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   2847篇
  免费   177篇
  国内免费   76篇
耳鼻咽喉   15篇
儿科学   86篇
妇产科学   39篇
基础医学   307篇
口腔科学   36篇
临床医学   315篇
内科学   761篇
皮肤病学   93篇
神经病学   127篇
特种医学   303篇
外科学   336篇
综合类   73篇
一般理论   2篇
预防医学   200篇
眼科学   36篇
药学   179篇
中国医学   4篇
肿瘤学   188篇
  2021年   19篇
  2020年   26篇
  2019年   30篇
  2018年   42篇
  2017年   20篇
  2016年   34篇
  2015年   36篇
  2014年   40篇
  2013年   59篇
  2012年   100篇
  2011年   86篇
  2010年   75篇
  2009年   88篇
  2008年   84篇
  2007年   131篇
  2006年   97篇
  2005年   95篇
  2004年   81篇
  2003年   82篇
  2002年   104篇
  2001年   90篇
  2000年   90篇
  1999年   62篇
  1998年   99篇
  1997年   80篇
  1996年   81篇
  1995年   70篇
  1994年   62篇
  1993年   64篇
  1992年   66篇
  1991年   56篇
  1990年   68篇
  1989年   84篇
  1988年   65篇
  1987年   66篇
  1986年   56篇
  1985年   62篇
  1984年   52篇
  1983年   42篇
  1982年   31篇
  1981年   30篇
  1980年   26篇
  1979年   23篇
  1978年   22篇
  1977年   44篇
  1976年   28篇
  1975年   33篇
  1974年   32篇
  1973年   29篇
  1972年   25篇
排序方式: 共有3100条查询结果,搜索用时 15 毫秒
81.

Introduction

Spain, which has one of the largest migrant populations in Europe, has committed to eliminating the hepatitis C virus (HCV). The aim of this study was to estimate the prevalence of HCV among migrant groups in Spain, a country of 46 million people, with an estimated HCV-antibody prevalence of 1.7%.

Methods

Studies on HCV and migration in Spain were identified by systematically searching three databases from the first records to 30 November 2017, and consulting experts at the Ministry of Health and in the 17 Spanish autonomous communities. A meta-analysis was conducted to determine pooled HCV prevalence for the general migrant population. Prevalences were also calculated for high-risk migrant populations and populations who had undergone hospital screening, stratified by region of origin.

Results

Out of 243 studies identified, 26 met the eligibility criteria. The meta-analysis of the general migrant population found HCV antibody prevalence to be 1.6%. Migrants originating from European countries, including those at high or moderate risk for HCV, had the highest pooled prevalence (7.1%). In the general migrant population, prevalence was highest among sub-Saharan African migrants (3.1%) and lowest among Latin American migrants (0.2%).

Conclusion

Based on the limited available data, the prevalence among the general migrant population was found to be the same as the general Spanish population. Further research is needed to more accurately determine HCV prevalence for the overall migrant population and specific migrant subpopulations with a higher risk in the country as a whole and in each of Spain's 17 autonomous communities.  相似文献   
82.
A luminescent bioassay for thyroid blocking antibodies   总被引:4,自引:0,他引:4  
OBJECTIVE: Thyroid blocking antibodies (TBAb) have a role in the development of hypothyroidism and in the neonate are responsible for transient hypothyroidism. Specific measurement of TBAb requires a bioassay, but current methods are lengthy and cumbersome. We describe a rapid luciferase-based method for the detection of TBAb using the lulu* cell line which is suitable for the provision of a clinical service PATIENTS AND MEASUREMENTS: Chinese hamster ovary (CHO) cells were transfected with human TSH-R together with G418 resistance and a cAMP responsive luciferase construct. Stable pools of transfected cells were selected and clones identified by limiting dilution. Clone lulu* gave the best response to stimulation by TSH and was used to develop a bioassay for TBAb. The luminescent bioassay conditions have been optimized and validated using 12 serum samples from patients found to be TBAb positive in a bioassay using an established method quantifying cAMP by radioimmunoassay (RIA). The effect of thyroid stimulating antibodies (TSAb) on the calculation of Inhibition Index (InI) using two previously described formulae have been investigated and we have used serum containing both TSAb and TBAb to investigate detection of TBAb in samples containing more than one type of activity. RESULTS: Lulu* displays a dose dependent increase in luciferase expression in response to stimulation with bovine (b) TSH which is more effective in serum free medium than in salt free buffer. TSH stimulated luciferase expression can be inhibited by TBAb in either serum or an immunoglobulin preparation. Using optimized assay conditions, challenging 10% serum against 1 U/l bTSH in culture medium, we have tested 31 euthyroid sera to determine a reference range: InI values >23% were considered positive. Twelve samples previously shown to contain TBAb by an established method quantifying cAMP by RIA were positive by the luciferase-based assay. Of control sera, 20/20 systemic lupus erythematosus, 13/14 rheumatoid arthritis, 12/12 multinodular goitre were negative. We demonstrated that if more complex formulae are used to calculate InI, false positive TBAb results can be obtained in samples containing only TSAb. Finally, when sera contain both TSAb and TBAb, the net activity of stimulating and blocking antibodies is detected in the bioassay. Where TSAb are also present, analysis of serum may be required at several dilutions to detect TBAb. CONCLUSIONS: We describe the production of a new cell line, lulu*, and its use to develop a luminescent bioassay for TBAb suitable for clinical use. Comparing two established methods of calculating TBAb, we found that they do not give identical results. In light of this, the high prevalence reported for TBAb in some studies has to be considered with caution.  相似文献   
83.
OBJECTIVE: TGPO autoantibodies (aAbs) that bind simultaneously to thyroglobulin (Tg) and thyroperoxidase (TPO) are present in the serum of patients with autoimmune thyroid diseases (AITD) and have been found to differ from monospecific Tg and TPO aAbs. To obtain further insights on the prevalence defined as the rate of occurrence and significance of TGPO aAbs in a large population, we carried out a collaborative study involving 15 European teams. METHODS: Serum samples from 3122 patients with various thyroid and non-thyroid diseases and normal subjects were assayed using a novel TGPO aAb detection kit. This test was designed so that TGPO aAbs are trapped between the Tg-coated solid phase and the soluble TPO labeled with a radioiodinated monoclonal antibody. RESULTS: Only three out of the 220 normal subjects (prevalence of 1.4%) were found to have positive TGPO aAb levels, which were mainly observed in the patients with AITD: the group of patients suffering from Hashimoto's thyroiditis had a TGPO aAb prevalence of 40.5% (n=437 patients), those with Graves' disease, a prevalence of 34.6% (n=645) and those with post-partum thyroiditis, 16.0% (n=243). Among the non-AITD patients with positive TGPO aAb levels, the TGPO aAb prevalence ranged from 20.7% among those with thyroid cancer (n=246) to 0% among those with toxic thyroid nodules (n=47). Among the patients with non-thyroid diseases, the TGPO aAb prevalence ranged from 9.8% in the case of Biermer's pernicious anemia (n=78) to 0% in that of premature ovarian failure (n=44). It is worth noting that the groups showing the highest TGPO aAb prevalence also contained the patients with the highest TGPO aAb titers. Statistical comparisons between the TGPO aAb prevalences in the various groups showed that TGPO aAb could be used as a parameter to distinguish between the groups of Hashimoto's and Graves' patients and between the women with post-partum thyroiditis and the post-partum women with only Tg and/or TPO aAb established during early pregnancy. Unexpectedly, the correlations between TGPO aAbs and Tg and TPO aAbs were found to depend mainly on the assay kit used. CONCLUSION: High TGPO aAb titers are consistently associated with AITD but the reverse was not found to be true. TGPO aAbs are a potentially useful tool, however, for establishing Hashimoto's diagnosis, and would be worth testing in this respect with a view to using them for routine AITD investigations.  相似文献   
84.
85.
During the last three decades, several myeloablative conditioning regimens have been used for AML allografts. In this review, we systematically examine the data from studies reporting on myeloablative conditioning regimens for AML allografts. High-dose busulfan combined with cyclophosphamide (BuCy) and cyclophosphamide in combination with total body irradiation (CyTBI) are the two most commonly used conditioning regimens for AML allografts. From the available data, there are no significant differences in survival with these two regimens. A small benefit of decreased relapse rate with CyTBI is counterbalanced by a nonsignificant increase in treatment-related mortality. The incidence of veno-occlusive disease is significantly higher in patients treated with BuCy. Therapeutic monitoring of busulfan was not reported in any of the studies comparing the regimens. Either of the regimens can be used for AML allografts, and the choice may ultimately depend on local availability and expertise. Further improvements may be possible from modifications of the standard regimens. Data from these latter studies seem to be encouraging, but are not based on comparative randomized trials.  相似文献   
86.
With increasing donor age, the potential of transmitting diseases from donor to recipient reaches new dimensions. Potentially transmittable diseases from donors include infections, congenital disorders, and acquired illnesses like autoimmune diseases or malignancies of hematological or nonhematological origin. While established nonmalignant or malignant diseases might be easy to discover, early-stage hematological diseases like CML, light-chain multiple myelomas, aleukemic leukemias, occult myelodysplastic syndromes and other malignant and nonmalignant diseases might not be detectable by routine screening but only by invasive, new and/or expensive diagnostic tests. In the following article, we propose recommendations for donor work-up, taking into consideration the age of the donors. In contrast to blood transfusions, stem cells from donors with abnormal findings might still be acceptable for HCT, when no other options are available and life expectancy is limited. This issue is discussed in detail in relation to the available donor and stem cell source. Finally, the recommendations presented here aim at harmonized worldwide work-up for donors to insure high standard quality.  相似文献   
87.
88.
Monoclonal gammopathy of undetermined significance (MGUS) occurs in 3–7% of the elderly population, with higher prevalence in renal failure patients, and is associated with a 25‐fold increased lifetime risk for plasma cell myeloma (PCM), also known as multiple myeloma. Using the California State Inpatient, Emergency Department, and Ambulatory Surgery Databases components of the Healthcare Cost and Utilization Project (HCUP), we sought to determine whether patients with MGUS who undergo solid organ allograft (n = 22 062) are at increased adjusted relative risk (aRR) for hematologic malignancy and other complications. Among solid organ transplant patients, patients with preexisting MGUS had higher aRR of PCM (aRR 19.46; 95% CI 7.05, 53.73; p < 0.001), venous thromboembolic events (aRR 1.66; 95% CI 1.15, 2.41; p = 0.007), and infection (aRR 1.24; 95% CI 1.06, 1.45; p = 0.007). However, when comparing MGUS patients with and without solid organ transplant, there was decreased aRR for PCM with transplant (aRR 0.34; 95% CI 0.13, 0.88; p = 0.027), and increased venous thromboembolic events (aRR 2.33; 95% CI 1.58, 3.44; p < 0.001) and infectious risks (aRR 1.44; 95% CI 1.23, 1.70; p < 0.001). While MGUS increased the risk of PCM overall following solid organ transplantation, there was lower risk of PCM development compared to MGUS patients who did not receive a transplant. MGUS should not preclude solid organ transplant.  相似文献   
89.
Alteration of the TAL1 locus is the most common nonrandom genetic defect in childhood T-cell acute lymphoblastic leukemia (T-ALL). To determine if rearrangements of the TAL1 proto-oncogene confer a distinct leukemic phenotype, we studied leukemic peripheral blood or bone marrow samples from 182 children with newly diagnosed T-ALL enrolled on Pediatric Oncology Group treatment protocols. Forty-eight (26%) of the samples had a local rearrangement of the TAL1 locus. Demographic and clinical features were compared for patient subgroups with and without TAL1 rearrangements. The only clinical correlates that were significantly associated with TAL1 gene rearrangements were higher white blood cell count (P = .017) and higher hemoglobin (P = .007) at diagnosis. Immunophenotypically, samples with altered TAL1 were more likely to be CD2+ (P = .001) and lack CD10 (cALLa) expression (P = .007) than those without the rearrangement. There was a trend toward improved event-free survival (EFS) in patients with TAL1 rearrangements (4-year EFS was 44% +/- 7% for patients without the rearrangements v 59% +/- 11% for those with rearrangements), but the difference was not significant (P = .34). The role of TAL1 in leukemogenesis has yet to be clearly defined, and the prognostic significance of TAL1 gene rearrangements in T-ALL deserves further study.  相似文献   
90.
HLA-identical bone marrow transplantation (BMT) may be complicated by graft-versus-host disease or graft rejection. Both complications are thought to be initiated by recognition of minor histocompatibility (mH) antigens by HLA-restricted mH-antigen-specific T lymphocytes. Using HLA- A2-restricted mH antigens HA-1-, -2-, and -4-, and HY-specific cytotoxic T lymphocyte (CTL) clones, we studied the recognition by these CTL clones of interleukin-2 (IL-2)-stimulated T cells (IL-2 blasts), BM mononuclear cells (BMMNCs), and hematopoietic progenitor cells (HPCs). We showed that, when IL-2 blasts from the BM donors who were investigated were recognized by the HA-1-, -2-, and -4-, and HY- specific CTL clones, their BMMNCs and HPCs were recognized as well by these CTL clones, resulting in antigen-specific growth inhibition of erythrocyte burst-forming units (BFU-E), colony-forming units- granulocyte (CFU-G), and CFU-macrophage (CFU-M). the HA-2-specific CTL clone, however, inhibited BFU-E and CFU-G growth from four donors to a lesser extent than from two other donors. We further investigated whether inhibitory cytokines released into the culture medium by the antigen-specific stimulated CTLs or by stimulated BMMNCs were responsible for suppression of HPC growth or whether this effect was caused by direct cell-cell contact between CTLs and HPCs. HPC growth inhibition was only observed after preincubation of BMMNCs and CTLs together for 4 hours before plating the cells in semisolid HPC culture medium. When no cell-cell contact was permitted before plating, neither antigen-stimulated CTL nor antigen-nonstimulated CTLs provoked HPC growth inhibition. Culturing BMMNCs in the presence of supernatants harvested after incubation of BMMNCs and CTL clones together for 4 or 72 hours did also not result in HPC growth inhibition. Both suppression of HPC growth and lysis of IL-2 blasts and BMMNCs in the 51Cr-release assay appeared to be dependent on direct cell-cell contact between target cells and CTLs and were not caused by the release of inhibitory cytokines into the culture medium by antigen-specific stimulated CTLs or by stimulated BMMNCs. Our results show that mH-antigen-specific CTLs can inhibit HPC growth by a direct cytolytic effect and may therefore be responsible for BM graft rejection after HLA-identical BMT.  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