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   8551篇
  免费   401篇
  国内免费   52篇
耳鼻咽喉   49篇
儿科学   203篇
妇产科学   121篇
基础医学   1151篇
口腔科学   187篇
临床医学   581篇
内科学   2293篇
皮肤病学   234篇
神经病学   627篇
特种医学   312篇
外科学   1430篇
综合类   52篇
预防医学   300篇
眼科学   162篇
药学   546篇
中国医学   20篇
肿瘤学   736篇
  2023年   46篇
  2022年   97篇
  2021年   170篇
  2020年   92篇
  2019年   122篇
  2018年   171篇
  2017年   128篇
  2016年   173篇
  2015年   150篇
  2014年   214篇
  2013年   234篇
  2012年   420篇
  2011年   452篇
  2010年   255篇
  2009年   237篇
  2008年   415篇
  2007年   489篇
  2006年   501篇
  2005年   437篇
  2004年   417篇
  2003年   460篇
  2002年   424篇
  2001年   337篇
  2000年   340篇
  1999年   285篇
  1998年   119篇
  1997年   75篇
  1996年   66篇
  1995年   61篇
  1994年   49篇
  1993年   59篇
  1992年   159篇
  1991年   143篇
  1990年   143篇
  1989年   133篇
  1988年   100篇
  1987年   92篇
  1986年   76篇
  1985年   82篇
  1984年   49篇
  1983年   44篇
  1979年   55篇
  1978年   34篇
  1977年   30篇
  1973年   36篇
  1972年   29篇
  1971年   30篇
  1969年   27篇
  1968年   31篇
  1966年   25篇
排序方式: 共有9004条查询结果,搜索用时 0 毫秒
1.
2.
3.
The efficacy of non-pharmacological intervention for chronic insomnia has been proven by several meta-analytic reviews, an NIH report, an American Academy of Sleep Medicine review, and numerous clinical trials. Behavior therapy for chronic insomnia consists of relaxation, stimulus control, sleep restriction, cognitive restructuring and sleep hygiene education, which has produced reliable and durable changes in total sleep time, sleep onset latency, number and duration of awakening. These studies also showed that the post-treatment effect of behavior therapy is equal to that of hypnotic therapy, and that these effects were maintained for 6 months on follow-up assessment. Elderly insomniac patients would gain considerable benefit from behavioral treatments because there are no adverse physical effects as there are from pharmacological therapy. The authors present the basic theory, techniques of behavior therapy for insomnia, and the results of two important key meta-analytic reviews. Any behavioral approach such as convenient education, self-care enhancement by bibliotherapy, and individual face-to-face counseling, seem to be fruitful not only for American but also Japanese insomnia patients. Nonetheless, there are no currently actual intervention studies using behavior therapy in Japan. We have discussed the methodology of intervention study and published a behavioral self-help manual for people with sleep problems. Development of a behavioral approach to chronic insomnia seemed to be very beneficial and a useful contribution to mental health services.  相似文献   
4.
Pancreatic metastasis of malignant melanoma is rarely diagnosed while the patient is alive. We report a case of metastatic melanoma of the pancreas in a 35-year-old woman presenting with a solid mass of the pancreas. Her past medical history included a radical hysterectomy 2 years previously for malignant melanoma of the vagina. Twelve months later, lung metastasis was also resected. EUS-guided fine needle aspiration (EUS-FNA) identified that the pancreatic tumor was histologically and immunohistochemically identical to the surgical specimen of her lung neoplasm. Imaging studies including US, CT, and MRI have limited value to distinguish the tumors from primary ductal adenocarcinoma. EUS-FNA can provide tissue diagnosis from pancreatic masses, specifically when other modalities have failed.  相似文献   
5.
The effects of 3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinolinone (vesnarinone) on the growth of glioma cells were examined in vitro. Vesnarinone at a dose of 100 mug/ml suppressed the growth of four different glioma cell lines, U-251MG, U-373MG, U-87MG and A-172, by approximately 50%, with an elongation of the cytoplasmic process on day 5 of culture. The long-term culture of U-87MG with 10 mug/ml of vesnarinone was continued up to day 34. Although growth suppression was approximately 25% on day 5, it reached over 95% on day 34. An increase in the cyclic adenosine monophosphate content of glioma cells cultured with vesnarinone was observed by enzyme-linked immunosorbent assay (ELISA). The accumulation of glial fibrillary acidic protein was observed to occur with vesnarinone by ELISA. These findings suggest that vesnarinone suppressed the growth and induced differentiation of glioma cells in vitro.  相似文献   
6.
The matrix metalloproteinase matrilysin (MMP-7) is a member of the matrix metallo-proteinase gene family, which is believed to play an important role in tumor invasion and metastasis. We have previously found that matrilysin mRNA is specifically expressed in colorectal cancers and adenomas and that its message is localized in the tumor cells themselves. We examined the effects of activated Ki-ras oncogene on the expression of matrilysin in colon cancer cells. We showed that both mRNA and the enzymatic activity of matrilysin were induced by the introduction of activated Ki-ras into SW1417 colon cancer cells. To understand the mechanisms regulating this induction, we analyzed alterations of AP-1 activity induced by activated Ki-ras, using the chloramphenicol acetyltransferase assay. AP-1 activity in SW1417 cells expressing activated Ki-ras was higher than that in control cells. The gel-shift assay also showed higher levels of AP-1 binding protein in SW1417 cells expressing activated Ki-ras than those in control cells. Our results suggest that activated Ki-ras may play a role in inducing expression of matrilysin through an AP-1-dependent pathway in colon cancer cells.  相似文献   
7.
OBJECTIVES: 1) To assess, with a peripheral magnetic resonance imaging system (pMRI), the prevalence of bony and soft tissue abnormalities in the knee joints of normal subjects, osteoarthritis (OA) patients, and individuals who have suffered an anterior cruciate ligament (ACL) rupture; and 2) to compare the prevalence among groups. METHODS: Magnetic resonance (MR) images of 28 healthy, 32 OA, and 26 ACL damaged knees were acquired with a 1.0-T pMRI system. Two radiologists graded the presence and severity of 9 MR image features: cartilage degeneration, osteophytes, subchondral cyst, bone marrow edema, meniscal abnormality, ligament integrity, loose bodies, popliteal cysts, and joint effusion. RESULTS: Ten of 28 healthy (35.7%), 24 of 26 ACL (92.3%), and all OA knees (100%) showed prevalent cartilage defects; 5 healthy (17.9%), 20 ACL (76.9%), and all OA knees (100%) had osteophytes; and 9 normal (32.1%), 21 ACL (80.8%), and 29 OA knees (90.6%) had meniscal abnormalities. One-half of the knees in the OA group (16 of 32, 50%) had subchondral cysts, and almost one-half had bone marrow edema (15 of 32, 46.9%). These features were not common in the ACL group (7.7%, and 11.5%, respectively) and were not observed in healthy knees. The OA group had the most severe cartilage defects, osteophytes, bone marrow edema, subchondral cysts, and meniscal abnormalities; the ACL group showed more severe cartilage defects, osteophytes, and meniscal abnormalities than did normal subjects. CONCLUSION: The results suggest that knees that have sustained ACL damage have OA-like reatures; most subjects (19 of 26, 73.1%) could be identified as in the early stage of OA. The prominent abnormalities present in ACL-damaged knees are cartilage defects, osteophytes, and meniscal abnormalities.  相似文献   
8.
9.
The impact of clinical risk factor-based absolute risk methods on the prevalence of high risk for osteoporotic fracture is unknown. We applied absolute risk methods to 6646 subjects and found that the prevalence of elderly women deemed to be at high risk increased substantially, whereas the overall prevalence was highly dependent on the threshold used to designate high risk. INTRODUCTION: Many groups have advocated using absolute risk methods that incorporate clinical risk factors to target patients for osteoporosis therapy. We examined how the application of such absolute risk classification systems influences the prevalence of those considered to be at high risk for osteoporotic fracture and compared these systems to one based solely on BMD. MATERIALS AND METHODS: Using 6646 subjects from the Canadian Multicentre Osteoporosis Study (CaMos), a prospective, randomly selected, population-based cohort, we assessed three different systems for determining prevalence of high risk for osteoporotic fracture: a BMD-based system; a simplified risk factor system incorporating age, sex, BMD, and two clinical risk factors; and a comprehensive system, incorporating age, sex, BMD, and seven clinical risk factors. The 10-year absolute risks of incident fragility fracture were compared across systems using three different high-risk thresholds. RESULTS: The prevalence of a T score < or = -2.5 was 18.8% (95% CI: 17.7-19.9%) in women and 3.9% (95% CI: 3.0-4.7%) in men. Using a 15% 10-year risk of fracture threshold, the prevalence of women at high risk increased to 46.9% (95% CI: 45.4-48.4) and 42.5% (95% CI: 41.1-43.9) when the comprehensive and simplified risk factor classification systems were used, respectively. Using a 25% 10-year absolute risk threshold, the prevalence of high risk was similar to that of the BMD-based system, whereas the 20% threshold gave intermediate rates. All thresholds analyzed resulted in an increased prevalence of older women at high risk for fracture, whereas only the 15% 10-year risk of fracture threshold resulted in an increase in the prevalence of men at high risk. CONCLUSIONS: The application of risk factor-based systems results in an increased prevalence of older women at high risk. The prevalence of individuals at high risk may increase with changes to the methods used to determine those who are eligible for therapy. These data have important implications for the pattern of care and costs of treating osteoporotic fractures.  相似文献   
10.
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