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   8168篇
  免费   891篇
  国内免费   136篇
耳鼻咽喉   44篇
儿科学   119篇
妇产科学   64篇
基础医学   803篇
口腔科学   73篇
临床医学   961篇
内科学   920篇
皮肤病学   31篇
神经病学   1805篇
特种医学   497篇
外科学   396篇
综合类   1179篇
一般理论   2篇
预防医学   879篇
眼科学   68篇
药学   717篇
  10篇
中国医学   488篇
肿瘤学   139篇
  2024年   25篇
  2023年   151篇
  2022年   317篇
  2021年   455篇
  2020年   423篇
  2019年   375篇
  2018年   348篇
  2017年   373篇
  2016年   335篇
  2015年   366篇
  2014年   627篇
  2013年   579篇
  2012年   473篇
  2011年   513篇
  2010年   367篇
  2009年   380篇
  2008年   335篇
  2007年   324篇
  2006年   312篇
  2005年   258篇
  2004年   212篇
  2003年   207篇
  2002年   168篇
  2001年   131篇
  2000年   99篇
  1999年   96篇
  1998年   65篇
  1997年   77篇
  1996年   49篇
  1995年   61篇
  1994年   64篇
  1993年   56篇
  1992年   41篇
  1991年   50篇
  1990年   62篇
  1989年   42篇
  1988年   34篇
  1987年   28篇
  1986年   32篇
  1985年   41篇
  1984年   43篇
  1983年   22篇
  1982年   30篇
  1981年   22篇
  1980年   31篇
  1979年   19篇
  1978年   18篇
  1977年   24篇
  1975年   8篇
  1974年   8篇
排序方式: 共有9195条查询结果,搜索用时 15 毫秒
51.
择业期间大学生焦虑水平及其影响因素   总被引:16,自引:0,他引:16  
张弛  刘鹂 《中国心理卫生杂志》2002,16(11):779-780,767
目的 :对择业期间大学生焦虑水平及其影响因素进行调查 ,为高校心理卫生工作提供科学依据。方法 :采用“状态—特质焦虑量表”对 5 2 2名大学生择业期间焦虑水平进行测查 ,采用问卷调查法及访谈法探讨影响择业期间大学生焦虑水平的因素。结果 :择业情境导致大学生焦虑水平普遍升高 ,部分学生呈过度焦虑状态。择业期间大学生焦虑水平受自身条件、个人理想、社会环境、学校教育、家庭期望等因素的综合影响 ,其中自身条件、个人理想为首要因素。结论 :择业期间大学生产生焦虑的根本原因在于职业理想与实现可能的矛盾冲突  相似文献   
52.
53.
Summary We studied the membrane effects of (1S,2S)-2-(2-[[3-2(benzimidazolyl) propyllmethylamino]ethyl)-6-fluoro-1,2,3,4-tetrahydro-l-isopropyl-2-naphthyl-methoxy-acetate dihydrochloride, Ro 40-5967, a new non-dihydropyridine (DHP) Ca2+ channel antagonist, on dog coronary and saphenous arterial vascular muscle cells using the whole-cell patch-clamp method. Long-lasting (L-type) inward currents in 20 mM Ba2+ were measured over a range of test potentials (300 ms) from –50 mV to + 90 mV from a holding potential of –80 mV in the presence of 1 M Bay k8644 (a DHP Ca2+ agonist). Ro 40-5967 caused a concentration-dependent suppression of Ca2+ channel currents in muscle cells from both arteries, with greater potency on coronary than saphenous arterial cells. The concentration of Ro 40-5967 which inhibited the magnitude of peak inward currents by 50% (IC50) was estimated to be 1 M (n = 5) in muscle cells from coronary artery and 10 M (n = 4) in saphenous artery. Ro 40-5967 (1 M) decreased the amplitude of the activation current-voltage relationship for coronary L-type Ca2+ channel currents over a wider range of membrane potentials than verapamil, diltiazem, or nifedipine. In contrast, block of Ca2+ channel currents in saphenous artery cells by 1 M Ro 40-5967 was only observed at command potentials positive to 0 mV. Ro 40-5967 (1 M) significantly shifted the voltage-inactivation curve downward by 40% in coronary (n = 4), but only by 18% in saphenous arterial muscle cells (n = 3). The non-parallel shift of the coronary artery inactivation curve suggests that pronounced resting channel block is a notable feature of Ro 40-5967. The marked inhibition of Ba2+ current by 1 M Ro 40-5967 in the inactivation protocol in coronary arterial muscle cells was found over the entire range of membrane holding potentials tested, while inhibition in the saphenous artery inactivation curve occurred only from holding potentials more positive than –40 mV. Therefore, Ro 40-5967 is unique: 1) in acting over a wider range of voltages, on both instantaneous and resting Ca2+ currents, than other Ca2+ antagonists; 2) in producing more significant resting state block; and 3) in acting with selectivity for coronary over saphenous arteries.This research was supported by National Institutes of Health grants HL38537, HL38645, and by F. Hoffmann-La Roche, Basel, Switzerland  相似文献   
54.
Two sets of experiments were carried out to compare the effects of fenfluramine and fluoxetine on consummatory and operant behaviour. In food-deprived rats allowed access to a 35% sucrose solution, an initial period of sucrose consumption was followed by a short period of grooming and exploratory behaviour, later superceded by resting. This behavioural satiety sequence was advanced by fluoxetine, but disrupted bydl-fenfluramine, which suppressed post-prandial resting, even at sub-anorectic doses. Fluoxetine also elicited resting behaviour following water drinking. However, this did not appear to be a non-specific sedative effect, since fluoxetine increased post-prandial grooming. In rats performing on random interval schedules of food reinforcement, fluoxetine caused proportionally greater decreases in responding on a reinforcement-lean schedule (RI-300s), as compared to a reinforcement-rich schedule (RI-7.5s); this effect is similar to that of a reduction in level of food deprivation. By contrast, fenfluramine reduced responding equally on both schedules. In both paradigms, the effects of fluoxetine were compatible with an increase in postprandial satiety, but the effects of fenfluramine were not.  相似文献   
55.
形神兼养理论是中医养生思想体系中的重要组成部分 ,通过对《内经》相关文献的整理研究 ,试从辨证的形神一体观和具体的形神兼养大法两个方面对这一理论进行全面的探讨和总结 ,使之进一步系统化、理论化 ,并阐述了它的现实意义。为医学模式的转变提供理论依据 ;为现代心身医学的建立和养生保健提供宝贵经验和理论指导  相似文献   
56.
The experimental hepatic cirrhosis was induced either by bile duct ligation (BDL) or by pretreatment with dimethylnitrosamine (DMNA). The pharmacokinetics of theophylline were studied after a single intravenous or a single oral administration. Using the ultrafiltration method, protein-drug binding experiments were also carried out. The bilirubin level was several-fold increased by BDL, but not by DMNA treatment. The albumin content was decreased in both cirrhotic groups. The total clearance (Clt, ml/kg/hr) of theophylline in both hepatic cirrhosis groups significantly decreased and the terminal half-life (t1/2) in the cirrhotic rats was increased about two-fold after intravenous and oral administration. The volume of distribution at steady state (Vdss, ml/kg) was increased slightly in the cirrhotic groups. Protein binding in BDL (8.67±4.85%) decreased about four-folds, but in DMNA (73.00±9.85%) similar result, was observed as compared with the control. Increased free fraction of theophylline did not increase the volume of distribution in BDL. Therefore decreased total body clearance of theophylline was mainly due to decreased intrinsic clearance of theophylline in the liver. The absolute bioavailability of theophylline in these experiments was between 63.8 and 72.8%(66.1% in BDL, 63.8% in Sham operated and Control, 72.8% in DMNA). These results suggest that in the experimental hepatic cirrhosis model, administration route does not affect the disposition of theophylline.  相似文献   
57.
Gao  Qi  Wei  Jian-Mei  Chen  Shu-Hui 《Pharmaceutical research》1995,12(3):337-341
Crystals of the C2-acetate analog of paclitaxel, grown from a mixture of isopropyl alcohol and methanol, belong to the space group P2l with a = 9.058(3), b = 18.306(5), c = 15.043(1) , = 97.09(1)°, Z = 2, V = 2475.1(9)3, D calc = 1.269 gcm–3 and µ = 0.75 cm–1. The structure was determined by direct methods and refined to R(F) = 0.054 and wR(F) = 0.057 for 605 variables and 3496 observed reflections. The paclitaxel side chain possesses a conformation similar to that observed in the crystal structure of docetaxel (Taxotere®). A three dimensional network of hydrogen bonds is formed through solvent molecules and stabilizes the crystal lattice.  相似文献   
58.
The effect of probenecid on the pharmacokinetics of diflunisal and its glucuronide and sulphate conjugates was studied in 8 healthy volunteers. Diflunisal 250 mg b. d. was administered p. o. for 15 days and its steady state pharmacokinetics was evaluated on Day 16 after the last dose (control phase). Probenecid 500 mg b. d. was co-administered throughout the entire study period in the treatment phase of the study.The steady state plasma concentration of diflunisal was significantly higher during the probenecid treatment phase as compared to the control phase (104.0 vs. 63.1 g·ml–1). This was the result of a significant decrease in the plasma clearance of diflunisal from 5.8 (control) to 3.4 ml·min–1 (probenecid co-administration). The metabolite formation clearances of both glucuronides were significantly decreased by probenecid, -45 % and -54 % for the phenolic and acyl glucuronide, respectively. The metabolite formation clearance of the sulphate conjugate was not affected by probenecid co-administration.Steady state plasma concentrations of the sulphate and glucuronide conjugates of diflunisal were 2.5- to 3.1-fold higher during probenecid co-administration, due to a significant reduction in the renal clearance of the three diflunisal conjugates. Probenecid also reduced the plasma protein binding of diflunisal, but only to a minor extent; the unbound plasma fraction of diflunisal at steady state averaged between 5 and 30 % higher during probenecid co-administration.  相似文献   
59.
目的:探讨闭角型青光眼患者凝血指标变化与临床的关系。方法:对50例闭角型青光眼患者及43例正常对照组进行了凝血指标(PT、TT、Fbg、APTT)检测。结果:闭角型青光眼患者与对照组比较PT、TT无显著变化(P<0.05),Fbg含量升高有极显著性差异(P<0.01),APTT时间缩短有极显著性差异(P<0.01)。结论:闭角型青年眼患者体内血液是高凝状态,而这种高凝状态在闭角青光眼病的发生、发展中起着重要的作用。  相似文献   
60.
Since our major hypothesis is that prenatal protein malnutrition significantly affects hippocampal neuroplasticity, this study examined the effects of prenatal protein malnutrition on the modulation of dentate granule cell excitability in freely moving rats at 15, 30 and 90 days of age across the vigilance states of quiet waking (QW), slow-wave sleep (SWS) and rapid eye movement (REM) sleep. Using paired-pulse stimulation, the paired-pulse index (PPI), a measure of the type and degree of modulation of dentate granule cell excitability elicited by stimulation of the medial perforant path, was obtained for each vigilance state at each stage of development. Four specific measures of granule cell excitability were computed, namely, PPI using both population spike amplitude (PSA) and EPSP slope measures, absolute values of PSA(1) and EPSP(1) slope. PPI values obtained at 15, 30 and 90 days of age, however, were altered during normal ontogenetic development, but not by vigilance state. At 15 days of age, the malnourished group exhibits greater early inhibition of the PPI using the PSA measure at IPIs between 20 and 30 ms regardless of vigilance state, while at 30 days of age, the malnourished group exhibits greater facilitation at IPIs between 50 and 70 ms during QW and SWS, but not during REM sleep. In the control adult (PND90) and juvenile (PND30) animal, PSA(1) values are significantly higher during SWS than in QW or REM sleep. However, for the younger malnourished animals (PND15 and PND30), PSA(1) values were found to be significantly greater during REM sleep rather than SWS. Therefore, as the animal matures, there appears to be a shift in vigilance state dependent synaptic transmission through the hippocampal trisynaptic circuit from REM sleep to SWS in both control and malnourished animals, with the change occurring later in malnourished animals when compared to control ones. Furthermore, our findings suggests that prenatal protein malnutrition significantly alters modulation of dentate granule cell excitability (i.e., PPI values using the PSA measure) during the earlier stages of development but not in adulthood.  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