全文获取类型
收费全文 | 123819篇 |
免费 | 47928篇 |
国内免费 | 2540篇 |
专业分类
耳鼻咽喉 | 2185篇 |
儿科学 | 4713篇 |
妇产科学 | 1180篇 |
基础医学 | 22391篇 |
口腔科学 | 5745篇 |
临床医学 | 17413篇 |
内科学 | 30818篇 |
皮肤病学 | 8806篇 |
神经病学 | 16079篇 |
特种医学 | 5193篇 |
外国民族医学 | 7篇 |
外科学 | 19118篇 |
综合类 | 5209篇 |
现状与发展 | 4篇 |
一般理论 | 31篇 |
预防医学 | 6736篇 |
眼科学 | 2480篇 |
药学 | 11430篇 |
18篇 | |
中国医学 | 3634篇 |
肿瘤学 | 11097篇 |
出版年
2024年 | 164篇 |
2023年 | 705篇 |
2022年 | 1673篇 |
2021年 | 3901篇 |
2020年 | 6481篇 |
2019年 | 12188篇 |
2018年 | 11719篇 |
2017年 | 12830篇 |
2016年 | 13828篇 |
2015年 | 14542篇 |
2014年 | 14804篇 |
2013年 | 15350篇 |
2012年 | 8922篇 |
2011年 | 8751篇 |
2010年 | 11735篇 |
2009年 | 7525篇 |
2008年 | 4934篇 |
2007年 | 3579篇 |
2006年 | 3407篇 |
2005年 | 3044篇 |
2004年 | 2409篇 |
2003年 | 2430篇 |
2002年 | 2234篇 |
2001年 | 1788篇 |
2000年 | 1505篇 |
1999年 | 912篇 |
1998年 | 435篇 |
1997年 | 399篇 |
1996年 | 298篇 |
1995年 | 242篇 |
1994年 | 236篇 |
1993年 | 161篇 |
1992年 | 165篇 |
1991年 | 177篇 |
1990年 | 148篇 |
1989年 | 121篇 |
1988年 | 102篇 |
1987年 | 81篇 |
1986年 | 77篇 |
1985年 | 47篇 |
1984年 | 36篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 21篇 |
1978年 | 10篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
目的 探讨获取母血中纯化胎儿细胞的有效方法。方法 对 6 0名孕龄 7~ 40周、年龄 2 1~ 30岁的孕妇外周血进行不连续密度梯度离心 ,将分离后的细胞进行制片 ,显微镜下行显微操作分离胎儿有核红细胞 ,进行 Y染色体特异性DYZ1基因的聚合酶链反应 (PCR)。结果 (1)早孕期母血中胎儿 NRBC检出率为 2 0 % ,中孕期母血中胎儿 NRBC检出率为 71.4% ,晚孕期母血中胎儿 NRBC检出率为 6 .6 5 % ,三者之间有显著性差异 (P <0 .0 5 ) ;(2 )用显微操作技术获得的胎儿细胞数量已满足 PCR扩增所需的模板量 ,对胎儿性别进行预测 ,男胎符合率为 11/ 13(84.6 % ) ,性别符合率为 2 6 / 2 8(92 .9% )。结论 不连续密度梯度离心合并显微操作技术对于无创性早期产前基因诊断意义重大。 相似文献
992.
993.
Yapu Cao Kaixiang He Qingqing Li Xin Chen Haiying Mo Zhihao Li Qiaolin Ji Ganpeng Li Gang Du Haiying Yang 《Journal of basic microbiology》2023,63(1):17-25
Gastrodia elata is an achlorophyllous and fully mycoheterotrophic orchid which obtains carbon and other nutrients from Armillaria species in its life cycle. Many researchers suggested that plant hormones, as signing molecules, play a central role in the plant–fungi interaction. In the process of Armillaria gallica 012 m cultivation, both exogenous indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) distinctly stimulated the growth of mycelia in solid media. The differential expression genes (DEGs) of A. gallica 012 m with IAA versus blank control (BK) and IBA versus BK were investigated. The results showed that more than 80% of DEGs of the IAA group were coincident with the DEGs of the IBA group, and more than half of upregulated DEGs and most of the downregulated DEGs of the IAA group coincided with those DEGs of the IBA group. Above research implied that A. gallica 012 m could perceive IAA and IBA, and possess similar responses and signaling pathways to IAA and IBA. The overlapping differential genes of the IAA group and IBA group were analyzed by GO term, and the results showed that several DEGs identified were related to biological processes including positive regulation of the biological process and biological process. The downregulated NmrA-like and FKBP_C genes might be benefit to the growth of mycelia. Those results can explain that exiguous IAA and IBA improved the growth of A. gallica to some extent. We speculate that IAA and IBA are signaling molecules, and regulate the expression of growth-related genes of A. gallica 012 m by the same signaling pathway. 相似文献
994.
995.
Ivan Karel Bohdana Kalvodová Martin Filipec Eva Boháčová Petr Soucek Ctibor Povýšil Jiří Vacík Marie Tlusťáková 《Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie》1997,235(3):186-189
Background: The highly swelling poly(glycerol monomethacrylate) gel (polyGLYMA) and hydrophilic polymer poly(triethylenglycol monomethacrylate (polyTEGMA) were tested as potential viscoelastics for intraopertive use in anterior segment surgery. Methods: PolyGLYMA was implanted into the anterior chamber in 5 rabbits, and 40% polyTEGMA in 16 rabbits. The eyes were enucleated 1 week to 3 months after the operation. The corneal endothelium was examined with specular microscopy, and then the whole eye histopathologically. Results: In all eyes of the polyGLYMA group, the clinical findings were characterized by a marked ciliary injection and severe secondary glaucoma, and the histologic ones by a marked inflammatory infiltration and thickening of Descemet's membrane in the anterior chamber angle. Specular microscopy revealed a decrease in the endothelial cell density and polymorphism of the endothelial cells. In the polyTEGMA group, the anterior segment and the fundus were physiologic all the time, and specular microscopy and histologic findings showed no degenerative and/or inflammatory changes. Conclusions: PolyGLYMA proved unsuitable for intracameral application in rabbits. The new polymer polyTEGMA is characterized by high biologic tolerance after its implantation into the anterior chamber of rabbits. PolyTEGMA 40% might be considered as a potential viscoelastic material in humans. 相似文献
996.
The antioxidant activity ofArtemisia iwayomogi was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The methanol extract
ofA. iwayomogi showed strong antioxidant activity, and thus fractionated with several solvents. The antioxidant activity potential of the
individual fraction was in the order of ethyl acetate>n-butanol>water>chloroform>n-hexane fraction. The ethyl acetate andn-butanol soluble fractions exhibiting strong antioxidant activity were further purified by repeated silica gel and Sephadex
LH-20 column chromatography. Antioxidant chlorogenic acid was isolated as one of the active principles from then-butanol fraction, together with the inactive components, 1-octacosanol, scopoletin, scopolin, apigenin 7,4′-di-O-methylether luteolin 6,3′-di-O-methylether (jaceosidin), apigenin 7-methylether (genkwanin), 2,4-dihydroxy-6-methoxyacetophenone 4-O-β-D-glucopyranoside and quebrachitol. The antioxidant activity of chlorogenic acid was comparable to that of L-ascorbic acid,
which is a well known antioxidant. 相似文献
997.
998.
In order to develop new anti-inflammatory agents having different action mechanisms compared with nonsteroidal and steroidal anti-inflammatory drugs, the culture broths of various actinomycetes isolated from soil were screened using anin vivo mouse ear edma assay and one strain (Streptomyces sp. MT 2705-4: KCTC 8651P) was selected. Activity-guided purification led to the isolation of a polyether compound, dianemycin. Topically, dianemycin showed a potent anti-inflammatory activity in mouse ear edema induced by croton-oil or arachidonic acid. ED(50) value of dianemycin was found to be 0.8 mg/ear compared to 0.4 mg/ear of prednisolone in croton-oil ear edema. However, dianemycin did not show the inhibitory activity in UV-erythema and delayed hypersensitivity reaction. These results indicate that dianemycin is a potential topical anti-inflammatory agent. 相似文献
999.
Twenty seven plant extracts were selected on the basis of ancient literature search for rheumatoid arthritis or similar syndrome. Methanol extract of each plant was prepared and administered orally to rats everyday at a dose of 200 mg/kg/day. Experimental arthritis was induced by subplantar injection of heat-killedMycobacterium butyricum to right hind paw of rats. This treatment provoked swelling of the treated paw in two phases, acute primary swelling and secondary arthritic swelling. An inhibition of secondary swelling was considered to be antiarthritic activity. Several plant methanol extracts such asAkebia quinata (caulis),Ephedra sinica (herba) andSophorae subprostrata (radix) were found to show significant inhibitory activity against secondary swelling at the dose tested. Our results strongly suggested an antiarthritic potential of these plant extracts. 相似文献
1000.
The experimental hepatic cirrhosis was induced either by bile duct ligation (BDL) or by pretreatment with dimethylnitrosamine
(DMNA). The pharmacokinetics of theophylline were studied after a single intravenous or a single oral administration. Using
the ultrafiltration method, protein-drug binding experiments were also carried out. The bilirubin level was several-fold increased
by BDL, but not by DMNA treatment. The albumin content was decreased in both cirrhotic groups. The total clearance (Clt, ml/kg/hr)
of theophylline in both hepatic cirrhosis groups significantly decreased and the terminal half-life (t1/2) in the cirrhotic rats was increased about two-fold after intravenous and oral administration. The volume of distribution
at steady state (Vdss, ml/kg) was increased slightly in the cirrhotic groups. Protein binding in BDL (8.67±4.85%) decreased
about four-folds, but in DMNA (73.00±9.85%) similar result, was observed as compared with the control. Increased free fraction
of theophylline did not increase the volume of distribution in BDL. Therefore decreased total body clearance of theophylline
was mainly due to decreased intrinsic clearance of theophylline in the liver. The absolute bioavailability of theophylline
in these experiments was between 63.8 and 72.8%(66.1% in BDL, 63.8% in Sham operated and Control, 72.8% in DMNA). These results
suggest that in the experimental hepatic cirrhosis model, administration route does not affect the disposition of theophylline. 相似文献