全文获取类型
收费全文 | 10204篇 |
免费 | 645篇 |
国内免费 | 41篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 230篇 |
妇产科学 | 174篇 |
基础医学 | 1336篇 |
口腔科学 | 289篇 |
临床医学 | 830篇 |
内科学 | 2276篇 |
皮肤病学 | 186篇 |
神经病学 | 815篇 |
特种医学 | 977篇 |
外科学 | 1702篇 |
综合类 | 69篇 |
一般理论 | 1篇 |
预防医学 | 587篇 |
眼科学 | 145篇 |
药学 | 515篇 |
1篇 | |
中国医学 | 8篇 |
肿瘤学 | 680篇 |
出版年
2023年 | 106篇 |
2022年 | 230篇 |
2021年 | 367篇 |
2020年 | 230篇 |
2019年 | 282篇 |
2018年 | 346篇 |
2017年 | 205篇 |
2016年 | 288篇 |
2015年 | 333篇 |
2014年 | 395篇 |
2013年 | 423篇 |
2012年 | 653篇 |
2011年 | 618篇 |
2010年 | 427篇 |
2009年 | 347篇 |
2008年 | 516篇 |
2007年 | 533篇 |
2006年 | 533篇 |
2005年 | 528篇 |
2004年 | 421篇 |
2003年 | 364篇 |
2002年 | 363篇 |
2001年 | 126篇 |
2000年 | 121篇 |
1999年 | 117篇 |
1998年 | 95篇 |
1997年 | 97篇 |
1996年 | 70篇 |
1995年 | 53篇 |
1994年 | 62篇 |
1993年 | 49篇 |
1992年 | 57篇 |
1991年 | 66篇 |
1990年 | 79篇 |
1989年 | 55篇 |
1988年 | 47篇 |
1987年 | 60篇 |
1986年 | 41篇 |
1985年 | 49篇 |
1984年 | 42篇 |
1983年 | 28篇 |
1982年 | 26篇 |
1981年 | 39篇 |
1979年 | 30篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1975年 | 26篇 |
1974年 | 31篇 |
1932年 | 36篇 |
1923年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Timo D Müller Anke Hinney André Scherag Thuy T Nguyen Felix Schreiner Helmut Schäfer Johannes Hebebrand Christian L Roth Thomas Reinehr 《BMC medical genetics》2008,9(1):85
Background
We have previously identified strong association of six single nucleotide polymorphisms (SNPs) in FTO (fat mass and obesity associated gene) to early onset extreme obesity within the first genome wide association study (GWA) for this phenotype. The aim of this study was to investigate whether the obesity risk allele of one of these SNPs (rs9939609) is associated with weight loss in a lifestyle intervention program. Additionally, we tested for association of rs9939609 alleles with fasting blood parameters indicative of glucose and lipid metabolism. 相似文献42.
43.
dos Santos CN Rocha CF Cordeiro M Fragoso SP Rey F Deubel V Desprès P 《Virus research》2002,90(1-2):197-205
We have investigated the genetic diversity of dengue type-1 (DEN-1) virus in Brazil. The full nucleotide sequences of three DEN-1 virus isolated from DEN fever (DF) and DEN hemorrhagic fever patients in northeastern Brazil in 1997 (BR/97) and one from a DF patient in the south of Brazil in 2001 (BR/01) were compared to that of the reference strain BR/90 obtained in the city of Rio de Janeiro in 1990. Sequence analysis showed that the structural proteins were remarkably conserved between all isolates. A total of 27 amino acid changes occurred throughout the non-structural proteins. Among them, nine amino acid substitutions were specific of BR/97 and BR/01 isolates, indicating that in situ evolution of these strains had occurred. Within the BR/97 and BR/01 samples, some amino acid substitutions have been previously identified in DEN-1 virus strains sequenced so far, suggesting that recombination events might have occurred. 相似文献
44.
Podlowski S Wenzel K Luther HP Müller J Bramlage P Baumann G Felix SB Speer A Hetzer R Köpke K Hoehe MR Wallukat G 《Journal of molecular medicine (Berlin, Germany)》2000,78(2):87-93
A substantial body of evidence suggests involvement of the human beta1-adrenoceptor (beta1-AR) gene in the pathophysiology of dilated cardiomyopathy (DCM), a severe heart disease of significant public health impact. Beta1-AR-mediated signal transduction is dramatically altered due to downregulation, resulting in an impairment of myocardial response. The important role of genetic factors in idiopathic dilated cardiomyopathy (IDCM) recently recognized, we analyzed this prime candidate gene for genetic variation in carefully selected patients and controls. In this preliminary study, 18 single nucleotide polymorphisms were observed, 17 of which were located in the N-terminal and C-terminal region of the coding exon, resulting in 7 amino acid exchanges: Ser-49-Gly, Ala-59-Ser, Gly-389-Arg, Arg-399-Cys, His-402-Arg, Thr-404-Ala, and Pro-418-Ala. These mutations resulted in 11 different beta1-AR genotypes. Importantly, the genotypes carrying the Ser-49-Gly mutation in the N-terminus of the molecule in a heterozygous or homozygous form were observed significantly more frequently in the group of IDCM patients. The present results may provide a clue on the molecular mechanisms involved in IDCM, and add moreover interesting information on nature, distribution, and evolutionary aspects of sequence variation in human adrenergic receptor genes. 相似文献
45.
Wayne C. Waltzer Radoslav J. Bachvaroff Angelo Arnold David Anaise Felix T. Rapaport 《Journal of clinical immunology》1985,5(2):78-83
The role and activity of natural killer (NK) cells following renal transplantation remain unknown. To monitor NK activity, a51Cr release of K-562 targets in prednisone-and azathioprine-treated patients receiving renal allografts was utilized. In 18 patients in whom NK activity was measured prior to and after transplantation, a significant diminution in NK activity within 3 weeks following transplantation was demonstrated compared to pretransplant values (34.71 vs 12.20%, respectively;P<0.001). In 11 subjects who had NK activity assayed at various intervals after transplantation but not prior to allografting, mean NK values were markedly lower (mean, 14.2%) than those of normal volunteers or patients maintained on hemodialysis (P<0.001). The latter two control groups demonstrated no difference (P = NS) in mean NK activity (39.46 vs 35.82%, respectively). In 5 of the 29 patients evaluated with good long-term graft function (mean, 2.7 years), restitution of normal NK activity was demonstrated. In two patients with bacterial infections, NK activity increased from 39.29 to 51.7% and from 13.54 to 20.00%. After infection, these values were 35.3% in the former and 3.39% in the latter. Viral infection did not appear to affect NK activity significantly. NK activity was increased in only one of seven patients with documented rejection episodes. In three of such patients, NK activity declined significantly following pulse methylprednisolone therapy. These results indicate that (1) NK-cell activity significantly decreases immediately after transplantation, probably as a result of immunosuppressive therapy; (2) NK activity does not appear to be stimulated by the alloreactive rejection process; (3) NK activity may be augmented in the course of bacterial but not viral infections; and (4) long-term allograft survival may be associated with a restoration of NK-cell levels in certain recipients. 相似文献
46.
Summary: Mucosal surfaces represent the entry route of a multitude of viral pathogens. For many of these viruses, such as the herpes simplex viruses and human immunodeficiency virus, no effective vaccine exists. Hence, it is important that prospective vaccines engender maximal immunity at these susceptible sites. Genetic vaccines encoding adjuvant molecules represent one approach to optimize mucosal as well as systemic immunity. Promising candidates include various inflammatory cytokines and chemokines that might be used to enhance the primary response to a level sufficient for protection. Encouraging studies involving cytokines such as granulocyte/macrophage colony‐stimulating factor, interleukin‐2 (IL‐2), IL‐12, IL‐18, and many others are examined. Notable chemokines that may offer hope in such efforts include IL‐8, RANTES, CCL19, CCL21, and a few others. Combinatorial approaches utilizing several cytokines and chemokines will most likely yield the greatest success. In addition, as more is discovered regarding the requirements for memory development of T cells, boosters involving key cytokines such as IL‐15 and IL‐23 may prove beneficial to long‐term maintenance of the memory pool. This review summarizes the progress in the use of genetic vaccines to achieve mucosal immunity and discusses the needed strategies to maximize long‐term prospective immunity at this vulnerable entry site. 相似文献
47.
Storlazzi CT Fioretos T Paulsson K Strömbeck B Lassen C Ahlgren T Juliusson G Mitelman F Rocchi M Johansson B 《Human molecular genetics》2004,13(14):1479-1485
Double minutes (dmin), the cytogenetic hallmark of genomic amplification, are found in approximately 1% of karyotypically abnormal acute myeloid leukemias (AML) and myelodysplastic syndromes (MDS). The MYC gene at 8q24 has been reported to be amplified in the majority of the cases, and generally it has been assumed that MYC is the target gene. However, only a few studies have focused on the extent of the amplicon or on the expression patterns of the amplified genes. We have studied six cases (five AML and one MDS) with MYC-containing dmin. Detailed fluorescence in situ hybridization analyses identified a common 4.3 Mb amplicon, with clustered proximal and distal breakpoints, harboring eight known genes (C8FW, NSE2, POU5FLC20, MYC, PVT1, AK093424, MGC27434 and MLZE). The corresponding region was deleted in one of the chromosome 8 homologues in five of the six cases, suggesting that the dmin originated through extra replication (or loop-formation)--excision--amplification. Northern blot analysis revealed that MYC was not overexpressed. Instead, the C8FW gene, encoding a phosphoprotein regulated by mitogenic pathways, displayed increased expression. These results exclude MYC as the target gene and indicate that overexpression of C8FW may be the functionally important consequence of 8q24 amplicons in AML and MDS. 相似文献
48.
Hideki Endo Takahiro Yonezawa Felix Rakotondraparany Motoki Sasaki Masami Hasegawa 《Annals of anatomy》2006,188(4):383-390
The hindlimb muscles in four species of Tenrecidae (Oryzoryctinae: Talazac long-tailed tenrec and web-footed tenrec, Tenrecinae: lesser hedgehog tenrec, and streaked tenrec), were examined macroscopically. The weight ratios of the muscles to the body in the oryzoryctinid species are larger than those in Tenrecinae, since the Oryzoryctinae species have an obviously smaller body from the evolutionary point of view. It can be primarily pointed out that the adaptation of the body size is different between the two subfamilies, and secondarily, that functional adaptation to locomotion is complete within each subfamily. The weight data and the morphological findings demonstrate that the web-footed tenrec possesses an extraordinary large M. semimembranosus in comparison to the Talazac long-tailed tenrec in their weight ratios. This muscle may act as a strong flexor motor in the knee joint during the aquatic locomotion of the web-footed tenrec. Since the other muscles of the web-footed tenrec are similar to those of the Talazac long-tailed tenrec regards weight ratio data, we think that the web-footed tenrec may have derived from a terrestrial ancestor such as the long-tailed tenrecs. In Tenrecinae the streaked tenrec is equipped with larger Mm. adductores, M. semimembranosus and M. triceps surae than the lesser hedgehog tenrec. This species is adapted to fossorial life derived from non-specialized ancestors within the evolutionary lines of the spiny tenrecs. 相似文献
49.
Felix Eckstein Beat Merz Magdalena Müller-Gerbl Nikolaus Holzknecht Markus Pleier Reinhard Putz 《Anatomical record (Hoboken, N.J. : 2007)》1995,243(3):327-335
Background: A deeper joint socket (concave incongruity) is found at most angles of flexion of the humero-ulnar joint and maintained over a wide range of physiological loading. It is, however, unclear how far this incongruity affects the distribution of load and subchondral mineralization of this joint as compared with a congruous configuration. Methods: Two nonlinear, axisymmetrical finite element models with two cartilage layers were constructed, one congruous and one incongruous, with a joint space of realistic magnitude. The distribution of subchondral mineralization was determined by computed tomography osteoabsorptiometry in the same six specimens that were investigated in the first part of the study, and compared with the biomechanical data obtained there and the predictions of the models. Results: In the congruous case, the center of the socket is highly loaded, whereas the periphery does not experience mechanical stimulation. A central bone density maximum is predicted. With concave incongruity the position of the contact areas shifts from the joint margin towards the center as the load increases, and the peak stresses are considerably lower. A bicentric ventro-dorsal distribution pattern of subchondral mineralization is predicted, and this is actually found in the six specimens. Conclusions: Concave incongruity is shown to determine load transmission and subchondral mineralization of the humero-ulnar joint. It is suggested that this shape leads to a more even distribution of stress, provides intermittent stimulation of the cartilaginous tissue, and has beneficial effects on the metabolism, nutrition, and lubrication of the articular cartilage during cyclic loading. © 1995 Wiley-Liss, Inc. 相似文献
50.
Felix S. B. Baumann G. Hashemi T. Niemczyk M. Ochsenfeld G. Ahmad Z. Shirani S. Blömer H. 《Inflammation research》1991,33(3-4):349-358
Summary
In vivo anaphylaxis is associated with respiratory distress and cardiovascular failure. The present investigation was designed to further characterize respiratory and cardiac anaphylactic events. In guinea pigs, sensitization was produced by subcutaneous application of ovalbumin together with Freund's adjuvant. Fourteen days after sensitization, the effects of an intravenous infusion of ovalbumin were tested in the anesthetized artificially ventilated guinea pigs. The renewed application of the antigen induced an initial increase of left ventricular pressure which was followed by a rapid decrease 5 min after antigenic challenge. Enddiastolic left ventricular pressure increased within 3 min, thus indicating left ventricular pump failure. In the same time range, ECG recordings uniformly showed signs of acute myocardial ischemia. In addition, heart rate steadily decreased. All animals died within 15 min. Simultaneously with cardiac anaphylactic malfunction, severe arterial hypoxia and carbon dioxide retention occurred, revealing respiratory distress.Histamine is known as a potent bronchoconstrictor via histamine H1-receptor stimulation. Administration of H1-recpetor antagonists to improve respiration may therefore provide further information on the contribution of pulmonary malfunction to anaphylactic cardiovascular shock. Therefore, additional experiments were performed with sensitized guinea pigs pretreated with the histamine H1-receptor blocker mepyramine. In these experiments the antigenic challenge induced a dissociation of cardiac and respiratory manifestation of anphylaxis. Despite inhibition of hypoxia and carbon dioxide retention, left ventricular pump failure and occurrence of myocardial ischemia were delayed but not suppressed.It is concluded that histamine is an important mediator of anaphylactic respiratory distress. However, vasoactive anaphylactic mediators other than histamine are primarily involved in anaphylactic cardiac malfunction occurring during the later phase of systemic anaphylaxis.Supported by grant Fe 250/1-1 from the Deutsche Forschungsgemeinschaft (DFG). 相似文献