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   3961篇
  免费   212篇
  国内免费   26篇
耳鼻咽喉   42篇
儿科学   75篇
妇产科学   41篇
基础医学   466篇
口腔科学   109篇
临床医学   229篇
内科学   1097篇
皮肤病学   58篇
神经病学   286篇
特种医学   243篇
外科学   653篇
综合类   27篇
预防医学   136篇
眼科学   149篇
药学   193篇
中国医学   18篇
肿瘤学   377篇
  2023年   20篇
  2022年   77篇
  2021年   99篇
  2020年   69篇
  2019年   88篇
  2018年   107篇
  2017年   79篇
  2016年   84篇
  2015年   90篇
  2014年   138篇
  2013年   167篇
  2012年   242篇
  2011年   271篇
  2010年   181篇
  2009年   146篇
  2008年   228篇
  2007年   241篇
  2006年   244篇
  2005年   222篇
  2004年   184篇
  2003年   197篇
  2002年   170篇
  2001年   76篇
  2000年   65篇
  1999年   67篇
  1998年   33篇
  1997年   45篇
  1996年   35篇
  1995年   30篇
  1994年   22篇
  1993年   15篇
  1992年   49篇
  1991年   43篇
  1990年   29篇
  1989年   37篇
  1988年   31篇
  1987年   39篇
  1986年   33篇
  1985年   37篇
  1984年   26篇
  1983年   17篇
  1982年   8篇
  1981年   20篇
  1980年   11篇
  1979年   15篇
  1978年   9篇
  1977年   11篇
  1976年   10篇
  1975年   7篇
  1968年   5篇
排序方式: 共有4199条查询结果,搜索用时 0 毫秒
31.
BackgroundLow back pain (LBP) is a major problem; it causes significant burden, incurs considerable economic and human costs, and adversely affects the quality of life (QoL). Central sensitivity syndrome (CSS) is known as a group of overlapping conditions that share a common pathophysiological mechanism of central sensitization. Previous studies have shown that CSS is present in several disorders. However, it has been studied for people with presurgical LBP. The purpose of the study was to investigate the proportion of patients with CSS for presurgical LBP and to analyse the association of CSS with clinical symptoms and psychological factors.MethodsData of demographics, the central sensitization inventory (CSI), psychological measures, clinical symptoms of 238 patients with presurgical LBP were evaluated. The patients were divided into two groups depending on the CSI scores (≥40 and < 40). The two groups were compared, and the correlation between the CSI scores and other outcomes was analysed. Furthermore, multiple regression analysis was performed to identify factors contributing to the CSI scores.Results13.0% of participants were CSS. All outcomes were significantly different between the groups and significant associations were found between the CSI scores and all other outcomes. In addition, Pain Catastrophizing Scale (PCS) was most significant associated scale for the CSI scores.ConclusionWe found that certain patients had CSS with presurgical LBP. The CSI scores were significantly associated with the majority of the factors. The PCS was the factor with the most influence on the CSI scores.  相似文献   
32.
Pilon fractures with intact fibula have been associated with low-energy trauma. However, the compression force onto the ankle joint can damage the tibiofibular linkage as in a Maisonneuve fracture. Herein, we describe a case of a patient who had a pilon fracture (AO type 43 C3.2) without a fibular fracture. Three-dimensional preoperative simulation by reduction with the surface registration technique was performed as the fibular length was intact and there was no reference for the tibial length. The preoperative simulation revealed superior fibular head dislocation and shortening of the distal tibia. After emergency external fixation on the day of arrival, a 2-staged surgery was performed. During the first operation, the fibular head was reduced and the tibial posterolateral fragment was fixed to restore the tibia length. During the second operation, medial and anterolateral fragments were fixed in order to reduce joint surface of the distal tibia. In general, proximal fibular head fractures are easily overlooked. In the case of pilon fractures with severe length shortening of the tibia without a fibular fracture, a proximal tibiofibular injury should be suspected.  相似文献   
33.
Overexpression of P-glycoprotein (Pgp) in tumors is one of the major mechanisms which mediates the multidrug resistance (MDR) phenotype. To evaluate the prognostic significance of Pgp in breast cancer, Pgp expression was examined in paraffin-embedded tissue sections of 94 breast cancer specimens by immunohistochemistry. Tissue specimens were obtained by mastectomy without preoperative chemotherapy. UIC2 monoclonal antibody which recognizes an extracellular epitope of human Pgp was employed. Of the 94 breast cancer specimens, 35 (37.2%) were positive for Pgp expression. Pgp expression had no correlation with menopausal or hormone receptor status, axillary lymph node involvement or tumor size. However, a significant correlation was observed between Pgp expression and disease relapse (p = 0.0322). Pgp-positive patients showed a significantly shorter disease-free survival period than Pgp-negative patients by the Kaplan-Meier method (p = 0.0433). These results suggest that immunohistochemical detection of Pgp in breast cancer tissue may have prognostic value after radical operation.  相似文献   
34.
RS-1541, an acyl-derivative of rhizoxin (Fig. 1), is a potent antitumor compound. This agent showed cytotoxicity in vitro on some cultured human tumor cells, although it was less potent than rhizoxin. Rhizoxin exhibited antitumor effects by inhibiting the polymerization of tubulin, whereas RS-1541 did not inhibit tubulin polymerization in vitro. However, cell cycle analysis in vivo showed that the two agents had the same mode of action. The cytotoxicity of RS-1541 was enhanced when the initial cell density of the cells was increased. The cytotoxicity was also enhanced when the membrane fraction of St-4 cells, which were the most sensitive to RS-1541 among the cell lines tested, was added to the target cells. When St-4 cells were incubated with [14C]-RS-1541, significant amounts of [14C]-rhizoxin were produced within the cells. Further fractionation of the crude membrane showed that the activity that enhanced the cytotoxicity of RS-1541 (RS-1541-enhancing activity) belonged to the mitochondrial-lysosomal fraction, not to the microsomal fraction. Both the enhancing activity and the activity that converting [14C]-RS-1541 to [14C]-rhizoxin (RS-1541-converting activity) were inhibited by treatment with chloroquine, an inhibitor of lysosomal function. Cholesterol esterase derived fromCandida cylindracea had RS-1541-enhancingand-converting activities. These data suggest that RS-1541 exerts its cytotoxic action after being converted to rhizoxin within the cells by a lysosomal enzyme such as cholesterol esterase.Abbreviations DMSO Dimethylsulfoxide - PBS(-) Ca2+ Mg2+-free phosphate-buffered saline - HCO60 hydrogenated castor oil polyethylene glycor ether - DMA dimethylacetamide - RSB reticulocyte standard buffer, consisting of 10mM NaCl, 1.5 mM MgCl2, and 10 mM TRIS-HCl, (pH 7.4) - TLC thin-layer chromatography - ara-C 1--D-arabinofuranosylcytosine - LDL low-density lipoprotein  相似文献   
35.
As both tissue inhibitor of metalloproteinases-1 (TIMP-1) and TIMP-2 have been reported to inhibit bone resorption, we examined whether TIMP-1 or TIMP-2 in fetal calf serum (FCS), with which culture media were supplemented, affected osteoclastic bone resorption in vitro. Contrary to our expectation, almost complete suppression of osteoclastic bone resorption was observed when both TIMP-1 and TIMP-2 were removed from the FCS. Bone resorption was, however, almost fully restored by the addition of recombinant TIMPs. TIMPs stimulate bone resorption at significantly lower concentrations (∼ng/ml) than those (∼μg/ml) required to inhibit bone resorption. To understand the mechanism of TIMP-dependent bone resorption, we counted and compared the number of tartrate-resistant acid phosphatase-(TRAP-) positive and multinuclear cells in cultures containing either 10% FCS or TIMP-1-free and/or TIMP-2-free FCS. There was essentially no difference in number among these, suggesting that the TIMP role seems to be related to the functional expression of osteoclasts. Metallo-proteinase inhibitors, either BE16627B[l-N-(N-hydroxy-2-isobutylsuccinynamoyl)-seryl-l-valine] or R94138 {N-methyl-(3S)-2-[(2R)-2-hydroxycarbamoylmethylundecanoyl] hexahydropyridazine-3-carboxamide}, could not replace TIMPs, suggesting that the osteoclast-stimulating activity of TIMPs cannot be ascribed to merely their inhibitory effect on matrix metalloproteinases. Received: Oct. 15, 1998 / Accepted: April 5, 1999  相似文献   
36.
37.
BACKGROUND: A randomized, controlled clinical trial was conducted in 1991 to compare an intravenous megadose of methylprednisolone with a control drug (mecobalamin) for treating acute idiopathic optic neuritis. CASES: Sixty-six cases from 22 clinical centers throughout Japan were examined to evaluate the treatment on visual function parameters, such as visual acuity, visual field, color vision, contrast sensitivity, and critical flicker frequency. OBSERVATIONS: The methylprednisolone pulse treatment group showed faster recovery of visual function, particularly the visual acuity at 1 week (P<.05), Humphrey field analyzer mean deviation at 3 weeks (P<.05), and color vision at 1 week (P<.05). Recovery of contrast sensitivity at several different spatial frequencies was significant in the pulse treatment group at 1 (P<.01), 2 (P<.05), and 4 weeks (P<.05) after the start of treatment. Visual function test results at 12 weeks and 1 year were essentially the same in the two treatment groups. Side effects appeared more frequently in the pulse treatment group than in the control (P<.05). CONCLUSIONS: Pulse treatment does not appear effective for idiopathic optic neuritis even though visual function in the pulse treatment group of this trial recovered more quickly during the initial phase compared to the controls. More effective and specific treatment should be established for optic neuritis.  相似文献   
38.
BACKGROUNDS: Choroideremia is an X-linked hereditary eye disease that causes progressive degeneration of the choroid and retina and frequently leads to legal blindness in later life. Recent molecular genetic studies have revealed mutations involving the Rab escort protein (REP-1) gene localized at Xq 21. CLINICAL FEATURES: The clinical picture and rate of progression may vary among affected individuals in different families and within the same family. Usually, hemizygous males develop night blindness in their teenage years, followed by progressive peripheral visual field constriction and visual disability in late age. Heterozygous female carriers are mostly asymptomatic, but their fundi show characteristic pigment changes in the midperiphery closely resembling the fine mottling observed in the initial stage of the disease in males. MOLECULAR GENETICS: Assessment of the REP-1 gene in European and Japanese choroideremia patients has revealed a wide variety of mutations, including gross deletions and point mutations such as nonsense, frameshift, and splice-site mutations. All these mutations are thought to fail in intact REP-1 protein synthesis. CONCLUSIONS: The recent molecular studies may open a new chapter in the research on choroideremia and provide the groundwork for therapeutic potential as well as diagnosis and genetic counseling.  相似文献   
39.
We reported previously that an angiogenesis inhibitor, E7820, inhibits in vitro tube formation of human umbilical vein endothelial cell through the suppression of integrin alpha2 expression. Here we describe the antiangiogenic and antitumor effects of E7820 in mice and discuss the feasibility of using platelet integrin alpha2 expression on platelets as a biological marker of the efficacy of E7820. Oral administration of E7820 significantly inhibited basic fibroblast growth factor-induced angiogenesis in Matrigel implants and human colon WiDr tumor-induced angiogenesis in a dorsal air sac model. Twice-daily treatment with E7820 clearly inhibited the s.c. tumor growth of seven tumor cell lines derived from human colon, breast, pancreas, and kidney, and completely suppressed the growth of human pancreatic KP-1 and human colon LoVo cell lines. Moreover, E7820 significantly inhibited the growth of KP-1 and human colon tumor Colo320DM cells orthotopically implanted in the pancreas and cecum, respectively. The efficacy of E7820 was comparable in the s.c. and orthotopic transplantation models. Immunohistochemical analyses using anti-CD31 antibody showed that E7820 significantly reduced microvessel density in orthotopically implanted KP-1 tumor. E7820 reduced integrin alpha2 expression on a megakaryocytic cell line, Dami cells, induced by phorbol 12-myristate 13-acetate treatment. It also decreased the expression level of integrin alpha2 on platelets withdrawn from mice bearing s.c. KP-1 tumor at a dosage close to that affording antitumor activity. These data demonstrate that E7820 showed a broad-spectrum antitumor effect in mice through inhibition of angiogenesis and indicate that the decrease of integrin alpha2 on platelets might serve as a biological marker for the antitumor efficacy of E7820.  相似文献   
40.
Background We studied the relationship between the augmentative effects of leucovorin (LV) on 5-fluorouracil (5-FU) and the inhibition rate of thymidylate synthase (TS) activity in Colon 26 murine colon carcinoma cells and L1210 murine leukemia cells. Methods In cytotoxic and TS inhibition studies, cells were exposed for 24 hours to varied concentrations of 5-FU alone or in combination with 1 or 10 μmol/L LV. Cytotoxicity was determined by colony forming efficiency or trypan blue dye exclusion, and TS inhibition rate was determined by [6-3H]-5-FdUMP binding assay. A growth inhibition curve was constructed for longer exposures. Results For tumor cell growth inhibition and cytotoxicity, the augmentative effect was observed when the lower 5-FU concentrations (0.1 μg/mL) were used. There was no difference in the effects between the low (1 μmol/L) and high (10 μmol/L) LV doses. Normally, TS enzyme levels rise acutely when cells are exposed to 5-FU. Both cell lines displayed an increase in TS after exposure to 5-FU. This exposure to 5-FU resulted in the maintenance of free enzyme. LV was able to increase the ternary complex and TS inhibition rate with little induction of TS, however, the inhibition rate was not dependent on doses of LV. Conclusions It was concluded that the augmentative effect of LV at a concentration of 0.1 μg/mL 5-FU occurred at the clinically achievable levels of 1 μmol/L of LV, and there was no difference in the effect between the low and high doses. TS was inhibited effectively by 5-FU and the addition of LV, without a marked induction of TS.  相似文献   
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