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   1056篇
  免费   62篇
  国内免费   1篇
耳鼻咽喉   9篇
儿科学   43篇
妇产科学   47篇
基础医学   133篇
口腔科学   19篇
临床医学   113篇
内科学   256篇
皮肤病学   21篇
神经病学   88篇
特种医学   16篇
外科学   88篇
综合类   7篇
一般理论   1篇
预防医学   118篇
眼科学   13篇
药学   64篇
中国医学   1篇
肿瘤学   82篇
  2024年   5篇
  2023年   11篇
  2022年   27篇
  2021年   48篇
  2020年   28篇
  2019年   33篇
  2018年   35篇
  2017年   22篇
  2016年   28篇
  2015年   31篇
  2014年   39篇
  2013年   56篇
  2012年   75篇
  2011年   75篇
  2010年   48篇
  2009年   36篇
  2008年   76篇
  2007年   82篇
  2006年   63篇
  2005年   53篇
  2004年   48篇
  2003年   53篇
  2002年   40篇
  2001年   14篇
  2000年   5篇
  1999年   6篇
  1998年   11篇
  1997年   12篇
  1996年   9篇
  1994年   5篇
  1993年   4篇
  1991年   3篇
  1989年   2篇
  1988年   1篇
  1985年   1篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1974年   2篇
  1973年   3篇
  1972年   7篇
  1971年   2篇
  1969年   4篇
  1968年   2篇
  1966年   3篇
  1964年   1篇
  1963年   1篇
排序方式: 共有1119条查询结果,搜索用时 15 毫秒
51.
52.
Molecular events associated with the initiation and progression of esophageal squamous cell carcinoma (ESCC) remain poorly understood but likely hold the key to effective early detection approaches for this almost invariably fatal cancer. CDC25B and LAMC2 are two promising early detection candidates emerging from new molecular studies of ESCC. To further elucidate the role of these two genes in esophageal carcinogenesis, we did a series of studies to (a) confirm RNA overexpression, (b) establish the prevalence of protein overexpression, (c) relate protein overexpression to survival, and (d) explore their potential as early detection biomarkers. Results of these studies indicated that CDC25B mRNA was overexpressed (>/=2-fold overexpression in tumor compared with normal) in 64% of the 73 ESCC cases evaluated, whereas LAMC2 mRNA was overexpressed in 89% of cases. CDC25B protein expression was categorized as positive in 59% (144 of 243) of ESCC cases on a tumor tissue microarray, and nonnegative LAMC2 patterns of protein expression were observed in 82% (225 of 275) of cases. Multivariate-adjusted proportional hazard regression models showed no association between CDC25B protein expression score and risk of death [hazard ratio (HR) for each unit increase in expression score, 1.00; P = 0.90]; however, several of the LAMC2 protein expression patterns strongly predicted survival. Using the cytoplasmic pattern as the reference (the pattern with the lowest mortality), cases with a diffuse pattern had a 254% increased risk of death (HR, 3.52; P = 0.007), cases with no LAMC2 expression had a 169% increased risk of death (HR, 2.69; P = 0.009), and cases with a peripheral pattern had a 130% greater risk of death (HR, 2.30; P = 0.02). CDC25B protein expression scores in subjects with esophageal biopsies diagnosed as normal (n = 35), dysplastic (n = 23), or ESCC (n = 32) increased significantly with morphologic progression. For LAMC2, all normal and dysplastic patients had a continuous pattern of protein expression, whereas all ESCCs showed alternative, noncontinuous patterns. This series of studies showed that both CDC25B and LAMC2 overexpress RNA and protein in a significant majority of ESCC cases. The strong relation of LAMC2 pattern of protein expression to survival suggests a role in prognosis, whereas the association of CDC25B with morphologic progression indicates a potential role as an early detection marker.  相似文献   
53.
These are case reports of two children with structurally normal hearts and with normal coronary arteries, who survived myocardial infarction in the early neonatal period. They are only the third and fourth reported survivors of neonatal myocardial infarction and the first in which hypercholesterolemia is postulated to have played an important role. The most likely cause of the myocardial infarction was thrombosis or thromboembolism. Changes in hemostatic function associated with hypercholesterolemia may be relevant.  相似文献   
54.
A three-cell, randomized, parallel, investigator-blinded clinical trial was conducted to compare the efficacy and safety of three professional at-home tooth whitening systems, including Crest Professional Whitestrips (6.5% H2O2), Day White 2 (7.5% H2O2) and Nite White Excel 2 (16% carbamide peroxide equivalent). Ninety subjects were randomly assigned to three groups (30/group). Subjects were instructed to use the assigned whitener following the manufacturers' instructions. Clinical examinations at baseline, and on days 3, 7, 14, and 18 (Day White), or 21 (Crest Professional Whitestrips and Nite White) included the following parameters: 1) oral tissues; 2) tooth shade by the Vitapan Classical shade guide; 3) tooth shade by a chromameter with a jig; and, 4) tooth sensitivity and gingival irritation. The results showed significant shade reductions with time in all three groups. Nite White resulted in significantly greater shade reductions in periods between days 7, 14, or 21 and baseline than did the other two systems. Tooth sensitivity and gingival irritation, which were mostly mild and transient, occurred in all groups. It is concluded that all three whitening systems evaluated are effective and safe. Nite White Excel is superior to the other two systems because it provides a greater whitening efficacy with comparable or lower incidence of tooth sensitivity and gingival irritation.  相似文献   
55.

Background

The greater susceptibility of children to renal injury in post-diarrheal hemolytic-uremic syndrome (HUS) may be related, at least in part, to heightened renal cell sensitivity to the cytotoxic effect of Shiga toxin (Stx), the putative mediator of kidney damage in HUS. We hypothesized that sexual maturation, which coincides with a falling incidence of HUS, may induce a relatively Stx-resistant state in the renal cells.

Methods

Cultured human glomerular endothelial (HGEN), human glomerular visceral epithelial (HGEC) and human proximal tubule (HPT) cells were exposed to Stx-1 after pre-incubation with progesterone, β-estradiol or testosterone followed by determination of cytotoxicity.

Results

Under basal conditions, Stx-1 potently and dose-dependently killed HPT and HGEC, but had relatively little effect on HGEN. Pre-incubation for 1, 2 or 7 days with physiologic or pharmacologic concentrations of progesterone, β-estradiol or testosterone had no effect on Stx-1 cytotoxicity dose-response on any cell type. In addition, no steroid altered Gb3 expression (Stx receptor) by any cell type at any time point.

Conclusion

These data do not support the notion that hormonal changes associated with puberty induce an Stx-resistant state within kidney cells.  相似文献   
56.
BACKGROUND: Because topical microbicides designed to prevent the spread of sexually transmitted diseases may be applied frequently, it is important to ensure product safety as well as efficacy. A murine model was developed to test for induction of inflammatory responses following application of candidate microbicides. GOAL: A comparison was made of the induction of inflammation following vaginal application of detergent-based and sulfated polymer-based microbicides. STUDY DESIGN: Vaginal leukocytes were collected, identified, and quantified following microbicide application to detect the entry of inflammatory leukocytes into the vaginal lumen. RESULTS: Large numbers of neutrophils and macrophages entered the vaginal lumen following a single application of detergent-based microbicides. No significant increase in vaginal leukocytes was detected following a single or repeated application of sulfated polymer-based microbicides. CONCLUSION: Application of sulfated polymer-based microbicides was less likely to result in inflammatory responses than was application of detergent-based compounds. This murine model should prove useful as part of a screening process to prioritize candidate microbicides before clinical trial.  相似文献   
57.
BACKGROUND: In 1999, licensed health care facilities in California (N = 2532) were invited to participate in a survey about occupational bloodborne pathogens exposure surveillance activities, recordkeeping methods, and use of safety-enhanced sharps devices. RESULTS: A total of 1274 facilities responded to the survey from January 1999 through August 1999 (response rate = 50%). Sharps-related injuries were recorded for multiple departments on various forms in diverse manners. Only 66% of hospitals, 37% of home health agencies, and 33% of skilled nursing facilities reported sharps injuries on a mandated sharps injury log. More than 70% of facilities stated that they used some type of safety device or needleless system, but this figure varied by type of device and facility type. Eighty-four percent of general acute care hospitals, 28% of home health agencies and skilled nursing facilities each had evaluated at least 1 safety-enhanced device. Almost 90% of all facilities expressed a need for educational materials on topics such as device selection and evaluation. CONCLUSIONS: Standardization of surveillance and recordkeeping activities does not exist across facility types. Standards and regulations demand complex recordkeeping activities. Increased funding for distribution of educational materials and on-site training should accompany changes in mandated reporting activities when appropriate. Increased testing and evaluation of devices across facility types are necessary to ensure that safety-enhanced devices are protective of health care workers and patients.  相似文献   
58.
This article reviews the neuroradiological evaluation of acute head injury with an emphasis on CT and MR imaging. Subacute and chronic head injury are not discussed. CT remains the modality of choice in the emergency setting, permitting rapid, comprehensive assessment of the great majority of head injuries. MR is most useful in patients in whom there is a discrepancy between clinical symptoms and CT findings. In addition, MR is the imaging modality of choice in the subacute and chronic setting. The superior contrast resolution of MR permits optimal evaluation of nonhemorrhagic (and hemorrhagic) white matter shearing injuries, and the lack of beam-hardening artifact permits a more thorough evaluation of the brain stem, posterior fossa, and cortical surface.  相似文献   
59.
We compared two joint likelihood approaches, with complete (L1) or without (L2) linkage disequilibrium, under different ascertainment schemes, for the genetic analysis of the disease trait and marker gene 1 in replicate 42. Joint likelihoods were computed without a correction for the selection scheme. For the different sampling schemes we have explored, our results suggest that L1 is a more powerful approach than L2 to detect major gene and covariatc effects as well as to identify accurately gene×covariate interaction effects in a common and complex disease such as the Genetic Analysis Workshop 12 MG6 simulated trait. © 2001 Wiley‐Liss, Inc.  相似文献   
60.
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