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   9008篇
  免费   621篇
  国内免费   64篇
耳鼻咽喉   62篇
儿科学   220篇
妇产科学   192篇
基础医学   1572篇
口腔科学   121篇
临床医学   887篇
内科学   2300篇
皮肤病学   126篇
神经病学   808篇
特种医学   177篇
外科学   707篇
综合类   41篇
一般理论   1篇
预防医学   790篇
眼科学   131篇
药学   767篇
中国医学   28篇
肿瘤学   763篇
  2024年   11篇
  2023年   117篇
  2022年   264篇
  2021年   402篇
  2020年   208篇
  2019年   279篇
  2018年   327篇
  2017年   235篇
  2016年   226篇
  2015年   319篇
  2014年   357篇
  2013年   506篇
  2012年   718篇
  2011年   723篇
  2010年   392篇
  2009年   368篇
  2008年   613篇
  2007年   654篇
  2006年   584篇
  2005年   534篇
  2004年   437篇
  2003年   436篇
  2002年   392篇
  2001年   23篇
  2000年   37篇
  1999年   49篇
  1998年   72篇
  1997年   52篇
  1996年   35篇
  1995年   23篇
  1994年   11篇
  1993年   16篇
  1992年   10篇
  1991年   10篇
  1989年   8篇
  1988年   8篇
  1987年   11篇
  1986年   10篇
  1985年   16篇
  1984年   11篇
  1982年   7篇
  1981年   22篇
  1980年   10篇
  1978年   12篇
  1977年   13篇
  1976年   8篇
  1975年   8篇
  1974年   7篇
  1971年   6篇
  1966年   6篇
排序方式: 共有9693条查询结果,搜索用时 15 毫秒
101.
Isolated GH deficiency (IGHD) is characterized by genetic heterogeneity, both in familial and sporadic cases. To determine if this statement can be applied to the Russian population, we performed screening for mutations in the GH-1 gene in children living in Russia with IGHD. Twenty-eight children from 26 families with total IGHD were studied. DNA fragments, covering each of four (2-5) exons of GH-1 were amplified using PCR. Single-strand conformation polymorphism analysis followed by direct DNA sequencing identified five heterozygous mutations of splicing in intron 2, intron 3, and exon 4 of GH-1; three of them were not previously reported. We concentrated here on dominant-negative mutations causing IGHD type II, which were as follows: 1) A>T transversion of the second base of the 3'-acceptor splice site of intron 2 (IVS2 -2A>T); 2) T>C transition of the second base of the 5'-donor splice site of intron 3 (IVS3 +2T>C); 3) G>A transition of the first base of the 5'-donor splice site of intron 3 (IVS3 +1G>A). Our data indicate allelic heterogeneity of IGHD type II (IGHD II). However, all mutations in Russian IGHD II patients affect splicing, a striking difference from the mutation spectrum of other IGHD forms. The IVS2 -2A>T mutation is the first identified mutation in intron 2 of GH-1. The 5'-donor splice site of intron 3 of GH-1 is a mutational hot spot, and the IVS3 +1G>A mutation can be considered to be a common molecular defect in IGHD II in Russian patients.  相似文献   
102.
OBJECTIVE: Plasticity of hematopoietic stem cells (HSC) has gained major interest in stem cell research. In order to investigate whether HSC may differentiate into mesenchymal stem cells (MSC), we assessed chimerism in peripheral blood (PB), mononuclear cell fractions (MNC) of bone marrow, and MSC derived from bone marrow (BM) from 27 up to 4225 days after allogeneic transplantation. PATIENTS AND METHODS: We applied fluorescence in situ hybridization using X/Y gene probes in sex-mismatched and STR-PCR in sex-matched patients. MSC could have been generated in 27 of 55 bone marrow samples derived from 20 patients. Fifteen patients received peripheral blood stem cell transplants (PBSCT), including CD34-selected PBSCT in two. Five patients received bone marrow. RESULTS: While all patients had chimerism in PB and MNC of the BM, in all but one patient BM-derived MSC were of recipient origin. This single patient showed reproducibly MSC of donor origin in a frequency of 1% after having received a CD34-selected PBSCT. Looking at graft collections, MSCs were easily generated from BM specimens, while no MSC could be derived from PBSC samples. CONCLUSION: Even though HSC have been found to differentiate into a variety of nonhematological cell types, they usually do not differentiate into MSC after allogeneic transplantation.  相似文献   
103.
Maciejewski JP  Sloand EM  Nunez O  Boss C  Young NS 《Blood》2003,102(10):3584-3586
In contrast to severe aplastic anemia (sAA), the appropriate management of patients with moderate pancytopenia is unclear. In this study, we examined the efficacy of a humanized monoclonal antibody recognizing interleukin-2 receptor (daclizumab), which has proven to be a successful immunosuppressive agent in solid organ and bone marrow transplantation. We treated 17 patients with moderate aplastic anemia (mAA) with 1 mg/kg every 2 weeks for 3 months. mAA was defined as depression of 2 of the 3 blood counts: absolute neutrophil count 1200/mm3 or less, platelet count 70,000/mm3 or less, hemoglobin level 8.5 g/dL or lower, and absolute reticulocyte count 60,000/mm3 or less. The primary end point of our protocol was a hematologic response in at least one affected peripheral blood value. Daclizumab had little toxicity. Six of the 16 (38%) evaluable patients responded to treatment. Two patients with previously chronic disease showed complete return of normal counts, which were sustained for more than 2 years following treatment. Four patients had single-lineage responses. Two previously transfusion-dependent patients became transfusion independent; one patient with many neutropenia-related infections had a normal neutrophil count following treatment. Daclizumab appears safe; its efficacy in this pilot protocol suggests that expanded study of this monoclonal antibody in immune-mediated bone marrow failure syndrome is warranted.  相似文献   
104.
N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide (PNPr), i.e., the monomer with a terminal ethynyl group and 1,8‐naphthalimide fluorophore, has been successfully copolymerized with a series of monoethynylarenes into well‐soluble high‐molecular‐weight (Mw up to 210 000) linear polyacetylene‐type copolymers containing from 14 to 51 mol% units derived from PNPr. The copolymerization of PNPr with bifunctional 4,4′‐diethynylbiphenyl provides polyacetylene‐type micro/mesoporous fluorescent network containing 8 mol% PNPr units and exhibiting the Brunauer–Emmett–Teller surface of ≈1000 m2 g?1. The copolymerizations (catalyzed with acetylacetonato(norborna‐2,5‐diene)rhodium complex, [Rh(nbd)acac]) proceed smoothly despite the fact that the homopolymerization of PNPr fails. The fluorescence of PNPr (emission at ≈ 510 nm) has been retained after the incorporation of PNPr into the copolymers. The fluorescence of the copolymers can be induced by a direct excitation of PNPr units or via an energy transfer mechanism. In the latter case, the comonomeric units with aromatic hydrocarbon fluorophores (e.g., of the biphenyl‐type) emitting at 380–400 nm (after irradiation with 300 nm UV radiation) serve as energy donors for fluorescent PNPr acceptors. The difference between the wavelengths of the primary absorbed radiation and the finally emitted radiation is 210 nm.

  相似文献   

105.

Objective

To determine and compare specific factors that could be associated and predictive with successful prosthetic rehabilitation in major lower-limb amputations.

Methods

A 15-year long (2000–2014) retrospective observational cohort study was conducted. Two different criteria were used to define successful prosthetic rehabilitation: (1) the ability to walk at least 45 m, regardless of assistive devices; and (2) walking >45 m without other ambulatory aids than one cane (if required). Age, gender, comorbidities, cause and level of amputation, stump characteristics, ulcers in the preserved limb, and time between surgery and physical therapy were examined as predictors of successful prosthetic rehabilitation.

Results

A total of 169 patients (61.60 ± 15.9 years) were included. Regarding walking ability with or without walking aids, the presence of ulcers in the preserved limb was individually associated with failed prosthetic rehabilitation (p < 0.001), while being male (OR = 0.21; 95%CI = 0.06–0.80) and transtibial level of amputation (OR = 6.73; 95%CI = 1.92–23.64) were identified as independent predictors of failure and success, respectively. Regarding the criterion of successful rehabilitation, a shorter time until rehabilitation was individually associated with improved walking ability (p < 0.013), while failure could be predicted by comorbidities (OR = 0.48; 95%CI = 0.29–0.78) and age groups of 65–75 years old (OR = 0.19; 95%CI = 0.05–0.78) and over 75 years old (OR = 0.19; 95%CI = 0.04–0.91).

Conclusions

Regarding walking ability with or without walking aids, male gender and transtibial level of amputation are independently associated with failure and success respectively, whereas older age and comorbidities can predict failed prosthetic rehabilitation when assistive walking devices are considered. Future prospective cohort studies are needed to confirm these findings.  相似文献   
106.
107.
To access the calibration of a predictive model in a survival analysis setting, several authors have extended the Hosmer–Lemeshow goodness‐of‐fit test to survival data. Grønnesby and Borgan developed a test under the proportional hazards assumption, and Nam and D'Agostino developed a nonparametric test that is applicable in a more general survival setting for data with limited censoring. We analyze the performance of the two tests and show that the Grønnesby–Borgan test attains appropriate size in a variety of settings, whereas the Nam‐D'Agostino method has a higher than nominal Type 1 error when there is more than trivial censoring. Both tests are sensitive to small cell sizes. We develop a modification of the Nam‐D'Agostino test to allow for higher censoring rates. We show that this modified Nam‐D'Agostino test has appropriate control of Type 1 error and comparable power to the Grønnesby–Borgan test and is applicable to settings other than proportional hazards. We also discuss the application to small cell sizes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
108.
109.
We show the long‐term efficacy and safety of modified biliopancreatic diversion for the treatment of LPL‐deficiency. How this option compares with gene therapy is difficult to evaluate due to limited experience. Surgery may be the first option in patients in whom medical therapy is ineffective and gene therapy not applicable.  相似文献   
110.
A ventricular septal aneurysm is a rare heart defect located in the muscular or membranous part of the septum. Muscular ventricular septal aneurysms are usually isolated, with a favorable prognosis. Membranous ventricular septal aneurysms are often associated with other heart anomalies, could result in serious complications, and may require surgical treatment. We describe 2 cases of prenatally diagnosed ventricular septal aneurysms: an isolated membranous ventricular septal aneurysm with a good outcome, which was initially misdiagnosed as an atrioventricular septal defect; and a muscular ventricular septal aneurysm associated with a hypoplastic aortic arch and severe hydrocephaly, which resulted in termination of the pregnancy. To our knowledge, the combination of a muscular ventricular septal aneurysm with an extracardiac anomaly has not been reported previously.  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