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   163752篇
  免费   12842篇
  国内免费   5303篇
耳鼻咽喉   1210篇
儿科学   3044篇
妇产科学   1597篇
基础医学   24652篇
口腔科学   3042篇
临床医学   16901篇
内科学   22216篇
皮肤病学   1517篇
神经病学   8555篇
特种医学   4392篇
外国民族医学   22篇
外科学   13772篇
综合类   25692篇
现状与发展   11篇
一般理论   25篇
预防医学   10993篇
眼科学   4341篇
药学   17143篇
  17篇
中国医学   8146篇
肿瘤学   14609篇
  2024年   349篇
  2023年   1923篇
  2022年   4091篇
  2021年   5670篇
  2020年   5033篇
  2019年   5187篇
  2018年   5131篇
  2017年   5020篇
  2016年   5182篇
  2015年   5306篇
  2014年   8381篇
  2013年   9366篇
  2012年   7805篇
  2011年   9067篇
  2010年   7854篇
  2009年   7759篇
  2008年   7828篇
  2007年   8921篇
  2006年   8188篇
  2005年   8177篇
  2004年   7139篇
  2003年   6335篇
  2002年   4712篇
  2001年   4613篇
  2000年   3789篇
  1999年   3523篇
  1998年   2548篇
  1997年   2231篇
  1996年   2320篇
  1995年   2244篇
  1994年   1955篇
  1993年   1784篇
  1992年   1552篇
  1991年   1340篇
  1990年   1126篇
  1989年   1053篇
  1988年   997篇
  1987年   763篇
  1986年   593篇
  1985年   699篇
  1984年   714篇
  1983年   445篇
  1982年   556篇
  1981年   474篇
  1980年   411篇
  1979年   328篇
  1978年   274篇
  1977年   220篇
  1976年   249篇
  1975年   159篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
A cytomorphometric analysis of superficial vaginal cells inwomen in three groups of different types of hormonal concentrationwas made. There were 15 women in each group. Group I was studiedduring a natural cycle, group II under oral contraceptive therapyand group III during an in-vitro fertilization (IVF) stimulationprotocol. Morphometric parameters were measured on an imageanalyser. The area, perimeter and several form factors weremeasured separately for nuclei and cytoplasm. The nucleus:cytoplasmicratio was also determined. The cytoplasmic area was significantlyreduced in group II and was associated with a statisticallysignificant reduction of the nuclear area. The nucleus:cytoplasmicratio appeared significantly increased in group II and reducedin group III. Low oestradiol impregnation obtained with an oralminidosed contraceptive interfered with vaginal cell maturation.High oestradiol concentrations obtained during IVF protocolsinduced marked nuclear pycnosis but did not induce supra-physiologicalcell enlargement. Maximal cell size is genetically regulatedaccording to Driesch's law of volume invariance and hormonalover-stimulation has no effect on cell size. The nucleus:cytoplasmicratio appears to be a powerful parameter reflecting the oppositeeffects of hormones on cell compartments.  相似文献   
52.
The present study was designed to examine the effects of a >30kDa fraction of medium conditioned for 2 days by adult rat seminiferoustubules on inhibin secretion by cultured tubules, and on spermatogenesisand fertility of male rats. Inhibin secretion was assayed byadding the >30 kDa fraction to 5 cm segments of adult ratseminiferous tubules and measuring inhibin by radioimmunoassayat 2 day intervals. Fertility was assayed by injecting malerats daily for up to 45 days with the >30 kDa fraction andthen mating them with a proestrus female, or by injecting for15 days and mating them with two female rats. The assay usedto evaluate the in-vivo effect of the >30 kDa fraction onthe testis involved an assessment of frequencies of seminiferoustubule stages scored by transillumination on intact tubules.The addition of the >30 kDa fraction to the adult rat seminiferoustubules cultured for 2 days resulted in an inhibition of inhibinsecretion into the medium. This effect was reversed when thefraction was removed and changed with fresh medium and culturedfor a further 4 days. The >30 kDa fraction administered i.p.to adult male rats resulted in a low fertilization rate comparedto control rats (67%) (P < 0.05). The assessment of frequenciesof seminiferous tubule stages scored by transillumination showedan increased frequency of stage VI and decreased frequency ofstages VII and VIII after treatment. The results of the presentstudy provide additional evidence that local regulation of Sertolicell function is mediated by a >30 kDa component or componentssecreted by adult seminiferous tubules which could arrest spermatogenesis.  相似文献   
53.
泵式自体输血过滤引流系统在急症救护中的应用   总被引:5,自引:1,他引:4  
自体输血、胸腔闭式引流,是缓解血源矛盾、赢得抢救时机、防治心肺衰竭及ARDS/MOF的重要措施。笔者研制成功的手控泵式储血过滤引流系列在战地、灾害现场,以及平时的心肺手术中,共应用3000余例,现重点对其功能设计和用于自体输血、紧急救护做讨论和评估。  相似文献   
54.
Six preparations were considered: three multiple unit dosage forms (micropellets in capsules) (D, E and G) and one matrix tablet (B) were experimental prolonged release formulations, two non-disintegrating tablets (A and C) were commercial products. The in vitro dissolution behaviour of the differing formulations was investigated using the USP XXII paddle apparatus. The in vivo study was effected on a panel of 12 healthy volunteers. The two commercial tablets (A and C) showed mean dissolution time (MDT) of 1.34 and 1.44 h and td of 91 and 92 min, respectively; for prolonged release formulations (B, E, D, and G) MDT ranged between 2.28 and 4.23 h and td between 149 and 291 min. The mean residence time (MRT) was 8.68 and 6.47 h for tablets A and C, respectively; it ranged between 9.62 and 10.24 h for the multiple unit formulations E, D, and G and was 11.27 h for matrix B. Formulation B also showed the higher apparent elimination half-life t1/2 (7.12 h), while apparent t1/2 for all the other formulations were very similar, ranging between 5.04 and 5.28 h. High variability between the various formulations was found for Cmax and AUC values, and no relationships could be established with the type of formulation. An in vitro/in vivo correlation was found for all the formulations examined on the basis of analogous parameters (MDT and MRT); (r = 0.83, p <0.05). In a few cases the Wagner-Nelson deconvolution method was applied to individual plasma level versus time curves and the corresponding absorption curves were obtained. In these cases the in vitro/in vivo correlation was tested on the basis of the comparison of the in vivo absorption curves with the in vitro dissolution profiles. This was accomplished using the ‘Levy's plot’ (per cent released versus per cent absorbed) approach and provided further support for the correlation found.  相似文献   
55.
56.
安吉复口服液的耐缺氧,耐低温和抗疲劳作用   总被引:2,自引:0,他引:2  
采用缺氧、寒冷和负重游泳等方法,观察了安吉复口服液(0.025、0.1和0.4mg·kg~(-1),ig,qd×14d)对小鼠的耐缺氧、耐低温及抗疲劳作用.结果表明,安吉复口服液0.1、0.4mg·kg~(-1)可延长KCN中毒小鼠的存活时间及延长小鼠在寒冷环境中存活时间,而0.4mg·kg~(-1)可延长常压缺氧条件下小鼠存活时间及延长小鼠负重游泳时间.  相似文献   
57.
Effect of buffering on pharmacokinetics of ketoprofen enantiomers in man   总被引:1,自引:0,他引:1  
Aims Concomitant administration of magnesium hydroxide may affect the rate or extent of absorption of non-steroidal anti-inflammatory drugs. In order to find out whether or not buffering modifies the pharmacokinetics of ketoprofen, plasma concentration-time courses resulting from oral administration of unbuffered formulations were compared with those of buffered formulations.
Methods Two groups of 12 healthy and young male subjects were included in two randomized cross-over studies and received single oral doses of ketoprofen 12.5 or 25  mg, respectively, given as tablets which were either unbuffered or buffered with magnesium hydroxide/citrate. Ketoprofen enantiomers in plasma were determined by h.p.l.c. up to 24  h post-dose.
Results Maximum plasma concentrations ( C max ) of both the (R)- and (S)-enantiomer, observed after administration of the buffered formulations (12.5 and 25  mg), were higher compared with the unbuffered tablets by about 50–80%. The area under concentration-time data (AUC) was unaffected, and, hence, C max/AUC was increased by buffering. Time to C max ( t max ) and mean residence time (MRT) tended to be or was shortened by buffering.
Conclusions It is concluded that buffering of two ketoprofen formulations with magnesium hydroxide/citrate enhanced the concentration maximum by increasing the rate of absorption and leaving AUC unaffected.  相似文献   
58.
Current knowledge about alcohol and marital functioning is limited by restrictive sample selection, inattention to the literature on individual-based alcoholic subtypes, and lack of research linking individual differences among alcoholics to marital functioning. The present study was designed to study marital functioning of alcoholics in light of current alcohol typologies. Subjects were part of a larger study on conjoint treatment of alcoholic males and their female partners. Four typologies—including Type 1/2, In-Home/Out-of-home, SteadyIEpisodic, and EarlyILate Onset—were tested for replicability and discriminant validity before linking them to marital functioning. Discriminant validity was found only for the Early (59%)-versus Late (41 %)-Onset typology; thus, further analyses linked only this typology with marital functioning. At baseline, Early-Onset couples reported more marital instability, and the females in these couples were more distressed. During treatment, Early-Onset couples reported higher daily marital satisfaction than Late-Onset couples. Regardless of age of onset, males reported higher marital satisfaction than their spouses during treatment, but their satisfaction did not increase during treatment. Female partners' marital satisfaction increased during treatment. Female partners of Late-Onset males reported particularly low marital satisfaction during treatment. Parsing the sample according to the early-/late-onset typology yielded different predictors of marital satisfaction for males and females within each subtype. For female partners of Early-Onset alcoholics, psychological distress unrelated to her pattner's drinking severity was most associated with her own marital satisfaction, whereas marital adjustment of female partners of Late-Onset alcoholics was most associated with the male's level of perceptual accuracy regarding her needs. This pattern was reversed for the males; marital adjustment of Early-Onset alcoholics was most associated with his partner's perceptual accuracy of his needs, whereas marital functioning of Late-Onset alcoholics was best accounted for by his own psychological distress.  相似文献   
59.
60.
This review refers to the evolution of ooplasmic injectionsof round spermatid nuclei ROSNI) or intact round spermatidsROSI). Conclusions from their preliminary application in thehamster, rabbit, mouse and human are discussed. Criteria foridentification of round spermatids and guidelines/quality controlfor application of ROSNI/ROSI techniques are emphasized. Althoughall the animal offspring and the human newborns delivered afterROSNI/ROSI are healthy additional research efforts are necessaryto confirm the safety of these procedures and improve theiroutcome  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