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   7476篇
  免费   314篇
  国内免费   33篇
耳鼻咽喉   77篇
儿科学   158篇
妇产科学   132篇
基础医学   951篇
口腔科学   176篇
临床医学   477篇
内科学   1868篇
皮肤病学   153篇
神经病学   927篇
特种医学   201篇
外科学   1126篇
综合类   23篇
预防医学   191篇
眼科学   180篇
药学   419篇
中国医学   10篇
肿瘤学   754篇
  2022年   50篇
  2021年   127篇
  2020年   80篇
  2019年   116篇
  2018年   144篇
  2017年   98篇
  2016年   99篇
  2015年   123篇
  2014年   184篇
  2013年   223篇
  2012年   341篇
  2011年   353篇
  2010年   205篇
  2009年   160篇
  2008年   291篇
  2007年   341篇
  2006年   298篇
  2005年   351篇
  2004年   287篇
  2003年   317篇
  2002年   289篇
  2001年   216篇
  2000年   252篇
  1999年   197篇
  1998年   82篇
  1997年   69篇
  1996年   55篇
  1995年   71篇
  1994年   71篇
  1993年   49篇
  1992年   179篇
  1991年   175篇
  1990年   153篇
  1989年   174篇
  1988年   153篇
  1987年   127篇
  1986年   117篇
  1985年   131篇
  1984年   104篇
  1983年   87篇
  1979年   79篇
  1978年   53篇
  1977年   57篇
  1976年   49篇
  1974年   51篇
  1973年   58篇
  1972年   53篇
  1970年   55篇
  1969年   56篇
  1968年   45篇
排序方式: 共有7823条查询结果,搜索用时 46 毫秒
131.
Seventeen 1,2,3,4-tetrahydroimidazo[1,5-a]pyrimidine derivatives bearing electron-withdrawing substituents were designed and synthesized by novel ring closure as potential antitumor agents. They were screened for their activities against mouse leukemia L1210 and human oral epidermoid carcinoma KB cell lines, and relationships of structure and antitumor activity in vitro are discussed. It was found that 8-thiocarbamoyl-1,2,3,4-tetrahydroimidazo[1, 5-a]pyrimidin-2(1H)-thione (8c) exhibited activity comparable to that of 5-fluorouracil against both L1210 and KB cells. The existence of both 2-thioxo and 8-substituent with a thioxo group in the molecule is crucial for the cytotoxicity against L1210 and KB cells. A novel procedure for introduction of a double bond between C-3 and C-4 in 8c was developed. Introduction of the 3,4-double bond increased the activity against L1210, but against KB cells the activity decreased by 4-fold. Cytotoxicity of compounds 8c and 8-thiocarbamoyl-1,2-dihydroimidazo[1,5-a]pyrimidin-2(1H)-thione (11c) against human solid tumor and leukemia cell lines was further evaluated. The saturation of the 3,4-double bond led to a significant increase in cytotoxicity against tumor cell lines tested.  相似文献   
132.
Nocturnal eating/drinking syndrome secondary to neuroleptic-induced restless legs syndrome (RLS) occurred under treatment with low-dose haloperidol in a 51-year-old female schizophrenic patient. Polysomnographic investigation showed a low level of sleep efficacy, periodic leg movements, and a strict relationship between nocturnal eating episodes and non-rapid eye movement sleep. Her nocturnal eating and RLS were completely inhibited by clonazepam treatment. To our knowledge, this is the first published case of nocturnal eating/drinking syndrome secondary to neuroleptic-induced RLS.  相似文献   
133.
To investigate the mechanism of synovial pannus formation in rheumatoid arthritis, immunohistochemical and immunoelectron microscopic studies with monoclonal antibodies against the adhesion molecules, CD54 (ICAM-1), CD 11a (LFA-1), CDw49a (VLA-1), CDw49b (VLA-2), CDw49c (VLA-3), Cdw49d (VLA-4) and CDw49e (VLA-5), were carried out to determine the pattern of distribution of these molecules at the rheumatoid synovial cartilage junction. Treatment with anti-ICAM-1 resulted in membrane staining of most of the macrophages and fibroblasts infiltrating the synovial tissue and bordering the pannus-cartilage junction, suggesting the possibility that ICAM-1 may function to facilitate the adhesion of synovial type A cells bearing ICAM-1 to type B cells of the pannus. ICAM-1-positive macrophages and fibroblasts were often found to be in contact with lymphoid cells, suggesting also that a cellular immune reaction occurs in the formation of the pannus. In addition, VLA-3, VLA-4 and, particularly, VLA-5 were the predominant1 integrins expressed by rheumatoid synovial pannus. Since these three integrins all function as fibronectin receptors, it is possible that the fibronectin-rich environment of the rheumatoid cartilage surface effectively traps pannus cells expressing high levels of these molecules. The VLA-5 molecule was found in a pericellular and interterritorial matrix distribution in the present study, strongly suggesting that a recepfor-ligand interaction between VLA-5 and cartilage matrix may occur at the early stage of pannus formation. Furthermore, an increase in1 integrin may be necessary for the growth of the pannus and also for the upregulation of the VLA molecules, leading secondarily to increased attachment.  相似文献   
134.
We report five patients with atypical parkinsonism characterized by freezing phenomenon, akinesia and axial rigidity without limb rigidity or tremor. These patients were selected from 252 patients with parkinsonism who were referred to our clinic from 1986 to 1993. They have common clinical features consisting of freezing phenomena involving all four extremities, especially in the initiation of walking, and marked axial rigidity; otherwise, neither supranuclear ophthalmoparesis nor nuchal dystonia was noted. Their clinical features did not change over several years except in one patient who later developed typical manifestations of progressive supranuclear palsy (PSP). Levodopa was of no effect on their symptoms. After excluding other possibilities, it is our conclusion that they represent an atypical form of PSP lying between the pure akinesia of Imai and Narabayashi and the typical form of PSP.  相似文献   
135.
Clinical study of growing up aneurysms: report of 25 cases   总被引:1,自引:0,他引:1  
Twenty-five cases of patients with growing up aneurysms are reported. Growth of the aneurysm was confirmed by repeated angiography within 1 month in 11 cases (short-term group), and for over 1 month in the other 14 cases (long-term group) following the initial angiography. Clinical history, shape and growth pattern of aneurysms, as well as hemodynamic factors that effect the growth were investigated in each group. The aneurysms were classified according to the shape into dome-type (smooth contour) and bleb-type (irregular contour). In all cases of the short-term group, the first angiography was performed because of rupture of the aneurysm. In this group, 4 cases bled again because of enlargement or the development of an aneurysmal bleb. Growth rate and the initial size of the aneurysm did not effect the potential of re-rupture. In the long-term group, 9 cases out of 14 (64.3%) had "non-ruptured aneurysm" at the time of first angiography. In the follow up, 5 cases were ruptured (two because of re-bleeding and three for the first time). In 3 out of these 5 cases, a bleb was demonstrated on initial angiography, and in another case, a bleb was demonstrated in follow-up angiography. Only one case ruptured because of the growth of the aneurysmal dome. Most of the aneurysms that rupture, in the follow-up survey, showed a larger growth rate in comparison with aneurysms that did not rupture. Many cases of this long-term group were associated with hypertension or vascular abnormalities which would effect the aneurysmal growth.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
136.
Itami C  Mizuno K  Kohno T  Nakamura S 《Brain research》2000,857(1-2):141-150
The maturation of cortical circuitry critically depends on experience. Recently, a model of silent synapse has been proposed as a mechanism of activity-mediated transition of immature synapse to mature synapse. It is not clear, however, how activity could regulate this transition. Here, we show the evidence that endogenous brain-derived neurotrophic factor (BDNF) is required for the maturation of glutamatergic synapse in developing mouse somatosensory cortex. Field potential recordings of thalamocortical glutamatergic synaptic activity with brain slices from the BDNF mutant mice showed that AMPA receptor responses are low, but NMDA receptor responses remain high in layer 4, thus, the relative contribution of AMPA receptor response is significantly lower compared to the age-matched wild-type mouse. Furthermore, optical images of development of thalamocortical connectivity with a voltage-sensitive dye showed that NMDA receptor-dominant synapse is established first in layer 4 and layer 5/6 then AMPA receptor response appears later in concomitant with reduction of NMDA receptor response in layer 4 and that the maturation of the silent synapse is impaired in the BDNF mutant mice. In layer 5/6, NMDA receptor response was suppressed without upregulation of AMPA receptor response. This process also required BDNF function. Interestingly, whisker-trimming of the wild-type mouse from just after birth showed quite similar results with the homozygous mutant of their whiskers left intact. Therefore, we would propose that BDNF is a critical mediator for the maturation of glutamatergic synapse in developing mouse somatosensory cortex.  相似文献   
137.
We report a patient with hemiparkinsonism associated with unilateral striatal necrosis of the contralateral side. The patient was an 18-year-old woman who had a two-month-history of difficulty in executing skilled movements with her right upper extremity. Neurological examination revealed that she had cogwheel rigidity and bradykinesia in her right upper and lower extremities. MRI revealed a well-delineated low signal intensity in T1-weighted and high signal intensity in T2-weighted images in the region of the putamen on the left side. Her laboratory data were unremarkable and mitochondrial gene mutation studies revealed no abnormality. It is extremely rare to encounter a case of parkinsonism associated with unilateral striatal necrosis.  相似文献   
138.
A new technique for dividing the fibula when performing a high tibial osteotomy is described. The head of the fibula is enucleated and morselized. The technique is simple and safe with a low complication rate.
Résumé En cas d’ostéotomie supérieure du tibia, nous décrivons une nouvelle technique d’ostéotomie péronière avec énucléation et morcellement de la tête du péroné. On peut employer pour ce faire la même incision cutanée que pour l’ostéotomie du tibia. L’incidence de complications est faible.


Accepted: 17 March 2000  相似文献   
139.
A patient presented 4 months after sustaining a fracture of the hook of hamate. X-rays and computed tomography scanning of the carpal tunnel confirmed the presence of an ununited fracture. Low-intensity ultrasound was applied to the fracture site. After 4.5 months of exposure to ultrasound, union was confirmed by both x-rays and computed tomography scanning of the carpal tunnel. (J Hand Surg 2000; 25A:77-79.  相似文献   
140.
A 71-year-old man was transferred to our institution with suspected of impending rupture of the abdominal aorta. The clinical manifestations included abdominal pain, pulsatile mass, and abdominal bruit. We made on early diagnosis of aortocaval fistula based on enhanced computed tomography and color Doppler flow imaging. Surgical repair was performed 24 hours after the onset of symptoms. At the introduction of anesthesia, cardiac arrest with high central venous pressure occurred. After resuscitation and rapid clamping of the proximal aorta, surgical closure of the fistula with graft replacement was performed successfully.  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