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   1349篇
  免费   63篇
  国内免费   12篇
耳鼻咽喉   17篇
儿科学   49篇
妇产科学   38篇
基础医学   121篇
口腔科学   121篇
临床医学   102篇
内科学   321篇
皮肤病学   21篇
神经病学   49篇
特种医学   33篇
外科学   202篇
综合类   31篇
预防医学   69篇
眼科学   43篇
药学   107篇
中国医学   8篇
肿瘤学   92篇
  2023年   12篇
  2022年   35篇
  2021年   63篇
  2020年   25篇
  2019年   40篇
  2018年   53篇
  2017年   31篇
  2016年   34篇
  2015年   40篇
  2014年   53篇
  2013年   76篇
  2012年   112篇
  2011年   112篇
  2010年   61篇
  2009年   68篇
  2008年   69篇
  2007年   65篇
  2006年   76篇
  2005年   77篇
  2004年   57篇
  2003年   47篇
  2002年   41篇
  2001年   15篇
  2000年   15篇
  1999年   8篇
  1998年   10篇
  1997年   4篇
  1996年   8篇
  1995年   8篇
  1994年   6篇
  1993年   4篇
  1992年   8篇
  1990年   3篇
  1989年   7篇
  1987年   4篇
  1986年   4篇
  1985年   7篇
  1984年   7篇
  1983年   9篇
  1982年   4篇
  1981年   4篇
  1980年   3篇
  1979年   7篇
  1978年   8篇
  1977年   4篇
  1974年   3篇
  1972年   2篇
  1970年   3篇
  1967年   2篇
  1966年   2篇
排序方式: 共有1424条查询结果,搜索用时 31 毫秒
101.
Prevalence of intestinal helminths of dogs and foxes from Jordan   总被引:2,自引:0,他引:2  
Necropsy of 340 stray and semi-stray dogs (Canis familiaris) and nine red foxes (Vulpes vulpes) from Jordan revealed that 239 dogs (70.3%) and all foxes were infected with at least one intestinal helminth species. No trematodes were found in the intestine of these hosts. The overall infection rates with cestodes, nematodes and acanthocephalans in dogs were 66.8%, 4.4% and 2.9%, respectively. The following cestodes were identified: Echinococcus granulosus (9.4%), Taenia pisiformis (11.8%), T. hydatigena (7.4%), T. ovis (4.4%), T. multiceps (3.8%), T. taeniaeformis (2.9%), Dipylidium caninum (19.4%), Joyeuxiella (3.2%), Diplopylidium (2.4%), and Mesocestoides (0.9%). Other intestinal worms in dogs were Toxascaris (2.6%), Toxocara canis (1.2%), and Protospirura (0.6%) nematodes, and gigantorhynchiid acanthocephalans (2.9%). Intestinal helminths found in foxes included cestodes (D. caninum, Joyeuxiella, Diplopylidium, Mesocestoides), nematodes (Protospirura, Uncinaria stenocephala and Oxynema) and an acanthocephalan (Macracanthorhynchus). In both hosts, most helminths were recovered from the second intestinal segment of four equally divided segments. Received: 11 March 1999 / Accepted: 10 June 1999  相似文献   
102.
PURPOSE: The precise determination of skin's mechanical properties is still an open question. When performing an in vivo test, the piece of skin tested is not as well defined as it is in material testing. Moreover, the body zone and the body posture imply an initial stress on the skin. Consequently, a precise mechanical analysis needs a precise measurement of the natural skin tension. METHODS: A new method and the relative device are presented. It is based on an extensiometry test. Skin is tested not only in traction but also in compression. The tested skin sample is well defined and protected from surrounding effects by follower tabs. The size and shape of the device have been optimised by a finite element modelisation. RESULTS: The method was tested with elastomers pre-tensioned at different loads. It is shown that the initial tension can be retrieved with good precision. Tests were then performed in vivo on the forearm for different arm positions. It is shown that initial tension could be only clearly determined for the highest skin tension, although the skin presented very different traction behaviour with different arm positions. CONCLUSION: It is shown how body posture influences measurements. An innovative method for easily determining initial tension is presented. Nevertheless, further tests and device improvements are needed to apply this skin tension measurement for different body zones and body postures.  相似文献   
103.
OBJECTIVE: To study the effect of mesenchymal stem cells (MSC) on experimental liver fibrosis in rats. DESIGN AND METHOD: MSC were derived from bone marrow obtained from femoral and tibial bones of male albino rats. MSC were separated, grown, and propagated in culture for 4 weeks and were characterized morphologically and by detection of CD29 by RT-PCR. They were then infused into the tail vein of female rats that received CCl4 injection to induce liver fibrosis. Rats were divided into 4 groups: control, CCl4, CCl4 plus MSC, and MSC. Liver tissue was examined histopathologically and liver functions (ALT and serum albumin) were estimated for all groups. Y-chromosome gene (sry) was assessed by PCR in liver tissue of the female rats to confirm uptake of the male stem cells. Hydroxyproline content in liver tissue was assessed by chemical methods and expression of the collagen gene (type I) was detected as a marker for liver fibrosis. Results of the present study showed that MSC have a significant antifibrotic effect as evidenced by the significant decrease in liver collagen gene expression as well as the decrease in hydroxyproline content in the CCl4/MSC group (p<0.001) compared to the CCl4 group. The Y-chromosome gene (sry) was detected by RT-PCR in the CCl4/MSC group, but was not detected in control group and other groups. The CD29 gene was expressed in MSC culture, and this confirmed the efficiency of isolation and propagation of MSC in culture. With regard to liver function, there was also a significant improvement and elevation of serum albumin in the CCl4/MSC group compared to the CCl4 group (p<0.05). As regard to the liver enzyme ALT, there was a decrease of its level in the CCl4/MSC group compared to the CCl4 group. However, this was statistically nonsignificant (p>0.05). In conclusion, MSC have a potential therapeutic effect against the fibrotic process through their effect in minimizing collagen deposition in addition to their capacity to differentiate into hepatocytes.  相似文献   
104.

Background

Hospital-associated UTI rates in surgery patients have not improved despite recommendations for reducing indwelling catheter days.

Methods

We performed a retrospective review of institutional NSQIP general surgery patient data, 2006–2015. During this time, a UTI-reduction policy was implemented. Demographics, HA-UTI incidence, CA-UTI incidence, indwelling catheter days, straight catheterization rates, and mortality were examined.

Results

Females had significantly higher risk of HA-UTI. There was no significant change in HA-UTI (X12?=?0.02, p?=?.878) or indwelling catheter days (5.18?±?1.12 days v 3.73?±?0.39 days, p?=?.23). Straight catheterizations among those with HA-UTI increased (0.04?±?0.04 v 0.32?±?0.12, p?=?.029). There was no change in CA-UTI (1.38 v 1.11 CAUTI/1000 patient hospital-days P?=?.555) or in initial indwelling catheter days of patients with CA-UTI (7.2 SD 8.89 v 47.0 SD 7.04 days P?=?.961) after policy implementation.

Conclusions

The reduction policy increased the number of straight catheterizations for patients developing HA-UTI, but did not reduce the number of initial indwelling catheter days, HA-UTI rates, or CA-UTI rates.  相似文献   
105.
Abstract:   Cervicogenic headache is a chronic hemicranial pain, usually occurring daily. This randomized, double-blind, placebo-controlled trial evaluated the effectiveness of nerve stimulator-guided occipital nerve blockade in the treatment of cervicogenic headache. The reduction in analgesic consumption was the primary outcome measure. Fifty adult patients diagnosed with cervicogenic headache were randomly divided into two equal groups of 25 patients each. All patients in both groups received greater and lesser occipital blocks, whereas only 16 patients in each group received facial nerve blockade in association with the occipital blocks. The control group received injections of an equivalent volume of preservative-free normal saline. Pain was assessed using the visual analog scale (VAS) and the Total Pain Index (TPI). Forty-seven patients entered into the final analysis as three patients were lost to follow-up. Anesthetic block was effective in reducing the VAS and the TPI by approximately 50% from baseline values ( P  = 0.0001). Analgesic consumption, duration of headache and its frequency, nausea, vomiting, photophobia, phonophobia, decreased appetite, and limitations in functional activities were significantly less in block group compared to control group ( P  < 0.05). The nerve stimulator-guided occipital nerve blockade significantly relieved cervicogenic headache and associated symptoms at two weeks following injection.  相似文献   
106.

Background

Total parenteral nutrition (TPN) is often used in children with perforated appendicitis, despite the absence of clear indications. We assessed the validity of specific clinical indications for initiation of TPN in this patient cohort.

Methods

Data were gathered prospectively on duration of nil per os (NPO) status and TPN use in a cohort of children treated under a perforated appendicitis protocol during a 19-month period. TPN was started in the immediate postoperative period in patients who had generalized peritonitis and severe intestinal dilatation at operation, or later per the discretion of the attending surgeon. At discharge, TPN was considered to have been used appropriately, according to consensus guidelines, if the patient was NPO  7 days or received TPN  5 days.

Results

During the study period, TPN was initiated in 31 (25.4%) of 122 patients operated for perforated appendicitis. Sixteen (51.6%) received TPN per operative finding indications and 15 (48.4%) for prolonged ileus. The operative indications demonstrated 47% sensitivity, 86% specificity, a positive predictive value (PPV) of 35%, and a negative predictive value (NPV) of 91%, when adherence to TPN consensus guidelines was considered the gold standard.

Conclusion

Patients without severe intestinal dilatation and generalized peritonitis at operation should not be placed on TPN in the immediate postoperative period. Refinement of selection criteria is necessary to further decrease inappropriate TPN use in children with perforated appendicitis.

Type of study

Diagnostic Test.

Level of study

II  相似文献   
107.
BACKGROUND: It has been suggested that single-use biopsy forceps prevent interpatient transmission of infection during endoscopy. Passage of sterile forceps through the accessory channel of the endoscope may lead to contamination, however, if the endoscope has been inadequately processed. The potential for contamination of single-use biopsy forceps at various stages of endoscope reprocessing was prospectively evaluated. METHODS: A total of 50 disposable biopsy forceps were passed through the accessory channels of 10 colonoscopes at the following stages of reprocessing: (1) before use in patients to establish a baseline of high-level disinfection, (2) directly after colonoscopy to confirm contamination with use, (3) after manual cleaning and flushing of the accessory channel to support the claim that manual cleaning significantly decreases bioburden, (4) after manual cleaning and a 2-minute soak in 2% glutaraldehyde to assess for contamination after an inadequate cleaning time, and (5) after manual cleaning and a 20-minute soak in 2% glutaraldehyde. The forceps were then sealed in sterile plastic bags after adding 20 mL of thioglycollate broth medium. The suspension was passed through a 0.2-micron vacuum filter and the filters were cultured. All cultures were incubated more than 48 hours. RESULTS: Biopsy forceps underwent a total of 50 aerobic and 50 anaerobic cultures. Colony-forming units too numerous to count of GI flora, including Escherichia coli, Klebsiella, Pseudomonas, and Clostridium species, grew on 19 of 20 culture plates from biopsy forceps passed through colonoscopes immediately after use. One plate in this group grew 3 colony-forming units of E coli. Persistence of GI flora was noted on 5 of 20 plates after manual cleaning of the colonoscopes. No GI flora were found on forceps after the colonoscopes after soaking in gluteraldehyde for 2 and 20 minutes. Environmental contaminants including diptheroids, Staphylococcus, and Streptococcus species grew on 16 culture plates. CONCLUSIONS: (1) Single-use biopsy forceps are highly susceptible to contamination during passage through the accessory channels of improperly cleaned endoscopes. (2) Disinfection of the colonoscopes in this study prevented contamination of the forceps at baseline and after reprocessing. (3) Proper endoscope reprocessing may be the most important factor in preventing biopsy forceps-related interpatient infection.  相似文献   
108.
Tadros GM  Broder K  Bachour F 《Angiology》2005,56(6):761-765
The occurrence of intracoronary thrombus during percutaneous coronary intervention (PCI) is a well-known complication. It has been estimated that it complicates approximately 6% of all coronary procedures. Patients at highest risk for this complication include those with acute ischemic syndromes or with angiographically apparent thrombus. Since the development of PCI, intravenous unfractionated heparin (UFH) has remained the primary antithrombotic therapy for the prevention of periprocedural ischemic complications. The availability of a rapid "point of care' test for dose individualization (the activated clotting time [ACT]) has facilitated this process. Other forms of antithrombotic therapies such as direct thrombin inhibitors or low-molecular-weight heparin have been proposed as more effective anticoagulants during PCI. Bivalirudin is a direct thrombin inhibitor proven to decrease post-PCI ischemic complication rate compared with UFH and have a lower vascular complication rate compared with glycoprotein IIb/IIIa receptor antagonists. We herein report a case of acute macrothrombus formation during PCI despite adequate ACT achieved with bivalirudin.  相似文献   
109.
The reaction of nucleophilic phosphacumulene and phosphallene ylides with different chromenone derivatives was investigated. Heterocycles and carbocycles of various ring sizes and heteroatom patterns such as pyrano-, oxaphosphino-, cyclopenta-, phosphoranylidene cyclobutane-, and phospholo-chromenones were obtained. The antitumor (breast and liver) properties of some new compounds were performed in vitro. Some of these compounds were more potent than the comparative standard.  相似文献   
110.
Aberrantly hyperactivated STAT3 has been found in human liver cancers as an oncogene; however, STAT3 has also been shown to exert hepatoprotective effects during liver injury. The balancing act that STAT3 plays between hepatoprotection and liver tumorigenesis remains poorly defined. In this study, the diethylnitrosamine (DEN)-induced liver tumor model and the chronic carbon tetrachloride (CCl(4))-induced liver fibrosis model were both used to investigate the role of STAT3 in liver tumorigenesis. Hepatocyte-specific STAT3 knockout mice were resistant to liver tumorigenesis induced by a single DEN injection, whose tumorigenesis was associated with minimal chronic liver inflammation, injury, and fibrosis. In contrast, long-term CCl(4) treatment resulted in severe hepatic oxidative damage, inflammation, and fibrosis but rarely induced liver tumor formation in wild-type mice. Despite the oncogenic function of STAT3 in DEN-induced liver tumor, hepatocyte-specific STAT3 knockout mice were more susceptible to liver tumorigenesis after 16 weeks of CCl(4) injection, which was associated with higher levels of liver injury, inflammation, fibrosis, and oxidative DNA damage compared with wild-type mice. These findings suggest that the hepatoprotective feature of STAT3 prevents hepatic damage and fibrosis under the condition of persistent inflammatory stress, consequently suppressing injury-driven liver tumor initiation. Once liver tumor cells have developed, STAT3 likely acts as an oncogenic factor to promote tumor growth.  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