting symptom; discharging sinuses with abscess formation was found in six patients, five of whom were children. MR imaging of the sacrum revealed a hypointense marrow signal on T1-weighted images and hyperintense signal on T2-weighted images in 14 of 15 patients, the S2 vertebra being always involved. CT revealed osteolytic changes in the sacrum in all the five patients in whom CT was performed. All patients showed marked clinical improvement within 1 year of anti-tuberculous chemotherapy. Conclusion. Isolated tuberculosis of the sacrum is uncommon but should be suspected in patients presenting with chronic low backache or children with discharging sinuses/abscesses and showing sacral destruction on CT or MR imaging. MR imaging can identify cases and enables early institution of anti- tuberculous chemotherapy. Received: 31 August 1999 Revision requested: 1 November 1999 Revision received: 27 March 2000 Accepted: 14 April 2000  相似文献   
10.
The influence of natural beta-cyclodextrin and its hydrophilic derivatives (HPbetaCd and SBE7betaCd) on the in vitro dissolution rate, in vivo absorption and oral bioavailability of a poorly water soluble anti-inflammatory agent, valdecoxib (VALD) was studied. Equimolar drug-cyclodextrin solid complexes were prepared by kneading and coevaporation methods and characterized by infrared spectroscopy, differential scanning calorimetry, X-ray diffraction. In the liquid state, the cyclodextrin complexes were studied using phase solubility analysis, (1)H nuclear magnetic resonance and circular dichroism spectroscopy. Drug solubility and dissolution rate in distilled water were notably improved by employing the betaCds. The DP(15) (i.e. percent of dissolved VALD at 15 min) was 10.5% for the pure drug and 50, 91 and 93% for VALD-betaCd, VALD-HPbetaCd and VALD-SBE7betaCd complexes, respectively. Moreover, it was found that in the, the cyclodextrin complexes of drug showed significant improvement in the anti-inflammatory activity.  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