全文获取类型
收费全文 | 2276篇 |
免费 | 108篇 |
国内免费 | 47篇 |
专业分类
耳鼻咽喉 | 100篇 |
儿科学 | 75篇 |
妇产科学 | 94篇 |
基础医学 | 218篇 |
口腔科学 | 53篇 |
临床医学 | 207篇 |
内科学 | 339篇 |
皮肤病学 | 21篇 |
神经病学 | 369篇 |
特种医学 | 239篇 |
外国民族医学 | 11篇 |
外科学 | 326篇 |
综合类 | 39篇 |
预防医学 | 137篇 |
眼科学 | 9篇 |
药学 | 103篇 |
中国医学 | 3篇 |
肿瘤学 | 88篇 |
出版年
2022年 | 14篇 |
2021年 | 27篇 |
2020年 | 19篇 |
2019年 | 16篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 35篇 |
2015年 | 53篇 |
2014年 | 72篇 |
2013年 | 124篇 |
2012年 | 85篇 |
2011年 | 91篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 79篇 |
2007年 | 121篇 |
2006年 | 76篇 |
2005年 | 72篇 |
2004年 | 77篇 |
2003年 | 69篇 |
2002年 | 67篇 |
2001年 | 78篇 |
2000年 | 67篇 |
1999年 | 76篇 |
1998年 | 40篇 |
1997年 | 49篇 |
1996年 | 40篇 |
1995年 | 36篇 |
1994年 | 36篇 |
1993年 | 24篇 |
1992年 | 45篇 |
1991年 | 41篇 |
1990年 | 29篇 |
1989年 | 48篇 |
1988年 | 43篇 |
1987年 | 34篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 18篇 |
1980年 | 17篇 |
1979年 | 22篇 |
1977年 | 13篇 |
1976年 | 19篇 |
1975年 | 12篇 |
1973年 | 13篇 |
1969年 | 13篇 |
1968年 | 13篇 |
排序方式: 共有2431条查询结果,搜索用时 15 毫秒
991.
Controlled comparison of percutaneous and microsurgical sperm retrieval in men with obstructive azoospermia 总被引:3,自引:2,他引:1
Sheynkin YR; Ye Z; Menendez S; Liotta D; Veeck LL; Schlegel P 《Human reproduction (Oxford, England)》1998,13(11):3086-3089
A controlled comparison of the efficacy and reliability of sperm retrieval
by testicular fine needle aspiration (TFNA), percutaneous testicular needle
biopsy (PercBiopsy) and microsurgical epididymal sperm aspiration (MESA)
was performed in nine patients with obstructive azoospermia. During a
planned MESA procedure, sperm retrieval was attempted on the same testis
with TFNA and PercBiopsy. Spermatozoa were obtained from all patients using
MESA and PercBiopsy. Spermatozoa were retrieved using TFNA from 6/9 (67%)
men. The mean number of epididymal spermatozoa retrieved with MESA (15 x
106) was significantly higher (P = 0.003) than that retrieved
percutaneously from the testis. The mean number of spermatozoa obtained by
PercBiopsy was 0.116 x 10(6) while TFNA recovered 0.014 x 106 spermatozoa
(P = 0.025). MESA is the optimal choice to retrieve the greatest number of
spermatozoa with highest motility for assisted reproduction and subsequent
cryopreservation. However, percutaneous testicular retrieval does not
require microsurgical expertise and is less invasive. Our results suggest
that the optimal percutaneous procedure for sperm retrieval from the testis
involves percutaneous testicular needle biopsy with an automatic biopsy
gun.
相似文献
992.
Endometrial vascular and glandular expression of integrin alpha(v)beta3 in women with and without endometriosis 总被引:8,自引:3,他引:5
The integrin alpha(v)beta3 functions in both cell-cell and cell-
extracellular matrix adhesion, and has reported roles in platelet
aggregation, immune function, tissue repair, tumour invasion, angiogenesis
and uterine receptivity. The aim of this study was to use
immunohistochemistry to describe the vascular and glandular expression of
integrin alpha(v)beta3 in formalin fixed, paraffin embedded endometrium
obtained from women with (n = 29) and without (n = 24) endometriosis. The
results showed a significant increase in the percentage of vessels
expressing alpha(v)beta3 in the endometrium of women with endometriosis
compared with controls (P = 0.0001). This difference was more pronounced in
the secretory phase (P = 0.001) than the proliferative phase (P = 0.016).
There was no correlation between vascular alpha(v)beta3 expression and the
endothelial cell proliferation index (P > 0.05). Vascular sprouts were
not observed in any of the 53 endometrial tissues obtained from women with
or without endometriosis throughout the menstrual cycle. Results from semi-
quantitative scoring of gland immunostaining showed that neither controls
(P = 0.3329) nor the endometriosis group (P = 0.2260) had any significant
changes in terms of alpha(v)beta3 expression between the different stages
of the menstrual cycle. There was also no difference in glandular
alpha(v)beta3 expression between women with and without endometriosis (P =
0.4302). These results provide evidence for increased endometrial
angiogenesis in women with endometriosis compared with controls, and
suggest that glandular expression of alpha(v)beta3 is not related to
uterine receptivity per se.
相似文献
993.
JA Martínez A Bello LL Rubio C Rodríguez L Galán E Caudales and JL Alvarez 《Fundamental & clinical pharmacology》1998,12(2):182-187
Summary— The alkaloid cycleanine ([12aR-(12aR,24aR)]-2,3,12a,13,14,15,24,24a-octahydro-5,6,17,18-tetramethoxy-1,13-dimethyl-8,11: 20,23-dietheno-1H,12H [1,10]dioxacyclooctadecino[2,3,4-ij: 11,12,13-i'j']diisoquinoline) was extracted from the bulbs of Stephania glabra (Roxb) Miers and its effects on cardiac and smooth muscle preparations were studied and compared to those of nifedipine (1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridine dicarboxylic acid dimethylesther). Cycleanine inhibited the KCl-induced contraction of rabbit aortic rings with higher potency than nifedipine. IC50s for cycleanine and nifedipine were 0.8 and 7·10−9 M respectively. Cycleanine had minor effects on the norepinephrine-induced contraction of rabbit aortic rings. Cycleanine and nifedipine also depressed the contraction of rat ventricular preparations but with lower potency (IC50 = 3 and 0.03·10−6 M respectively). Action potential duration of rat right ventricular strips was decreased by both compounds. L-type Ca-current (ICaL ) of single rat ventricular cardiomyocytes was inhibited by cycleanine in a voltage- and frequency-dependent manner. With a higher potency nifedipine inhibited ICaL in a tonic and almost frequency-independent manner. The results suggest that cycleanine can act as a potent vascular selective Ca-antagonist. 相似文献
994.
W. LL. PARRY-JONES 《Acta paediatrica (Oslo, Norway : 1992)》1991,80(S373):82-90
Establishing realistic weight goals and their effective use in treatment is an integral part of management in anorexia nervosa. However, the processes involved are discussed rarely in the clinical and research literature. Various methods for setting target weights are reviewed, with consideration of the relative merits of their application in the treatment of pre-pubertal children and adolescents with anorexia nervosa. 相似文献
995.
Prospective study of patients aged 55 years or less with acute myocardial infarction between 1981 and 1985: outcome 7 years and beyond.
下载免费PDF全文
![点击此处可从《Heart (British Cardiac Society)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J. S. Skinner C. J. Albers J. Goudevenos C. Fraser O. Odemuyiwa R. J. Hall P. C. Adams 《Heart (British Cardiac Society)》1995,74(6):604-610
OBJECTIVE--To determine the long-term prognosis of patients after a myocardial infarction (MI) at a young age. DESIGN--Prospective cohort study of patients aged 55 years or less suffering a myocardial infarction. SETTING--A single coronary care unit admitting patients from the community. PATIENTS--255 consecutive patients (210 men) aged 55 years or less admitted between 1981 and 1985 after acute MI. Twenty four patients died in hospital or within 3 months of infarction and 11 were lost to further follow up after discharge. Of the remaining patients, 150 (mean (SD) age 48 (5.7) years) able to exercise 3 weeks after infarction and who agreed to undergo coronary angiography were recruited to a study group and seen 18 months, and 3, 5, and 7 years after MI. In addition, a cross sectional analysis of survival was made to a median of 120 months. Seventy 3 month survivors (mean (SD) age 48 (5.8) years) were not recruited to the study group but were traced for late survival through their general practitioners and family health service associations to a median of 130 months. MAIN OUTCOME MEASURES--Survival in young patients after MI and the survival of 3 month survivors stratified by their ability to exercise and agreement to undergo angiography. The rate of coronary artery surgery (CAGB) and reinfarction during the first 7 years after index MI in patients recruited to the study group. RESULTS--Sixteen patients (6%) died in hospital and eight (3%) within 3 months of the index infarction. The 7 and 11 year survival rates in the whole cohort of 255 patients were 80% and 66% respectively using life table methods. Survival 7 years after MI, in patients recruited to the study group was better than in those not recruited (93% v 79%, P = 0.001), but thereafter mortality in the study group accelerated and there was no significant difference in survival 11 years after infarction (76% v 67%, P = 0.05). There was a trend towards higher mortality in patients with multivessel disease and severely impaired left ventricular function. During the first 7 years after MI, 38 of 150 patients in the study group underwent CABG and 19 suffered reinfarction, which was fatal in three. CONCLUSION--The medium-term prognosis of young survivors of MI is good, particularly in patients recruited to the study group. After 7 years there is an increase in mortality and the long-term prognosis is less favourable. This should be taken into account when planning future management and follow up of young patients after MI. 相似文献
996.
Transcranial Doppler (TCD) examinations are increasingly being used in studies of headache pathophysiology. Because blood velocity is highly dependent on pCO2 , these parameters should be measured simultaneously. The most common way of performing measurements during TCD examinations is as end-tidal pCO2 witch a capnograph. When patients are nauseated and vomit, as in migraine, the mask or mouthpiece connected to the capnograph represents a problem. We therefore evaluated whether a transcutaneous pCO2 electrode was as useful as the capnograph for pCO2 measurements in TCD examinations. We conclude that this is not the case, and recommend capnographic end-tidal pCO2 measurements during TCD examinations. However, transcutaneous pCO2 measurements may represent a supplement to spot measurements of end-tidal pCO2 in stable conditions when long-term monitoring is needed, and the mask or mouthpiece of the capnograph has to be taken on and off between recordings. 相似文献
997.
Ascher SM; Arnold LL; Patt RH; Schruefer JJ; Bagley AS; Semelka RC; Zeman RK; Simon JA 《Radiology》1994,190(3):803
998.
These studies describe the phase I and II metabolism of 7-ethoxycoumarin (7-EC) in the isolated, perfused intestinal loop. Following cytochrome P450-dependent oxidative deethylation of 7-EC by intestinal epithelial cells, the product, 7-hydroxycoumarin (7-HC), undergoes phase II conjugation to form both the glucuronide and sulfate conjugates. The capacity for conjugation of 7-HC within the intestinal epithelium exceeds that of phase I oxidative deethylation, as demonstrated by the absence of increased release of unconjugated 7-HC upon saturation of the conjugation pathways. The formation of both glucuronide (53-62%) and sulfate (41-43%) conjugates contributed to a comparable extent to the overall phase II metabolism of 7-HC within the intestine. This is in contrast to the liver, where sulfate conjugation has been shown to be the predominant phase II metabolic pathway. Furthermore, it was found that unconjugated and sulfate conjugated 7-HC were evenly distributed between the lumenal perfusate and blood compartments, whereas the glucuronide conjugates of 7-HC were preferentially transported at a 4:1 ratio toward the blood. These results indicate that the epithelial cells of the small intestine have the capacity to biotransform orally administered xenobiotics, and the ultimate profile of metabolites generated may influence the biodisposition of these compounds. 相似文献
999.
Clinical practice is often based on the results of research. Critical evaluation of research studies is important if appropriate conclusions are to be drawn. In this series of columns, we review principles of research methodology and statistical analysis. Our intent is to assist certified nurse-midwives in understanding the relative merits of the research they read and use. This article, the first of the series, will review issues pertinent to randomized clinical trials. 相似文献
1000.
Human blood monocytes isolated by centrifugal elutriation were resistant to infection with herpes simplex virus type 1 (HSV). In vitro cultivation for several days resulted in a stepwise increase of virus yield. Similar amounts of virus absorbed to fresh and cultured monocytes. No viral DNA was associated with the nuclear fraction of freshly isolated monocytes early after infection indicating that early steps of virus infection were already inhibited in resistant cells. This argues against HSV induced interferon (IFN) being a major mediator of resistance. Culturing the cells for some hours was sufficient to overcome the early block. However, as revealed by virus yield assays, monocytes after 1 day of cultivation were not as susceptible as cells after 6 days of cultivation. Viral sequences could be demonstrated in the nuclei of freshly isolated monocytes after treatment with the fusion-promoting agent polyethylene glycol. Under these conditions no DNA replication occurred, indicating that overcoming the block of viral DNA entry into the nucleus was not sufficient to break resistance of the cells. Thus, the results show that several mechanisms are involved in the primary resistance of human blood monocytes to HSV. 相似文献