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   2399篇
  免费   93篇
  国内免费   62篇
耳鼻咽喉   14篇
儿科学   35篇
妇产科学   25篇
基础医学   374篇
口腔科学   65篇
临床医学   133篇
内科学   523篇
皮肤病学   39篇
神经病学   182篇
特种医学   278篇
外科学   208篇
综合类   131篇
预防医学   120篇
眼科学   44篇
药学   157篇
  1篇
中国医学   2篇
肿瘤学   223篇
  2023年   17篇
  2022年   22篇
  2021年   45篇
  2020年   24篇
  2019年   25篇
  2018年   42篇
  2017年   40篇
  2016年   41篇
  2015年   68篇
  2014年   86篇
  2013年   101篇
  2012年   171篇
  2011年   152篇
  2010年   120篇
  2009年   80篇
  2008年   126篇
  2007年   132篇
  2006年   144篇
  2005年   116篇
  2004年   123篇
  2003年   79篇
  2002年   55篇
  2001年   72篇
  2000年   55篇
  1999年   51篇
  1998年   57篇
  1997年   48篇
  1996年   42篇
  1995年   32篇
  1994年   33篇
  1993年   24篇
  1992年   24篇
  1991年   17篇
  1990年   12篇
  1989年   36篇
  1988年   27篇
  1987年   21篇
  1986年   31篇
  1985年   26篇
  1984年   9篇
  1983年   8篇
  1982年   19篇
  1981年   12篇
  1980年   15篇
  1979年   4篇
  1978年   8篇
  1977年   13篇
  1976年   11篇
  1975年   10篇
  1972年   6篇
排序方式: 共有2554条查询结果,搜索用时 0 毫秒
41.
This work reports new findings on the formation of a pearl-necklace pattern in self-assembled upconverting nanocrystals (UCN-PNs) which exhibit strong upconversion emission under an NIR excitation source of a femtosecond laser (Fs-laser). Each nano-necklace consists of several upconversion nanoparticles (UCNPs) having a size ca. 10 ± 1 nm. UCN-PNs are arranged in a self-organized manner to form necklace type chains with an average length of 140 nm of a single row of nanoparticles. Furthermore, UCN-PNs are comprised of UCNPs with an average interparticle separation of ca. 4 nm in each of the nanonecklace chains. Interestingly, these UCN-PNs exhibit high energy upconversion especially in the UV region on interaction with a 140 Fs-laser pulse duration at 80 MHz repetition rate and intense blue emission at 450 nm on interaction with a 900 nm excitation source is obtained. The preparation of self-assembled UCNPs is easy and they are very stable for a longer period of time. The emission (fluorescence/luminescence) intensity is very high which can make them unique in innumerable industrial and bio-applications such as for disease diagnosis and therapeutic applications by targeting the infected cells with enhanced efficiency.

Self-assembled pearl necklace patterned-upconverting nanoparticles and their femtosecond laser based upconversion properties.  相似文献   
42.
Hilar cholangiocarcinoma is a tumor of the extrahepatic bile duct involving the left main hepatic duct, the right main hepatic duct, or their confluence. Biliary drainage in hilar cholangiocarcinoma is sometimes clinically challenging because of complexities associated with the level of biliary obstruction. This may result in some adverse events, especially acute cholangitis. Hence the decision on the indication and methods of biliary drainage in patients with hilar cholangiocarcinoma should be carefully evaluated. This review focuses on the optimal method and duration of preoperative biliary drainage(PBD) in resectable hilar cholangiocarcinoma. Under certain special indications such as right lobectomy for Bismuth type ⅢA or Ⅳ hilar cholangiocarcinoma, or preoperative portal vein embolization with chemoradiation therapy, PBD should be strongly recommended. Generally, selective biliary drainage is enough before surgery, however, in the cases of development of cholangitis after unilateral drainage or slow resolving hyperbilirubinemia, total biliary drainage may be considered. Although the optimal preoperative bilirubin level is still a matter of debate, the shortest possible duration of PBD is recommended. Endoscopic nasobiliary drainage seems to be the most appropriate method of PBD in terms of minimizing the risks of tract seeding and inflammatory reactions.  相似文献   
43.
The objective of the study was to investigate the association between metabolic syndrome (MS) and muscle strength in community-dwelling older men and women in Korea. Korean men and women 65 years and older living in a single, typical South Korean city (n = 647) were enrolled in the Korean Longitudinal Study on Health and Aging study. The diagnosis of MS was evaluated according to the definition of the National Cholesterol Education Program Adult Treatment Panel III. Isokinetic muscle strength of the knee extensors, as determined by peak torque per body weight (newton meter per kilogram) and hand-grip strength per body weight (newton per kilogram), was measured. Participants without MS had greater leg muscle strength and grip strength per weight. The effect of MS on muscle strength was more prominent in men than in women in our study population. Only men showed a significant interaction between MS and age for muscle strength (P = .014), and the effect was greater in men aged 65 to 74 years compared with those older than 75 years (119.2 ± 31.2 vs 134.5 ± 24.3 N m/kg). Participants with MS had weaker knee extensor strength after controlling the covariates (β = -90.80, P = .003), and the interaction term (age × MS × male sex) was significant (β = 1.00, P = .017). Metabolic syndrome is associated with muscle weakness, and this relationship is particularly pronounced in men. Age can modify the impact of MS on muscle strength. Men aged 65 to 74 years with MS need a thorough assessment of muscle strength to prevent disability.  相似文献   
44.
45.
The aim of this study was to examine in detail the anatomic variations in the orbicularis oculi muscle (OOc) and relationship of the zygomaticus minor muscle (ZMi) with the OOc, thereby providing an anatomic basis for explaining facial animation and attachment to the periorbital muscle. Sixty-one hemifaces from embalmed Korean adult cadavers (34 males, 27 females; age range, 45-85 years; mean age, 62.6 years) were used in this study. The prevalence of cases in which the ZMi did not run straight from the upper lip, rather running straight to the corner of the levator labii superioris, was 36.1% (22/61), because the origin of ZMi covered the inferior border of the OOc. The prevalence of mixing of the belly of the orbital part of the outer edge of the OOc with the ZMi was 88.5%, and that of blending of the ZMi band into the lower inner corner of the OOc was 55.7%. The area of blending of the OOc and ZMi was located 17.8 mm down from the Frankfort plane and 8.9 mm lateral to the vertical line between the lateral canthus and the Frankfort plane in the lateral part of the OOc. At this position, the mixed belly extends medially for a distance of 16 mm. This research has identified the exact location where the ZMi and OOc blend and determined the relationship between the ZMi and the suborbicularis oculi fat. This result will be given as basic data for understanding facial expressions and for performing composite rhytidectomy.  相似文献   
46.
47.

Background

The ethnic usage of exotics and indigenous problem plants is a highly debated topic, as legislative requirements over-shadow their potential medicinal value, particularly to treat sexually transmitted infections (STIs). Limited information exists regarding their medicinal value among the Bapedi.

Objectives

To ascertain the importance of exotics and indigenous problem plants in the treatment of STIs, a major global primary health care challenge.

Methods

A field observation and semi-structured questionnaire focussing on species diversity, types of STIs treated and medicinal preparation as well as application was used to collect data from 34 traditional healers.

Results

Seven exotics and three indigenous problem species were identified. These species were used to treat four STIs; with Catharanthus roseus illustrating its dominance in the treatment of gonorrhoea. Some medicinal species used by Bapedi traditional healers have been validated through scientific research or through their extensive use by various cultures in South Africa and other parts of Africa. To the best of our knowledge Alternanthera pungens, Caesalpinia decapetala, Cinnamomum verum, and Citrullus lanatus are reported for the first time in the treatment of the investigated STIs.

Conclusions

Exotic and indigenous problem species constitute an important component of the STIs treatment protocol. Their utilization by Bapedi cautions against the narrow-minded approach of indiscriminate eradication, as these species can play a significant role in the primary health care needs of socio-economic vulnerable people.  相似文献   
48.
49.
Hepatoid adenocarcinoma (HAC) is a rare type of extrahepatic carcinoma whose morphology is similar to that of hepatocellular carcinoma (HCC). Metachronous HCC and HAC in the same patient is extremely rare. The case of a 68-year-old man with chronic hepatitis B infection who had both HCC and HAC of the stomach is reported herein. Nine years previously this patient had been diagnosed with HCC and received a right lobectomy. HCC that recurred at the caudate lobe at 6 months after the operation was successfully treated with transarterial chemoembolization. The patient was followed up regularly thereafter without evidence of tumor recurrence for 9 years. In July 2010 his serum alpha-fetoprotein (AFP) level elevated from 6.5 ng/mL to 625.4 ng/mL, and he developed a probable single metastatic lymph node around the hepatic artery without intrahepatic lesions. Subsequent evaluation with upper endoscopy revealed a 4-cm ulcerative lesion on the antrum of the stomach. Subtotal gastrectomy was performed with lymph-node dissection. Histologic examination revealed a special type of extrahepatic AFP-producing adenocarcinoma-HAC with lymph-node metastasis-which indicates that HAC can be a cause of elevated AFP even in patients with HCC. HAC should be considered if a patient with stable HCC exhibits unusual elevation of AFP.  相似文献   
50.
Castleman's disease is a rare disease characterized by lymph node hyperplasia. Although Castleman's disease can occur wherever lymphoid tissue is found, it rarely appears in the abdominal cavity, and is especially rare adjacent to the liver. Here, we report a rare case of Castleman's disease in the portal area that mimicked a hepatocellular carcinoma (HCC) in a chronic hepatitis B patient. A 40 year-old woman with chronic hepatitis B presented with right upper quadrant discomfort. Computed tomography and magnetic resonance imaging results showed a 2.2 cm-sized, exophytic hypervascular mass in the portal area. HCC was suspected. However, histologic examination revealed Castleman's disease. We suggest that Castleman's disease should be included as a rare differential diagnosis of a hypervascular mass in the portal area, even in patients with chronic hepatitis B.  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