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   5629篇
  免费   375篇
  国内免费   15篇
耳鼻咽喉   37篇
儿科学   134篇
妇产科学   82篇
基础医学   878篇
口腔科学   193篇
临床医学   561篇
内科学   1209篇
皮肤病学   80篇
神经病学   859篇
特种医学   164篇
外科学   662篇
综合类   27篇
一般理论   1篇
预防医学   338篇
眼科学   38篇
药学   291篇
中国医学   5篇
肿瘤学   460篇
  2022年   38篇
  2021年   75篇
  2020年   76篇
  2019年   78篇
  2018年   100篇
  2017年   76篇
  2016年   116篇
  2015年   135篇
  2014年   131篇
  2013年   202篇
  2012年   247篇
  2011年   280篇
  2010年   156篇
  2009年   151篇
  2008年   228篇
  2007年   270篇
  2006年   241篇
  2005年   273篇
  2004年   242篇
  2003年   216篇
  2002年   219篇
  2001年   155篇
  2000年   140篇
  1999年   155篇
  1998年   79篇
  1997年   61篇
  1996年   83篇
  1995年   55篇
  1994年   38篇
  1993年   46篇
  1992年   95篇
  1991年   111篇
  1990年   110篇
  1989年   92篇
  1988年   97篇
  1987年   108篇
  1986年   91篇
  1985年   90篇
  1984年   74篇
  1983年   68篇
  1982年   53篇
  1979年   59篇
  1978年   55篇
  1977年   46篇
  1976年   43篇
  1975年   46篇
  1974年   57篇
  1973年   44篇
  1972年   47篇
  1971年   52篇
排序方式: 共有6019条查询结果,搜索用时 640 毫秒
91.
Summary The principle of bowel detubularization to decrease peristaltic pressure and increase reservoir capacity is applied in contemporary continent urinary diversions. The process of detubularization and refashioning of the spatulated bowel segment approximates 1 of operating time and is the most time-consuming aspect of pouch construction. The employment of devices applying absorbable staples (absorbable staplers) has substantially reduced the time required to fashion bowel reservoirs. This article reviews the adaptation of the absorbable stapler to continent urinary diversion using small- and large-bowel segments.  相似文献   
92.
Summary The possibility that -adrenoceptor blockers, especially 1-selective agents might inhibit platelet function is of considerable interest, as this might be of pathophysiological importance in cardiovascular diseases. Platelet function, however, is difficult to assess and in vivo related data are scarce.The effect of one week of treatment with metoprolol 200 mg/day on platelet aggregability during mental stress (colour word conflict test; CWT) and low and high dose adrenaline infusions has been evaluated in a double-blind, placebo-controlled, cross-over study in 10 healthy male volunteers. Platelet function in vivo was assessed using ex vivo filtragometry, and the urinary excretions of -thromboglobulin (HMW -TG) and 11-dehydro-TxB2 (a thromboxane metabolite). Conventional in vitro aggregometry and the urinary levels of 2,3-dinor-6-keto-PGF1 (a prostacyclin metabolite) were also studied.During the interventions there was increased platelet aggregability in vivo, as filtragometry readings were shortened by 41±11% during high dose adrenaline infusion, urinary HMW -TG levels increased and urinary 11-dehydro-TxB2 tended to increase. In contrast, platelet sensitivity to ADP in vitro was reduced. The urinary 2,3-dinor-6-keto-PGF1 levels were increased during the interventions.Despite the cardiovascular and biochemical signs of -adrenoceptor blockade at rest and during the interventions, metoprolol failed to influence platelet function in vivo, as measured by ex vivo filtragometry, or urinary HMW -TG or 11-dehydro-TxB2 levels. It tended rather to enhance the stress response measured by ex vivo filtragometry. Platelet aggregability in vitro and urinary 2,3-dinor-6-keto-PGF1 levels were not altered by metoprolol.Thus, metoprolol was not found to reduce platelet aggregability in healthy male volunteers either at rest or during sympatho-adrenal activation. The effect of treatment may still differ in patients; studies in patients with ischaemic heart disease are under way.  相似文献   
93.
Integration in trigeminal premotor interneurones in the cat   总被引:1,自引:0,他引:1  
Seventy-one (n = 71) premotor interneurones have been localized by extracellular recordings within the subnucleus-gamma of the oral nucleus of the spinal trigeminal tract (NVspo-gamma) in nineteen chloralose anaesthetized cats. The neurons were antidromically activated by microstimulation (minimum = 3 microA) applied to the digastric motoneurone subnucleus of the trigeminal motor nucleus. Fifty-one (n = 51) of the interneurones were discharged from the ipsi- and nineteen (n = 19) from the contralateral digastric subnucleus. One neurone out of four tested was antidromically activated from both stimulation sites suggesting a bifurcated axon. The identified premotor neurones had a unique convergence profile of oral and perioral primary afferents. Latency calculations indicated that at least 55% of these interneurones were monosynaptically activated by low stimulus strength applied to the inferior alveolar (minimum = 1.0 T) and/or the lingual nerve (minimum = 1.0 T). The thresholds for evoking the neuronal discharges coincided statistically with those required to evoke a jaw opening reflex response by stimulation of the same nerves. It is suggested that the specific group of NVspo-gamma interneurones under different contexts mediates the disynaptic reflex and participates in the centrally and reflexly evoked "patterning" adjustments of the digastric jaw opening motoneurones during ongoing jaw movements. A companion paper reports the convergence of descending cortical, tectal and ascending cervical inputs, as well as of oro-facial and neck primary afferent inputs onto an unselected population of interneurones in the NVspo-gamma (Westberg and Olsson 1991).  相似文献   
94.
CSF and serum was obtained from 216 patients with neurological or psychoneurotic symptoms and the concentrations of albumin and IgG were immunologically determined. The IgG/albumin index, calculated as the quotient of the CSF/serum ratios of IgG and albumin was compared with electrophoresis on agar gel. In "normal" cases, the IgG/albumin index was between 0.26-0.66. Pathological electrophoresis, i.e. with two or more IgG bands in the gamma globulin region was found in 85 per cent of the MS patients; in 29 per cent of the patients with a possible demyelinating disease; in 41 per cent of patients with CNS infection; and in 4 per cent of patients with other neurological disorders; whereas an increased IgG/albumin index ( greater than 0.66) was found in 88 per cent of the MS patients; in 43 per cent of the patients with a possible demyelinating disease; in 50 per cent of the patients with CNS infection; in 11 per cent of patients with immunological disorders; and in 18 per cent of patients with other neurological diseases. The increase of the IgG/albumin index was sometimes moderate (0.67-0.90), except in patients with MS, syphilis and other CNS infections, where a pathological electrophoresis combined with an IgG/albumin index above 1.0 was found to be a valuable support for the clinical diagnosis.  相似文献   
95.
BACKGROUND: Transplanted islets lack endothelial cells immediately after implantation and therefore depend on an adequate revascularization for their survival and function. However, the functional properties of the newly formed islet graft microvessels are largely unknown. This study aimed to investigate the blood flow regulation of transplanted pancreatic islets. METHODS: Pancreatic islets were syngeneically transplanted beneath the renal capsule of control and streptozotocin-diabetic rats. Blood flow measurements were performed 4 weeks later using laser-Doppler flowmetry. Adenosine (0.6 mg x kg(-1) x min(-1), angiotensin II (AT II; 0.17 microg x kg(-1) x min(-1)) and the nitric oxide synthase inhibitor NG-nitro-L-arginine (25 mg/ kg) were given to each animal. RESULTS: An increased basal blood flow and basal vascular conductance in the islet grafts, but not in the renal cortex, were seen in diabetic rats compared with control rats. Adenosine increased, and AT II decreased, the vascular conductance of the islet grafts in both nondiabetic and diabetic animals. A more pronounced circulatory response to AT II was observed in kidneys of diabetic animals, whereas there was no difference in the islet graft blood flow response between nondiabetic and diabetic animals. NG-Nitro-L-arginine decreased islet graft blood flow and vascular conductance in both nondiabetic and diabetic recipients, but the effect was more pronounced in the non-diabetic animals. CONCLUSIONS: Islet graft blood flow was influenced by adenosine, AT II, and nitric oxide inhibition in all animals. However, diabetic animals were less dependent on nitric oxide to maintain a basal blood flow in the islet graft.  相似文献   
96.
A cohort of offspring of mothers with breast or ovarian cancer diagnosed in 1958-1993 was established using Swedish population-based registers. The children (n = 158,041) were born between 1941 and 1993, and their cancer incidence was followed between 1961 and 1993. A total of 3,257 tumors in 3,102 children were found. Observed numbers of cases were compared with expected numbers based on national calendar year-, age-, and sex-specific incidences. For daughters of women with breast cancer, the standardized morbidity ratios for being diagnosed with breast cancer and ovarian cancer before age 50 years were 1.99 (95% confidence interval (CI): 1.86, 2.14) and 1.28 (95% CI: 1.05, 1.54), respectively. The corresponding figures for daughters of women with ovarian cancer were 1.79 (95% CI: 1.55, 2.07) and 2.38 (95% CI: 1.77, 3.12). The risks were raised if the mother's cancer was diagnosed at a young age, the mother had multiple breast/ovarian diagnoses, or there was a sister with breast/ovarian cancer. Among all offspring, increased risks were found for thyroid cancer, testicular cancer, and malignant melanoma, while lung cancer risk was decreased if the mother had had breast cancer. The authors developed a variance estimator for the standardized morbidity ratio to cope with overdispersion due to dependency within families.  相似文献   
97.
Transplantation of pancreatic islets may provide a cure for type 1 diabetes. However, this treatment can currently be offered only to very few patients. To improve transplantation success we need to understand better the mechanisms of how the implanted islets survive, grow and/or maintain adequate function. We herein report on our studies to evaluate the factors responsible for the engraftment, i.e. revascularization, reinnervation etc., of transplanted islets and relate these factors to the metabolism and growth of the islets. Graft metabolism can be monitored by microdialysis probes that allow for the measurement of minute amounts of islet metabolites and hormonal products. Growth of the endocrine cells can be stimulated both in vitro before implantation and in vivo post-transplantation. Another problem is rejection of transplanted islets, which may be overcome by the microencapsulation of islets. The knowledge gained by the present studies will enable us to elucidate the optimal treatment of islets to ensure a maximal survival of the transplanted islets, and may be applied also to clinical islet transplantation.  相似文献   
98.
99.
We investigated the impact of highly purified Haemophilus ducreyi cytolethal distending toxin (HdCDT) on the apoptosis and necrosis of various human cells; including myeloid cells, epithelial cells, keratinocytes, and primary fibroblasts. The levels of apoptosis and necrosis induced in these cells were compared to those induced by HdCDT in human T cells and in the Jurkat T cell line. Levels of caspase-3 activity were measured, and membrane changes like phosphatidylserine (PS) translocation was evaluated after double-staining with the fluorescein isothiocyanate (FITC)-labeled annexin V and propidium iodide (PI) using flow cytometry. HdCDT induced various degrees of apoptosis and necrosis in dose- and time-dependent manners in cells of various lineages. Early and late apoptosis (annexin V-stained cells) were induced in more than 90% of T cells and monocytes after treatment with 100 ng/ml HdCDT for 24 and 48 h, respectively. The corresponding numbers for epithelial cells, keratinocytes, and fibroblasts were 26-32% after treatment with 100 ng/ml HdCDT for 48 h. HdCDT appears to eliminate effectively by inducing apoptosis those cells that are involved in immune responses. Epithelial cells, keratinocytes and fibroblasts, which are important for the healing of chancroid ulcers, are eliminated by apoptosis or necrosis after contact with HdCDT, albeit slower and to a lesser extent than T cells.  相似文献   
100.
儿童皮下和网膜脂肪组织瘦素表达水平及其临床意义   总被引:1,自引:1,他引:1  
【目的】 对不同年龄儿童皮下和网膜脂肪组织中瘦素 (leptin)mRNA表达水平进行调查。  【方法】 配对的皮下和网膜脂肪组织从腹部择期手术患儿 ( 3 7例 ,3月~ 12岁 )和成人 ( 9名 )获取。应用real timeRT PCR方法测定不同部位脂肪组织中leptinmRNA表达水平 ,并探讨其与体块指数 (BMI)、腰围、臀围及腰臀围比 (WHR )、年龄、性别及肥胖的相互关系。 【结果】 与成人相一致 ,儿童leptin的表达亦有明显的部位性差异 ,皮下脂肪组织中leptinmRNA水平显著高于网膜 (P <0 .0 0 1)。皮下脂肪组织leptinmRNA表达水平与BMI呈显著正相关 (r =0 .69,P <0 .0 0 1) ,而网膜leptin与BMI呈较弱的正相关 (r =0 .3 2 ,P <0 .0 5 ) ;皮下和网膜leptin与WHR的均无显著相关 ,但网膜leptin与腰围呈较弱的正相关 (r =0 .3 3 ,P <0 .0 5 )。不同年龄组中脂肪组织的leptin表达水平差异有显著性(P <0 .0 1) ,6~ 12岁组皮下和网膜脂肪组织leptinmRNA表达均高于 1~ 5岁组 (P <0 .0 5 ) ,与成人水平相比 ,则差异无显著性 (P >0 .0 5 )。过重和肥胖儿童脂肪组织leptinmRNA表达水平显著高于非肥胖儿童。  【结论】 儿童不同部位脂肪组织leptinmRNA表达水平在一定程度上反映了脂肪组织的生长和分布。肥胖儿童脂肪组织leptin的  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