全文获取类型
收费全文 | 10959篇 |
免费 | 497篇 |
国内免费 | 64篇 |
专业分类
耳鼻咽喉 | 73篇 |
儿科学 | 206篇 |
妇产科学 | 118篇 |
基础医学 | 1487篇 |
口腔科学 | 184篇 |
临床医学 | 744篇 |
内科学 | 2613篇 |
皮肤病学 | 130篇 |
神经病学 | 758篇 |
特种医学 | 478篇 |
外科学 | 2271篇 |
综合类 | 33篇 |
预防医学 | 283篇 |
眼科学 | 228篇 |
药学 | 952篇 |
中国医学 | 41篇 |
肿瘤学 | 921篇 |
出版年
2022年 | 94篇 |
2021年 | 164篇 |
2020年 | 92篇 |
2019年 | 128篇 |
2018年 | 198篇 |
2017年 | 137篇 |
2016年 | 148篇 |
2015年 | 176篇 |
2014年 | 234篇 |
2013年 | 277篇 |
2012年 | 422篇 |
2011年 | 475篇 |
2010年 | 246篇 |
2009年 | 200篇 |
2008年 | 438篇 |
2007年 | 455篇 |
2006年 | 443篇 |
2005年 | 487篇 |
2004年 | 452篇 |
2003年 | 425篇 |
2002年 | 477篇 |
2001年 | 325篇 |
2000年 | 388篇 |
1999年 | 382篇 |
1998年 | 138篇 |
1997年 | 98篇 |
1996年 | 124篇 |
1995年 | 101篇 |
1994年 | 108篇 |
1993年 | 100篇 |
1992年 | 350篇 |
1991年 | 326篇 |
1990年 | 282篇 |
1989年 | 324篇 |
1988年 | 281篇 |
1987年 | 259篇 |
1986年 | 251篇 |
1985年 | 239篇 |
1984年 | 150篇 |
1983年 | 124篇 |
1982年 | 61篇 |
1979年 | 125篇 |
1978年 | 92篇 |
1977年 | 57篇 |
1975年 | 64篇 |
1974年 | 56篇 |
1973年 | 53篇 |
1972年 | 50篇 |
1969年 | 54篇 |
1967年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
51.
52.
K Miyamoto Y Kawashima H Matsuda A Okuda S Maeda H Hirose 《The Journal of thoracic and cardiovascular surgery》1986,92(6):1065-1070
The relationship between the perfusion flow rate and cerebral oxygen consumption during deep hypothermic cardiopulmonary bypass at 20 degrees C was investigated in dogs. In 10 dogs the perfusion flow rate was decreased in steps from 100 to 60, 30, and 15 ml/kg/min every 30 minutes. Although cerebral blood flow decreased as perfusion flow rate decreased, the ratio of cerebral blood flow to the perfusion flow rate increased significantly (p less than 0.05) at a perfusion flow rate of 15 ml/kg/min compared to that at a perfusion flow rate of 100 or 60 ml/kg/min. The arterial-sagittal sinus blood oxygen content difference increased as perfusion flow rate decreased. Consequently, cerebral oxygen consumption did not vary significantly at perfusion flow rates of 100 (0.48 +/- 0.10), 60 (0.43 +/- 0.14), and 30 ml/kg/min (0.44 +/- 0.12 ml/100 gm/min), and it decreased significantly to 0.31 +/- 0.22 ml/100 gm/min at a perfusion flow rate of 15 ml/kg/min. In five dogs the perfusion flow rate was decreased in one step from 100 to 15 ml/kg/min, and after 60 minutes' perfusion at a perfusion flow rate of 15 ml/kg/min, the perfusion flow rate was returned to 100 ml/kg/min. Cerebral oxygen consumption decreased significantly during 60 minutes' perfusion at a perfusion flow rate of 15 ml/kg/min and did not return to its initial value after the perfusion flow rate was returned to 100 ml/kg/min. These data indicate that the optimal perfusion flow rate for the brain during deep hypothermic cardiopulmonary bypass at 20 degrees C appears to be 30 ml/kg/min, with a possible oxygen debt in the brain resulting in anaerobic metabolism if the perfusion flow rate is kept at 15 ml/kg/min or less. 相似文献
53.
The effect of dietary fiber on the induction of cytochrome P450IA1 in rat colonic mucosa after a single intragastric injection of 3-methylcholanthrene (3MC, 20 mg/kg) was investigated by examining the drug-metabolizing enzyme activity, immunoblotting for cytochrome P450IA1 and immunohistochemistry. 7-Ethoxycoumarin-O-deethylase activities were approximately 20-fold higher in microsomes from both proximal and distal portions of the colonic mucosa of control diet-fed 3MC-treated rats compared with those of control diet-fed untreated rats. Strong immunofluorescence for cytochrome P450IA1 was localized in the cytoplasm of the colonic mucosa surface epithelium from the control diet-fed 3MC-treated rats. 7-Ethoxycoumarin-O-deethylase activity and cytochrome P450IA1 content determined by immunoblotting were significantly lower in wheat bran-fed 3MC-treated rats than in control diet-fed 3MC-treated rats. Immunohistochemical analysis showed much weaker immunofluorescence for cytochrome P450IA1 in the surface epithelium of the colonic mucosa of the wheat bran-fed 3MC-treated rats. These observations suggested that dietary fiber can affect the induction of cytochrome P450IA1 in colonic mucosa by dietary inducers or carcinogens. 相似文献
54.
55.
M Urashima S Toyoda T Nakano S Matsuda N Kobayashi H Kitajima A Tokushige H Horita J Akatsuka K Maekawa 《Journal of pediatric gastroenterology and nutrition》1992,15(1):89-92
Determining the site and severity of blood loss is important in the management of children with gastrointestinal (GI) bleeding. Blood urea nitrogen (BUN) and serum creatinine (Cr) were measured on the day of hospitalization and the ratio of BUN/Cr was calculated in 11 children with 16 episodes of upper GI bleeding and 49 with lower GI bleeding. There was a significant difference between the two GI bleeding groups with regard to BUN/Cr ratio (p less than 0.001). When the ratio was 30 or above, the specificity of upper GI bleeding was 98% with a sensitivity of 68.8%. A linear relationship was found between the BUN/Cr ratio and delta Hb (delta Hb = 0.08 x BUN/Cr +/- 0.8 g/dl) for bleeding originating from the upper GI tract. This study confirms that measurement of the BUN/Cr ratio is useful for localizing the source of bleeding to the upper GI tract and also demonstrates its usefulness as an estimation of the severity of blood loss from the upper GI tract. 相似文献
56.
57.
Sho Haneda M.D. Kouhei Fukushima M.D. Yuji Funayama M.D. Chikashi Shibata M.D. Ken-Ichi Takahashi M.D. Hitoshi Ogawa M.D. Munenori Nagao M.D. Kazuhiro Watanabe M.D. Iwao Sasaki M.D. 《Journal of gastrointestinal surgery》2006,10(7):1051-1059
Our previous studies demonstrated that sodium glucose cotransporter 1 (SGLT-1) was induced in the remnant ileum of total colectomized
rats via the action of factors other than hyperaldosteronism. The aim of the present study was to clarify whether fecal stream
is required for the enhancement of SGLT-1-mediated sodium transport. Twenty-seven pairs of ileal tissues were obtained from
the proximal and distal side, respectively, of loop ileostomy after total proctocolectomy. Mucosae were mounted in an Ussing
chamber to evaluate glucose-coupled sodium transport. Levels of SGLT-1 mRNA in proximal and distal mucosae were compared by
Northern blotting. Villous height and crypt depth were measured to test for correlations between mucosal structure and SGLT-1-mediated
sodium transport or mRNA expression levels. Both glucose-coupled sodium transport and expression of SGLT-1 mRNA were significantly
lower in distal mucosae relative to proximal mucosae. In distal mucosae, villous height, but not crypt depth, was significantly
lower than in proximal mucosae, demonstrating a positive correlation between villous height and SGLT-1 function and expression.
Comparative studies of proximal and distal mucosae demonstrated that in addition to hormonal changes, fecal stream is required
for full induction of the sodium transport system (which includes SGLT-1-mediated transport) in the remnant ileum following
total proctocolectomy.
Presented in part at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois,
May 14–19, 2005 (poster presentation).
This work was supported by Grants-in-Aid for Scientific Research 10557118 and 14657295 from the Ministry of Education, Science
and Culture of Japan to K. Fukushima, and by Kanae Foundation to K. Fukushima. 相似文献
58.
Molecular cloning, characterization, and overexpression of ERG7, the Saccharomyces cerevisiae gene encoding lanosterol synthase. 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
E J Corey S P Matsuda B Bartel 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(6):2211-2215
We report the cloning, characterization, and overexpression of Saccharomyces cerevisiae ERG7, which encodes lanosterol synthase [(S)-2,3-epoxysqualene mutase (cyclizing, lanosterol forming), EC 5.4.99.7], the enzyme responsible for the complex cyclization/rearrangement step in sterol biosynthesis. Oligonucleotide primers were designed corresponding to protein sequences conserved between Candida albicans ERG7 and the related Arabidopsis thaliana cycloartenol synthase [(S)-2,3-epoxysqualene mutase (cyclizing, cycloartenol forming), EC 5.4.99.8]. A PCR product was amplified from yeast genomic DNA using these primers and was used to probe yeast libraries by hybridization. Partial-length clones homologous to the two known epoxysqualene mutases were isolated, but a full-length sequence was found neither in cDNA nor genomic libraries, whether in phage or plasmids. Two overlapping clones were assembled to make a functional reconstruction of the gene, which contains a 2196-bp open reading frame capable of encoding an 83-kDa protein. The reconstruction complemented the erg7 mutation when driven from either its native promoter or the strong ADH1 promoter. 相似文献
59.
J Arisawa J Ikezoe H Yamagami H Naito S Morimoto T Kozuka T Sano K Taniguchi Y Shimazaki H Matsuda 《Nihon Igaku Hōshasen Gakkai zasshi. Nippon acta radiologica》1992,52(1):9-13
Cross sectional echocardiography was used to evaluate the thickness of the ventricular septum in tetralogy of Fallot (TOF). Forty-six patients with TOF and 20 patients with pseudo-truncus arteriosus underwent echocardiography during a five-year period beginning in 1984. Thicknesses of the right ventricular anterior wall (RVAWT), trabecular septum (IVST) and left ventricular posterior wall (LVPWT) were measured in end diastole on parasternal short axis view at the level of the tips of papillary muscles. The ratios of IVST to RVAWT and IVST to LVPWT were assessed. The ratio of IVST to RVAWT was 1.09 +/- 0.15 in the group aged less than 7 years (less than 7 y.o.) and 0.94 +/- 0.15 in the group aged of 7 years or more (greater than = 7 y.o.). The ratios of IVST to LVPWT were 1.10 +/- 0.14 (less than 7 y.o.) and 0.90 +/- 0.15 (greater than = 7 y.o.), respectively. Both ratios were significantly different (p less than 0.01) in the two age groups, and relative thinning of the septum was demonstrated in the older patients. It is speculated that thinning of the interventricular septum is caused by the lower systolic wall stress of the ventricular septum compared with that of the free walls, which is produced under equal systolic pressure of the two ventricles. It is suggested that this thinning is one of the factors that reduces left ventricular function after repair of TOF. 相似文献
60.
Yoshimasa Matsuda Shinya Ono Yosuke Otake Shinya Handa Katsumi Kose Tomoyuki Haishi Shigeto Yamada Chikako Uwabe Kohei Shiota 《Magnetic resonance in medical sciences》2007,6(3):139-146
Using 4 and 8-channel super-parallel magnetic resonance (MR) microscopes with a horizontal bore 2.34T superconducting magnet developed for 3-dimensional MR microscopy of the large Kyoto Collection of Human Embryos, we acquired T(1)-weighted 3D images of 1204 embryos at a spatial resolution of (40 microm)(3) to (150 microm)(3) in about 2 years. Similarity of image contrast between the T(1)-weighted images and stained anatomical sections indicated that T(1)-weighted 3D images could be used for an anatomical 3D image database for human embryology. 相似文献