全文获取类型
收费全文 | 8894篇 |
免费 | 769篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 227篇 |
儿科学 | 324篇 |
妇产科学 | 227篇 |
基础医学 | 1087篇 |
口腔科学 | 227篇 |
临床医学 | 996篇 |
内科学 | 1814篇 |
皮肤病学 | 243篇 |
神经病学 | 659篇 |
特种医学 | 502篇 |
外科学 | 1519篇 |
综合类 | 172篇 |
一般理论 | 8篇 |
预防医学 | 676篇 |
眼科学 | 150篇 |
药学 | 346篇 |
中国医学 | 2篇 |
肿瘤学 | 519篇 |
出版年
2021年 | 91篇 |
2019年 | 84篇 |
2018年 | 108篇 |
2017年 | 91篇 |
2016年 | 88篇 |
2015年 | 120篇 |
2014年 | 144篇 |
2013年 | 244篇 |
2012年 | 295篇 |
2011年 | 308篇 |
2010年 | 206篇 |
2009年 | 189篇 |
2008年 | 276篇 |
2007年 | 345篇 |
2006年 | 341篇 |
2005年 | 343篇 |
2004年 | 304篇 |
2003年 | 339篇 |
2002年 | 318篇 |
2001年 | 267篇 |
2000年 | 291篇 |
1999年 | 259篇 |
1998年 | 104篇 |
1997年 | 105篇 |
1996年 | 111篇 |
1995年 | 105篇 |
1994年 | 94篇 |
1993年 | 97篇 |
1992年 | 242篇 |
1991年 | 242篇 |
1990年 | 228篇 |
1989年 | 260篇 |
1988年 | 214篇 |
1987年 | 220篇 |
1986年 | 221篇 |
1985年 | 206篇 |
1984年 | 178篇 |
1983年 | 124篇 |
1982年 | 100篇 |
1981年 | 85篇 |
1979年 | 143篇 |
1978年 | 110篇 |
1976年 | 85篇 |
1975年 | 83篇 |
1974年 | 96篇 |
1973年 | 150篇 |
1972年 | 87篇 |
1971年 | 101篇 |
1970年 | 107篇 |
1969年 | 97篇 |
排序方式: 共有9698条查询结果,搜索用时 15 毫秒
61.
Eighteen male hypertensives on diuretic medication between the ages of 37 and 60 were studied in a double-blind, randomized, crossover design under three conditions: 200 mg of caffeine and mental arithmetic; placebo and mental arithmetic; and 200 mg of caffeine alone. Systolic and diastolic blood pressure, heart rate, and skin conductance were recorded. During rest, caffeine compared to placebo increased blood pressure by 8/6 mm Hg, but had no effect on heart rate or skin conductance. During mental arithmetic, the combined effect of mental stress and caffeine led to a further increase of 17/7 mm Hg, reaching a pressure level of 163/100 mm Hg. Heart rate and skin conductance were increased above their prior caffeine levels. There were no significant differences between the blood pressure response to mental arithmetic with caffeine and that response to mental arithmetic with a placebo, which may have been due to the fact that the hypertensives were already responding at ceiling level during the mental stressor. 相似文献
62.
Expression of CD14 by Hepatocytes: Upregulation by Cytokines during Endotoxemia 总被引:12,自引:0,他引:12 下载免费PDF全文
63.
Epidemiology of group C rotavirus infection in Western New York women of childbearing age. 总被引:1,自引:1,他引:1 下载免费PDF全文
M Riepenhoff-Talty K Morse C H Wang C Shapiro J Roberts M Welter M Allen M J Evans T D Flanagan 《Journal of clinical microbiology》1997,35(2):486-488
Umbilical cord serum samples (380), an average of 10 per month for 3 years (1990 to 1992), were tested by indirect immunofluorescence assay for group C rotavirus immunoglobulin G. Thirty percent were positive, suggesting that approximately one-third of women of childbearing age in western New York have experienced group C rotavirus infection. 相似文献
64.
The risk of myocardial infarction after quitting smoking in men under 55 years of age 总被引:10,自引:0,他引:10
L Rosenberg D W Kaufman S P Helmrich S Shapiro 《The New England journal of medicine》1985,313(24):1511-1514
We assessed the effect of quitting cigarette smoking on the incidence of nonfatal myocardial infarction in men under the age of 55 in a case-control study of 1873 men with first episodes of myocardial infarction and 2775 controls. For "current" smokers (men who had smoked in the previous year) as compared with those who had never smoked, the estimated relative risk of myocardial infarction, adjusted for age, was 2.9 (95 per cent confidence interval, 2.4 to 3.4). Among exsmokers (those who had last smoked at least one year previously), the relative-risk estimate declined to a value close to unity for those who had abstained for at least two years; the estimate was 2.0 (1.1 to 3.8) for men who had abstained for 12 to 23 months, and the estimates were about 1.0 for men who had abstained for longer intervals. The results were unchanged by allowance for multiple potential confounding factors. A similar pattern was apparent among exsmokers who had smoked heavily for many years; among those predisposed to a myocardial infarction because of family history, hypertension, or other risk factors; and among those with no apparent predisposition. The results suggest that the risk of myocardial infarction in cigarette smokers decreases within a few years of quitting to a level similar to that in men who have never smoked. 相似文献
65.
African trypanosome antigens recognized during the course of infection in N''dama and Zebu cattle. 总被引:3,自引:1,他引:3 下载免费PDF全文
The humoral immune responses to Trypanosoma brucei infection were examined in N'dama and in Zebu, two breeds of cattle recognized for their differing susceptibility to trypanosomiasis. Regardless of the clinical course, animals of both breeds produced antibodies to nonsurface trypanosome antigen(s) detectable by both immunodiffusion and immune fluorescence. As a new approach to assessment of the humoral response to trypanosome infection, protein antigens responded to were isolated by immune precipitation, and their molecular weights were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This allowed the detection of differences in the immune response which correlated with the clinical course of the disease. All cattle of both breeds which exhibited a capacity to control the disease recognized at least one of three specific antigens: protein of 110,000, 150,000, and 300,000 daltons. The N'dama, which proved less susceptible to the disease, generally responded to more of the three identified trypanosome protein antigens than did the Zebu. Animals which died of trypanosomiasis failed to produce detectable antibodies to any of the three specific proteins, although they sometimes exhibited antibodies to another trypanosome antigen. 相似文献
66.
Forty male college student volunteers were asked either to increase their diastolic pressure or their heart rate while sitting and during orthostatic stress (going from a sitting to a standing position), and half of them were also given second- to-second visual feedback for the target variable. Systolic blood pressure was also continuously recorded. Comparisons were made between baseline and voluntary control conditions, and test trials were included to examine immediate carry-over effects. With voluntary control instructions, substantial increases in tonic levels were obtained for the three cardiovascular variables in both sitting and postural change conditions. In general, the increases were significantly greater for feedback than for no-feedback conditions. Phasic effects of feedback were also observed during postural change conditions: the blood pressure troughs and the heart rate peak occurred earlier with feedback than for instructions only. Immediate transfer effects were obtained in feedback conditions only. The results were discussed in terms of concomitant effects of somatic and cognitive activities. The distinctive feedback effects on the time course of the responses suggest that a precise analysis of response patterns is needed in selecting appropriate feedback methods in the management of orthostatic hypotension. 相似文献
67.
Detection of N-myc gene amplification by fluorescence in situ hybridization. Diagnostic utility for neuroblastoma. 总被引:4,自引:1,他引:4 下载免费PDF全文
D. N. Shapiro M. B. Valentine S. T. Rowe A. E. Sinclair J. E. Sublett W. M. Roberts A. T. Look 《The American journal of pathology》1993,142(5):1339-1346
We assessed fluorescence in situ hybridization (FISH) as an alternative to Southern blot analysis for determination of N-myc gene amplification in neuroblastoma. In the 44 pediatric solid tumor cell lines examined (20 neuroblastomas), the mean number of N-myc copies determined by FISH correlated closely with Southern blot results. There was wide intercellular variability in gene copy number in tumors that had evidence of amplification; however, tumors judged to be non-amplified completely lacked any cells with high N-myc copy number. FISH provided reliable estimates of N-myc amplification in 12 clinical samples even when the percentage of tumor was low. The other advantages of FISH over Southern blot analysis were speed and technical simplicity, ability to discern heterogeneous gene amplification among tumor cells in the same specimen, and capacity to determine the source of the amplified N-myc signal, whether extrachromosomal double-minute chromosomes, expanded intrachromosomal regions, or chromosome 2 aneuploidy. We conclude that FISH would refine the analysis of N-myc amplification in neuroblastoma and thus improve the assignment of patients to prognostic groups based on this unfavorable risk factor. 相似文献
68.
Israel Shapiro Zvi Borochowitz Shimon Degani Hanna Dar Izu Ibschitz Mordechai Sharf 《American journal of medical genetics. Part A》1992,43(3):602-605
A diagnosis of the Neu-Laxova syndrome (NLS) was made by ultrasonography at 32 wks of gestation. Ultrasonographic examination showed intrauterine growth retardation (IUGR), Dandy-Walker anomaly, choroid plexus cysts, receding forehead and microcephaly, bilateral cataract without prominent eyes, scalp edema with no generalized edema, retrognathia, curved penis, and flexion deformities of limbs. The findings in this case are consistent with NLS; however, they did not fit any of Curry's [1982] groups. Massive swelling of hands and feet were among the main manifestations in classic NLS cases. In the case presented herein, edema was noted only in the scalp. This might shed further light on the question of variability vs. heterogeneity in the NLS. This case shows the existing possibility of an early diagnosis of NLS and adds Dandy-Walker anomaly and choroid plexus cysts as new findings to this syndrome. © 1992 Wiley-Liss, Inc. 相似文献
69.
Immunohistochemical localization of epinephrine, norepinephrine, catecholamine-synthesizing enzymes, and chromogranin in neuroendocrine cells and tumors. 总被引:2,自引:1,他引:2 下载免费PDF全文
R. V. Lloyd J. C. Sisson B. Shapiro A. A. Verhofstad 《The American journal of pathology》1986,125(1):45-54
The immunohistochemical localization of epinephrine (E), norepinephrine (NE), and chromogranin was analyzed in normal and neoplastic neuroendocrine cells. The immunohistochemical detection of tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT) was used to distinguish between uptake and biosynthesis of catecholamines. E, NE, chromogranin, TH, DBH, and PNMT were found in the normal human adrenal medulla and in pheochromocytomas. Although many neuroendocrine tissues outside of the adrenal gland contained immunoreactive NE, only a small percentage of these tissues contained DBH. E was found in a few neuroendocrine tissues outside of the adrenal, including cardiac paragangliomas, and the enzyme PNMT was localized in some of these neoplasms. There was very close agreement between the localization of chromogranin and of catecholamines in normal and neoplastic neuroendocrine tissues. These results indicate that the presence of catecholamines and chromogranin in neuroendocrine cells and tumors within the adrenal medulla and in many other sites may be closely related. 相似文献
70.
Bareket Falk Ruth Burstein Isaack Ashkenazi Ofer Spilberg Jacob Alter Ester Zylber-Katz Ardon Rubinstein Nava Bashan Yair Shapiro 《European journal of applied physiology》1989,59(3):168-173
Summary The purpose of this study was to determine the effect of caffeine ingestion on physical performance after prolonged endurance
exercise. Twenty three trained male volunteers participated in a 40-km march and were divided into two groups, matched for
caffeine clearance rate and aerobic capacity. The experimental group ingested, prior to the march, a caffeinated drink at
a dose of 5 mg·kg−1 body mass and at the 3rd and 5th h of marching an additional drink at a dose of 2.5 mg·kg−1 body mass. The control group ingested a drink of equal volume at the same times. Upon termination of the march each subject
performed a cycle ergometer test at an intensity of 90% maximal oxygen consumption. Time to exhaustion and rate of perceived
exertion (RPE) were recorded. Blood samples were drawn predrink, at the 3rd and 5th h of marching and immediately after the
cycle ergometer test, and were analysed for caffeine, free fatty acids (FFA), lactate and glucose levels. Plasma FFA levels
increased during the march (p<0.05), with no significant difference between groups. Lactate levels increased in the experimental group (p<0.05), with no significant change in the control group. Glucose levels did not change significantly in either group. After
the cycle ergometer test, lactate levels were significantly higher in the experimental, as compared to the control group (3.77±0.33
vs 2.52±0.35 mmol·l−1, respectively). There was no significant difference between treatments in the time to exhaustion on the cycle ergometer,
but RPE was different (p<0.05). Under the conditions of this study, the results do not indicate caffeine ingestion as an ergogenic aid which will
postpone exhaustion following prolonged endurance exercise.
This work was presented, in part, at the Canadian Association of Sports Sciences Annual Meeting, October 1987, Lake Louise,
Alberta, Canada 相似文献