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   3517篇
  免费   219篇
  国内免费   92篇
儿科学   116篇
妇产科学   812篇
基础医学   631篇
口腔科学   8篇
临床医学   343篇
内科学   173篇
皮肤病学   17篇
神经病学   48篇
特种医学   99篇
外科学   76篇
综合类   719篇
预防医学   391篇
眼科学   3篇
药学   287篇
  4篇
中国医学   69篇
肿瘤学   32篇
  2023年   27篇
  2022年   77篇
  2021年   114篇
  2020年   122篇
  2019年   128篇
  2018年   135篇
  2017年   170篇
  2016年   185篇
  2015年   113篇
  2014年   260篇
  2013年   294篇
  2012年   167篇
  2011年   215篇
  2010年   162篇
  2009年   120篇
  2008年   157篇
  2007年   143篇
  2006年   161篇
  2005年   123篇
  2004年   119篇
  2003年   90篇
  2002年   89篇
  2001年   72篇
  2000年   59篇
  1999年   57篇
  1998年   51篇
  1997年   42篇
  1996年   29篇
  1995年   41篇
  1994年   35篇
  1993年   25篇
  1992年   31篇
  1991年   26篇
  1990年   13篇
  1989年   11篇
  1988年   24篇
  1987年   9篇
  1986年   10篇
  1985年   25篇
  1984年   12篇
  1983年   10篇
  1982年   9篇
  1981年   13篇
  1980年   8篇
  1979年   9篇
  1978年   8篇
  1977年   3篇
  1976年   9篇
  1974年   3篇
  1973年   6篇
排序方式: 共有3828条查询结果,搜索用时 31 毫秒
51.
A cell line has been established from human placentae at thefirst trimester of normal pregnancy. The cell line was obtainedby culture of purified cytotrophoblast cells in serum-free mediumsupplemented with epidermal growth factor, insulin, dexamethasoneand 0.1% bovine serum albumin. The cells can be subculturedfor >30 passages in one to three splits. All the cells weremononuclear epithelial-like cells positive to cytokeratin 18,gonadotrophin-releasing . hormone (GnRH), neuropeptide Y, neurotensin,leucine-enkephalin, dopamine and 5-hydroxytryptamine inununo-cytochemicalstaining. The cells secreted GnRH, progesterone and oestradiol(in the presence of testosterone) but little human chorionicgonadotrophin and no -endorphin. The cell line showed humankaryotypes and had a population doubling time of 48 h in serum-freemedium. However, the cells would stop growing in the mediumcontaining fetal bovine serum. A normal cytotrophoblast cellline established in serum-free medium will be particularly usefulin the study of cytotrophoblast cell proliferation and differentiation.  相似文献   
52.
Basement membrane thickening in the placentae from diabetic women   总被引:2,自引:0,他引:2  
A light microscopy study was carried out on 48 placentae. Seventeen placentae were obtained from non-diabetic mothers while the other 31 placentae were from both women with controlled diabetes and women who had an abnormality of the glucose tolerance test. All the women delivered at 38-40 weeks of gestation. Placentae from diabetic patients showed immaturity of the villi, hypertrophy of the capillaries and thickening of the basement membrane of the trophoblastic villi (3.2 +/- 0.35 microns) and the amniotic membrane (1.8 +/- 0.3 microns). Focal fibrinoid necrosis, an increase in the number of Hofbauer cells and dilatation of villi capillaries were also commonly observed in placentae from diabetic mothers, and the normal cuboidal cells lining the amniotic membrane tended to become tall columnar (17.6 +/- 6.3 microns) with distally located nuclei. Similar findings were observed in patients who had a potentially abnormal glucose tolerance test, which suggests the possibility of primary lesion in origin. Therefore, control of hyperglycemia may only partially prevent the development of placental abnormalities.  相似文献   
53.
Summary The influence of the lead content of drinking water on the transplacental transfer of lead was investigated in 70 pregnant women living in a rural area of Belgium. The mothers were divided into 2 groups: group A: morning water lead below 50 g/liter; group B: morning water lead above this value. In group A, the mean lead content of water was 11.8 g/liter and in group B it amounted to 247.4 g/liter.The difference in the mean lead concentration between the two groups were for maternal blood: 3.2 g/100 ml, for umbilical cord blood: 3.3 g/100 ml, and for placenta: 3.6 g/100 g. These differences are statistically significant.There were significant correlations between water lead and lead concentration in blood (mother, newborn) or placenta. An increment of water lead concentration from 50 to 500 g/liter increases blood lead concentration in mother and in newborn by about 3 g/100 ml and in placenta by about 2.5 g/100 g (wet weight).  相似文献   
54.
目的 通过对胎盘早剥的临床分析,探讨早期诊断及治疗方法,以降低孕产妇和围产儿死亡率。方法 对我院200l—2002年元月收治的qd胎盘早剥32例进行顾性分析。结果 围产儿死亡19例,死亡率59.3%,其中胎死宫内者17例,新生儿死亡2例。孕产妇32例中1例并发DIC及凝血功能障碍,经及时刨救治愈。无孕产妇死亡。结论 胎盘早剥的早期诊断更应注重病史及诱因,B超已成为胎盘早剥的重要辅助诊断方法。适时终止妊娠可减少母子严重的并发症。  相似文献   
55.
过期妊娠胎盘滋养细胞Bax、Bcl-2基因表达情况的研究   总被引:1,自引:0,他引:1  
目的 :通过观察过期妊娠患者促凋亡基因Bax和抑凋亡基因Bcl 2在胎盘滋养细胞层的表达 ,探讨细胞凋亡与过期妊娠的关系。方法 :采用免疫组织化学方法对20例过期妊娠和20例正常足月妊娠产妇的胎盘滋养细胞层Bax和Bcl 2基因表达进行检测和对比研究。结果 :胎盘滋养细胞层Bax和Bcl-2基因表达过期妊娠组分别为 (44 87±3 16) %和 (20 03±3 82) % ,足月妊娠组分别为 (43 89±3 96) %和 (34 14±3 85) %。2组比较Bax表达差别无统计学意义 (P>0 05) ,而Bcl 2表达差别有统计学意义 (P<0 05)。结论 :(1)胎盘滋养细胞层抑凋亡基因Bcl 2表达减少 ,可能与过期妊娠有关。 (2)胎盘滋养细胞层促凋亡基因Bax表达与过期妊娠无明显关系  相似文献   
56.
产后出血的高危因素分析   总被引:14,自引:0,他引:14  
目的 分析产后出血发生的相关危险因素 ,探讨预防和减少产后出血的措施。方法 对我院1 990年 1月~ 2 0 0 2年 1 2月间住院分娩的产妇出现产后出血的产妇 31 9例 ,对照 6 38例。通过多元Logistic回归分析评价各危险因素的相对危险性。结果 产后出血的发病率为 2 0 9%。相对独立的多个危险因素作用大小的顺位为 :胎盘粘连或植入、前置胎盘、多胎妊娠及胎儿体重≥ 4 0 0 0g、重度妊高征、流产次数≥ 2次、胎盘早剥 ;在阴道分娩的产妇中 ,作用相对独立的危险因素的顺位为胎盘粘连或植入、胎儿体重≥ 4 0 0 0g、妊高征、第三产程 >1 0min、流产次数≥ 2次。结论 避免产前非意愿妊娠以减少前置胎盘、胎盘粘连或植入 ;减少巨大儿、多胎的发生 ,有助于预防和减少产后出血  相似文献   
57.
The relationship of placenta previa and history of induced abortion.   总被引:5,自引:0,他引:5  
OBJECTIVES: We evaluated the risk of placenta previa being associated with a history of induced abortion by different surgical procedures. METHODS: Cases (n=192) were women who had a singleton delivery complicated by placenta previa at a major obstetric care hospital in western Washington state between April 1, 1990 and December 31, 1992. Controls (n=622) were women with singleton deliveries not complicated by placenta previa or abruption. Odds ratios, determined by logistic regression, approximate the relative risks. RESULTS: Vacuum aspiration abortion was not associated with an increased risk of placenta previa (OR 0.9, 95% CI 0.6-1.5). However, the risk of placenta previa increased with the number of sharp curettage abortions (OR 2.9, 95% CI 1.0-8.5 for > or =3). CONCLUSIONS: Risk of placenta previa may be increased in a dose response fashion by multiple sharp curettage abortions. However, vacuum aspiration does not confer an increased risk, and may be a better alternative.  相似文献   
58.
We examined the placentas of 12 patients in whom congenital cytomegalovirus CMV infection was suspected from serological and or pathological evaluation. Seven patients died including four intrauterine deaths and five survived. On histological examination, the characteristic inclusion bodies were detected in only three placentas, and villitis with plasma cell infiltration was seen in eight placentas. Immunohistochemistry using a specific antibody against CMV improved the sensitivity of CMV detection 10 cases were positive . With the polymerase chain reaction PCR following the extraction of DNA from formaldehyde-fixed placenta samples, CMV DNA was detected in seven cases. All 12 subjects were diagnosed with CMV infection by additional Southern blot analysis after the PCR. CMV DNA was also detected by an in situ hybridization method in all cases. With current molecular biological techniques the placenta can be reliably used for the diagnosis of congenital CMV infection.  相似文献   
59.
Increased placental apoptosis in intrauterine growth restriction   总被引:2,自引:0,他引:2  
OBJECTIVES: Our purpose was to investigate a possible role for apoptosis in the pathophysiologic mechanisms of intrauterine growth restriction. STUDY DESIGN: Placental samples were obtained from 43 uncomplicated third-trimester pregnancies and from 26 pregnancies complicated by intrauterine growth restriction. The definition used to identify cases of intrauterine growth restriction depended on three criteria: clinical evidence of suboptimal growth, ultrasonographic evidence of deviation from an appropriate growth percentile, and individualized birth weight ratios <10th percentile. Light microscopy was used to quantify the incidence of apoptosis. Electron microscopy and TUNEL (terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick end labeling) staining were used to confirm the occurrence of apoptosis. RESULTS: Quantification of apoptosis (medians and interquartile ranges) resulted in the following values: normal third trimester (n = 43) 0.14% of cells (0.08% to 0.20%) and intrauterine growth restriction third trimester (n  = 26) 0.24% of cells (0.16% to 0.29%). The incidence of apoptosis was significantly higher in placentas from pregnancies with intrauterine growth restriction compared with normal third-trimester placentas (p < 0.01, Mann Whitney U test). CONCLUSIONS: These results suggest that apoptosis may play a role in the pathophysiologic mechanisms of intrauterine growth restriction.(Am J Obstet Gynecol 1997;177:401)  相似文献   
60.
Choriocarcinoma arising in the placenta, or intraplacental choriocarcinoma, has seldom been reported, particularly in the absence of maternal metastases. Reluctance to diagnose choriocarcinoma in the presence of chorionic villi can delay diagnosis; however, timely diagnosis of choriocarcinoma is prognostically important, both for the mother and infant. We report the clinicopathologic findings in five mothers and infants in whom choriocarcinoma was identified in the placenta. None of the mothers had a history of gestational trophoblastic disease in previous pregnancies. Three placentas were similar with a single small lesion grossly suggesting a small infarct; microscopically these consisted of infarcted areas surrounded by choriocarcinoma. These three mothers were unusual in that none had metastatic choriocarcinoma; two were treated with chemotherapy and remained disease-free; the third was lost to follow-up shortly following delivery. The remaining two mothers had known pulmonary metastases at time of delivery. One of these latter two placentas contained a large marginal lesion microscopically identified as choriocarcinoma. The fifth placenta had rare microscopic foci of choriocarcinoma, and sheets of necrotic choriocarcinoma were identified in “blood clot” submitted with the placenta. In four of the five cases the choriocarcinoma appeared to be arising from otherwise normal chorionic villi, and in no case was there invasion of the villous stroma. All of the infants survived, and none had evidence of choriocarcinoma. These cases support the concept that choriocarcinoma associated with otherwise normal pregnancy arises in the placenta and may be more common than reported. Received August 11, 1997; accepted December 8, 1997.  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