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   12136篇
  免费   1108篇
  国内免费   41篇
耳鼻咽喉   119篇
儿科学   349篇
妇产科学   190篇
基础医学   1693篇
口腔科学   479篇
临床医学   1474篇
内科学   2610篇
皮肤病学   100篇
神经病学   888篇
特种医学   387篇
外科学   1779篇
综合类   199篇
一般理论   15篇
预防医学   1089篇
眼科学   201篇
药学   935篇
中国医学   4篇
肿瘤学   774篇
  2023年   70篇
  2022年   95篇
  2021年   311篇
  2020年   172篇
  2019年   298篇
  2018年   354篇
  2017年   263篇
  2016年   274篇
  2015年   276篇
  2014年   422篇
  2013年   516篇
  2012年   810篇
  2011年   872篇
  2010年   481篇
  2009年   443篇
  2008年   727篇
  2007年   704篇
  2006年   683篇
  2005年   750篇
  2004年   653篇
  2003年   610篇
  2002年   576篇
  2001年   229篇
  2000年   185篇
  1999年   214篇
  1998年   147篇
  1997年   120篇
  1996年   113篇
  1995年   95篇
  1994年   75篇
  1993年   71篇
  1992年   154篇
  1991年   125篇
  1990年   120篇
  1989年   127篇
  1988年   100篇
  1987年   97篇
  1986年   78篇
  1985年   81篇
  1984年   70篇
  1983年   67篇
  1982年   48篇
  1981年   50篇
  1980年   35篇
  1979年   52篇
  1978年   46篇
  1977年   51篇
  1976年   44篇
  1975年   38篇
  1970年   34篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Potential for widespread transmission of HIV/AIDS among American Indian (AI) adolescents exists, yet no evidence-based interventions (EBIs) have been adapted and evaluated with this population. Intensive psychoeducation may improve knowledge and decision-making which could potentially translate to reductions in HIV risk behaviors. A peer group randomized controlled comparison of an adapted EBI vs. control was delivered over an eight-day summer basketball camp in one reservation-based tribal community to adolescents ages 13–19. Outcome data were gathered immediately post-camp and at 6 and 12 months follow-up. Self-selected peer groups were randomized to intervention (n = 138) or control (n = 129) conditions for a total sample of 267 participants (56.2% female), mean age 15.1 years (SD = 1.7). Intervention participants had better condom use self-efficacy post-camp (Adjusted Mean Difference [AMD] = ?0.75, p < 0.005) and at 6 (AMD = ?0.44, p < 0.005) and 12 months (AMD = ?0.23, p < 0.05) follow-up. Intervention participants also had higher HIV prevention and transmission knowledge (post-camp: AMD = 0.07, p < 0.01; 6 months: AMD = 0.06, p < 0.01) were more likely to believe condoms prevent sexually transmitted infections (post-camp: RR = 1.41, p < 0.005; 6 months: RR = 1.34, p < 0.05), to talk with an adult about HIV/AIDS (post-camp: RR=1.78, p < 0.005; 6 months: RR = 1.14, p < 0.005), had higher partner negotiation efficacy related to substance use during sex (post-camp: AMD = 0.37, p < 0.01), and were more likely to intend to use a condom (post-camp: RR = 1.39, p < 0.01). The adapted intervention had short- and medium-term impacts on AI adolescent risk for HIV/AIDS, but attenuated at 12 months. Intervention delivery through a community-based camp is feasible and acceptable with strong retention. Additional study is needed to evaluate the adapted intervention's impact on sexual risk behaviors and if booster sessions and parent involvement translate to long-term impacts.  相似文献   
2.
3.
Choledochal cysts (CDCs) and biliary atresia (BA) are rare pediatric hepatobiliary anomalies that require surgical intervention due to increased risk of malignancy and liver failure, respectively. The underlying disease and operative procedures place patients at risk for long‐term complications, which may continue to affect them into adulthood. Lack of a transitional care model in the health‐care system potentiates the challenges they will face following aging out of their pediatric providers' care. We sought to elucidate the long‐term complications and challenges patients with CDCs and BA face, review the current literature regarding transitioning care, and propose guidelines aiding adult providers in continued care and surveillance of these patients. A literature review was performed to assess short‐term and long‐term complications after surgery and the current standards for transitioning care in patients with a history of CDCs and BA. While transitional programs exist for patients with other gastrointestinal diseases, there are few that focus on CDCs or BA. Generally, authors encourage medical record transmission from pediatric to adult providers, ensuring accuracy of information and compliance with treatment plans. Patients with CDCs are at risk for developing biliary malignancies, cholangitis, and anastomotic strictures after resection. Patients with BA develop progressive liver failure, necessitating transplantation. There are no consensus guidelines regarding timing of follow up for these patients. Based on the best available evidence, we propose a schema for long‐term surveillance.  相似文献   
4.
Background: Guidelines recommend primary prophylactic use of colony-stimulating factor (PP-CSF) when risk of febrile neutropenia (FN) – based on chemotherapy and patient risk factors – is high. Whether and how PP-CSF use may have changed over time (e.g. due to guideline revisions, increasing use of myelosuppressive regimens, controversy regarding inappropriate CSF use), and whether there has been a concomitant change in the incidence of FN, is unknown.

Methods: A retrospective cohort design and data from two US healthcare claims repositories were employed. The study population included patients who had non-metastatic cancer of the breast, colon/rectum, lung or ovaries, or non-Hodgkin’s lymphoma (NHL), and who received myelosuppressive chemotherapy regimens with an intermediate/high risk for FN. For each patient, the first cycle of the first course was characterized in terms of PP-CSF use and FN episodes. Crude incidence proportions for PP-CSF and FN during the first cycle were estimated by calendar quarter (2010–2016); multivariable logistic regression models were used to estimate quarter-specific adjusted mean probabilities of FN by PP-CSF use.

Results: The study population totaled 142,730 patients with breast cancer (61%), colorectal cancer (14%), NHL (11%), ovarian cancer (10%) or lung cancer (5%). PP-CSF use increased from 52% in 1Q2010 to 58% in 4Q2016; pegfilgrastim was the most commonly used agent (>96% across quarters). PP-CSF administration on the same day as chemotherapy ranged from 8 to 11% until 1Q2015, and increased to 64% by 4Q2016. Adjusted incidence proportions for FN in the first chemotherapy cycle ranged from 2.7% (95% CI: 2.3–3.0) to 3.7% (95% CI: 3.1–4.3) among those who did not receive PP-CSF, and was 2.6% (95% CI: 2.5–2.7) across quarters among those who received PP-CSF.

Conclusions: Although the use of PP-CSF is commonplace in current US clinical practice, underutilization in cancer patients receiving chemotherapy regimens with an intermediate/high risk for FN may still be an issue. Use of same-day PP-CSF increased markedly from the end of 2015, although this finding reflects (at least in part) increased uptake of pegfilgrastim delivered via an on-body injector as well as the recent change in clinical practice guidelines. Overall, patients receiving PP-CSF appear to have a lower risk of FN during the first cycle of chemotherapy.  相似文献   

5.
6.
7.
Arachidonic acid metabolites (eicosanoids) have major effects on bone but their role is unclear. Many are known to stimulate bone resorption in organ culture, but paradoxically, previous work has suggested that at least some of them act as direct inhibitors of osteoclastic function. In an attempt to clarify the role of eicosanoids in bone physiology, we have defined the duration of action and relative potencies of prostaglandin (PG) E1 and E2 and have extended the range of eicosanoids tested on isolated osteoclasts. We have found that PGE1 and PGE2 inhibited bone resorption by isolated osteoclasts for at least 6 h. Inhibition was followed by recovery to control, not supranormal levels. Bone resorption was inhibited in the range 10(-5)-10(-9) M for PGE1 and PGE2, and the rank order as resorption inhibitors was PGE1 greater than 6-keto PGE1 greater than PGE2 greater than PGA2 greater than PGB2. None of the products of lipoxygenase metabolism showed a significant direct effect. The effects of PGE1 and PGE2 were not antagonistic. Prostaglandin production does not seem to be implicated as a second messenger for the action of calcitonin. Although inhibition of osteoclasts by PGs was less prolonged than that observed in the presence of calcitonin, the sensitivity of osteoclasts to inhibition by PGs, and the duration of the effect without subsequent direct stimulation, suggests that inhibition of osteoclastic resorption is a major physiological role of PG production in bone.  相似文献   
8.
The isolated perfused working rat heart model of cardiopulmonary bypass was used to assess whether (a) allopurinol pretreatment enhances resistance to normothermic (30 min) or hypothermic (4 h) ischemia; (b) addition of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) to cardioplegic and/or reperfusion solutions are protective; (c) any protective effects are additive. With normothermic ischemia, allopurinol pretreatment improved recovery of aortic flow from its control value of 25 +/- 3% to 48 +/- 6% (P less than 0.05). Similarly, SOD plus CAT used during both ischemia and reperfusion improved recovery of aortic flow from a control value of 28 +/- 4% to 48 +/- 6% (P less than 0.05). However, various combinations of the two types of intervention afforded no additive protection. Under hypothermic (21 degrees C) conditions, allopurinol pretreatment was not effective, whereas SOD and CAT added during ischemia and reperfusion improved recovery of aortic flow from its control value of 53 +/- 4% to 69 +/- 5% (P less than 0.05). This value was similar to allopurinol pretreatment and SOD plus CAT added during ischemia and reperfusion (69 +/- 6%: P less than 0.05). These results provide further evidence that reperfusion-induced free radical formation may adversely affect postischemic recovery of function. The absence of an additive effect suggests a common mechanism of action, which is likely to involve the free radical-generating enzyme xanthine oxidase; however, other mechanisms may exist. Our results further support the use of antifree radical intervention in conjunction with cardioplegia to protect the heart during ischemia and reperfusion.  相似文献   
9.
10.
The efficacy of cilofungin (LY121019) for aortic valve endocarditis caused by Candida albicans in rabbits was studied. Vegetation titers were similar for cilofungin-treated and untreated rabbits. No rabbit survived beyond 5 days in either group. All rabbits given amphotericin B survived, and titers were reduced. Cilofungin was ineffective in this model.  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