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   2585篇
  免费   237篇
  国内免费   52篇
耳鼻咽喉   22篇
儿科学   205篇
妇产科学   79篇
基础医学   350篇
口腔科学   50篇
临床医学   232篇
内科学   600篇
皮肤病学   52篇
神经病学   102篇
特种医学   255篇
外科学   271篇
综合类   102篇
一般理论   1篇
预防医学   146篇
眼科学   39篇
药学   216篇
中国医学   3篇
肿瘤学   149篇
  2023年   21篇
  2022年   25篇
  2021年   39篇
  2020年   33篇
  2019年   22篇
  2018年   40篇
  2017年   64篇
  2016年   64篇
  2015年   67篇
  2014年   102篇
  2013年   119篇
  2012年   102篇
  2011年   117篇
  2010年   109篇
  2009年   112篇
  2008年   102篇
  2007年   141篇
  2006年   109篇
  2005年   93篇
  2004年   88篇
  2003年   91篇
  2002年   72篇
  2001年   73篇
  2000年   56篇
  1999年   47篇
  1998年   91篇
  1997年   73篇
  1996年   72篇
  1995年   61篇
  1994年   56篇
  1993年   51篇
  1992年   23篇
  1991年   36篇
  1990年   52篇
  1989年   40篇
  1988年   48篇
  1987年   33篇
  1986年   41篇
  1985年   32篇
  1984年   22篇
  1983年   21篇
  1982年   17篇
  1981年   11篇
  1980年   13篇
  1979年   12篇
  1977年   11篇
  1976年   13篇
  1975年   11篇
  1974年   10篇
  1937年   18篇
排序方式: 共有2874条查询结果,搜索用时 27 毫秒
1.
Haaga  JR; Beale  SM 《Radiology》1986,161(3):829-830
By injecting small amounts of CO2 through a needle, one can move bowel or bladder from the intended path of instruments during interventional procedures. The technique worked well in six of seven cases in the pelvis and retroperitoneum; it was not effective in the mediastinum or midabdomen (n = 6).  相似文献   
2.
3.
We tested the hypothesis that bone mineral density (BMD) and bone mineral content (BMC) in proximal human femur specimens in the upper neck region of interest (ROI) and femoral neck axis length (FNAL) provide a significantly better prediction of femoral bone strength than standard ROIs in vitro. BMD and BMC were measured in 110 proximal femur specimens using a standard dual-energy X-ray absorptiometry (DXA) scanner. The analysis included a new ROI in the upper neck as well as the standard ROIs. FNAL was obtained from the scan images. The specimens' failure-load was measured in a mechanical loading device, simulating a fall on the greater trochanter. For the standard ROIs, correlations between failure-load and BMD ranged from R2 = 0.64 (shaft ROI) to R2 = 0.70, p < 0.001 (femoral neck). Prediction of strength by BMD did not significantly differ from those of BMC (R2 ranging from 0.65 to 0.75, p < 0.001). In the upper neck ROI, for both BMD and BMC correlations with failure-load were higher (R2 = 0.76 and 0.81, respectively; p < 0.001). A lower, yet still significant, correlation was found between FNAL and bone strength (R2 = 0.23, p < 0.001). Normalization of failure-load with respect to FNAL did not significantly increase the correlations with densitometric measures. This study provides in vitro evidence indicating that among the ROIs of the proximal femur the newly defined upper neck ROI provides the best prediction of bone strength. Only a weak association was observed between failure load and FNAL.  相似文献   
4.
A primary monolayer culture system from cockerel hepatocytes was established. The cultures synthesize and secrete proteins that comigrate with authentic serum proteins on polyacrylamide gels and are found in the same relative abundance. Addition of estradiol increased the synthesis of apoprotein B, found in very low density lipoprotein, under all culture conditions. Vitellogenin synthesis could not be induced directly by estradiol. However, when serum was obtained from cockerels injected with estradiol 4 days before blood collection and included in the culture medium, the cultures secreted a protein identified immunologically as vitellogenin by affinity chromatography. Furthermore, addition of growth hormone or prolactin to cultured cockerel hepatocyte monolayers resulted in the synthesis and secretion of a polypeptide that comigrates with authentic vitellogenin on polyacrylamide gels.  相似文献   
5.
BACKGROUND: The process of gastro-duodenal digestion may play a role in determining the allergenic properties of food proteins. The sensitizing and allergenic potential of digestion products of highly degraded allergens, such as the major peanut allergen Ara h 1, is currently under debate. We evaluated the effect of in vitro gastro-duodenal digestion of Ara h 1 on T cell reactivity and basophil histamine release. METHODS: An in vitro model of gastro-duodenal digestion was used to investigate changes in the allergenic properties of Ara h 1 using in vitro assays monitoring T cell reactivity (proliferation, cytokine production) and histamine release of basophils from peanut allergic individuals. The digestion process was monitored using an SDS-PAGE gel. RESULTS: In vitro gastric digestion led to rapid degradation of Ara h 1 into small fragments M(r) L5600. Gastric digestion did not affect the ability of Ara h 1 to stimulate cellular proliferation. Gastro-duodenal digestion significantly reduced its ability to stimulate clonal expansion (P<0,05; Wilxocon's signed rank test). The Th-2 type cytokine polarization of T cells from peanut allergic donors (IFN-gamma/IL-13 ratio and IFN-gamma/IL-4 ratio of CFSE(low) CD4(+) T cells) remained unchanged regardless of the level of digestion. Histamine release of basophils from peanut allergic individuals was induced to the same extent by native Ara h 1 and its digestion products. CONCLUSION: Gastro-duodenal digestion fragments of Ara h 1 retain T cell stimulatory and IgE-binding and cross-linking properties of the intact protein.  相似文献   
6.
外科医生和手术室人员经常接触手术设备产生的烟气,病人也会暴露于烟气中,特别是腹腔镜手术中产生的烟气滞留于腹腔内这一密闭空间并被吸收.这些烟气是一种与香烟烟气相似的毒性物质,然而对这种毒性物质的影响还未引起足够重视.应该采取必要措施尽可能减少手术中烟气的不良影响.  相似文献   
7.
Heterotopes Pankreasgewebe der Magenwand   总被引:2,自引:0,他引:2  
Heterotopic pancreas is an uncommon cause of gastrointestinal complaints such as epigastric pain, nausea, vomiting, and upper gastrointestinal bleeding. Despite the development of modern diagnostic procedures, it is still difficult to differentiate heterotopic pancreatic tissue from other benign or malignant gastric tumors. Local excision of the gastric wall is regarded as the diagnostic and therapeutic procedure of choice. We present two cases and an overview of the literature.  相似文献   
8.
9.
10.
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