首页 | 本学科首页   官方微博 | 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   229001篇
  免费   20390篇
  国内免费   4738篇
耳鼻咽喉   3361篇
儿科学   4103篇
妇产科学   3630篇
基础医学   17200篇
口腔科学   7671篇
临床医学   23538篇
内科学   24498篇
皮肤病学   2471篇
神经病学   11943篇
特种医学   6068篇
外国民族医学   17篇
外科学   21663篇
综合类   35984篇
现状与发展   9篇
一般理论   26篇
预防医学   31817篇
眼科学   2099篇
药学   21601篇
  367篇
中国医学   26287篇
肿瘤学   9776篇
  2024年   1039篇
  2023年   4618篇
  2022年   8576篇
  2021年   11274篇
  2020年   11023篇
  2019年   12182篇
  2018年   10934篇
  2017年   9643篇
  2016年   8712篇
  2015年   8058篇
  2014年   15590篇
  2013年   16210篇
  2012年   13912篇
  2011年   14748篇
  2010年   11908篇
  2009年   10374篇
  2008年   9694篇
  2007年   9630篇
  2006年   8200篇
  2005年   6998篇
  2004年   5780篇
  2003年   5088篇
  2002年   4004篇
  2001年   3322篇
  2000年   2882篇
  1999年   2356篇
  1998年   1914篇
  1997年   1731篇
  1996年   1393篇
  1995年   1315篇
  1994年   1204篇
  1993年   1072篇
  1992年   978篇
  1991年   889篇
  1990年   757篇
  1989年   725篇
  1988年   682篇
  1987年   613篇
  1986年   548篇
  1985年   1802篇
  1984年   2064篇
  1983年   1294篇
  1982年   1713篇
  1981年   1183篇
  1980年   1014篇
  1979年   906篇
  1978年   739篇
  1977年   554篇
  1976年   696篇
  1975年   479篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Phenomenology and family history in DSM-III psychotic depression   总被引:1,自引:0,他引:1  
Depressed inpatients with psychotic features were compared to those without them in terms of demographic features, depressive symptoms at intake and family history. These variables were then used to compare patients with mood-congruent psychotic features to those with mood-incongruent psychotic features. Patterns of familial psychopathology were similar for psychotic and non-psychotic patients. In accord with other studies, the families of mood-incongruent patients had slightly more schizophrenia and significantly less depression than did the families of mood-congruent patients. Depressive symptoms, particularly those used to define major depression and melancholia, were more severe in psychotic patients. Moreover, these particular depressive symptoms were more likely to distinguish mood-congruent from mood-incongruent patients than were other depressive symptoms. Thus mood-congruent psychotic features accompanied a more typical depressive syndrome than did mood-incongruent psychotic features.  相似文献   
992.
Autopsies were performed in 40 cases of nonimmune hydrops fetalis during the period from 1975 to 1983. In 25 cases specific anatomic diagnoses, including hematologic disorders, infections, chromosomal abnormalities, congenital anomalies, and tumors, were made. In the majority the diagnosis of hydrops fetalis was made prenatally by ultrasonography. The mean gestational age at delivery was 30 weeks; 23 infants were stillborn, and 17 died during the neonatal period. Body weights were consistently increased; peripheral edema and ascites were present in all cases and pleural effusions in all but two cases. Hepatosplenomegaly, cardiomegaly, and pulmonary hypoplasia were frequent findings. The most consistent microscopic changes involved endocrine organs. Islet cell hyperplasia and Leydig cell hyperplasia were common, and thyroid hyperplasia was found occasionally. The fetal zone of the adrenal cortex was often thick and composed of swollen, vacuolated cells. Enhanced extramedullary erythropoiesis was observed in all cases. Thirty-nine placentas were examined; 34 were edematous (mean weight, 547 g), with villous edema, excess erythroblastemia and normoblastemia, and occasional intravillous hematopoiesis. Nonimmune hydrops fetalis has a range of known causes. Thorough autopsy, including placental examination, is the most useful approach for determining the etiology. In 23 cases the probable or possible cause was established in this manner. Antibody studies should also be performed in all cases to exclude an immunologic etiology. Synthesis of clinical, serologic, and pathologic data offers prospects for rational management and prediction of recurrence.  相似文献   
993.
Monoclonal antibody LICR -LON- M18 identifies the immunodominant oligosaccharide sequence of the I(Ma) blood-group antigen: Gal beta 1----4GlcNAc beta 1----6--. In primary breast cancers this structure is almost totally cryptic, due to "masking" by sialic acid, but can be revealed by digestion with the specific glycosidase neuraminidase. Following desialylation, light microscopic immunohistochemical examination has revealed the epitope identified by LICR -LON- M18 to be heterogeneously distributed throughout the population of breast carcinoma cells. These tumor cells express the antigen as both a cytoplasmic and a surface membrane determinant. In the normal human breast, this structure is expressed exclusively along the luminal plasma membranes of the duct and alveolar littoral epithelial cells. Desialylation of tissue sections of normal resting and lactating breast epithelium with neuraminidase virtually abolishes the heterogeneous intercellular distribution of the I(Ma) determinant. In desialylated nonneoplastic breast tissues, the expression of this antigen is observed within the cytoplasm of some myoepithelial cells, but not in the littoral epithelial cells. The expression of the I(Ma) antigen by neoplastic and normal breast epithelial cells has also been compared with that of the oligosaccharide sequence Gal beta 1----3GalNAc. This structure, recognized by peanut agglutinin, forms the dominant portion of the Thomsen-Friedenreich antigen. With respect to normal and lactating breast epithelial cells, both oligosaccharide structures are sialylated and appear to be similarly misprocessed by breast carcinomas. The masking of surface carbohydrate determinants and the faulty processing of structures usually expressed on the surface of non-neoplastic breast epithelial cells may be important phenomena in the pathobiology of breast carcinomas.  相似文献   
994.
The distributions of retrograde labeled cells in fields 17 and 18 and the fields 17/18 transitional zone were studied in both hemispheres of cats after microiontophoretic administration of horseradish peroxidase into individual cortical columns in fields 17, 18, 19, and 21a. The clustered organization of the internal connections of the cortical fields, the asymmetrical locations of labeled callosal cells relative to the injected columns, and the defined distribution of labeled cells in layers A of the lateral geniculate body suggested that eye-specific neuronal connections support binding of the visual hemifields separately for each eye. Application of marker to columns in fields 19 or 21a demonstrated disparate inputs from fields 17 and 18 and the fields 17/18 transitional zone. It is suggested that these connections may support the extraction of loci and stereoscopic boundaries located in the central sectors of the visual space.Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 89, No. 10, pp. 1281–1290, October, 2003.  相似文献   
995.
Summary To investigate whether intestinal calcium absorption parallels that of sodium following extracellular fluid volume expansion, the effects of saline loading on intestinal transport of calcium. sodium and water were studied in rats by perfusing jejunal loops in situ.After calcium-free saline infusion net calcium absorption was reversed similar to that of sodium and water and net secretion occurred. Concurrently, blood-to-lumen (b-l) calcium flux, measured using45Ca, increased significantly (P<0.001). Following expansion with calcium-containing Ringer a similar reversal of net calcium, sodium and water flux was also observed. Again, the b-l calcium flux increased but to a significantly lesser extent (P<0.05). Plasma ionized calcium remained unchanged after calcium-rich Ringer loading, but decreased significantly (P<0.001) when calcium was omitted from the solution. Plasma immunoreactive parathyroid hormone was unchanged after expansion with the calcium containing solution but increased following calcium-free infusion.It is concluded that after extracellular fluid volume expansion: 1. net jejunal calcium absorption is decreased; 2. the decrease parallels that of sodium and water; 3. b-l calcium transport is enhanced to a greater degree by calcium-free Ringer infusion than by a calcium-rich solution. This difference could be the result of increased parathyroid hormone secretion.  相似文献   
996.
997.
Sixteen per cent of the substantia nigra cell bodies normally labeled from the injection of a fluorescent retrograde tracer in the caudate-putamen complex could still be labeled by the same procedure after multiple intracisternal 6-hydroxydopamine treatments that depleted dopamine levels in the caudate-putamen complex to 1.0% of control. However, the demonstration of glyoxylic-acid-induced catecholamine histofluorescence in tissue from these lesioned rats revealed that many of the surviving retrogradely-labeled substantia nigra cell bodies still contained dopamine. The persistence of some dopamine in the substantia nigra of the lesioned animals was confirmed biochemically. Therefore, retrograde tracing in 6-hydroxydopamine lesioned rats overestimated the extent of the non-dopaminergic nigrostriatal tract.The simultaneous combination of retrograde fluorescent tracing and catecholamine histofluorescence in unlesioned animals revealed that only 5% or less of the substantia nigra cell bodies retrogradelylabeled from the caudate-putamen complex were without catecholamine fluorescence. These apparently non-dopaminergic nigrostriatal cells were located primarily in the ventral tegmental area, substantia nigra pars reticulata and extreme medial edge of the substantia nigra pars compacta.  相似文献   
998.
Dai L  Lü XH  Li ZH  Li R  Liu H  Liu YL  Hui YZ 《中华病理学杂志》2004,33(2):140-142
目的 探讨肾上皮性肿瘤的诊断及鉴别诊断。方法 对91例具有较完整病理资料的肾上皮性肿瘤进行了常规组织学观察,Mowy胶状铁染色及CD10、细胞角蛋白(CK)7、波形蛋白免疫组织化学染色。结果 91例肾上皮性肿瘤中肾透明细胞癌78例,占86%;肾乳头状癌8例,占9%;肾嫌色细胞癌4例,占4%;肾嗜酸细胞腺瘤1例,占1%。78例肾透明细胞癌中CD10、波形蛋白阳性分别为63例(81%)和69例(88%),主要表现为细胞膜阳性。74/78肾透明细胞癌CK7呈阴性,17/17 Mowy胶状铁染色阴性或呈灶状粗颗粒。肾嫌色细胞癌4例,CK7均呈胞膜阳性;Mowy胶状铁染色表现为胞质内蓝色细网状;4例CD10肿瘤细胞膜均阴性,波形蛋白阴性。肾嗜酸细胞腺癌1例CD10,CK7,波形蛋白,Mowy胶状铁染色均为阴性或不特异。结论 在常规诊断肾上皮性肿瘤有困难时免疫组织化学CD10,CK7,波形蛋白染色以及Mowy胶状铁染色对鉴别诊断有帮助。  相似文献   
999.
身心因素与肠易激综合征患者生活质量的相关研究   总被引:1,自引:0,他引:1  
目的调查肠易激综合征(IBS)患者生活质量状况并评估躯体及心理因素对它的影响。方法采用肠易激综合征生活质量量表(IBS-QOL)、临床症状问卷、艾森克人格问卷简式(EPQ-RSC)、简明心境问卷简式(POMS-SF)、医学应对问卷(MCMQ)对120例IBS患者进行测查,将IBS患者的心理健康水平(人格、情绪、应对)及躯体症状(肠道症状、肠外症状、睡眠障碍)与IBS患者生活质量进行相关分析。结果IBS患者IBS-QOL的8个因子和总分均显著降低(P<0.05),其中健康忧虑和饮食限制降低最为明显,除IBS症状外,肠外症状、睡眠障碍、精神心理异常在IBS患者中也很常见。心理因素中EPQ-RSC神经质(N)分、POMS中焦虑、抑郁等多项因子分及总分、MCMQ屈服积分与IBS-QOL总分呈负相关;躯体因素中IBS症状、肠外症状、睡眠障碍积分与IBS-QOL总分呈负相关。结论肠易激综合征患者的生活质量明显降低,除躯体症状外,心理功能失调也是决定患者生活质量的重要因素。  相似文献   
1000.
A moveable sweating thermal manikin has recently been developed. Thermal and water-vapour resistances of three kinds of cold-protective clothing ensembles, laminated with polytetrafluoroethylene, polyurethane and without a laminate were measured, with the aid of the manikin in a cold environment of 5°C with a relative humidity of 70% and an air velocity of around 1.5 m s–1. Two sweating rates of 65 and 130 g m–2 h–1 were employed. Supplied heat fluxes in both of the sweat rates ranged from 350 W m–2 to 400 W m–2. To maintain a comfortable condition, the skin wettedness (w) (mean weighted value) had to be kept at 0.6. The measurements obtained from the manikin when testing the three ensembles were w=0.3 (approximately) for the low sweat rate and w0.6 for the high sweat rate, irrespective of the property differences among the ensembles. In addition, the condensation in the ensembles in comparison with those calculated from an analytical equation is discussed. Condensation mass fluxes in the ensembles obtained byexperiment and those from the calculation agreed sufficiently well. Thus, distribution of the condensation in the ensembles was estimated using the equation.  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