全文获取类型
收费全文 | 432272篇 |
免费 | 42146篇 |
国内免费 | 22867篇 |
专业分类
耳鼻咽喉 | 4268篇 |
儿科学 | 7535篇 |
妇产科学 | 2932篇 |
基础医学 | 28525篇 |
口腔科学 | 7477篇 |
临床医学 | 50860篇 |
内科学 | 40032篇 |
皮肤病学 | 5470篇 |
神经病学 | 10064篇 |
特种医学 | 16696篇 |
外国民族医学 | 16篇 |
外科学 | 37739篇 |
综合类 | 114526篇 |
现状与发展 | 93篇 |
一般理论 | 2篇 |
预防医学 | 49971篇 |
眼科学 | 5415篇 |
药学 | 52535篇 |
662篇 | |
中国医学 | 42716篇 |
肿瘤学 | 19751篇 |
出版年
2024年 | 2158篇 |
2023年 | 5498篇 |
2022年 | 13495篇 |
2021年 | 17283篇 |
2020年 | 15137篇 |
2019年 | 8255篇 |
2018年 | 8990篇 |
2017年 | 12013篇 |
2016年 | 9080篇 |
2015年 | 16624篇 |
2014年 | 21307篇 |
2013年 | 27243篇 |
2012年 | 39223篇 |
2011年 | 41793篇 |
2010年 | 37271篇 |
2009年 | 32567篇 |
2008年 | 33897篇 |
2007年 | 32715篇 |
2006年 | 28814篇 |
2005年 | 22838篇 |
2004年 | 16392篇 |
2003年 | 13399篇 |
2002年 | 10429篇 |
2001年 | 9497篇 |
2000年 | 7373篇 |
1999年 | 3224篇 |
1998年 | 845篇 |
1997年 | 696篇 |
1996年 | 641篇 |
1995年 | 531篇 |
1994年 | 527篇 |
1993年 | 353篇 |
1992年 | 666篇 |
1991年 | 621篇 |
1990年 | 569篇 |
1989年 | 504篇 |
1988年 | 515篇 |
1987年 | 480篇 |
1986年 | 472篇 |
1985年 | 428篇 |
1984年 | 300篇 |
1983年 | 234篇 |
1982年 | 170篇 |
1981年 | 111篇 |
1979年 | 221篇 |
1978年 | 113篇 |
1977年 | 127篇 |
1976年 | 118篇 |
1974年 | 131篇 |
1972年 | 128篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
双歧杆菌对早产儿食道pH值的影响及临床意义 总被引:2,自引:0,他引:2
目的为探讨双歧杆菌对早产儿食道pH值的影响,及其对早产儿易发生的消化道疾病的防治意义。方法我们采用便携式24hpH值自动记录仪,对61例早产儿进行了食道pH值的动态监测。结果口服双歧杆菌活菌制剂组的30例早产儿,食道pH值明显高于未服药的对照组,t=2.4093,P<0.05。总pH值<4的时间占总观察时间的百分比显著小于对照组。并且治疗组发生消化道疾患的人数也较对照组少。结论早产儿口服双歧杆菌活菌制剂可以减少胃食道反流等消化道疾病的发生。 相似文献
992.
S Aractingi E Gluckman M C Dauge-Geffroy C Le Gou A Flahaut L Dubertret E Carosella 《Journal of clinical pathology》1997,50(4):305-309
AIMS: To measure Langerhans' cells in skin of patients treated by bone marrow transplantation who developed chronic graft versus host disease (GvHD); to determine whether the reduction in Langerhans' cells resulted directly from the GvHD or from other factors, such as the immunosuppressive regimens used in bone marrow transplant patients. PATIENTS AND METHODS: Lesional and nonlesional skin specimens from nine patients with lichen planus-like lesions and three patients with sclerodermoid lesions were studied. Control skin specimens were taken from three patients undergoing breast reduction surgery. The number of Langerhans' cells/mm2 and the area of Langerhans' cells as a percentage of total epidermis were measured by counting cells labelled with antihuman CD1a. RESULTS: A significant reduction in Langerhans' cell area and number were found in specimens with lesions (area 3.5%; number 507/mm2) compared with specimens without lesions (8.42%; 2375/mm2). In contrast, Langerhans' cell area and number in skin without lesions were similar to controls (10.26%; 2968/mm2). CONCLUSIONS: Langerhans' cells were significantly reduced in skin with lesions of chronic GvHD but not in skin without lesions from the same patient, suggesting that the reduction is a direct consequence of GvHD and not linked to immunosuppressive drugs or late effects of conditioning regimens. In long term bone marrow transplant recipients, Langerhans' cells are derived mainly from the donor cells; therefore, this result suggests the occurrence of autoreactive phenomenon in chronic GvHD. 相似文献
993.
Sodium gradient-energized concentrative transport of adenosine in renal brush border vesicles 总被引:4,自引:0,他引:4
The uptake of adenosine in brush border vesicles of the proximal tubule of the rat kidney has been studied with a filtration technique. The initial rate of uptake was almost 6 times greater in the presence of NaCl than in the presence of KCl. The stimulatory effect of Na+ was strictly dependent on a gradient of Na+ (out>in). The time course of uptake showed an overshoot with a maximum at 20 s with a gradient of NaCl, but not with KCl. Inosine and 5-AMP were produced from adenosine within the vesicles. In the presence of an inhibitor or adenosine deaminase adenosine was not significantly metabolized during the first 20 s of uptake. Thus, kinetic parameters of transport could be studied in the absence of interferences with metabolism. AK
m of 1.1 M and aV
max of 232 pmol · min–1 · mg protein–1 were calculated for the Na+ gradient-dependent transport. The dependency on a Na+ gradient, the capacity for uphill transport and the high affinity for adenosine situate this transport system apart from the mechanisms of transport of nucleosides described so far. It may be relevant in regard to the role of adenosine in the regulation of glomerular filtration.Abbreviations used EHNA
erythro-9-(2-hydroxy-3-nonyl)adenine
- FCCP
carbonylcyanide p-trifluoromethoxy-phenylhydrazone
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- Tris
tris (hydroxymethyl)-aminomethane 相似文献
994.
小鼠甲胎蛋白与结核杆菌热休克蛋白70基因融合载体的构建及体外表达 总被引:1,自引:0,他引:1
目的 构建小鼠甲胎蛋白(α-Fetoprotein,AFP)与结核杆菌热休克蛋白70(Mycobacterium tuberculosis heat shock protein 70,Mt.HSP70)基因融合载体.并研究其在真核细胞中的表达情况。方法 以pcDNA3.1为基本单位构建AFP及HSP70的融合表达载体,融合基因以G-S-G-G-S连接子连接;用脂质体将系列载体导入COS-7细胞.48h后以免疫化学方法检测其表达。结果 构建的AFP和HSP70的单独及融合表达载体导入COS-7细胞48h后经RT-PCR检测可扩增出相应片段,细胞免疫化学染色为阳性。结论 AFP和HSP70的单独及融合表达载体构建成功,并能在真核细胞中表达。 相似文献
995.
996.
997.
Intending to clarify the true Incidence of Invasive lobular carcinoma of the breast In Japanese women as well as the frequency of unilateral multlcentriclty, 362 cases of clinically defined monocentrlc breast cancer without pre-operative biopsy (previously fine needle aspiration or needle biopsy were routinely carried out for every case) were examined by whole mammary gland serial sectioning. On the basis of pathology and the World Health Organization classification of breast tumors, each case was assigned to one of two main histologlc types: Invasive lobular carcinoma (ILC) or Invasive ductal carcinoma (IDC). Invasive lobular carcinoma was further separated into classic and variant types by employing previously published criteria. Twenty-one cases of ILC (5.8%) were diagnosed, which Is more than In most previous Japanese studies. Unilateral multicentric breast carcinoma was detected In 9.5% of ILC and 16.1% of IDC (the difference was found not significant). Microscopically, ILC tumors were found to be, on average, larger than IDC. Patients with classic type ILC tended to be younger than those with variant type or IDC. Estrogen receptor expression was found more frequently In variant type ILC than in classic type. These results suggest that the incidence of invasive lobular carcinoma of the breast In Japanese women is low and that unilateral multicentricity Is not significantly higher in ILC than in IDC. 相似文献
998.
API2-MALT1融合基因变异体在粘膜相关淋巴组织结外边缘区B细胞淋巴瘤中的分布及凋亡的关系 总被引:2,自引:0,他引:2
目的探讨API2-MALT1融合基因变异体在粘膜相关淋巴组织结外边缘区B细胞淋巴瘤(extranodal marginal zone B—cell lymphoma of mucosa—associated lymphoid tissue,MALT)中的分布特点及其转录与肿瘤凋亡的关系。方法将逆转录-聚合酶链反应和巢式聚合酶链式反应结合,检测62例不同部位MALT淋巴瘤中API2-MALT1融合基因的多种变异体;通过TdT介导脱氧核苷酸缺口末端标记技术进行肿瘤细胞的原位凋亡检测;通过逆转录-聚合酶链反应和免疫组化染色检测API2的mRNA和蛋白水平。结果62例MALT淋巴瘤中28例检出API2-MALT1融合基因(45.16%),为变异体A1446-M1123或A1446-M814,但未检出A1446-M541和A1446-M1150。A1446-M1123(18/28)的检出明显多于A1446-M814(10/28)。融和基因转录在甲状腺MALT淋巴瘤中检出最低,在其它部位的分布无差异。在API2-MALT1^ 组(API2-MALT1mRNA表达阳性组)肿瘤凋亡水平明显高于API2-MALT1^-组(API2-MALT1mRNA表达阴性组),API2的mRNA和蛋白水平低于阴性组。A1446-M1123^ 与A1446-M814^ 病例之间凋亡和API2的变化无差异。结论MALT淋巴瘤中t(11;18)(q21;q21)的发生有部位差异,A1446-M1123可能是中国人MALT淋巴瘤中API2-MALT1融合基因变异体的主要类型。API2-MALT1融合基因转录与MALT淋巴瘤的凋亡水平和API2的变化有关。 相似文献
999.
Swiedler SJ Beck M Bajbouj M Giugliani R Schwartz I Harmatz P Wraith JE Roberts J Ketteridge D Hopwood JJ Guffon N Sá Miranda MC Teles EL Berger KI Piscia-Nichols C 《American journal of medical genetics. Part A》2005,(2):144-150
A cross-sectional survey in individuals affected with the lysosomal storage disease Mucopolysaccharidosis VI (MPS VI) was conducted to establish demographics, urinary glycosaminoglycan (GAG) levels, and clinical progression of the disease. The survey evaluated 121 bona fide MPS VI-affected individuals over the age of 4 years from 15 countries across the Americas, Europe, and Australasia representing greater than 10% of the estimated world prevalence of the disease. A medical history, complete physical exam, urinary GAG determination, and assessment of several clinical measures related to physical endurance, pulmonary function, joint range of motion, strength, and quality of life were completed for each participant. Although a wide variation in clinical presentation was observed, several general findings were obtained reflecting progression of the disease. Impaired physical endurance, as measured by the distance achieved in a 6-min walk, could be demonstrated across all age groups of MPS VI-affected individuals. High urinary GAG values (>200 mug/mg creatinine) were associated with an accelerated clinical course comprised of age-adjusted short stature and low body weight, impaired endurance, compromised pulmonary function, and reduced joint range of motion. An unexpected result was the predominance of urinary GAG values <100 mug/mg creatinine for those participants over the age of 20 years. Pending the collection of longitudinal data, these results suggest that urinary GAG levels predict clinical morbidity, and longer-term survival is associated with urinary GAG levels below a threshold of 100 mug/mg creatinine. 相似文献
1000.
目的:分析肿瘤光动力治疗中的组织氧含量的变化规律,研究影响肿瘤光动力治疗效果的与氧相关的因素,探讨改进光动力治疗的途径。方法:建立肿瘤光动力治疗中氧含量的动态模型,并采用Crank—Nicolson离散方法解析该模型,在时间域和空间域上,分析光动力过程中肿瘤氧含量的动态变化过程,研究光照的光功率密度、肿瘤初始氧含量等因素对光动力疗效的影响,并比较间断光照和连续光照两种方式的不同疗效。结果:肿瘤氧含量随着治疗时间和离血管的距离呈衰减趋势,光动力反应只发生在血管附近的有限区域,且区域大小与初始氧含量密切相关.在较高的初始氧含量下,更大区域的氧含量因为处于阈值Cth以上,所以能发生光动力反应。当采用较低的光功率密度光照治疗时,肿瘤氧含量衰减比高功率密度下慢;当采用间断光照进行光动力治疗时,在治疗黑暗期肿瘤氧含量能得到回升.有利于光照期的治疗。结论:初始氧含量较高的情况下治疗效果更好;在较低的光功率密度下,光动力反应较难进行,但是有利于保护肿瘤供氧源的工作。在较低的初始氧含量下,间断光照方式的疗效要比连续光照要好。 相似文献