全文获取类型
收费全文 | 10304篇 |
免费 | 729篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 94篇 |
儿科学 | 312篇 |
妇产科学 | 187篇 |
基础医学 | 1361篇 |
口腔科学 | 225篇 |
临床医学 | 1077篇 |
内科学 | 2357篇 |
皮肤病学 | 159篇 |
神经病学 | 1003篇 |
特种医学 | 255篇 |
外科学 | 1580篇 |
综合类 | 137篇 |
一般理论 | 4篇 |
预防医学 | 932篇 |
眼科学 | 152篇 |
药学 | 664篇 |
中国医学 | 18篇 |
肿瘤学 | 539篇 |
出版年
2023年 | 63篇 |
2021年 | 187篇 |
2020年 | 134篇 |
2019年 | 170篇 |
2018年 | 218篇 |
2017年 | 167篇 |
2016年 | 195篇 |
2015年 | 236篇 |
2014年 | 283篇 |
2013年 | 428篇 |
2012年 | 717篇 |
2011年 | 709篇 |
2010年 | 343篇 |
2009年 | 319篇 |
2008年 | 534篇 |
2007年 | 618篇 |
2006年 | 602篇 |
2005年 | 627篇 |
2004年 | 600篇 |
2003年 | 531篇 |
2002年 | 477篇 |
2001年 | 161篇 |
2000年 | 141篇 |
1999年 | 168篇 |
1998年 | 126篇 |
1997年 | 116篇 |
1996年 | 90篇 |
1995年 | 72篇 |
1994年 | 94篇 |
1993年 | 82篇 |
1992年 | 110篇 |
1991年 | 130篇 |
1990年 | 124篇 |
1989年 | 97篇 |
1988年 | 94篇 |
1987年 | 93篇 |
1986年 | 90篇 |
1985年 | 93篇 |
1984年 | 66篇 |
1983年 | 70篇 |
1982年 | 62篇 |
1981年 | 58篇 |
1980年 | 52篇 |
1979年 | 54篇 |
1978年 | 60篇 |
1976年 | 62篇 |
1975年 | 49篇 |
1974年 | 45篇 |
1973年 | 45篇 |
1972年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Human Disease Genes and Their Cloned Mouse Orthologs: Exploration of the FANTOM2 cDNA Sequence Data Set 下载免费PDF全文
112.
113.
Pontine parabrachial neurons have been suggested to play a regulatory role in both respiratory and sleep cycle control. Encouraged by the finding that microinjections of the cholinergic agonist carbachol into the medial pontine reticular formation (mPRF) of the cat produced respiratory changes paralleling those observed during rapid eye movement (REM) sleep (Neurosci. Lett., 102 (1989) 211–216), this study tested the hypothesis that cholinergic mechanisms in the mPRF can also cause state-dependent changes in the discharge of parabrachial neurons. This paper describes extracellular recordings of parabrachial neurons during REM sleep and during the carbachol-induced REM sleep-like state (DCarb). Cells which were activated (REM-on) or inactivated (REM-off) during REM maintained these same state-dependent firing patterns during the DCarb state. These results support the hypothesis that cholinergic mechanisms in the mPRF can cause state-dependent changes in the discharge of parabrachial neurons. 相似文献
114.
Ole Petter Ottersen Jon H. Laake Winfried Reichelt Finn-Mogens Haug Reidun Torp 《Journal of chemical neuroanatomy》1996,12(1):1-14
More than 10 years ago, it was shown by microdialysis that the excitatory transmitter glutamate accumulates in the interstitial space of brain subjected to ischemic insult. This was one of the key observations leading to the formulation of the `glutamate hypothesis' of ischemic cell death. It is now assumed that even a transient glutamate overflow may set in motion a number of events that ultimately cause cell loss in vulnerable neuronal populations. The aim of the present review is to discuss the intracellular changes that underlie the dysregulation of extracellular glutamate during and after ischemia, with emphasis on data obtained by postembedding, electron microscopic immunogold cytochemistry. While the time resolution of this approach is necessarily limited, it can reveal, quantitatively and at a high level of spatial resolution, how the intracellular pools of glutamate and metabolically related amino acids are perturbed during and after an ischemic insult. Moreover, this can be done in animals whose extracellular amino acid levels are monitored by microdialysis, allowing a direct correlation of extra- and intracellular changes. Immunogold analyses of brains subjected to ischemia have identified dendrites and neuronal somata as likely sources of glutamate efflux, probably mediated by reversal of glutamate uptake. The vesicular glutamate pool has been found to be largely unchanged after 20 min of ischemia. Ischemia causes an increased glutamate content and an increased glutamate/glutamine ratio in glial cells, as revealed by double immunogold labelling. This argues against the idea that glial cells contribute to the extracellular overflow of glutamate in the ischemic brain. 相似文献
115.
Henrik Ewald Ole Mors Tracey Flint Ursula Friedrich Hans Eiberg Torben A. Kruse 《American journal of medical genetics. Part A》1995,60(5):386-392
The long arm of chromosome 11 is one of the most interesting regions in the search for major genes involved in the etiology of manic-depressive illness. Several candidate genes have been identified, including the gene encoding the dopamine D2 receptor, the M1 muscarinic receptor, and porfobillinogen deaminase. Furthermore, different families with co-segregation of psychiatric illness and structural chromosome abnormalities involving regions 11q21, 11q22.3, and 11q25 have been reported. Using narrow as well as broad phenotypic models, conservative genetic parameters, models with dominant or recessive modes of inheritance, and various methods to reduce misclassification, the present study did not find evidence for a major gene causing manic-depressive illness on the long arm of chromosome 11. In the broader phenotypic models multi-point analyses excluded at least 11q14 to 11q23.3, approximately 60 cM, even in one large family. Assuming homogeneity close linkage to DRD2 was excluded for all dominant models, and also in the affecteds-only analyses in the large family alone. © 1995 Wiley-Liss, Inc. 相似文献
116.
D McCormick I Wallace J Kirk S Dinsmore I Allen 《British journal of experimental pathology》1983,64(1):103-115
A permanent cell line has been established from a human intracranial secondary melanoma. During 3 years of continuous growth in vitro the cells have maintained their characteristic phenotypic properties including melanin production. The cultured cells are highly tumorigenic in the athymic mouse and the tumours produced are histologically identical to the human tumour of origin. 相似文献
117.
Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r?r 0)·r 0 ?1, wherer is the vessels inner radius computed as (CSA · π?1)½ andr 0 is the radius of the vessel at a minimal distension pressure], the tension [(r·dP), wheredP is the transmural pressure difference], and the pressure elastic modulus (ΔP·r·Δr ?1). We found thatin vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of crror. Measurements were performed with consecutively increasing pressures in the range 1–25 kPa (8–188 mmHg, 0.01–0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm2; 25 kPa, mean 21.8 mm2) than in both the left circumflex (Cx) (4.5–16.0 mm2) and the right coronary artery (RCA) (2.8–15.6 mm2) (analysis of variance,P<0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P<0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P<0.001) and RCA (P<0.05). Impedance planimetry was applied to the study of coronary artery biomechanicsex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of anin vivo introduction of the method require additional evaluation. 相似文献
118.
Face processing differences have been observed between AS and control subjects at the behavioural and neurological levels. The purpose of the present study was to investigate the neurophysiological basis of processing faces and facial features (eyes and mouths) in adults with AS relative to age- and gender-matched typically-developing controls. These results were compared with ERPs generated to objects in both groups to determine if any differences were specific to facial stimuli. Although both groups elicited earlier N170 latencies to faces than to face parts and to eyes relative to mouths, adults with AS exhibited delayed N170 latencies to faces and face parts relative to controls. This difference was not observed to objects. Together these findings suggest that adults with AS may be slower to process facial information. 相似文献
119.
Milan Stevanovic George R. Wodicka Joe D. Bourland George P. Graber Kirk S. Foster Gary C. Lantz Willis A. Tacker Allen Cymerman 《Annals of biomedical engineering》1995,23(6):720-727
Although potentially fatal increases in intracranial pressure (ICP) can occur in a number of pathological conditions, there
is no reliable and noninvasive procedure to detect ICP elevation and quantitatively monitor changes over time. In this experimental
study, the relationships between ICP elevation and the vibrational response of the head were determined. An ovine animal model
was employed in which incremental increases in ICP were elicited and directly measured through intraventricular cannulae.
At each ICP increment, a vibration source elicited a flexural response of the animal's head that was measured at four locations
on the skull using accelerometers. Spectral analysis of the responses showed changes in proportion to ICP change up to roughly
20 cm H2O (15 mm Hg) above normal; a clinically significant range. Both magnitude and phase changes at frequencies between 4 and 7
kHz correlated well (γ>0.92) with ICP across the study group. These findings suggest that the vibrational response of the
head can be used to monitor changes in ICP noninvasively. 相似文献
120.
Nianhui Zhang Jon Laake Erlend Nagelhus Jon Storm-Mathisen Ole Petter Ottersen 《Anatomy and embryology》1991,184(3):213-223
Summary The cellular and subcellular localization of glutamine, a major glutamate precursor, was studied by means of an antiserum raised against glutaraldehydefixed glutamine. Ultrathin sections from the cerebellar cortex of rat and baboon (Papio anubis) were incubated sequentially in the primary antiserum and in a secondary antibody coupled to colloidal gold particles. The labelling intensity was quantified by computer-aided calculation of gold particle densities. High levels of immunoreactivity occurred in glial cells (Bergmann fibres, astrocytes, and oligodendrocytes), intermediate levels in cell bodies and processes of granule cells, and low levels in terminals of presumed GABAergic or glutamatergic fibres (terminals of basket and Golgi cells, and of parallel, mossy, and climbing fibres). The labelling intensity of Purkinje cells showed some variation, but never exceeded that in glial cells. Within the nerve fibre terminals, the glutamine-like immunoreactivity showed some preference for mitochondria, but was otherwise evenly distributed. The predominant glial localization of glutamine was also obvious in light microscopic preparations processed according to the postembedding peroxidase-antiperoxidase procedure. Gold particle densities over different types of profile in glutamine immunolabelled sections were compared with particle densities over the corresponding types of profiles in neighbouring sections labelled with an antiserum to glutaraldehyde-fixed glutamate. The glutamate/glutamine ratio, expressed arbitrarily by the ratio between the respective gold particle densities, varied by a factor of about 6, with the highest ratio in the putative glutamatergic mossy and parallel fibre terminals, and the lowest ratio in glial elements. The remaining tissue components displayed intermediate ratios. The present study provides direct morphological evidence for the existence in the brain of distinct compartments with differing glutamate/glutamine ratios.This paper is dedicated to Professor Fred Walberg on the occasion of his 70th birthdayOn leave of absence from Department of Anatomy, Capital Institute of Medicine, You An Men Street, Beijing, China 相似文献