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   8524篇
  免费   644篇
  国内免费   19篇
耳鼻咽喉   75篇
儿科学   263篇
妇产科学   178篇
基础医学   1134篇
口腔科学   108篇
临床医学   1554篇
内科学   1447篇
皮肤病学   88篇
神经病学   800篇
特种医学   162篇
外科学   629篇
综合类   111篇
一般理论   10篇
预防医学   1411篇
眼科学   112篇
药学   530篇
中国医学   1篇
肿瘤学   574篇
  2023年   95篇
  2022年   84篇
  2021年   157篇
  2020年   135篇
  2019年   219篇
  2018年   222篇
  2017年   199篇
  2016年   188篇
  2015年   234篇
  2014年   315篇
  2013年   433篇
  2012年   679篇
  2011年   671篇
  2010年   332篇
  2009年   301篇
  2008年   547篇
  2007年   596篇
  2006年   564篇
  2005年   593篇
  2004年   503篇
  2003年   549篇
  2002年   485篇
  2001年   60篇
  2000年   44篇
  1999年   73篇
  1998年   109篇
  1997年   74篇
  1996年   54篇
  1995年   54篇
  1994年   58篇
  1993年   64篇
  1992年   33篇
  1991年   34篇
  1990年   24篇
  1989年   27篇
  1988年   33篇
  1987年   23篇
  1986年   27篇
  1985年   28篇
  1984年   38篇
  1983年   30篇
  1982年   26篇
  1981年   31篇
  1980年   27篇
  1979年   11篇
  1978年   13篇
  1977年   10篇
  1976年   10篇
  1975年   9篇
  1973年   10篇
排序方式: 共有9187条查询结果,搜索用时 0 毫秒
61.
Background and Objectives : Several countries have introduced graphic warning images aimed at discouraging smoking. The objective of this study was to evaluate the impact on smokers of graphic warnings showing cosmetically important harm caused by smoking. Methods : Fifty‐six adult smokers were randomly assigned to view either written smoking warnings or the same written warnings with related graphic images. The smokers viewed the warnings at a rate of one per week for 4 weeks. The smokers were assessed before and after the warnings with regard to stage of change toward smoking cessation and level of smoking. Results : The randomized control trial showed that the warnings with graphic images led to significantly more progress in stage of change toward smoking cessation than written warnings alone. However, the images did not lead to decreases in smoking rates. Conclusions and Scientific Significance : The results indicate that written smoking warnings accompanied by images of cosmetically important harm caused by smoking have more potential than warnings alone in prompting changes in the direction of quitting. (Am J Addict 2012;21:555–557)  相似文献   
62.
63.
Objectives: The effects of prenatal exposure to Polychlorinated biphenyls (PCBs) on the development of asthma, frequent ear infections, and eczema/hay fever are not well understood. We aim to investigate associations between prenatal PCB exposure and these health outcomes in the offspring of women who worked at the LaSalle Electrical Utilities Company (EUC). Methods: A retrospective cohort with at least one live birth and known employment time at EUC was eligible for this analysis. Exposure was defined and categorized by the number of fiscal quarters worked during the PCB era (1952–1981). A total of 288 women with 800 live births were included. A Chi-Square test was used to compare maternal and child characteristics across exposure groups and repeated measures logistic regression, controlling for clustering among siblings, was used to assess the associations between prenatal PCB exposure and these outcomes. Results: After adjustment for confounding and independent maternal predictors, 1–4 quarters of prenatal exposure to PCBs increased the odds for asthma (OR 3.24[1.30–8.09]), eczema/hay fever (OR 3.29[1.54–7.04]), and frequent ear infections (OR 2.24[1.19–4.22]) when compared with persons unexposed/exposed only to naphthalenes. The significance of the associations varied by exposure period and level of exposure, with the strongest associations in those employed exclusively after 1952 when PCBs were introduced. Conclusions: These results support previous findings of associations of prenatal exposure to PCBs with asthma, eczema/hay fever, and frequent ear infections. Additional prospective studies are needed to confirm these findings. Also required are more precise PCB exposures to separate them from other exposures in occupational settings.  相似文献   
64.
We present a case and discuss stroke related to human immunodeficiency virus (HIV) infection and the difficulties of reaching a firm diagnosis of the cause of the aneurysmal vasculopathy. In the absence of a clear aetiology we suggest looking for varicella zoster virus (VZV) replication in the cerebrospinal fluid (CSF) by polymerase chain reaction (PCR) and treating with intravenous acyclovir, aiming for HIV control with appropriate antiretroviral therapy and providing suitable antiplatelet agents. If there is a high index of suspicion of VZV, therapy with acyclovir may be prudent even if the CSF PCR is negative (as may occur after the first 2 weeks of reactivation of infection). Determination of a VZV plasma:CSF IgG ratio is not readily available and would only provide surrogate support for a previous VZV infection in the central nervous system compartment.  相似文献   
65.
Aspiration of iliac crest bone marrow (ICBM) remains the most frequent technique used in harvesting multipotential stromal cells (MSCs) for bone regeneration. Although this tissue type is easily accessed by a surgeon, it has a low frequency of MSCs, which is significant given the high cell numbers required for bone regeneration strategies. Lipoaspirates possess higher MSC frequencies, albeit cells with a differentiation profile less suited to orthopaedic interventions. Intra-medullary cavities of long bones have previously been shown to harbour MSCs in animals, however evaluation of their frequency, differentiation capacity and phenotype in humans had not previously been performed. Long bone fatty bone marrow (LBFBM) was collected prior to harvesting bone graft. Basic cellular compositions of donor-matched LBFBM and ICBM aspirates, including the numbers of CD34(+) hematopoietic stem cells and CD31(+) endothelial cells, were similar. MSCs were enumerated using colony-forming-unit-fibroblast assays and flow cytometry for the presence of a resident LBFBM CD45(-/low) CD271(+) MSC population and revealed a trend for higher MSC numbers (average 5 fold, n=6) per millilitre of LBFBM compared to donor-matched ICBM. Functional characteristics of resident MSCs, including their growth rates, differentiation potentials and surface phenotypes (CD73(+)CD105(+)CD90(+)) before and after culture-amplification, were similar. Enhanced numbers of MSCs could be recovered following brief enzymatic treatment of solid fragments of LBFBM. Our findings therefore reveal that the intramedullary cavity of the human femur is a depot of MSCs, which, although closely associated with fat, have a differentiation profile equivalent to ICBM. This anatomical site is frequently accessed by the orthopaedic/trauma surgeon and aspiration of the intramedullary cavity represents a 'low-tech' method of harvesting potentially large numbers of MSCs for regenerative therapies and research.  相似文献   
66.
Study Type – Therapy (cohort) Level of Evidence 4 What's known on the subject? and What does the study add? Accumulating evidence suggests that inflammation may contribute to the development of BPH and LUTS. Therefore, it is plausible that anti‐inflammatory agents, such as aspirin and other NSAIDs, may reduce the risk of BPH/LUTS, as was observed in a recent analysis of daily aspirin use and BPH/LUTS risk in the Olmsted County Study of Urinary Symptoms and Health Status in Men. The present study, conducted in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, found no association for recent aspirin or ibuprofen use with the risk of BPH/LUTS.

OBJECTIVE

  • ? To investigate the relationship between non‐steroidal anti‐inflammatory drug (NSAID) use and the incidence of benign prostatic hyperplasia (BPH)‐related outcomes and nocturia, a lower urinary tract symptom (LUTS) of BPH, in light of accumulating evidence suggesting a role for inflammation in BPH/LUTS development.

PATIENTS AND METHODS

  • ? At baseline, participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial completed questions on recent, regular aspirin and ibuprofen use, BPH surgery, diagnosis of an enlarged prostate/BPH, and nocturia. Participants in the intervention arm also underwent a digital rectal examination (DRE), from which prostate dimensions were estimated, as well as a prostate‐specific antigen (PSA) test. Only participants in the intervention arm without BPH/LUTS at baseline were included in the analysis (n= 4771).
  • ? During follow‐up, participants underwent annual DREs and PSA tests, provided annual information on finasteride use, and completed a supplemental questionnaire in 2006–2008 that included additional questions on diagnosis of an enlarged prostate/BPH and nocturia.
  • ? Information collected was used to investigate regular aspirin or ibuprofen use in relation to the incidence of six BPH/LUTS definitions: diagnosis of an enlarged prostate/BPH, nocturia (waking two or more times per night to urinate), finasteride use, any self‐reported BPH/LUTS, prostate enlargement (estimated prostate volume ≥30 mL on any follow‐up DRE) and elevation in PSA level (>1.4 ng/mL on any follow‐up PSA test).

RESULTS

  • ? Generally, null results were observed for any recent, regular aspirin or ibuprofen use (risk ratio = 0.92–1.21, P= 0.043–0.91) and frequency of use (risk ratios for one category increase in NSAID use = 0.98–1.11, P‐trends = 0.10–0.99) with incident BPH/LUTS.

CONCLUSION

  • ? The findings obtained in the present study do not support a protective role for recent NSAID use in BPH/LUTS development.
  相似文献   
67.

Background/objective

Examine associations of type and quantity of physical therapy (PT) interventions delivered during inpatient spinal cord injury (SCI) rehabilitation and patient characteristics with outcomes at the time of discharge and at 1 year post-injury.

Methods

Physical therapists delivering routine care documented details of PT interventions provided. Regression modeling was used to predict outcomes at discharge and 1 year post-injury for a 75% subset; models were validated with the remaining 25%. Injury subgroups also were examined: motor complete low tetraplegia, motor complete paraplegia, and American Spinal Injury Association (ASIA) Impairment Scale (AIS) D motor incomplete tetra-/paraplegia.

Results

PT treatment variables explain more variation in three functionally homogeneous subgroups than in the total sample. Among patients with motor complete low tetraplegia, higher scores for the transfer component of the discharge motor Functional Independence Measure () are strongly associated with more time spent working on manual wheelchair skills. Being male is the most predictive variable for the motor FIM score at discharge for patients with motor complete paraplegia. Admission ASIA lower extremity motor score (LEMS) and change in LEMS were the factors most predictive for having the primary locomotion mode of “walk” or “both (walk and wheelchair)” on the discharge motor FIM for patients with AIS D injuries.

Conclusion

Injury classification influences type and quantity of PT interventions during inpatient SCI rehabilitation and is a strong predictor of outcomes at discharge and 1 year post-injury. The impact of PT treatment increases when patient groupings become more homogeneous and outcomes become specific to the groupings.

Note

This is the second of nine articles in the SCIRehab series.  相似文献   
68.
69.
BACKGROUND: Janus Kinase (JAK) 3 is a tyrosine kinase essential for proper signal transduction downstream of selected cytokine receptors and for robust T-cell and natural killer cells activation and function. JAK3 inhibition with CP-690,550 prevents acute allograft rejection. To provide further insight into the mechanisms of efficacy, we investigated the immunomodulatory effects of CP-690,550 in vitro and in vivo in nonhuman primates. METHODS: Pharmacodynamic assessments of lymphocyte activation, function, proliferation and phenotype were performed in three settings: in vitro in whole blood isolated from untransplanted cynomolgus monkeys (cynos), in vivo in blood from untransplanted cynos dosed with CP-690,550 for 8 days, and in vivo in blood from transplanted cynos immunosuppressed with CP-690,550. Cell surface activation markers expression, IL-2- enhanced IFN-gamma production, lymphocyte proliferation and immune cell phenotype analyzes were performed with multiparametric flow cytometry. RESULTS: In vitro exposure to CP-690,550 resulted in significant reduction of IL-2-enhanced IFN-gamma production by T-cells (maximum inhibition of 55-63%), T-cell surface expression of CD25 (50% inhibitory concentration (IC50); 0.18 microM) and CD71 (IC50; 1.6 microM), and T-cell proliferative capacities measured by proliferating cell nuclear antigen expression (IC50; 0.87 microM). Similar results were observed in animals dosed with CP-690,550. In addition, transplanted animals displayed significant reduction of NK cell (90% from baseline) and T-cell numbers whereas CD8 effector memory T-cell populations were unaffected. CONCLUSIONS: Potent in vitro and in vivo immunomodulatory effects of the JAK3 inhibitor CP-690,550 likely contribute to its efficacy in the prevention of organ allograft rejection.  相似文献   
70.
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