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   1015400篇
  免费   71878篇
  国内免费   1698篇
耳鼻咽喉   14556篇
儿科学   26957篇
妇产科学   25279篇
基础医学   143848篇
口腔科学   31855篇
临床医学   86417篇
内科学   203616篇
皮肤病学   21875篇
神经病学   78913篇
特种医学   38589篇
外国民族医学   80篇
外科学   162204篇
综合类   18583篇
现状与发展   1篇
一般理论   263篇
预防医学   70697篇
眼科学   22833篇
药学   78533篇
  3篇
中国医学   2705篇
肿瘤学   61169篇
  2021年   8573篇
  2019年   8594篇
  2018年   12277篇
  2017年   9010篇
  2016年   9713篇
  2015年   11097篇
  2014年   15148篇
  2013年   21816篇
  2012年   30476篇
  2011年   31895篇
  2010年   18477篇
  2009年   17261篇
  2008年   29578篇
  2007年   30870篇
  2006年   31220篇
  2005年   30136篇
  2004年   28781篇
  2003年   27525篇
  2002年   26699篇
  2001年   56483篇
  2000年   58459篇
  1999年   48519篇
  1998年   11234篇
  1997年   9883篇
  1996年   9908篇
  1995年   9225篇
  1994年   8524篇
  1993年   7787篇
  1992年   36150篇
  1991年   34432篇
  1990年   33215篇
  1989年   32256篇
  1988年   29359篇
  1987年   28586篇
  1986年   26591篇
  1985年   25418篇
  1984年   18018篇
  1983年   15322篇
  1982年   7923篇
  1979年   15938篇
  1978年   10720篇
  1977年   9120篇
  1976年   7948篇
  1975年   8713篇
  1974年   10616篇
  1973年   9959篇
  1972年   9447篇
  1971年   8969篇
  1970年   8526篇
  1969年   8035篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
921.
BACKGROUND: Allergen-specific immunotherapy is the only treatment for allergic disease providing long-lasting symptom relief. Currently, it is mainly based on the use of crude allergen extracts. The treatment may be improved by the use of genetically engineered allergens, hypoallergens, aiming at a more effective and safer therapy. OBJECTIVE: The aim of this study was to provide a rational design of hypoallergen candidates for immunotherapy by using structural information and knowledge of B and T cell epitopes of an allergen. METHODS: The three-dimensional structure of the major cat allergen Fel d 1 was systematically altered by duplication of selected T cell epitopes and disruption of disulphide bonds. Seven Fel d 1 derivatives were generated and screened for allergenic reactivity in comparison with recombinant Fel d 1 in competition-ELISA. The allergenicity was further evaluated in basophil activation experiments and T cell reactivity was assessed in a lymphoproliferation assay. RESULTS: Three out of seven Fel d 1 derivatives, with two duplicated T cell epitopes and one or two disulphide bonds disrupted, were carefully evaluated. The three derivatives displayed a strong reduction in allergenicity with 400-900 times lower IgE-binding capacity than recombinant Fel d 1. In addition, they induced a lower degree of basophil activation and similar or stronger T cell proliferation than recombinant Fel d 1. CONCLUSION: By a rational approach, we have constructed three Fel d 1 hypoallergens with reduced IgE-binding capacities and retained T cell reactivities. This strategy may be applied to any well-characterized allergen to improve immunotherapy for allergic patients.  相似文献   
922.
OBJECTIVE: The aim of the study was to describe the occurrence of spontaneous version in twins in the third trimester, as well as the correlation between antepartum and birth presentation. METHODS: Twin pregnancies were divided into four gestational age intervals: 20-23; 24-27; 28-31; and 32-36 weeks. Fetal presentation was categorized as cephalic (C) or non-cephalic (NC). Hospital records were reviewed to determine demographic factors, including mode of conception. Chi-square was used to compare distributions of presentations, and Cramer's V measure of association was used to correlate presentations in individual pregnancies between antepartum intervals and birth. RESULTS: A total of 207 pregnancies were included. The distribution of fetal presentations changed significantly through gestational age intervals (p < 0.001), although they were similar between 32-36 weeks and birth (p = 0.75). Correlation between antepartum and birth presentation in individual pregnancies strengthened throughout the four intervals. No correlation was seen between parity, gender, birthweight, or in vitro fertilization and fetal presentation or rate of spontaneous version.CONCLUSION: Many twins undergo spontaneous version in the third trimester, though there is excellent correlation between presentation at 32-36 weeks and birth. A cephalic presenting twin at > or = 28 weeks is highly likely to be in cephalic presentation at delivery.  相似文献   
923.
Higher cerebral dysfunctions such as aphasia, apraxia and agnosia have seldom been reported in multiple sclerosis (MS). 12 year-old right-handed boy felt unsteadiness of the body and headache for several days. Two months later, he had the same episode and complained of visual disturbance, and weakness and sensory disturbance on the face and the extremities. Additionally, he showed amnestic aphasia, acalculia, ideomotor apraxia, finger agnosia and right-left disorientation. Cerebrospinal fluid examinations revealed increases IgG, myelin basic protein and neuron specific enolase (11%, 25 ng/ml and 28.8 ng/ml, respectively). X-ray CT scan and MRI-CT examinations revealed sclerotic lesions on the left parietal white matter and the right mid-brain. The diagnosis was made as MS. He was treated with m-PSL (methyl-prednisolone) pulse therapy for three weeks and consecutively treated with PSL for four weeks. He recovered gradually, but visual disturbance and facial palsy remained. After seven months MRI-CT showed a high signal intensity on the left parietal white matter in spite of the disappearance of the lesion on X-ray CT scan. We suggest that these higher cerebral dysfunctions may result from the lesion of the left parietal white matter which produces a disconnection between each cortical area.  相似文献   
924.
Crisis debriefing of a jury after a murder trial   总被引:1,自引:0,他引:1  
The importance of crisis debriefing for those involved in major accidents, violent crimes, and natural disasters has been demonstrated. Similar debriefing may be warranted for jurors exposed to disturbing material in criminal cases. The authors describe a debriefing session for jurors after the murder trial of a man whose truck had collided with a school bus, killing 27 people. The graphic evidence of the accident, the high levels of emotion of the survivors and the victims' relatives, and the intense community and national attention to the trial placed the jurors under considerable stress. The debriefing enabled the jurors to express their feelings of anger, guilt, and frustration and to begin to accept their role in the event.  相似文献   
925.
In view of the continuing debate on euthanasia, the restrictions and safeguards which were introduced into the Voluntary Euthanasia (Legislation) Bill 1936 are discussed. Proposals for a new Terminal Care and Euthanasia Bill are suggested, based on some of the principles of the Mental Health Act 1983.  相似文献   
926.
A seven-month-old girl with atypical West syndrome with pedaling automatism was reported. She started to have early infantile epileptic encephalopathy with suppression-burst (EIEE) at age 14 days followed by infantile spasms at 3 months of age. She began to have spasms with automatism at 4 month, mainly consisting of pedaling movements of both feet associated with tonic spasms of upper extremities and writhing of trunk. Ictal EEG showed irregular slow waves with occasional spikes predominantly over the right hemisphere mixed with artifacts. Interictal EEG during sleep showed suppression-burst patterns. Cerebral atrophy and microcephaly were revealed on brain CT, immature myelination on MRI and decreased blood flow in the frontal, temporal, and parietal lobes on the right on PET scan. Pedaling automatism is rare in infancy and its clinical significance was discussed in relation to West syndrome and complex partial seizures.  相似文献   
927.
Pattern visual evoked potentials were obtained from 46 patients with definite relapsing/remitting multiple sclerosis, using both a conventional 5-channel occipital array and a 3-D recording technique consisting of three bipolar derivations approximating the three dimensions of space. These three orthogonal wave forms were displayed as a 3-D Lissajous trajectory for each subject. Two of the 15 patients with completely normal conventional pattern VEPs had abnormalities of the orientation of the B-C curvilinear segment of the 3-D pattern VEPs. Delays in the first major occipital positive component (P100) were evident using both techniques; the correlation between P100 latency and the latency of the corresponding trajectory apex was r = 0.99 (P less than 0.01). Post-chiasmal MRI abnormalities were associated with 3-D VEP orientation abnormalities. Three-dimensional pattern VEPs are moderately more sensitive than conventional pattern VEPs at detecting dysfunction posterior to the optic chiasm in demyelinating disease and do not require the use of eccentric fixation to do so.  相似文献   
928.
Pulse cyclophosphamide for severe neuropsychiatric lupus.   总被引:5,自引:0,他引:5  
We studied the effect of parenteral pulse cyclophosphamide therapy in nine patients with active systemic lupus erythematosus and severe central nervous system involvement. Seven patients had focal neurological deficits and/or seizures associated with abnormalities on cerebrospinal fluid analysis and/or magnetic resonance imaging. Two patients had organic brain syndrome with psychosis and normal cerebrospinal fluid and/or magnetic resonance imaging analysis. Six patients were unresponsive to treatment with high dose corticosteroid. Cyclophosphamide, 0.75-1.0 g/m2 body surface area, was administered intravenously every month for at least 2 months. Eight patients had a complete recovery or recovered with minor residuals. Cyclophosphamide was well tolerated with few side effects. We conclude that parenteral pulse cyclophosphamide is an effective adjunctive therapy for the management of patients with active systemic lupus erythematosus and central nervous system symptoms.  相似文献   
929.
930.
Following an encephalopathic illness, a 13-year-old Chinese boy had a partial form of Klüver-Bucy syndrome with emotional disturbance, recent memory loss, hypersexuality, and polyphagia. Other unusual features included narcolepsy, polydipsia, and polyuria. Virologic studies failed to incriminate the etiologic agent, including herpes simplex virus. Brain biopsy of the frontal lobe demonstrated Alzheimer type II astrocytosis.  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