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   4831篇
  免费   352篇
  国内免费   22篇
耳鼻咽喉   18篇
儿科学   99篇
妇产科学   148篇
基础医学   791篇
口腔科学   60篇
临床医学   517篇
内科学   943篇
皮肤病学   91篇
神经病学   572篇
特种医学   178篇
外科学   455篇
综合类   35篇
一般理论   5篇
预防医学   435篇
眼科学   60篇
药学   319篇
中国医学   6篇
肿瘤学   473篇
  2023年   45篇
  2022年   90篇
  2021年   157篇
  2020年   103篇
  2019年   108篇
  2018年   127篇
  2017年   123篇
  2016年   169篇
  2015年   179篇
  2014年   220篇
  2013年   267篇
  2012年   420篇
  2011年   459篇
  2010年   214篇
  2009年   201篇
  2008年   322篇
  2007年   305篇
  2006年   295篇
  2005年   288篇
  2004年   230篇
  2003年   214篇
  2002年   175篇
  2001年   50篇
  2000年   55篇
  1999年   51篇
  1998年   27篇
  1997年   30篇
  1996年   16篇
  1995年   8篇
  1994年   8篇
  1993年   7篇
  1992年   13篇
  1991年   15篇
  1990年   19篇
  1989年   18篇
  1988年   14篇
  1987年   8篇
  1986年   13篇
  1985年   8篇
  1984年   5篇
  1983年   11篇
  1980年   7篇
  1979年   15篇
  1978年   7篇
  1977年   8篇
  1976年   9篇
  1971年   5篇
  1970年   5篇
  1969年   9篇
  1961年   4篇
排序方式: 共有5205条查询结果,搜索用时 875 毫秒
1.
Harinakshi Sanikini  David C. Muller  Marisa Sophiea  Sabina Rinaldi  Antonio Agudo  Eric J. Duell  Elisabete Weiderpass  Kim Overvad  Anne Tjønneland  Jytte Halkjær  Marie-Christine Boutron-Ruault  Franck Carbonnel  Iris Cervenka  Heiner Boeing  Rudolf Kaaks  Tilman Kühn  Antonia Trichopoulou  Georgia Martimianaki  Anna Karakatsani  Valeria Pala  Domenico Palli  Amalia Mattiello  Rosario Tumino  Carlotta Sacerdote  Guri Skeie  Charlotta Rylander  María-Dolores Chirlaque López  Maria-Jose Sánchez  Eva Ardanaz  Sara Regnér  Tanja Stocks  Bas Bueno-de-Mesquita  Roel C.H. Vermeulen  Dagfinn Aune  Tammy Y.N. Tong  Nathalie Kliemann  Neil Murphy  Marc Chadeau-Hyam  Marc J. Gunter  Amanda J. Cross 《International journal of cancer. Journal international du cancer》2020,146(4):929-942
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox models. During a mean follow-up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric noncardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI ≥30 vs. 18.5–25 kg/m2: HR = 1.94, 95% CI: 1.25–3.03) and women (HR = 2.66, 95% CI: 1.15–6.19); however, adjustment for waist-to-hip ratio (WHR) attenuated these associations. After mutual adjustment for BMI and HC, respectively, WHR and waist circumference (WC) were associated with EA in men (HR = 3.47, 95% CI: 1.99–6.06 for WHR >0.96 vs. <0.91; HR = 2.67, 95% CI: 1.52–4.72 for WC >98 vs. <90 cm) and women (HR = 4.40, 95% CI: 1.35–14.33 for WHR >0.82 vs. <0.76; HR = 5.67, 95% CI: 1.76–18.26 for WC >84 vs. <74 cm). WHR was also positively associated with GC in women, and WC was positively associated with GC in men. Inverse associations were observed between parity and EA (HR = 0.38, 95% CI: 0.14–0.99; >2 vs. 0) and age at first pregnancy and GNC (HR = 0.54, 95% CI: 0.32–0.91; >26 vs. <22 years); whereas bilateral ovariectomy was positively associated with GNC (HR = 1.87, 95% CI: 1.04–3.36). These findings support a role for hormonal pathways in upper gastrointestinal cancers.  相似文献   
2.
3.
A feasibility study was undertaken to evaluate laboratory phlebotomists performing bedside glucose monitoring (BGM) over a 3-month period on a medical and surgical floor. Specific questions included: feasibility of providing testing on a 24-h basis, accuracy, appropriate utilization, effect on patient care, and an analysis of cost. In all, 1975 tests were performed on 114 patients. BGM results were within 15% of the laboratory's result 97% of the time. Patient and physician satisfaction was high. Although the cost of BGM is slightly higher than a laboratory glucose test, its use appeared to reduce the length of hospital stay by 0.47 days. Practical information on initiating a highly successful BGM program is provided.  相似文献   
4.
Abstract:  The identification of tumor-specific proteins located at the plasma membrane is hampered by numerous methodological pitfalls many of which are associated with the post-translational modification of such proteins. Here, we present a new combination of detergent fractionation of cells and of subtractive suppression hybridization (SSH) to gain overexpressed genes coding for membrane-associated or secreted proteins. Fractionation of subcellular components by digitonin allowed sequestering mRNA of the rough Endoplasmatic reticulum and thereby increasing the percentage of sequences coding for membrane-bound proteins. Fractionated mRNAs from the cutaneous T-cell lymphoma (CTCL) cell line HuT78 and from normal peripheral blood monocytes were used for SSH leading to the enrichment of sequences overexpressed in the tumor cells. We identified some 21 overexpressed genes, among them are GPR137B, FAM62A, NOMO1, HSP90, SLIT1, IBP2, CLIF, IRAK and ARC. mRNA expression was tested for selected genes in CTCL cell lines, skin specimens and peripheral blood samples from CTCL patients and healthy donors. Several of the detected sequences are clearly related to cancer, but have not yet been associated with CTCL. qPCR confirmed an enrichment of these mRNAs in the rough endoplasmic reticulum fraction. RT-PCR confirmed the expression of these genes in skin specimens and peripheral blood of CTCL patients. Western blotting verified protein expression of HSP90 and IBP2 in HuT78. GPR137B could be detected by immunohistology in HuT78 and in keratinocytes of dysplastic epidermis, but also in sweat glands of healthy skin. In summary, we developed a new technique, which allows identifying overexpressed genes coding preferentially for membrane-associated proteins.  相似文献   
5.
After liver transplantation for hepatitis-B-related diseases, patients currently receive lifelong treatment with hepatitis B immunoglobulin to prevent endogenous reinfection with hepatitis B virus (HBV). Active immunization with hepatitis B vaccine would be a preferable alternative; however, most attempts to immunize these patients with standard vaccine have failed. A recent study with a new adjuvanted hepatitis B vaccine was exceptionally successful, leading to a high-titered long-lasting antibody response in 80% of all vaccinees. To identify the immunological mechanisms behind these unexpected results, the successfully vaccinated participants were tested for hepatitis B surface antigen (HBsAg)-specific T and B cells, and their cellular responses to revaccination with conventional vaccine were studied. HBsAg-specific CD4(+) T lymphocytes could be detected in 13 of 16 patients after immunization with the new vaccine. Unexpectedly, these T cells produced almost exclusively interleukin (IL)-10 and had a CD4(+)/CD25(+) phenotype. They were functionally active, suppressing cytokine secretion in HBsAg-specific (Th1) cells, thus representing antigen-specific regulatory T cells (T(Reg)). Following a booster dose with conventional vaccine 22-31 months after completion of the initial vaccination series, the T-cell pattern in the revaccinated individuals changed substantially: 7 days after revaccination 9 of 11 individuals showed a switch to a Th1-type immune response with HBsAg-specific T cells secreting IL-2, interferon gamma and tumor necrosis factor alpha as observed in healthy controls. Four weeks after the booster, 4 patients still showed a Th1-type cytokine pattern, whereas in 5 patients only IL-10-secreting cells were detectable. After 1 year, in 3 of 4 revaccinated individuals only IL-10-secreting cells could be found, whereas the specific T cells of the fourth patient still showed a Th1-type of response. HBsAg-specific T(Reg) cells could be demonstrated in HBV-positive liver transplant recipients successfully immunized with a new adjuvanted vaccine. Revaccination led to immediate disappearance of the these cells and the appearance of HBsAg-specific T cells with a Th1-type cytokine profile, which in most cases were replaced by the IL-10-secreting regulatory cells during the following months. The specific induction of T(Reg) cells could contribute to the poor response of liver transplant recipients to conventional vaccine. In conclusion,, for successful vaccination of these patients, a vaccine with a strong inhibitory effect on T(Reg) cells would be desirable.  相似文献   
6.
Background: Postoperative nausea and vomiting (PONV) is a distressing problem after strabismus surgery. An inspired oxygen fraction has been reported to decrease PONV in patients after colon resection and to be more effective than ondansetron after gynecologic laparoscopy. Therefore, in a randomized, prospective, placebo-controlled study, the authors tested whether an inspired oxygen fraction of 0.8 decreases PONV in patients undergoing strabismus surgery and whether oxygen is more effective than ondansetron.

Methods: With approval of the authors' institutional review board, 210 patients were randomly assigned to receive one of three treatments: (1) 30% inspired oxygen in air plus intravenous administration of saline, (2) 80% inspired oxygen in air plus intravenous administration of saline, or (3) 30% inspired oxygen in air plus 75 [mu]g/kg ondansetron intravenously during induction. General anesthesia was standardized and included etomidate, alfentanil, and mivacurium for induction and sevoflurane for maintenance. PONV was evaluated 6 and 24 h postoperatively by an investigator unaware of treatment assignment.

Results: Overall postoperative incidence of nausea and vomiting was 41% for inspired oxygen fraction of 0.3 plus placebo, 38% for inspired oxygen fraction of 0.8 plus placebo, and 28% for inspired oxygen fraction of 0.3 plus ondansetron, respectively (P = 0.279). Therefore, there was no statistically significant difference of PONV incidence among groups.  相似文献   

7.
Using the whole-cell configuration of the patch clamp technique, calcium-activated potassium currents (IK,Ca) were investigated in ramified murine brain macrophages. In order to induce IK,Ca the intracellular concentration of nominal free Ca2+ was adjusted to 1μM. The Ca2+-activated K+ current of brain macrophages did not show any voltage dependence at test potentials between –120 and +30mV. A tenfold change in extracellular K+ concentration shifted the reversal potential of IK,Ca by 51mV. The bee venom toxin apamin applied at concentrations of up to 1μM did not affect IK,Ca. Ca2+-activated K+ currents of ramified brain macrophages were highly sensitive to extracellularly applied charybdotoxin (CTX). The half-maximal effective concentration of CTX was calculated to be 4.3nM. In contrast to CTX, the scorpion toxin kaliotoxin did not inhibit IK,Ca at concentrations between 1 and 50nM. Tetraethylammonium (TEA) blocked 8.0% of IK,Ca at a concentration of 1mM, whereas 31.4% of current was blocked by 10mM TEA. Several inorganic polyvalent cations were tested at a concentration of 2mM for their ability to block IK,Ca. La3+ reduced IK,Ca by 72.8%, whereas Cd2+ decreased IK,Ca by 17.4%; in contrast, Ni2+ did not have any effect on IK,Ca. Ba2+ applied at a concentration of 1mM reduced IK,Ca voltage-dependently at hyperpolarizing potentials. Received: 17 January / Accepted: 5 May 1997  相似文献   
8.
9.
The objective of this study was to explore whether the items from a specific outcome measure, that is, Disabilities of the Arm, Shoulder, and Hand (DASH), for quantifying limb symptoms and functions in musculoskeletal disorders fit into the framework of the International Classification of Functioning, Disability and Health (ICF). All DASH items were compared to the ICF according to eight linking rules. Two groups of researchers performed the linking independently, and the results were compared by correlation. The 30 DASH items and four items from the optional modules were linked to 63 ICF categories and 11 chapters: 15 categories belong to the ICF body functions component and 48 to the activities and participation component. There were no items coded under the components body structure or environmental factors. Kappa index showed an agreement of 0.73 (p<0.001). The results showed that the content of the DASH does link well with the ICF framework. Clinicians and researchers must attend to the fact that certain domains and categories from the ICF are not covered by the DASH. Limitations of the instrument may be overcome by simultaneously using other instruments that address the intended content.  相似文献   
10.
The effects of recombinant human erythropoietin (rhEPO, RecormonR, CAS 122312-54-3) on the differential leucocyte counts and platelets of rabbits were investigated after the repeated application of a single dose of rhEPO. Therefore, 150 IU rhEPO (n = 5), 300 IU rhEPO (n = 6), or 600 IU rhEPO (n = 5) per animal was injected once on three separate occasions with an interval of 5–6 weeks between each injection. Six animals were used to study the potential effect of the solvent alone.rhEPO showed a significant time effect on the differential leucocyte counts and platelets of rabbits. The decrease in total white blood cells count (WBC) on the third, fourth and sixth day after rhEPO administration was due to a decrease in lymphocytes. These results support the hypothesis that the enhanced demand of one cell line leads to a down-modulation of the production of other cell line(s).  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