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   96801篇
  免费   6594篇
  国内免费   510篇
耳鼻咽喉   1207篇
儿科学   2286篇
妇产科学   1386篇
基础医学   12429篇
口腔科学   2310篇
临床医学   9533篇
内科学   21323篇
皮肤病学   1517篇
神经病学   9227篇
特种医学   3950篇
外国民族医学   1篇
外科学   16056篇
综合类   801篇
一般理论   194篇
预防医学   6550篇
眼科学   1833篇
药学   5857篇
中国医学   139篇
肿瘤学   7306篇
  2023年   864篇
  2022年   1498篇
  2021年   3285篇
  2020年   1820篇
  2019年   2822篇
  2018年   3317篇
  2017年   2350篇
  2016年   2541篇
  2015年   2854篇
  2014年   3943篇
  2013年   5045篇
  2012年   7638篇
  2011年   7739篇
  2010年   4266篇
  2009年   3702篇
  2008年   6369篇
  2007年   6140篇
  2006年   5948篇
  2005年   5864篇
  2004年   5280篇
  2003年   4844篇
  2002年   4350篇
  2001年   616篇
  2000年   487篇
  1999年   686篇
  1998年   891篇
  1997年   710篇
  1996年   574篇
  1995年   565篇
  1994年   451篇
  1993年   459篇
  1992年   366篇
  1991年   324篇
  1990年   296篇
  1989年   288篇
  1988年   291篇
  1987年   265篇
  1986年   289篇
  1985年   292篇
  1984年   357篇
  1983年   311篇
  1982年   339篇
  1981年   339篇
  1980年   264篇
  1979年   151篇
  1978年   193篇
  1977年   181篇
  1976年   130篇
  1975年   134篇
  1974年   132篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background

In infants with gastroschisis antenatal closure of the umbilical defect results in a proximal atresia with ischemia and/or volvulus of the extracorporeal midgut. It has been described as “closed gastroschisis” or “vanishing midgut.”

Methods

A 10-year review of 219 gastroschisis patients identified 10 infants with this rare complication.

Results

In these 10 infants, the extracorporeal midgut was invariably matted and fibrosed. In 3 cases, the midgut had completely “vanished.” In the remaining 7 cases, the remnant midgut was surgically reduced into the abdominal cavity with care not to compromise the diminutive vascular pedicle. Abdominal exploration was performed several weeks later to reestablish bowel continuity; 4 required an ostomy and 2 underwent a serial transverse enteroplasty. Mean residual length of salvaged small bowel was 79 cm with retention of the distal half of the colon. Eight infants survived the initial hospitalization, with a mean length of stay of 121 days and mean hospital charge of $287,094. Six of the 7 long-term survivors have been completely weaned off total parenteral nutrition.

Conclusion

A nihilistic attitude toward infants with closed gastroschisis may not be uniformly supported because in the majority of these infants' long-term independence from total parenteral nutrition was achieved.  相似文献   
992.

Purpose

The current management of osteosarcoma (OS) entails an aggressive preoperative and postoperative chemotherapeutic regimen with limb salvage surgery. Despite these efforts, relapse-free survival is less than 60% in patients with classic OS, whereas most patients relapse with pulmonary metastases. In these studies, we sought to prevent the establishment of pulmonary metastases from OS with a single oral dose of SalpIL2.

Methods

Mice were administered attenuated Salmonella typhimurium with (SalpIL2) and without a gene for human interleukin 2 (Sal-NG) 7 days before challenge with 2 × 105 OS cells via tail vein. Three weeks after injection, mice were harvested for splenic lymphocytes and tumor enumeration.

Results

Prophylaxis with attenuated SalpIL2 significantly reduces pulmonary metastases in number and volume (P < .0001 and P < .0001) with respect to saline controls. Furthermore, splenic natural killer cell populations were increased 396% with SalpIL2 (P < .0007) and 426% with Sal-NG (P < .0003) compared to nontreated groups.

Conclusions

Host natural killer response is greatly amplified and maybe partially responsible for the effective immune response against the formation of pulmonary metastases. A single oral dose of SalpIL2 may be a novel form of adjuvant therapy for patients after early detection of primary OS.  相似文献   
993.
994.
995.
996.
Hinged elbow external fixation for severe elbow contracture   总被引:2,自引:0,他引:2  
BACKGROUND: When it was first introduced, it was hoped that hinged external fixation with a built-in gear mechanism for applying passive motion and static progressive stretch by turning a dial would improve the arc of ulnohumeral motion, by gradually stretching contracted muscles, after open release of a severe elbow contracture. METHODS: Forty-two patients were evaluated at an average of thirty-nine months after operative release of a severe posttraumatic elbow contracture (defined as < or =40 degrees of motion). Twenty-three patients had been treated, during the early part of the study, with a hinged external fixator that incorporated a worm gear to apply static progressive stretch postoperatively. These patients were compared with nineteen patients who had been treated without hinged external fixation during the later part of the study, when the hinge was used less frequently. The operative techniques did not otherwise change during the study period. Demographic and injury characteristics as well as associated problems were comparable between the two groups. RESULTS: The average gain in the range of motion after the index procedure was 89 degrees in the patients treated with a hinge and 78 degrees in those treated without a hinge, an insignificant difference with the numbers available (p = 0.175). Complications associated with use of the hinge included five pin-track infections, one case of pin-track osteomyelitis, one ulnar fracture through a pin site, two broken Schanz screws, and two cases of irritation of the ulnar nerve. CONCLUSIONS: Open release of a severe elbow contracture results in a substantial gain in motion, with or without hinged elbow fixation. The slightly greater improvement in motion provided by the hinge does not justify the associated increase in risk, expense, and complications.  相似文献   
997.
BACKGROUND: Interleukin (IL)-12-producing dendritic cells (IL-12+DC) polarize T helper (Th) differentiation toward Th1, whereas IL-10+DC induce Th differentiation toward Th2. We investigated DC and plasma cytokine patterns early and late after transplantation. METHODS: Twenty-five hospitalized renal-transplant recipients without acute rejection or infection early (<40 days) posttransplant, 32 symptom-free outpatients with long-term functioning transplants (2,762+/-2,423 days posttransplant), and 17 healthy controls were studied. The intracellular production of IL-12 and IL-10 in CD11c+ CD83+ CD40+ DC was measured in freshly obtained whole blood using four-color fluorescence flow cytometry. In addition, plasma cytokine levels were investigated. RESULTS: Early and late posttransplant patients had significantly lower proportions of IL-12+DC (early: P=0.001; late: P=0.034) and lower ratios of IL-12+/IL-10+DC (early: P=0.0001; late: P<0.0001) than healthy controls. IL-10+DC (P=0.0004) and IL-12+DC (P=0.002) increased with time posttransplant in association with dose reductions of cyclosporine (IL-10+DC: P=0.003; IL-12+DC: P=0.005), methylprednisolone (IL-10+DC: P<0.0001; IL-12+DC: P=0.001) and mycophenolate mofetil (IL-10+DC: P<0.0001; IL-12+DC: P=0.004). Both IL-10+DC and IL-12+DC were associated with low plasma IL-10 (IL-10+DC: P=0.010; IL-12+DC: P=0.011) and high plasma IL-6 (IL-10+DC: P=0.001; IL-12+DC: P=0.009). IL-10+DC were also associated with high plasma levels of IL-3 (P=0.003), interferon (IFN)-gamma (P=0.014), and IL-2 (P=0.058). CONCLUSION: IL-10+DC and IL-12+DC in peripheral blood are associated with time after transplantation and dosage of immunosuppression. IL-10+DC dominate late posttransplant in the presence of Th1 plasma cytokines (high IFN-gamma and IL-2), high IL-3, and low IL-10. These findings could be a reflection of immunoregulatory processes favoring long-term allograft acceptance.  相似文献   
998.
BACKGROUND: Cytolytic induction therapy with anti-thymocyte globulin (ATG) should induce effective immunosuppression, with a low rate of rejection in the initial phase after heart transplantation. Induction therapy with ATG allows post-operative renal recovery without the negative effects of highly nephrotoxic cyclosporine levels. An increased rate of infection is a common problem, however, and has been associated with "over-immunosuppression" early after transplantation. Therefore, we investigated whether reduced T-cell-adapted ATG induction therapy could be performed without increasing the risk of graft loss by rejection and whether reductions in infection rates and costs are possible. METHODS: Between March 1999 and December 2002, T-cell-adapted ATG induction therapy with ATG (Sangstat) (1.5 mg/kg) was given to 62 heart transplant recipients (study group) starting on post-operative Days 1 to 6. T-lymphocyte sub-populations were screened daily using flow cytometry. If total lymphocytes were <100/microl (reference 1,300 to 2,300/microl), T-helper lymphocytes (CD4+) <50/microl (reference >500/microl) and T-suppressor cells (CD8+) <50/microl (reference >300/microl), then no ATG was given. Further immunosuppression was continued with triple therapy consisting of methylprednisolone, azathioprine and cyclosporine. An historic group of heart transplant recipients given a full-dose ATG regimen for 8 days served as controls. These recipients were treated with ATG (Merieux 1.5 mg/kg) until reaching monoclonal cyclosporine levels of >300 mg/dl. Additional immunosuppressive treatment did not differ. Patients in both groups received systemic antibiotics (Imipenem) peri-operatively. Results of routine endomyocardial biopsies and rates of infections were examined. RESULTS: Study group patients were older (52 +/- 10 vs 49 +/- 14 years). In the study group, mean cumulative ATG dose was reduced significantly to 596 +/- 220 mg (p < 0.05) for 3.9 +/- 1.6 days compared with 1,159 +/- 376 mg for 6.9 +/- 1.1 days in the control group. The rate of cytomegalovirus (CMV) seroconversion was 23% in the study group compared with 13% in the control group. Rate of deep sternal infections was lower in the study group (1.6% vs 3.2%). The mean rejection rate in the first 3 months was 0.4 +/- 0.7 for the study patients (185 biopsies) vs 1.1 +/- 1.7 for controls (237 biopsies). All biopsies with ISHLT Grade >2 were treated successfully with 1,000 mg of methylprednisolone intravenously for 3 days. Both groups showed a similar 1-year survival rate (study 88%, control 89%). CONCLUSIONS: T-cell-adapted ATG induction therapy can be a helpful tool for individualized immunosuppression. It is not associated with an increased rate of rejection. Lower doses of immunosuppression help to minimize the rates of infection. In addition, cytolytic induction therapy combined with reduced ATG results in significant cost reduction.  相似文献   
999.
1000.
The prevention of new blood vessel growth is an increasingly attractive strategy to limit tumor growth. However, it remains unclear whether anti-angiogenesis approaches will impair wound healing, a process thought to be angiogenesis dependent. Results of previous studies differ as to whether angiogenesis inhibitors delay wound healing. We evaluated whether endostatin at tumor-inhibiting doses delayed excisional wound closure. C57/BL6J mice were treated with endostatin or phosphate-buffered solution 3 days prior to the creation of two full-thickness wounds on the dorsum. Endostatin was administered daily until wound closure was complete. A third group received endostatin, but also had daily topical vascular endothelial growth factor applied locally to the wound. Wound area was measured daily and the wounds were analyzed for granulation tissue formation, epithelial gap, and wound vascularity. Endostatin-treated mice showed a significant delay in wound healing. Granulation tissue formation and wound vascularity were significantly decreased, but reepithelialization was not effected. Topical vascular endothelial growth factor application to wounds in endostatin-treated mice resulted in increased granulation tissue formation, increased wound vascularity, and wound closure approaching that of control mice. This study shows that the angiogenesis inhibitor endostatin delays wound healing and that topical vascular endothelial growth factor is effective in counteracting this effect.  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