全文获取类型
收费全文 | 10037篇 |
免费 | 776篇 |
国内免费 | 240篇 |
专业分类
耳鼻咽喉 | 103篇 |
儿科学 | 182篇 |
妇产科学 | 204篇 |
基础医学 | 1496篇 |
口腔科学 | 999篇 |
临床医学 | 611篇 |
内科学 | 1360篇 |
皮肤病学 | 84篇 |
神经病学 | 699篇 |
特种医学 | 697篇 |
外国民族医学 | 1篇 |
外科学 | 1154篇 |
综合类 | 932篇 |
预防医学 | 697篇 |
眼科学 | 75篇 |
药学 | 619篇 |
2篇 | |
中国医学 | 103篇 |
肿瘤学 | 1035篇 |
出版年
2023年 | 176篇 |
2022年 | 386篇 |
2021年 | 503篇 |
2020年 | 362篇 |
2019年 | 412篇 |
2018年 | 379篇 |
2017年 | 400篇 |
2016年 | 396篇 |
2015年 | 460篇 |
2014年 | 748篇 |
2013年 | 728篇 |
2012年 | 685篇 |
2011年 | 670篇 |
2010年 | 477篇 |
2009年 | 424篇 |
2008年 | 424篇 |
2007年 | 382篇 |
2006年 | 330篇 |
2005年 | 261篇 |
2004年 | 204篇 |
2003年 | 158篇 |
2002年 | 130篇 |
2001年 | 123篇 |
2000年 | 106篇 |
1999年 | 126篇 |
1998年 | 101篇 |
1997年 | 97篇 |
1996年 | 56篇 |
1995年 | 49篇 |
1994年 | 77篇 |
1993年 | 77篇 |
1992年 | 70篇 |
1991年 | 68篇 |
1990年 | 49篇 |
1989年 | 59篇 |
1988年 | 50篇 |
1987年 | 65篇 |
1986年 | 34篇 |
1985年 | 77篇 |
1984年 | 81篇 |
1983年 | 48篇 |
1982年 | 88篇 |
1981年 | 55篇 |
1980年 | 41篇 |
1979年 | 56篇 |
1978年 | 51篇 |
1976年 | 44篇 |
1975年 | 54篇 |
1974年 | 48篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Activities of creatine kinase isoenzymes in single skeletal muscle fibres of trained and untrained rats 总被引:1,自引:0,他引:1
Katsumasa Yamashita Toshitada Yoshioka 《Pflügers Archiv : European journal of physiology》1992,421(2-3):270-273
Biochemical changes in the creatine kinase isoenzyme compositions in single muscle fibres of different types in rats were induced by endurance running training. Single muscle fibres were dissected from the soleus and extensor digitorum longus muscles of Wistarstrain male rats trained on a motor-driven treadmill for 16 weeks. Each fibre was typed histochemically (SO, slow-twitch oxidative; FOG, fast-twitch oxidative glycolytic; FG, fast-twitch glycolytic), and the activities of total creatine kinase and its four isoenzymes (CK-MM, -MB,-BB, and mitochondrial creatine kinase) were measured. The endurance training did not affect the total creatine kinase activity, but resulted in significantly increased activities of CK-MB and CK-BB in SO and FOG fibres, and the mitochondrial enzyme activity in FOG and FG fibres. Endurance training induced biochemical changes in the isoenzyme compositions, specifically in FOG fibres. These results suggest that changes in creatine kinase isoenzymes with endurance training reflect changes in the energy metabolism in the different muscle fibres, supporting the hypothesis that the different isoenzymes play different roles in energy transduction. 相似文献
22.
Unilateral lesion of the nigrostriatal pathway decreases the firing rate and alters the firing pattern of globus pallidus neurons in the rat 总被引:2,自引:0,他引:2
Activities of spontaneously firing neurons in the globus pallidus of intact rats and rats that survived unilateral lesions of the nigrostriatal pathway for 3 days, 1 week, or 6-11 weeks were compared. No significant differences in neuronal firing rate, firing pattern, and number of cells per pass were observed between chloral hydrate-anesthetized control and lesioned animals. However, in locally anesthetized animals, pallidal cells fired significantly faster than in chloral hydrate-anesthetized animals, and the lesion caused a decrease in the firing rates of pallidal cells 1 week and 6-9 weeks postlesion. In addition, significant differences in the firing pattern of pallidal cells, as determined by the ratio of the mean to median interspike intervals, were seen between locally anesthetized controls and animals surviving 3 days, 1 week, and 6-9 weeks postlesion. This altered firing pattern tended to return to normal with time. The number of cells per pass was not significantly altered by the lesion. Data from this study suggest that, in locally anesthetized animals, the removal of the tonic dopaminergic input to the basal ganglia causes pallidal cells to decrease their firing rates in a time-dependent fashion and causes reversable firing pattern changes. This suggests that tonically active dopamine neurons, probably acting through the striatopallidal pathway, regulate the firing rate and mechanisms controlling the temporal ordering of spontaneous discharges of globus pallidus neurons. 相似文献
23.
Masaki Shinoda Tsuyoshi Yamaguchi Yoshimi Tanaka Osamu Sato Sin Kobayashi Yutaka Suzuki 《Child's nervous system》1992,8(4):219-221
Single photon emission computerized tomography (SPECT) is now widely used as one of the tools in evaluating cerebral blood flow (CBF). The authors report the CBF changes in childhood hydrocephalus. Five pediatric cases studied by 123I-IM SPECT in children are presented. The authors counted radioactivities both in early and delayed images in each patient, and calculated the reabsorption ratio (RR). Two negative-RR cases and three positive-RR cases were found. All of the negative-RR patients had a poor prognosis, while all of the positive-RR patients had a favorable outcome. 相似文献
24.
用单板计算机配合肾图仪,可自动采集肾图数据、计算并打印指标及曲线.75例病人的配对比较结果表明:计算机结果与原肾图仪无显著性差异.由此证明我们编制的应用程是合理可行的. 相似文献
25.
H. Oka T. Yamamoto T. Kawazoe K. Saratani Y. Hikida 《Medical & biological engineering & computing》1988,26(3):260-266
A new impact response method using a fracture of a pencil-lead to produce an excitation pulse is proposed. Impact excitations
(rectangular pulse, triangular pulse and half-sine pulse) are strictly given in physical and mathematical definitions and
complete solutions to the impact excitations are provided for Noyes' model of the human tooth. When a relatively long triangular
pulse is applied to Noyes' model, which can express the physical characteristic of periodontal tissues, a sinusoidal damped
vibration of a single degree-of-freedom model is approximately obtained. The acceleration response is characterised by the
physical parameters (T, δ and Ao) and mechanical elements (m1, c1 and k) of which a single degree-of-freedom model is composed. By means of this method, the values of the parameters and elements
in the cases of healthy maxillary, healthy mandibular and pathological mandibular incisors are obtained. The single degree-of-freedom
model can express the high-frequency spectra of Noyes' model. The pathological tooth is characterised by a longer damped time
constant and a larger acceleration maximum. This impact response method can effectively be applied to clinical diagnosis in
view of the physical parameters and mechanical elements which have been derived. 相似文献
26.
MRI and SPECT findings in amyotrophic lateral sclerosis 总被引:1,自引:0,他引:1
Summary MRI was performed in 21 patients and single photon emission computed tomography (SPECT) withN-isopropyl-p-123I iodoamphetamine in 16 patients, to visualize upper motor neurone lesions in amyotrophic lateral sclerosis. T2-weighted MRI revealed high signal along the course of the pyramidal tract in the internal capsule and cerebral peduncle in 4 of 21 patients. SPECT images were normal in 4 patients, but uptake was reduced in the cerebral cortex that includes the motor area in 11. 相似文献
27.
Brett W. Cox M.D. Kathleen C. Horst M.D. Sherri Thornton C.M.D. Frederick M. Dirbas M.D. 《Medical Dosimetry》2007,32(4):254-262
The purpose of this study was to evaluate the dose to normal tissues as a function of increasing margins around the lumpectomy cavity in accelerated partial breast irradiation (APBI) using 3D-conformal radiotherapy (3DCRT). Eight patients with Stage 0-I breast cancer underwent treatment planning for 3DCRT APBI. The clinical target volume (CTV) was defined as a 15-mm expansion around the cavity limited by the chest wall and skin. Three planning target volumes (PTV1, PTV2, PTV3) were generated for each patient using a 0, 5-, and 10-mm expansion around the CTV, for a total margin of 15, 20, and 25 mm. Three treatment plans were generated for every patient using the 3 PTVs, and dose-volume analysis was performed for each plan. For each 5-mm increase in margin, the mean PTV:total breast volume ratio increased 10% and the relative increase in the mean ipsilateral breast dose was 15%. The mean volume of ipsilateral breast tissue receiving 75%, 50%, and 25% of the prescribed dose increased 6% to 7% for every 5 mm increase in PTV margin. Compared to lesions located in the upper outer quadrant, plans for medially located tumors revealed higher mean ipsilateral breast doses and 20% to 22% more ipsilateral breast tissue encompassed by the 25% IDL. The use of 3DCRT for APBI delivers higher doses to normal breast tissue as the PTV increases around the lumpectomy cavity. Efforts should be made to minimize the overall PTV when this technique is used. Ongoing studies will be necessary to determine the clinical relevance of these findings. 相似文献
28.
James A. Case Bai Ling Hsu Timothy M. Bateman S. James Cullom 《Journal of nuclear cardiology》2007,14(3):324-333
Background High-quality attenuation maps are critical for attenuation correction of myocardial perfusion single photon emission computed
tomography studies. The filtered backprojection (FBP) approach can introduce errors, especially with low-count transmission
data. We present a new method for attenuation map reconstruction and examine its performance in phantom and patient data.
Methods and Results The Bayesian iterative transmission gradient algorithm incorporates a spatially varying gamma prior function that preferentially
weights estimated attenuation coefficients toward the soft-tissue value while allowing data-driven solutions for lung and
bone regions. The performance with attenuation-corrected technetium 99m sestamibi clinical images was evaluated in phantom
studies and in 50 low-likelihood patients grouped by body mass index (BMI). The algorithm converged in 15 iterations in the
phantom studies. For the clinical studies, soft-tissue estimates had significantly greater uniformity of mediastinal coefficients
(mean SD, 0.005 cm−1 vs 0.011 cm−1; P<.0001). The accuracy and uniformity of the Bayesian iterative transmission gradient algorithm were independent of BMI, whereas
both declined at higher BMI values with FBP. Attenuation-corrected perfusion images showed improvement in myocardial wall
variability (4.8% to 4.1%, P=.02) for all BMI groups with the new method compared with FBP.
Conclusion This new method for attenuation map reconstruction provides rapidly converging and accurate attenuation maps over a wide spectrum
of patient BMI values and significantly improves attenuation-corrected perfusion images. 相似文献
29.
30.