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   30736篇
  免费   1754篇
  国内免费   105篇
耳鼻咽喉   279篇
儿科学   760篇
妇产科学   683篇
基础医学   3819篇
口腔科学   923篇
临床医学   3194篇
内科学   6110篇
皮肤病学   401篇
神经病学   2943篇
特种医学   1212篇
外科学   3447篇
综合类   312篇
一般理论   31篇
预防医学   3038篇
眼科学   750篇
药学   2495篇
中国医学   44篇
肿瘤学   2154篇
  2023年   112篇
  2022年   171篇
  2021年   395篇
  2020年   267篇
  2019年   450篇
  2018年   512篇
  2017年   414篇
  2016年   433篇
  2015年   530篇
  2014年   823篇
  2013年   1364篇
  2012年   1977篇
  2011年   2116篇
  2010年   1160篇
  2009年   1185篇
  2008年   2046篇
  2007年   2275篇
  2006年   2276篇
  2005年   2175篇
  2004年   2149篇
  2003年   2032篇
  2002年   1993篇
  2001年   290篇
  2000年   186篇
  1999年   313篇
  1998年   446篇
  1997年   365篇
  1996年   343篇
  1995年   297篇
  1994年   280篇
  1993年   263篇
  1992年   161篇
  1991年   181篇
  1990年   149篇
  1989年   141篇
  1988年   134篇
  1987年   128篇
  1986年   111篇
  1985年   158篇
  1984年   215篇
  1983年   164篇
  1982年   243篇
  1981年   244篇
  1980年   232篇
  1979年   110篇
  1978年   109篇
  1977年   107篇
  1976年   82篇
  1975年   70篇
  1974年   63篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
BACKGROUND CONTEXT: Prior studies have documented an increased complication rate in diabetics treated by lumbar decompression. Despite the assumption that this risk would be exacerbated in larger fusion procedures, a recent study found no such increased risk. PURPOSE: To clarify the perioperative risk for patients with diabetes mellitus undergoing instrumented lumbar fusion as compared with controls. To identify differences, if any exist, between patients with insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes (NIDDM). STUDY DESIGN/SETTING: This is a retrospective case-control study designed to examine the risk of perioperative complications in patients with diabetes mellitus treated by lumbar instrumentation and fusion. This study analyzed 94 diabetic patients and 43 controls treated by posterior lumbar instrumentation and fusion. Outcome was assessed based on the occurrence of perioperative complications. Complications were classified as major or minor. METHODS: Hospital and office records were reviewed for 94 diabetics (51 NIDDM, 43 IDDM) and 43 controls matched for age, sex and procedure with the IDDM group. The groups were compared for demographic characteristics, surgical data, perioperative complications and fusion rate. RESULTS: The NIDDM, IDDM and control groups were equivalent with regard to age, gender, nicotine use, fusion levels, operative time and estimated blood loss. There was a significant difference in complication rate between the NIDDM (53%) and IDDM (56%) groups versus controls (21%). There was a significant increase in complications with multilevel fusion in all groups and with increased operative time in the IDDM group. There was a significantly greater nonunion rate in the NIDDM (22%) and IDDM (26%) groups as compared with controls (5%). CONCLUSIONS: Patients with both IDDM and NIDDM have a significantly increased risk of perioperative complications as compared with controls when treated by lumbar instrumentation and fusion.  相似文献   
992.
BACKGROUND: The impact of moderate alcohol consumption on renal function has important public health implications given the high prevalence of alcohol use. Experimentally, alcohol may adversely affect renal function, but clinical data are limited and no large, prospective studies have examined this issue. METHODS: In a prospective study of 1658 nurses enrolled in the Nurses' Health Study, we sought to determine if there was an association between moderate alcohol consumption and rate of decline in renal function. Daily alcohol intake was measured in 1990, 1994 and 1998 using a detailed questionnaire. Maximum daily alcohol intake was measured in 1988. Creatinine, measured from blood samples provided in 1989 and 2000, was used to estimate glomerular filtration rate (GFR) and creatinine clearance (CCr). RESULTS: Compared to individuals with no alcohol intake, the odds ratios (ORs) for developing a >or=25% estimated GFR decline were: 0.98 (95% CI: 0.72-1.32) for 0.1-4.9 g/day, 0.83 (95% CI: 0.56-1.21) for 5-14.9 g/day and 0.81 (95% CI: 0.50-1.31) for 15-59.9 g/day. For women with hypertension (n = 726), the ORs for a >or=25% estimated GFR decline were: 0.98 (95% CI: 0.53-1.21) for 0.1-4.9 g/day, 0.62 (95% CI: 0.34-1.12) for 5-14.9 g/day and 0.53 (95% CI: 0.25-1.12) for 15-59.9 g/day. CONCLUSIONS: Moderate alcohol consumption had no substantial adverse effect on renal function in women over an 11 year follow-up period.  相似文献   
993.
BACKGROUND: The AERx Pain Management System (Aradigm Corporation, Hayward, CA) is a novel pulmonary delivery system for the systemic administration of morphine. The authors compared the relative analgesic efficacy and safety of the AERx Pain Management System with those of placebo and intravenous morphine in an orthopedic postsurgical pain model. METHODS: Eighty-nine male and female PS-1 to PS-3 patients underwent standardized bunionectomy surgery and received multiple doses of inhaled or intravenous placebo, inhaled morphine (one inhalation [2.2 mg] or three inhalations [6.6 mg]), or intravenous morphine (4 mg) in a blinded fashion. Open-label rescue morphine (2 mg) was also available as needed. Pain intensity, pain relief, and time to pain relief were measured after the first dose. Global evaluation, morphine consumption, vital signs, and adverse events were monitored for 8 h after treatment. Blinded study personnel performed all treatment administrations and pain assessments. RESULTS: Three inhalations of morphine and 4 mg intravenous morphine provided comparable single- and multiple-dose analgesia. One inhalation of morphine was statistically indistinguishable from placebo. Three inhalations of morphine and 4 mg intravenous morphine both consistently demonstrated significantly greater analgesic efficacy than did placebo and one inhalation of morphine. CONCLUSIONS: Comparable analgesic efficacy was demonstrated between a carefully matched dose of inhaled and intravenous morphine in a postsurgical pain model.  相似文献   
994.
Background: Australia has the highest incidence of cutaneous squamous cell carcinoma in the world. The majority of lesions occur in the head and neck with metastases to the parotid gland lymph nodes reflecting an uncommon, but aggressive, manifestation. Parotidectomy ± neck dissection followed by adjuvant radiotherapy should be considered as best practice. Methods: Between 1983 and 2000, seventy-four patients were treated for metastatic cutaneous squamous cell carcinoma to the parotid with surgery and adjuvant radiotherapy at Westmead Hospital, Sydney. Relevant data were extracted from patient files and a prospectively maintained database. Patterns of relapse and outcome were analysed. Results: Median age at diagnosis was 65 years (34−93 years) in 63 men and 11 women. Median follow-up duration was 41 months (12−188 months). All patients underwent parotidectomy with 52 undergoing a simultaneous neck dissection. Twelve patients required sacrifice of the facial nerve (4) or one or more branches (8). All received adjuvant radiotherapy to the parotid region with 56 also receiving radiotherapy to the ipsilateral neck. Despite treatment, 24% developed locoregional recurrence, with a median time to relapse of 7.5 months. The most common site for recurrence was the treated parotid region and upper neck. Most relapsed patients died. No variable independently predicted for locoregional recurrence on multivariate analysis. The 5-year absolute and cause-specific survival rates were 58% and 72%, respectively. Conclusion: Parotid gland lymph node metastases from cutaneous squamous cell carcinoma are associated with a high rate of recurrence and cause-specific mortality despite current best practice (surgery and high dose adjuvant radiotherapy). The role of more aggressive surgery, altered fractionation or chemotherapy to enhance locoregional control remains unclear.  相似文献   
995.
996.
Biliary strictures after live donor liver transplantation (LDLT) are frequent and difficult to manage. The outcomes of surgical correction of biliary anastomotic complications remain unclear. Clinical outcomes of patients requiring surgical revision of their biliary anastomosis following LDLT were analyzed. Of 296 consecutive right lobe LDLTs, approximately 21% of patients developed biliary strictures. Of these patients, twelve required surgical revision of a biliary anastomotic stricture. For patients who had operative repair, the average time from transplantation to stricture diagnosis was 7.6 months. Mean time to surgical correction was 8.2 months from the time of stricture diagnosis. Eight of 12 (67%) patients no longer require any intervention with a mean follow-up of 43.7 months. Two of 12 patients require intermittent medical treatment for presumed cholangitis, but have not required biliary interventions. Two patients have required chronic PTC catheter drainage. The 30-day postoperative morbidity was 58%, with four serious (Grade 3) complications occurring in three patients. Early stricture repair (<6 months from diagnosis of stricture) and younger donor grafts were associated with better surgical outcomes. Timely surgical correction of biliary strictures is successful and durable in appropriately selected patients. However, operative repair is associated with significant postoperative morbidity.  相似文献   
997.
Carbon-11-labeled tricyclic necroptosis inhibitors were first designed and synthesized as new potential PET agents for imaging of tumor necrosis factor α (TNF-α). The target tracers were prepared by O-[11C]methylation of their corresponding precursors using [11C]CH3OTf under basic conditions and isolated by a simplified SPE method in 50–60% radiochemical yields based on [11C]CO2 and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15–20 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111–185 GBq/μmol.  相似文献   
998.
Despite their large size, antibodies (Abs) are suitable carriers to deliver systemic radiotherapy, often molecular image-based, for lymphoma and leukemia. Lym-1 Ab has proven to be an effective radioisotope carrier, even in small amounts, for targeting human leukocyte antigen DR (HLA-DR), a surface membrane protein overexpressed on B-cell lymphoma. Pairs of molecules (referred to as ligands), shown by computational and experimental methods to bind to each of 2 sites within the Lym-1 epitopic region, have been linked to generate small (<2 kDa) molecules (referred to as selective high-affinity ligands [SHALs]) to mimic the targeting properties of Lym-1 Ab. METHODS: A lysine-polyethylene glycol (PEG) backbone was used to synthetically link 2 of the following ligands: deoxycholate, 5-leuenkephalin, triiodothyronine, thyronine, dabsyl-L-valine, and N-benzoyl-L-arginyl-4-amino-benzoic acid to generate a series of 13 bidentate SHALs with a biotin or 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid (DOTA) chelate attached to the linker. These SHALs have been assessed for their selectivity in binding to HLA-DR10-expressing cells and for their pharmacokinetics and tissue biodistribution in mice. Biotinylated versions of these SHALs discriminated cell lines positive for HLA-DR10 expression with near-nanomolar affinity. The DOTA versions of 4 SHALs were labeled with (111)In for pharmacokinetic studies in mice with HLA-DR10-expressing malignant Raji xenografts. RESULTS: The bidentate, biotinylated, and DOTA-SHALs were synthesized in high-purity, multimilligram amounts. Mean radiochemical and product yields and purities were 90%, 75%, and 90% at mean specific activities of 3.9 MBq/microg (105 microCi/microg) for the (111)In-labeled SHALs. As expected, rapid blood clearance and tumor targeting were observed. The pharmacokinetics of the SHALs was influenced by the component ligands. Biliary clearance, kidney localization, and serum receptor binding contributed to less favorable tumor targeting. CONCLUSION: A series of SHALs was readily synthesized in multimilligram amounts and showed the expected selective binding in vitro. Better selection of the SHAL components should provide second-generation SHALs with improved properties to fulfill the substantial potential of these novel molecular carriers for targeting.  相似文献   
999.
In the study of asthma, a vital role is played by mouse models, because knockout or transgenic methods can be used to alter disease pathways and identify therapeutic targets that affect lung function. Assessment of lung function in rodents by available methods is insensitive because these techniques lack regional specificity. A more sensitive method for evaluating lung function in human asthma patients uses hyperpolarized (HP) (3)He MRI before and after bronchoconstriction induced by methacholine (MCh). We now report the ability to perform such (3)He imaging of MCh response in mice, where voxels must be approximately 3000 times smaller than in humans and (3)He diffusion becomes an impediment to resolving the airways. We show three-dimensional (3D) images that reveal airway structure down to the fifth branching and visualize ventilation at a resolution of 125 x 125 x 1000 microm(3). Images of ovalbumin (OVA)-sensitized mice acquired after MCh show both airway closure and ventilation loss. To also observe the MCh response in naive mice, we developed a non-slice-selective 2D protocol with 187 x 187 microm(2) resolution that was fast enough to record the MCh response and recovery with 12-s temporal resolution. The extension of (3)He MRI to mouse models should make it a valuable translational tool in asthma research.  相似文献   
1000.
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