全文获取类型
收费全文 | 8090篇 |
免费 | 586篇 |
国内免费 | 55篇 |
专业分类
耳鼻咽喉 | 35篇 |
儿科学 | 177篇 |
妇产科学 | 165篇 |
基础医学 | 1369篇 |
口腔科学 | 191篇 |
临床医学 | 807篇 |
内科学 | 1798篇 |
皮肤病学 | 234篇 |
神经病学 | 937篇 |
特种医学 | 214篇 |
外科学 | 823篇 |
综合类 | 25篇 |
一般理论 | 5篇 |
预防医学 | 526篇 |
眼科学 | 113篇 |
药学 | 614篇 |
中国医学 | 10篇 |
肿瘤学 | 688篇 |
出版年
2024年 | 18篇 |
2023年 | 131篇 |
2022年 | 238篇 |
2021年 | 396篇 |
2020年 | 247篇 |
2019年 | 296篇 |
2018年 | 295篇 |
2017年 | 248篇 |
2016年 | 267篇 |
2015年 | 265篇 |
2014年 | 377篇 |
2013年 | 433篇 |
2012年 | 677篇 |
2011年 | 608篇 |
2010年 | 356篇 |
2009年 | 343篇 |
2008年 | 526篇 |
2007年 | 476篇 |
2006年 | 481篇 |
2005年 | 460篇 |
2004年 | 391篇 |
2003年 | 363篇 |
2002年 | 316篇 |
2001年 | 68篇 |
2000年 | 44篇 |
1999年 | 58篇 |
1998年 | 65篇 |
1997年 | 52篇 |
1996年 | 35篇 |
1995年 | 38篇 |
1994年 | 23篇 |
1993年 | 17篇 |
1992年 | 24篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1907年 | 2篇 |
1906年 | 3篇 |
1905年 | 3篇 |
1904年 | 2篇 |
1903年 | 4篇 |
排序方式: 共有8731条查询结果,搜索用时 15 毫秒
31.
Dopamine in the orbitofrontal cortex regulates operant responding under a progressive ratio of reinforcement in rats 总被引:3,自引:0,他引:3
Prefrontocortical dopamine (DA) plays an essential role in the regulation of cognitive functions and behavior. The orbitofrontal cortex (OFC) receives a dopaminergic projection from the ventral tegmental area and is particularly important for goal-directed appetitive behaviors and for the neural representation of reward value. We here examined the effects of DA receptor blockers locally infused into the OFC, on instrumental behavior under a progressive schedule of reinforcement. After continuous reinforcement training (lever pressing for casein pellets) rats received bilateral intra-OFC-infusions of the DA D1-receptor antagonist SCH23390 (3 μg/0.5 μl), the DA D2-receptor antagonist sulpiride (3 μg/0.5 μl), or phosphate buffered saline through chronically indwelling cannulae. Immediately after infusion they were tested under a time-constrained progressive ratio schedule of reinforcement (3, 6, 9, 12, … lever presses for 1 casein pellet within 180 s). Both SCH23390 and sulpiride led to a significant reduction of the break point (cessation to respond to the increasing criterion of instrumental effort) compared to vehicle infusions. A food preference test revealed no drug effects on the amount of consumed pellets and on the preference of casein pellets over laboratory chow. Leftward shifts of the break point in progressive ratio tasks indicate a disturbance of the mechanisms that translate motivation into appetitive behavior under conditions of increasing instrumental effort. Therefore, our data indicate that orbitofrontal dopamine is necessary for reward-related instrumental behavior. 相似文献
32.
Collagen type I as a robust fibre protein and main component of the extracellular matrix of most tissues is increasingly utilized for surface engineering of biomaterials using different immobilization methods. In the present work we studied the mineralization behaviour of fibrillar collagen type I in simulated body fluid as a measure for conformational changes caused by adsorptive immobilization or immobilization by partial incorporation into the anodic oxide layer on c.p.-titanium using microscopic and vibration spectroscopic methods. Adsorptive immobilization on highly oriented pyrolytic graphite (HOPG) and c.p.-titanium without collagen were used as references. In the initial phase (1-24 h) the kinetics of formation and the morphology of calcium phosphate phases (CPP) are strongly influenced both by the substrate and the immobilization method. Compared to HOPG both types of immobilization on titanium increasingly inhibit the formation of CPP. For longer times (30 d) these initial differences disappear-mineralization product on titanium, irrespective of the presence of collagen, is a mixture of amorphous calcium phosphate and octacalcium phosphate. Contrary to this the mineralization of HOPG substrates results in hydroxy apatite. This is discussed with respect to the conditions during the immobilization as well as the resulting interactions between substrate and immobilized collagen. It is shown that the mineralization process exhibits a high sensitivity with respect to conformational changes caused by these interactions. Possible cell biological relevance of these conformational changes is discussed. 相似文献
33.
Alja Videtic Galina Pungercic Irena Zupanic Pajnic Tomaz Zupanc Joze Balazic Martina Tomori Radovan Komel 《American journal of medical genetics. Part B, Neuropsychiatric genetics》2006,(6):669-672
A number of molecular genetic studies have investigated if serotonin (5-HT) receptor subtypes are involved in the pathogenesis of depression, suicidal behavior, aggression, and impulsive behavior. Existence of many receptor subtypes for a single transmitter permits a great diversity of signaling raising the possibility that they may serve as genetic markers for suicidal behavior. Most previous studies of suicide have analyzed polymorphisms of the receptors 5-HT1A, 5-HT1B, 5-HT2A, fewer have examined 5-HT1F. We report a study of possible association between the polymorphisms in the 5-HT receptor genes (1A, 1B, 1F, and 2A) and suicidal behavior on a sample of 226 suicide victims and 225 healthy control subjects. No significant differences in genotype frequency distributions between the suicide victims and healthy control subjects were observed for four polymorphisms; three were not polymorphic. A single polymorphism, C-1420T in gene 5-HT2A, showed a slight association with suicide (chi2= 4.94, df = 2, P = 0.067), but the correlation was not statistically significant. None of the tested genetic variants of serotonin receptors appears to be associated with suicidal behavior in the Slovenian population which has a relatively high suicide rate. 相似文献
34.
35.
BACKGROUND: Long-term post-menopausal hormone therapy (pHT) was often regarded as first-line therapy to prevent fractures in post-menopausal women, a recommendation under scrutiny given the benefit-risk profile of the Women's Health Initiative results of the estrogen-progestin combination. Apart from controlled clinical studies providing data with fractures as an end point, measures of lumbar and hip bone mineral density (BMD) may be used to assess bone-related effects of pHT. The objective of this study was to conduct a systematic review of 2-year trials, published between 1990 and December 2002, and assessing changes in BMD by any estrogen including ethinyl estradiol, any estrogen plus any progestin, or tibolone. METHODS: We searched MEDLINE, EMBASE and systematic reviews. Thirty-nine randomized, prospective, controlled 2-year trials were analysed in pre-specified groups according to the profile of the compounds. RESULTS: Virtually all pHT regimens at least maintain BMD at the lumbar spine and the hip compared with baseline; there is no apparent difference between the various estrogenic compounds. Tibolone, a synthetic progestin, appears to be as effective as any estrogen. Most trials were conducted in early post-menopausal women, fewer in women with hysterectomy and/or bilateral oophorectomy. CONCLUSIONS: The size of impact on BMD does not appear to differ between tibolone and any estrogen compound studied. 相似文献
36.
Lugli A Forster Y Haas P Nocito A Bucher C Bissig H Mirlacher M Storz M Mihatsch MJ Sauter G 《Human pathology》2003,34(10):994-1000
Calretinin is a calcium-binding protein expressed in different normal and neoplastic tissues. Early studies suggested that calretinin is a useful marker to differentiate adenocarcinomas from malignant mesotheliomas of the lung, but subsequent work has shown that calretinin can be expressed in several other tumor types. To systematically investigate the epidemiology of calretinin expression in normal and neoplastic tissues, we used tissue microarrays (TMAs) to analyze the immunohistochemically detectable expression of calretinin in 5233 tissue samples from 128 different tumor categories and 76 different normal tissue types. At least 1 case with weak expression could be found in 74 of 128 (58%) different tumor types and 46 entities (36%) had at least 1 tumor with strong positivity. In normal tissues, a particularly strong expression was found in Leydig cells of the testis, neurons of the brain, theca-lutein and theca interna cells of the ovary, and mesothelium. In tumors, strong calretinin expression was most frequently found in malignant mesotheliomas (6 of 7), Leydig cell tumors of the testis (5 of 5), adenomas of adrenal gland (5 of 9), and adenomatoid tumors (4 of 9). In summary, calretinin is frequently expressed in many different tumor types. Metastases of various different origins must be included in the differential diagnosis of calretinin-positive pleura tumors. 相似文献
37.
38.
Montesinos-Rongen M Akasaka T Zühlke-Jenisch R Schaller C Van Roost D Wiestler OD Siebert R Deckert M 《Brain pathology (Zurich, Switzerland)》2003,13(4):534-538
Primary central nervous system lymphomas (PCNSL) constitute diffuse large B-cell lymphomas arising in and remaining confined to the brain. Little information is available on cytogenetic changes in PCNSL, and recurrent chromosomal translocations have not yet been identified. Fluorescence in situ hybridization (FISH) of a series of 13 PCNSL from immunocompetent patients revealed 3 cases with signal patterns of a BCL6-specific probe suggesting a breakpoint in this oncogene locus in chromosome band 3q27. Here, we describe cloning of the translocation breakpoints by long-distance inverse polymerase chain reaction (LDI-PCR) in 2 of these tumors. Both breakpoints affected the first intron of BCL6. In one PCNSL, the HSPCA (HSP90A) gene in 14q32.31 was identified as BCL6 partner. In the second lymphoma, the gene encoding glyceraldehyde-3-phosphate dehydrogenase (GAPD) on 12p13.31 was detected as a hitherto unknown partner of BCL6. Our results suggest translocation-mediated BCL6 oncogene activation as a so far unknown pathogenetically relevant mechanism in PCNSL. 相似文献
39.
Ludewig K Ludewig S Seitz A Obrist M Geyer MA Vollenweider FX 《Biological psychology》2003,63(3):311-323
The acoustic startle reflex and its modulation by prepulse inhibition (PPI) and habituation are used in many studies in different fields of neuropsychiatric research. The aim of this study was to examine the effects of age and gender on PPI, startle magnitude, and habituation in healthy human volunteers. Twenty-seven male and 28 female participants of four different age groups (range: 20-60 years) were investigated in an acoustic startle paradigm using a startle stimulus of 115 dB and a prepulse of 86 dB (16 dB over the white noise background) with five different lead intervals (30, 60, 120, 240, and 2000 ms). Seventeen males and 16 female participants were tested three times at monthly intervals. Aged participants showed significantly lower startle magnitude and significantly more habituation than younger participants, but there was no effect of age on PPI or prepulse facilitation. Moreover, there were no effects of gender on startle magnitude, PPI, prepulse facilitation, or habituation measures. Healthy males and females exhibited stable startle magnitudes and PPI across sessions. The results demonstrated that PPI and startle are reliable measures of sensory information processing in both genders and that startle magnitude and habituation are age-dependent measures. 相似文献
40.
Alessandro Antonelli Mario Rotondi Poupak Fallahi Paola Romagnani Silvia Martina Ferrari Ele Ferrannini Mario Serio 《Journal of interferon & cytokine research》2005,25(9):547-552
Circulating levels of cytokines are deeply influenced by aging, and few data about serum chemokines are available. The aim of this study was to evaluate the influence of aging on circulating CXCL10. One hundred forty healthy subjects (70 males and 70 females), 10-79 years of age, underwent fasting plasma glucose, total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglyceride, and CXCL8 serum assay. Thyroid hormone testing for thyroid-stimulating hormone (TSH), antithyroglobulin (AbTg), and antithyroperoxidase (AbTPO) autoantibodies and thyroid ultrasonography were performed in all subjects to exclude the presence of clinical or subclinical thyroid disease. Serum CXCL10 levels were assayed in all subjects and found to be increased in 14 of 70 females (20%) and in 4 of 70 males (5.7%) (p = 0.01). In a multiple linear regression model including age, body mass index (BMI), systolic and diastolic blood pressure, glycemia, total cholesterol, HDL, LDL, triglycerides, TSH, AbTPO, AbTg, and CXCL8, only age was significantly related to CXCL10 [C.R. 1.30 (0.28-2.33), p = 0.001]. No relationship was present between CXCL8 serum levels and age, suggesting a specificity of CXCL10 elevation as a function of age. Results of this study, performed in healthy subjects on an age gradient, demonstrate an increase in serum CXCL10 with advancing age overall in females, supporting the hypothesis of enhanced Th1 immune responses in aging. 相似文献