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   2195篇
  免费   185篇
  国内免费   6篇
耳鼻咽喉   24篇
儿科学   88篇
妇产科学   33篇
基础医学   343篇
口腔科学   66篇
临床医学   213篇
内科学   347篇
皮肤病学   20篇
神经病学   231篇
特种医学   192篇
外科学   243篇
综合类   82篇
一般理论   2篇
预防医学   251篇
眼科学   38篇
药学   125篇
中国医学   4篇
肿瘤学   84篇
  2022年   20篇
  2021年   30篇
  2020年   23篇
  2018年   36篇
  2017年   30篇
  2016年   33篇
  2015年   38篇
  2014年   46篇
  2013年   60篇
  2012年   100篇
  2011年   109篇
  2010年   91篇
  2009年   56篇
  2008年   83篇
  2007年   62篇
  2006年   79篇
  2005年   85篇
  2004年   72篇
  2003年   49篇
  2002年   68篇
  2001年   65篇
  2000年   62篇
  1999年   52篇
  1998年   48篇
  1997年   41篇
  1996年   36篇
  1995年   27篇
  1994年   31篇
  1993年   24篇
  1992年   45篇
  1991年   37篇
  1990年   38篇
  1989年   55篇
  1988年   53篇
  1987年   65篇
  1986年   55篇
  1985年   38篇
  1984年   29篇
  1983年   34篇
  1982年   22篇
  1981年   19篇
  1980年   18篇
  1979年   45篇
  1978年   17篇
  1976年   21篇
  1975年   18篇
  1974年   17篇
  1973年   25篇
  1969年   16篇
  1966年   19篇
排序方式: 共有2386条查询结果,搜索用时 31 毫秒
61.
Journal of Thrombosis and Thrombolysis - The optimal management strategy for submassive or intermediate risk pulmonary embolism (IRPE)—anticoagulation alone versus anticoagulation plus...  相似文献   
62.
The transient nature of the internal pore structure of particulate wall flow filters, caused by the continuous deposition of particulate matter, makes studying their flow and filtration characteristics challenging. In this article we present a new methodology and first experimental demonstration of time resolved in-situ synchrotron micro X-ray computed tomography (micro-CT) to study aerosol filtration. We directly imaged in 4D (3D plus time) pore scale deposits of TiO2 nanoparticles (nominal mean primary diameter of 25 nm) with a pixel resolution of 1.6 μm. We obtained 3D tomograms at a rate of ∼1 per minute. The combined spatial and temporal resolution allows us to observe pore blocking and filling phenomena as they occur in the filter’s pore space. We quantified the reduction in filter porosity over time, from an initial porosity of 0.60 to a final porosity of 0.56 after 20 min. Furthermore, the penetration depth of particulate deposits and filtration rate was quantified. This novel image-based method offers valuable and statistically relevant insights into how the pore structure and function evolves during particulate filtration. Our data set will allow validation of simulations of automotive wall flow filters. Evolutions of this experimental design have potential for the study of a wide range of dry aerosol filters and could be directly applied to catalysed automotive wall flow filters.  相似文献   
63.
Angiotensin II receptors and prolactin release in pituitary lactotrophs   总被引:6,自引:0,他引:6  
G Aguilera  C L Hyde  K J Catt 《Endocrinology》1982,111(4):1045-1050
Logical properties of angiotensin II receptors in the rat adenohypophysis were analyzed in cultured rat pituitary cells incubated with angiotensin II and known stimuli of pituitary hormone secretion. PRL release during incubation for 3 h with 3 nM angiotensin II was consistently increased by 68 +/- 5%, comparable with that elicited by TRH (63.1 +/- 4%). The ED50 of 0.5 nM for PRL release by angiotensin II was significantly lower than that of TRH (2.9 nM) in the same cell cultures. The antagonist analog [Sar1,Ala8]angiotensin II prevented the angiotensin-induced rise in PRL production but not that evoked by TRH, whereas dopamine and SRIF inhibited basal, angiotensin, and TRH-stimulated PRL release. Angiotensin II also caused a small increase in ACTH release but had no effect on the release of LH, TSH, and GH. Angiotensin II binding and PRL release were measured in partially purified lactotrophs prepared by elutriation, by which the initial cell suspension was separated into seven fractions. Most of the lactotrophs were present in the two fractions eluted at flow rates of 15.7 and 19.8 ml/min, as indicated by their immunoreactive PRL content. The 2.5- to 3.2-fold enrichment of lactotrophs was accompanied by a 2- to 3.5-fold increase in angiotensin II receptor concentration, with no change in binding affinity (Ka = 3.5 x 10(9) M-1). In the same fractions, angiotensin II-induced PRL release was similarly increased by 1.6- to 3.5-fold above basal, compared with values of less than 1 in the initial cell suspension and other fractions. The preferential location of angiotensin II receptors in the lactotroph-containing fractions and the close correlation between angiotensin II binding sites and stimulation of PRL release indicate the functional importance of the pituitary angiotensin II receptor sites. These findings also suggest that angiotensin II could contribute to the physiological regulation of PRL secretion.  相似文献   
64.
ObjectivesThe aim of this study was to assess 1-year clinical outcomes among high-risk patients with failed surgical mitral bioprostheses who underwent transseptal mitral valve-in-valve (MViV) with the SAPIEN 3 aortic transcatheter heart valve (THV) in the MITRAL (Mitral Implantation of Transcatheter Valves) trial.BackgroundThe MITRAL trial is the first prospective study evaluating transseptal MViV with the SAPIEN 3 aortic THV in high-risk patients with failed surgical mitral bioprostheses.MethodsHigh-risk patients with symptomatic moderate to severe or severe mitral regurgitation (MR) or severe mitral stenosis due to failed surgical mitral bioprostheses were prospectively enrolled. The primary safety endpoint was technical success. The primary THV performance endpoint was absence of MR grade ≥2+ or mean mitral valve gradient ≥10 mm Hg (30 days and 1 year). Secondary endpoints included procedural success and all-cause mortality (30 days and 1 year).ResultsThirty patients were enrolled between July 2016 and October 2017 (median age 77.5 years [interquartile range (IQR): 70.3 to 82.8 years], 63.3% women, median Society of Thoracic Surgeons score 9.4% [IQR: 5.8% to 12.0%], 80% in New York Heart Association functional class III or IV). The technical success rate was 100%. The primary performance endpoint in survivors was achieved in 96.6% (28 of 29) at 30 days and 82.8% (24 of 29) at 1 year. Thirty-day all-cause mortality was 3.3% and was unchanged at 1 year. The only death was due to airway obstruction after swallowing several pills simultaneously 29 days post-MViV. At 1-year follow-up, 89.3% of patients were in New York Heart Association functional class I or II, the median mean mitral valve gradient was 6.6 mm Hg (interquartile range: 5.5 to 8.9 mm Hg), and all patients had MR grade ≤1+.ConclusionsTransseptal MViV in high-risk patients was associated with 100% technical success, low procedural complication rates, and very low mortality at 1 year. The vast majority of patients experienced significant symptom alleviation, and THV performance remained stable at 1 year.  相似文献   
65.
Leonard  JP; Quinto  CM; Kozitza  MK; Neben  TY; Goldman  SJ 《Blood》1994,83(6):1499-1506
Interleukin-11 (IL-11) is a novel multifunctional hematopoietic cytokine capable of stimulating cells of the myeloid, lymphoid, erythroid, and megakaryocytic lineages in vitro. We have tested the pleiotropic properties of this cytokine on the hematopoietic recovery of mice after a combined regimen of sublethal irradiation and carboplatin administration. This regimen results in severe myelosuppression, characterized by a prolonged period of thrombocytopenia and severe anemia. Administration of recombinant human IL-11 (rhIL-11; 250 micrograms/kg/d) had multilineage effects on bone marrow and spleen hematopoietic activity, increasing the number of megakaryocyte, erythroid, granulocyte, and macrophage progenitors compared with the vehicle-treated controls. This was reflected in the peripheral circulation by a reduction of both the platelet and hematocrit nadirs and a significantly reduced period of thrombocytopenia and anemia in the rhIL-11-treated mice. The results from this study support the broad spectrum of biologic activities that have been attributed to rhIL-11 in vitro and suggest that this cytokine may be an effective agent in the treatment of myelosuppression associated with cancer chemotherapy and bone marrow transplantation.  相似文献   
66.
Porter  CD; Parkar  MH; Levinsky  RJ; Collins  MK; Kinnon  C 《Blood》1993,82(7):2196-2202
Chronic granulomatous disease (CGD) is an inherited immunodeficiency resulting from the inability of an individual's phagocytes to produce superoxide anions because of defective NADPH oxidase. The disease may be treated by bone marrow transplantation and as such is a candidate for somatic gene therapy. Two thirds of patients have defects in an X- linked gene (X-CGD) encoding gp91-phox, the large subunit of the membrane cytochrome b-245 component of NADPH oxidase. Epstein-Barr virus-transformed B-cell lines from patients with CGD provide a model system for the disease. We have used retrovirus-mediated expression of gp91-phox to reconstitute functionally NADPH oxidase activity in B-cell lines from three unrelated patients with X-CGD. The protein is glycosylated and membrane associated, and the reconstituted oxidase is appropriately activated via protein kinase C. The kinetics of superoxide production by such reconstituted cells is similar to that of normal B-cell lines. These data show the potential of gene therapy for this disease.  相似文献   
67.
68.
The posterior pituitary contains a PRL-releasing factor (PRF), a small (less than 5000 mol wt) peptide which is distinct from known PRL secretagogues. The objectives of this study were to determine if posterior pituitary extracts specifically stimulate PRL release in vivo and to assess the relative contributions of oxytocin (OT), arginine vasopressin (AVP), and beta-endorphin (beta END) to the PRF activity of the extract. Rat posterior pituitaries or cerebellar tissue were extracted with 1.0 N acetic acid, boiled, and ultrafiltered through 5000 mol wt cutoff membranes. The eluates were treated with performic acid (which oxidizes disulfide bonds and methionine residues), lyophilized, and reconstituted in saline. Jugular blood was collected from conscious ovariectomized rats before and after intracarotid injection of test substances and was analyzed for PRL, LH, and GH by RIA. Injection of 0.3, 1.0, and 3.0, posterior pituitary equivalents increased plasma PRL levels by 2-, 8-, and 22-fold, respectively. PRL levels peaked within 5 min after the injection and returned to basal levels by 30 min. Plasma LH levels decreased slightly, and GH was unchanged. Cerebellar extracts did not affect plasma hormone levels. Injection of OT induced a 4-fold rise in plasma PRL levels. Oxidation of OT was well as AVP with performic acid abolished any PRL-releasing activity. Injection of beta END increased plasma PRL levels by 7-fold. Treatment of beta END with performic acid caused a 60% loss in its ability to release PRL. Pretreatment of rats with naloxone abolished the PRL-releasing effect of beta END, but did not alter the PRF activity of posterior pituitary extracts. We conclude that posterior pituitary extracts stimulate PRL release in vivo in the presence of an intact dopaminergic inhibition. This stimulation is rapid, dose dependent, and hormone specific. OT, AVP, and beta END do not contribute significantly to the PRF activity in the posterior pituitary extract.  相似文献   
69.
Behavior Genetics - Trajectories of youth antisocial behavior (ASB) are characterized by both continuity and change. Twin studies have further indicated that genetic factors underlie continuity,...  相似文献   
70.
Adequate levels of health literacy are needed for transplant recipients to be able to understand and comply with medical recommendations. However, little is known about health literacy among transplant candidates. Therefore, the purpose of this study was to examine the levels of health literacy and cognitive functioning among patients being evaluated for various types of transplantation. There were 398 patients who completed a required psychological evaluation prior to being listed for transplant. This included a screen for cognitive impairment and limited reading and math ability. The prevalence of limited reading ability was 27.5%, limited math ability was 42.8%, and 30.7% had probable cognitive impairment. Rates of limited reading and math ability and cognitive impairment varied for each type of end‐stage disease. Limited reading ability was related to poorer cognitive functioning. Those with a higher likelihood of limited reading ability included blacks and males. Those more likely to have cognitive impairment included blacks and patients who are older. Results from this study suggest that patients should be regularly screened for health literacy and cognitive impairment. Once patients with difficulties are identified, recommendations can be provided to these patients at a level that they are able to understand.  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