全文获取类型
收费全文 | 5935篇 |
免费 | 478篇 |
国内免费 | 145篇 |
专业分类
耳鼻咽喉 | 61篇 |
儿科学 | 110篇 |
妇产科学 | 121篇 |
基础医学 | 699篇 |
口腔科学 | 154篇 |
临床医学 | 630篇 |
内科学 | 1345篇 |
皮肤病学 | 59篇 |
神经病学 | 338篇 |
特种医学 | 178篇 |
外科学 | 836篇 |
综合类 | 351篇 |
一般理论 | 7篇 |
预防医学 | 376篇 |
眼科学 | 110篇 |
药学 | 483篇 |
1篇 | |
中国医学 | 147篇 |
肿瘤学 | 552篇 |
出版年
2023年 | 40篇 |
2022年 | 79篇 |
2021年 | 153篇 |
2020年 | 95篇 |
2019年 | 137篇 |
2018年 | 149篇 |
2017年 | 116篇 |
2016年 | 158篇 |
2015年 | 196篇 |
2014年 | 246篇 |
2013年 | 284篇 |
2012年 | 404篇 |
2011年 | 439篇 |
2010年 | 297篇 |
2009年 | 260篇 |
2008年 | 351篇 |
2007年 | 396篇 |
2006年 | 310篇 |
2005年 | 344篇 |
2004年 | 310篇 |
2003年 | 280篇 |
2002年 | 243篇 |
2001年 | 197篇 |
2000年 | 165篇 |
1999年 | 121篇 |
1998年 | 66篇 |
1997年 | 60篇 |
1996年 | 50篇 |
1995年 | 33篇 |
1994年 | 37篇 |
1993年 | 27篇 |
1992年 | 51篇 |
1991年 | 64篇 |
1990年 | 52篇 |
1989年 | 46篇 |
1988年 | 29篇 |
1987年 | 17篇 |
1986年 | 32篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 21篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 18篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1974年 | 11篇 |
1973年 | 8篇 |
排序方式: 共有6558条查询结果,搜索用时 15 毫秒
21.
Jong-Kai Hsiao Ming-Fong Tai Hung-Hao Chu Shin-Tai Chen Hung Li Dar-Ming Lai Sung-Tsang Hsieh Jaw-Lin Wang Hon-Man Liu 《Magnetic resonance in medicine》2007,58(4):717-724
The purpose of this work was to evaluate the efficacy of labeling human mesenchymal stem cells (hMSCs) by ionic superparamagnetic iron oxide (SPIO) without a transfection agent and verifying its capability to be detected with clinical 1.5 T magnetic resonance (MR) at the single-cell level. Human hMSCs were incubated for 24 h with an ionic SPIO, Ferucarbotran. The labeling efficiency of hMSCs was determined by iron content measurement spectrophotometrically, and the influence of labeling on cell behavior was ascertained by examination of cell viability using the trypan blue exclusion method, cell proliferation analysis using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, mitochondrial membrane potential (MMP) change, differentiation capacity, and reactive oxygen species (ROS) production measured by dichlorofluorescein diacetate (DCFDA) fluorescent probe. Labeled hMSCs were scanned under 1.5 T MRI with three-dimensional (3D) and two-dimensional (2D) T(2)-weighted gradient echo (GRE) pulse sequences. Human hMSC labeling without transfection agent was efficient. The iron content in hMSCs was 23.4 pg Fe/cell. No significant change was found in viability, proliferation, MMP change, ROS production, or differentiation capacity. About 45.2% of the hMSCs could be detected using 1.5 T MRI at the single cell level with 3D GRE and four repetitions. 相似文献
22.
Federico E Turkheimer Paul Edison Nicola Pavese Federico Roncaroli Alexander N Anderson Alexander Hammers Alexander Gerhard Rainer Hinz Yan F Tai David J Brooks 《Journal of nuclear medicine》2007,48(1):158-167
PET with [(11)C]-(R)-PK11195 is currently the modality of choice for the in vivo imaging of microglial activation in the human brain. In this work we devised a supervised clustering procedure and a new quantification methodology capable of producing binding potential (BP) estimates quantitatively comparable with those derived from plasma input with robust quantitative implementation at the pixel level. METHODS: The new methodology uses predefined kinetic classes to extract a gray matter reference tissue without specific tracer binding and devoid of spurious signals (in particular, blood pool and muscle). Kinetic classes were derived from an historical database of 12 healthy control subjects and from 3 patients with Huntington's disease. BP estimates were obtained using rank-shaping exponential spectral analysis (RS-ESA) (both plasma and reference input) and the simplified reference tissue model (SRTM). Comparison between plasma- derived BPs and those produced with the new reference methodology was performed using 6 additional healthy control subjects. Reliability of the new methodology was performed on 4 test-retest studies of patients with Alzheimer's disease. RESULTS: The new algorithm selected reference voxels in gray matter tissue avoiding regions with specific binding located, in particular, in the venous and arterial circulation. Using the new reference, BP values obtained using a plasma input and a reference input were in excellent agreement and highly correlated (r = 0.811, P < 10(-5)) when calculated with RS-ESA and less so (r = 0.507, P < 0.005) when SRTM was used. In the production of parametric maps, SRTM was used with the new reference extraction, resulting in test-retest variability (10.6%; mean ICC = 0.878) that was superior to that obtained using the previous unsupervised clustering approach (mean ICC = 0.596). CONCLUSION: Reference region modeling combined with supervised reference tissue extraction produces a robust and reproducible quantitative assessment of [(11)C]-(R)-PK11195 studies in the human brain. 相似文献
23.
San-Chi Lin Chung-Chieh Tai Chang-Chuan Chan Jung-Der Wang 《American journal of industrial medicine》1994,26(2):221-228
A chromium electroplating worker, suffering from epistaxis during work, was found to have nasal septum perforation. To determine the etiology and prevalence of nasal septum lesions, we conducted a survey of seven chromium electroplating factories and examined 79 workers. Forty workers from three aluminum electroplating factories were also enrolled as the reference group. Subjects were thoroughly examined by an otolaryngologist and each of them provided a blood and urine sample. A questionnaire interview regarding symptoms of the upper respiratory tract, past medical history, life style, and work history was also conducted. Air chromium concentrations were measured by taking area samples for 4–6 hours. Based on field observation and chromium measurements, we divided chromium electroplating into three different exposure zones: workers directly dealing with electroplating tanks (n = 31), other process workers (n = 29), and office workers and drivers (n = 19). Among the 79 chromium electroplating workers, there were 16 cases of nasal septum perforation, and 42 with either scar formation or ulceration; 10 chromium electroplating workers developed skin ulcers after performing chrome plating. No workers from aluminum electroplating factories had any nasal septum or skin abnormalities. There was a consistent trend between the degree of chromium exposure and the signs and symptoms related to the nose, throat, and skin. Immediate improvement of occupational hygiene is warranted. 相似文献
24.
25.
中西医结合治疗慢性盆腔炎100例疗效观察 总被引:2,自引:1,他引:1
目的:采用中西医结合治疗慢性盆腔炎,减少复发,提高治愈率。方法:对我院门诊患者100例采用胎盘组织液肌注,金钢藤胶囊口服,并用我院自制中药妇炎肠疗液灌肠。结果:临床显效40例,有效56例,无效4例,总有效率96%。结论:中西医结合治疗慢性盆腔炎疗效满意,是目前治疗慢性盆腔炎的最好方法。 相似文献
26.
A relatively nonhygroscopic crystalline form of the glycopeptide, N-acetylmuramyl-L--aminobu-tyryl-D-isoglutamine (I), containing approximately one molecule of water was prepared from amorphous material. The crystalline material, consisting of a mixture of the and anomers, exhibited better physical and chemical stability than the lyophilized amorphous material. The /-anomer ratios of I in both the crystalline and the amorphous state were approximately equal but different from that in solution. 相似文献
27.
Cell extract-derived differentiation of embryonic stem cells 总被引:1,自引:0,他引:1
Various means have been used to encourage the differentiation of embryonic stem cells (ESCs) toward specific lineages, including growth factor administration, genetic modification, and coculture with relevant cells/tissues. Cell extract-based reprogramming has recently been used to derive mature cells from nonrelated phenotypes. In this communication, we tested whether this in vitro reprogramming approach can be used to direct ESC differentiation. Permeabilized murine ESCs exposed to extracts of murine type II pneumocytes showed increased expression of surfactant protein C and its corresponding mRNA, reflecting enhanced differentiation of pneumocytes. Subsequent differentiation to a type I phenotype was demonstrated by expression of aquaporin 5. Pneumocyte formation occurred quicker than with growth factor-induced differentiation. Our findings establish that ESCs can be differentiated in vitro using cellular extracts. This model provides a tool for analysis of the key factors involved in the differentiation of ESCs to type II pneumocytes. 相似文献
28.
孕鼠被动吸烟对子代学习记忆功能及海马神经生长因子含量的影响 总被引:5,自引:0,他引:5
目的 探讨孕鼠被动吸烟对子代学习记忆功能的影响及其机制。方法 采用反映学习记忆功能的水迷宫法测试大鼠神经行为的改变,IRMA法测定大鼠海马神经生长因子的含量变化。结果 孕期被动吸烟使仔鼠学习记忆能力下降,海马神经生长因子含量明显降低。结论 孕期被动吸烟降低仔鼠学习记忆功能与海马神经生长因子代谢的失调有关。 相似文献
29.
Yu Wen-Gong; Yamamoto Noriniko; Takenaka Hiroshi; Mu Jie; Tai Xu-Guang; Zou Jian-Ping; Ogowa Makoto; Tsutsui Tateki; Wijesuriya Rishani; Yoshida Ryotaro; Herrmann Steven; Fujiwara Hiromi; Hamaoka Toshiyuki 《International immunology》1996,8(6):855-865
The present studnt Investigates the molecular by which IFN-produced as a result of in vitroIL-12 addministration exertsits anty-tumor,rIL-12 was administered three or five times intomice bearing CDA1M fibrosarcoma, OV-HM ovarian carcinoma orMCH-1-A1 fibosarcoma. This regimen induced complete regressionof CSA1M and OV-HM tumors but only transient growth inhibitionof MCH-1-A1 tumors. The anty-tumor effects of Il-12 were associatatedwith enhanced induction of IFN-becouse these effects were abrogatedby pretreatment of hosts with anti-IFN- antibody.Exposure inin vitro of the three types of tumor cells to rIFN- resultedin moderate to potent inhibition of tumor cell growth.IFNstimulatedthe expression of mRNAs for an inducible type of NO synthasa(INOS)in CSA1M cells and indoleamine 2,3-dioxygenasa (IDO),an enzyme capable of degrading tryptophan, in OV-HM cells ,but induced only marginal levels of these mRNAs in MCH-I-ALcells. In association withiNOS gene expression, INF--stimulatedCSA1M cells produced a large amount of NO which functioned toinhibit their own growth in vitro. Although OV-HM and MCH-1-A1cells did not produce NO, they also exhibited NO susceptibility.Whereasthe tumor masses from IL-12-treated CSA1M-bearing mice inducedhigher levels of INOS (for CSA1M) or IDO and iNOS (for OV-HM)mRNAs,the MCH-1-A1 tumor mass expressed lower levels of iNOS mRNAalone.Moreover, massive infiltration of CD4+and CD8+ T cellsand Mac-1+ cells was seen only in the CSA1M and OV-HM tumors.Thus, these results indicate that IFN- produced after IL-12treatment induces the expression of various genes with potentialto modulate tumor cells and growth by acting directly on tumorecells or stimulating tumor-infiltrating lymphold cells and thatthe effectiveness of IL12 therapy is assoiated with the operation if these mechanisms. 相似文献
30.
蒙古族、回族和汉族的发旋调查 总被引:2,自引:0,他引:2
对蒙古族、回族和汉族共6098例发旋进行了观察,结果:蒙古族单旋出现率高于回族和汉族,而双旋则低于这两个民族,差异极其显著(P<0.01)。三个民族男性双旋均高于本民族女性(P<0.01)。双旋的组合除文献报道的四种类型外,还有四种组合方式。 相似文献