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   5238篇
  免费   380篇
  国内免费   12篇
耳鼻咽喉   37篇
儿科学   137篇
妇产科学   62篇
基础医学   806篇
口腔科学   60篇
临床医学   662篇
内科学   1095篇
皮肤病学   63篇
神经病学   377篇
特种医学   237篇
外科学   997篇
综合类   31篇
一般理论   4篇
预防医学   359篇
眼科学   65篇
药学   392篇
中国医学   10篇
肿瘤学   236篇
  2023年   35篇
  2022年   58篇
  2021年   109篇
  2020年   76篇
  2019年   120篇
  2018年   131篇
  2017年   93篇
  2016年   96篇
  2015年   117篇
  2014年   112篇
  2013年   197篇
  2012年   293篇
  2011年   275篇
  2010年   153篇
  2009年   144篇
  2008年   274篇
  2007年   288篇
  2006年   293篇
  2005年   245篇
  2004年   241篇
  2003年   220篇
  2002年   215篇
  2001年   133篇
  2000年   139篇
  1999年   141篇
  1998年   68篇
  1997年   69篇
  1996年   45篇
  1995年   56篇
  1994年   32篇
  1993年   36篇
  1992年   76篇
  1991年   85篇
  1990年   86篇
  1989年   48篇
  1988年   69篇
  1987年   73篇
  1986年   65篇
  1985年   68篇
  1984年   58篇
  1983年   57篇
  1982年   39篇
  1981年   36篇
  1980年   31篇
  1979年   48篇
  1978年   29篇
  1977年   28篇
  1972年   23篇
  1971年   27篇
  1970年   23篇
排序方式: 共有5630条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: This prospective study examined the interaction of clinical course of disease and brain structure with time in schizophrenic patients. METHOD: A total of 21 first-episode schizophrenic patients, 10 patients with other psychiatric disorders and a control group of 9 healthy volunteers had CT at first admission and at reinvestigation 5 years later. RESULTS: At first admission all of the patients had enlarged cortical fissures and sulci compared to controls, and the duration of untreated psychosis was significantly correlated with sulcal enlargement. At reinvestigation, frontal and central brain atrophy had progressed in schizophrenic patients. CONCLUSION: The study indicated that ongoing psychosis and lifetime dose of classical antipsychotics were the main candidates accounting for the finding of progressively disturbed brain structure during the first 5 years of schizophrenia.  相似文献   
42.
43.
This paper reports the results of a stratified, randomized trial of monthly intradermal injections of Glaxo BCG in addition to conventional therapy (surgery, radiotherapy or no treatment) in a consecutive series of 75 men with confirmed bronchial carcinoma. BCG treatment did not significantly prolong survival but had consistenly more effect in prolonging the period in good general condition and in "acceptable" clinical condition. These were significantly prolonged among the BCG patients (all histopathologies) treated with a full course of radiotherapy (p = 0.01, p = 0.005) and among the 43 patients with squamous carcinoma after adjustment for treatment and general prognostic factors (ratio of observed to expected deaths (O/E) for BCG 0.65, P = 0.025). There was a tendency for BCG patients with oat cell carcinoma to survive less well than controls (O/E for BCG 1.40 not significant). Within comparable groups of patients with squamous carcinoma the delay in decline of general condition was accompanied by reduced weight loss.  相似文献   
44.
An expert system is a computer program which uses artificial intelligence to make logical decisions on the basis of input data. The rules the system uses to make its decisions are called heuristics which can be provided in the form of IF . . . THEN statements, or they can be learned by the system from examples. The term "expert" is used because the rules or examples come from human experts and the program is considered to have captured their expertise. Currently there are many expert systems in business and medical use but few, if any, are used in optometry. The rule-oriented nature of many ophthalmic procedures suggests a future role for these systems, but their cost-effectiveness may not yet be favorable enough to justify development of expert systems for optometric practice.  相似文献   
45.
Determination of glomerular size-selectivity in the normal rat with Ficoll.   总被引:6,自引:0,他引:6  
Diffusion studies in vitro indicate that Ficoll behaves more like an ideal spherical molecule than does dextran, suggesting that Ficoll would be a better probe of glomerular pore size than the commonly used dextran. To examine the differences between these macromolecules in vivo, the fractional clearances of tritiated Ficoll and dextran were measured over a wide range of molecular sizes (Stokes-Einstein radius, rs, from 19 to 65 A) in normal euvolemic Munich-Wistar rats. Whole-kidney and single-nephron hemodynamic conditions were characterized through a combination of clearance and micropuncture measurements. The fractional clearance, or sieving coefficient (theta), for dextran significantly exceeded that of Ficoll at all molecular sizes examined, theta for dextran being approximately 10 times that for Ficoll for rs greater than 30 A. Thus, the results with Ficoll imply a more size-restrictive barrier than do the results with dextran. The values of theta for Ficoll approximated previously reported values for uncharged globular proteins. Although theta for Ficoll at rs = 35 A was much smaller than the corresponding value for dextran, it was still approximately 30 times greater than typical values of the filtrate-to-plasma concentration ratio reported for serum albumin (a polyanion) in the rat, in agreement with the concept that glomerular charge-selectivity normally plays an important role in the prevention of albuminuria. Three membrane-pore models were compared in their ability to represent the dextran and Ficoll sieving data. A lognormal pore-size distribution in parallel with a nonselective "shunt" pathway was found to be more effective than either an isoporous membrane with a shunt or a purely lognormal distribution. On the basis of these laboratory results and computations, Ficoll may be preferred over dextran in future studies of glomerular size-selectivity.  相似文献   
46.
47.
A general method of confocal laser scanning microscopy was used to demonstrate specific binding of fluorescein-labeled naloxone (FNAL, 10-50 nM) to stably transfected mu opioid receptors on live Chinese hamster ovary cells. Nonspecific binding was visually indistinguishable from autofluorescence in cells with intact cell membranes. Fluorescent labeling of cell perimeters, not present in control nontransfected cells, reversed in transfected cells upon washout of FNAL or following the addition of either unlabeled naloxone (25 microM) or the mu specific antagonist CTOP (1 microM). The addition of the delta and kappa specific agonists DPDPE (1 microM) and U50488 (1 microM), respectively, failed to reverse the labeling. Further evidence of specific binding was obtained from kinetic experiments, where it was observed that only transfected cells showed a time-dependent exponential change in fluorescence that permitted estimation of association and dissociation binding rate constants of (5.8+/-0.5, mean+/-S.E.M.)x10(5) M(-1) s(-1) and (3.3+/-0.6)x10(-3) s(-1), respectively and a kinetically derived dissociation constant of 5.7+/-1.4 nM. These estimates were comparable to those obtained under similar conditions in radioligand binding experiments using [3H]-naloxone.  相似文献   
48.
ObjectiveThe aim of this study was to explore the acceptability of bacterial STI vaccines among young HPV-vaccinated Canadian women to inform future vaccine program implementation.MethodsA 20-item cross-sectional questionnaire was administered from June 2019 to June 2020 to HPV-vaccinated participants of the pan-Canadian QUEST cohort. Multivariable logistic regression models assessed interest in chlamydia, syphilis, and gonorrhea vaccines using a priori variables and factors significant in bivariate analysis.ResultsOf the 1092 respondents analyzed, 82% indicated interest in receiving one or more future STI vaccines. Respondents had a median age of 19.6 years (range 16.9–23.4), and 75% of respondents identified as white/European descent. In adjusted analyses, intent to engage in positive health behaviours was associated with vaccine interest for syphilis (OR = 5.76, 95% CI 4.03–8.27), chlamydia (OR = 5.27, 95% CI 3.66–7.63), and gonorrhea (OR = 5.96, 95% CI 4.15–8.60). Willingness to pay for an STI vaccine was also associated with vaccine interest for syphilis (OR = 2.02, 95% CI 1.29–3.19), chlamydia (OR = 2.41, 95% CI 1.50–3.90), and gonorrhea (OR = 2.29, 95% CI 1.44–3.63). Ever having sexual intercourse and identifying as LGBTQ were significantly associated with vaccine interest for all infections, while age and ever being immunosuppressed were not significant in any adjusted models.ConclusionFindings indicate over 80% of participants in a cohort of young HPV-vaccinated Canadian women are interested in receiving future bacterial STI vaccines. Further exploration of STI vaccine acceptability among diverse populations is required to inform future bacterial STI vaccine program implementation.Supplementary InformationThe online version contains supplementary material available at 10.17269/s41997-022-00648-2.  相似文献   
49.
50.
Objective: The purpose of the study was to investigate the effect of route of administration of erythropoietin (EPO) on the dose requirement in dialysis patients after intravenous (IV) and subcutaneous (SC) therapy. Methods: The study was performed as a single centre, prospective, open, combined parallel and cross-over study of 50 dialysis patients, consecutively randomised to IV or SC treatment with EPO. The initial dose was 40 U⋅kg−1 3-times weekly, adjusted to increase haemoglobin (Hgb) from a median 5.3 mmol⋅l−1 to a target of haemoglobin 6.5–7.5 mmol⋅l−1. After reaching the target level, the haemoglobin was maintained for 4 months (Period 1). Then IV and SC treatment was switched for a further 4 months (Period 2). The study included high risk patients. The adjustment period was completed by 38 patients, Period one by 32 patients (IV/SC = 15/17; male/female = 19/13; age = 54 (24– 71) y), and Period two by 22 patients. Results: No significant difference was found between the two groups in the reticulocyte response, the rate of Hgb increase (IV 0.7 versus SC 0.5, mmol⋅l−1⋅ month−1), time to reach target level (IV 43 versus SC 60 days), or total EPO dose per increase in haemoglobin to target level (IV 663 versus SC 946 (U⋅kg−1) per (mmol Hgb⋅l−1). The overall median maintenance dose during the last month of the two four month periods was 105 (range IV 51–336) U⋅kg−1⋅w−1 and SC 104 (range 21–321) U⋅kg−1⋅w−1. Trough serum EPO levels were significantly higher during SC treatment. The blood pressure did not change significantly from the base level after either route of administration; start 133/80 versus 143/80 mmHg, target 127/78 versus 154/85 mmHg, and maintenance period 140/84 versus 142/85 mmHg. Thus, three-times weekly IV or SC EPO did not differ significantly in efficacy or in the effect on blood pressure in dialysis patients. Received: 13 June 1995/Accepted in revised form: 30 October 1995  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