首页 | 官方网站   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   2065篇
  免费   82篇
  国内免费   3篇
医药卫生   2150篇
  2023年   12篇
  2022年   13篇
  2021年   55篇
  2020年   27篇
  2019年   43篇
  2018年   59篇
  2017年   35篇
  2016年   51篇
  2015年   55篇
  2014年   73篇
  2013年   117篇
  2012年   198篇
  2011年   146篇
  2010年   123篇
  2009年   70篇
  2008年   121篇
  2007年   137篇
  2006年   117篇
  2005年   122篇
  2004年   118篇
  2003年   101篇
  2002年   105篇
  2001年   29篇
  2000年   29篇
  1999年   20篇
  1998年   17篇
  1997年   12篇
  1996年   11篇
  1995年   11篇
  1994年   8篇
  1993年   8篇
  1992年   10篇
  1991年   13篇
  1990年   4篇
  1989年   5篇
  1988年   4篇
  1987年   3篇
  1986年   4篇
  1985年   4篇
  1984年   13篇
  1983年   2篇
  1982年   7篇
  1981年   5篇
  1979年   3篇
  1978年   6篇
  1977年   3篇
  1976年   5篇
  1975年   2篇
  1967年   2篇
  1965年   3篇
排序方式: 共有2150条查询结果,搜索用时 46 毫秒
31.
32.
33.
OBJECTIVES: We sought to describe clinical and laboratory findings for a large cohort of patients with thienopyridine-associated thrombotic thrombocytopenic purpura (TTP). BACKGROUND: The thienopyridine derivatives, ticlopidine and clopidogrel, are the 2 most common drugs associated with TTP in databases maintained by the U.S. Food and Drug Administration (FDA). METHODS: Clinical reports of TTP associated with clopidogrel and ticlopidine were identified from medical records, published case reports, and FDA case reports (n = 128). Duration of thienopyridine exposure, clinical and laboratory findings, and survival were recorded. ADAMTS13 activity (n = 39) and inhibitor (n = 30) were measured for a subset of individuals. RESULTS: Compared with clopidogrel-associated TTP cases (n = 35), ticlopidine-associated TTP cases (n = 93) were more likely to have received more than 2 weeks of drug (90% vs. 26%), to be severely thrombocytopenic (84% vs. 60%), and to have normal renal function (72% vs. 45%) (p < 0.01 for each). Compared with TTP patients with ADAMTS13 activity >15% (n = 13), TTP patients with severely deficient ADAMTS13 activity (n = 26) were more likely to have received ticlopidine (92.3% vs. 46.2%, p < 0.003). Among patients who developed TTP >2 weeks after thienopyridine, therapeutic plasma exchange (TPE) increased likelihood of survival (84% vs. 38%, p < 0.05). Among patients who developed TTP within 2 weeks of starting thienopyridines, survival was 77% with TPE and 78% without. CONCLUSIONS: Thrombotic thrombocytopenic purpura is a rare complication of thienopyridine treatment. This drug toxicity appears to occur by 2 different mechanistic pathways, characterized primarily by time of onset before versus after 2 weeks of thienopyridine administration. If TTP occurs after 2 weeks of ticlopidine or clopidogrel therapy, therapeutic plasma exchange must be promptly instituted to enhance likelihood of survival.  相似文献   
34.
Circannual variations in plasma levels of testosterone (T), 17beta-estradiol (E(2)), and 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (DHP) as well as seasonal fluctuations in ovarian steroid synthetic potential were observed in Indian major carp, Labeo rohita. A study was also conducted to examine the mechanism of the development of gonadotropin-induced maturational competence in oocytes of this fish. The present study recorded the lowest values of plasma E(2) and T in L. rohita during the period from October to January. A mild increase in the levels of these steroids observed in February was followed by their rapid rise reaching peak values in April, when the ovary contained mostly the vitellogenic follicles. In the month of May, as the postvitellogenic follicles predominated in the ovary, there was a decline in plasma concentrations of both T and E(2). Low levels of these steroids in plasma remained until January, except a small elevation detectable during June and July (spawning stage). DHP was not detected in the plasma of this fish collected during the period from August to March. Existence of DHP was first recorded in blood in the month of April (vitellogenic stage) and it quickly reached the peak value in May (postvitellogenic stage), followed by a sudden decline in the month of June. Under stimulation of fish pituitary extract (FPE), as a source of gonadotropin, in vitro production of E(2) and T by the vitellogenic follicles was shown to be highest compared to their production rate in other stages, while the postvitellogenic follicles recorded the highest rate of DHP synthesis. Acquisition of oocyte maturational competence (OMC) was shown to develop either by priming the vitellogenic stage fish with a single dose of FPE or by in vitro addition of FPE in culture. In vitro treatment of trilostane, an inhibitor of 3beta-HSD, blocked the FPE-stimulated steroid production but not the development of OMC. Presence of cycloheximide and actinomycin D in the incubation was shown to inhibit FPE-induced development of OMC, indicating the requirement of de novo protein synthesis for this process.  相似文献   
35.
Influenza surveillance was conducted in Pune, India in 2003. A total of 573 throat swabs/ nasal swabs (TS/NS) and 190 nasopharyngeal aspirates (NPA) were collected from 763 in- and out-patients who were mostly children aged 0-16 years. TS/NS (507/573) and NPA (42/190) specimens were processed in MDCK cell cultures and identified with the hemagglutination inhibition test (HI). A total of 37 influenza viruses was isolated: twenty-three type A (H3N2) and 14 type B of the Yamagata lineage were isolated from 29 children and 8 adults. Three type A (H3N2) isolates were characterized as being similar to A/Panama/2007/99 like, A/Korea/770/2000 like, and B/Sichuan/379/99 like strains.  相似文献   
36.
We evaluated the safety and feasibility of ipsilateral radial and ulnar artery cannulation during the same catheterization procedure. Crossover from radial to femoral was done in 122 patients. Both ipsilateral radial and ulnar catheterization were performed in 16 patients without any complications, which was further supported by Doppler ultrasonography.  相似文献   
37.
Schwannomas are benign, encapsulated, primary neurilemmal tumors composed of proliferating Schwann cells. Schwannomas are commonly seen in the orbit, but are rare on the epibulbar surface. Herein, we report a case of a 12-year-old boy who presented to us with a slow-growing painless subconjunctival mass in the left eye. There was no intraocular extension of the mass and intra-operatively, the mass could be clearly delineated and was excised off the underlying sclera. Histopathological examination of the mass showed typical features of schwannoma and immunohistochemistry helped to confirm the diagnosis. There was no recurrence of the lesion observed at follow-up 26 months after surgery. Here, we describe this uncommon tumor and review the available literature. Although rare, an epibulbar schwannoma should be considered in the differential diagnosis of an amelanotic, painless subconjunctival nodular mass. Excision of the lesion is the recommended treatment.  相似文献   
38.
Rare earth (RE) ions are known to improve the magnetic interactions in spinel ferrites if they are accommodated in the lattice, whereas the formation of a secondary phase leads to the degradation of the magnetic properties of materials. Therefore, it is necessary to solubilize the RE ions in a spinel lattice to get the most benefit. In this context, this work describes the synthesis of Co–Zn ferrite nanoparticles and the Gd3+ doping effect on the tuning of their magnetic properties. The modified sol–gel synthesis approach offered a facile way to synthesize ferrite nanoparticles using water as the solvent. X-ray diffraction with Rietveld refinement confirmed that both pure Co–Zn ferrite and Gd3+ substituted Co–Zn ferrite maintained single-phase cubic spinel structures. Energy dispersive spectroscopy was used to determine the elemental compositions of the nanoparticles. Field and temperature dependent magnetic characteristics were measured by employing a vibration sample magnetometer in field cooled (FC)/zero field cooled (ZFC) modes. Magnetic interactions were also determined by Mössbauer spectroscopy. The saturation magnetization and coercivity of Co–Zn ferrite were improved with the Gd3+ substitution due to the Gd3+ (4f7)–Fe3+ (3d5) interactions. The increase in magnetization and coercivity makes these Gd3+ substituted materials applicable for use in magnetic recording media and permanent magnets.

Rare earth (RE) ions are known to improve the magnetic interactions in spinel ferrites if they are accommodated in the lattice, whereas the formation of a secondary phase leads to the degradation of the magnetic properties of materials.  相似文献   
39.
Hypertension is an important, modifiable risk for cardiovascular disease. The Women Take Heart study, a prospective, community-based cohort study of risk factors for heart disease, provides an opportunity to examine prevalence, awareness, and control of hypertension specifically in women. In 1992, 5932 women, age 35 and older (mean age, 52.9; 86% white, 9% African American, 5% other) and free of active heart disease symptoms for 3 months, were recruited through Chicago area public announcements, and their baseline examination data analyzed. Overall, 47.6% were hypertensive (systolic blood pressure 140 mm Hg or diastolic blood pressure 90 mm Hg, or self-report). Only 17.3% reported being hypertensive; in 63.2% of all hypertensive women, the hypertension was undetected or unacknowledged. Blood pressure was controlled to <140/90 mm Hg in 24.1% of self-reported hypertensives. Results from this study and national surveys indicate that hypertension detection and control remain major public health challenges in preventing cardiovascular disease in older women.  相似文献   
40.
ContextOlder adults with advanced cancer face uncertainty related to their disease and treatment.ObjectivesTo evaluate the associations of uncertainty with psychological health and quality of life (QoL) in older adults with advanced cancer.MethodsSecondary cross-sectional analysis of baseline data from a national clustered geriatric assessment trial. Patients 70 years and older with advanced cancer considering a new line of chemotherapy were recruited. We measured uncertainty using the modified nine-item Mishel Uncertainty in Illness Scale. Dependent variables included anxiety (Generalized Anxiety Disorder-7), depression (Generalized Depression Scale-15), distress (distress thermometer), QoL (Functional Assessment of Cancer Therapy—General), and emotional well-being (Functional Assessment of Cancer Therapy—General subscale). We used multivariate linear regression analyses to evaluate the association of uncertainty with each dependent variable. We conducted a partial least squares analysis with a variable importance in projection (VIP) plot to assess the contribution of individual variables to the model. Variables with a VIP <0.8 were considered less influential.ResultsWe included 527 patients (median age 76 years; range 70–96). In multivariate analyses, higher levels of uncertainty were significantly associated with greater anxiety (β = 0.11; SE = 0.04), depression (β = 0.09; SE = 0.02), distress (β = 0.12; SE = 0.02), as well as lower QoL (β = ?1.08; SE = 0.11) and emotional well-being (β = ?0.29; SE = 0.03); the effect sizes were considered small. Uncertainty items related to disease and treatment were most strongly associated with psychological health and QoL scores (all VIP >0.8).ConclusionUncertainty among older patients with advanced cancer is associated with worse psychological health and QoL. Tailored uncertainty management strategies are warranted.  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-23

京公网安备 11010802026262号