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   6095篇
  免费   567篇
  国内免费   11篇
耳鼻咽喉   31篇
儿科学   219篇
妇产科学   210篇
基础医学   741篇
口腔科学   254篇
临床医学   626篇
内科学   1205篇
皮肤病学   153篇
神经病学   337篇
特种医学   339篇
外科学   774篇
综合类   171篇
一般理论   9篇
预防医学   739篇
眼科学   91篇
药学   377篇
  1篇
中国医学   6篇
肿瘤学   390篇
  2022年   40篇
  2021年   70篇
  2020年   48篇
  2019年   89篇
  2018年   119篇
  2017年   87篇
  2016年   78篇
  2015年   93篇
  2014年   167篇
  2013年   275篇
  2012年   292篇
  2011年   264篇
  2010年   157篇
  2009年   147篇
  2008年   246篇
  2007年   229篇
  2006年   241篇
  2005年   222篇
  2004年   203篇
  2003年   221篇
  2002年   209篇
  2001年   196篇
  2000年   189篇
  1999年   166篇
  1998年   86篇
  1997年   72篇
  1996年   98篇
  1995年   90篇
  1994年   76篇
  1993年   75篇
  1992年   161篇
  1991年   141篇
  1990年   123篇
  1989年   135篇
  1988年   136篇
  1987年   154篇
  1986年   109篇
  1985年   105篇
  1984年   88篇
  1983年   72篇
  1982年   42篇
  1981年   48篇
  1980年   52篇
  1979年   78篇
  1976年   39篇
  1975年   39篇
  1974年   59篇
  1973年   46篇
  1972年   50篇
  1968年   46篇
排序方式: 共有6673条查询结果,搜索用时 22 毫秒
71.
Six cases of uncommon profunda femoris artery injury are analyzed. One half of the cases were not treated surgically at the time of injury and resulted in chronic arteriovenous fistulas. Even after operative correction, residual symptoms persisted in two of these three cases. The generous use of arteriography is recommended in cases of proximal thigh penetrating injuries to avoid this problem. Either repair or ligation of the injured vessel yielded the same good results. The postoperative hospital stay was short in all instances, ranging from four to eight days, and there were no deaths.  相似文献   
72.
Lung tissue from 13 cases of unexplained non-immunological hydrops fetalis was examined by in situ hybridisation to detect parvovirus. Four specimens contained parvovirus DNA in cells in the blood vessel lumina and alveoli. Twenty six control cases were negative for parvovirus DNA. As there was no known epidemic of parvovirus infection during the study period, this suggests that parvovirus is a relatively common cause of non-immunological hydrops fetalis. In situ hybridisation may have a role in clinical medicine, particularly for retrospective investigations.  相似文献   
73.
There has been much debate about the role of luteinizing hormone (LH) during follicle stimulating hormone (FSH)-treated ovarian stimulation for assisted reproduction, where the endogenous LH is suppressed using a gonadotrophin-releasing hormone analogue. The requirement for LH in oestradiol biosynthesis is established, but other effects of 'insufficiency' are less clear, and little attention has been paid to the specific origin of the FSH used. The aim of this study was to examine the roles of profoundly suppressed circulating LH concentrations in cycles of ovarian stimulation for IVF, which were affected in two large separate cohorts of patients undergoing assisted reproduction. They were stimulated by either purified urinary FSH (MHP) or recombinant human FSH (rFSH). Within each dataset, outcomes were examined with respect to the circulating concentrations of LH in the mid-follicular phase, as plasma samples were stored prospectively, and assayed retrospectively. Patients with profoundly suppressed LH showed much reduced oestradiol concentrations at mid-follicular phase and at human chorionic gonadotrophin administration in cycles treated with either MHP or rFSH. However, gross ovarian response, as became evident by FSH dose demands, duration of stimulation, and also oocyte and embryo yields and embryo cryopreservation were influenced only in cycles treated with MHP. Furthermore, no effect upon pregnancy survival was observed. Thus, it is concluded that there is a demand for additional exogenous LH treatment only in cycles treated with purified urinary FSH where the LH is profoundly suppressed.  相似文献   
74.
Fischer 344 rats, 3 and 26 months of age, were first tested in an eight-arm spatial maze to assess memory function behaviorally. The same animals were then subjected to hippocampal kindling to examine alterations in neuronal plasticity as a function of aging. The results indicated that spatial memory was poorer and hippocampal kindling slower in aged rats than in young ones. Furthermore, there was a striking positive relation between performance in the eight-arm spatial maze and speed of kindling. This finding suggests that age-related deficits in spatial memory and hippocampal kindling reflect decreased efficacy of synaptic transmission in a common neuroanatomical substrate.  相似文献   
75.
Few investigations have looked at behavioral stress outcomes in Alzheimer's caregivers. This study documented concentration deficits to examine behavioral outcomes of stress in 33 Alzheimer's Disease (AD) caregivers and in 33 age-, sex-, and race-matched controls. As hypothesized, caregivers showed less persistence than controls in solving problems from a standard test of problem-solving ability. In addition, caregivers tended to make more errors than controls on a standard proofreading task ( p < .09). In AD caregivers, cognitive deficits (represented by lower scores on problem-solving and concentration tasks) may be representative of a broader deficit in concentration that impairs the ability of caregivers to provide for their own needs and the needs of the family member for whom they are caring.  相似文献   
76.
In the present study we determined whether the endothelium-derived hyperpolarizing factor (EDHF), in addition to its acute effects on vascular tone, activates intracellular signalling pathways other than those associated with Ca2+-dependent K+ channels. EDHF was generated by rhythmic distension of porcine coronary arteries under conditions of combined nitric oxide (NO) synthase/cyclo-oxygenase blockade, and the EDHF-containing luminal incubate was applied to cultured human coronary endothelial or smooth muscle cells. In both cell types, the luminal incubate activated tyrosine kinases, the mitogen-activated protein (MAP) kinases, extracellular signal regulated kinases 1 and 2 (Erk1/2) and p38, as well as protein kinase B/Akt. The constituent responsible for Erk1/2 phosphorylation was identified as a cytochrome P450 (CYP) metabolite, as Erk1/2 activation was attenuated by pretreating the EDHF donor with the CYP 2C inhibitor sulfaphenazole as well as by CYP 2C antisense oligonucleotides. Erk1/2 phosphorylation in detector cells was also observed following the transfer of supernatant from cultured endothelial cells treated with the CYP inducer beta-naphthoflavone. The CYP 2C product 11,12-epoxyeicosatrienoic acid (11,12-EET) also activated tyrosine kinases, Erk1/2 and p38 MAP kinase. Overexpression of CYP 2C8 in native porcine coronary artery endothelial cells resulted in an increase in endothelial 11,12-EET production and Erk1/2 phosphorylation compared to that detected in untreated cells or cells transfected with an antisense CYP 2C8. Endothelial cell number was unaffected by transfection with LacZ or CYP 2C8 antisense but was significantly enhanced in cells overexpressing CYP 2C8. These observations indicate that EDHF/11,12-EET is not simply a vasodilator and that its continuous release under pulsatile conditions in vivo may affect vascular cell signalling and proliferation.  相似文献   
77.
78.
The hormone melatonin is synthesised and secreted from the pineal gland in darkness and triggers the daily and seasonal timing of various physiological and behavioural processes. The Mashona mole-rat, Cryptomys darlingi, lives in subterranean burrows that are completely sealed and is therefore rarely, if ever, exposed to light under natural conditions. Hence, this species is of particular interest for studies on rhythms of melatonin secretion. We investigated how plasma melatonin concentrations of the Mashona mole-rat responded to exposure to a long-term standard photoperiod of 12 h light, 12 h dark (12:12 LD), constant light (LL) and constant dark (DD). In addition, we examined whether plasma melatonin concentration was coupled to locomotor activity. Mashona mole-rats displayed rhythms of plasma melatonin concentration that appeared entrained to the standard LD photoperiod, suggesting that the mole-rat is capable of perceiving and entraining to this photic zeitgeber. Furthermore, under chronic constant lighting conditions (DD, LL), circadian rhythms in plasma melatonin concentration were observed, suggesting the possible existence of an endogenous rhythm. Light suppressed melatonin secretion, but constant light did not abolish the rhythm of plasma melatonin concentration. Between active and non-active animals, no difference in plasma melatonin concentration was found for any of the sequential photoperiods (LD1 DD, LD2, LL), tentatively suggesting that the rhythm of melatonin secretion is uncoupled from that of locomotor activity.  相似文献   
79.
80.
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