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   1348篇
  免费   59篇
  国内免费   34篇
耳鼻咽喉   26篇
儿科学   62篇
妇产科学   19篇
基础医学   118篇
口腔科学   37篇
临床医学   123篇
内科学   375篇
皮肤病学   109篇
神经病学   34篇
特种医学   209篇
外科学   124篇
综合类   29篇
预防医学   79篇
眼科学   11篇
药学   37篇
中国医学   3篇
肿瘤学   46篇
  2021年   9篇
  2019年   12篇
  2018年   13篇
  2017年   12篇
  2016年   18篇
  2015年   25篇
  2014年   25篇
  2013年   69篇
  2012年   19篇
  2011年   15篇
  2010年   52篇
  2009年   59篇
  2008年   21篇
  2007年   30篇
  2006年   26篇
  2005年   30篇
  2004年   15篇
  2003年   13篇
  2002年   23篇
  2001年   23篇
  2000年   13篇
  1999年   21篇
  1998年   83篇
  1997年   72篇
  1996年   76篇
  1995年   49篇
  1994年   62篇
  1993年   51篇
  1992年   15篇
  1991年   15篇
  1990年   21篇
  1989年   41篇
  1988年   43篇
  1987年   33篇
  1986年   26篇
  1985年   28篇
  1984年   23篇
  1983年   12篇
  1982年   21篇
  1981年   18篇
  1980年   13篇
  1979年   17篇
  1978年   14篇
  1977年   17篇
  1976年   16篇
  1975年   12篇
  1973年   16篇
  1972年   9篇
  1971年   7篇
  1957年   7篇
排序方式: 共有1441条查询结果,搜索用时 0 毫秒
141.
The aim of this study was to assess alcoholic inpatients' smoking and coffee intake variation following withdrawal. Only moderate smokers (less than 30 cigarettes/day) showed a significant increase of cigarette consumption after alcohol withdrawal. However, their urinary cotinine level did not vary, suggesting a behavioral, and not biological, compensation through smoking following alcohol withdrawal. Heavy smokers (30 cigarettes/day or more) showed no significant clinical or biological variation of smoking behavior. Coffee consumption increased after alcohol withdrawal in all patients, irrespective of smoking habits.  相似文献   
142.
143.
144.
BACKGROUND: The increase in CD4 count may reach a plateau after some duration of virological response to highly active antiretroviral therapy (HAART). METHODS: A total of 1281 HIV-infected patients initiating HAART were enrolled in the AntiPROtease (APROCO) cohort. We investigated determinants of increase in CD4 count using longitudinal mixed models in patients who maintained a plasma HIV RNA <500 HIV-1 RNA copies/mL. RESULTS: A total of 870 patients had a virological response at month 4. The median follow-up time was 57 months. Mean estimated increases in CD4 count in patients with persistent virological response were 29.9 cells/muL/month before month 4, 6.4 cells/microL/month between months 4 and 36, and 0.7 cells/microL/month (not significantly different from 0) after month 36. Three factors were associated with a significantly positive CD4 count slope after month 36: male gender (+0.9), no history of antiretroviral therapy at baseline (+1.7) and baseline CD4 count <100 cells/microL (+2.6). In patients who maintained a virological response after 5 years of HAART, a CD4 count >500 cells/microL was achieved in 83% of those with a baseline CD4 count >or=200 cells/microL and in 45% of those with a baseline CD4 count <200 cells/microL. CONCLUSION: The increase in CD4 count reaches a plateau after 3 years of virological response. Even if patients initiating HAART with low CD4 counts still show a CD4 count increase after 3 years, it remains insufficient to overcome immune deficiency in all patients.  相似文献   
145.
<正>Rehabilitation is an integrated program of interventions that support individuals with disabilities and chronic health conditions to attain "personally fulfilling, socially meaningful,  相似文献   
146.

Background

Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic–pituitary–adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life.

Aims

To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task.

Study design

Observational repeated measures study.

Subjects

Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants.

Outcome measures

Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained.

Results

Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers.

Conclusions

Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health.  相似文献   
147.
Previous reports indicate that metronidazole is highly effective in the therapy of colonic amebiasis and in the treatment of hepatic amebic abscesses when combined with aspiration. A retrospective review of 15 cases of intestinal amebiasis and 12 patients with amebic liver abscesses treated with metronidazole alone is reported. Based on the literature and the clinical response of the patients reported herein, metronidazole is the initial drug of choice in the therapy of amebic colitis because of its ease of administration, efficacy, and low toxicity. In the treatment of hepatic amebic abscesses, metronidazole alone is adequate therapy for most cases, but occasionally there will be progression of the disease despite standard dosages of the drug.  相似文献   
148.
Muta  K; Krantz  SB; Bondurant  MC; Dai  CH 《Blood》1995,86(2):572-580
Stem cell factor (SCF), the ligand for the c-kit tyrosine kinase receptor, markedly stimulates the accumulation of erythroid progenitor cells in vitro. We now report that SCF delays erythroid differentiation among the progeny of individual erythroid progenitors while greatly increasing the proliferation of these progeny. These effects appear to be independent of an effect on maintenance of cell viability. Highly purified day-6 erythroid colony-forming cells (ECFC), consisting mainly of colony-forming units-erythroid (CFU-E), were generated from human peripheral blood burst-forming units-erythroid (BFU-E). Addition of SCF to the ECFC in serum-free liquid culture, together with erythropoietin (EP) and insulin-like growth factor 1 (IGF-1), resulted in a marked increase in DNA synthesis, associated with a delayed peak in cellular benzidine positivity and a delayed incorporation of 59Fe into hemoglobin compared with cultures without SCF. In the presence of SCF, the number of ECFC was greatly expanded during this culture period, and total production of benzidine-positive cells plus hemoglobin synthesis were ultimately increased. To determine the effect of SCF on individual ECFC, single-cell cultures were performed in both semisolid and liquid media. These cultures demonstrated that SCF, in the presence of EP and IGF-1, acted on single cells and their descendants to delay erythroid differentiation while substantially stimulating cellular proliferation, without an enhancement of viability of the initial cells. This was also evident when the effect of SCF was determined using clones of ECFC derived from single BFU-E. Our experiments demonstrate that SCF acts on individual day-6 ECFC to retard erythroid differentiation while simultaneously providing enhanced proliferation by a process apparently independent of an effect on cell viability or programmed cell death.  相似文献   
149.
Du  X; Beutler  L; Ruan  C; Castaldi  PA; Berndt  MC 《Blood》1987,69(5):1524-1527
Two new murine monoclonal antibodies, AK 1 and SZ 1, reactive with the human platelet glycoprotein (GP) Ib-IX complex have been produced by the hybridoma technique. Both AK 1 and SZ 1 immunoprecipitated the GP Ib-IX complex from Triton X-100-solubilized, periodate-labeled platelets. With trypsinized, labeled platelets, AK 1, SZ 1, and FMC 25 (epitope on GP IX) immunoprecipitated a membrane-bound proteolytic fragment of the GP Ib-IX complex consisting of GP IX and an congruent to 25,000 mol wt remnant of the alpha-chain of GP lb disulfide-linked to the beta-subunit. Unexpectedly, although AK 1 and SZ 1 immunoprecipitated purified GP Ib-IX complex, neither antibody immunoprecipitated the individual components of this complex, GP Ib or GP IX. When GP Ib and GP IX were recombined, however, AK 1 and SZ 1 again immunoprecipitated the reformed complex, strongly suggesting that both antibodies were recognizing an epitope present only on the intact complex. Cross-blocking studies indicated that AK 1 and SZ 1 recognized a very similar or identical epitope that was proximal to the epitope for FMC 25. Both AK 1 and SZ 1 bound to a similar number of binding sites (congruent to 25,000) on intact platelets as monoclonal antibodies directed against either GP lb or GP IX. The combined data suggests that GP lb and GP IX are fully complexed in the intact platelet membrane.  相似文献   
150.
We describe a new spectrin variant with a truncated beta-chain. It was discovered in a 17-year-old white boy presenting with intermittent jaundice and spleen enlargement. He also displayed numerous smooth elliptocytes. On sodium dodecyl sulfate-polyacrylamide gel, the truncated beta-chain (beta'-chain) appeared as an additional band of approximately 216 kilodaltons, migrating between spectrin beta-chain and ankyrin. It represented 30% of total beta-chain. The beta'-chain reacted with an antispectrin beta-chain monoclonal antibody. It failed to become phosphorylated when ghosts were incubated in the presence of [gamma-32P] adenosine triphosphate. Whole spectrin tetramerization was defective since the amount of spectrin dimer was increased in spectrin crude extract and the association constant of the spectrin dimer self- association was decreased. Spectrin whole tetramer isolated from spectrin crude extracts contained small quantities of beta'-chain. Spectrin tryptic peptides showed an increase of the 74,000-dalton fragment at the expense of the 80,000-dalton fragment. So far, the latter abnormality has been used to characterize a number of cases of hereditary elliptocytosis or pyropoikilocytosis with no other apparent change. In the present case, we consider that the abnormality is a consequence of the beta-chain alteration. The parents seemed asymptomatic. As a result, we regard this new spectrin variant as deriving from a de novo mutation.  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