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   57999篇
  免费   6219篇
  国内免费   127篇
耳鼻咽喉   400篇
儿科学   2002篇
妇产科学   1614篇
基础医学   8253篇
口腔科学   1065篇
临床医学   7571篇
内科学   11285篇
皮肤病学   1117篇
神经病学   5502篇
特种医学   1956篇
外国民族医学   7篇
外科学   6727篇
综合类   960篇
一般理论   48篇
预防医学   6597篇
眼科学   1174篇
药学   4139篇
中国医学   63篇
肿瘤学   3865篇
  2023年   388篇
  2022年   527篇
  2021年   1362篇
  2020年   930篇
  2019年   1487篇
  2018年   1600篇
  2017年   1244篇
  2016年   1347篇
  2015年   1423篇
  2014年   1822篇
  2013年   2574篇
  2012年   3464篇
  2011年   3342篇
  2010年   2052篇
  2009年   1831篇
  2008年   2942篇
  2007年   3013篇
  2006年   2897篇
  2005年   2743篇
  2004年   2632篇
  2003年   2414篇
  2002年   2265篇
  2001年   1401篇
  2000年   1397篇
  1999年   1239篇
  1998年   658篇
  1997年   563篇
  1996年   500篇
  1995年   445篇
  1994年   456篇
  1993年   426篇
  1992年   895篇
  1991年   869篇
  1990年   854篇
  1989年   741篇
  1988年   755篇
  1987年   694篇
  1986年   659篇
  1985年   713篇
  1984年   595篇
  1983年   478篇
  1982年   333篇
  1981年   349篇
  1980年   294篇
  1979年   490篇
  1978年   378篇
  1977年   298篇
  1976年   320篇
  1974年   323篇
  1972年   292篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
41.
Blood and plasma donations among a cohort of intravenous drug users   总被引:1,自引:0,他引:1  
K E Nelson  D Vlahov  J Margolick  M Bernal  E Taylor 《JAMA》1990,263(16):2194-2197
We evaluated the blood and plasma donation histories of a cohort of 2921 intravenous drug users in Baltimore, Md, and correlated these histories with their human immunodeficiency virus (HIV) serologic status, numbers of CD4 lymphocytes in the peripheral blood, and stigmata of intravenous drug use (scarred veins). Of the 793 intravenous drug users (27.1%) who had donated blood or plasma, 652 (82.2%) donated after they had started using intravenous drugs. Most subjects donated at commercial plasma centers, where they were paid $10 to $15 per donation. Although the HIV-1 seroprevalence of the entire cohort was 24.1%, the HIV-1 seroprevalence among those reporting plasma or blood donations declined progressively with time, from 17.1% in those who last donated in 1985 to 3.6% in those who last donated in 1988-1989. Many of the 437 intravenous drug users who had donated plasma or blood since 1985, when screening for HIV-1 was initiated, had not been notified and counseled about their HIV test results. Current programs to exclude individuals with a history of intravenous drug use from the plasma donor pool should be reevaluated and improved.  相似文献   
42.
Summary Twenty-two patients with recurrent or metastatic squamous cell carcinoma of the head and neck were treated with piroxantrone 150 mg/m2 intravenously every 21 days. There were no objective responses. The 95% upper confidence bound for response is 15%. Primary toxicity was hematologic.  相似文献   
43.
The ability of a number of heterocyclic metal chelators to deliver zinc into red cells, to release the liganded zinc to haemoglobin and thereby cause a left shift in the oxygen dissociation curve of intact red cells has been investigated. Incubation of neutrally charged zinc-pyrone and zinc-pyridin-2-one complexes with red cells led to the rapid accumulation of zinc within cells, whereas unliganded zinc in the form of zinc acetate, zinc chloride or zinc sulphate accumulated only slowly. The rate at which zinc was delivered to red cells by pyrone and pyridin-2-one ligands increased with increasing lipid solubility of the ligands. The uptake of zinc into both normal adult and sickle red cells was associated with a dose-dependent increase in the oxygen affinity of haemoglobin. The degree of left shift in the oxygen dissociation curve following the incubation of red cells with zinc-pyrone and -pyridin-2-one complexes suggests that these complexes may find application as agents to increase the oxygen affinity of haemoglobin in sickle cell disease and thereby decrease the probability of intravascular sickling at low tissue oxygen tensions. Ethylmaltol appears to be a particularly useful agent due to its known low toxicity.  相似文献   
44.
45.
The spectrum of acne vulgaris is wide, ranging from minor comedones to devastating nodules and cysts. Appropriate therapy requires an understanding of the various types of lesions, their pathophysiology, and the rationale for treatment. Good patient rapport and communication are important, and close follow-up is necessary until the treatment regimen has stabilized. Timely referral to a dermatologist is essential when therapy is not effective. With effort, the treatment of acne can be quite rewarding for both patient and physician.  相似文献   
46.
47.
32nd Annual Meeting of the Scandinavian Society for Psychopharmacology Copenhagen, Denmark April 10–12, 1991 Abstracts  相似文献   
48.
A R Berry  G C Davies  A M Millar  T V Taylor 《Gut》1983,24(10):929-934
Using an experimental model of acute pancreatitis in the rat, we have studied changes in the biophysical properties of lungs and intrapulmonary fibrin deposition in this condition. Acute pancreatitis is associated with a significant decrease in pulmonary compliance (p less than 0.01) and a significant increase in lung weight (p less than 0.01) compared with a control sham operation group. These changes are associated with a 24% increase in intrapulmonary 125I fibrinogen deposition (p less than 0.01), and an 18% increase in 125I fibrinogen deposition per gram of lung tissue (p less than 0.05) in acute pancreatitis, compared with a control sham operation group. The increased fibrinogen deposition is abolished by treatment with low dose heparin. Using the same animal model changes in pulmonary ultrastructure are shown using scanning electron microscopy. The results indicate that pulmonary abnormalities are associated with intrapulmonary fibrin deposition in experimental acute pancreatitis and these findings may be relevant to the well described respiratory complications of the condition in man.  相似文献   
49.
50.
Summary Aged common marmosets were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 0.5–2.0 mg/kg/week i.p.) for 16 or 24 weeks, observed for a total of 30 weeks and then killed for measurement of biochemical pramaters in basal ganglia. The MPTP treatment induced a marked depletion in dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels in the caudate nucleus and putamen. In contrast, the concentrations of five neuropeptides: [Met5]-enkephalin, [Leu5]-enkephalin, cholecystokinin, substance P and neurotensin as measured by a combined HPLC/RIA method, remained unaltered in all basal ganglia regions examined. Enkephalin precursor levels, as reflected by cryptic [Met5]-enkephalin content, were increased in the putamen, but not in the caudate nucleus, as a consequence of MPTP administration. Cryptic [Leu5]-enkephalin content remained unchanged in the striatum of MPTP treated marmosets. Overall, these results suggest an increase in striatal [Met5]-enkephalin release following chronic MPTP treatment of aged marmosets. However, the chronic treatment of aged marmosets with MPTP does not reproduce the neuropeptide alterations characteristic of Parkinson's disease.  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