首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   8802篇
  免费   475篇
  国内免费   58篇
医药卫生   9335篇
  2023年   32篇
  2022年   36篇
  2021年   111篇
  2020年   64篇
  2019年   94篇
  2018年   92篇
  2017年   76篇
  2016年   108篇
  2015年   153篇
  2014年   186篇
  2013年   309篇
  2012年   435篇
  2011年   508篇
  2010年   334篇
  2009年   306篇
  2008年   516篇
  2007年   600篇
  2006年   580篇
  2005年   635篇
  2004年   537篇
  2003年   613篇
  2002年   558篇
  2001年   163篇
  2000年   114篇
  1999年   137篇
  1998年   152篇
  1997年   107篇
  1996年   100篇
  1995年   80篇
  1994年   77篇
  1993年   92篇
  1992年   63篇
  1991年   92篇
  1990年   58篇
  1989年   83篇
  1988年   53篇
  1987年   45篇
  1986年   56篇
  1985年   36篇
  1984年   44篇
  1983年   39篇
  1982年   41篇
  1981年   42篇
  1980年   43篇
  1979年   37篇
  1978年   33篇
  1977年   45篇
  1976年   29篇
  1975年   29篇
  1974年   28篇
排序方式: 共有9335条查询结果,搜索用时 16 毫秒
31.
32.
33.
Some 30.5 million Germans hold a driving license. For the person with a physical handicap, too, active traffic participation is of special importance, in that it constitutes an essential link in his rehabilitation. Road traffic authorities, in view of traffic safety, are held to consider both, the handicapped individual's interest in obtaining a license and society's claim to safety. Numerous studies have established the fact that disabled drivers, in particular those with impairment of the limbs, are neither more accident-prone nor otherwise more conspicious in road traffic than the non-disabled. The view that the driver with a physical disability poses particular risks, has been invalidated by extensive factual data and thorough literature review. Diseases of major relevance for driving ability are touched on, the range of adaptive equipment is exemplified. Physicians in accident surgery primarily have to deal with trauma to the spinal cord and limbs. The majority of these conditions permit good compensation by technical devices, enabling safe driving of a private car. Awareness of legal/administrative aspects of licensing, as well as of the adaptive potential of technical aids are of great importance to both physician and client.  相似文献   
34.
Bacterial cultures were selected from the native flora of liquid manure in order to metabolize liquid manure substances. The mixed culture used in the growth experiments is characterized by low growth rates when maximum degradation of acetate occurs. The biomass concentration reached 2.2 g/l.  相似文献   
35.
36.
37.
Background: Lumbar facet nerve (medial branch) blocks are often used to diagnose facet joint-mediated pain. The authors recently described a new ultrasound-guided methodology. The current study determines its accuracy using computed tomography scan controls.

Methods: Fifty bilateral ultrasound-guided approaches to the lumbar facet nerves were performed in five embalmed cadavers. The target point was the groove at the cephalad margin of the transverse (or costal) process L1-L5 (medial branch T12-L4) adjacent to the superior articular process. Axial transverse computed tomography scans, with and without 1 ml contrast dye, followed to evaluate needle positions and spread of contrast medium.

Results: Forty-five of 50 needle tips were located at the exact target point. The remaining 5 were within 5 mm of the target. In 47 of 50 cases, the applied contrast dye reached the groove where the nerve is located, corresponding to a simulated block success rate of 94% (95% confidence interval, 84-98%). Seven of 50 cases showed paraforaminal spread, 5 of 50 showed epidural spread, and 2 of 50 showed intravascular spread. Despite the aberrant distribution, all of these approaches were successful, as indicated by contrast dye at the target point. Abnormal contrast spread was equally distributed among all lumbar levels. Contrast traces along the needle channels were frequently observed.  相似文献   

38.
Mice rendered deficient for interleukin (IL) 6 by gene targeting were evaluated for their response to T cell–dependent antigens. Antigen-specific immunoglobulin (Ig)M levels were unaffected whereas all IgG isotypes showed varying degrees of alteration. Germinal center reactions occurred but remained physically smaller in comparison to those in the wild-type mice. This concurred with the observations that molecules involved in initial signaling events leading to germinal center formation were not altered (e.g., B7.2, CD40 and tumor necrosis factor R1). T cell priming was not impaired nor was a gross imbalance of T helper cell (Th) 1 versus Th2 cytokines observed. However, B7.1 molecules, absent from wild-type counterparts, were detected on germinal center B cells isolated from the deficient mice suggesting a modification of costimulatory signaling. A second alteration involved impaired de novo synthesis of C3 both in serum and germinal center cells from IL-6–deficient mice. Indeed, C3 provided an essential stimulatory signal for wild-type germinal center cells as both monoclonal antibodies that interrupted C3-CD21 interactions and sheep anti–mouse C3 antibodies caused a significant decrease in antigen-specific antibody production. In addition, germinal center cells isolated from C3–deficient mice produced a similar defect in isotype production. Low density cells with dendritic morphology were the local source of IL-6 and not the germinal center lymphocytes. Adding IL-6 in vitro to IL-6–deficient germinal center cells stimulated cell cycle progression and increased levels of antibody production. These findings reveal that the germinal center produces and uses molecules of the innate immune system, evolutionarily pirating them in order to optimally generate high affinity antibody responses.  相似文献   
39.
CO2 laser surgery of oral premalignant lesions   总被引:1,自引:0,他引:1  
Experiences gained in the CO2 laser treatment of patients with oral dysplastic precancerous lesions are presented. Besides 7 lichens planus, 50 leukoplakias of all grades of dysplasia, and carcinoma in situ and one lentigo maligna were removed superficially with a defocused laser. Within the average follow-up period of 37 months, 22% local recurrences were observed. In comparison with conservative drug therapy, conventional surgical procedures, and cryosurgical therapy, the CO2 laser treatment of multicentric premalignant diseases of the oral mucosa can be recommended as an alternative therapy.  相似文献   
40.
This study aimed to identify interferon-gamma (IFN-gamma) gene variants in cattle for diagnostic purposes. Therefore, the entire bovine IFN-gamma gene (BoIFNG) and 2605 bp of its promoter DNA were sequenced. The BoIFNG DNA sequence conforms to the published part of Bo-IFN-gamma cDNA. Primer extension experiments show the presence of a 5' extension of exon 1 by 42 nucleotides (nt). One SINE element (Bov-A2) is located in the 5'-region, and two SINE elements (Bov-tA, Bov-B) are contained in the 3'-region of BoIFNG. The variants were detected by comparative sequence analysis of PCR amplicons from different bovine species. Four polymorphic mononucleotide repeats are situated in the promoter and in intron 1. Four distinct series of single nucleotide polymorphisms (SNP) were found in functionally important regions of BoIFNG. The region between the two intron 1 microsatellites contains the highest density of SNPs in Bos taurus breeds. One G-T transversion in the coding region of exon 1 causes a Gly(14) to Val(14) exchange in the BoIFNG signal peptide of different bovine species. A G-A transition in exon 2 encodes a Ser(19) to Asn(19) change in the mature protein of the Tibetan yak. Genotyping of randomly sampled Holstein Friesian cows at selected SNPs and of both intron 1 microsatellites revealed two dominant BoIFNG microhaplotypes. The detected SNPs improve the recently reported genotyping system of cattle.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号