全文获取类型
收费全文 | 133438篇 |
免费 | 11276篇 |
国内免费 | 4249篇 |
专业分类
耳鼻咽喉 | 647篇 |
儿科学 | 1650篇 |
妇产科学 | 921篇 |
基础医学 | 11080篇 |
口腔科学 | 1712篇 |
临床医学 | 12074篇 |
内科学 | 14566篇 |
皮肤病学 | 1550篇 |
神经病学 | 11503篇 |
特种医学 | 2988篇 |
外国民族医学 | 9篇 |
外科学 | 8850篇 |
综合类 | 19124篇 |
现状与发展 | 12篇 |
一般理论 | 4篇 |
预防医学 | 13779篇 |
眼科学 | 1434篇 |
药学 | 35284篇 |
129篇 | |
中国医学 | 5367篇 |
肿瘤学 | 6280篇 |
出版年
2024年 | 355篇 |
2023年 | 2043篇 |
2022年 | 3590篇 |
2021年 | 4987篇 |
2020年 | 4968篇 |
2019年 | 4292篇 |
2018年 | 4348篇 |
2017年 | 4608篇 |
2016年 | 4628篇 |
2015年 | 4612篇 |
2014年 | 8558篇 |
2013年 | 11660篇 |
2012年 | 8399篇 |
2011年 | 9933篇 |
2010年 | 7173篇 |
2009年 | 6728篇 |
2008年 | 6537篇 |
2007年 | 6289篇 |
2006年 | 5676篇 |
2005年 | 4940篇 |
2004年 | 4178篇 |
2003年 | 3752篇 |
2002年 | 2914篇 |
2001年 | 2653篇 |
2000年 | 2163篇 |
1999年 | 1845篇 |
1998年 | 1723篇 |
1997年 | 1625篇 |
1996年 | 1366篇 |
1995年 | 1289篇 |
1994年 | 1179篇 |
1993年 | 1007篇 |
1992年 | 1021篇 |
1991年 | 938篇 |
1990年 | 771篇 |
1989年 | 651篇 |
1988年 | 669篇 |
1987年 | 640篇 |
1986年 | 553篇 |
1985年 | 695篇 |
1984年 | 574篇 |
1983年 | 378篇 |
1982年 | 386篇 |
1981年 | 338篇 |
1980年 | 301篇 |
1979年 | 208篇 |
1978年 | 206篇 |
1977年 | 165篇 |
1976年 | 144篇 |
1975年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Dr. Y. Fukuoka M. Noshiro H. Shindo H. Minamitani M. Ishikawa 《Medical & biological engineering & computing》1997,35(1):33-39
The nonlinearity included in the PCO
2 control system in humans is evaluated using the degree of nonlinearity based on a difference of residuals. An autoregressive
moving average (ARMA) model and neural networks (linear and nonlinear) are employed to model the system, and three types of
network (Jordan, Elman and fully interconnected) are compared. As the Jordan-type linear network cannot approximate respiratory
data accurately, the other two types and the ARMA model are used for the evaluation of the nonlinearity. The results of the
evaluation indicate that the linear assumption for the PCO
2 control system is invalid for three subjects out of seven. In particular, strong nonlinearity was observed for two subjects. 相似文献
992.
为了解眼睛房水压强变化规律,进一步建立闭角型青光眼模型和对疾病的治疗及视功能康复提供参考,探讨一种在体连续测量正常兔眼前房压强的方法。将正常成年新西兰白兔麻醉后,先用静脉留置针(20G)自角膜缘外行前房穿刺术,然后通过套管将Millar导管植入兔眼的前房,兔眼的前房压强信号经过Powerlab系统进行滤波、放大和模数转换后,通过Chart软件进行实时显示。结果表明:用该方法测得的正常兔眼24 h前房压强的变化范围为(1.31±0.21—2.74±0.83)KPa。前房压强的分布凌晨较低(0~5点),然后逐渐升高(5~10点),到中午或下午(11—17点)时达到最高峰,晚上又逐渐下降(18~23点)。结果证明本实验在体连续测量兔眼前房压强的方法是可行的。 相似文献
993.
M. B. Dutia Alexander R. Johnston 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,118(2):148-154
The postnatal maturation of medial vestibular nucleus (MVN) neurones was examined in slices of the dorsal brainstem prepared
from balb/c mice at specific stages during the first postnatal month. Using spike-shape averaging to analyse the intracellularly recorded
action potentials and after-hyperpolarisations (AHPs) in each cell, all the MVN neurones recorded in the young adult (postnatal
day 30; P30) mouse were shown to have either a single deep AHP (type A cells), or an early fast and a delayed slow AHP (type
B cells). The relative proportions of the two subtypes were similar to those in the young adult rat. At P5, all the MVN cells
recorded showed immature forms of either the type A or the type B action potential shape. Immature type A cells had broad
spontaneous spikes, and the characteristic single AHP was small in amplitude. Immature type B cells had somewhat narrower
spontaneous spikes that were followed by a delayed, apamin-sensitive AHP. The delayed AHP was separated from the repolarisation
phase of the spike by a period of isopotentiality. Over the period P10–P15, the mean resting potentials of the MVN cells became
more negative, their action potential fall-times became shorter, the single AHP in type A cells became deeper, and the early
fast AHP appeared in type B cells. Until P15 cells of varying degrees of electrophysiological maturity were found in the MVN
but by P30 all MVN cells recorded were typical adult type A or type B cells. Exposure to the selective blocker of SK-type
Ca-activated K channels, apamin (0.3 μM), induced depolarising plateaux and burst firing in immature type B cells at rest.
The duration of the apamin-induced bursts and the spike frequency during the bursts were reduced but not abolished after blockade
of Ca channels in Ca-free artificial cerebrospinal fluid containing Cd2+. By contrast, in mature type B cells at rest apamin selectively abolished the delayed slow AHP but did not induce bursting
activity. Apamin had no effect on the action potential shape of immature type A cells. These data show that the apamin-sensitive
I
AHP is one of the first ionic conductances to appear in type B cells, and that it plays an important role in regulating the intrinsic
rhythmicity and excitability of these cells.
Received: 19 November 1996 / Accepted: 30 June 1997 相似文献
994.
M. Deckert-Schlüter Josef Marek Michael Šetlík Jana Marková E. Pakos Robert Fischer Otmar D. Wiestler 《Virchows Archiv : an international journal of pathology》1998,432(5):477-481
A 62-year-old woman presented with loss of memory and a mild hemiparesis. Neuroradiology demonstrated a left frontoparietal
tumour. Biopsy specimens of this lesion revealed intracerebral Hodgkin’s lymphoma, a diagnosis supported by immunohistochemical
reactions of the tumour cells for the CD30 antigen. Additional cell cycle studies revealed a high proliferative activity of
the tumour cells in association with absence of apoptosis. There was no evidence that overexpression of bcl-2 or Epstein-Barr
virus infection was involved in the pathogenesis of this neoplasm. Lymphomas in the lung were detected 3 months later. Following
neurosurgical excision, radiotherapy, and chemotherapy, the patient had no evidence of Hodgkin’s disease after 13 months of
follow-up.
Received: 8 October 1997 / Accepted: 8 December 1997 相似文献
995.
S. D. Stocker B. C. Steinbacher Jr. C. D. Balaban B. J. Yates 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,116(2):270-282
A region of the caudal ventrolateral medullary reticular formation (CVLM) participates in baroreceptor, vestibulosympathetic,
and somatosympathetic reflexes; the adjacent retroambigual area is involved in generating respiratory-related activity and
is essential for control of the upper airway during vocalization. However, little is known about the connections of the CVLM
in the cat. In order to determine the locations of terminations of CVLM neurons, the anterograde tracers Phaseolus vulgaris leucoagglutinin and tetramethylrhodamine dextran amine were injected into this region. These injections produced a dense concentration
of labeled axons throughout the lateral medullary reticular formation (lateral tegmental field), including the retrofacial
nucleus and nucleus ambiguus, regions of the rostral ventrolateral medulla, the lateral and ventrolateral aspects of the hypoglossal
nucleus, nucleus intercalatus, and the facial nucleus. A smaller number of labeled axons were located in the medial, lateral,
and commissural subnuclei of nucleus tractus solitarius, the A5 region of the pontine reticular formation, the ventral and
medial portions of the spinal and motor trigeminal nuclei, locus coeruleus, and the parabrachial nucleus. We confirmed the
projection from the CVLM to both the rostral ventrolateral medulla and lateral tegmental field using retrograde tracing. Injections
of biotinylated dextran amine or Fluorogold into these regions resulted in retrogradely labeled cell bodies in the CVLM. However,
the neurons projecting to the lateral tegmental field were located mainly dorsal to those projecting to the rostral ventrolateral
medulla, suggesting that these neurons form two groups, possibly with different inputs. Injections of retrograde tracers into
the lateral tegmental field and rostral ventrolateral medulla also produced labeled cell bodies in other regions, including
the medial and inferior vestibular nuclei and nucleus solitarius. These data are consistent with the view that the CVLM of
the cat is a multifunctional area that regulates blood pressure, produces vocalization, affects the shape of the oral cavity,
and elicits contraction of particular facial muscles.
Received: 18 February 1997 / Accepted: 27 March 1997 相似文献
996.
本文分别应用标准12导联系统,Frank正交导联系统和改良Frank正交导联系统记录健康人36例、陈旧性心肌梗塞42例的心室碎裂电位,通过分析这些导联系统中相互垂直或近似垂直的导联上VFP的形态,数量关系,发现改良Frank正导联系统记录VFP较其它导联系统更科学,合理,且操作方便。 相似文献
997.
Dr. J. Wetzig K. Hofstetter-Degen R. von Baumgarten 《Journal of molecular medicine (Berlin, Germany)》1993,71(9):757-760
Summary Two subjects were rotated eccentrically in the manner described previously. In contrast to a normal control group, settings of a luminous line to the subjective vertical were almost unrelated to the gravitoinertial vector before, and totally so shortly after, space flight. Only 3 days postflight did a clear relation to the gravitoinertial vector re-establish itself in the one subject who actually flew. The correspondence became normal 5 days after the flight. Since there were no clinical abnormalities evident in the subjects, it is suggested that both subjects suppressed their vestibular information, presumably as an effect of vestibular deconditioning training before the flight. In addition, as a consequence of the flight experience one subject continued to ignore it several days after the flight.Abbreviations DARA
Deutsche Agentur für Raumfahrtangelegenheiten
- DLR
Deutsche Forschungsanstalt für Luft-und Raumfahrt
- ESA
European space agency
- ESTEC
European space research and technology centre
-
G
z
G-Units (9.81 m/s2) in z-axis direction
- L-xx
Launch minus xx days
- R+xx
Return
- VESTA
ESA Neurovestibular experiment facility 相似文献
998.
Y. Yamamoto T. Yamamoto P. Å. Öberg 《Medical & biological engineering & computing》1991,29(4):419-424
Electrode design and electrode positioning are important factors in blood flow measurements using impedance plethysmography.
Optimal electrode type and accurate positioning will decrease measurement errors and improve the signal-to-noise-ratio. Disk
electrodes were found to be superior to tape electrodes because of their better skin-electrode stability and because they
prevent limb compression. The distance between current electrodes and potential electrodes should be greater than 2·3 R (disk
electrodes) and 1·5 R (tape electrodes) to avoid the influence of the so-called diffusion resistance (R is the radius of the
limb at the electrode site). 相似文献
999.
1000.
A computerized decision support system is presented. The system is used to aid in the situation of patient selection for the purpose of dental education and utilizes the PERT/CPM methodology and decision tables. It runs on a microcomputer and written in Basic. The input is a list of patient's needs, and the output is a tentative treatment plan, the chair time needed to complete the treatment, its cost, and the probability that the student will finish it on time. 相似文献