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   3047篇
  免费   145篇
  国内免费   9篇
耳鼻咽喉   19篇
儿科学   97篇
妇产科学   99篇
基础医学   488篇
口腔科学   82篇
临床医学   228篇
内科学   737篇
皮肤病学   81篇
神经病学   162篇
特种医学   33篇
外科学   254篇
综合类   28篇
一般理论   1篇
预防医学   407篇
眼科学   53篇
药学   259篇
中国医学   16篇
肿瘤学   157篇
  2023年   25篇
  2022年   61篇
  2021年   95篇
  2020年   50篇
  2019年   74篇
  2018年   81篇
  2017年   72篇
  2016年   63篇
  2015年   75篇
  2014年   128篇
  2013年   175篇
  2012年   269篇
  2011年   243篇
  2010年   142篇
  2009年   114篇
  2008年   200篇
  2007年   226篇
  2006年   188篇
  2005年   177篇
  2004年   163篇
  2003年   171篇
  2002年   163篇
  2001年   23篇
  2000年   16篇
  1999年   20篇
  1998年   28篇
  1997年   20篇
  1996年   18篇
  1995年   13篇
  1994年   11篇
  1993年   12篇
  1992年   5篇
  1991年   3篇
  1990年   9篇
  1989年   6篇
  1988年   5篇
  1987年   6篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   6篇
  1982年   8篇
  1981年   3篇
  1978年   3篇
  1975年   4篇
  1973年   2篇
  1971年   2篇
  1968年   2篇
  1967年   3篇
  1926年   1篇
排序方式: 共有3201条查询结果,搜索用时 31 毫秒
81.
We developed microsatellite loci for the Julimes pupfish, Cyprinodon julimes. Twenty-five loci were screened across 19 individuals from Julimes Spring, Chihuahua, Mexico. The number of alleles per locus ranged from 2 to 14, observed heterozygosity ranged from 0.105 to 0.947, and the probability of identity values ranged from 0.022 to 0.588. We then tested for cross-amplification in the bighead pupfish, C. pachycephalus; twenty-three individuals from San Diego de Alcalá, Chihuahua, Mexico, were screened across the 20 loci that amplified cleanly. These new loci will be used for long-term genetic monitoring of these critically endangered species.  相似文献   
82.
83.
JAK2V617F-negative essential thrombocythemia (ET) is a heterogeneous disease including clonal cases and others without evidence of clonality. However, it is unknown if the detection of myeloid clonality in JAK2V617F-negative ET patients confers a different clinical outcome than those in whom clonal hematopoiesis cannot be demonstrated. The objective of the present study was to evaluate the clinical significance of clonality assessment in patients with JAK2V617F-negative ET. Clonality investigation including mutational status of MPL, TET2, and ASXL1 genes and human androgen receptor (HUMARA) assay was performed in 73 JAK2V617F-negative cases out of 186 subjects consecutively diagnosed with ET in a single institution, at diagnosis or during follow-up. Mutations in MPL, TET2, and ASXL1 were observed in 7, 4, and 2 cases, respectively, whereas clonality by HUMARA assay was demonstrated in 21 out of 46 (46?%) female patients. With a median follow-up of 8?years, death, thrombosis, bleeding, and disease transformation were registered in 7, 10, 8, and 6 patients, respectively. No differences in thrombosis, bleeding or survival were observed according to clonality assessment. The probability of disease transformation at 10?years was higher in patients showing clonal hematopoiesis by presenting mutations in either MPL, TET2, or ASXL1 (64 versus 2?% in patients without mutations, p?相似文献   
84.
85.
86.
ABSTRACT: BACKGROUND: HTLV-1 is associated with increased susceptibility to Mycobacterium tuberculosis infection and severity of tuberculosis. Although previous studies have shown that HTLV-1 infected individuals have a low frequency of positive tuberculin skin test (TST) and decreasing in lymphoproliferative responses compared to HTLV-1 uninfected persons, these studies were not performed in individuals with history of tuberculosis or evidence of M. tuberculosis infection. Therefore the reasons why HTLV-1 infection increases susceptibility to infection and severity of tuberculosis are not understood.The aim of this study was to evaluate how HTLV-1 may influence the clinical, bacteriologic and immunologic presentation of tuberculosis. METHODS: The study prospectively enrolled and followed 13 new cases of tuberculosis associated with HTLV-1 (cases) and 25 patients with tuberculosis without HTLV-1 infection (controls). Clinical findings, bacterial load in the sputum, x-rays, immunological response and death were compared in the two groups. RESULTS: There were no differences in the demographic, clinical and TST response between the two study groups. IFN-gamma and TNF-alpha production was higher in unstimulated cultures of mononuclear cells of case than in control patients (p < 0.01). While there was no difference in IFN-gamma production in PPD stimulated cultures, TNF-alpha levels were lower in cases than in controls (p = 0.01). There was no difference in the bacterial load among the groups but sputum smear microscopy results became negative faster in cases than in controls. Death only occurred in two co-infected patients. CONCLUSION: While the increased susceptibility for tuberculosis infection in HTLV-1 infected subjects may be related to impairment in TNF-alpha production, the severity of tuberculosis in co-infected patients may be due to the enhancement of the Th1 inflammatory response, rather than in their decreased ability to control bacterial growth.  相似文献   
87.
88.

This longitudinal study aims to define the developmental trajectories of social cognition (SC) in a community sample (N = 378) assessed from preschool (3 years old) to preadolescence (12 years old). Parents and teachers reported on a SC measure at ages 5, 10, and 12. We tested the existence of different trajectories and whether they discriminated outcomes in early adolescence. The data were collected from different sources, the children, the parents, and teachers, by means of different methods. Using Growth Mixture Modeling (GMM), we identified three distinct social cognition trajectories: persistently mild difficulties reported by parents and teachers (7.9% of the children), stable low problems reported by parents and increased difficulties reported by teachers (10.5% of the sample), and stable low problems reported by both informants for most of the participants (81.5%). Comparison of the psychological outcomes between classes using regression models showed that the two trajectories including children with any level of problems differ from the normative one as regards their association with psychological problems, daily functioning, and variables, such as aggressive behavior and callousness. The two non-normative trajectories also differ from each other in terms of the personal characteristics of the adolescents included in them. Adolescents in the increasing problematic class in the school have a tougher and more problematic style of social relating, while children with persistent and non-context-dependent difficulties are more anxious. These results might help to better detect and design specific interventions for children with deficits in SC that might respond to different personal characteristics leading to different outcomes.

  相似文献   
89.
Several materials are commercially available as substitutes for skin. However, new strategies are needed to improve the treatment of skin wounds. In this study, we developed and characterized a new device consisting of poly(lactic‐co‐glycolic acid) (PLGA) and collagen associated with mesenchymal stem cells derived from human adipose tissue. To develop the bilaminar device, we initially obtained a membrane of PLGA by dissolving the copolymer in chloroform and then produced a collagen type I scaffold by freeze‐drying. The materials were characterized physically by gel permeation chromatography, scanning electron microscopy, and mass loss. Biological activity was assessed by cell proliferation assay. A preliminary study in vivo was performed with a pig model in which tissue regeneration was assessed macroscopically and histologically, the commercial device Integra being used as a control. The PLGA/collagen bilaminar material was porous, hydrolytically degradable, and compatible with skin growth. The polymer complex allowed cell adhesion and proliferation, making it a potentially useful cell carrier. In addition, the transparency of the material allowed monitoring of the lesion when the dressings were changed. Xenogeneic mesenchymal cells cultured on the device (PLGA/collagen/ASC) showed a reduced granulomatous reaction to bovine collagen, down‐regulation of α‐SMA, enhancement in the number of neoformed blood vessels, and collagen organization as compared with normal skin; the device was superior to other materials tested (PLGA/collagen and Integra) in its ability to stimulate the formation of new cutaneous tissue.  相似文献   
90.
The aim of the study is to demonstrate the successful use of “Hour 1” transfer of sperm microinjected oocytes in natural cycles of poor responder women. Seventy women were selected from 92 consecutive poor responders undergoing intracytoplasmatic sperm injection (ICSI) in a natural cycle at our Sterility and Assisted Reproduction Unit from September 2009 to July 2013, and randomly distributed in two homogeneous groups: Group A or B. Women in Group A (35) underwent transfer within 1 h after ICSI; Group B (35, control group) underwent transfer 3 days after ICSI. In Group A, seven clinical pregnancy and one miscarriage occurred; in Group B, eight clinical pregnancies and two miscarriages were observed. Pregnancy, miscarriage, term pregnancy and overall live birth rates’ difference between the two groups was not statistically significant (p?>?0.05). Difference between the two groups in terms of timing, type of delivery and newborn birthweight was not observed. Neither ectopic pregnancy nor multiple pregnancies occurred. “Hour 1” uterine transfer of ICSI oocytes, still to be considered with caution because of the relatively low number of observations of the pilot study, deserves further attention on a larger scale, and might be evaluated for clinical and financial effectiveness in other clinical settings.  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