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   22469篇
  免费   1105篇
  国内免费   117篇
耳鼻咽喉   149篇
儿科学   348篇
妇产科学   373篇
基础医学   3383篇
口腔科学   534篇
临床医学   1373篇
内科学   5448篇
皮肤病学   419篇
神经病学   1963篇
特种医学   864篇
外科学   3540篇
综合类   98篇
一般理论   1篇
预防医学   575篇
眼科学   658篇
药学   1665篇
中国医学   72篇
肿瘤学   2228篇
  2023年   103篇
  2022年   180篇
  2021年   319篇
  2020年   252篇
  2019年   294篇
  2018年   350篇
  2017年   280篇
  2016年   359篇
  2015年   365篇
  2014年   503篇
  2013年   628篇
  2012年   983篇
  2011年   1040篇
  2010年   578篇
  2009年   484篇
  2008年   983篇
  2007年   995篇
  2006年   951篇
  2005年   1058篇
  2004年   1126篇
  2003年   1057篇
  2002年   1061篇
  2001年   847篇
  2000年   856篇
  1999年   808篇
  1998年   329篇
  1997年   270篇
  1996年   213篇
  1995年   209篇
  1994年   199篇
  1993年   181篇
  1992年   574篇
  1991年   481篇
  1990年   491篇
  1989年   505篇
  1988年   433篇
  1987年   370篇
  1986年   380篇
  1985年   369篇
  1984年   267篇
  1983年   201篇
  1982年   91篇
  1979年   171篇
  1978年   135篇
  1977年   124篇
  1974年   92篇
  1972年   91篇
  1971年   100篇
  1968年   97篇
  1967年   91篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
Coiled bodies and interfascicular threads are conspicuous white matter abnormalities of brains of patients with progressive supranuclear palsy (PSP). Both structures are argyrophilic and immunoreactive for the microtubule-binding protein tau. This report concerns the ultrastructural localization of interfascicular threads and their relationship to coiled bodies in five PSP patients. We showed for the first time that abnormal tubules with a 13- to 15-nm diameter and fuzzy outer contours were the common structures of coiled bodies in the oligodendroglial perikarya and of interfascicular threads. Moreover, the tubules were immunolabeled by anti-tau antibodies. The abnormal tau-positive tubules of interfascicular threads were located in the inner loop of the myelin sheath. Our study further indicated that the thread-like structures in the white matter comprised, at least in part, oligodendroglial processes, and that they were also present in gray matter. We consider that the formation of coiled bodies in the perikarya and of interfascicular threads represents a common cytoskeletal abnormality of the oligodendroglia of PSP patients. Moreover, even though the white matter alterations of PSP resemble those of corticobasal degeneration, there are certain ultrastructural differences in the abnormal oligodendroglial tubules of the two diseases. Received: 4 October 1996 / Accepted: 6 December 1996  相似文献   
33.
Pituitary stalk meningioma: case report   总被引:1,自引:0,他引:1  
We report a 45-year-old woman with a meningioma which was in contact with only the pituitary stalk on MRI. As the pituitary stalk has no dura mater, we suggest this tumour may have originated from the arachnoid membrane of the pituitary stalk. Though some reports have shown that meningiomas can arise from sites lacking a dural component, this is the first report of a meningioma originating from the pituitary stalk. Received: 21 December 1995 Accepted: 26 February 1996  相似文献   
34.
35.
Clinical evaluation of ceftibuten (CETB, 7432-S) was performed in 20 patients with acute bronchitis. They were consisted of 10 males and 10 females aged from 20 to 80 years old. CETB was given orally in daily dose of 300 mg (18 cases) or 600 mg (2 cases) in three divided portions. The duration of administration was 3 to 14 days. Especially they were given for 7 days in 16 cases. A total of 11 strains comprising 4 strains of Staphylococcus aureus, 2 strains of beta-Streptococcus and 1 strain each of Streptococcus pneumoniae, Branhamella catarrhalis, Klebsiella oxytoca, Serratia marcescens, Acinetobacter lwoffii were identified from sputa before administration. All of the above bacteria were eradicated but, in 1 case, a strain of Streptococcus pyogenes appeared after the treatment (eradication ratio = 100%). The clinical efficacy rate was 100%: Responses were excellent in 3 cases and good in 17 cases. There was no side effect and no abnormal changes in laboratory test results. From the avobe results, it is concluded that CETB is effective, safe and useful new oral cephem on acute bronchitis.  相似文献   
36.
The regulation of interleukin-1 receptor (IL-1R) mRNA expression by IL-1 in a human lung fibroblast cell line (TIG-1) was investigated. After 2 h of stimulation with human recombinant IL-1 alpha or IL-1 beta, the levels of T cell/fibroblast-type IL-1R mRNA increased, and the elevation was sustained for at least 72 h. IL-1 also stimulated synthesis of prostaglandin E2 (PGE2) and secondary cAMP accumulation. Exogenously added PGE2 increased the levels of both IL-1R mRNA and intracellular cAMP. Forskolin, cholera toxin and 8-Bromo adenosine (8-Br-cAMP) all increased IL-1R mRNA levels. Indomethacin blocked IL-1 stimulation of IL-1R mRNA expression, PGE2 production and cAMP. 125I-labeled IL-1 alpha-binding studies showed that this cell line expresses 2.6 x 10(4) IL-1R per cell with a Kd of 5.1 x 10(-10) M. After treatment of the cells with IL-1, the level of IL-1R increased over that of control cells. PGE2 also increased IL-1R without alteration in its affinity. Cross-linking experiments indicate that this cell line expresses the 80-kDa receptor molecule before and after treatment with PGE2; the molecular mass corresponds to the T cell/fibroblast type I IL-1R. These results indicate that IL-1 does not directly stimulate expression of IL-1R mRNA or cell surface IL-1R, but only indirectly by stimulation of endogenous PGE2.  相似文献   
37.
We report the results and complications of 103 consecutive patients who underwent percutaneous removal of renal and ureteral stones. The overall clinical success rate was 80.6%. For the recent 33 cases in which UL-arm fluoroscopy was used, however, the success rate was as high as 87.9%, which was considered to be due to easier establishment of percutaneous direct access. The most common complications were bleeding (18.5%), extravasation (15.5%) and fever (9.7%). Four cases with significant bleeding required arteriography, but there were no sign of arteriovenous fistula nor pseudoaneurysms in any cases. To study renal parenchymal damage in the percutaneous procedures, plasma renin activities (PRA) were compared in 54 cases after six months. However, significant elevation of PRA did not occur in any case.  相似文献   
38.
Background: Contraction of airway smooth muscle is regulated by receptor-coupled mechanisms that control the force developed for a given cytosolic calcium concentration (i.e., calcium sensitivity). Halothane antagonizes acetylcholine-induced increases in calcium sensitivity by inhibiting GTP-binding (G)-protein pathways. The authors tested the hypothesis that hexanol, like halothane, inhibits agonist-induced increases in calcium sensitivity in airway smooth muscle by inhibiting G-protein pathways.

Methods: Calcium sensitivity was assessed using [alpha]-toxin-permeabilized canine tracheal smooth muscle. In selected experiments, regulatory myosin light chain phosphorylation was also determined by Western blotting in the presence and absence of 10 mm hexanol and/or 100 [mu]m acetylcholine.

Results: Hexanol (10 mm) and halothane (0.76 mm) attenuated acetylcholine-induced calcium sensitization by decreasing regulatory myosin light chain phosphorylation during receptor stimulation. Hexanol also inhibited increases in calcium sensitivity due to direct stimulation of heterotrimeric G-proteins with tetrafluoroaluminate but not with 3 [mu]m GTP[gamma]S, consistent with prior results obtained with halothane. In contrast, in the absence of receptor stimulation, both compounds produced a small increase in calcium sensitivity by a G-protein-mediated increase in regulatory myosin light chain phosphorylation that was not affected by pertussis toxin treatment.  相似文献   

39.
Background: Some anesthetics relax airway smooth muscle in part by inhibiting acetylcholine-induced increases in Ca2+ sensitivity, an effect associated with inhibition of guanosine nucleotide exchange at the [alpha] subunit of the Gq/11 (G[alpha]q/11) heterotrimeric G protein. This study tested the hypothesis that these anesthetic effects are not unique to the muscarinic receptor but are a general property of the heptahelical receptors that increase Ca2+ sensitivity in airway smooth muscle.

Methods: Anesthetic effects on agonist-induced increases in Ca2+ sensitivity were measured in porcine airway smooth muscle strips permeabilized with S. aureus [alpha]-toxin. Anesthetic effects on basal (without agonist stimulation) and agonist-promoted G[alpha]q/11 guanosine nucleotide exchange were determined in crude membranes prepared from porcine airway smooth muscle. The nonhydrolyzable, radioactive form of guanosine 5'-triphosphate was used as the reporter for nucleotide exchange at G[alpha]q/11.

Results: Acetylcholine, endothelin-1, and histamine caused a concentration-dependent increase in Ca2+ sensitivity. Halothane (0.67 +/- 0.07 mm) and hexanol (10 mm) significantly inhibited the increase in Ca2+ sensitivity induced by each agonist. Each agonist also caused a time- and concentration-dependent increase in G[alpha]q/11 nucleotide exchange. Neither anesthetic had an effect on basal G[alpha]q/11 nucleotide exchange, whereas halothane and hexanol significantly inhibited the increase in G[alpha]q/11 nucleotide exchange promoted by each agonist.  相似文献   

40.
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