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   6361篇
  免费   350篇
  国内免费   73篇
耳鼻咽喉   18篇
儿科学   112篇
妇产科学   169篇
基础医学   793篇
口腔科学   121篇
临床医学   430篇
内科学   1646篇
皮肤病学   180篇
神经病学   394篇
特种医学   256篇
外科学   1183篇
综合类   20篇
预防医学   133篇
眼科学   137篇
药学   468篇
中国医学   7篇
肿瘤学   717篇
  2023年   44篇
  2022年   82篇
  2021年   110篇
  2020年   86篇
  2019年   106篇
  2018年   137篇
  2017年   148篇
  2016年   167篇
  2015年   132篇
  2014年   181篇
  2013年   227篇
  2012年   281篇
  2011年   347篇
  2010年   161篇
  2009年   152篇
  2008年   297篇
  2007年   357篇
  2006年   315篇
  2005年   348篇
  2004年   335篇
  2003年   316篇
  2002年   351篇
  2001年   204篇
  2000年   208篇
  1999年   183篇
  1998年   95篇
  1997年   51篇
  1996年   70篇
  1995年   61篇
  1994年   47篇
  1993年   43篇
  1992年   114篇
  1991年   110篇
  1990年   100篇
  1989年   137篇
  1988年   91篇
  1987年   86篇
  1986年   65篇
  1985年   63篇
  1984年   44篇
  1983年   36篇
  1980年   19篇
  1979年   25篇
  1978年   31篇
  1977年   20篇
  1975年   18篇
  1973年   17篇
  1970年   20篇
  1969年   15篇
  1966年   15篇
排序方式: 共有6784条查询结果,搜索用时 15 毫秒
51.
Summary Bromocriptine and lergotrile, which are clinically used as antiparkinsonian (AP) agents, compete for the binding of H3-dopamine, H3-apomorphine, and H3-haloperidol to striatal membrane sites. Lergotrile has a higher affinity for the H3-dopamine binding to bovine striatal membranes than bromocriptine. Lergotrile and bromocriptine are almost equipotent in competing for the binding of H3-apomorphine to rat striatal membranes, but bromocriptine is more potent in competing for the binding of H3-haloperidol than lergotrile. These results indicate that lergotrile and bromocriptine are mixed putative agonist-antagonist with respect to the postsynaptic dopamine receptors. Lergotrile and bromcriptine at higher concentrations inhibit synaptosomal tyrosine hydroxylase activity, and reverse the apomorphine elicited enzyme inhibition. Thus, these ergot alkaloids behave as mixed agonist-antagonist also with respect to the presynaptic dopamine receptors. Bromocriptine and lergotrile, as well as other tested DH-ergot alkaloids and neuroleptics, compete for the binding of the-antagonist H3-WB-4101 to rat cerebral cortical membranes. The displacing potencies of the tested DH-ergot alkaloids and of the neuroleptics indicate that they have a high affinity for the-adrenoreceptors in the CNS.  相似文献   
52.
Key words  complications - intubation - epiglottic cyst  相似文献   
53.
We reported previously that an angiogenesis inhibitor, E7820, inhibits in vitro tube formation of human umbilical vein endothelial cell through the suppression of integrin alpha2 expression. Here we describe the antiangiogenic and antitumor effects of E7820 in mice and discuss the feasibility of using platelet integrin alpha2 expression on platelets as a biological marker of the efficacy of E7820. Oral administration of E7820 significantly inhibited basic fibroblast growth factor-induced angiogenesis in Matrigel implants and human colon WiDr tumor-induced angiogenesis in a dorsal air sac model. Twice-daily treatment with E7820 clearly inhibited the s.c. tumor growth of seven tumor cell lines derived from human colon, breast, pancreas, and kidney, and completely suppressed the growth of human pancreatic KP-1 and human colon LoVo cell lines. Moreover, E7820 significantly inhibited the growth of KP-1 and human colon tumor Colo320DM cells orthotopically implanted in the pancreas and cecum, respectively. The efficacy of E7820 was comparable in the s.c. and orthotopic transplantation models. Immunohistochemical analyses using anti-CD31 antibody showed that E7820 significantly reduced microvessel density in orthotopically implanted KP-1 tumor. E7820 reduced integrin alpha2 expression on a megakaryocytic cell line, Dami cells, induced by phorbol 12-myristate 13-acetate treatment. It also decreased the expression level of integrin alpha2 on platelets withdrawn from mice bearing s.c. KP-1 tumor at a dosage close to that affording antitumor activity. These data demonstrate that E7820 showed a broad-spectrum antitumor effect in mice through inhibition of angiogenesis and indicate that the decrease of integrin alpha2 on platelets might serve as a biological marker for the antitumor efficacy of E7820.  相似文献   
54.
The expression of alternatively spliced mRNAs for amyloid precursor protein (APP) isoforms and their translation products were examined in the rat cerebral cortex 1, 3, 6, and 12 h and 1, 3, and 7 days (n = 4-5 in each group) after fluid-percussion brain injury. In situ hybridization studies demonstrated that the expression of APP695 mRNA decreased in and around the damaged area of the cerebral cortex exposed to fluid-percussion injury 1 h after the insult. On the other hand, APP751/770 mRNAs were increased in the regions surrounding the damaged cortical areas 1 day after the injury. An increase of immunoreactive APP was detected in the regions around the damaged cortical areas 3 h after traumatic injury and maintained for the following 3 days. The APP immunoreactivity in the damaged cortices declined to the level of sham-operated animals by post-experimental day 7. Using an anti-amyloid beta (Abeta) protein (17-24) antibody, no deposits of immunoreactive Abeta (17-24) were observed in any of the samples examined in these experiments. These results suggest that the induction of Kunitz-type protease inhibitor (KPI) domain-containing APP mRNAs and the increased accumulation of APP are involved in the physiological and neuropathological responses of brains under various neurodegenerative conditions, including head trauma.  相似文献   
55.
A patient, who was not suited for ultrasound-guided biopsy, was biopsied in an interventional magnetic resonance unit at Brigham and Women's Hospital. Real-time magnetic resonance imaging provided verification of placement before tissue samples were taken. This technique successfully sampled tissue from the prostate and led to a diagnosis of cancer.  相似文献   
56.
A case of penetrating lung and diaphragmatic injuries with no abnormal findings of chest X-ray is reported. A 76-year-old man was admitted to our hospital due to penetrating chest trauma. A simple X-ray film of the chest on admission revealed no abnormal finding. An emergency operation was performed. On exploring the back open wound, we found a laceration of 7 cm in diameter in the right diaphragm and lung laceration. Then we repaired primarily with absorbable material. The postoperative course was uneventful, and the patient was discharged 12 days later. Penetrating truncal traumas can result in diaphragmatic injury. Sometimes the clinical and roentgenographic findings are unreliable. If the diagnosis is missed, a diaphragmatic injury may occur delayed diaphragmatic hernias within hours to years. Accordingly, initial wound exploration are important for the diagnosis of diaphragmatic injury in avoiding serious complications.  相似文献   
57.
OBJECTIVES: Ex vivo perfusion of the cardiac allograft during organ procurement is an ideal environment for adenoviral vectors with transgenes that target improving graft contractility. One such target is the beta-adrenergic receptor-signaling system, in which alterations in transgenic mice have elucidated novel means to improve the function of the heart in vivo. The purpose of the current study was to determine the functional consequences of beta-adrenergic receptor manipulation in a rabbit model of cardiac allograft transplantation. METHODS: New Zealand White rabbits weighing 3 kg served as recipients to 1-kg outbred donors. Donor hearts were arrested and harvested, and 1 of 3 adenoviral constructs was administered into the aortic root perfusing the graft. Transgenes delivered encoded either the human beta(2)-adrenergic receptor, a peptide inhibitor of beta-adrenergic receptor densensitization, or the marker transgene beta-galactosidase. RESULTS: Five days after cervical heterotopic transplantation, left ventricular performance was measured on a Langendorff apparatus. A moderate pattern of rejection was seen in all grafts. Biventricular myocyte expression of beta-galactosidase was observed, and beta(2)-adrenergic receptor density was elevated 10-fold in grafts that received adeno-beta(2)-adrenergic receptor. Left ventricular systolic and diastolic performance was significantly increased in grafts transfected with either adeno-beta(2)-adrenergic receptor or adeno-beta-adrenergic receptor densensitization compared with control grafts that received adeno-beta-galactosidase. CONCLUSIONS: Ex vivo adenovirus-mediated gene transfer is feasible in a rabbit allograft model and, more important, genetic manipulation of beta-adrenergic receptor signaling either by increasing beta(2)-adrenergic receptor density or blocking endogenous receptor desensitization improves graft function acutely in this allograft model.  相似文献   
58.
Social skill deficits in schizophrenia profoundly affect patients' life-long outcome, although the profile of the underlying cognitive dysfunction still remains a matter of debate. In the present study, we investigated the relationship between social skills and event-related potentials (ERPs) in an auditory selective attention task, in addition to the neurocognitive indices obtained from the degraded-stimulus continuous performance test (CPT) and clinical indices, such as Brief Psychiatric Rating Scale (BRPS) and global assessment of function (GAF) scores. Social skills were assessed using a Japanese version of the structured role play test. Fourteen persons with schizophrenia participated in the study. Non-verbal skills showed a positive correlation with GAF, the performance level, N1 and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Verbal communication skills showed a positive correlation with GAF, the performance level and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Processing skills showed a positive correlation with the performance level and N1 amplitude in the ERP task and a negative correlation with reaction time in the CPT. These findings suggested that the social skill deficits of persons with schizophrenia were related to the vigilance level and controlled stimulus detection processing.  相似文献   
59.
To elucidate the mechanism of neuronal death in Alzheimer's disease, we investigated the effects of overexpression of wild-type Alzheimer amyloid precursor protein (APP) on neuronal cells and glial cells in vivo. When an APP695-expressing adenovirus was injected into the dorsal hippocampal region, a number of neurons in remote areas were positively stained with anti-APP monoclonal antibody, and underwent severe degeneration from 3 to 7 days after viral inoculation. Most degenerating neurons were immunopositive with both APP and activated caspase-3, but some neurons that expressed activated caspase-3 were not expressing APP from 7 to 14 days after virus injection. In the neighborhood of the degenerating neurons, activated microglia/macrophages, which were identified by the phenotypic marker C3bi receptor (CD11b/c; OX-42), were observed, and some of them appeared to phagocytose the caspase-3-immunopositive degenerating neurons. In addition to microglia/macrophages, infiltrating leukocytes expressing CD45 or CD4 were also detected. These results suggest that the increased accumulation of APP induced not only caspase-3-mediated death machinery, but also inflammatory responses including microglial activation. These inflammatory responses might cause further neurodegeneration through the alternative pathway that might activate the caspase-3-mediated death machinery without APP expression.  相似文献   
60.
OBJECTIVE: To evaluate the characteristic patterns of facial expression in fetuses aged from 28 to 34 weeks using 4-dimensional (4-D) ultrasonography. METHODS: The faces of 10 healthy fetuses aged from 28 to 34 weeks were recorded continuously for 15 min with a 4-D ultrasonographic machine performing up to 25 frames per second. The occurrence rates of blinking, mouthing, yawning, tongue expulsion, smiling, scowling, and sucking were evaluated. RESULTS: Mouthing was the most frequent facial expression (median, 6.5; range, 2-19) whereas the least frequent were scowling (median, 1; range, 0-9) and sucking (median, 1; range, 0-2). Mouthing was evident in all fetuses and significantly more frequent than any other movement (P<.05). Yawning (median, 3; range, 0-6), smiling (median, 2; range, 0-9), and blinking (median, 1.5; range, 0-6) were observed in most cases. Tongue expulsion (median, 1.5; range, 0-5), scowling, and sucking were each observed in 6 cases. CONCLUSION: 4-D sonography provides a means of evaluating fetal facial expression early in the third trimester. It may be a key to predicting fetal brain function and well-being and an important modality in future fetal neurophysiologic research.  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