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   36058篇
  免费   2760篇
  国内免费   1204篇
耳鼻咽喉   367篇
儿科学   498篇
妇产科学   383篇
基础医学   5261篇
口腔科学   554篇
临床医学   3782篇
内科学   5442篇
皮肤病学   818篇
神经病学   2417篇
特种医学   1685篇
外国民族医学   5篇
外科学   4096篇
综合类   3479篇
现状与发展   7篇
一般理论   9篇
预防医学   2141篇
眼科学   929篇
药学   3856篇
  19篇
中国医学   1444篇
肿瘤学   2830篇
  2024年   49篇
  2023年   375篇
  2022年   559篇
  2021年   1618篇
  2020年   959篇
  2019年   1000篇
  2018年   1124篇
  2017年   970篇
  2016年   1159篇
  2015年   1653篇
  2014年   2004篇
  2013年   2288篇
  2012年   3206篇
  2011年   3289篇
  2010年   2055篇
  2009年   1701篇
  2008年   2313篇
  2007年   2147篇
  2006年   1916篇
  2005年   1755篇
  2004年   1360篇
  2003年   1160篇
  2002年   946篇
  2001年   765篇
  2000年   792篇
  1999年   596篇
  1998年   269篇
  1997年   226篇
  1996年   171篇
  1995年   167篇
  1994年   143篇
  1993年   105篇
  1992年   165篇
  1991年   173篇
  1990年   141篇
  1989年   107篇
  1988年   88篇
  1987年   80篇
  1986年   76篇
  1985年   48篇
  1984年   33篇
  1983年   34篇
  1982年   30篇
  1981年   19篇
  1980年   21篇
  1979年   29篇
  1978年   18篇
  1977年   15篇
  1976年   13篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
复方胰岛素凝胶剂促进大鼠皮肤溃疡愈合的初步研究   总被引:2,自引:0,他引:2  
周冼苡  周雪雪  曾抗 《中国美容医学》2006,15(2):124-126,i0001
目的:研究复方胰岛素凝胶剂对大鼠皮肤溃疡的促愈合作用,并探讨其可能的作用机制。方法:18只Wistar大鼠背部各制备4个皮肤溃疡模型,共复制溃疡72个,随机将溃疡分为复方胰岛素凝胶治疗组(A组)、凝胶基质对照组(B组)、空白对照组(C组)。以治疗后不同时间点各组溃疡面积、溃疡愈合速度及组织病理学检查评价修复效果。结果:在伤后头10天内,A组溃疡缩小最明显,愈合速度明显快于B组、C组。伤后14天,A组溃疡基本愈合,皮肤结构完整、上皮化较厚;而B、C组溃疡仍未完全愈合,皮肤结构不完整、上皮化较薄。结论:局部应用复方胰岛素凝胶剂对大鼠皮肤溃疡有促愈合作用。  相似文献   
92.
用多粘菌素B琼脂糖亲和层析法清除内毒素,结果表明:5ml多粘菌素B层析柱的总吸附内毒素能力为450 μg,用此法可完全清除体液或各种液体中的内毒素,对血清及腹水中的内毒素也有明显的吸附作用,而其他各种主要成分(除内毒素外)经过处理后无明显改变。去氧胆酸是一种强有力的去污剂,可使已饱和的柱子复活,复活率达85%左右。该方法有简便,可靠,吸附能力大,柱子的复活率高等优点。本方法的建立为内毒素血症的治疗展示了新的前景。  相似文献   
93.
1. The in vivo whole bladder preparation was used to correlate bladder volume with the ability of urinary bladders from control, sucrose-drinking, and diabetic rats to develop pressure in response to bethanechol or nerve stimulation. 2. Both streptozotocin-induced diabetes mellitus and sucrose-diuresis caused an increase in rat urinary bladder capacity and mass. 3. There were significant decreases in the ability of bladders from control rats to develop pressure in response to bethanechol at 1.0 ml intravesical volume, but no change in responsiveness of bladders from sucrose-drinking or diabetic rats at different intravesical volumes. Bladders from sucrose-drinking and diabetic rats developed significantly less pressure in response to bethanechol stimulation at low intravesical volumes than did bladders from control rats. 4. Bladders from diabetic rats developed significantly less pressure in response to 32 Hz stimulation at 0.2 ml intravesical volume compared to larger volumes, however, there were no differences in the responses of bladders from sucrose-drinking or control rats at any intravesical volume. 5. Bladders from control and sucrose-drinking rats had a reduced ability to empty in response to bethanechol and field stimulation at large intravesical volumes. 6. Bladders from 8-week streptozotocin-diabetic rats are able to contract and empty efficiently in response to nerve stimulation and bethanechol over a wide range of intravesical volumes.  相似文献   
94.
5-(2-Acylethynyl)-2,4-dimethoxypyrimidines (3-6) were synthesized in excellent yields from 2,4-dimethoxy-5-[2-(trimethylsilyl)ethynyl]pyrimidine (2) by treatment with acid chlorides in the presence of anhydrous aluminum chloride. Compounds 3-6 were deblocked with chlorotrimethylsilane and sodium iodide in acetonitrile to the corresponding 5-[(2-acyl-1-iodo)vinyl]uracils (7-10), which on treatment with potassium hydroxide in dioxane yielded the corresponding 5-(2-acylethynyl)uracils (11-14). The 5-(2-acylethynyl)uracils were found to be active against Ehrlich ascites carcinoma (EAC) cells in vivo, the most active compounds being 5-(2-benzoylethynyl)uracil (11) and 5-(2-p-toluoylethynyl)uracil (12). The T/C values of 281 and 300 were obtained for compounds 11 and 12, respectively, in the case of mice bearing EAC cells. The 5-(2-acylethynyl)uracils have also shown in vitro activity against CCRF-CEM and L1210/0 tumor cell lines. The lead compound 5-(2-p-toluoylethynyl)uracil effectively inhibited thymidylate synthetase.  相似文献   
95.
Ten (E)-and (Z)-isomers of 2-phenylcyclopropylamine (PCA), 1-Me-PCA, 2-Me-PCA, N-Me-PCA, and N, N-diMe-PCA and fifteeno , m, p isomers of (E)-PCA with substituents of Me, Cl, F, OMe, OH were synthesized in this laboratory and tested for the inhibition of rat brain mitochondrial MAO-A and MAO-B. The effects of substituents, their positions, and stereochemistry on the inhibition were assessed for the compounds with substituents at cyclopropyl and amino groups and QSAR analyses were performed using the potency data of ring-substituted compounds. The best correlated QSAR equations are as follows: pI50=0.804 Π2 Blo−1.069 Blm+0.334 Lp−1.709 HDp+7.897 (r=0.945, s=0.211, F=16.691, p=0.000) for the inhibition of MAO-A; pI50=1.815 π-0.825 Π2 R+0.900 Es2+0.869 Es3+0.796 Es4−0.992 HDp+0.562 HAo+3.893 (r=0.982, s=0.178, F=23.351, p=0.000) for the inhibition of MAO-B. Based on the potency difference between stereoisomers of cyclopropylamine-modified compounds and on QSAR results, it is proposed that the active sites of MAO-A are composed of one deep hydrophobic cavity near para position, two hydrophobic cavities interacting with Me group, a hydrophobic area accomodating phenyl and cyclopropyl backbone, steric boundaries, a hydrogen-acceptor site near para position, and an amino group binding site and that in addition to the same two hydrophobic cavities, hydrophobic area, steric boundaries, hydrogen-acceptor site, and amino group binding site, another steric boundary near para position and a hydrogen donating site near ortho position constitute active sites of MAO-B.  相似文献   
96.
M He  A S Kang  M Hamon  A S Humphreys  M Gani    M J Taussig 《Immunology》1995,84(4):662-668
The heavy chain variable region (VH) and the kappa light chain of the anti-progesterone monoclonal antibody (mAb) DB3, have been expressed as a single-chain three-domain polypeptide, designated VH/K, and secreted into the periplasmic space of Escherichia coli (E. coli). The linker sequence was derived from the VH-CH1 elbow region. The C kappa domain provides a sensitive detection tail for Western blotting and enzyme-linked immunosorbent assay (ELISA). Periplasmic extracts of transformed E. coli contained material that bound progesterone and related steroids with similar specificity and affinity to DB3, and displayed the DB3 idiotype and kappa chain epitopes. Reference to the crystal structure of DB3 suggests that all the characteristics of the combining site interaction with steroids are retained in the bacterially expressed material. Western blotting demonstrated material with a molecular weight equivalent to three domains after reduction, but six domains in the unreduced state, suggesting that the VH/K polypeptide is assembled in the periplasm as a disulphide-bridged dimer. The VH/K construct provides a novel route to expression of antibody combining sites in E. coli for antibody engineering.  相似文献   
97.
The characteristic distribution of calcitonin gone-related peptide(CGRP)inthe small intestine of rats and its changes in acute intestinal radiation sickness(AIRS)were studied with immunocytochemistry(whole mount stretch preparations of the smallintestine and cryostat sections)and radio-immunoassay.It was found that in all the lay-ers of the intestinal walls,there were large amounts of CGRP immunoreactive(CGRP-I)nerve fibers which existed in especiaUy high density in the myenteric,submucosal andmucosal plexuses.There was also a rather high density of the nerves around the smallvessels of the small intestine and the intestinal crypts.Some CGRP-I neurons were seenin the myenteric and submucosal plexuses.In AIRS,the intestinal CGRP showed a dip-hasic change,in a lower level in the 24th h and a higher level in the 48th and 72nd h af-ter irradiation.The results indicate that CGRP may be related to the regulation of the motility,se-cretion,absorption,sensation,and regional blood flow of the gastrointestinal tract.Pro-bably,CGRP is released under the stress of AIRS and participates in the mechanism ofinjury through many ways especially through the influence on the regional blood flowand the increase of the permeability of blood vessels.  相似文献   
98.
99.
目的:研究雌激素对左心室舒张功能的影响。材料和方法:利用多谱勒超声心动图记录了25例健康绝经后妇女二尖瓣口血流频谱,其中15例为雌激素替代治疗组,10例为对照组。所测参数有:舒张早期峰值速度(E),舒张晚期峰值速度(A),E加速度及减速度,并计算E/A比值及心房舒张晚期充盈分数(AFF)。结果:二组间左心室舒张期充盈明显不同,尤其是替代治疗组E/A比值高,AFF低,替代治疗组舒张早期充盈量大于对照组。结论:本研究表明长期雌激素替代治疗可以影响左心室舒张功能。  相似文献   
100.
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