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   1192篇
  免费   81篇
  国内免费   4篇
耳鼻咽喉   5篇
儿科学   6篇
妇产科学   8篇
基础医学   155篇
口腔科学   18篇
临床医学   120篇
内科学   247篇
皮肤病学   9篇
神经病学   328篇
特种医学   12篇
外科学   213篇
综合类   1篇
预防医学   41篇
眼科学   3篇
药学   65篇
肿瘤学   46篇
  2023年   8篇
  2022年   11篇
  2021年   15篇
  2020年   11篇
  2019年   9篇
  2018年   18篇
  2017年   25篇
  2016年   28篇
  2015年   27篇
  2014年   21篇
  2013年   62篇
  2012年   70篇
  2011年   70篇
  2010年   33篇
  2009年   31篇
  2008年   56篇
  2007年   72篇
  2006年   68篇
  2005年   65篇
  2004年   79篇
  2003年   49篇
  2002年   44篇
  2001年   42篇
  2000年   36篇
  1999年   33篇
  1998年   16篇
  1997年   10篇
  1996年   16篇
  1995年   4篇
  1994年   6篇
  1993年   11篇
  1992年   14篇
  1991年   24篇
  1990年   25篇
  1989年   22篇
  1988年   17篇
  1987年   18篇
  1986年   17篇
  1985年   13篇
  1984年   8篇
  1983年   4篇
  1982年   8篇
  1981年   6篇
  1980年   5篇
  1979年   11篇
  1978年   5篇
  1977年   5篇
  1976年   8篇
  1975年   6篇
  1974年   3篇
排序方式: 共有1277条查询结果,搜索用时 15 毫秒
91.
The performance of biomedical assays at both molecular and cellular level depends greatly on the ability to design new polymer surfaces. Patterns can be created by using materials with contrasted surface properties. In this work we describe in detail the preparation of micropatterned surfaces to be used as tissue engineering supports. Poly(ethylene glycol) (PEG) was used as the 'anti-fouling' polymer in opposition to functional regions covered by acrylic acid (AAc). Since spin-casted PEG films are unstable, ion beam stabilization (IBS) treatment was applied in order to render it insoluble. On the other hand, AAc films were deposited by low-power plasma chemical vapour deposition. Chemical properties of both polymers were monitored by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy while topographic features were followed by atomic force microscopy. Finally, a micropattern was produced by using a mask, which isolated the IBS-PEG from the AAc-deposited regions. Endothelial cells cultured on the surface were observed to follow the micropatterns. In fact, for a certain surface density it was observed that the cells present tensile or compressive stresses when forced to remain in the anti-fouling or the functionalised regions, respectively.  相似文献   
92.
BACKGROUND AND AIMS: Vitamin D deficiency is a well-known risk for hip fracture, and vitamin D insufficiency is so frequent in the elderly that population-wide preventive intervention would be useful. The objective of the study was to evaluate the efficacy of vitamin D bolus on hip fracture incidence in elderly women. METHODS: All women aged > 65 years registered at Health District 20 of the Regione Veneto, Italy, were eligible for this quasi-experimental, prospective community intervention study. A vial containing 400,000 IU vitamin D2 (Ostelin 800, Teofarma, Italy) was offered for oral administration to all women in the winters of 2000-2001 and 2001-2002. The only exclusion criteria for treatment were age and gender, and the control group included women who did not participate in the Health District initiative. Analysis of hip fracture incidence was carried out for 4 years, from 1999 to 2002. Patients with incident hip fracture were identified as soon as they were admitted to one of the 3 hospitals of the health district and interviewed regarding their participation in the vitamin D preventive intervention program. In 120 of the women (age range 68-90 years), serum concentrations of 25-OH vitamin D were measured from October to June, both before and 1 and 4 months after vitamin D administration. RESULTS: 23,325 and 24,747 women received the vitamin D bolus during winters 2000-2001 and 2001-2002 respectively, i.e. 45-47% of eligible women. The proportion of women who accepted the bolus declined with advancing age, from 50-55% in women aged 60-70 years to 22-26% in those aged > 90 years. The two-year intervention on the community decreased the incidence of fracture by 10% (p = 0.050) in comparison with the previous two years. The age-adjusted risk reduction (RR) of hip fracture during 2001 and 2002 in women who had received vitamin D, with respect to women who had not, decreased by 17% (p = 0.056) and 25% (p = 0.005) respectively. The RR was considerably greater and statistically significant over both 2001 and 2002 in the cohort aged > 75 years. 25-OH vitamin D concentrations, in the subset of women in whom it was measured, rose significantly (p < 0.0001) by 9 ng/ml over 4 months after administration. CONCLUSION: Despite several obvious limitations due to its nature, this study sufficiently documents that yearly vitamin D bolus supplements, given as primary prevention to elderly Caucasian women, may decrease the incidence of hip fracture. For its probable safety and excellent feasibility and cost-effectiveness, this primary intervention has a great potential for generalisability.  相似文献   
93.
Besides polysomnographic techniques, other neurophysiological methods have been utilized in order to understand the pathophysiology of restless legs and periodic limb movement syndromes. By using electromyography with nerve conduction velocity (EMG-CV) and somatosensory evoked potentials (SEPs) it has been possible to determine how frequently each muscle was involved in periodic limb movements, how frequently EMG activity started in a given muscle and the time delay and pattern of activation between the first and the other activated muscles. The etiology of symptoms does not involve structural lesions since brainstem and spinal pathways are intact. Recent evidence from paired transcranial magnetic stimulation suggests that the pathophysiological key in sleep motor disorders is a modified global excitability of corticospinal pathways. The next neurophysiological goal will be to localize the unresolved anatomical level of sleep disorder movement generators and to describe their mechanism.  相似文献   
94.
95.
Safety profile of recombinant canarypox HIV vaccines   总被引:1,自引:0,他引:1  
Attenuated poxviruses have been developed for use as candidate vaccine vectors. ALVAC, a strain of the Avipoxvirus canarypox, has been extensively evaluated as a vector for vaccines against the human immunodeficiency virus type 1 (HIV-1). This report presents the safety and reactogenicity data derived from 11 multicenter, randomized controlled trials of ALVAC-HIV vaccines conducted by the HIV Vaccine Trials Network (HVTN) and its predecessor, the AIDS Vaccine Evaluation Group (AVEG). Five different ALVAC vaccine constructs were tested among 1497 volunteers. Reactogenicity was similar for different ALVAC constructs. Local reactions of any grade to ALVAC vaccines were common. However, fewer than 2% of vaccinees had severe local responses, and less than 1% experienced severe local pain or tenderness. Systemic responses were mild and transient. As combination vaccine regimens are in common use, we also evaluated side effects of ALVAC vectors given in combination with a recombinant subunit protein. No significant differences were noted in the reactogenicity of ALVAC given with or without a recombinant envelope subunit vaccine. Black, non-Hispanic and male recipients of ALVAC-HIV reported less pain following vaccination than White, non-Hispanics and females, respectively. ALVAC-HIV vaccines are well tolerated at tested doses. The reactogenicity profiles are comparable to those reported for existing vaccines licensed for use among adults. Reactogenicity does not appear to be related to the number or type of inserted genes, and did not vary between different ALVAC constructs.  相似文献   
96.
In the present high-resolution electroencephalographic (EEG) study, we computed event-related desynchronization and synchronization (ERD/ERS) of alpha (about 10 Hz) and beta (about 20 Hz) rhythms in association with the execution (with visual feedback) and observation of brisk unilateral right and left aimless finger movements. A first scope was to test the topographical "functional equivalence" of cortical rhythmicity related to movement execution and observation, which would represent an ideal cortical observation/execution matching system. A second scope was to evaluate the hypothesis of a left or right hemisphere prevalence of the cortical rhythmicity related to the movement observation compared to the movement execution. EEG (128 electrodes) was recorded in 10 healthy right-handed volunteers. Surface Laplacian estimation spatially enhanced EEG data over a MRI-constraint head model. Under both conditions, ERD peaked during the movement execution or observation and was replaced by a ERS "rebound" or "recovery," which peaked during the postevent period. Topographical results are in favor of a "functional equivalence" (i.e., similar ERD/ERS values in magnitude and timing) of alpha and beta rhythmicity in central scalp regions overlying premotor/primary sensorimotor cortex. On the contrary, the functional equivalence of alpha rhythmicity was negligible (i.e., different ERD/ERS values in magnitude and timing) in parietal-occipital scalp regions overlying posterior parietal and parieto-occipital cortex, which could be the neural substrate to distinguish among the own motor intensions and others' aimless movements (i.e., visuomotor transformation integrated with sensorimotor, postural, and kinematics representations). Finally, the pattern of hemispherical cortical rhythmicity did not support a "simple concentration" of movement observation functions in the left or right hemisphere.  相似文献   
97.
Although it is well established that the diagnosis and treatment of depression in the elderly are major health care problems, the relative efficacy of antidepressant treatment in the elderly compared with younger adults has not been definitively established. In this study, we analyzed antidepressant response in 528 nondemented consecutive inpatients affected by a major depressive episode. The sample was divided based on a cut-off of 60 years (< or = 60 n = 354; mean age 46.6 +/- 10.4 years; > 60 n = 174; mean age 66.1 +/- 4.2 years); all the patients were treated with fluvoxamine for at least 6 weeks and they were assessed weekly by using the Hamilton Rating Scale for Depression. Fluvoxamine proved to be effective in our elderly sample, even if antidepressant response was lower in the elderly compared with that of younger subjects (chi2 = 6.27, P = 0.01). Moreover, when compared with younger subjects, the older ones showed significantly slower reduction of depressive symptoms (P = 0.0006). This difference between the 2 age groups was evident since the 2nd week of treatment, and it appeared to be independent of other clinical variables.  相似文献   
98.
BACKGROUND: A critical need exists for effective small-animal models that accept engraftment of human hematopoietic progenitor cells and mature lymphocytes. The purpose of this study was to determine the phenotypic effects of perforin (Pfp) deficiency on nonobese diabetic (NOD)-Rag1null mice and to evaluate the ability of NOD/LtSz-Rag1nullPfpnull recipients to support engraftment with human hematolymphoid cells. METHODS: A new genetic stock of NOD mice doubly homozygous for targeted mutations at the recombination activating gene (Rag)-1 and Pfp genes was developed. NOD/LtSz-Rag1nullPfpnull mice were studied for immunopathologic and hematologic abnormalities. The ability of these mice to support engraftment with human peripheral blood mononuclear cells (PBMC) and umbilical-cord blood hematopoietic progenitor cells was assessed. RESULTS: NOD/LtSz-Rag1nullPfpnull mice lacked mature B cells, T cells, natural killer (NK) cell cytotoxic activity and were devoid of serum immunoglobulin (Ig) throughout a 37-week lifespan. These mice supported heightened engraftment with human PBMC as compared with NOD/LtSz-Rag1null controls as evidenced by a 4- to 5-fold increase in percentages of human lymphocytes and a 7- to 13-fold increase in percentages of CD4+ T cells in the peripheral blood and spleen. Total numbers of human CD4+ T cells were increased approximately 20-fold in the spleens of NOD/LtSz-Rag1nullPfpnull mice. These mice also showed approximately 12-fold higher levels of engraftment with human umbilical-cord blood cells compared with NOD/LtSz-Rag1null mice. CONCLUSIONS: NOD/LtSz-Rag1nullPfpnull mice are devoid of mature B cell, T cell, and NK cell cytotoxic activity, engraft at high levels with human PBMC, and hematopoietic progenitor cells and provide a new NK cell-deficient model for human hematolymphoid cell engraftment.  相似文献   
99.
Type 1 diabetes in humans is a serious autoimmune disorder of children that is still poorly understood, unpreventable, and irreversible. Study of its animal models, notably the NOD mouse and BB rat, has generated a wealth of information concerning genetics and immunopathogenesis, but that information has still not altered the way in which we treat children with diabetes. In this review we attempt to identify the most promising avenues of continuing research in these models and the most important issues that must be faced by the designers of human therapies based on the animal dataset.  相似文献   
100.
Bisphosphonates have been used with success in the treatment of osteoporosis, but oral therapy often lacks compliance. Here we report the results of clinical trial with aminobisphosphonate neridronate administered intravenously (i.v.). The study included 78 postmenopausal women with spine bone mineral density (BMD) at least -2.5 SD below peak. Patients were randomized to receive for 2 years either 50 mg i.v. neridronate bimonthly and 500 mg calcium plus 400 U vitamin D supplements daily (n=39) or calcium-vitamin D supplements alone (control group, n=39). Treatment was continued over 2 years with an additional 1 year follow-up of calcium-vitamin D supplements alone. Neridronate was well tolerated with the appearance of typical clinical signs of an acute phase reaction in only 3 of the patients after the first infusion. In the control group no significant changes in BMD or bone markers were observed. In the neridronate group BMD rose progressively at the spine rose up to 7.4% +/- 6.1% (SD) and at the femoral neck up to 5.8% +/- 8.2% (SD) at the end of the second year. In the succeeding follow-up these gains were maintained at both skeletal sites. Serum bone alkaline phosphatase (bone ALP) and serum type I collagen C-telopeptide (s-CTX) significantly decreased within 2 months. The bone ALP values reached a -35% plateau after 6 months, while s-CTX attained the lowest mean value (-47%) only by the end of the treatment with neridronate. Both bone markers returned almost to baseline values 1 year after treatment discontinuation. Treatment of postmenopausal osteoporosis with 50 mg i.v. neridronate bimonthly results in clinically relevant increases in BMD, among the largest so far observed with any other bisphosphonate.  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