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   44302篇
  免费   2118篇
  国内免费   395篇
耳鼻咽喉   488篇
儿科学   1000篇
妇产科学   493篇
基础医学   5896篇
口腔科学   730篇
临床医学   2650篇
内科学   11512篇
皮肤病学   1027篇
神经病学   3310篇
特种医学   1806篇
外科学   7703篇
综合类   172篇
一般理论   6篇
预防医学   1128篇
眼科学   1001篇
药学   2761篇
中国医学   170篇
肿瘤学   4962篇
  2023年   213篇
  2022年   403篇
  2021年   893篇
  2020年   479篇
  2019年   666篇
  2018年   943篇
  2017年   712篇
  2016年   901篇
  2015年   984篇
  2014年   1269篇
  2013年   1598篇
  2012年   2590篇
  2011年   2875篇
  2010年   1637篇
  2009年   1512篇
  2008年   2726篇
  2007年   2946篇
  2006年   2973篇
  2005年   2977篇
  2004年   3088篇
  2003年   3131篇
  2002年   3105篇
  2001年   490篇
  2000年   414篇
  1999年   566篇
  1998年   766篇
  1997年   646篇
  1996年   603篇
  1995年   507篇
  1994年   452篇
  1993年   493篇
  1992年   310篇
  1991年   296篇
  1990年   243篇
  1989年   240篇
  1988年   242篇
  1987年   183篇
  1986年   149篇
  1985年   156篇
  1984年   164篇
  1983年   126篇
  1982年   126篇
  1981年   154篇
  1980年   128篇
  1979年   84篇
  1978年   102篇
  1977年   79篇
  1976年   67篇
  1975年   54篇
  1974年   41篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
This study was conducted to identify patterns of carpal instability in the rheumatoid wrist. One hundred patients with proven rheumatoid arthritis were randomly chosen, and posteroanterior and lateral radiographs of right wrists were taken. The most common isolated pattern was volar intercalated segmental instability, apparent in 16 wrists, while nine wrists had scapholunate dissociations. Larsen grading scores revealed a correlation between disease duration, carpal height ratio, and ulnar translocation index. In the early stages of disease, the scapholunate angle was significantly increased and the lunate rotated volarly due to loosening of the intrinsic carpal ligament. In later phases, the capitolunate angle significantly increased and the capitate rotated dorsally. Patterns of carpal instability in rheumatoid wrists seem to be complicated, involving combined laxity of the intrinsic and extrinsic carpal ligaments.No benefits have been received from a commercial party directly or indirectly related to the subject of this article.An erratum to this article can be found at  相似文献   
962.
963.
A detailed comparison was made of the bile acid composition in gallstones (brown pigment stones) and paired bile and liver from both affected and unaffected lobes by gallstones, which were taken at operation from 16 patients with hepatolithiasis, with the aim of elucidating whether stone formation is derived from possible local disturbances limited to intrahepatic bile ducts. Brown pigment stones in the intrahepatic bile ducts, most of which were accompanied by bile with high cholesterol saturation, had significantly more cholesterol, and less calcium bilirubinate and bile acid than those found in the extrahepatic bile ducts. Intrahepatic gallstones had significantly lower amounts of secondary and unconjugated bile acids, the bile acids modified by bacterial intervention, than extrahepatic stones. Bile specimens from both affected and unaffected lobes showed significantly increased molar percentages of cholesterol and decreased percentages of bile acids than bile from controls. In contrast, liver specimens from both lobes showed significantly higher concentrations of total bile acids. Secondary bile acids were present in a much lower proportion in bile and liver from both lobes than in bile and liver from controls. On the other hand, unconjugated bile acids were present in a much higher proportion in bile and liver from patients and only in negligible amounts in bile from controls. Furthermore, the plasma levels of mevalonate and those of 7α-hydroxy-4-cholestene-3-one were found to be significantly higher and lower in patients than in controls, respectively, indicating that in hepatolithiasis cholesterol synthesis might increase and bile acid synthesis might decrease in the liver. These findings suggested that alterations of bile acid composition in gallstones, bile, and liver of patients with hepatolithiasis may be attributed to not only secondary changes resulting from local disturbances limited to intrahepatic bile ducts but also possible primary alterations of hepatocyte metabolism, such as bile acid conjugation and primary defects in cholesterol and bile acid synthesis.  相似文献   
964.
965.
Anandamide induces necrosis in primary hepatic stellate cells   总被引:7,自引:0,他引:7  
The endogenous cannabinoid anandamide (AEA) is a lipid mediator that blocks proliferation and induces apoptosis in many cell types. Although AEA levels are elevated in liver fibrosis, its role in fibrogenesis remains unclear. This study investigated effects of AEA in primary hepatic stellate cells (HSCs). Anandamide blocked HSC proliferation at concentrations of 1 to 10 micromol/L but did not affect HSC proliferation or activation at nanomolar concentrations. At higher concentrations (25-100 micromol/L), AEA rapidly and dose-dependently induced cell death in primary culture-activated and in vivo-activated HSCs, with over 70% cell death after 4 hours at 25 micromol/L. In contrast to treatment with Fas ligand or gliotoxin, AEA-mediated death was caspase independent and showed typical features of necrosis such as rapid adenosine triphosphate depletion and propidium iodide uptake. Anandamide-induced reactive oxygen species (ROS) formation, and an increase in intracellular Ca(2+). Pretreatment with the antioxidant glutathione or Ca(2+)-chelation attenuated AEA-induced cell death. Although the putative endocannabinoid receptors CB1, CB2, and VR1 were expressed in HSCs, specific receptor blockade failed to block cell death. Depletion of membrane cholesterol by methyl-beta-cyclodextrin inhibited AEA binding, blocked ROS formation and intracellular Ca(2+)-increase, and prevented cell death. In primary hepatocytes, AEA showed significantly lower binding and failed to induce cell death even after prolonged treatment. In conclusion, AEA efficiently induces necrosis in activated HSCs, an effect that depends on membrane cholesterol and a subsequent increase in intracellular Ca(2+) and ROS. The anti-proliferative effects and the selective killing of HSCs, but not hepatocytes, indicate that AEA may be used as a potential anti-fibrogenic tool.  相似文献   
966.
Objectives: To determine the tentative diagnostic criteria and disease severity classification for Castleman disease (CD) and describe the clinical and pathologic features among human herpesvirus 8 (HHV-8) negative idiopathic multicentric CD (iMCD) in the Japanese population.

Methods: We established the working groups for the research of CD in Japan and had meetings to discuss and define the tentative diagnostic criteria and disease severity classification for CD. We subsequently analyzed 142 patients classified into iMCD by using the nationwide Japanese patient registry.

Results: We proposed the preliminary diagnostic criteria and disease severity classification for CD based on our discussion. In addition, we made a proposal for the disease activity score. We identified clinical and pathological features of patients with iMCD diagnosed by these diagnostic criteria. In the disease severity classification, 37, 33 and 30% patients were categorized into mild, moderate and severe diseases, respectively.

Conclusion: This is the first proposal for diagnosis and classification of CD by the Japanese group. Further studies are required to validate whether they can distinguish CD from other inflammatory diseases and to determine their sensitivity and specificity.  相似文献   

967.
OBJECTIVE: In the present study, we delivered vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) gene to a rabbit model of hind limb ischemia utilizing an ex vivo method of gene transfer, and evaluated the functional performance of the developed collateral vessels. METHOD: The left femoral artery of a male Japanese White rabbit was excised to induce limb ischemia, and a section of skin was resected for culture of auto-fibroblasts. Twenty days later, the VEGF gene, bFGF gene or beta-galactosidase gene (LacZ) was adenovirally transferred to the cultured auto-fibroblasts (5x10(6) cells), and the next day, a pair of specifically infected fibroblasts (total 1x10(7) cells) was injected via the left internal iliac artery of the same rabbit. Pairs of transferred genes into the fibroblasts were as follows: LacZ/LacZ (control group), VEGF/LacZ (VEGF group), bFGF/LacZ (FGF group) and VEGF/bFGF (combination group). Twenty-eight days after cell administration, collateral development and its function were evaluated. RESULTS: Calf blood pressure ratio, resting blood flow of the left iliac artery and capillary density of ischemic muscle showed similar degrees of angiogenic effects in the VEGF and FGF groups, which were significantly greater than those in the control group. On the contrary, angiographic score, collateral conductance and smooth muscle cell (SMC)-positive vessel density in the FGF group were significantly greater than those in the VEGF group. In the combination group, collateral conductance showed synergistic effects, and in vivo blood flow and smooth muscle cell-positive vessel density revealed additive effects of VEGF and bFGF. CONCLUSION: These findings suggested that bFGF-induced collateral development exceeded VEGF-induced collateral development in the induction of arteriogenesis, and that combined gene delivery of VEGF and bFGF produced additive or synergistic effects of collateral development as compared with the effects induced by transfer of each gene alone.  相似文献   
968.
969.
Plasmapheresis for the treatment of hypertriglyceridemia has previously been performed in patients with sudden onset severe hypertriglyceridemia and acute pancreatitis; however, only a few reports of this procedure have been published. We report here on a case showing severe hypertriglyceridemia during asparaginase (Asp) treatment for acute lymphocytic leukemia (ALL), and give an overview of a lipid‐lowering apheresis therapy. To prevent the complication of pancreatitis due to hypertriglyceridemia, we performed plasma exchange (PE) three times using fresh frozen plasma. PE remarkably reduced both serum triglyceride and total cholesterol levels from 5430 mg/dL to 403 mg/dL and from 623 mg/dL to 204 mg/dL, respectively. The causes of severe hyperlipidemia in this patient were considered to include: the Asp treatment for ALL, and a genetic background with a heterozygote of familial lipoprotein lipase (LPL) defect syndrome, because the patient's plasma LPL level after intravenous heparin injection was low at 137 ng/mL. Hence, PE using fresh frozen plasma may be useful not only to remove lipoproteins, but also to supply defective factors, such as LPL, in similar cases.  相似文献   
970.
Siba, a new platelet-specific alloantigen involved in a case of platelet transfusion refractoriness is reported. The IgG platelet alloantibody was detected in a multiply transfused patient of Japanese extraction (Sib), by the presence of HLA antibodies. After transfusion of HLA-compatible platelets, the patient suffered from refractoriness. Adsorption studies with pooled lymphocytes showed that the serum contained anti-platelet activity. Family studies indicate that Siba is inherited as an autosomal codominant trait and separate from HLA and Baka. As of this report, segregation from Zw(PlA) and Yuk (Pen) antigen systems have not yet been determined. The gene frequency of Siba in the Japanese population is estimated to be 0.136.  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