全文获取类型
收费全文 | 8106篇 |
免费 | 486篇 |
国内免费 | 34篇 |
专业分类
耳鼻咽喉 | 48篇 |
儿科学 | 156篇 |
妇产科学 | 159篇 |
基础医学 | 1191篇 |
口腔科学 | 240篇 |
临床医学 | 694篇 |
内科学 | 1636篇 |
皮肤病学 | 201篇 |
神经病学 | 862篇 |
特种医学 | 437篇 |
外科学 | 1149篇 |
综合类 | 73篇 |
一般理论 | 3篇 |
预防医学 | 395篇 |
眼科学 | 333篇 |
药学 | 546篇 |
中国医学 | 17篇 |
肿瘤学 | 486篇 |
出版年
2023年 | 30篇 |
2022年 | 98篇 |
2021年 | 149篇 |
2020年 | 84篇 |
2019年 | 114篇 |
2018年 | 125篇 |
2017年 | 119篇 |
2016年 | 154篇 |
2015年 | 185篇 |
2014年 | 266篇 |
2013年 | 338篇 |
2012年 | 521篇 |
2011年 | 584篇 |
2010年 | 360篇 |
2009年 | 330篇 |
2008年 | 598篇 |
2007年 | 591篇 |
2006年 | 542篇 |
2005年 | 540篇 |
2004年 | 514篇 |
2003年 | 524篇 |
2002年 | 501篇 |
2001年 | 108篇 |
2000年 | 90篇 |
1999年 | 136篇 |
1998年 | 104篇 |
1997年 | 93篇 |
1996年 | 61篇 |
1995年 | 56篇 |
1994年 | 48篇 |
1993年 | 47篇 |
1992年 | 50篇 |
1991年 | 40篇 |
1990年 | 39篇 |
1989年 | 33篇 |
1988年 | 24篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 27篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 23篇 |
1977年 | 19篇 |
1976年 | 12篇 |
1974年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有8626条查询结果,搜索用时 17 毫秒
51.
Judith Nemeth Annie Galian Jacqueline Mikol Béatrix Cochand-Priollet Michel Wassef Anne Lavergne 《Virchows Archiv : an international journal of pathology》1987,412(1):89-93
Summary The immunoreactivity of polyclonal antiserum to neuron-specific enolase (NSE) has been investigated. Twenty-three cases of malignant lymphoma (ML) were studied and compared with previously published reports. In our study 11 out of 23 cases showed strong or weak NSE positivity; any type of ML could be positive or negative even among B or T cell ML. This study indicated that polyclonal NSE is not a specific marker; it might be an inconstant marker of ML with no apparent correlation between reactivity and morphology or phenotype. 相似文献
52.
Norbert T. Sandor Attila Brassai Attila Pliskas Balazs Lendvai 《Brain research bulletin》1995,36(5):483-486
The effect of the nitric oxide synthase inhibitor N-nitro-
-arginine methyl ester (L-NAME) on the basal and stimulation-evoked release of dopamine (DA) and acetylcholine (ACh) was investigated in rat striatum. The experiments were carried out in isolated superfused striatal slices, loaded with either [3H]-dopamine or [3H]-choline.We have found that L-NAME reduced the elecrical field stimulation-evoked release of DA, while its enantiomer N-nitro-D-arginine methyl ester (D-NAME) was ineffective. In the presence of the nitric oxide (NO) precursor
-arginine L-NAME failed to influence DA release. Furthermore, treatment with the N-methyl-
-aspartate (NMDA) receptor antagonist MK-801 completely reversed the effect of L-NAME on striatal DA release. In contrast, L-NAME had no effect on either the basal or the stimulation-evoked ACh release in any experimental conditions studied.Our data indicate that endogenously produced NO is involved in the modulation of striatal DA, but not in ACh release. Furthermore, it seems likely that the modulatory effect of NO is linked to activation of presynaptic NMDA receptors located on the striatal dopaminergic nerve terminals. 相似文献
53.
Dara L. Kraitchman Norbert Wilke Erik Hexeberg Michael Jerosch-Herold Ying Wang Todd B. Parrish Cheng-Ning Chang Yi Zhang Robert J. Bache Leon Axel 《Magnetic resonance in medicine》1996,35(5):771-780
MRI studies of first-pass contrast enhancement with polylysine-Gd-DTPA and myocardial tagging using spatial modulation of magnetization (SPAMM) were performed to assess the feasibility of a combined regional myocardial blood flow and 2D deformation exam. Instrumented closed-chest dogs were imaged at a baseline control state (Cntl) followed by two interventions: moderate coronary stenosis (St) achieved by partial occlusion of the left anterior descending (LAD) and moderate coronary stenosis with dobutamine loading (StD). Hypoperfusion of the anterior region (ANT) of the myocardium (LAD distribution) relative to the posterior wall (POS) based on the upslope of the signal intensity time curve from the contrast-enhanced MR images was demonstrated only with dobutamine loading (ANT:POS Cntl=1.077 ± 0.15 versus ANT:POS StD=0.477 ± 0.11, P<0.03) and was confirmed with radio-labeled microspheres measurements (ANT:POS Cntl=1.18 ± 0.2 ml/min/g versus ANT:POS StD=0.44 ± 0.1 ml/min/g; P<0.002). Significant changes in regional myocardial shortening were only seen in the StD state (P<0.02); the anterior region showed impaired myocardial shortening with dobutamine loading (P=NS), whereas the nonaffected POS region showed a marked increase in shortening when compared with Cntl (Cntl=0.964 ± 0.02 versus StD=0.884 ± 0.03; P<0.001). These results demonstrate that an integrated quantitative assessment of regional myocardial function and semiquantitative assessment of myocardial blood flow can be performed noninvasively with ultrafast MRI. 相似文献
54.
Functional analysis of the cag pathogenicity island in Helicobacter pylori isolates from patients with gastritis, peptic ulcer, and gastric cancer 总被引:9,自引:0,他引:9 下载免费PDF全文
Backert S Schwarz T Miehlke S Kirsch C Sommer C Kwok T Gerhard M Goebel UB Lehn N Koenig W Meyer TF 《Infection and immunity》2004,72(2):1043-1056
Helicobacter pylori is the causative agent of a variety of gastric diseases, but the clinical relevance of bacterial virulence factors is still controversial. Virulent strains carrying the cag pathogenicity island (cagPAI) are thought to be key players in disease development. Here, we have compared cagPAI-dependent in vitro responses in H. pylori isolates obtained from 75 patients with gastritis, peptic ulcer, and gastric cancer (n = 25 in each group). AGS gastric epithelial cells were infected with each strain and assayed for (i) CagA expression, (ii) translocation and tyrosine phosphorylation of CagA, (iii) c-Src inactivation, (iv) cortactin dephosphorylation, (v) induction of actin cytoskeletal rearrangements associated with cell elongation, (vi) induction of cellular motility, and (vii) secretion of interleukin-8. Interestingly, we found high but similar prevalences of all of these cagPAI-dependent host cell responses (ranging from 56 to 80%) among the various groups of patients. This study revealed CagA proteins with unique features, CagA subspecies of various sizes, and new functional properties for the phenotypic outcomes. We further showed that induction of AGS cell motility and elongation are two independent processes. Our data corroborate epidemiological studies, which indicate a significant association of cagPAI presence and functionality with histopathological findings in gastritis, peptic ulcer, and gastric cancer patients, thus emphasizing the importance of the cagPAI for the pathogenicity of H. pylori. Nevertheless, we found no significant association of the specific H. pylori-induced responses with any particular patient group. This may indicate that the determination of disease development is highly complex and involves multiple bacterial and/or host factors. 相似文献
55.
Horst Friebolin Norbert Frank Gunda Keilich Egon Siefert 《Macromolecular chemistry and physics.》1976,177(3):845-858
The 13C-NMR spectra of malto- and isomalto-oligosaccharides, amylose and dextrane were analysed. It was observed that in both series of oligosaccharides and polysaccharides the resonances of the central glucose units are independent of the chain length with the exception of the C-atoms 1 and 4 of amylose which show deviations of 0,4 and 0,5 ppm. These small effects can possibly be explained by a definite polysaccharide chain conformation in solution. 相似文献
56.
Joel D. Schiff Norbert I. A. Overweg 《Pflügers Archiv : European journal of physiology》1980,389(1):75-79
The effects of changing bathing medium osmolality on tension generation in smooth muscle were studied on potassium-depolarized segments of rat ileum. Increasing the tonicity of the medium evokes a transient relaxation of the smooth muscle; restoration of isotonicity evokes a transient contraction of similar amplitude and time course. While immersed in hypertonic media of less than 1.3 times normal tonicity, the smooth muscle slowly increases its isometric tension; in media of nearly twice normal tonicity, the smooth muscle loses tension. All of these effects occur whether the medium is made hypertonic with added NaCl or sucrose. 相似文献
57.
René?G?ddeEmail author Stefanie?Brune Peter?Jagiello Eckhart?Sindern Michael?Haupts Sebastian?Schimrigk Norbert?Müller J?rg?T?Epplen 《Journal of negative results in biomedicine》2005,4(1):7
Apoptosis, the programmed death of cells, plays a distinct role in the etiopathogenesis of Multiple sclerosis (MS), a common
disease of the central nervous system with complex genetic background. Yet, it is not clear whether the impact of apoptosis
is due to altered apoptotic behaviour caused by variations of apoptosis-related genes. Instead, apoptosis in MS may also represent
a secondary response to cellular stress during acute inflammation in the central nervous system. Here, we screened 202 apoptosis-related
genes for association by genotyping 202 microsatellite markers in initially 160 MS patients and 160 controls, both divided
in 4 sets of pooled DNA samples, respectively. When applying Bonferroni correction, no significant differences in allele frequencies
were detected between MS patients and controls. Nevertheless, we chose 7 markers for retyping in individual DNA samples, thereby
eliminating 6 markers from the list of candidates. The remaining candidate, the ERBB3 gene microsatellite, was genotyped in additional 245 MS patients and controls. No association of the ERBB3 marker with the disease was detected in these additional cohorts. In consequence, we did not find further evidence for apoptosis-related
genes as predisposition factors in MS. 相似文献
58.
Deckert M Lütjen S Leuker CE Kwok LY Strack A Müller W Wagner N Schlüter D 《European journal of immunology》2003,33(5):1418-1428
Under various inflammatory conditions, cell adhesion molecules are up-regulated in the central nervous system (CNS) and may contribute to the recruitment of leukocytes to the brain. In the present study, the functional role of vascular cell adhesion molecule (VCAM)-1 in Toxoplasma encephalitis (TE) was addressed using VCAM(flox/flox MxCre) mice. Neonatal inactivation of the VCAM-1 gene resulted in a lack of induction of VCAM-1 on cerebral blood vessel endothelial cells, whereas the constitutive expression of VCAM-1 on choroid plexus epithelial cells and the ependyma was unaffected; in these animals, resistance to T. gondii was abolished, and VCAM(flox/flox MxCre) mice died of chronic TE caused by a failure to control parasites in the CNS. Although leukocyte recruitment to the CNS was unimpaired, the B cell response was significantly reduced as evidenced by reduced serum levels of anti-T. gondii-specific IgM and IgG antibodies. Furthermore, the frequency and activation state of intracerebral T. gondii-specific T cells were decreased, and microglial activation was markedly reduced. Taken together, these data demonstrate the crucial requirement of VCAM-1-mediated immune reactions for the control of an intracerebral infectious pathogen, whereas other cell adhesion molecules can efficiently compensate for VCAM-1-mediated homing across cerebral blood vessels. 相似文献
59.
Norbert B Ghyselinck Nadège Vernet Christine Dennefeld Norbert Giese Heinz Nau Pierre Chambon Stéphane Viville Manuel Mark 《Developmental dynamics》2006,235(6):1608-1622
Using Rbp4-null mice as models, we have established for the first time the kinetics of the spermatogenetic alterations during vitamin A deficiency (VAD). Our data demonstrate that the VAD-induced testicular degeneration arises through the normal maturation of germ cells in a context of spermatogonia differentiation arrest. They indicate that retinoic acid (RA) appears dispensable for the transition of premeiotic to meiotic spermatocytes, meiosis, and spermiogenesis. They confirm that RA plays critical roles in controlling spermatogonia differentiation, spermatid adhesion to Sertoli cells, and spermiation, and suggest that the VAD-induced arrest of spermatogonia differentiation results from simultaneous blocks in RA-dependent events mediated by RA receptor gamma (RARgamma) in spermatogonia and by RARalpha in Sertoli cells. They also provide evidence that expression of major RA-metabolizing enzymes is increased in mouse Sertoli cells upon VAD and that vitamin A-deficient A spermatogonia differ from their RA-sufficient counterparts by the expression of the Stra8 gene. 相似文献
60.
Heymann MF Joubert M Nemeth J Franc B Visset J Hamy A le Borgne J le Neel JC Murat A Cordel S le Bodic MF 《Histopathology》2000,36(5):421-432
AIMS: To study the clinical outcome of 82 cases of pancreatic neuroendocrine tumours classified according to the recent histological and prognostic classification of Capella. METHODS AND RESULTS: Eighty-two surgical cases of pancreatic neuroendocrine tumours were examined histologically with immunohistochemical staining of paraffin sections using streptavidin-biotin complex and application of antibodies against chromogranin A and 10 hormonal peptides. Classification in four groups correlated with long follow-up and outcome of these cases. Histological examination showed 30 group I, four group II, 41 group III and seven group IV tumours. Twenty-one (70%) of group I tumours were insulinomas, whereas 25% of group III tumours were glucagonomas and 25% were unclassified. Most group IV tumours were unclassified, showing no immunohistochemical staining with any of the 10 hormonal peptides tested. Outcome was clearly correlated with tumour group. Among the 14 patients who died of the disease, four had group IV and 10 group III tumours. Thus, unclassified asymptomatic tumours without immunohistochemical staining had a poorer prognosis than asymptomatic tumours with staining. CONCLUSION: This study validates the Capella classification as easy to apply and useful in predicting clinical outcome. 相似文献