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   2013篇
  免费   139篇
  2023年   8篇
  2022年   12篇
  2021年   19篇
  2020年   16篇
  2019年   21篇
  2018年   33篇
  2017年   21篇
  2016年   39篇
  2015年   52篇
  2014年   75篇
  2013年   123篇
  2012年   109篇
  2011年   107篇
  2010年   53篇
  2009年   65篇
  2008年   92篇
  2007年   119篇
  2006年   114篇
  2005年   92篇
  2004年   99篇
  2003年   86篇
  2002年   94篇
  2001年   52篇
  2000年   69篇
  1999年   44篇
  1998年   21篇
  1997年   15篇
  1996年   17篇
  1995年   20篇
  1994年   11篇
  1993年   7篇
  1992年   43篇
  1991年   42篇
  1990年   44篇
  1989年   45篇
  1988年   42篇
  1987年   26篇
  1986年   22篇
  1985年   17篇
  1984年   18篇
  1983年   18篇
  1982年   14篇
  1981年   11篇
  1980年   12篇
  1979年   10篇
  1971年   8篇
  1969年   9篇
  1968年   10篇
  1967年   6篇
  1966年   8篇
排序方式: 共有2152条查询结果,搜索用时 625 毫秒
21.
A simple method to reconstruct the midlateral lid margin defect is described using an orbicularis oculi musculocutaneous advancement flap and a free conchal cartilage graft. This method is easy to perform not only in the lower eyelid, but also in the upper one, provides a natural gray line and a stable lid margin without postoperative eversion, and substitutes for the Leone and van Gemert procedure.  相似文献   
22.
23.
The cytologic presentation of a case of chondrosarcoma of the trachea in a 72-year-old man is described. A mass detected on routine chest roentgenogram and defined by CT scan was used to make a touch imprint smear during partial tumor resection. The cytologic findings included round or polygonal cells with occasional binucleation, round hyperchromatic nuclei and prominent nucleoli, present in an amorphous pink-violet or light-blue background containing fragments of chondroid tissue. The histopathology was interpreted as a low-grade chondrosarcoma. Cartilaginous tumors of the trachea should be considered in the differential diagnosis of upper airway obstruction.  相似文献   
24.
25.
To examine the effects of chronic dehydration and starvation on plasma levels of human atrial natriuretic polypeptide (hANP) in human subjects, the basal level and saline-induced rise of plasma hANP in 7 patients with anorexia nervosa were compared with those in age-matched healthy subjects. The unstimulated level of plasma hANP was markedly high in the patients with anorexia nervosa (patients vs. control; 55.4 +/- 9.0 pg/ml vs. 11.4 +/- 6.1 pg/ml, P less than 0.01). However, no significant increase of plasma hANP in the anorectic patients was observed in response to saline-infusion, while a 3-fold increase over the basal level of plasma hANP was noted in the saline-infused normal young subjects. These results show that hANP may be secreted to an inadequate extent, hence the release would be resistant to volume-loading. The pathophysiological meaning of such a high plasma concentrations of hANP in anorexia nervosa is the subject of ongoing studies.  相似文献   
26.
The effects of vitamin E (alpha-tocopherol) and its model compounds on the fluidity of liposomes composed of dipalmitoylphosphatidylcholin (DPPC) and fatty acids were investigated by the measurement of the fluorescent polarization (P) using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a plobe. Although all tocopherols decreased the fluidity of liposomes which was perturbed by the inclusion of an unsaturated fatty acid having more than one double bond, alpha-tocopherol was more effective than the others. The fluidity in arachidonic acid-containing liposomes was decreased most in the presence of alpha-tocopherol and was decreased considerably by the inclusion of model compounds having a side chain at least one isoprene unit or a long straight chain instead of isoprenoid side chain. However, the chromanol with methyl group instead of the above side chain, and phytol, having no chromanol moiety, had no effect. These results show that a structural requirement for a membrane stabilization is to be either the chromanol moiety with methyl groups born on its aromatic ring or a side chain of appropriate length; an isoprenoid side chain of full length or one containing 4'a- and 8'a-methyl groups is not necessarily needed.  相似文献   
27.
A stable human T-cell hybridoma was established by cell fusion between activated human peripheral blood lymphocytes from an allogeneic bone marrow transplantation patient and the JD1-17 cell line, a subclone of the human T leukemia Jurkat cell line. This hybrid clone 1-8, which bore the surface phenotype of suppressor cells (CD8+HNK1+), spontaneously secreted a factor which, at high dilutions, suppressed the responses of T and B cells induced by mitogens and alloantigens. This suppressor factor was found to be heat-resistant (56 degrees C, 30 min), stable at alkaline but not acid pH, unaffected by 2-mercaptoethanol, and sensitive to trypsin. Preparative isoelectric focusing revealed an isoelectric point of 5.35. The suppressor activity was selectively absorbed by blast T cells. By gel filtration on Sephacryl S-200 and HPLC, the suppressor activity was found in two peaks corresponding to 40-45 kDa (monomer) and 90-95 kDa (dimer).  相似文献   
28.
A plasma prealbumin variant with a methionine-for-valine substitution at position 30 is closely associated with familial amyloidotic polyneuropathy (FAP) type I. Secondary ion mass spectrometry of the tryptic digest of a carrier's prealbumin could easily detect an abnormal peptide containing the substitution besides the normal peptide. This is a sensitive and reliable method for the diagnosis of FAP.  相似文献   
29.
A joint study was undertaken in three testing facilities to evaluate cumulative background data of Himalayan rabbits. All litters were derived from control does. The conception rate was high (84.0-95.1%) but the average numbers of corpora lutea (7.9-8.7), implantation sites (6.5-7.5) and viable fetuses (5.8-6.9) were somewhat lower than that of most other strains of rabbit. Altogether 90 malformed fetuses (1.12%) and 425 fetuses with variations (5.27%) occurred among 8,060 virable fetuses.  相似文献   
30.
Na+,K+-ATPase from pig kidney was specifically modified with a sulfhydryl fluorescent reagent, N-[p-(2-benzimidazolyl)phenyl]maleimide (BIPM), by pretreatment of N-ethylmaleimide. The preparation thus obtained retained 100% of initial Na+,K+-ATPase activity and contained 1 BIPM residue/alpha-chain, and it showed almost 2-fold larger fluorescence changes accompanying ATP hydrolysis than the previous preparations which retained 60% of initial activity and contained 3-4 BIPM residues/alpha-chain (Taniguchi, K., Suzuki, K., and Iida, S. (1982) J. Biol. Chem. 257, 10659-10667). Extensive trypsin (Sigma type I) treatment of the new preparation produced mainly two different fluorescent peptide peaks in both ion-exchange and reverse-phase chromatography. Amino acid sequence analysis of both peptides showed that they had the same common sequence, Ser-Tyr-X-Pro-Gly-Met-Gly-Val, except that the larger one contained Ala-Leu next to the Val residue. From the comparison of the amino acid sequence deduced from cDNA from sheep kidney (Shull, G. E., Schwartz, A., and Lingrel, J. B. (1985) Nature 316, 691-695), X was shown to correspond to Cys-964 of the alpha-chain in Na+,K+-ATPase. The data suggest that the microenvironment of the BIPM residue covalently bound to the sulfhydryl group of Cys-964 changes accompanying sequential appearance of reaction intermediates of Na+,K+-ATPase.  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