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   1704196篇
  免费   124424篇
  国内免费   3803篇
耳鼻咽喉   21835篇
儿科学   55877篇
妇产科学   46343篇
基础医学   242555篇
口腔科学   48942篇
临床医学   152176篇
内科学   335194篇
皮肤病学   38739篇
神经病学   131787篇
特种医学   64183篇
外国民族医学   244篇
外科学   258650篇
综合类   39117篇
现状与发展   4篇
一般理论   551篇
预防医学   125125篇
眼科学   40490篇
药学   124203篇
  7篇
中国医学   4484篇
肿瘤学   101917篇
  2021年   12927篇
  2019年   13632篇
  2018年   20112篇
  2017年   15322篇
  2016年   16730篇
  2015年   19103篇
  2014年   26426篇
  2013年   38276篇
  2012年   53166篇
  2011年   55888篇
  2010年   33091篇
  2009年   31004篇
  2008年   51979篇
  2007年   55310篇
  2006年   55722篇
  2005年   53069篇
  2004年   51229篇
  2003年   48572篇
  2002年   46825篇
  2001年   91978篇
  2000年   93805篇
  1999年   77124篇
  1998年   19841篇
  1997年   17362篇
  1996年   17465篇
  1995年   16829篇
  1994年   15368篇
  1993年   14149篇
  1992年   57524篇
  1991年   55380篇
  1990年   53087篇
  1989年   50871篇
  1988年   46228篇
  1987年   45050篇
  1986年   42319篇
  1985年   40088篇
  1984年   29436篇
  1983年   25011篇
  1982年   13971篇
  1979年   25616篇
  1978年   17656篇
  1977年   14958篇
  1976年   13938篇
  1975年   14624篇
  1974年   17695篇
  1973年   17001篇
  1972年   15721篇
  1971年   14493篇
  1970年   13480篇
  1969年   12554篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The authors report a case of massive Trichuris trichiura infection, resulting in severe anaemia and congestive cardiac failure in a 9-year-old Iban boy, who was resistant to the usual oral anthelmintic treatment, but promptly responded to mebendazole retention enema. This patient also had an associated Entamoeba histolytica infection.  相似文献   
992.
993.
994.
The present studies were undertaken to determine the involvement of neurons in the hypothalamic paraventricular nucleus (PVN) in stress-induced renin secretion. The stressor was a 10-min conditioned emotional response (CER) paradigm. Bilateral electrolytic lesions in the PVN prevented the stress-induced increase in plasma renin activity (PRA), and plasma renin concentration (PRC). Stress-induced corticosterone secretion was also blocked, supporting the histological verification and suggesting that the lesion included corticosterone-releasing factor neurons in the PVN. Stress-induced renin secretion appears to be restricted to the PVN, as electrolytic lesions in the nucleus reuniens, dorsal and caudal to the PVN, did not prevent the stress-induced increase in either PRA or PRC. The next step was to determine whether cell bodies in the PVN or fibers of passage through the PVN mediate the stress-induced increase of these hormones. For this purpose, bilateral stereotaxic injections of the cell-selective neurotoxin ibotenic acid (10 micrograms/microliter; 0.3 microliters per side) were performed 14 days prior to the stress procedure. Histological evaluation of the tissue revealed cell death and lysis in the PVN. Ibotenic acid injection into the PVN prevented the effect of stress on PRA, PRC and corticosterone levels. None of the lesions prevented the stress-induced rise in plasma prolactin concentration. These results suggest that neurons in the PVN play an important role in mediating stress-induced increases in renin and corticosterone but not prolactin secretion.  相似文献   
995.
A bovine beta-1,4-galactosyltransferase (GT; EC 2.4.1.90) cDNA in an Okayama-Berg vector, pLsGT, was constructed from a partial cDNA clone and a genomic fragment. We report that the cDNA sequence of pLsGT, in a transient expression assay in COS-7 cells, codes for an enzymatically active GT protein. There is an approximately 12-fold increase in the GT activity in pLsGT-transfected cells compared to cells transfected with the antisense bovine GT construct, pLasGT, or pSV2Neo or mock-transfected cells. The increased activity is correlated with the increase in bovine GT mRNA, which is distinguishable from COS GT mRNA with a 3'-end-specific probe of pLsGT. The expressed GT activity is modulated by alpha-lactalbumin, which changes the acceptor specificity to glucose to synthesize lactose. Polyclonal antibody raised against SDS/PAGE-purified bovine milk GT and a monoclonal antibody (mAb 4-10) directed against a synthetic peptide corresponding to the amino-terminal region of the protein encoded by pLsGT bind the expressed protein, and the resulting immunoprecipitates exhibit GT enzymatic activity.  相似文献   
996.
In the search for HLA-linked immune response genes that control susceptibility to tuberculosis, we performed HLA typing and measured antibody titers to well-defined Mycobacterium tuberculosis antigenic determinants in 101 patients with sputum smear-positive pulmonary tuberculosis and 64 healthy controls from Surabaya, Indonesia. HLA-DR2 and DQw1 were associated with sputum smear-positive pulmonary tuberculosis (attributable risk = 36% and 39%, respectively), while DQw3 was associated even more strongly with the control group (preventive fraction = 57%). Antibody titers to the TB71 and TB72 epitopes of the 38-kDa protein, present only on tubercle bacilli, were strongly associated with DR2 (Pcorr = .001 and .024, respectively). The association of both the disease and the antibody response to the 38-kDa antigen of M. tuberculosis with Class II HLA genes HLA-DR2 indicates that Ir-gene-mediated regulation of the immune response to this antigen may be of pathogenic significance for the development of sputum smear-positive tuberculosis.  相似文献   
997.
The use of multifactor statistic analysis for screening population of the northern part of the Ob river basin for helminthiasis allowed the authors to reveal a significant feedback between manifested opisthorchiasis and other types of this disease course in both sexes. The main component analysis indicates that the tentatively control group of males is presented by adolescents (14-17 years old) who are likely to be infected with Opisthorchis without evidence of its clinical manifestations. The correlation analysis demonstrated also a direct relationship between the age and manifest opisthorchiasis, as well as double mixed invasion of males (r-0.15 and 0.26, p less than 0.05 and 0.01, respectively). The first three main components explain about 55% variance in the correlation matrix of initial parameters and allow to reveal the variance source, taking into account, along with differentiation of 4 groups of opisthorchiasis patients, also the age- and sex-dependent combination of opisthorchiasis with other helminthic invasions.  相似文献   
998.
Despite extensive investigation, the pathogenesis of the adult respiratory distress syndrome (ARDS) remains uncertain. As yet, there is no clear explanation of why some patients at risk for ARDS develop the syndrome, whereas others do not. Neutrophils and complement fragments have been implicated in the acute lung injury, but it is clear from published data that evidence of complement activation alone predicts neither the development nor the severity of ARDS. We investigated whether the combination of endotoxin, a leukocyte-priming agent, and complement fragments, leukocyte-stimulating agents, was associated with the development of ARDS. Ninety-eight patients were identified as being either at risk for the development of ARDS or having ARDS, and serial blood samples were obtained. There was no correlation between C5 fragments and the development of ARDS. C3 fragment levels were increased in 89% of the patients with ARDS, but they were also increased in 62% of patients at risk. Endotoxin was detected in 74% of the plasma samples obtained from patients at risk who subsequent developed ARDS and in 64% of the plasma samples obtained from the patients with ARDS. In contrast, only 22% of the plasma samples obtained from the patients at risk who did not develop ARDS had measurable endotoxin. We suggest that the combination of endotoxin and complement fragments may be one mechanism involved in the development of ARDS.  相似文献   
999.
S C Chang  G M Shiao  R P Perng 《Chest》1989,96(1):60-63
The effect of body position (right and left lateral decubitus positions) on arterial oxygen tension (PaO2) and the relationship between this postural effect on gas exchange and pulmonary function were evaluated in 21 patients who had unilateral pleural effusions without roentgenographic and bronchoscopic evidence of bronchopulmonary disorders. Our results indicated that a positional influence on gas exchange existed in these patients. We failed to find a consistent relationship between the size of effusion estimated by chest roentgenogram and alterations in PaO2 during different positions. Postural change did affect gas exchange in the patients with unilateral pleural effusions and this postural effect on gas exchange was highly correlated with their FEV1 and FVC. This may be of clinical significance in managing such patients.  相似文献   
1000.
To determine the value of chest roentgenograms in the management of asymptomatic persons with positive tuberculin skin test results, we undertook a retrospective review of all tests administered by our Employee Health Service, North Shore University Hospital, Manhasset, NY, between July 1, 1983 and November 1, 1987. Of 5200 tests, 247 results were positive. Two hundred twenty-one of these charts were reviewed for roentgenographic results and the presence of symptoms. All persons were asymptomatic. Chest roentgenograms revealed the following: normal, 188; unrelated abnormalities, 24; apical pleural thickening, 5; granulomas, 2; calcified hilar node, 1; and calcified node plus granuloma, 1. We noted no active tuberculosis, nor did the chest roentgenographic results influence recommendations for isoniazid prophylaxis. We conclude that chest roentgenograms are of value in 0% to 1.3% of asymptomatic people with positive tuberculin test results. A larger study should be undertaken to further define the usefulness of chest roentgenograms in this population.  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