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   14583篇
  免费   893篇
  国内免费   272篇
耳鼻咽喉   69篇
儿科学   535篇
妇产科学   422篇
基础医学   881篇
口腔科学   128篇
临床医学   4242篇
内科学   1088篇
皮肤病学   89篇
神经病学   437篇
特种医学   1559篇
外科学   1462篇
综合类   2433篇
预防医学   784篇
眼科学   171篇
药学   749篇
  11篇
中国医学   195篇
肿瘤学   493篇
  2024年   29篇
  2023年   214篇
  2022年   561篇
  2021年   670篇
  2020年   599篇
  2019年   539篇
  2018年   541篇
  2017年   571篇
  2016年   430篇
  2015年   475篇
  2014年   1051篇
  2013年   913篇
  2012年   943篇
  2011年   906篇
  2010年   767篇
  2009年   729篇
  2008年   730篇
  2007年   660篇
  2006年   653篇
  2005年   501篇
  2004年   433篇
  2003年   344篇
  2002年   231篇
  2001年   241篇
  2000年   225篇
  1999年   179篇
  1998年   149篇
  1997年   147篇
  1996年   114篇
  1995年   119篇
  1994年   105篇
  1993年   64篇
  1992年   73篇
  1991年   63篇
  1990年   44篇
  1989年   51篇
  1988年   44篇
  1987年   44篇
  1986年   62篇
  1985年   54篇
  1984年   38篇
  1983年   47篇
  1982年   71篇
  1981年   62篇
  1980年   33篇
  1979年   38篇
  1978年   64篇
  1977年   25篇
  1976年   42篇
  1975年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
While anxiety appears to characterize humans who administer high doses of cocaine or experience withdrawal from cocaine, it is difficult to capture this aspect of cocaine effects in animals. The present study investigated if acute or protracted withdrawal from prolonged low-dose cocaine that is self-administered via the oral route could be detected in tactile startle and vocal distress responses of rats. Adult, male Long-Evans rats had access to cocaine solution (0.1 mg/ml) either for 24 or 4 h/day using the two-bottle choice technique. The amount of solution consumed from each bottle was measured daily for 30 or 60 days. On days 1, 3, 7, 14, 21, 28 of withdrawal, startle and ultrasonic vocal responses (USV, 15–35 kHz) were measured in response to 18 airpuff stimuli (20 psi). Rats drank an average of 5–20 mg/kg per day of the cocaine solution. On average, about half of the daily liquid was consumed from the cocaine solution-containing bottle. USVs were emitted at significantly increased rates on day 3 of withdrawal from 30 or 60 days of cocaine drinking. Startle reactions were slightly, but non-significantly increased on day 1 of withdrawal. Comparable to withdrawal from ethanol, morphine, and diazepam treatments, withdrawal from oral self-administration of low to moderate doses of cocaine increases the rate of ultrasonic vocalizations while increasing minimally the amplitude of startle responses to low-intensity tactile stimuli. Nevertheless, no correlation between the total amount of cocaine self-administered or the duration of treatment with the intensity of the withdrawal manifestations could be detected.  相似文献   
122.
The aim of our study was to evaluate the validity of a quantitative US technique for measuring the bone density of the proximal phalanges of the nondominant hand compared with computed metacarpal radiogrammetry and dual-photon absorptiometry (DPA) of the lumbar spine. Mean US bone velocity (UBV) correlated with mean metacarpal cortical index (MCI), with mean metacarpal bone density (MBD) and with bone mineral density (BMD) of the lumbar spine, whereas it was correlated negatively with age and menopause duration. The average UBV was significantly higher in premenopausal women than in postmenopausal women, and higher in normal lumbar DPA patients than in reduced lumbar DPA patients. We conclude that the US evaluation of the nondominant hand proximal phalanges may be a new alternative way for measuring bone mass in screening of osteoporosis. Correspondence to: A. Sili Scavalli  相似文献   
123.
The last decade has been marked by the development of liposuction. A better knowledge of the anatomy of fat tissue, together with an improvement in different devices, has made our results more predictable. However, such areas as the chin, anterior and inner thigh, and knee have remained difficult. This is especially true when large volumes of fat need to be removed. Blood loss has remained a problem as well. The development of ultrasound (U.S.) liposuction is a big step toward even more predictable results and to where blood loss can be negligible.Lipectron B.U.S. Endotron is a device manufactured by and available from MEDICA MAT s.a., Avenue Augustin Dumont 59, F-92240 MALAKOFF.  相似文献   
124.
目的评价经超声引导成人与儿童肾活检术的方法和安全性。方法83例肾脏病患者超声引导下经皮穿刺活检,经右肾或左肾下极进针,方向自外下向内上,沿肾下极皮质取材。结果68例获取足够肾组织,总成功率及3针以内成功率分别为82%、53%,成人与儿童间无差异(P>0.05)。肾活检并发症儿童以疼痛为主,成人以血尿为主。结论超声引导下成人与儿童肾活检术是安全可靠的,其病理诊断对临床治疗具有明确的指导意义。  相似文献   
125.
超声治疗外阴白色病变30例临床分析   总被引:17,自引:0,他引:17  
目的 :探讨超声治疗外阴白色病变的临床疗效。方法 :收治外阴白色病变 6 0例 ,随机分为 :超声治疗组 30例 ,微波治疗对照组 30例。观察其临床症状、体征和组织学变化。结果 :超声治疗组 30例患者的外阴瘙痒症状基本消失 ,患处上皮不同程度地恢复正常 ,显效率达 90 %。不同的病理类型间疗效的比较 ,差异无显著性 (P >0 .0 5 )。结论 :用超声治疗外阴白色病变效果明显  相似文献   
126.
OBJECTIVES: Presently, a design-based and practical method for measuring amniotic fluid volume (AFV) for routine clinical examinations has not been proposed. In this study we describe a new method, which combines the Cavalieri method with ultrasound imaging to estimate AFV. METHODS: We measured the AFVs of 14 women in the third trimester of pregnancy, and repeated our measurements three times for each woman. Parallel planimetric ultrasonographic images were obtained at every 2 cm along the longitudinal uterine axis. AFVs were calculated as the total of the multiples of the estimated cut surface areas by the section thickness. RESULTS: The mean estimated AFV was 380.5 cm3. The coefficient of error of each measurement was calculated and the mean was 0.108. The coefficient of correlation between the amniotic fluid index and our AFV estimations was 0.87. CONCLUSIONS: Design-based and efficient estimation of AFV is possible with the combination of consecutive ultrasound images and the Cavalieri method.  相似文献   
127.
Body mass is known to be related to measures of bone mineral density (BMD) as well as to parameters of quantitative ultrasound (US). To examine the effect of the body compartment's fat mass and lean body mass on quantitative ultrasonic bone parameters, data from a sample of 3241 German women were analyzed. Anthropometric measures, including skinfold thickness, were obtained from standardized measurements, and fat and lean body mass were derived from classical regression formulas based on skinfold measurements. Ultrasonic bone measurements were performed on the right os calcis, and speed of sound (SOS) and broadband ultrasound attenuation (BUA) were determined. Women were grouped into pre- and postmenopausal status; postmenopausal women were further stratified into ever and never hormone-replacement user. Correlation analysis indicated lean body mass to be stronger correlated with BUA than fat mass in both pre- (r = 0.23; P= 0.0001) and postmenopausal women with (r = 0.19; P= 0.0001) and without hormone replacement therapy (HRT) (r = 0.26; p = 0.0001). SOS demonstrated very small or no associations with body mass or its components. Multiple linear regression models were used to describe the relationship among body weight, fat mass, and lean body mass on BUA after adjustment for confounding variables. Both in pre- and postmenopausal women lean body mass was more strongly related to BUA than fat mass. However, body mass measures explained only small amounts of the overall variance in BUA (R2= 1–3% in premenopausal women; R2= 1% postmenopausal with HRT; R2= 4–5% in postmenopausal women without HRT). In conclusion, the strong influence of body mass and its components previously reported for BMD was not observed for quantitative ultrasonic bone parameters. Received: 5 January 1999 / Accepted: 1 July 1999  相似文献   
128.
不同类型的地物具有不同的反射光谱 ,在多维光谱空间中构成不同的特征向量 ,这便是遥感多光谱图象分析与识别的物理依据。传统方法中有基于单个象元波段亮度的、空间纹理的、变换空间的多光谱图象特征提取与分析方法 ,但这些方法并没有直接描述地物的最本质特征———反射光谱曲线 ,从上个世纪 80年代开始 ,当二进制编码的方法提出并在多光谱匹配识别中获得成功应用后 ,多光谱图象分析处理便可以在这种特征提取的基础上 ,研究新的方法。本文提出一种基于光谱形状描述的多门限的二进制编码分类方法 ,并给出了图象实验的结果。  相似文献   
129.
男性乳癌特征分析(附31例报告)   总被引:2,自引:0,他引:2  
目的:了解男性乳癌特点,提高其早期诊断率及治疗效果。方法:对31例男性乳癌进行了回顾性分析。结合随访资料,应用Kaplan-Meier法进行生存分析。结果:男性乳癌少见,病因不清,发病多在50岁以上,临床病例晚期多见,容易侵犯皮肤及胸肌,乳头常受累,可伴乳头溢血,淋巴结转移较早,雌激素受体阳性率高,治疗以手术为主,主要是改良根治术,包括化疗,内分泌治疗和放疗的综合治疗,预后与腋淋巴结转移状况有关。结论:男性乳癌晚期多见,治疗以综合治疗为主。预后与腋淋巴结转移状况相关。  相似文献   
130.
陈钢 《中国肿瘤临床》2003,30(4):247-249
分析遗传性非息肉病性大肠癌(HNPCC)的临床特点。方法:对10个家族27例HNPCC患者(A组)进行回顾性分析,并设30例一般大肠癌为对照组(B组)进行比较。结果:<50岁患者A组占59.3%(16/27),B组占23.3%(7/30),P<0.05。脾曲以上癌灶A组为40.0%(12/30),B组为16.1%(5/31),P<0.05。大肠多原发癌A组占10.0%(3/30),B组占3.2%(1/31)。大肠外肿瘤A组6例,B组2例。结论:HNPCC具有典型的临床特征,这些特征可以对HNPCC患者进行早期诊断及治疗,以得到较好的预后。  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