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   6594篇
  免费   374篇
  国内免费   29篇
耳鼻咽喉   95篇
儿科学   381篇
妇产科学   97篇
基础医学   778篇
口腔科学   102篇
临床医学   448篇
内科学   1478篇
皮肤病学   96篇
神经病学   475篇
特种医学   122篇
外科学   957篇
综合类   183篇
一般理论   6篇
预防医学   365篇
眼科学   218篇
药学   697篇
中国医学   80篇
肿瘤学   419篇
  2023年   41篇
  2022年   32篇
  2021年   239篇
  2020年   108篇
  2019年   159篇
  2018年   222篇
  2017年   151篇
  2016年   162篇
  2015年   190篇
  2014年   270篇
  2013年   363篇
  2012年   490篇
  2011年   508篇
  2010年   289篇
  2009年   257篇
  2008年   393篇
  2007年   369篇
  2006年   315篇
  2005年   326篇
  2004年   235篇
  2003年   205篇
  2002年   226篇
  2001年   103篇
  2000年   116篇
  1999年   101篇
  1998年   74篇
  1997年   38篇
  1996年   38篇
  1995年   30篇
  1993年   30篇
  1992年   55篇
  1991年   71篇
  1990年   71篇
  1989年   56篇
  1988年   46篇
  1987年   55篇
  1986年   42篇
  1985年   58篇
  1984年   45篇
  1983年   36篇
  1982年   24篇
  1980年   19篇
  1979年   30篇
  1978年   23篇
  1977年   27篇
  1975年   21篇
  1973年   31篇
  1972年   20篇
  1971年   27篇
  1969年   21篇
排序方式: 共有6997条查询结果,搜索用时 109 毫秒
61.
Antibodies to surface antigens of intracellular naked vaccinia virus (INV) and in limited studies extracellular enveloped virus (EEV) were determined by single radial immunodiffusion tests (SRDT) with immobilized virions in agarose gels. Antibodies to INV were demonstrable in rabbit hyperimmune sera (one to four visible zones), smallpox convalescent sera and sera from re-vaccinated individuals. A difference in specificity of antibodies reacting with INV and EEV was detectable by SRDT. The SRDT provides a simple, reproducible and specific test for detection of antibodies against vaccinia or variola virus, but the technique requires large quantities of virions.  相似文献   
62.
Mammalian β-defensins are small cationic peptides possessing broad antimicrobial and physiological activities. Because dogs are particularly resilient to sexually transmitted diseases, it has been proposed that their antimicrobial peptide repertoire might provide insight into novel antimicrobial therapeutics and treatment regimens. To investigate this proposal, we cloned the full-length cDNA of three canine β-defensin isoforms (cBD-1, -2, and -3) from canine testicular tissues. Their predicted peptides share identical N-terminal 65-amino-acid residues, including the β-defensin consensus six-cysteine motif. The two longer isoforms, cBD-2 and -3, possess 4 and 34 additional amino acids, respectively, at the C terminus. To evaluate the antimicrobial activity of cBD, a 34-amino-acid peptide derived from the shared mature peptide region was synthesized. Canine β-defensin displayed broad antimicrobial activity against gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus; MICs of 6 and 100 μg/ml, respectively), gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, and Neisseria gonorrhoeae; MICs of 20 to 50, 20, and 50 μg/ml, respectively), and yeast (Candida albicans; MIC of 5 to 50 μg/ml) and lower activity against Ureaplasma urealyticum and U. canigenitalium (MIC of 200 μg/ml). Antimicrobial potency was significantly reduced at salt concentrations higher than 140 mM. All three canine β-defensins were highly expressed in testis. In situ hybridization indicated that cBD-1 was expressed primarily in Sertoli cells within the seminiferous tubules. In contrast, cBD-2 was located primarily within Leydig cells. The longest isoform, cBD-3, was detected in Sertoli cells and to a lesser extent in the interstitium. The tissue-specific expression and broad antimicrobial activity suggest that canine β-defensins play an important role in host defense and other physiological functions of the male reproductive system.  相似文献   
63.
Summary: Hydrophobically modified poly(acrylic acid) was synthesized using 3‐pentadecylcyclohexylamine (3‐PDCA), which was in turn synthesized from 3‐pentadecylphenol, one of the components of cashew‐nut shell liquid (CNSL), a renewable resource material. 1H NMR spectra confirmed the incorporation of 3‐PDCA onto PAA and a series of HMPs with three different molar concentrations, viz ? 3, 5 and 7 mol‐% of 3‐PDCA, were synthesized. An increase in viscosity with increasing hydrophobic content was observed by rheological measurements. The critical association concentrations were determined using an Ubbelohde viscometer and a controlled stress rheometer. The stability of HMPs towards temperature and shear was studied. Rheological measurements showed that there was a steady increase in viscosity with increase in hydrophobe content due to the formation of reversible networks. These polymers exhibited gel‐like behavior at low concentrations (≥2 wt.‐%) with an apparent yield stress (ca. 10 Pa) and showed shear thinning properties (non‐Newtonian). However, below a critical concentration, c [η], they showed Newtonian behavior.

ηsp of unmodified and modified PAA‐Na at various polymer concentrations.  相似文献   

64.
65.
High level of plasma creatinine occurs in renal insufficiency, uremia, and other diseases. At present lowering of this metabolite is done by using dialysis and other techniques. In this article, we report the use of artificial cells microencapsulated genetically engineered E. coli DH5 cells for lowering plasma creatinine in-vitro and in-vivo. Result shows that artificial cells were able to lower plasma creatinine in-vitro from 21.80 +/- 1.10 mg/dl to 21.80 +/- 1.10 mg/dl in 60 minutes and to 19.34 +/- 0.60 mg/dl in 3 hours. Result also shows that when given orally on a daily basis, artificial cells microencapsulated genetically engineered E. coli DH5 cells were also able to lower plasma creatinine in rats.  相似文献   
66.
There is a deficit of literature regarding the association between nickel allergy–induced symptoms and implanted devices. This report describes a case of nickel allergy causing debilitating migraine-like symptoms, failing to resolve with medical therapy, requiring surgical removal of the device and repair of the defect.  相似文献   
67.

Textile dyes are becoming a growing threat to the environment. This report presents the findings of the study on the toxicity of the textile dye Alizarin Red S on two freshwater microalgae. The acute toxicity assay revealed that 96-h EC50 values of Chlorella vulgaris and Spirulina platensis were 29.81 mg/L and 18.94 mg/L respectively. The pigments chlorophyll-a, b and carotenoids in C. vulgaris on 96-h exposure to the dye were 2.91, 3.29 and 3.01 times lower in analogy to control whereas Spirulina platensis showed 2.89and 2.56 fold decrease in chlorophyll-a and carotenoid content than control. After the test period of 96-h with dye, the protein content of C. vulgaris and S. platensis were 2.33 and 1.77 times lower compared to the control. The growth inhibition rate, pigment as well as the protein content declined in compliance with the rise in dye concentration, which anticipate paradigm about the toxic effects of the textile dye.

  相似文献   
68.
The study aim was to examine the effect on birth spacing of a prior female child's birth. The study site was a rural health center under observation by staff from the Dayanand Medical College in Ludhiana, India. The sample included 73 pregnant women who were grouped by the sex of the preceding child. The results showed that the average birth interval was significantly shorter for women with a preceding birth of a female child. The average interval in weeks was 90.73 weeks + or - 54.46 weeks for the 41 women who had a prior girl child compared to 133.68 weeks for the male child. When the female child was at a parity of one the birth interval averaged 73.36 weeks, compared to 137.2 weeks for a prior parity of one male child. At parity of two, the average birth interval was 106.2 for a prior girl child and 144.38 for a prior male child. At a parity of three, the average birth interval was 88.22 weeks for a prior girl child and 96.5 weeks for a prior male child. At a parity of four, the average birth interval was 87.66 weeks for a prior girl child and 46.0 weeks for a prior male child. The significant effect of having a prior girl child was evident only at a parity of one. The intervals at a parity of two and three were shorter for girls but not significantly different. The recommendation was that young women and women with low parity be targeted for family planning in order to lengthen the birth interval, regardless of the desire for sons.  相似文献   
69.
Craniofacial osteogenic sarcomas are rare primary malignant bone tumors and very few cases involving zygomatic bone were reported in literature. We present our experience of multimodality management of a case of primary osteogenic sarcoma of zygoma. Wide radical excision of the tumor including the parotid gland was done followed by three cycles of adjuvant chemotherapy and fifty Gy of external radiotherapy. The patient is disease-free at two years follow-up. Till 1970s, craniofacial osteogenic sarcomas were managed mainly by radical surgery with a high local failure rate. With the advances made in the field of radiotherapy and chemotherapy, multimodality therapy is playing a major role in the treatment of these aggressive tumors with better overall and disease-free survival.  相似文献   
70.
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