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   47579篇
  免费   3837篇
  国内免费   113篇
耳鼻咽喉   378篇
儿科学   1913篇
妇产科学   1298篇
基础医学   6820篇
口腔科学   978篇
临床医学   6538篇
内科学   9277篇
皮肤病学   901篇
神经病学   4837篇
特种医学   1086篇
外科学   4157篇
综合类   416篇
一般理论   63篇
预防医学   5846篇
眼科学   673篇
药学   2666篇
  2篇
中国医学   54篇
肿瘤学   3626篇
  2024年   62篇
  2023年   427篇
  2022年   588篇
  2021年   1276篇
  2020年   939篇
  2019年   1407篇
  2018年   1539篇
  2017年   1206篇
  2016年   1337篇
  2015年   1409篇
  2014年   1798篇
  2013年   2637篇
  2012年   3676篇
  2011年   3790篇
  2010年   2073篇
  2009年   1853篇
  2008年   3086篇
  2007年   3172篇
  2006年   3104篇
  2005年   2926篇
  2004年   2829篇
  2003年   2606篇
  2002年   2338篇
  2001年   385篇
  2000年   284篇
  1999年   334篇
  1998年   530篇
  1997年   397篇
  1996年   352篇
  1995年   344篇
  1994年   270篇
  1993年   268篇
  1992年   191篇
  1991年   164篇
  1990年   153篇
  1989年   119篇
  1988年   129篇
  1987年   97篇
  1986年   102篇
  1985年   108篇
  1984年   104篇
  1983年   108篇
  1982年   134篇
  1981年   123篇
  1980年   105篇
  1979年   65篇
  1978年   69篇
  1977年   50篇
  1976年   45篇
  1972年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
The subthalamic nucleus plays a pivotal role in the regulation of basal ganglia output. Recent electrophysiologic, lesion and immunocytochemical studies suggest that the subthalamic nucleus uses an excitatory amino acid as a neurotransmitter. After complete ablation of the subthalamic nucleus, we have examined the NMDA, AMPA, kainate and metabotropic subtypes of excitatory amino acid receptors in two major subthalamic projection areas (globus pallidus and substantia nigra pars reticulata) with quantitative autoradiography. Two weeks after ablation, binding sites for [3H]AMPA and [3H]kainate increased in substantia nigra pars reticulata ipsilateral to the lesion. In globus pallidus on the lesioned side, [3H]glutamate binding to the NMDA recognition site decreased. The results suggest that glutamate receptors regulate after interruption of subthalamic nucleus output.  相似文献   
94.
95.
96.
To learn and teach about HIV/AIDS is to enter complex and senstitive territory that at times may be personally challenging. 5 In the vast literature on HIV infection and nursing two main themes recur: nurses' lack of understanding, negative attitudes and anxieties related to HIV/AIDS and the need for education to change such attitudes and enhance nurses' knowledge and skills.  相似文献   
97.
Abstract The anti-inflammatory properties of triclosan have been revealed in several recent studies, including an effect on histamine-induced inflammation. In other studies, the nature of the solvent has been shown to be of importance for the plaque inhibiting as well as the antibacterial potential of triclosan. This study was aimed at examining whether the nature of the solvent also may influence the anti-inflammatory capacity of triclosan and further to study a possible dose/response relationship. The study was performed as 3 separate, double-blind experiments, comprising 10, 11 and 12 healthy females. In all 3 experiments, 5 sites on the lower part of the back of the volunteers were intradermally exposed to one drop of 1% histamine dihydrochloride for 15 min. The size of the resulting wheals was recorded before and after 40 min of triclosan treatment. In experiment I. 4 different concentrations of triclosan in 2-fold dilutions in absolute alcohol (0.125%-1%) were applied on the histamine-induced wheals. In experiments 2 and 3, 4 different solutions containing 0.5% triclosan and a saline solution as negative control were used. The solvents in experiment 2 were as follows: (1) absolute alcohol (positive control). (2) propylene glycol (PG), (3) polyethylene glycol (PEG). (4) olive oil, and in experiment 3: (1) absolute alcohol (positive control). (2) Tween 80. (3) sodium carbonate, (4) soy oil. The results showed a dose/ response effect of triclosan and further that the solvent may be of importance for its anti-inflammatory potential.  相似文献   
98.
A majority of a cohort of 62 children and adolescents who had been hospitalized in a state psychiatric facility was found to have received less restrictive services such as outpatient mental health services prior to their index admission. Also, a number had been involved with the juvenile justice system and almost two-thirds had been placed out-of-home. Ninety percent had at least one prior psychiatric hospitalization. Just over half of the cohort received case management and individual counseling post release. About a third received family counseling, and a few received other types of services. At least a third were rehospitalized within a year of release. Although 90% of the cohort received some type of service post release, a higher proportion of non service receivers were rehospitalized than service receivers. Even those who received services had a high rate of rehospitalization. These findings raise questions as to the appropriateness of service provision during and following hospitalization.This study was funded by a grant from the Office of Program Evaluation and Research, Ohio Department of Mental Health.  相似文献   
99.
BACKGROUND: Photon energy recovery (PER) is a spectral deconvolution technique validated for scatter removal in patients and phantom studies. The purpose of this study was to examine the impact of PER on left ventricular volume measurement based on myocardial perfusion single photon emission computed tomography (SPECT). METHODS AND RESULTS: SPECT acquisitions were performed by use of a static cardiac phantom and in 25 patients after a rest injection of technetium 99m sestamibi by use of multiple energy windows (126-136, 137-144, and 145-154 keV). Data were successively reconstructed with and without PER, by use of iterative reconstruction and post-processing filtering (Butterworth filter; order, 5; cutoff, 0.30 cycles/pixel). Image contrast was evaluated in reconstructed data, and volumes were calculated by use of QGS. PER increased reconstructed image contrast from 62% +/- 2.7% to 84.3% +/- 5.7% in the phantom studies (P <.0001) and from 49% +/- 2% to 73% +/- 2% in patients (P <.0001). Although it remained underestimated (P <.0001), phantom volume was higher after PER correction compared with uncorrected data (50.9 +/- 0.8 mL vs 44.6 +/- 1 mL, P <.0001). The error in volume measurement was decreased by PER correction (16.6% +/- 1.3% vs 27% +/- 1.7% [uncorrected data], P <.0001). In patients, left ventricular volume increased from 83 +/- 10 mL to 91 +/- 10 mL (P <.0001), and the PER-induced volume increase was correlated with the image contrast increase (r = 0.61, P =.001). Finally, the percentage of volume increase was higher in patients with small left ventricular volumes. CONCLUSIONS: PER has a significant impact on image contrast and left ventricular volume measurement by use of perfusion SPECT. PER improves the accuracy of phantom volume assessment. In patients, volume increase is correlated to image contrast increase and is higher in those with small ventricles.  相似文献   
100.
Recent studies have shown inflammatory markers in affected neural tissues of amyotrophic lateral sclerosis (ALS) patients. We examined immunocytochemically spinal cord tissues of six patients with ALS, two with corticospinal tract degeneration secondary to cerebral infarcts and three control subjects without neuropathologic abnormalities. ALS spinal cords had dense macrophage infiltration (one log greater than control spinal cords) involving the white and gray matter, with heaviest infiltration of lateral and ventral columns and, in one patient, prefrontal gyrus and the occipital lobes of the brain. Macrophages in ALS spinal cord showed strong expression of cyclooxygenase-2 (COX-2) (one log greater than control tissues) and inducible nitric oxide synthase. In the gray matter, macrophages surrounded and appeared to phagocytize neurons (NeuN-positive) that appeared to be dying. Vessels showed damage to the tight junction protein ZO-1 in relation to perivascular CD40 receptor-positive macrophages and CD40 ligand-positive T lymphocytes. ALS spinal cords, but not control cords, were sparsely infiltrated with mast cells. In control cases with corticospinal tract degeneration following hemispheric cerebral infarction, macrophage infiltration of the white matter was COX-2-negative and restricted to lateral and anterior corticospinal tracts. Our data suggest that inflammation in ALS spinal cord and cortex is based on innate immune responses by macrophages and mast cells and adaptive immune responses by T cells.  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