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   44006篇
  免费   2278篇
  国内免费   145篇
耳鼻咽喉   598篇
儿科学   2830篇
妇产科学   757篇
基础医学   5330篇
口腔科学   1172篇
临床医学   3105篇
内科学   7876篇
皮肤病学   1205篇
神经病学   2627篇
特种医学   1253篇
外科学   6520篇
综合类   1431篇
一般理论   21篇
预防医学   2367篇
眼科学   1543篇
药学   4465篇
  1篇
中国医学   373篇
肿瘤学   2955篇
  2023年   353篇
  2022年   1062篇
  2021年   1747篇
  2020年   959篇
  2019年   1070篇
  2018年   1488篇
  2017年   1080篇
  2016年   1422篇
  2015年   1459篇
  2014年   2119篇
  2013年   2396篇
  2012年   3404篇
  2011年   3333篇
  2010年   1996篇
  2009年   1563篇
  2008年   2280篇
  2007年   2277篇
  2006年   2117篇
  2005年   1838篇
  2004年   1744篇
  2003年   1480篇
  2002年   1253篇
  2001年   879篇
  2000年   812篇
  1999年   680篇
  1998年   310篇
  1997年   244篇
  1996年   242篇
  1995年   204篇
  1994年   172篇
  1993年   160篇
  1992年   403篇
  1991年   369篇
  1990年   390篇
  1989年   387篇
  1988年   327篇
  1987年   260篇
  1986年   262篇
  1985年   256篇
  1984年   200篇
  1983年   160篇
  1982年   79篇
  1981年   88篇
  1980年   87篇
  1979年   131篇
  1978年   83篇
  1977年   98篇
  1976年   73篇
  1973年   80篇
  1971年   72篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A high incidence of increased plasma level of high density lipoprotein cholesterol (HDL-C) has been reported in cases of lepromatous leprosy. HDL-C levels were estimated in 96 (50 under treatment and 46 untreated) lepromatous leprosy patients and 84 randomly selected matched control patients suffering from other skin diseases attending skin out-patients department. HDL-C estimations were performed for the diagnosis of lepromatous leprosy in patients aged below 60 years, taking plasma HDL-C levels as 28-71 mg./dl. in men and 34-91 mg./dl. in women, as range of normal values. The study revealed that HDL-C levels in lepromatous leprosy group were raised and significantly different when compared with control group (t = 35.1668 and P less than 0.001). The sensitivity of the test was very high, 97.9 per cent (94/96), but specificity was low 80.95 per cent (68/84). False positive and false negative results were 19.04 per cent (16/84) and 2.08 per cent (2/96) respectively. It is opined that a negative test will be mainly useful in excluding diagnosis of lepromatous leprosy.  相似文献   
52.
Endothelin receptors (ETRs) display subtype heterogeneity and are widely distributed throughout the tissues of the periphery and central nervous system. In order to gain further insight into the potential molecular differences of ETRs, we initiated molecular cloning of ETR genes by screening for the appearance of 125I-ET-1 binding activity in COS cells transfected with pools of a porcine cerebellum cDNA expression library. Two independent clones (pPCETR 1.1 and pPCETR 5.6) were identified and isolated by repeated rounds of pool enrichment and COS cell expression. DNA sequence analysis of pPCET 1.1 and pPCET 5.6 indicated that both clones have the same nucleotide sequence; the deduced amino acid sequence indicated that the porcine cerebellum ETR is 443 residues in length and consists of seven potential transmembrane domains, with homology to members of the GTP-binding protein-coupled receptor superfamily. Northern analysis indicated a single mRNA species of about 5 kilobases, which is expressed significantly in cerebellum, lung, kidney, and pituitary. Expression of functional receptor was demonstrated by endothelin-1 (ET-1)-mediated Ca2+ mobilization in COS cells transfected with pPCETR 1.1 (COS/ETR 1.1) and ET-1-mediated electrophysiological responses in Xenopus oocytes injected with RNA derived from pPCETR 1.1. Quantitative comparison of saturation binding of 125I-ET-1 to either porcine cerebellum or COS/ETR 1.1 membranes indicated an identical apparent dissociation constant. The relative efficacy of ET-related peptides to compete for binding of 125I-ET-1 to receptor from porcine cerebellum and COS/ETR 1.1 indicated that both preparations encode a nonselective or ETBR subtype. Chemical cross-linking of 125I-ET-1 to receptor derived from cerebellum or COS/ETR 1 revealed two bands, with apparent molecular masses of 47 and 35 kDa. These data demonstrate that the pPCETR 1.1 encodes the major ETR subtype in the porcine cerebellum.  相似文献   
53.
In the present work we report our studies on IgG separated from the serum of lepromatous patients and non-lepromatous leprosy cases using Laser Raman Spectroscopy. Striking spectral changes in LL cases have been observed in the following special regions: (a) the amide I and III, (b) the S-S and C-S stretching (c) the skeletal bending and (d) skeletal stretching regions. These changes indicate a decrease in the amount of beta-structure and a transition towards alpha-helical conformation.  相似文献   
54.
P G Joshi  S Mishra 《Brain research》1992,597(1):108-113
Expression of galactocerebroside (GalC) was detected in human glioma cell line (U-87 MG). Exposure of cells to antibody against GalC and fluoresceinated second antibody showed intense fluorescence on the plasma membrane. Possible involvement of GalC in receptor-mediated transmembrane signaling was explored in this cell line. Antibodies raised against GalC were used as ligands. Binding of anti-GalC to these cells caused a transient increase in intracellular free calcium ([Ca2+]i). The response was observed both in the presence and absence of extracellular calcium demonstrating that the rise in [Ca2+]i induced by anti-GalC was due to an influx of Ca2+ through plasma membrane as well as the release of Ca2+ from intracellular pools. Ca2+ influx was blocked by verapamil, indicating that influx is mediated by voltage-sensitive channels. Our results suggest that GalC can play a role in transmembrane signaling by modulation of voltage-sensitive Ca2+ channels.  相似文献   
55.
The alterations in the oesophageal epithelium were studied in mice after a single whole-body exposure to 7.5 Gy of Co-60 gamma rays in presence or absence of 2-mercaptopropionyl glycine. The epithelium showed an increase in the thickness which reached a maximum on the third day and then decreased gradually up to seventh day after irradiation in the non-drug treated group. In the 2-mercaptopropionyl glycine treated animals the epithelial thickness remained in the normal range except on the day 7 when it was significantly lower than normal. The total cell population registered a steady decline from one to seven days post-irradiation in both groups, but the number of cells was more in the 2-mercaptopropionyl glycine treated group. The number of pycnotic nuclei showed an inverse relationship to the total cell population, it increased continuously up to seven days in both the protected and non-protected groups. However, pycnotic nuclei were significantly lower in the protected group on days 3, 5 and 7 in non-protected group.  相似文献   
56.
Regularity of DDS intake among 366 leprosy patients attending our out patient department voluntarily was assessed by urine spot test. It was found that only 54.6% of them had taken their last dose of drug within the previous three days. Those who kept their appointment showed better compliance than those who did not. Urinary DDS positivity was found to be unrelated to sex, occupation or the type of the disease. In the younger age group the compliance was low, as also among the patients coming from nearby places as compared to those who were residing in far off districts.  相似文献   
57.
Cytogenetics or the study of chromosomes has been an important tool in oncology. It localizes the abnormality on a particular chromosome segment as such but, the molecular analysis on the other hand focuses the exact gene of interest. Hence both are complimentary. Classical cytogenetics in combination with recent molecular techniques has given rise to various molecular cytogenetic analytical techniques such as florescent in-situ hybridization (FISH), spectral karyotyping (SKY) and comparative genomic hybridization (CGH). The role of telomeres and its concerned enzyme telomerase is important in carcinogenesis. This article summarizes the various cytogenetic techniques and presents an overall view of the importance of cytogenetcs in head and neck cancer.  相似文献   
58.
59.
Diagnosis of dementia needs to be complemented by precise determination of disease severity across the broad spectrum of disease progression. The Mini-Mental State Exam (MMS), the Activities-of-Daily-Living assessment (ADL) and the Clinical Dementia Rating scale (CDR) were modified for direct comparability and administered to 112 outpatients and 45 nursing home residents with a range of dementia severity from mild to profound. The scales showed the highest correlations for the probable Alzheimer's disease patient group (62) (Global Assessment of Dementia; GAD vs. ADL: r = 0.91; Extended Mini-Mental Assessment; EMA vs. GAD: r = 0.91; ADL vs. EMA: r = 0.86). For these patients, scores on the individual scales tended to be similar. Disparity among the three scores for individual cases was associated with the presence of comorbidities. The high correlations and correspondence among these scales demonstrate their reliability, validity, and utility in the assessment of dementia severity. The use of an average of these measures, with their increased precision, may give a more accurate indication of dementia severity over a broader range of impairment.  相似文献   
60.
Intracellular sodium in proximal tubules of diabetic rats. Role of glucose   总被引:1,自引:0,他引:1  
Renal hypertrophy is a common consequence of diabetes mellitus that precedes and possibly accounts for the increased glomerular filtration rate. We have postulated that the glucose-mediated increase in the intracellular concentration of sodium [Na]i initiates the chain of events leading to the increase in cell size and eventually cell number. Experiments were conducted on Sprague-Dawley rats made diabetic by the intravenous injection of 45 mg/kg body wt of streptozotocin dissolved in a 5 mM citrate buffer solution. Control animals were injected with the vehicle alone. Ninety-six hours and 11 weeks later, measurements of [Na]i were done by NMR spectroscopy on suspensions of proximal tubules, using dysprosium tripolyphosphate as an extracellular shift reagent. At 96 hours after the induction of the diabetes, there was a 60% increase in [Na]i compared to control (P less than 0.01). No further increase in [Na]i was observed during the subsequent 11 weeks of observation. Addition of ouabain (1.0 mM) resulted in a fourfold increase in [Na]i in tubules from control animals, and a 2.5-fold increase in tubules from 96-hour diabetic rats. Ouabain-inhibitable Na+-K+-ATPase activity was substantially higher in the renal tubules of diabetic rats, the increase being proportional to that of [Na]i. In order to ascertain the effect of hyperglycemia on [Na]i, proximal tubules prepared from kidneys of normal and diabetic rats were exposed to low (5 mM) and high (25 mM) concentration of glucose in the media.(ABSTRACT TRUNCATED AT 250 WORDS)  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