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   1776篇
  免费   233篇
  国内免费   17篇
耳鼻咽喉   18篇
儿科学   88篇
妇产科学   27篇
基础医学   140篇
口腔科学   12篇
临床医学   253篇
内科学   336篇
皮肤病学   31篇
神经病学   137篇
特种医学   165篇
外科学   369篇
综合类   67篇
现状与发展   20篇
一般理论   5篇
预防医学   123篇
眼科学   29篇
药学   66篇
中国医学   4篇
肿瘤学   136篇
  2023年   42篇
  2021年   21篇
  2020年   27篇
  2019年   16篇
  2018年   61篇
  2017年   50篇
  2016年   39篇
  2015年   48篇
  2014年   54篇
  2013年   101篇
  2012年   40篇
  2011年   51篇
  2010年   54篇
  2009年   77篇
  2008年   54篇
  2007年   46篇
  2006年   49篇
  2005年   43篇
  2004年   52篇
  2003年   36篇
  2002年   43篇
  2001年   48篇
  2000年   44篇
  1999年   54篇
  1998年   35篇
  1997年   40篇
  1996年   55篇
  1995年   37篇
  1994年   27篇
  1993年   27篇
  1992年   35篇
  1991年   48篇
  1990年   36篇
  1989年   38篇
  1988年   48篇
  1987年   46篇
  1986年   47篇
  1985年   45篇
  1984年   21篇
  1983年   29篇
  1982年   20篇
  1981年   11篇
  1980年   17篇
  1979年   26篇
  1978年   20篇
  1977年   24篇
  1976年   17篇
  1975年   16篇
  1974年   11篇
  1971年   11篇
排序方式: 共有2026条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: Endothelin, a peptide with strong vasoconstrictive and mitogenic properties, has been found to increase after cardiac transplantation. We therefore assessed the association between its precursor peptide, big endothelin-1, and intimal hyperplasia and coronary flow reserve after heart transplantation. METHODS: Thirty-five patients without hemodynamically significant coronary artery disease after heart transplantation were investigated: Average peak flow velocity in the left anterior descending artery (LAD) was assessed by intracoronary Doppler at baseline as well as after injection of adenosine; coronary flow reserve was calculated as a ratio of both and was corrected for patient age and baseline average peak flow velocity. Lumen, intima + media and total vessel area were measured by intracoronary ultrasound. The plasma concentration of big endothelin-1 in venous blood was determined by radioimmunoassay. RESULTS: Patients with elevated big endothelin-1 levels (>2 fmol/ml) tended to have a decreased corrected coronary flow reserve (2.60 +/- 0.9 vs 3.21 +/- 1.0, p = 0.078). They also had a significantly larger intima + media area (5.82 +/- 2.9 vs 2.37 +/- 2.9 mm(2), p = 0.004) and total vessel area (18.36 +/- 5.8 vs 12.81 +/- 4.8 mm(2), p = 0.012) than those with normal plasma concentrations. CONCLUSIONS: Our study suggests an association between elevated big endothelin-1 plasma levels and the development of intimal hyperplasia and reduction of coronary flow reserve after cardiac transplantation.  相似文献   
3.
Idiopathic retroperitoneal fibrosis. A retrospective analysis of 60 cases   总被引:5,自引:0,他引:5  
Sixty patients with idiopathic retroperitoneal fibrosis presenting between 1965 and 1984 are reviewed. Their mean age at presentation was 56 years and the male:female ratio was 3:1. The commonest presenting symptoms were flank and abdominal pain, weight loss, nausea and polyuria. Physical examination was usually normal, expect for the presence of hypertension. Anaemia and elevation of erythrocyte sedimentation rate were usually present. Proteinuria was found in less than a third of patients at presentation and significant bacteriuria was uncommon. The correct diagnosis was made or suspected in very few patients before referral. The cumulative actuarial survival rate was 86% at 1 year and 78% at 2 years. Seventeen patients died; they were significantly older and more uraemic at the time of referral than those who survived. A few patients did well with either corticosteroid therapy or ureterolysis alone. In the majority, both operation and steroid treatment were necessary. In bilateral obstruction with residual function in both kidneys, bilateral ureterolysis proved superior to unilateral operation (each followed by steroid therapy) in conserving renal function. Operation alone or steroid therapy alone should be considered in cases where steroids or surgery respectively present particular hazards. The less traumatic unilateral operation should be considered in poor risk patients and in those whose renal function is absent on one side. In many survivors, disease activity has persisted for many years. Life-long follow-up is recommended.  相似文献   
4.
5.
Fifteen subfertile males with absent or atrophic right testes underwent ligation of left varicoceles. Sperm concentration rose significantly with correction of scrotal thermographic abnormality and nine wives (60%) became pregnant.  相似文献   
6.
A randomized controlled trial of sedation in the critically ill   总被引:2,自引:0,他引:2  
A randomized controlled trial comparing: a) a combination of oral chloral hydrate and promethazine to b) a continuous intravenous midazolam infusion, for maintenance sedation in critically ill children, was carried out. The level of sedation was assessed four hourly using a specifically devized sedation scale. Forty-four children entered the study of whom two were subsequently excluded. The number of satisfactory assessments (desired and actual levels of sedation equal) was significantly greater in the chloral hydrate and promethazine group (Chi-squared P <0.01; confidence intervals of the difference 0.06 to 0.20). The number of assessments at level 5 on the sedation scale (patient restless/distressed) was significantly greater in the midazolam group (Chi-squared P <0.05). The total number of satisfactory assessments in the two groups were only 61 and 48% respectively, suggesting that sedation can be considerably improved. Chloral hydrate and promethazine are more effective than midazolam as maintenance sedation in critically ill children. It is possible to prospectively study the efficacy of sedative drugs in critically ill children.  相似文献   
7.
Autoimmunity to spermatozoa results in the production of antisperm antibodies that usually reduce the fertility of human males. Many laboratory tests have been devised to detect antisperm antibodies, but the results of such tests do not always correlate well with each other, particularly when the tests are conducted with patients' own spermatozoa rather than donor sperm. Experience over the past 12 years at Chelsea Hospital for Women and St Bartholomew's Hospital in London has led to at Chelsea Hospital for Women and St Bartholomew's Hospital in London has led to the development of an effective method for testing and treating subfertile males. This involves using the mixed antiglobulin reaction test and the post-coital test as initial screening tests, followed by serum and seminal plasma agglutination tests (both gelatin and tray) and the sperm-cervical mucus contact tests. Suitable patients are then put on one of three steroid regimens--long-term low-dose prednisolone, intermittent high-dose methylprednisolone, or intermediate graduated-dose prednisolone. Such treatment is useful not only in cases of spontaneous autoimmunity, but also in cases involving genital infection, testicular obstruction, and in vitro fertilization or gamete intrafallopian transfer.  相似文献   
8.
The administration of protamine sulfate for the reversal of heparin anticoagulation has been associated with adverse hemodynamic changes including hypotension and decreased cardiac output. The possible direct toxic effect of protamine on human right atrial trabeculae contracting isometrically in vitro was studied. Muscles were stimulated to contract at 1 Hz in Tyrode's solution (maintained at 34 degrees C, pH 7.4) into which protamine was continuously added. Following a polynomial regression analysis, a parabolic dose-response curve resulted. The equation was: y = 95.13 + 38.76x - 278.71x2 where y = relative developed force and x = concentration of protamine (milligrams per milliliters) (r = 0.82). The estimated concentration of protamine resulting in 50% developed force was 0.48 mg/ml. In a second series of experiments, protamine was added to the bath along with a neutralizing amount of heparin. This resulted in a limited reduction in the fall of relative developed force. Thus, protamine in high concentrations alone or in complex with heparin has a direct toxic effect on human myocardial muscle mechanics, and care is warranted in its clinical use.  相似文献   
9.
10.
Combinations of murine recombinant interleukin 3 (IL-3), purified murine macrophage colony-stimulating factor (M-CSF), and human recombinant interleukin 1 alpha (IL-1 alpha) were used to determine the effects of growth factors on the measured radiosensitivity of different populations of murine colony-forming cells (CFC). The data showed that combinations of growth factors resulted in different values of CFC radiosensitivity, being less than values observed when colony growth was stimulated using a single factor. For various combinations of growth factors, Do values ranged from 106 +/- 8 to 175 +/- 24 cGy for progenitor cells in normal bone marrow; 74 +/- 3 to 171 +/- 18 cGy for primitive multipotent CFC enriched using fluorescence-activated cell sorting; and from 46 +/- 4 to 131 +/- 10 cGy for more mature granulocyte-macrophage CFC, enriched by counterflow centrifugal elutriation. Only combinations of three factors produced the high values of Do reported in experiments using unpurified conditioned medium as a stimulus for colony formation.  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