全文获取类型
收费全文 | 27832篇 |
免费 | 1775篇 |
国内免费 | 437篇 |
专业分类
耳鼻咽喉 | 514篇 |
儿科学 | 474篇 |
妇产科学 | 398篇 |
基础医学 | 4619篇 |
口腔科学 | 373篇 |
临床医学 | 2243篇 |
内科学 | 5973篇 |
皮肤病学 | 1202篇 |
神经病学 | 2075篇 |
特种医学 | 1749篇 |
外科学 | 3578篇 |
综合类 | 124篇 |
现状与发展 | 1篇 |
一般理论 | 6篇 |
预防医学 | 994篇 |
眼科学 | 735篇 |
药学 | 2426篇 |
中国医学 | 396篇 |
肿瘤学 | 2164篇 |
出版年
2024年 | 14篇 |
2023年 | 187篇 |
2022年 | 635篇 |
2021年 | 993篇 |
2020年 | 545篇 |
2019年 | 707篇 |
2018年 | 867篇 |
2017年 | 701篇 |
2016年 | 1065篇 |
2015年 | 1456篇 |
2014年 | 1714篇 |
2013年 | 1807篇 |
2012年 | 2668篇 |
2011年 | 2567篇 |
2010年 | 1565篇 |
2009年 | 1329篇 |
2008年 | 1762篇 |
2007年 | 1547篇 |
2006年 | 1352篇 |
2005年 | 1279篇 |
2004年 | 974篇 |
2003年 | 871篇 |
2002年 | 803篇 |
2001年 | 416篇 |
2000年 | 420篇 |
1999年 | 307篇 |
1998年 | 147篇 |
1997年 | 121篇 |
1996年 | 95篇 |
1995年 | 58篇 |
1994年 | 62篇 |
1993年 | 52篇 |
1992年 | 86篇 |
1991年 | 106篇 |
1990年 | 71篇 |
1989年 | 94篇 |
1988年 | 82篇 |
1987年 | 69篇 |
1986年 | 52篇 |
1985年 | 45篇 |
1984年 | 26篇 |
1983年 | 30篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 30篇 |
1979年 | 40篇 |
1978年 | 31篇 |
1977年 | 37篇 |
1976年 | 15篇 |
1971年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Lee YJ Nam SW Seo DW Ahn SH Ko YK Sung DS Han JW Hong SY Lee HW 《Archives of pharmacal research》1997,20(3):239-246
In the present study, liver regeneration rate (%) was increased up to 70% 3 days after partial hepatectomy (PH). Nitric oxide
synthase (NOS) activity in liver tissue as well as serum nitrite/nitrate content had no timed response, revealing no significant
difference between shamoperated and partially hepatectomized rat liver. Contents of free methylarginines in liver tissue were
increased biphasically in a time-dependent manner after PH. However, those in serum did not exhibit the same patterns as in
liver. Taken together, the results suggest that NG-monomethyl-L-arginine (MMA) and NG, NG-dimethylarginine (DMA) play a role in inhibiting nitric oxide (NO) synthesis in regenerating rat liver because the increase
of their contents was synchronized with NOS expression. 相似文献
82.
By human intestinal bacteria, saikosaponin c was transformed to four metabolites, prosaikogenin E1 (E1) prosaikogenin E2 (E2), prosaikogenin E3 (E3) and saikogenin E. Metabolic time course of saikosaponin c was as follows; in early time, saikosaponin c was converted to E1 and E2, and then these were transformed to saikogenin E via E3. Also, this metabolic pathway was similar to the metabolism of saikosaponin c by rat intestinal bacteria.Bacteroides JY-6 andBacteroides YK-4, the bacteria isolated from human intestinal bacteria, could transform saiko-saponin c to E via E1 (or E2) and E3. However, these bacteria were not able to directly transform E1 and E2 to saikogenin E. Naringin was mainly transformed to naringenin by human intestinal bacteria. The minor metabolic pathway transformed naringin to naringenin via prunin. By JY-6 or YK-4, naringin was metabolized to naringenin only via prunin. 相似文献
83.
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
84.
85.
86.
True histiocytic lymphoma of the esophagus in an HIV-positive patient: an ultrastructural study 总被引:1,自引:0,他引:1
A 56-year-old white woman, seropositive for human immunodeficiency virus for 18 months without signs of acquired immunodeficiency syndrome, presented with retrosternal pain and progressive dysphagia secondary to an exophytic esophageal mass. Biopsies of the tumor showed a malignant neoplasm composed of pleomorphic, noncohesive cells growing in a diffuse, sheet-like fashion. Immunohistochemically, tumor cells were nonreactive with epithelial, lymphoid, neural, and monocyte/macrophage markers. Despite the noncontributory immunohistochemical findings, ultrastructural study of the tumor cells revealed convincing histiocytic features. Individual cells possessed long, slender filopodial projections, prominent Golgi apparatus, residual bodies, rare lysosomes, and prelysosomes. Immunoglobulin heavy chain and T-cell receptor gamma gene rearrangement studies detected no evidence of a clonal gene rearrangement. The patient responded poorly to chemotherapy and died 5 months after her initial symptom of dysphagia. 相似文献
87.
We present a patient with pancreatoblastoma along with a discussion of various cross-sectional imaging features. The tumor was a large multilocular cystic mass with solid components in the left retroperitoneal space. There were fine internal echoes on ultrasonography, and the signal intensity was high on both T1- and T2-weighted MR images in most of the locules, suggesting the presence of hemorrhagic debris. Among the various retroperitoneal organs displaced by the tumor, only the pancreatic tail was inseparable from the mass, suggesting that the pancreatic tail was the origin of the tumor. Pancreatoblastoma should be included in the differential diagnosis when a large left upper quadrant mass with these imaging features is seen in infants and young children. 相似文献
88.
The role of genetics in Parkinson's disease (PD), previously controversial, is now supported by several studies. A major breakthrough has been the discovery of a single gene defect in familial Parkinson's disease. A single base pair change at position 209 from G to A (G209A) in the fourth exon of the alpha-synuclein gene has been identified in cases of familial PD. We looked for this mutation in 65 cases of sporadic PD in Taiwan Chinese patients but found none of these patients with this mutation. We conclude that mutation of G209A in the alpha-synuclein gene plays no role in sporadic PD among Taiwan Chinese. 相似文献
89.
The present study was designed to evaluate whether functional impairment and/or protein expression of constitutive nitric oxide synthase (cNOS; endothelial NOS [eNOS] and neuronal NOS[nNOS]) was involved in impairment of endothelium-dependent relaxation of cavernous smooth muscle in hypercholesterolemic rabbits. New Zealand White rabbits were randomly divided into control and experimental groups. The control group (n=20) received a regular diet, while the two experimental groups (n=20 for each) were fed a 2% cholesterol diet for 4 and 8 weeks, respectively. We conducted isometric tension studies with endothelium-dependent and endothelium-independent vasodilators with or without preincubation with L-arginine and nonadrenergic, noncholinergic (NANC)-selective electrical field stimulation on isolated strips of corpus cavernosum. Expression of cNOS (eNOS and nNOS) protein was assessed by Western blot analysis. cNOS activities in both cytosolic and particulate fractions were measured by determining the conversion of L-[U-14C] arginine to L-[U-14C] citrulline. Blood levels of cholesterol were significantly higher (P < 0.01) in the experimental groups than in the control group. The relaxation responses to endothelium-dependent agents (acetylcholine and adenosine 5'-diphosphate [ADP]) were significantly reduced (P < 0.05) in both experimental groups, regardless of their incubation with L-arginine, compared with the control group. However, no differences were found among the three groups in the relaxation response to endothelium-independent agents (papaverine and nitroprusside) and to NANC-selective electrical field stimulation. There was no difference in immunoreactive nNOS from cytosolic and particulate fractions between the cavernous tissues of the control and experimental groups. nNOS protein levels in the particulate fractions were markedly lower than in the cytosolic fractions. The particulate cNOS activity was significantly decreased (P < 0.05) in the experimental groups compared with the control group, while the cytosolic cNOS activity in the experimental groups was not different from that found in the control group. Therefore, it is concluded that functional impairment of eNOS, rather than of nNOS, may lead to impairment of cavernous smooth muscle relaxation in response to endothelium-mediated stimuli in hypercholesterolemic rabbits. 相似文献
90.
Hepatitis C virus (HCV) nonstructural (NS) proteins appeared to be important targets for HCV vaccine development, since NS-specific T-helper-cell responses are associated with clearance from acute HCV infection. In this report, we have constructed a plasmid, pTV-NS345, that encodes the HCV NS3, NS4 and NS5 proteins (NS345) and a bicistronic plasmid, PTV-NS345/GMCSF, in which the HCV NS345 polyprotein and GMCSF are translated independently. Intramuscular inoculation with pTV-NS345 plasmid DNA into the Buffalo rats generated both antibody and T-cell proliferative responses to each NS protein. The expression of GMCSF, together with HCV NS345 proteins, appeared to significantly increase T-cell proliferative responses. In particular, the inoculation of a bicistronic plasmid generated higher T-cell proliferative responses to each NS protein than did the coinjection of two separate plasmids, pTV-NS345 and pTV-GMCSF. These results demonstrate that the codelivery of GMCSF augmented HCV NS345-specific cellular immunity and that the intensity of the immunity was differed depending on how GMCSF gene is codelivered. 相似文献