全文获取类型
收费全文 | 11239篇 |
免费 | 1202篇 |
国内免费 | 171篇 |
专业分类
耳鼻咽喉 | 40篇 |
儿科学 | 146篇 |
妇产科学 | 71篇 |
基础医学 | 1110篇 |
口腔科学 | 108篇 |
临床医学 | 2336篇 |
内科学 | 947篇 |
皮肤病学 | 93篇 |
神经病学 | 1189篇 |
特种医学 | 172篇 |
外国民族医学 | 1篇 |
外科学 | 403篇 |
综合类 | 1738篇 |
一般理论 | 5篇 |
预防医学 | 1490篇 |
眼科学 | 67篇 |
药学 | 773篇 |
34篇 | |
中国医学 | 1731篇 |
肿瘤学 | 158篇 |
出版年
2024年 | 50篇 |
2023年 | 240篇 |
2022年 | 405篇 |
2021年 | 667篇 |
2020年 | 535篇 |
2019年 | 484篇 |
2018年 | 382篇 |
2017年 | 532篇 |
2016年 | 470篇 |
2015年 | 456篇 |
2014年 | 816篇 |
2013年 | 1014篇 |
2012年 | 720篇 |
2011年 | 782篇 |
2010年 | 586篇 |
2009年 | 545篇 |
2008年 | 545篇 |
2007年 | 485篇 |
2006年 | 413篇 |
2005年 | 338篇 |
2004年 | 296篇 |
2003年 | 251篇 |
2002年 | 185篇 |
2001年 | 172篇 |
2000年 | 172篇 |
1999年 | 123篇 |
1998年 | 110篇 |
1997年 | 104篇 |
1996年 | 83篇 |
1995年 | 69篇 |
1994年 | 44篇 |
1993年 | 52篇 |
1992年 | 62篇 |
1991年 | 36篇 |
1990年 | 38篇 |
1989年 | 28篇 |
1988年 | 37篇 |
1987年 | 27篇 |
1986年 | 33篇 |
1985年 | 27篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 18篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
C. T. M. Davies J. R. Brotherhood E. ZeidiFard 《European journal of applied physiology》1978,38(3):225-232
Summary The effects of intravenous injections of Atropine (1.8 mg) and practolol (15 mg) on the thermoregulatory responses to 1 h of exercise on a motordriven treadmill have been investigated on six healthy subjects.The results show that -blockade had little effect on thermal responses to work except for a small but significant (p<0.05) decrease in mean skin temperature (¯T
sk
) and peripheral tissue heat conductance (K). Metabolic (M) and total heat (H) production, and evaporative sweat loss (E) and rectal temperature (T
re
) were similar to control values. In contrast, atropine, particularly at work loads beyond 60% maximal aerobic power output (VO2 max), raised T
re
(p<0.001), ¯T
sk
(p<0.001) and reduced E by approximately 50%. At the highest work loads T
re
increased as a linear function of time during the latter part of exercise, and at the 60th min was almost independent of relative stress (expressed as % VO2 max) imposed on the subjects. At the lower work loads the majority of subjects reached thermal equilibrium before the end of exercise by maintaining their convective heat transfer from core to periphery by increasing peripheral blood flow (as indicated by K), and raising their heat losses to environment by convection and radiation. The latter pathways for heat dissipation were enhanced by the subjects ability to sustain a ¯T
sk
4 C above control values independently of M. Atropine had no effect on M or H but greatly affected work performance, no subject was able to exercise at loads >70% VO2 max for 1 h. These results demonstrate the ability of the thermoregulatory system to adapt to -adrenergic and to parasympathetic blockade during light exercise, and underline the effects of a reduction in the capacity of the sweating mechanism on physiological performance at higher rates of work.List of Abbreviations used in the Text
M
Metabolic heat production
-
H
Total heat production
-
E
Evaporative sweat loss
-
T
re
Rectal temperature
-
¯T
sk
Mean skin temperature
-
K
Peripheral tissue heat conductance
-
PBF
Peripheral blood flow
-
VO2 max
Maximal aerobic power output
-
f
H
Cardiac frequency 相似文献
82.
A systematic comparison of the effect of architectural modifications to the network structure on the internal microstructure of N‐isopropylacrylamide (NIPA) based hydrogels showed that the addition of a second component to the network significantly increased the proportion of macropores in the network. The second components considered were short poly(N‐isopropylacrylamide) (PNIPAM) chains grafted to the network backbone, high‐molecular‐weight polyacrylamide (PAM) chains, or microsphere particles of PNIPAM. Structures are proposed for each of the modified gel networks taking into account the new structural information. Through a combination of the pore size and network structure data reported here, and with the shrinking data obtained previously, shrinking mechanisms are proposed for each of the modified network structures. In all cases, the enhanced shrinking rates were directly caused by the presence of the second component, which acted as nuclei for shrinking (graft‐PNIPAM and PNIPAM microspheres) or as water‐release channels (PAM gel), and indirectly caused by the second components via their affect on the network microstructure.
83.
To protect plasma supplies, donors are screened for infectiousdiseases. As an added measure of protection, donations are identifiedand stored for a period of time to allow future discard in theevent that an identified donor subsequently tests positive forsome screened disease. Previous models for evaluating such plasmaholds have only addressed the case of a single infectious disease.This paper extends the analysis to the case of multiple infections.Given knowledge of the marginal incidence rates for those infectionschecked, upper and lower bounds for important quantities suchas the probability of interdicting an infectious but undetecteddonation, the expected number of infections interdicted perdonation, and the net economic benefits of the holding policyare developed. Several examples are developed, illustratinghow the models can be used to evaluate the consequences of aplasma hold. 相似文献
84.
Rawe VY Olmedo SB Nodar FN Ponzio R Sutovsky P 《Human reproduction (Oxford, England)》2003,18(3):576-582
BACKGROUND: The assembly of nuclear pore complexes (NPC) and their cytoplasmic stacks, annulate lamellae (AL), promote normal nucleocytoplasmic trafficking and accompany pronuclear development within the mammalian zygote. Previous studies showed that a percentage of human oocytes fertilized in vitro failed to develop normal pronuclei and cleave within 40-48 h post insemination. We hypothesized that an aberrant recruitment of NPC proteins, nucleoporins and/or NPC preassembled into AL, might accompany human fertilization arrest. METHODS AND RESULTS: We explored NPC and AL assembly in unfertilized human oocytes, and fertilized and arrested zygotes by immunofluorescence with an NPC- and AL-specific antibody, mAb 414, and by transmission electron microscopy. Major NPC or AL assembly was not observed in the unfertilized human oocytes. Once fertilization took place, the formation of AL was observed throughout the cytoplasm and near the developing pronuclei with NPC. On the contrary, NPC assembly was disrupted in the arrested zygotes, whereas AL were clustered into large sheaths. This was accompanied by the lack of NPC incorporation into the nuclear envelopes. CONCLUSIONS: We conclude that the aberrant assembly of NPC and AL coincides with early developmental failure in humans. 相似文献
85.
磷脂双层膜稳定性的理论分析 总被引:2,自引:0,他引:2
目的:越来越多磷脂双层膜的原子力显微镜扫描力谱显示溶液离子浓度对磷脂双层膜稳定性有很大影响,本文从理论角度研究溶液离子浓度对磷脂双层膜稳定性的影响,同时解释两个基于不同模型模拟结果差别的原因。方法:主要根据磷脂分子极性端带电特性,将极性端看作偶极子,然后基于偶极-偶极相互作用理论以及泊松-玻尔兹曼理论解决以上问题。结论:随着离子浓度的增加,磷脂双层膜趋于更加稳定;基于两个不同模型模拟结果差别的原因是高浓度溶液的强静电屏蔽作用。 相似文献
86.
The relationship between cardiac activity and sensory acuity suggested by Lacey and Lacey was tested by recording heart rates of Ss attempting to detect a threshold-level visual stimulus. Heart rate decelerations during a warning tone preceding the threshold stimulus were found in be greater on hit trials than on miss trials, supporting the suggested relationship. 相似文献
87.
88.
多参数信息融合实现非脑电的睡眠结构分期 总被引:7,自引:3,他引:7
目前临床睡眠分析的主要手段是多导睡眠图(Polysomnograph,PSG),用仪器记录被测者整晚的脑电、眼动电和颏肌电等生理参数,计算机进行自动睡眠分期,再由技术人员依据国际标准进行校正.几十年来PSG保持着睡眠分期金标准的地位.提出在不使用脑电的条件下,利用较易获得的心动周期、呼吸、体动等基本生理参数,提取其中与睡眠过程及其变化有关的规律和信息,建立知识规则库,采用不确定推理的证据理论进行多参数睡眠信息融合计算,实现睡眠结构分期.50余例与PSG对照试验结果表明:醒睡的平均符合率达90%以上,基本睡眠结构的平均符合率达75%以上,证明该技术达到了应用的要求. 相似文献
89.
Tetsuya Yoshida Seiichi Nakai Akira Yorimoto Takashi Kawabata Taketoshi Morimoto 《European journal of applied physiology》1995,71(2-3):235-239
We measured the aerobic capacity, sweat rate and fluid intake of trained athletes during outdoor exercise and examined the relationship between aerobic capacity and thermoregulatory responses at high ambient temperatures. The maximal aerobic capacity (
) of the subjects, nine male baseball players of college age, was determined by maximal exercise tests on a cycle ergometer. The subjects practised baseball regularly without drinking fluids from 1330 to 1530 hours. After 30 min rest, they played a baseball game with free access to a sports drink at 15°C from 1600 to 1830 hours. At a mean ambient temperature of 36.7 (SEM 0.2)°C, the mean percentage of body mass loss (m
b) and increase of oral temperature (T
o) from 1330 to 1530 hours was 3.47 (SEM 0.12)% and 0.81 (SEM 0.14)°C, respectively. The sweat loss from 1330 to 1830 hours was 56.53 (SEM 1.56)ml · kg–1 of body mass (M
b) while the mean fluid consumption was 44.78 (SEM 2.39)ml · kg–1 ofm
b, with recovery of 76.08 (SEM 2.81)% of sweat loss. The
was significantly inversely correlated withm
b, fluid intake and rehydration amount, but showed no correlation withT
o. These results would suggest that at a given exercise intensity in subjects with a higher aerobic capacity body temperature is maintained with a lower sweating rate than that in subjects with a lower aerobic capacity. 相似文献
90.
The main purpose of the study was to compare the efficiency of the Fishbein and Ajzen and the Triandis models to predict (1) the intention to participate regularly in some physical activities during free time within a 3-week period and (2) the exercise behavior within these 3 weeks among a group of 166 subjects, aged 22 to 65 years. Our results show that the Triandis model was as efficient as the Fishbein and Ajzen model in predicting the exercise behavior. However, the results obtained from the Triandis model demonstrate the importance of the habit of exercising in predicting the exercise behavior. Moreover, the Triandis model was superior to the Fishbein and Ajzen model in explaining behavioral intention. Of particular interest was the salience of the affective, social, and personal belief components of the Triandis model. In addition, from a practical perspective, this comparative study showed that (1) to exercise regularly is perceived as hard work, and (2) individuals believe that it is their own responsibility to exercise or not to exercise. 相似文献