全文获取类型
收费全文 | 19298篇 |
免费 | 1077篇 |
国内免费 | 155篇 |
专业分类
耳鼻咽喉 | 155篇 |
儿科学 | 378篇 |
妇产科学 | 293篇 |
基础医学 | 2396篇 |
口腔科学 | 574篇 |
临床医学 | 1980篇 |
内科学 | 4154篇 |
皮肤病学 | 397篇 |
神经病学 | 2354篇 |
特种医学 | 1335篇 |
外科学 | 2959篇 |
综合类 | 97篇 |
一般理论 | 7篇 |
预防医学 | 636篇 |
眼科学 | 407篇 |
药学 | 1033篇 |
中国医学 | 13篇 |
肿瘤学 | 1362篇 |
出版年
2024年 | 14篇 |
2023年 | 155篇 |
2022年 | 318篇 |
2021年 | 541篇 |
2020年 | 353篇 |
2019年 | 412篇 |
2018年 | 505篇 |
2017年 | 443篇 |
2016年 | 576篇 |
2015年 | 650篇 |
2014年 | 802篇 |
2013年 | 928篇 |
2012年 | 1474篇 |
2011年 | 1460篇 |
2010年 | 967篇 |
2009年 | 889篇 |
2008年 | 1320篇 |
2007年 | 1439篇 |
2006年 | 1198篇 |
2005年 | 1210篇 |
2004年 | 1151篇 |
2003年 | 1077篇 |
2002年 | 956篇 |
2001年 | 172篇 |
2000年 | 135篇 |
1999年 | 178篇 |
1998年 | 167篇 |
1997年 | 134篇 |
1996年 | 110篇 |
1995年 | 78篇 |
1994年 | 67篇 |
1993年 | 70篇 |
1992年 | 59篇 |
1991年 | 54篇 |
1990年 | 29篇 |
1989年 | 42篇 |
1988年 | 46篇 |
1987年 | 29篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 24篇 |
1983年 | 25篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 21篇 |
1977年 | 17篇 |
1974年 | 12篇 |
1972年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 3 毫秒
951.
952.
Attempted replication of reported chronic obstructive pulmonary disease candidate gene associations 总被引:6,自引:0,他引:6
Hersh CP Demeo DL Lange C Litonjua AA Reilly JJ Kwiatkowski D Laird N Sylvia JS Sparrow D Speizer FE Weiss ST Silverman EK 《American journal of respiratory cell and molecular biology》2005,33(1):71-78
Case-control studies have successfully identified many significant genetic associations for complex diseases, but lack of replication has been a criticism of case-control genetic association studies in general. We selected 12 candidate genes with reported associations to chronic obstructive pulmonary disease (COPD) and genotyped 29 polymorphisms in a family-based study and in a case-control study. In the Boston Early-Onset COPD Study families, significant associations with quantitative and/or qualitative COPD-related phenotypes were found for the tumor necrosis factor (TNF)-alpha -308G>A promoter polymorphism (P < 0.02), a coding variant in surfactant protein B (SFTPB Thr131Ile) (P = 0.03), and the (GT)(31) allele of the heme oxygenase (HMOX1) promoter short tandem repeat (P = 0.02). In the case-control study, the SFTPB Thr131Ile polymorphism was associated with COPD, but only in the presence of a gene-by-environment interaction term (P = 0.01 for both main effect and interaction). The 30-repeat, but not the 31-repeat, allele of HMOX1 was associated (P = 0.04). The TNF -308G>A polymorphism was not significant. In addition, the microsomal epoxide hydrolase "fast" allele (EPHX1 His139Arg) was significantly associated in the case-control study (P = 0.03). Although some evidence for replication was found for SFTPB and HMOX1, none of the previously published COPD genetic associations was convincingly replicated across both study designs. 相似文献
953.
Epithelial-mesenchymal transition in colonies of rhesus monkey embryonic stem cells: a model for processes involved in gastrulation 总被引:2,自引:0,他引:2
Rhesus monkey embryonic stem (rhES) cells were grown on mouse embryonic fibroblast (MEF) feeder layers for up to 10 days to form multilayered colonies. Within this period, stem cell colonies differentiated transiently into complex structures with a disc-like morphology. These complex colonies were characterized by morphology, immunohistochemistry, and marker mRNA expression to identify processes of epithelialization as well as epithelial-mesenchymal transition (EMT) and pattern formation. Typically, differentiated colonies were comprised of an upper and a lower ES cell layer, the former growing on top of the layer of MEF cells whereas the lower ES cell layer spread out underneath the MEF cells. Interestingly, in the central part of the colonies, a roundish pit developed. Here the feeder layer disappeared, and upper layer cells seemed to ingress and migrate through the pit downward to form the lower layer while undergoing a transition from the epithelial to the mesenchymal phenotype, which was indicated by the loss of the marker proteins E-cadherin and ZO-1 in the lower layer. In support of this, we found a concomitant 10-fold upregulation of the gene Snail2, which is a key regulator of the EMT process. Conversion of epiblast to mesoderm was also indicated by the regulated expression of the mesoderm marker Brachyury. An EMT is a characteristic process of vertebrate gastrulation. Thus, these rhES cell colonies may be an interesting model for studies on some basic processes involved in early primate embryogenesis and may open new ways to study the regulation of EMT in vitro. 相似文献
954.
Structural and functional asymmetry of lateral Heschl's gyrus reflects pitch perception preference 总被引:1,自引:0,他引:1
Schneider P Sluming V Roberts N Scherg M Goebel R Specht HJ Dosch HG Bleeck S Stippich C Rupp A 《Nature neuroscience》2005,8(9):1241-1247
The relative pitch of harmonic complex sounds, such as instrumental sounds, may be perceived by decoding either the fundamental pitch (f0) or the spectral pitch (fSP) of the stimuli. We classified a large cohort of 420 subjects including symphony orchestra musicians to be either f0 or fSP listeners, depending on the dominant perceptual mode. In a subgroup of 87 subjects, MRI (magnetic resonance imaging) and magnetoencephalography studies demonstrated a strong neural basis for both types of pitch perception irrespective of musical aptitude. Compared with f0 listeners, fSP listeners possessed a pronounced rightward, rather than leftward, asymmetry of gray matter volume and P50m activity within the pitch-sensitive lateral Heschl's gyrus. Our data link relative hemispheric lateralization with perceptual stimulus properties, whereas the absolute size of the Heschl's gyrus depends on musical aptitude. 相似文献
955.
Waniek PJ Hendgen-Cotta UB Stock P Mayer C Kollien AH Schaub GA 《Parasitology research》2005,97(6):486-500
After the previous characterization of one trypsin gene (Try1) of the human body louse Pediculus humanus, genes encoding a second trypsin (Try2) and a chymotrypsin (Chy1) have been cloned using degenerate serine proteinase primers and 5- and 3-RACE, and sequenced. The deduced 259 and 267 amino acid sequences of Try2 and Chy1 show an identity of 33%–40% to trypsinogens and chymotrypsinogens of other insects. Considering previously published partial sequences, P. humanus possesses at least one Try1 gene, five variants/isoforms of Try2 and six variants/isoforms of Chy1. The genomic DNA of Try2 contains three introns and Chy1 contains five introns. Using whole mount in situ hybridization, gene expression of Try1, Try2 and Chy1 has been localized not only in the distensible anterior region of the midgut of lice but sometimes also in the area following the distensible region. The Try2 gene was always expressed at much lower levels than Try1 or Chy1. This lower expression, the constitutive expression of Try1 and Chy1 at 1, 2, 6, 12 and 24 h after feeding of adults and the regional differences have been verified in quantitative real-time PCR. 相似文献
956.
Immunohistochemistry in bone marrow pathology: a useful adjunct for morphologic diagnosis 总被引:1,自引:0,他引:1
Kremer M Quintanilla-Martínez L Nährig J von Schilling C Fend F 《Virchows Archiv : an international journal of pathology》2005,447(6):920-937
Pathomorphological examination of trephine biopsies of the bone marrow (BM) represents a standard method for the diagnosis
and staging of hematologic neoplasms and other disorders involving the BM. The increasing knowledge about the genetic basis
and biology of hematologic neoplasms, as well as the recently proposed WHO classification system, provide the framework for
an accurate diagnosis. Although conventional morphology remains the gold standard for paraffin-embedded BM trephines, immunohistochemical
stainings have become an integral part of the diagnostic workup. Antibodies suitable for paraffin sections are generally applicable
to BM trephines, but modifications of staining protocols may be necessary due to the alternative fixatives and decalcification
procedures used for BM biopsies. The indications for immunostainings range from confirmation and classification of lymphoma
involvement, subclassification of acute leukemias, and estimating blast counts in myelodysplastic and myeloproliferative syndromes
to characterization of BM involvement in nonhematologic neoplasms. Although subtyping of NHL in the BM is more difficult from
the point of morphology, classification of the entities that frequently involve the BM, especially the small B-cell lymphomas,
can easily be achieved with the help of immunohistochemistry. In this review, we try to summarize the current state of the
art in BM immunohistochemistry for the diagnosis of hematologic disorders. Moreover, diagnostic algorithms and useful antibody
panels are proposed for a rational and cost-effective approach. 相似文献
957.
The present study examined the association of the Tyrosine hydroxylase Val-81-Met polymorphism with alcohol dependence. One hundred and fifty-nine patients in a psychiatric unit with alcohol dependence were genotyped as well as 92 healthy volunteers. The Val allele was more frequent in patients with alcohol dependence (69.5%) than in controls (62.5%). This effect was largely due to the association with early-onset alcoholism (77.8%), whereas no difference was noted between late-onset patients and controls. Our results suggest a role for tyrosine hydroxylase in early-onset alcoholism. 相似文献
958.
Kremer M Ott G Nathrath M Specht K Stecker K Alexiou C Quintanilla-Martinez L Fend F 《The Journal of pathology》2005,205(1):92-101
Primary extramedullary plasmacytomas are infrequent, typically solitary, plasma cell neoplasms that generally pursue an indolent clinical course but may, rarely, convert to multiple myeloma. Phenotypic differences between these two entities are not well defined. Twenty-eight cases of primary extramedullary plasmacytoma and 26 cases of both medullary (n = 17) and extramedullary (n = 9) multiple myeloma were analysed for the expression of proteins known to play a role in the biology of multiple myeloma. Immunohistochemistry was performed on paraffin wax sections using antibodies against cyclin D1, Bcl-2, Bcl-xL, p27, p21, p53, MIB1, CD20, and CD56. Twenty-three extramedullary plasmacytomas were localized in the upper aerodigestive tract, four in the lymph nodes, and one in the testis. There was a strong male predominance (M : F = 6 : 1). None of the patients died from the disease or progressed to multiple myeloma (mean follow-up 50 months). Nine patients developed local relapse and one patient's tumour evolved into a B-cell non-Hodgkin's lymphoma. In contrast to both intra- and extra-medullary multiple myeloma, extramedullary plasmacytoma showed absence of cyclin D1 (p < 0.001) and infrequent expression of CD56 (p < 0.001). Furthermore, extramedullary plasmacytomas were characterized by weaker staining for Bcl-2 protein and rare overexpression of p21 and p53. In comparison to extramedullary multiple myeloma, extramedullary plasmacytoma showed a more mature morphology and lower proliferation indices (p = 0.008). There was no association between the phenotypic parameters investigated and clinical outcome in extramedullary plasmacytoma. In summary, extramedullary plasmacytoma and multiple myeloma show significant immunophenotypic differences, some of which may be of both diagnostic utility and biological relevance. 相似文献
959.
Schroeder C Vernino S Birkenfeld AL Tank J Heusser K Lipp A Benter T Lindschau C Kettritz R Luft FC Jordan J 《The New England journal of medicine》2005,353(15):1585-1590
We report on a patient with long-standing severe autonomic failure that affected his sympathetic and parasympathetic nervous systems. Antibodies against the ganglionic acetylcholine receptors were detected in the serum. Removal of the antibodies by means of plasma exchange resulted in a dramatic clinical improvement. 相似文献
960.
von Känel R Kudielka BM Preckel D Hanebuth D Herrmann-Lingen C Frey K Fischer JE 《Physiology & behavior》2005,86(1-2):61-68
Exaggerated procoagulant responses to acute mental stress may contribute to coronary thrombosis, and continuing low-grade systemic coagulation activation may link negative affect with the development of coronary artery disease. We investigated whether negative and positive affect and perceived social support would moderate stress procoagulant reactivity. Psychological functioning, exhaustion, negative affectivity, depression, anxiety, worrying, vigor, and social support were assessed in 27 apparently healthy men (mean age 47 +/- 8 years) who underwent the 13-min Trier Social Stress Test combining preparation, speech, and mental arithmetic. Plasma levels of von Willebrand factor antigen (VWF:Ag), fibrinogen, factor VII clotting activity (FVII:C), FVIII:C, FXII:C, and D-dimer were measured immediately before and after stress. Acute stress elicited significant increases in hemodynamic, cortisol, and coagulant activity (p values < 0.05). VWF:Ag reactivity showed inverse relationships with exhaustion (r = -0.63, p < 0.001), negative affectivity (r = -0.53, p = 0.005), and worrying (r = -0.53, p = 0.005). Exhaustion and negative affectivity emerged as independent predictors of VWF:Ag reactivity explaining 54% of its variance. Fibrinogen reactivity showed inverse relationships with negative affectivity (r = -0.59, p = 0.002) and anxiety (r = -0.54, p = 0.005); negative affectivity emerged as an independent predictor of fibrinogen reactivity explaining 35% of its variance. Psychological functioning and FVII:C reactivity were also correlated (r = -0.52, p = 0.006). Whereas FVIII:C reactivity correlated positively with vigorous mood (r = 0.48, p = 0.012), positive associations between social support and procoagulant reactivity did not reach significance. Negative affect was associated with attenuated procoagulant reactivity to stress and the opposite was observed for positive affect. Negative affect is not likely to enhance the acute procoagulant stress response in healthy men. 相似文献