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   4786篇
  免费   295篇
  国内免费   29篇
耳鼻咽喉   44篇
儿科学   144篇
妇产科学   131篇
基础医学   821篇
口腔科学   78篇
临床医学   483篇
内科学   894篇
皮肤病学   159篇
神经病学   552篇
特种医学   206篇
外科学   341篇
综合类   52篇
一般理论   3篇
预防医学   352篇
眼科学   73篇
药学   406篇
中国医学   43篇
肿瘤学   328篇
  2023年   44篇
  2022年   120篇
  2021年   210篇
  2020年   107篇
  2019年   166篇
  2018年   148篇
  2017年   108篇
  2016年   155篇
  2015年   148篇
  2014年   215篇
  2013年   253篇
  2012年   431篇
  2011年   453篇
  2010年   259篇
  2009年   181篇
  2008年   344篇
  2007年   318篇
  2006年   275篇
  2005年   241篇
  2004年   204篇
  2003年   172篇
  2002年   158篇
  2001年   34篇
  2000年   21篇
  1999年   41篇
  1998年   37篇
  1997年   33篇
  1996年   22篇
  1995年   17篇
  1994年   19篇
  1993年   12篇
  1992年   7篇
  1991年   7篇
  1990年   7篇
  1989年   7篇
  1988年   9篇
  1987年   9篇
  1986年   5篇
  1985年   7篇
  1984年   7篇
  1983年   8篇
  1982年   8篇
  1981年   11篇
  1980年   13篇
  1979年   6篇
  1978年   9篇
  1977年   9篇
  1976年   5篇
  1975年   7篇
  1974年   5篇
排序方式: 共有5110条查询结果,搜索用时 15 毫秒
31.
We report a case of Takayasu's disease with severe renovascular hypertension in a girl from Eritrea. In the "burn-out" phase after the erythrocyte sedimentation rate had normalized, reconstructive vascular surgery was performed as further progression of the disease seemed unlikely. However, probably due to her growth, the graft rotated and a second operation was successfully performed.  相似文献   
32.
BACKGROUND: An important concern for developers of clinical practice guidelines is how best to determine when guidelines require updating to ensure they remain current and evidence based. Because of the high costs associated with updating guidelines, recent attention has focused on approaches that can reliably assess the extent of updating required. Recently, Shekelle and colleagues proposed a model of limited literature searches with modest expert involvement as a way to reduce the cost and time requirements for assessing whether a guideline needs updating. METHODS: The main objective of this study was to compare the Shekelle et al. assessment model (review approach) and a conventional process using typical systematic review methods (traditional approach) in terms of comprehensiveness and effort. We modeled the review approach on that by Shekelle and colleagues but refined it iteratively over three phases to achieve greater efficiency. Using both methods independently, we assessed the need to update six topics from the 1996 Guide to Clinical Preventive Services from the US Preventive Services Task Force. Main outcomes included completeness of study identification, importance of missed studies and the effort involved. RESULTS: Although the review approach identified fewer eligible studies than the traditional approach, none of the studies missed was rated as important by task force members acting as liaisons to the project with respect to whether the topic required an update. On average, the review approach produced substantially fewer citations to review than the traditional approach. The effort involved and potential time saving depended largely on the scope of the topic. CONCLUSIONS: The revised review approach provides an efficient and acceptable method for judging whether a guideline requires updating.  相似文献   
33.
In order to investigate the ameliorative potential of L-ascorbic acid on intensive swimming exercise induced testicular oxidative stress, 18 Wistar male rats (age: 3 months, weight: 127.5 ± 5.3 g) were randomly divided into the following groups: (i) control group (CG,n = 6); (ii) experimental group (EG,n = 6); and (iii) supplemented group (SG,n = 6). An exercise protocol of 3 h swimming per day, five days per week was followed for 6 weeks in EG and SG with no exercise in CG. In SG, L-ascorbic acid was supplied orally at a dose of 25-mg/kg of bodyweight each day for 6 weeks. A significant decrease (P < 0.05) was noted in paired testicular weights, epididymal sperm count, testicular Δ5, 3β-hydroxyseroid dehydrogenase, 17β-hydroxyseroid dehydrogenase, plasma levels of testosterone luteinizing hormone, follicle stimulating hormone, prolactin, the numbers of preleptotine spermatocytes, midpachytene spermatocytes and stage 7 spermatids of stage VII seminiferous epithelium cycle in EG when compared with CG. A significant elevation (P < 0.05) in plasma corticosterone and testicular content of malondialdehyde along with a significant reduction (P < 0.05) in glutathione, ascorbic acid, α-tocopherol, superoxide dismutase, catalase and glutathione-peroxidase, and glutathione-S-transferase were noted in testes of EG compared with CG. No significant change was noted in final bodyweight or numbers of spermatogonia-A among the groups. Furthermore, L-ascorbic acid supplementation restored the above parameters to the control level. Conclusion  It can be concluded that intensive swimming exercise induced oxidative stress causes dysfunctions in the male reproductive system, which can be protected by L-ascorbic acid.  相似文献   
34.
35.
The development of cost-effective co-catalysts of high photocatalytic activity and recyclability is still a challenge in the energy transformation domain. In this study, 0D/2D Schottky heterojunctions, consisting of 0D ZnO and 2D Ti3C2, were successfully synthesized by the electrostatic self-assembling of ZnO nanoparticles on Ti3C2 nanosheets. In constructing these heterojunctions, Ti3C2 nanosheets acted as a co-catalyst for enhancing the transfer of excitons and their separation to support the photocatalytic response of ZnO. The as-prepared ZnO/Ti3C2 composites demonstrate an abbreviated charge transit channel, a huge interfacial contact area and the interfacial electrons’ transport potential. The extended optical response and large reactive area of the ZnO/Ti3C2 composite promoted the formation of excitons and reactive sites on the photocatalyst’s surface. The ZnO/Ti3C2 Schottky heterojunction showed significantly high photocatalytic activity for hydrogen production from a water–ethanol solution under the light illumination in the visible region. The hydrogen evolution overoptimized the ZnO/Ti3C2 composition with 30 wt.% of Ti3C2, which was eight times higher than the pristine ZnO. These findings can be helpful in developing 0D/2D heterojunction systems for photocatalytic applications by utilizing Ti3C2 as a low-cost co-catalyst.  相似文献   
36.
Advances in high-throughput sequencing methods have boosted the discovery of multistrain viral infections in diverse plant systems. This phenomenon appears to be pervasive for certain viral species. However, our knowledge of the transmission aspects leading to the establishment of such mixed infections is limited. Recently, we reported a mixed infection of a single strawberry plant with strawberry mottle virus (SMoV), strawberry crinkle virus (SCV) and strawberry virus 1 (StrV-1). While SCV and StrV-1 are represented by two and three molecular variants, respectively, SmoV has three different RNA1 and RNA2 segments. In this study, we focus on virus acquisition by individual adult aphids of the Aphis gossypii, Aphis forbesi and Chaetosiphon fragaefolii species. Single-aphid transmission trials are performed under experimental conditions. Both different viruses and individual virus strains show varying performances in single aphid acquisition. The obtained data suggests that numerous individual transmission events lead to the establishment of multistrain infections. These data will be important for the development of epidemiological models in plant virology.  相似文献   
37.
A fuzzy model has been developed for the optimization of high-shear wet granulation wetting on a plant scale depending on the characteristics of pharmaceutical active substance particles. The model optimized on the basis of experimental data involves a set of rules obtained from expert knowledge and full-scale process data. The skewness coefficient of particle size distribution and the tapped density of the granulated mixture were chosen as the model input variables. The output of the fuzzy ruled system is the optimal quantity of wetting liquid. In comparison to manufacturing practice, a very strong sensitivity of the optimal quantity of the added wetting liquid to the size and shape of the active substance particles has been identified by fuzzy modeling.  相似文献   
38.
OBJECTIVES: Evaluation of the complications rate, as well as pregnancy outcome, in women who underwent early and mid-trimester amniocentesis. MATERIAL AND METHODS: The study was conducted among 454 patients, including 162 women after the procedure performed before 15 gestational week and 292 patients who underwent classic amniocentesis. All patients were hospitalized in Division of Reproduction of University of Medical Sciences in Poznan between 1999 and 2005. The analysis, based both on clinical observations and questionnaire sent to patients, concerned especially the frequency of following complications: miscarriage, premature rupture of membranes and club foot in newborns. RESULTS: Total pregnancy loss rate due to amniocentesis amounted to 1.2% and 0.3% in early and mid-trimester amniocentesis, respectively, not reaching statistical significance. The frequency of club foot in newborns of mothers who underwent amniocentesis did not differ significantly between the groups, although it was four times higher in early amniocentesis group than in patients in whom mid-trimester amniocentesis had been performed. CONCLUSIONS: The safety of early amniocentesis is comparable with safety of mid-trimester amniocentesis.  相似文献   
39.
In acute myeloid leukemia, there is an ongoing debate on the prognostic value of the early bone marrow assessment in patients receiving intensive therapy. In this retrospective study, we analyzed the prognostic impact of the early response in 1,008 patients with newly diagnosed acute myeloid leukemia, who were treated at our institution with intensive chemotherapy followed by consolidation chemotherapy and/or allogeneic hematopoietic stem cell transplantation (HSCT). We found that early blast persistence has an independent negative prognostic impact on overall survival, event-free survival and relapse-free survival. This negative prognostic impact may only be overcome in patients showing at least a partial remission at the early bone marrow assessment and who subsequently achieve blast clearance by additional induction chemotherapy prior to consolidation therapy with allogeneic HSCT. In accordance, we propose that the time slope of remission is an additional leukemia-related dynamic parameter that reflects chemosensitivity and thus may inform post-induction therapy decision-making. In addition to patient-related factors, European LeukemiaNet risk group, measurable residual disease monitoring and donor availability, this may particularly apply to European LeukemiaNet intermediate-risk patients, for whom a decision between consolidation chemotherapy and allogeneic HSCT remains challenging in many cases.  相似文献   
40.
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