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   1858篇
  免费   102篇
  国内免费   22篇
耳鼻咽喉   1篇
儿科学   156篇
妇产科学   54篇
基础医学   199篇
口腔科学   47篇
临床医学   175篇
内科学   442篇
皮肤病学   23篇
神经病学   39篇
特种医学   471篇
外科学   116篇
综合类   58篇
一般理论   1篇
预防医学   57篇
眼科学   13篇
药学   63篇
中国医学   3篇
肿瘤学   64篇
  2022年   5篇
  2021年   15篇
  2020年   10篇
  2019年   7篇
  2018年   19篇
  2017年   11篇
  2016年   23篇
  2015年   32篇
  2014年   36篇
  2013年   59篇
  2012年   32篇
  2011年   29篇
  2010年   80篇
  2009年   60篇
  2008年   34篇
  2007年   27篇
  2006年   34篇
  2005年   26篇
  2004年   19篇
  2003年   30篇
  2002年   31篇
  2001年   30篇
  2000年   39篇
  1999年   36篇
  1998年   139篇
  1997年   119篇
  1996年   129篇
  1995年   92篇
  1994年   75篇
  1993年   82篇
  1992年   26篇
  1991年   22篇
  1990年   16篇
  1989年   62篇
  1988年   48篇
  1987年   57篇
  1986年   52篇
  1985年   53篇
  1984年   27篇
  1983年   32篇
  1982年   36篇
  1981年   20篇
  1980年   36篇
  1979年   16篇
  1978年   17篇
  1977年   20篇
  1976年   24篇
  1975年   24篇
  1973年   4篇
  1966年   4篇
排序方式: 共有1982条查询结果,搜索用时 390 毫秒
951.
An IgG1 monoclonal antibody, 31D8, that recognizes normal neutrophil (PMN) membranes, was used to study PMN from patients with chronic myelogenous leukemia (CML). Nineteen patients with Philadelphia chromosome positive CML were followed over a ten-month period and compared with 23 normals, six patients with leukemoid reactions, and eight patients with phagocytic cell defects. The percentage of PMN binding of 31D8 among normal subjects was variable about a normal distribution with an average of 95 +/- 2% of cells binding 31D8. In contrast, there were two groups of CML patients: in 14 patients 88 +/- 3% PMN bound 31D8 while in the remaining five patients only 6 +/- 6% PMN bound 31D8. PMN 31D8 binding was normal in the control patient groups. Control antibodies 7C3 (binds to PMN precursors) and OKM1 (binds to the CR3 (iC3b) receptor) bound normally to CML neutrophils. Functionally, CML cells had normal chemotaxis to several stimuli and normal superoxide generation to phorbol myristate acetate. However, superoxide production in response to fmet-leu-phe was significantly less in 31D8 negative CML PMN than both 31D8 positive CML PMN and normal PMN which contained 85% 31D8 positive and 15% 31D8 negative PMN. Clinically, 2 of 14 CML patients with 31D8 positive PMN were in blast crisis (one extramedullary) at the time of study and the other 12 patients remained clinically stable in the chronic phase during the ten months of study. In contrast, one of five patients with 31D8 negative PMN was in blast crisis at the time of study and all four of the remaining patients progressed to either the accelerated phase or blast crisis. Three of these patients died of their disease eight to ten months after their initial study. Thus, failure of CML cells to bind 31D8 may be useful for predicting which patients are likely to progress to the accelerated phase or blast crisis.  相似文献   
952.
BACKGROUND & AIMS: The aim of this study was to compare the diagnostic yield of capsule endoscopy (CE) with double-balloon enteroscopy (DBE) in small-bowel (SB) disease using meta-analysis. METHODS: We performed a search of studies comparing CE with DBE in SB disease. Data on diagnostic yield of CE and DBE were extracted, pooled, and analyzed. The weighted incremental yield (IY(W)) (yield of CE--yield of DBE) of CE over DBE and 95% confidence intervals (95% CIs) for pooled data were calculated using a fixed-effect model (FEM) for analyses without, and a random-effect model (REM) for analyses with, significant heterogeneity. RESULTS: Eleven studies compared CE and DBE; the pooled overall yield for CE and DBE was 60% (n = 397) and 57% (n = 360), respectively (IY(W), 3%; 95% CI, -4% to 10%; P = .42; FEM). Ten studies reported vascular findings; the pooled yield for CE and DBE was 24% (n = 371) and 24% (n = 364), respectively (IY(W), 0%; 95% CI, -5% to 6%; P = .88; REM). Nine studies reported inflammatory findings; the pooled yield for CE and DBE was 18% (n = 343) and 16% (n = 336), respectively (IY(W), 0%; 95% CI, -5% to 6%; P = .89; FEM). Nine studies reported polyps/tumors; the pooled yield for CE and DBE was 11% (n = 343) and 11% (n = 336), respectively (IY(W), -1%; 95% CI, -5% to 4%; P = .76; FEM). CONCLUSIONS: CE and DBE have comparable diagnostic yield in SB disease, including obscure gastrointestinal bleeding. CE should be the initial diagnostic test because of its noninvasive quality, tolerance, ability to view the entire SB, and for determining the initial route of DBE. Because of its therapeutic capabilities, DBE may be indicated in patients with a positive finding on CE requiring a biopsy or therapeutic intervention, if suspicion for a SB lesion is high despite a negative CE, and in patients with active bleeding.  相似文献   
953.
Factor VII activity (FVIIc), a risk marker for coronary heart disease, is increased during postprandial lipemia. Factor VII activation accompanies lipolysis of triglyceride-rich lipoproteins, but the nature of this association and whether it is causal remain uncertain. To explore this issue, four patients with homozygous factor XII deficiency, four with complete factor XI deficiency, six with factor IX deficiency, and their respective age- and sex-matched controls were given two isocaloric dietary regimens, one providing on average 136 g fat and the other 19 g fat. Blood was taken before breakfast, immediately before lunch at 195 minutes, and at completion of the study at 390 minutes. All samples for each subject and matched control were assayed as one batch for FVIIc, activated factor VII, and factor VII antigen (FVIIag). Activation of factor VII was observed with the high- fat regimen but not with the low-fat regimen in all controls, factor XII-deficient patients, and factor XI-deficient patients. No factor VII activation was observed during either regimen in factor IX-deficient patients, but a normal postprandial responsiveness of factor VII to dietary fat was restored in one patient who replicated the study after factor IX therapy. Plasma FVIIag was not altered postprandially in either regimen in any group of patients or controls. Factor IX apparently plays an obligatory role in the postprandial activation of factor VII, although the mechanism remains to be determined.  相似文献   
954.
The Fc receptor for IgA (Fc alpha R, CD89) is a transmembrane glycoprotein found on monocytes, macrophages, neutrophils, and eosinophils. Here we describe the characterization of a novel isoform of the Fc alpha R cloned from a human eosinophil cDNA library. This clone, Fc alpha Rb, lacks the exon encoding the transmembrane/intracellular region of wild type Fc alpha R, which is replaced by 23 new amino acids. Expression of Fc alpha Rb mRNA could be detected in eosinophils and neutrophils. IIA1.6 murine pro-B cells transfected with Fc alpha Rb cDNA secrete high levels of the protein, but also a substantial amount of Fc alpha Rb is expressed at the cell membrane. Membrane-bound Fc alpha Rb binds IgA-coated beads equally well as wild type Fc alpha R. Surface expression is not affected by phosphatidyl inositol phospholipase C, indicating that glycosyl phosphatidyl inositol-linkage of Fc alpha Rb is not likely. In IIA1.6 cells expressing Fc alpha Rb and FcR gamma, which is necessary for signal transduction by wild type Fc alpha R, no tyrosine phosphorylation or Ca(2+)-mobilization could be observed after receptor cross-linking. These results indicate that Fc alpha Rb is likely to have a different function than wild-type Fc alpha R receptor.  相似文献   
955.
Dysfunction of the posterior tibial tendon is the most common cause of acquired flatfoot in adults; despite this, the condition is not commonly recognized. We report three cases with flatfoot secondary to spontaneous tendon rupture, in whom magnetic resonance imaging (MRI) was a helpful non-invasive technique to confirm the suspected diagnosis. This disabling entity, and the usefulness of MRI in the diagnosis and planning the appropriate treatment, are reviewed.   相似文献   
956.
Carrier detection in the Wiskott Aldrich syndrome   总被引:13,自引:1,他引:13  
The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disease characterized by immunodeficiency and severe thrombocytopenia in affected males, but no demonstrable clinical abnormalities in carrier females. Through analysis of the methylation patterns of X-linked genes that display restriction fragment length polymorphisms (RFLPs), we studied the pattern of X-chromosome inactivation in various cell populations from female relatives of patients with WAS. The peripheral blood T cells, granulocytes, and B cells of eight obligate WAS carriers were found to display specific patterns of X-chromosome inactivation clearly different from these of normal controls. Thus, carriers of WAS could be accurately identified using this analysis.  相似文献   
957.
Taketa  F; Matteson  KJ; Chen  JY; Libnoch  JA 《Blood》1980,55(1):116-118
Erythrocytes from heterozygous carriers of the high oxygen affinity mutant hemoglobin, Hb Wood, demonstrate lower rates of methemoglobin reduction than normal human red cells when incubated in the in vitro system of Beutler and Baluda. The rate of methemoglobin reduction in red cells from an individual who is heterozygous for both NADH- methoglobin reductase deficiency and Hb Wood shows the combined effects of the two mutations.  相似文献   
958.
Balloon rupture may occur during stent placement and will only become apparent when the stent has been manouvered across the target stenosis and deployment is attempted. Withdrawal may be complicated by displacement of the stent off the balloon. We describe two cases in which a power injector was used to momentarily inflate the balloon and partially expand the stent in place. The punctured balloon could then be withdrawn and the stent fully deployed, using a new balloon. © 1995 Wiley-Liss, Inc.  相似文献   
959.
Antibodies to the AIDS retrovirus, specifically to human T cell lymphotropic virus, type III, and AIDS-associated retrovirus, were detected with increasing prevalence in a population of 190 hemophiliacs from western Pennsylvania between 1981 and 1984: 7.7% in 1981, 20.0% in 1982, 45.5% in 1983, and 62.5% in 1984. The seropositive included approximately three fourths of those receiving factor VIII concentrate, nearly one third of those receiving factor IX concentrate, nearly one fifth of those receiving cryoprecipitate, and none of those receiving fresh frozen plasma. The seroconversion rate, determined on 43 seropositive hemophiliacs from this group who were serially sampled, was 0% in 1977, 4.7% in 1978, 4.9% in 1979, 2.6% in 1980, 10.5% in 1981, 52.9% in 1982, 87.5% in 1983, and 100% in 1984. Of 27 seropositive for three or more years (since 1982 or before), four (15%) have developed AIDS and seven (26%), diffuse lymphadenopathy (ARC); of 16 seropositive for less than three years, none has developed AIDS and three (19%) have developed ARC. The mean time from seroconversion to onset of ARC, 0.8 +/- 0.2 years (SEM), was shorter (P less than .001) than the time to onset of AIDS, 4.1 +/- 0.6 years. These findings confirm the widespread presence of AIDS retrovirus and support the association of these retroviruses with the acquired immunodeficiency syndrome and related conditions.  相似文献   
960.
Hemoglobin E trait reexamined: a cause of microcytosis and erythrocytosis   总被引:6,自引:0,他引:6  
The current Indochinese resettlement program in the United States has resulted in an increase in the number of persons with hemoglobin E trait. American physicians should be aware of the hematologic expressions of this innocuous condition. The hematologic manifestations of 21 persons with hemoglobin E trait were evaluated. The subjects were of Tai-dam, Vietnamese, Chinese, Laotian, and European origin. These studies showed uniform hematologic manifestations in hemoglobin E trait, characterized by slight microcytosis, by morphologic features resembling those of thalassemia minor, and often by increased erythrocyte count. Hemoglobin instability also was confirmed.  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