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   900篇
  免费   53篇
  国内免费   26篇
耳鼻咽喉   1篇
儿科学   47篇
妇产科学   11篇
基础医学   92篇
口腔科学   38篇
临床医学   97篇
内科学   284篇
皮肤病学   4篇
神经病学   69篇
特种医学   118篇
外科学   51篇
综合类   7篇
预防医学   28篇
眼科学   8篇
药学   85篇
肿瘤学   39篇
  2022年   3篇
  2021年   8篇
  2020年   6篇
  2018年   6篇
  2017年   4篇
  2016年   9篇
  2015年   14篇
  2014年   14篇
  2013年   17篇
  2012年   18篇
  2011年   15篇
  2010年   10篇
  2009年   26篇
  2008年   23篇
  2007年   38篇
  2006年   27篇
  2005年   26篇
  2004年   15篇
  2003年   29篇
  2002年   23篇
  2001年   31篇
  2000年   18篇
  1999年   21篇
  1998年   48篇
  1997年   47篇
  1996年   57篇
  1995年   41篇
  1994年   35篇
  1993年   33篇
  1992年   24篇
  1991年   23篇
  1990年   18篇
  1989年   36篇
  1988年   33篇
  1987年   22篇
  1986年   21篇
  1985年   23篇
  1984年   12篇
  1983年   11篇
  1982年   10篇
  1981年   9篇
  1980年   7篇
  1979年   6篇
  1978年   9篇
  1977年   9篇
  1976年   8篇
  1975年   9篇
  1973年   9篇
  1972年   5篇
  1967年   3篇
排序方式: 共有979条查询结果,搜索用时 0 毫秒
101.
Background: Clinicians and researchers have questioned whether participants in randomized control trials (RCTs) are representative of patients in the broader clinical population. Method: We compared the demographic, clinical, and personality characteristics of patients (N=256) with major depressive disorder (MDD) receiving antidepressant medication or interpersonal therapy as part of an RCT investigation (n=105) versus in a clinic (n=151). The RCT and clinic protocols were identical with the exception of recruitment procedures (advertisement versus physician referral) and assignment to treatment (randomized versus nonrandomized). Results: No significant differences emerged between the RCT participants and clinic patients for sex, age, marital status, and education. Overall, clinic patients were no more severely depressed compared to RCT participants; there was, however, a significant interaction effect. Response rates were significantly higher for RCT participants versus clinic patients. Those participating in the RCT scored significantly higher on a personality scale assessing preference for novel experiences compared to those in the clinic. Conclusions: Differences in clinical and personality variables between those receiving treatment for MDD as part of an RCT versus in a clinic exist; however, the clinical significance of these differences remains in question, as these variables were unrelated to treatment outcome. Depression and Anxiety, 2009. © 2009 Wiley‐Liss, Inc.  相似文献   
102.
Efficacy study of the small-bowel examination   总被引:8,自引:0,他引:8  
  相似文献   
103.
This study was initiated to compare lipoprotein lipase activity in isolated heart myocytes and the heparin residual compartment of perfused hearts from adult rats. Heart lipoprotein lipase activity was divided into two fractions by 1 min of heparin perfusion. Heparin-residual and myocyte lipoprotein lipase activity were lower in hearts obtained from fasted compared to fed rats. In each case, the myocyte enzyme activity was 55 to 60% of heparin-residual levels. The difference between myocyte and heparin-residual activity may be a consequence of the time and treatment required to isolate cells in that long-term in vitro exposure of heart tissue to heparin also reduces residual activity. In vivo treatment with endotoxin decreased both heparin-residual and myocyte lipoprotein lipase activities; whereas, colchicine administration increased both activities compared to saline injected rats. In this latter experiment heart heparin-residual and myocyte lipoprotein lipase activities were positively correlated (r = 0.90). The results indicate that in the mature heart intracellular lipoprotein lipase activity is primarily associated with myocytes.  相似文献   
104.
BACKGROUND: The majority of individuals with major depressive disorder are diagnosed and treated in the primary-care setting. A quantifiable critical objective in the management of depression is to achieve and sustain full symptomatic remission. The HAMD-7 is a depression metric validated in both tertiary and primary-care settings. METHODS: Herein, we further characterise the psychometric properties of the HAMD-7 in depressed patients treated in primary-care settings. Several cut-scores were evaluated for maximum agreement; diagnostic efficacy statistics with the original HAMD-7 items were also evaluated. We compared performance of the HAMD-7 in primary care to a previously characterised tertiary sample. RESULTS: The depressive symptoms most frequently endorsed (>or=70%) and most sensitive to change during antidepressant treatment in depressed primary-care patients were depressed mood, guilt, work and activities, psychic and somatic anxiety and fatigue. LIMITATIONS: This is a post hoc analysis of a primary-care database; assumptions regarding the definition of symptomatic remission in depression affect interpretation. CONCLUSION: Measurement-based care with the HAMD-7 quantifies the severity of commonly reported depressive items and their responsivity to treatment. The HAMD-7, inclusive of the suicide item, is capable of tracking symptom progress, with a validated remission cut-score.  相似文献   
105.
106.
The molecular pathogenesis of the myeloid leukemias that frequently occur in patients with Fanconi anemia (FA) is not well defined. Hematopoietic stem cells bearing inactivating mutations of FA complementation group C (FANCC) are genetically unstable and hypersensitive to apoptotic cytokine cues including IFN-gamma and TNF-alpha, but neoplastic stem cell clones that arise frequently in vivo are resistant to these cytokines. Reasoning that the combination of genetic instability and cytokine hypersensitivity might create an environment supporting the emergence of leukemic stem cells, we tested the leukemia-promoting effects of TNF-alpha in murine stem cells. TNF-alpha exposure initially profoundly inhibited the growth of Fancc-/- stem cells. However, longer-term exposure of these cells promoted the outgrowth of cytogenetically abnormal clones that, upon transplantation into congenic WT mice, led to acute myelogenous leukemia. TNF-alpha induced ROS-dependent genetic instability in Fancc-/- but not in WT cells. The leukemic clones were TNF-alpha resistant but retained their characteristic hypersensitivity to mitomycin C and exhibited high levels of chromosomal instability. Expression of FANCC cDNA in Fancc-/- stem cells protected them from TNF-alpha-induced clonal evolution. We conclude that TNF-alpha exposure creates an environment in which somatically mutated preleukemic stem cell clones are selected and from which unaltered TNF-alpha-hypersensitive Fancc-/- stem cells are purged.  相似文献   
107.
A man with polymyalgia rheumatica (patient 1) and two patients (2 and 3) with Felty's syndrome had neutropenia at the time of diagnosis. Bone marrow samples in each patient were cellular but showed an "arrest" of granulocyte maturation at the myelocyte stage. Agar colony growth of marrow cells from each patient was subnormal but increased after removal of sheep erythrocytes rosette-forming cells (thymus-dependent [T] cells) from marrow cell suspensions before culture. Preincubation of marrow cells with cortisol also enhanced colony growth. Maximum enhancement with cortisol occurred at 1 mM (patient 1), 1 microM (patient 2), and 10 nM (patient 3). Cortisol failed to enhance colony growth after removal of T cells from marrow cell suspensions. Peripheral blood lymphocytes (PBL) and PBL-conditioned medium from all three patients inhibited colony growth of normal human marrow cells. Cortisol treatment of PBL or T depletion from PBL abrogated the inhibition in coculture and with conditioned medium. Prednisone therapy resulted in the disappearance of suppressor T-cell function concomitant with hematologic improvement in patients 2 and 3, but suppressor T cells persisted in patient 1, who did not respond to prednisone. We conclude that cortisol-sensitive T lymphocytes inhibited granulopoiesis in vitro probably by elaboration of a soluble factor or factors. Our results suggest (a) that neutropenia in these patients resulted, at least in part, from T-cell suppression of granulopoiesis, (b) that the effectiveness of prednisone therapy was a result of its inhibition of suppressor T cells, and (c) that responses to glucocorticoid therapy may be predicted in such patients with the agar culture technique and cortisol dose response in vitro.  相似文献   
108.
Blood coagulation is initiated when plasma factor VII(a) binds to its essential cofactor tissue factor (TF) and proteolytically activates factors X and IX. Progressive inhibition of TF activity occurs upon its addition to plasma. This process is reversible and requires the presence of VII(a), catalytically active Xa, Ca2+, and another component that appears to be associated with the lipoproteins in plasma, a lipoprotein-associated coagulation inhibitor (LACI). A protein, LACI(HG2), possessing the same inhibitory properties as LACI, has recently been isolated from the conditioned media of cultured human liver cells (HepG2). Rabbit antisera raised against a synthetic peptide based on the N-terminal sequence of LACI(HG2) and purified IgG from a rabbit immunized with intact LACI(HG2) inhibit the LACI activity in human serum. In a reaction mixture containing VIIa, Xa, Ca2+, and purified LACI(HG2), the apparent half-life (t1/2) for TF activity was 20 seconds. The presence of heparin accelerated the initial rate of inhibition threefold. Antithrombin III alpha alone had no effect, but antithrombin III alpha with heparin abrogated the TF inhibition. LACI(HG2) also inhibited Xa with an apparent t1/2 of 50 seconds. Heparin enhanced the rate of Xa inhibition 2.5-fold, whereas phospholipids and Ca2+ slowed the reaction 2.5-fold. Xa inhibition was demonstrable with both chromogenic substrate (S-2222) and bioassays, but no complex between Xa and LACI(HG2) could be visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Nondenaturing PAGE, however, showed that LACI(HG2) bound to Xa but not to X or Xa inactivated by diisopropyl fluorophosphate. Thus, LACI(HG2) appears to bind to Xa at or near its active site. Bovine factor Xa lacking its gamma-carboxyglutamic acid-containing domain, BXa(-GD), through treatment with alpha-chymotrypsin, was used to further investigate the Xa requirement for VIIa/TF inhibition by LACI(HG2). LACI(HG2) bound to BXa(-GD) and inhibited its catalytic activity against a small molecular substrate (Spectrozyme Xa), though at a rate approximately sevenfold slower than native BXa. Preincubation of LACI(HG2) with saturating concentrations of BXa(-GD) markedly retarded the subsequent inhibition of BXa. The VII(a)/TF complex was not inhibited by LACI(HG2) in the presence of BXa(-GD), and further, preincubation of LACI(HG2) with BXa(-GD) slowed the inhibition of VIIa/TF after the addition of native Xa. The results are consistent with the hypothesis that inhibition of VII(a)/TF involves the formation of a VIIa-TF-XA-LACI complex that requires the GD of XA.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
109.
Clonal rearrangements of the Ig heavy chain (IGH) locus occur in nearly all cases of B-cell precursor acute leukemia (BCP-ALL). Some of these rearrangements may be detected by polymerase chain reaction (PCR) using VH gene framework III (FRIII) and JH consensus primers. However, about 20% of BCP-ALLs fail to amplify with this technique. To determine the causes of these PCR failures and to investigate any possible association with specific subgroups of disease, we analyzed 72 acute leukemias of defined immunophenotype and cytogenetics, comparing FRIII with VH-family leader-specific PCR methods and Southern blotting. Of 37 BCP-ALL cases, 6 (16.2%) failed totally to amplify with FRIII and JH primers. None of these cases amplified with VH leader primers. Additionally, all cases retained germline VH6 genes and 5 of 11 rearranged alleles amplified with a consensus DH primer, indicating that these rearrangements represented biallelic DH-JH recombinations. Among the 6 FRIII and VH leader PCR-negative BCP-ALL cases, there was no common immunophenotype or consistent cytogenetic abnormality, although all showed structural chromosomal abnormalities and 3 of 5 successfully karyotyped had abnormalities of chromosome 12p. 13 cases with t(9;22)(q34;q11) Philadelphia chromosome-positive [Ph+]) and IGH rearrangements (9 BCP-ALL and 4 biphenotypic cases) were also analyzed. Of 23 rearranged IGH alleles, 19 (82%) were positive by FRIII PCR, and all 4 remaining alleles were amplified by VH leader primers. Use of the leader primers in these Ph+ cases also detected 3 additional clonal rearrangements that were not anticipated from Southern blotting; such unexpected bands were not observed in 21 other Ph- cases. The additional bands represented "new" and unrelated VH rearrangements rather than VH-VH replacement events. We conclude that biallelic DHJH rearrangements occur in a subgroup of BCP-ALL; in these cases, the activation of the full VHDHJH recombination mechanism had not occurred. Therefore, these cases of BCP-ALL were arrested at an early stage of B- cell differentiation. In contrast, all Ph+ BCP-ALLs and biphenotypic acute leukemias, which may represent the transformation of multipotent hemopoietic stem cells, had undergone VHDHJH recombination. Of 9 Ph+ BCP-ALL cases, 3 also showed ongoing VHDHJH rearrangement, reflecting the persistent expression of the VHDHJH recombinase. Finally, sequence analysis of 33 rearranged VHDHJH genes showed that only 3 including 2 Ph+ BCP-ALL maintained an intact open-reading frame. Loss of the open- reading frame occurred not only because of out-of-frame VHDH and DHJH joining, but also because of VH gene mutation and deletion. These data show that most BCP-ALLs may represent the neoplastic transformation of BCPs destined to die in the bone marrow.  相似文献   
110.
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