全文获取类型
收费全文 | 21369篇 |
免费 | 1720篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 314篇 |
儿科学 | 595篇 |
妇产科学 | 463篇 |
基础医学 | 3004篇 |
口腔科学 | 445篇 |
临床医学 | 1990篇 |
内科学 | 5018篇 |
皮肤病学 | 239篇 |
神经病学 | 2008篇 |
特种医学 | 647篇 |
外科学 | 3399篇 |
综合类 | 302篇 |
一般理论 | 16篇 |
预防医学 | 1623篇 |
眼科学 | 582篇 |
药学 | 1156篇 |
中国医学 | 38篇 |
肿瘤学 | 1326篇 |
出版年
2023年 | 183篇 |
2022年 | 387篇 |
2021年 | 777篇 |
2020年 | 405篇 |
2019年 | 612篇 |
2018年 | 739篇 |
2017年 | 483篇 |
2016年 | 495篇 |
2015年 | 607篇 |
2014年 | 787篇 |
2013年 | 1037篇 |
2012年 | 1503篇 |
2011年 | 1525篇 |
2010年 | 830篇 |
2009年 | 708篇 |
2008年 | 1251篇 |
2007年 | 1235篇 |
2006年 | 1222篇 |
2005年 | 1154篇 |
2004年 | 1064篇 |
2003年 | 933篇 |
2002年 | 922篇 |
2001年 | 151篇 |
2000年 | 137篇 |
1999年 | 165篇 |
1998年 | 180篇 |
1997年 | 165篇 |
1996年 | 137篇 |
1995年 | 126篇 |
1994年 | 117篇 |
1993年 | 113篇 |
1992年 | 108篇 |
1991年 | 102篇 |
1990年 | 111篇 |
1989年 | 90篇 |
1988年 | 106篇 |
1987年 | 113篇 |
1986年 | 76篇 |
1985年 | 106篇 |
1984年 | 106篇 |
1983年 | 102篇 |
1982年 | 135篇 |
1981年 | 125篇 |
1980年 | 164篇 |
1979年 | 77篇 |
1978年 | 87篇 |
1977年 | 79篇 |
1976年 | 84篇 |
1975年 | 63篇 |
1974年 | 71篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Mohamed Guled Samuel Myllykangas Henry F Frierson Stacey E Mills Sakari Knuutila Edward B Stelow 《Modern pathology》2008,21(6):770-778
Olfactory neuroblastoma is an unusual neuroectodermal malignancy, which is thought to arise at the olfactory membrane of the sinonasal tract. Due to its rarity, little is understood regarding its molecular and cytogenetic abnormalities. The aim of the current study is to identify specific DNA copy number changes in olfactory neuroblastoma. Thirteen dissected tissue samples were analyzed using array comparative genomic hybridization. Our results show that gene copy number profiles of olfactory neuroblastoma samples are complex. The most frequent changes included gains at 7q11.22-q21.11, 9p13.3, 13q, 20p/q, and Xp/q, and losses at 2q31.1, 2q33.3, 2q37.1, 6q16.3, 6q21.33, 6q22.1, 22q11.23, 22q12.1, and Xp/q. Gains were more frequent than losses, and high-stage tumors showed more alterations than low-stage olfactory neuroblastoma. Frequent changes in high-stage tumors were gains at 13q14.2-q14.3, 13q31.1, and 20q11.21-q11.23, and loss of Xp21.1 (in 66% of cases). Gains at 5q35, 13q, and 20q, and losses at 2q31.1, 2q33.3, and 6q16-q22, were present in 50% of cases. The identified regions of gene copy number change have been implicated in a variety of tumors, especially carcinomas. In addition, our results indicate that gains in 20q and 13q may be important in the progression of this cancer, and that these regions possibly harbor genes with functional relevance in olfactory neuroblastoma. 相似文献
103.
Matthew J. Bassignani Samuel J. Dwyer III Jonathan M. Ciambotti Juan M Olazagasti Ruth Moran Sean Moynihan Alfred C. Weaver Andrew M. Snyder 《Journal of digital imaging》2004,17(1):18-27
Teleradiology allows contemporaneous interpretation of imaging exams performed at some distance from the interpreting radiologist. The transmitted images are usually static. However, there is benefit to real-time review of full-motion ultrasound (US) exams as they are performed. Telesonography is transmission of full-motion sonographic data to a remote site. We hypothesize that US exams, read after having been compressed utilizing Motion Picture Experts Group version 4 (MPEG-4) compression scheme, transmitted over the Internet as streaming multimedia, decompressed, and displayed, are equivalent in diagnostic accuracy to reading the examinations locally. MPEG-4 uses variable compression on each image frame to achieve a constant output bit rate. With less compression, the bit rate rises, and the only way the encoder can contain bit rate within the set bandwidth is by lowering frame rate or reducing image quality. We review the relevant technologies and industry standard components that will enable low-cost telesonography. 相似文献
104.
Cheng Zhang Peter Gehlbach Celine Gongora Marisol Cano Robert Fariss Stacey Hose Avindra Nath William R Green Morton F Goldberg J Samuel Zigler Debasish Sinha 《Developmental dynamics》2005,234(1):36-47
We demonstrate that expression of beta- and gamma-crystallins is associated with intraocular vessels during normal vascular development of the eye and also in the Nuc1 rat, a mutant in which the hyaloid vascular system fails to regress normally. Real-Time RT PCR, Western blot and metabolic labeling studies indicate an increased expression of beta- and gamma-crystallins in Nuc1 retina. The increased expression of crystallins was localized to the astrocytes surrounding the intraocular vessels. A similar pattern of crystallin expression was also observed in the retinal vessels during normal development. Cultured human astrocytes exposed to 3-nitropropionic acid, an established model of neuronal hypoxia, increased VEGF expression, as expected, but also increased expression of crystallins. Our data suggest that crystallins may function together with VEGF during vascular remodeling. Interestingly, in human PFV (persistent fetal vasculature) disease, where the hyaloid vasculature abnormally persists after birth, we show that astrocytes express both VEGF and crystallins. 相似文献
105.
Kermit Zhang Eleina Cox Samuel Strom Zhuo Luan Xu Alexis Disilvestro Kelly Usrey 《American journal of medical genetics. Part A》2020,182(9):2124-2128
Baraitser‐Winter cerebrofrontofacial syndrome (BWCFF) is a rare autosomal dominant developmental disorder associated with missense mutations in the genes ACTB or ACTG1. The classic presentation of BWCFF is discerned by the combination of unique craniofacial characteristics including ocular coloboma, intellectual disability, and hypertelorism. Congenital contractures and organ malformations are often present, including structural defects in the brain, heart, renal, and musculoskeletal system. However, there is limited documentation regarding its prenatal presentation that may encourage healthcare providers to be aware of this disorder when presented throughout pregnancy. Herein we describe a case of a pregnancy with large cystic hygroma and omphalocele. Whole exome sequencing (WES) was performed and a de novo, heterozygous, likely pathogenic mutation in ACTB was detected, c.1004G>A (p.Arg335His), conferring a diagnosis of BWCFF. 相似文献
106.
A case of amphotericin B lipid complex induced fatal fat embolism is described. A 41-year-old Caucasian man with AIDS was undergoing treatment for cryptococcal meningitis with amphotericin B. His course was complicated by renal failure necessitating a change in therapy to amphotericin B lipid complex (Abelcet). At approximately 48 h, the patient developed tachycardia, tachypnea, respiratory failure, decline in hematocrit, thrombocytopenia, and alteration in mental status. Autopsy findings included fat emboli involving heart, lungs, kidney, and brain. To our knowledge, this is the first case report of a fatal fat embolism caused by intravenous liposome drug delivery. 相似文献
107.
108.
Fengshuo Lan Defu Zeng Masanori Higuchi John P Higgins Samuel Strober 《Biology of blood and marrow transplantation》2003,9(6):355-363
Our previous studies in mice showed that the nonmyeloablative conditioning regimen of fractionated irradiation of the lymphoid tissues (total lymphoid irradiation; TLI) and depletive anti-T-cell antibodies (anti-thymocyte serum) markedly increased the percentage of regulatory DX5+ and natural killer 1.1+ T cells in the mouse spleen, and prevented acute lethal graft-versus-host disease (GVHD) in BALB/c mice (H-2(d)) following the transplantation of bone marrow (BM) and peripheral blood mononuclear cells (PBMC) from C57BL/6 (H-2(b)) donors. The object of the current study was to determine whether the TLI and anti-thymocyte serum regimen protected natural killer T-cell deficient CD1(-/-) BALB/c mice against GVHD after BM and PBMC transplantation from C57BL/6 donors, and whether a similar conditioning regimen of TLI and anti-thymocyte globulin (ATG) can prevent GVHD in Lewis rat (RT1(l)) hosts after BM and PBMC transplantation from ACI rat (RT1(a)) donors. The experimental results in mice showed that, although wild-type BALB/c hosts are protected in association with a marked increase in CD1- reactive T cells expressing the invariant TCR identified with a CD1 tetramer reagent; CD1(-/-) BALB/c hosts are not. Studies of chimeric donor cells in mice protected from GVHD showed donor T-cell polarization to a Th2 cytokine pattern. Results in rats showed that approximately 1000 fold more donor PBMC cells were required to induce a similar incidence of lethal GVHD in TLI and ATG conditioned hosts as compared with hosts conditioned with single-dose total-body irradiation or total-body irradiation and ATG. Surviving TLI and ATG conditioned rat hosts were complete chimeras. In conclusion, the TLI and ATG/anti-thymocyte serum conditioning regimen protects against GVHD in rats and mice, and regulatory natural killer T cells are required for protection. 相似文献
109.
Recombinant tumor necrosis factor alpha does not inhibit the growth of African trypanosomes in axenic cultures 下载免费PDF全文
Kitani H Black SJ Nakamura Y Naessens J Murphy NB Yokomizo Y Gibson J Iraqi F 《Infection and immunity》2002,70(4):2210-2214
Mice whose tumor necrosis factor alpha (TNF-alpha) genes were disrupted developed higher levels of parasitemia than wild-type mice following infection with Trypanosoma congolense IL1180 or T. brucei brucei GUTat3.1, confirming the results of earlier studies. To determine whether TNF-alpha directly affects the growth of these and other bloodstream forms of African trypanosomes, we studied the effects of recombinant mouse, human, and bovine TNF-alpha on the growth of two isolates of T. congolense, IL1180 and IL3338, and two isolates of T. brucei brucei, GUTat3.1 and ILTat1.1, under axenic culture conditions. The preparations of recombinant TNF-alpha used were biologically active as determined by their capacity to kill L929 cells. Of five recombinant TNF-alpha lots tested, one lot of mouse TNF-alpha inhibited the growth of both isolates of T. brucei brucei and one lot of bovine TNF-alpha inhibited the growth of T. brucei brucei ILTat1.1 but only at very high concentrations and without causing detectable killing of the parasites. The other lots of mouse recombinant TNF-alpha, as well as human TNF-alpha, did not affect the growth of any of the test trypanosomes even at maximal concentrations that could be attained in the culture systems (3,000 to 15,000 U of TNF-alpha/ml of medium). These results suggest that exogenously added recombinant TNF-alpha generally does not inhibit the growth of African trypanosomes under the culture conditions we used. The impact of TNF-alpha on trypanosome parasitemia may be indirect, at least with respect to the four strains of trypanosomes reported here. 相似文献
110.