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   39484篇
  免费   3724篇
  国内免费   1297篇
耳鼻咽喉   238篇
儿科学   635篇
妇产科学   245篇
基础医学   3353篇
口腔科学   598篇
临床医学   4139篇
内科学   4412篇
皮肤病学   325篇
神经病学   2250篇
特种医学   2736篇
外国民族医学   3篇
外科学   1953篇
综合类   6199篇
现状与发展   2篇
预防医学   4551篇
眼科学   1370篇
药学   7379篇
  36篇
中国医学   2641篇
肿瘤学   1440篇
  2024年   112篇
  2023年   581篇
  2022年   1446篇
  2021年   1836篇
  2020年   1598篇
  2019年   1524篇
  2018年   1459篇
  2017年   1568篇
  2016年   1613篇
  2015年   1612篇
  2014年   2625篇
  2013年   2818篇
  2012年   2633篇
  2011年   2690篇
  2010年   2156篇
  2009年   1675篇
  2008年   1893篇
  2007年   1948篇
  2006年   1690篇
  2005年   1405篇
  2004年   1177篇
  2003年   1041篇
  2002年   829篇
  2001年   736篇
  2000年   642篇
  1999年   508篇
  1998年   408篇
  1997年   435篇
  1996年   337篇
  1995年   388篇
  1994年   350篇
  1993年   275篇
  1992年   270篇
  1991年   259篇
  1990年   210篇
  1989年   172篇
  1988年   191篇
  1987年   163篇
  1986年   134篇
  1985年   226篇
  1984年   205篇
  1983年   162篇
  1982年   125篇
  1981年   91篇
  1980年   68篇
  1979年   68篇
  1978年   46篇
  1977年   28篇
  1976年   29篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
There is a growing need for research into new skin- and environment-friendly surfactants. This paper focuses on a natural surfactant of an alkylpolyglucoside type, which can form both thermotropic and lyotropic liquid-crystalline phases. The aim of this study was to relate some physicochemical properties (characterised by polarisation and transmission electron microscopy, thermal analysis and rheology) of the three formulations based on cetearyl glucoside and cetearyl alcohol, to the results of in vitro and in vivo bioavailability of hydrocortisone (HC). The three formulations contained oils of different polarity (medium chain triglycerides: MG, isopropyl myristate: IPM and light liquid paraffin: LP), respectively. In vitro permeation was followed through the artificial skin constructs (ASC), while the parameters measured in vivo were erythema index: EI (using instrumental human skin blanching assay), transepidermal water loss (TEWL) and stratum corneum hydration (SCH). The vehicles based on cetearyl glucoside and cetearyl alcohol showed a complex colloidal structure of lamellar liquid-crystalline and lamellar gel-crystalline type, depending on oil polarity. Rheological profile of the vehicle was directly related to the in vitro profile of the HC permeation. In vivo results suggested that the vehicle with MG retarded the HC permeation, whereas less polar IPM and non-polar LP enhanced it. It is suggested that the enhancement is achieved either by a direct interaction with lipid lamellae of the SC or indirectly by improving skin hydration.

There were no adverse effects during in vivo study, which indicates a good safety profile of this alkylpolyglucoside surfactant.  相似文献   

82.
AIMS: Metabolic responses to manipulation of the plasma free fatty acid (FFA) concentration were assessed in six healthy men via cross-over design to determine whether FFAs independently influence insulin sensitivity. METHODS: Intramyocellular lipid (IMCL) was measured by proton magnetic resonance spectroscopy and insulin sensitivity via frequently sampled intravenous glucose tolerance test (IVGTT) after 67 h of two identical low carbohydrate/high fat (LC) diets which were used to elevate IMCL and plasma FFAs. To uncouple the influence of FFAs and IMCL on insulin sensitivity, FFAs were suppressed 30 min prior to and during IVGTT in one treatment [LC + nicotinic acid (NA)] by NA ingestion. RESULTS: Vastus lateralis IMCL was significantly elevated in LC (13.3 +/- 1.1 x 10(-3)) and LC + NA (13.5 +/- 1.1 x 10(-3)) (P < 0.01 for both), but was not different between conditions (P > 0.05). Plasma FFAs were raised in LC (0.79 +/- 0.08 mmol/l) and LC + NA (0.80 +/- 0.11 mmol/l) (P < 0.01 for both) and were significantly reduced by NA ingestion prior to (0.36 +/- 0.05 mmol/l, P < 0.01) and during IVGTT (P < 0.05) in LC + NA. Despite marked differences in plasma FFA availability, insulin sensitivity and glucose tolerance were not different between LC and LC + NA (P > 0.05 for both). CONCLUSIONS: Plasma FFAs appear to exert no immediate effect on insulin sensitivity/glucose tolerance independent of their action on intracellular lipid moieties. Further research is required to elucidate the duration of FFA suppression required to restore insulin sensitivity following lipid-induced insulin resistance.  相似文献   
83.
Abstract. The mechanisms responsible for the decreased high density lipoprotein (HDL) cholesterol levels associated with obesity and insulin resistance are not well understood. Lecithin: cholesterol acyltransferase (LCAT) and cholesterol ester transfer protein (CETP) are key factors in the esterification of cholesterol in HDL and the subsequent transfer of cholesteryl ester towards apolipoprotein B-containing lipoproteins. Phospholipid transfer protein (PLTP) may be involved in the regulation of HDL particle size. We therefore measured the activities of LCAT, CETP and PLTP using exogenous substrate assays, as well as lipids, lipoproteins, insulin and C-peptide in fasting plasma from eight healthy obese men (body mass index >27 kg m-2) and 24 non-obese subjects. The obese men had lower levels of HDL cholesterol (P<0·05) and higher levels of plasma triglycerides (P<0·05), insulin (P<0·05) and C-peptide (P<0·01), as compared to the quartile of subjects with the lowest body mass index (BMI <22·4 kg m-2). CETP and PLTP activities were elevated in the obese men by 35% (P<0·01) and by 15% (P<0·05), respectively. LCAT activity was comparable among the quartiles. Linear regression analysis showed that CETP activity was positively correlated with body mass index (P<0·02), fasting blood glucose (P7lt;0·05) and plasma C-peptide (P<0·05). PLTP activity was positively related to body mass index (P<0·01), waist to hip circumference ratio (P<0·001), as well as to fasting blood glucose (P<0·05) and plasma C-peptide (P<0·05) It is concluded that the activities of CETP and PLTP are influenced by adiposity and possibly by insulin resistance. Elevated lipid transfer protein activities may provide a mechanism that contributes to alterations in HDL in insulin resistant states.  相似文献   
84.
山东农村511名高中生伤害的现况调查   总被引:2,自引:0,他引:2  
目的 调查高中生伤害的情况、危险因素及其影响,为制定高中生伤害的预防措施提供依据。方法 以整群抽样的方法在山东省利津县某高中9个班的511名高中生中进行调查和描述性分析。结果 在过去一年里所调查的高中生8种伤害(车祸、中毒、跌落、烧烫伤、电击伤、钝/锐器伤、动物昆虫叮咬伤、溺水)的总发生率为15.5%,男、女生发生率分别为18.5%、11.9%。发生率最高的前4位伤害依次是跌落伤(7.6%)、中毒(4.3%)、车辆伤(3.3%)和钝/锐器伤(3.1%)。家中常发生中毒、烧烫伤,学校常发生跌落伤和钝/锐器伤。平均每人次伤害花费最大的是车辆伤,其次为跌落伤;平均影响学习时间最长的是车辆伤,其次为烧烫伤和跌落伤。伤害发生率在性别和父亲健康状况上有显著性差异。结论 针对不同伤害特点采取相应预防措施,以降低伤害发生率,促进青少年健康,减少社会健康损失和经济损失。  相似文献   
85.
The present study was designed to investigate the effects of combined treatment with a serotonin (5-HT)1A receptor agonist, 8-hydroxy-2-(dipropylamino)-tetralin (8-OH-DPAT), and a muscarinic acetylcholine receptor antagonist, scopolamine, on water maze (WM) navigation. Treatment with either 8-OH-DPAT or scopolamine before daily behavioral training disrupted spatial navigation at medium doses and cue navigation at high doses. Pretraining treatment with a combination of subthreshold doses of 8-OH-DPAT and scopolamine impaired WM spatial and cue navigation, but did not impair the WM performance if the drugs were injected post-training. In trained rats, combined injections of subthreshold doses of 8-OH-DPAT and scopolamine given pretraining did not impair the rats' ability to find the platform in a familiar or in a novel position. The combination of 8-OH-DPAT and scopolamine also disrupted WM navigation in rats with central 5-HT depletion. A combination of a peripheral muscarinic acetylcholine receptor antagonist and 8-OH-DPAT had no effect on WM navigation. These data suggest that combined treatment with drugs blocking muscarinic acetylcholine receptors and activating 5-HT1A receptors greatly impairs WM learning/performance, but does not impair spatial memory per se.  相似文献   
86.
SRTR Center-Specific Reporting Tools: Posttransplant Outcomes   总被引:3,自引:2,他引:1  
Measuring and monitoring performance—be it waiting list and posttransplant outcomes by a transplant center, or organ donation success by an organ procurement organization and its partnering hospitals—is an important component of ensuring good care for people with end-stage organ failure. Many parties have an interest in examining these outcomes, from patients and their families to payers such as insurance companies or the Centers for Medicare and Medicaid Services; from primary caregivers providing patient counseling to government agencies charged with protecting patients.
The Scientific Registry of Transplant Recipients produces regular, public reports on the performance of transplant centers and organ procurement organizations. This article explains the statistical tools used to prepare these reports, with a focus on graft survival and patient survival rates of transplant centers—especially the methods used to fairly and usefully compare outcomes of centers that serve different populations. The article concludes with a practical application of these statistics—their use in screening transplant center performance to identify centers that may need remedial action by the OPTN/UNOS Membership and Professional Standards Committee.  相似文献   
87.
高效液相色谱法测定硫酸奈替米星注射液的含量   总被引:4,自引:0,他引:4  
杨立  陈卫波  翁德民 《中国热带医学》2006,6(1):132-134,175
目的采用高效液相色谱法测定硫酸奈替米星及注射液的含量。方法以μ-Diamonsil—C18为分析柱,流动相为1.5%的磷酸二氢钾-乙睛,流速为1.0ml/min,检测渡长为205nm。含量测定用峰面积外标法。结果硫酸奈替米星在0.1—1.6mg/ml浓度范围内呈现良好线性关系,r=0.9998.平均回收率为99.5%,RSD=0.4%(n=9)。结论本方法操作简便、快速,结果准确可靠,重现性好,均能很好地满足质量控制的要求,为开辟氨基糖苷类抗生素含量测定的仪器提供了一定借鉴。  相似文献   
88.
Long-term outcome and complications of children born with meningomyelocele   总被引:9,自引:1,他引:8  
The long-term functional outcome of 101 children born with meningomyelocele between 1971 and 1981 was assessed, by a combination of retrospective chart review and follow-up assessments. The children had been managed at birth using a process ofnonstandardized selection. Eighty-three of the 101 patients survived after a minimum follow-up of 8.6 years, for a mortality rate of 18%. Forty-four of 83 children (53%) were community ambulators, and this correlated well with the presence of intact quadriceps function. Forty-eight children (58%) attended normal school and were grade-appropriate. Sixty-two of 83 patients (75%) were socially continent of urine, and 71/83 (86%) were socially continent of stool. Hydrocephalus was present in 93 of the 101 children in the study, and 85 children were shunted. Half of the shunted children required a shunt revision in the first year of life, and thereafter the rate of revision decreased, so that after 2 years the risk of revision was approximately 10% per year.  相似文献   
89.
采用限制性酶切片段长度多态性分析法,检测在胃癌高发区庄河检出的19例胃癌高系家族成员胃蛋白酶原C基因多态性,发现三种常见片段及一种稀有片段。对其中4例携带稀有片段的受检者进行了胃镜追踪观察,2.5年后发现1例早期胃癌。本文对此作了初步探讨。  相似文献   
90.
以高频喷射通气结合胸壁挤压(HFJV+CWC)为通气模式,观察其对组胺致肺损伤犬呼吸循环功能的影响,并与单纯高频喷射通气(HFJV)进行比较。结果表明:与HFJV相比,HFJV+CWC时的功能残气量(FRC)、PaCO_2和PCO_2均显著降低(P<0.01),肺泡通气量(V_A)和二氧化碳排出量(CO_2)均显著增高(P<0.01),每分呼出气量(V_E)、PaO_2、PCO_2、吸气峰压(PIP)、平均气道压(Paw)、呼气末压(EEP)、HR、平均动脉压(MAP)、肺动脉压(PAP)和肺毛细血管楔压(PCWP)均无显著变化(P>0.05)。提示:HFJV+CWC除保留单纯HFJV时气道开放、气道低压、良好的血液氧合、不影响循环功能等特点外,还具有增加呼气动力,改善肺泡通气,显著促进CO_2排除等优点。  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