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   1072篇
  免费   62篇
  国内免费   78篇
耳鼻咽喉   1篇
儿科学   43篇
妇产科学   9篇
基础医学   130篇
口腔科学   17篇
临床医学   188篇
内科学   276篇
皮肤病学   23篇
神经病学   14篇
特种医学   287篇
外科学   39篇
综合类   30篇
预防医学   38篇
眼科学   3篇
药学   83篇
肿瘤学   31篇
  2021年   4篇
  2019年   3篇
  2018年   8篇
  2017年   5篇
  2016年   8篇
  2015年   9篇
  2014年   12篇
  2013年   18篇
  2012年   18篇
  2011年   12篇
  2010年   25篇
  2009年   38篇
  2008年   20篇
  2007年   69篇
  2006年   16篇
  2005年   24篇
  2004年   14篇
  2003年   15篇
  2002年   16篇
  2001年   23篇
  2000年   24篇
  1999年   24篇
  1998年   68篇
  1997年   78篇
  1996年   50篇
  1995年   65篇
  1994年   37篇
  1993年   37篇
  1992年   23篇
  1991年   21篇
  1990年   16篇
  1989年   42篇
  1988年   38篇
  1987年   39篇
  1986年   35篇
  1985年   51篇
  1984年   24篇
  1983年   19篇
  1982年   26篇
  1981年   21篇
  1980年   25篇
  1979年   5篇
  1978年   7篇
  1977年   17篇
  1976年   16篇
  1975年   9篇
  1973年   4篇
  1966年   3篇
  1944年   11篇
  1943年   3篇
排序方式: 共有1212条查询结果,搜索用时 11 毫秒
21.
22.
Aims. To examine the utility and validate the use of the Cardiac Depression Scale in patients who had first‐time coronary artery bypass graft surgery. Background. The Beck Depression Inventory, though frequently used, may not be sufficiently sensitive for use in cardiac patients. The Cardiac Depression Scale has been shown to identify the range of depression in medical cardiac patients. Design. Survey. Methods. The Beck Depression Inventory and Cardiac Depression Scale were administered to 120 men at hospital discharge, as well as six, 12 and 36 weeks postoperatively. Cronbach’s α scores were calculated for the measures at each point. Changes in scores over time were analysed using repeated measures analysis of variance. Associations between the measures scores were calculated using Pearson product–moment correlations. Agreement between the measures’ dichotomised scores (depression/no depression) was examined using Cohen’s Kappa statistic. Results. Internal consistency was similar for the Beck Depression Inventory (0·793–0·904) and Cardiac Depression Scale (0·859–0·910). Depression scores decreased over time with the Beck Depression Inventory [F(2·50, 175·29) = 22·27, p < 0·001] and Cardiac Depression Scale [F(2·68, 190·37) = 13·18, p < 0·001]. The measures had similar power [Cohen’s f = 0·65 (Beck Depression Inventory) and 0·43 (Cardiac Depression Scale)] to reveal changes over time. The continuous scores were highly correlated at each point [0·737 (p < 0·001)–0·819 (p < 0·001)]. However, when dichotomised scores were compared, the chance corrected level of agreement was less impressive [0·198 (p = 0·014)–0·381 (p < 0·001)]. Conclusions. The Cardiac Depression Scale may have utility for use with surgical cardiac patients. However, continued examination of this measure of depression is warranted. Relevance to clinical practice. Given the prevalence of depression and its negative impact on coronary artery disease, it is important to identify even mild depression in cardiac patients. Using a measure of depression specifically for cardiac patients, rather than a generic measure, may best accomplish this goal.  相似文献   
23.
The effect of a 4-fold increase in alpha1-acid glycoprotein (AGP) on the antiviral efficacy of 5 human immunodeficiency virus (HIV) protease inhibitors (PIs) was examined by the effect of HIV PIs on p24 production in peripheral blood mononuclear cells infected with protease wild-type and PI-resistant HIV isolates. For wild-type virus, the efficacy of the PIs at trough concentrations was unaffected by a 4-fold increase in AGP. With the partially HIV PI-resistant isolate, a 4-fold increase in AGP resulted in 2%, 30%, 37%, 37%, and 42% loss of activity for indinavir, saquinavir, nelfinavir, ritonavir, and amprenavir, respectively. The high-level HIV PI-resistant isolate had a greater loss in activity. The change in IC50 secondary to the addition of AGP was the greatest for ritonavir, nelfinavir, and amprenavir and lowest for indinavir. These data suggest that the target plasma concentration for the highly bound HIV PIs may need to be raised in subjects with elevated AGP who harbor partially PI-resistant isolates.  相似文献   
24.
25.
OBJECTIVES: Linezolid soft tissue penetration and serum antimicrobial activity were analysed in six patients with peripheral vascular disease and severe diabetic foot infections requiring surgical intervention. METHODS: Blood draws (1, 3, 6, 9 and 12 h after initiation of a 1 h infusion) and a viable soft tissue sample at the site of infection were obtained in patients receiving linezolid (600 mg every 12 h) on the day of surgery. Concentrations of linezolid were determined by HPLC in both tissue (pre-treated with tissue lysis buffer) and serum. In addition, serum inhibitory and bactericidal activity (dilution titres 1:2-1:32) of linezolid was determined in these patients against strains of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin (vancomycin MICs = 2, 4, 8, 256 and >256 mg/L). RESULTS: Linezolid concentrations in tissue were found to be 51% (range, 18% to 78%) of simultaneous serum concentrations. Rapid (1 h) and prolonged (12 h) inhibitory activity (titres > or = 1:2) was observed for linezolid against each of the study isolates. Furthermore, bactericidal activity (titres > or = 1:2) was observed for at least 6 h (50% of the dosing interval) against four of these five strains. CONCLUSIONS: These findings suggest that linezolid could be effective in the treatment of multidrug-resistant MRSA even when concentrations at the infection site are diminished due to impaired blood flow.  相似文献   
26.
There is increasing evidence that genetic factors have a role in differential susceptibility to depression in response to severe or chronic adversity. Studies in animals suggest that nitric oxide (NO) signalling has a key role in depression-like behavioural responses to stress. This study investigated whether genetic variation in the brain-expressed nitric oxide synthase gene NOS1 modifies the relationship between psychosocial stress and current depression score. We recruited a population sample of 1222 individuals who provided DNA and questionnaire data on symptoms and stress. Scores on the List of Life-Threatening Experiences (LTE) questionnaire for the last year and self-rated current financial hardship were used as measures of recent/ongoing psychosocial stress. Twenty SNPs were genotyped. Significant associations between eight NOS1 SNPs, comprising two regional haplotypes, and current depression score were identified that survived correction for multiple testing when current financial hardship was used as the interaction term. A smaller three-SNP haplotypes (rs10507279, rs1004356 and rs3782218) located in a regulatory region of NOS1 showed one of the strongest effects, with the A-C-T haplotype associating with higher depression scores at low adversity levels but lower depression scores at higher adversity levels (p=2.3E-05). These results suggest that NOS1 SNPs interact with exposure to economic and psychosocial stressors to alter individual''s susceptibility to depression.  相似文献   
27.
A human malignant melanoma cell line (M3Dau) was observed by electron microscopy to interact directly with human platelets and induced platelet aggregation. Fab fragments of a monoclonal antibody MoAb (LYP18), directed against the platelet glycoprotein (GP) IIb-IIIa complex, inhibited platelet-melanoma interactions and platelet-platelet aggregation. M3Dau melanoma cells bind LYP 18 and synthesize IIb-IIIa- like GPs. When the melanoma cells were preincubated with LYP 18, tumor- platelet interaction did not occur, suggesting that the interaction may be mediated by the IIb-IIIa-like GPs present on the melanoma cell surface. Glanzmann's thrombasthenic platelets, lacking GPIIb and IIIa, did not interact with melanoma cells, indicating that the platelet GPIIb-IIIa complex is also necessary for the platelet-melanoma cell interaction. This work demonstrates the importance of the IIb-IIIa-like GPs, present on M3Dau melanoma cells, in mediating tumor-platelet interactions.  相似文献   
28.
The functional capacities of granulocytes in patients with chronic granulocytic leukemia are still a subject of controversy, probably due to the heterogeneity of the abnormalities observed from patient to patient. For a better definition of these abnormalities, 14 patients with untreated chronic granulocytic leukemia were studied. The patients were divided into three groups on the basis of the functional activities of their phagocytosing granulocytes. In four patients (group I), the granulocytes were normal in respect to particle ingestion, nitroblue tetrazolium (NBT)-stimulated reduction, cyanide-insensitive oxygen (O2) consumption, superoxide anion (O2-)-stimulated production, hydrogen peroxide (H2O2) production, and iodination. They also had a normal myeloperoxidase (MPO) content. In four patients (group III), the granulocytes were significantly defective in all of these activities. In the six remaining patients (group II), all the initial metabolic steps of the phagocytosing granulocytes (ingestion, NBT reduction, O2 consumption, O2-production, H2O2 production) were normal, as were the MPO content of the granulocytes, while iodination was strikingly decreased. These metabolic features suggested a degranulation defect which was observed ultrastructurally in the only patient studied among these six. The phagocytosing granulocytes of this patient did not degranulate and no deposits of MPO activity were seen in the phagosomes.  相似文献   
29.
Two cardioacceleratory peptides from the corpora cardiaca of Periplaneta americana have been purified by gel filtration and reversed-phase liquid chromatography, Based on analysis of the intact factors and their chymotryptic fragments, we have assigned the primary structure of these octapeptides as pGlu-Val-Asn-Phe-Ser-Pro-Asn-Trp-NH2, designated periplanetin CC-1, and pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-NH2, designated periplanetin CC-2. They represent new members of a family of invertebrate peptides that includes locust adipokinetic hormone and crustacean red-pigment concentrating hormone. Both peptides show adipokinetic activity in grasshoppers and hyperglycemic activity in cockroaches. One of these peptides (CC-2) has provocative sequence homology with the NH2-terminal portion of glucagon.  相似文献   
30.
Schooley  J. C.; Mahlmann  L. J. 《Blood》1972,39(1):31-38
The serum erythropoietin levels ofadult male and female rats exposedimmediately after nephrectomy to asimulated altitude of 22,000 ft for 5 hris measurable but decreased to aboutl5% of normal. Erythropoietin is notdetected in the serum of adult femaleand male rats when the interval between nephrectomy and the beginningof the hypoxic exposure is increasedto 8 and 16 rr, respectively. The abilityof an anephric rat to respond to thishypoxic stimulus progressively decreases with increasing time afternephrectomy. The ability of young anephric rats to increase their serum erythropoietin levels is little altered if therats are exposed to hypoxia immediately after nephrectomy, but exposureto the same hypoxic stimulus 24 hrlater results in a significant reductionin erythropoietin production. The ability of both normal and anephric ratsto produce erythropoietin is reduced orabolished by actinomycin D. Theserum erythropoietin produced in hypoxic anephric rats is immunologicallyindistinguishable from normal erythropoietin.

Submitted on April 5, 1971 Revised on August 9, 1971 Accepted on August 10, 1971  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