全文获取类型
收费全文 | 3763篇 |
免费 | 146篇 |
国内免费 | 64篇 |
专业分类
耳鼻咽喉 | 85篇 |
儿科学 | 90篇 |
妇产科学 | 97篇 |
基础医学 | 522篇 |
口腔科学 | 145篇 |
临床医学 | 407篇 |
内科学 | 451篇 |
皮肤病学 | 36篇 |
神经病学 | 381篇 |
特种医学 | 217篇 |
外科学 | 221篇 |
综合类 | 368篇 |
一般理论 | 1篇 |
预防医学 | 257篇 |
眼科学 | 88篇 |
药学 | 348篇 |
中国医学 | 46篇 |
肿瘤学 | 213篇 |
出版年
2023年 | 29篇 |
2022年 | 61篇 |
2021年 | 99篇 |
2020年 | 83篇 |
2019年 | 78篇 |
2018年 | 90篇 |
2017年 | 58篇 |
2016年 | 65篇 |
2015年 | 81篇 |
2014年 | 180篇 |
2013年 | 249篇 |
2012年 | 183篇 |
2011年 | 215篇 |
2010年 | 159篇 |
2009年 | 196篇 |
2008年 | 174篇 |
2007年 | 189篇 |
2006年 | 169篇 |
2005年 | 132篇 |
2004年 | 118篇 |
2003年 | 106篇 |
2002年 | 79篇 |
2001年 | 64篇 |
2000年 | 76篇 |
1999年 | 85篇 |
1998年 | 62篇 |
1997年 | 77篇 |
1996年 | 60篇 |
1995年 | 57篇 |
1994年 | 47篇 |
1993年 | 54篇 |
1992年 | 47篇 |
1991年 | 53篇 |
1990年 | 44篇 |
1989年 | 38篇 |
1988年 | 33篇 |
1987年 | 35篇 |
1986年 | 47篇 |
1985年 | 37篇 |
1984年 | 56篇 |
1983年 | 22篇 |
1982年 | 45篇 |
1981年 | 24篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 10篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有3973条查询结果,搜索用时 15 毫秒
21.
E. B. Andersen F. Boesen O. Henriksen 《Clinical physiology and functional imaging》1991,11(5):451-458
Summary. The effect of age and sex on relative changes in blood flow and vascular resistance in skeletal muscle and subcutaneous tissue during postural changes and during local increase in transmural pressure was studied in 33 healthy subjects. The intra-individual variation was studied in five subjects. Blood flow was measured by the local 133Xenon wash-out method. No relation to age or sex was seen in the centrally elicited sympathetic vasoconstrictor responses in subcutaneous tissue and skeletal muscle and in the locally elicited vasoconstriction in subcutaneous tissue. A small, but statistically significant, correlation to sex and age was found in the local sympathetic vasoconstrictor response in skeletal muscle. The age correlation was caused only by an attenuated response in the young subjects below 40 years of age and may be fortuitous. The intra-individual variation was acceptably small. Based on the present results, a reduction in blood flow in skeletal muscle and subcutaneous tissue during centrally or locally elicited sympathetic vasoconstriction of 10% or less should be considered abnormal. The local 133Xenon wash-out method is of value in examining patients suspected of dysfunction in the sympathetic part of the autonomic nervous system. 相似文献
22.
23.
Sex differences in plasma cocaine levels and subjective effects after acute cocaine administration in human volunteers 总被引:3,自引:3,他引:0
S. E. Lukas M. Sholar L. H. Lundahl X. Lamas E. Kouri J. D. Wines L. Kragie J. H. Mendelson 《Psychopharmacology》1996,125(4):346-354
Gender differences after acute cocaine administration have received little attention in spite of the fact that males and females respond differently to many drugs. Seven male and seven female occasional cocaine users received both an intranasal dose of cocaine hydrochloride (0.9 mg/kg) and placebo powder in a randomized order and reported subjective effects via an instrumental joystick device and various questionnaires. Blood samples were withdrawn at 5-min intervals to assess pharmacokinetic differences. Male subjects achieved the highest peak plasma cocaine levels (144.4 ± 17.5 ng/ml), detected cocaine effects significantly faster than females and also experienced a greater number of episodes of intense good and bad effects. Women studied during the follicular phase of their menstrual cycle had peak plasma cocaine levels of 73.2 ± 9.9 ng/ml, which was significantly higher than when they were studied during their luteal phase (54.7 ± 8.7 ng/ml), but there were no differences in their subjective reports of cocaine effects. In spite of the different cocaine blood levels and subjective effects, peak heart rate increases did not differ between males and females suggesting that women may be more sensitive than males to the cardiovascular effects of cocaine. These data suggest that there are significant gender and menstrual cycle differences in the response to acute intranasal cocaine administration and these differences may have implications for the differential abuse of this drug.This paper is dedicated to Xavier Lamas, MD, PhD, who lost his life while ascending Mt. Everest, August 1995 相似文献
24.
年龄因素对健康人心率变异性的影响 总被引:1,自引:0,他引:1
目的探讨年龄因素对健康人心率变异性(HRV)的影响。材料与方法将236例健康人分为五个年龄组,使用美国先进医用设备公司5.0版本HRV软件做短时时域及频域HRV分析。结果年龄因素对健康人HRV短时时域和频域分析的多项指标产生显著影响,随着年龄增大,时域指标中的HRSD、SDANN、rMSSD及PNN50均逐渐降低;随着年龄增长,频域指标中各频段下的绝对面积,即:VLF、LF、MF及HF均逐渐降低;而频域指标中各频段下的相对面积,即:VLFP、LFP、MFP、HFP随着年龄增长呈不同的发展趋势。LF/HF随着年龄的增加而逐渐升高。结论HRV随着年龄的增加而下降,尤以迷走神经活性下降为显著。频域指标中各频段的相对面积较绝对面积能更敏感地反映交感、迷走神经张力的消长。 相似文献
25.
Radiotelemetry of the human EKG was obtained to observe for rate alterations during spontaneous cigarette smoking. Ten subjects were observed for a total of 26 hours during which time 50 cigarettes were smoked. The utilization of telemetry allowed the subjects to continue their usual afternoon behavior. There were no rate changes before, during, or after smoking which could be attributed to the cigarette. These results differ from most previous reports. Telemetry allows for two departures from past designs; subjects were ambulant and smoking behavior was spontaneous (both in initiation and rate). It is suggested that these departures are related to the results of the present study. 相似文献
26.
Schweigart G Chien RD Mergner T 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2002,147(1):89-97
Vestibular functions are known to show some deterioration with age. Vestibular deterioration is often thought to be compensated
for by an increase in neck proprioceptive gain. We studied this presumed compensatory mechanism by measuring psychophysical
responses to vestibular (horizontal canal), neck and combined stimuli in 50 healthy human subjects as a function of age (range
15–76 years). After passive horizontal rotations of head and/or trunk (torso) in complete darkness (dominant frequencies 0.05,
0.1, and 0.4 Hz), subjects readjusted a visual target to its remembered prerotational location in space. (1) Vestibular-only stimulus (whole-body rotation); subjects' responses were shifted towards postrotatory body position, this only slightly at 0.4 Hz and
pronounced at 0.1 and 0.05 Hz. These errors reflect the known physiological drop of vestibular gain at low rotational frequency.
They exhibited a slight but significant increase with age. (2) Neck-only stimulus (trunk rotated, head stationary); the responses showed errors similar to those upon vestibular stimulation (with offset towards
postrotatory trunk position) and this again slightly more with increasing age. (3) Vestibular-neck stimulus combination during head rotation on stationary trunk; the errors were close to zero, independent of stimulus frequency and the subjects'
age. (4) Opposite stimulus combination (trunk rotated in the same direction as the head, but with double amplitude); the errors were clearly enhanced, essentially
reflecting the sum of those with vestibular-only and neck-only stimulation. Taken together, we find a parallel increase in
neck- and vestibular-related errors with age, in seeming contrast to previous studies. We explain our and the previous findings
by a vestibular-neck interaction model in which two different neck signals are involved. One neck signal is used, in combination
with the vestibular signal, for estimating trunk-in-space rotation. It is internally shaped to always match the vestibular
signal, so that these two signals cancel each other out when summed during head rotation on stationary trunk. Because of this
matching, perceived trunk stationariness during head rotation on the stationary trunk is independent of vestibular deterioration
(related to stimulus frequency, age, ototoxic medication, etc.). The other neck proprioceptive signal, coding head-on-trunk
rotation, is superimposed on the estimate of trunk-in-space rotation, thereby yielding a notion of head-in-space. This neck
signal remains essentially unchanged with vestibular deterioration. Generally, we hold that the transformation of the vestibular
signal from the head down to the trunk proceeds further to include the hip and the legs as well as the haptically perceived
body support surface; by this, subjects yield a notion of support kinematics in space. As a consequence, spatial orientation
is impaired by chronic vestibular deterioration only to the extent that the body support is moving in space, while it is unimpaired
(determined by proprioception alone) during body motion with respect to a stationary support.
Electronic Publication 相似文献
27.
Kirsi T. Ailus 《American journal of reproductive immunology (New York, N.Y. : 1989)》1994,31(4):189-196
PROBLEM: To obtain a systematic view of changes in the levels of immunoglobulins (Igs), other serum proteins, and autoantibodies during pregnancy and postpartum. METHOD: A series of 220 women were followed throughout pregnancy and four to six months postpartum. RESULTS: Immunoglobulin G (IgG) concentration clearly decreased toward term. The concentrations of IgM and IgA decreased only slightly. In most instances autoantibody levels paralleled changes in the corresponding immunoglobulin class levels. In few cases, however, there were clear deviations from this. With respect to IgG class autoantibodies, the highest autoantibody levels were found in the postpartum specimen. IgM class autoantbody levels remained almost constant throughout the follow-up period. CONCLUSIONS: The intrapregnancy decrease of IgG is mainly due to hemodilution, but when the effect of hemodilution is taken into account, total amounts of IgM and IgA are increased. The results suggests that compared to IgG the regulatory mechanisms of IgM and IgA are altered during pregnancy. 相似文献
28.
Stress or heat-shock proteins may be involved in the initiation and perpetuation of autoimmune diseases. In order to investigate a possible role of autoantibodies against the 70-kD family of heat-shock proteins in systemic lupus erythematosus (SLE), sera of SLE patients and healthy subjects were tested for the presence of IgG and IgM antibodies to 70-kD class proteins. These proteins were purified by affinity chromatography on ATP-agarose and used in Western blotting studies. The data obtained revealed that antibodies to the 72-kD and the 73-kD heat-shock proteins occurred with similar frequencies both in healthy subjects and SLE patients. Thus, approximately 20% of the sera in each group contained IgG antibodies, and IgM antibodies were detected in about 30% of the sera tested. Moreover, in SLE patients no association between the occurrence and litre of these antibodies and disease activity was found. These data suggest that antibodies to the 70-kD class heat-shock proteins are naturally occurring and argue therefore against an involvement of these antibodies in the pathogenesis of SLE. 相似文献
29.
研究了18例新鲜尸体T12-L5腰段脊柱应力松弛,蠕变特性。测定了完整脊柱(正常组)及模拟前路(对照1组),后路手术(对照2组)腰段脊柱的应力松弛和蠕变效应,得出了在恒应变,应力条件下应力-时间曲线及数据,用回归分析的方法处理实验数据,得出了归一化应务松弛,蠕变函数及曲线,对前路间盘摘除术与后路间盘摘除术对脊柱粘弹性的影响进行分析讨论。 相似文献
30.
H. Pekkarinen H. Tukiainen H. Litmanen J. Huttunen T. Karstu E. Länsimies 《European journal of applied physiology》1989,58(8):821-825
Summary In order to understand more fully the effect on pulmonary function of whole body exposure to cold during submaximal exercise,
we measured pulmonary function indices in ten healthy male students and ten healthy male forestry workers of similar age following
submaximal treadmill walking at different temperatures in a climatic chamber. After measuring the maximal aerobic capacity
with a cycle ergometer test, the subjects had to walk on four separate occasions in the climatic chamber at an intensity of
70%–75% of their individual maximal heart rate; the first at normal room temperature and then randomly, either at 0°C or at
−20°C, and vice versa. The duration of each walk was 8 min. Finally, each subject had to walk in the chamber at −20° C for
17 min. Flow volume spirometry was performed at room temperature 1, 5, 10, and 20 min after exercise and the values were compared
to baseline values taken prior to the last walking test. There were only minor changes in pulmonary function indices following
exercise at different temperatures. Only one student showed a reduction of over 15% in peak expiratory flow rate after an
8-min walk at −20° C. It seems that submaximal exercise of short duration, even at a temperature as low as −20° C, does not
impair pulmonary function in healthy young men. 相似文献