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   7102篇
  免费   451篇
  国内免费   29篇
耳鼻咽喉   56篇
儿科学   156篇
妇产科学   92篇
基础医学   1041篇
口腔科学   146篇
临床医学   464篇
内科学   1796篇
皮肤病学   294篇
神经病学   506篇
特种医学   153篇
外科学   929篇
综合类   22篇
一般理论   1篇
预防医学   351篇
眼科学   169篇
药学   522篇
中国医学   15篇
肿瘤学   869篇
  2023年   42篇
  2022年   60篇
  2021年   194篇
  2020年   129篇
  2019年   128篇
  2018年   189篇
  2017年   152篇
  2016年   173篇
  2015年   157篇
  2014年   212篇
  2013年   309篇
  2012年   445篇
  2011年   481篇
  2010年   258篇
  2009年   237篇
  2008年   455篇
  2007年   489篇
  2006年   444篇
  2005年   450篇
  2004年   437篇
  2003年   385篇
  2002年   363篇
  2001年   120篇
  2000年   124篇
  1999年   143篇
  1998年   70篇
  1997年   68篇
  1996年   47篇
  1995年   46篇
  1994年   34篇
  1993年   45篇
  1992年   71篇
  1991年   63篇
  1990年   52篇
  1989年   54篇
  1988年   58篇
  1987年   52篇
  1986年   45篇
  1985年   30篇
  1984年   32篇
  1983年   20篇
  1982年   13篇
  1979年   20篇
  1978年   15篇
  1974年   13篇
  1973年   14篇
  1969年   13篇
  1968年   14篇
  1967年   15篇
  1966年   19篇
排序方式: 共有7582条查询结果,搜索用时 31 毫秒
81.
The androgens testosterone and dihydrotestosterone (DHT) are essential for a variety of systemic functions in mature males. Alteration of these hormones results in late-onset hypogonadism (LOH) and benign prostate hyperplasia (BPH). The fruit bodies of fungi of the genus Cordyceps have been regarded as folk medicine or health food with tonic and antifatigue effects. The extract from the fruit body of Cordyceps militaris parasitizing Samia cynthia ricini (CM) was evaluated as a novel-candidate natural product for ameliorating male andropause symptoms. To explore the effects of CM on LOH and BPH, CM was applied to rat models and cultured testicular cells and prostate cells. The concentrations of androgens in the serum and culture media were determined by ELISA. Expression of steroidogenic enzymes and androgen-related genes was evaluated by qPCR, and prostatic cell proliferation was assessed with the cell-viability assay. CM maintained the serum levels of testosterone and DHT, but inhibited testosterone-induced prostate hypertrophy. CM also increased the secretion of testosterone and DHT by primary testicular cells, with no changes in the mRNA expression of steroidogenic enzymes, but decreased the growth of prostatic cell lines. Our data suggest that CM could improve both LOH and BPH in males.  相似文献   
82.
Osteopenia/osteoporosis and sarcopenia are common geriatric diseases among older adults and harm activities of daily living (ADL) and quality of life (QOL). Osteosarcopenia is a unique syndrome that is a concomitant of both osteopenia/osteoporosis and sarcopenia. This review aimed to summarize the related factors and clinical outcomes of osteosarcopenia to facilitate understanding, evaluation, prevention, treatment, and further research on osteosarcopenia. We searched the literature to include meta-analyses, reviews, and clinical trials. The prevalence of osteosarcopenia among community-dwelling older adults is significantly higher in female (up to 64.3%) compared to male (8–11%). Osteosarcopenia is a risk factor for death, fractures, and falls based on longitudinal studies. However, the associations between osteosarcopenia and many other factors have been derived based on cross-sectional studies, so the causal relationship is not clear. Few studies of osteosarcopenia in hospitals have been conducted. Osteosarcopenia is a new concept and has not yet been fully researched its relationship to clinical outcomes. Longitudinal studies and high-quality interventional studies are warranted in the future.  相似文献   
83.
84.
Summary An electron spin resonance (ESR) method already in use for the quantitative analysis of paraquat was applied to the analysis of diquat in blood, serum, urine, tissue homogenates and several drinks without purification of the samples. The diquat radical produced with ascorbic acid at alkaline pH was much more stable than that produced with the commonly used sodium dithionite. Radical decay in solutions covered with n-hexane was less than 5% after 60 min over a wide range of ascorbic acid concentrations. In 0.2N NaOH solution 85% of the radicals was present even after 24h. The limit of detection was 0.3 g/ml and the required amount of sample was 0.1 ml. When both diquat and paraquat were present in a sample the diquat was first extracted with 1-butanol prior to the ESR measurement, because both species were converted to the radicals.  相似文献   
85.
The present study was performed to evaluate postoperative hoarseness quantitatively by means of acoustic wave form analysis. Pitch and amplitude perturbation (PPQ, and APQ), and normalized noise energy (NNE) were measured along with the frequency characteristics in 51 adult patients undergoing elective surgery. The normal values for these acoustic parameters were less than 0.5%, less than 2.0%, and less than -10 dB, respectively. Vowel sound "E" was recorded and evaluated before the induction of anesthesia and on the morning of the day after the surgery. PPQ increased from 0.39% to 1.00% (P less than 0.05), APQ increased from 3.34% to 6.62% (P less than 0.05), and NNE increased from -9.19 dB to -4.74 dB (P less than 0.05). Eighteen percent of the patients showed abnormal values in all parameters preoperatively, but 45% of the patients postoperatively (P less than 0.05). These findings suggest that even the short term intubation resulted in the postoperative hoarseness, and this method is a useful and non-invasive bed-side test to evaluate postoperative hoarseness quantitatively.  相似文献   
86.
Summary The effects of morphine-HCl (MOR), methionine-enkephalin (ME) and dynorphin1–13 (DYN) on spinal and spino-bulbo-spinal (SBS) reflexes were studied. Although spinal intrathecal administration of MOR (15g) did not produce any apparent effect on these reflexes, systemically administered MOR (3mg/kg i.v.) reduced the electrical toe stimulation-induced SBS reflex. Furthermore, MOR (3mg/kg i.v.) increased the polysynaptic reflex induced by electrical stimulation of low-threshold dorsal root afferents in intact (non-spinal) rats, but not in spinal rats. Intrathecally administred DYN (0.5 and 5 g) reduced both the electrical toe stimulation-induced spinal and SBS reflexes, while ME (15g) only reduced the SBS reflex. These results indicate the physiological multiplicity of spinal opioid receptors. MOR may affect supraspinal nuclei but not the spinal pathway which possesses MOR-sensitive opioid receptors, whereas ME and DYN affect spinal opioid peptide receptors and modulate the reflex activities in which they participate.  相似文献   
87.
The effect of calcium-balanced heparin (471896, CIBA CORNING) on blood gas and electrolyte analysis was evaluated, by comparing with that of sodium heparin (Na heparin). One ml of whole blood was collected into a syringe, which contained calcium-balance heparin (Ca balanced heparin) or Na heparin. 122 pairs of blood samples obtained from 15 patients were analyzed for Na, K, ionized calcium (Ca(++)), total hemoglobin, pH, P(CO)(2), and P(O)(2) by an automatic blood gas and electrolyte analyzer, CIBA CORNING model 288. There was a significant difference ( P < 0.05) in pH, P(CO)(2), Na, and Ca(++) between the two different groups. Ca(++) concentration was significantly less in Na heparin group than in Ca balanced heparin group, probably due to more chelation of Ca(++) by Na heparin than Ca balanced heparin. The present study suggests that the Ca balanced heparin has minimal effect on the blood gas and electrolyte analysis, and is a suitable anticoagulant for the Ca(++) measurement.  相似文献   
88.
  1. The aim of this study was to determine whether BAYw6228 (BAYw), a newly developed 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitor, could suppress an atherogenic process such as intimal thickening by a mechanism other than lowering the level of serum cholesterol.
  2. First, we evaluated the in vitro effect of BAYw on the proliferation of vascular smooth muscle cells (SMC) from various species: Sprague-Dawley (SD) rats, New Zealand (NZ) white rabbits, intimal cells from Watanabe hereditary hyperlipidemic (WHHL) rabbit and SMC from the new-born human aorta. The increasing rate of total protein content of these cells was inhibited by the addition of BAYw in a dose-dependent fashion. In the presence of 2% foetal calf serum (FCS), the value of IC50 was 1.0 μM in SD rats. 2.1 μM in NZ white rabbits, and 0.3 μM in WHHL rabbits. With human SMC, the value was 0.02 μM in the presence of 10% FCS and 0.2 μM with a mixture of growth factors.
  3. Based on these above in vitro findings, we next examined the in vivo effect of the agent to determine whether it could suppress rabbit intimal thickening induced by balloon catheterization. A balloon catheter was inserted from a peripheral branch of the left external carotid artery to the aorta to denude the endothelium of the left common carotid artery in Japanese white rabbits. After 12 days they were divided into control and BAYw groups. The former were subcutaneously injected with saline and the latter with BAYw 1 mg kg−1 day−1. Two days after the beginning of treatment, a second balloon injury was performed to the previously injured left common carotid artery in both groups. After another two weeks, the left common carotid artery was removed and variously stained. Although the total serum cholesterol in the BAYw group was significantly lower than in the control (P<0.05), the difference was not enough to affect intimal thickening. In addition, the BAYw group had a smaller intima/media ratio than the control group, decreasing to 45% of control (P<0.05). By anti-α smooth muscle actin antibody staining, these intimal thickening areas were entirely occupied by SMCs, and their amount was attenuated by BAYw. By anti-rabbit macrophage antibody (RAM 11) staining, the number of positive cells in the intimal thickening was markedly decreased in the BAYw group compared to control (P<0.01).
  4. These results indicate that BAYw has an inhibitory effect on intimal thickening by attenuating intimal SMC proliferation and infiltration of macrophages, suggesting that BAYw could be effective in the prevention of the progression of atherosclerotic plaque-like restenosis after angioplasty.
  相似文献   
89.
  1. A murine anti-human vWF monoclonal antibody, AJvW-2, was developed that inhibited the interaction between platelet glycoprotein Ib (GPIb) and von Willebrand factor (vWF) during the ristocetin- (IC50=0.7±0.1 μg ml−1) and botrocetin- (IC50=1.8±0.3 μg ml−1) induced aggregation of human platelets.
  2. AJvW-2 inhibited the high shear stress (10.8 N m−2) induced aggregation of human platelets dose-dependently with an IC50=2.4±0.3 μg ml−1, but had no effect on low shear stress induced platelet aggregation (1.2 N m−2) up to 100 μg ml−1.
  3. AJvW-2 also inhibited the high shear stress (5.0 N m−2) induced adhesion of human platelets to collagen I with the same efficacy (IC50=2.4±0.3 μg ml−1), but had no effect at low shear conditions (1.5 N m−2).
  4. AJvW-2 inhibited the botrocetin-induced aggregation of platelets from guinea-pig, rat, rabbit, dog and pig at the same concentration range as human platelets; it likewise also inhibited the high shear stress induced aggregation and adhesion to collagen I of guinea-pig platelets.
  5. AJvW-2 prevented arterial thrombus formation in guinea-pigs at a dose of 100 μg kg−1 without prolonging the template bleeding time, whereas the GPIIb/IIIa antagonist lamifiban mediated inhibition of thrombosis at 1000 μg kg−1 was accompanied by a significant prolongation of the bleeding time.
  6. These results suggest that AJvW-2 is a potent inhibitor of the GPIb-vWF interaction and a potential novel antithrombotic agent with lower bleeding risk than GPIIb/IIIa antagonists.
  相似文献   
90.
In this cross-sectional study, the relationships of the physiological levels of estradiol (E2) and dehydroepiandrosterone-sulfate (DHEA-S) to the lipid and lipoprotein profiles were investigated in 212 apparently healthy men aged from 18 to 59 years old. These subjects were divided into tertiles according to the levels of E2 and DHEA-S, respectively. We performed one-way analysis of variance and analysis of co-variance controlling for age, body mass index, percent body fat, waist to hip ratio, maximal oxygen uptake, alcohol and cigarette consumptions as confounding factors.A lower E2 level was associated with higher concentrations of total cholesterol (TC) and low density lipoprotein cholesterol. A lower DHEA-S level was associated with a lower concentration of high density lipoprotein cholesterol (HDLC) and a higher ratio of TC / HDLC. These correlations remained significant after adjusting for the above confounding factors. Neither free testosterone nor sex hormone-binding globulin was associated with the lipids and lipoproteins. These results suggest that higher levels of E2 and DHEA-S, at least in physiological concentrations, are related to the favorable lipid and lipoprotein levels in men.  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