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   1220篇
  免费   65篇
  国内免费   50篇
耳鼻咽喉   11篇
儿科学   44篇
妇产科学   15篇
基础医学   157篇
口腔科学   29篇
临床医学   139篇
内科学   337篇
皮肤病学   34篇
神经病学   83篇
特种医学   155篇
外科学   77篇
综合类   30篇
预防医学   55篇
眼科学   17篇
药学   92篇
中国医学   4篇
肿瘤学   56篇
  2021年   6篇
  2020年   7篇
  2019年   7篇
  2018年   8篇
  2017年   12篇
  2016年   7篇
  2015年   27篇
  2014年   25篇
  2013年   34篇
  2012年   34篇
  2011年   36篇
  2010年   42篇
  2009年   46篇
  2008年   38篇
  2007年   67篇
  2006年   31篇
  2005年   32篇
  2004年   22篇
  2003年   23篇
  2002年   32篇
  2001年   29篇
  2000年   25篇
  1999年   20篇
  1998年   50篇
  1997年   54篇
  1996年   59篇
  1995年   33篇
  1994年   35篇
  1993年   27篇
  1992年   17篇
  1991年   18篇
  1990年   17篇
  1989年   48篇
  1988年   44篇
  1987年   35篇
  1986年   32篇
  1985年   38篇
  1984年   22篇
  1983年   15篇
  1982年   19篇
  1981年   15篇
  1980年   23篇
  1979年   9篇
  1978年   13篇
  1977年   15篇
  1976年   8篇
  1975年   11篇
  1972年   8篇
  1969年   7篇
  1967年   8篇
排序方式: 共有1335条查询结果,搜索用时 15 毫秒
1.
A 41-year-old woman had acute hepatitis A infection complicated with severe anemia due to selective erythroblastopenia and hemolysis. A mechanism involving a cellular immune reaction is suggested. The hematological complications resolved during steroid treatment. She later developed a transient seropositive arthritis.  相似文献   
2.
Quantitative ultrastructural data were obtained from kidney biopsy material of 12 long-term insulin-dependent diabetics. All patients had overt diabetic nephropathy with increased urinary albumin excretion and reduced glomerular filtration rate. Renal clearance of 51Cr-EDTA was in the range of 16-50 ml X min-1 X 1.73 m-2. All patients received antihypertensive treatment. A combined light- and electron-microscope study was performed. A significant proportion of the glomeruli was totally occluded (mean 36%, range 24-67%). Structural data presented relate only to the open, still-functioning glomeruli. Comparison with data previously obtained showed that the thickness of the peripheral basement membrane [647 nm, coefficient of variation (C.V.) 0.22] was more than twice the normal value (310 nm, C.V. 0.08); the width of epithelial foot processes (352 nm, C.V. 0.07) was significantly greater than in normal biopsies (224 nm, C.V. 0.06); and the mean volume of the open glomeruli was markedly increased compared with normal and clearly exceeded that in the early diabetic hypertrophy. Total mesangial volume and total basement membrane material per open glomerulus were increased by 277 and 614%, respectively. However, capillary length and surface per open glomerulus were similar to those observed in early diabetic hypertrophy. These findings suggest that a late glomerular hypertrophy with preservation of capillary surface occurs as a compensatory phenomenon, prolonging renal survival for diabetic nephropathy patients.  相似文献   
3.
The aim of this study was to assess alcoholic inpatients' smoking and coffee intake variation following withdrawal. Only moderate smokers (less than 30 cigarettes/day) showed a significant increase of cigarette consumption after alcohol withdrawal. However, their urinary cotinine level did not vary, suggesting a behavioral, and not biological, compensation through smoking following alcohol withdrawal. Heavy smokers (30 cigarettes/day or more) showed no significant clinical or biological variation of smoking behavior. Coffee consumption increased after alcohol withdrawal in all patients, irrespective of smoking habits.  相似文献   
4.
BACKGROUND: A simple, rapid, inexpensive method for measuring the flow in a patient's vascular access would permit routine monitoring during haemodialysis, and hence provide information of access graft deterioration sufficiently early to increase the success of minimally invasive remedial procedures. This paper reports the validation of such a method in animals. METHODS: A PTFE graft was implanted in sheep between the carotid artery and the jugular vein. While the sheep was under general anaesthesia and on an haemodialysis circuit, ultrasound velocity in its blood was perturbed by the injection of a 5-10 ml bolus of isotonic NaCl. The pump tubing flow was measured by a transit-time blood flow meter. This flow was combined with the areas of perturbation generated by the injection before and after mixing in the access flow to estimate graft flow. The calculated graft flow was compared to flow measured directly by a transit-time probe on the same carotid artery. RESULTS: Over a 10-fold range, 120-1260 ml/min, graft flow measured by ultrasound velocity dilution agreed well with graft flow measured directly with a scatter of 76 ml/min about the regression line. CONCLUSION: Ultrasound velocity dilution provides a method for measuring flow in the graft accurate enough for clinical evaluation of patients on dialysis.   相似文献   
5.
The brains of rats with streptozocin-induced diabetes treated with a low-dose insulin regimen (1 IU/day) were studied with morphometric techniques. After 1 yr of diabetes, brain weight decreased slightly (1350 +/- 71 vs. 1521 +/- 55 mg, 2P less than .01) as did the volume of the neocortex (498 +/- 36 vs. 567 +/- 40 mm3, 2P less than .05). A significant loss of neocortical neurons occurred (38 +/- 2 X 10(6) vs. 46 +/- 3 X 10(6), 2P less than .01), and the length of the capillary network in the neocortical tissue shortened disproportionately (405 +/- 102 vs. 631 +/- 47 m, 2P less than .01), leading to increased diffusion distance. The mechanisms underlying cerebral loss in this model are unknown, but abnormalities of the vascular supply with prolongation of the route of diffusion might play a role.  相似文献   
6.
The contact between dorsal root growth cones and substrates of type IV collagen, fibronectin, poly-L-lysine, and laminin were studied using interference reflection microscopy (IRM) coupled with detaching growth cones from these substrates and observing substrate-associated membrane (SAM). IRM images of growth cones on collagen and fibronectin indicate substantial dark areas of close association between the substrate and basal region of the growth cone. The thin membranous veils and lamellapodia appear bright, indicating a greatly decreased association with the substrate. Filopodia can appear either entirely dark or light but usually are dark interspersed with brighter areas indicating varying degrees of contact. IRM images of growth cones on polylysine and laminin suggest a decreased association between the basal region of the growth cone and the substrate. The appearance of veils and lamellapodia was similar to that observed on collagen and fibronectin. Observations of SAM indicate an increased degree of contact between growth cones and substrates of collagen and fibronectin compared to laminin and polylysine. Collectively these data indicate that simple increases in adhesion are not adequate to explain substrate preference and enhancement of neurite elongation. Overall decreases in adhesion may accomplish the same phenomena, suggesting that it is perhaps more important to consider the regional distribution of adhesive contacts in relation to growth cone movement.  相似文献   
7.
In this prospective, randomized study the clinical response and toxicity of megestrol acetate (MA) and aminoglutethimide (AG) as second-line treatment in patients with metastatic breast cancer was compared. 176 patients were included, and 150 received treatment greater than 8 weeks and are evaluable for treatment response. The two groups did not differ with regard to prognostic factors. Response rate for the AG and MA groups were 34% and 31% respectively, with duration of response of 13.1 and 13.0 months. Stable disease was obtained in 33% and 35% respectively. No difference was observed in survival. Side effects occurred more frequently in the AG group (42%) than in the MA group (18%).  相似文献   
8.
The incidence (%) of hyperbilirubinemia (serum bilirubin ≥257 μmol/l) was similar in neonates with a combination of ABO incompatibility and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency (45%), with ABO incompatibility (54%) or G-6-PD deficiency (37%), alone (ns). Carboxyhemoglobin values, corrected for inspired CO, were similarly elevated in all three groups (0.87 ± 0.32%, 0.82 ± 0.29%, 0.76 ± 0.18%, respectively, ns), but correlated with bilirubin only in those with ABO incompatibility alone. ABO-incompatible/G-6-PD-deficient neonates, compared with those with either condition alone, are not at increased risk for hemolysis or hyperbilirubinemia.  相似文献   
9.
10.
In a human in-vitro fertilization (IVF) programme, the effect of co- culture of embryos with human fibroblasts was evaluated with respect to pregnancy rate and embryo development. Patients were included in the study after giving informed written consent. The IVF treatments were randomly assigned by stratification of both age (<36 versus > or =36 years) and previous IVF attempts (yes versus no). After fertilization was established, the zygotes were transferred to a 4-well dish with or without fibroblasts and cultured for 2 days. On the third day after ovum pick-up (OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were scored and a maximum of three embryos was transferred. Supernumerary embryos of good quality were cryopreserved. The design of this study was a group sequential trial with the objective of detecting differences between pregnancy rates following IVF with conventional incubation or incubation in co-culture with fibroblasts. This design included one evaluation at half-way data collection. In the study, 148 patients had an OPU, of whom 77 were allocated to the co-culture group. There was no statistically significant difference in pregnancy rate, cell number and embryo quality between the two groups. The ongoing pregnancy rate per embryo transfer was 27% in co-culture and 30% in the conventional culture group. The implantation rates per transferred embryo were 17 and 18% respectively. Using a multivariate logistic regression model for the probability of ongoing pregnancies, the odds ratio of co-culture, adjusted for age and previous IVF attempts, was not statistically significant. In conclusion, co-culture with human fibroblasts does not contribute to an improvement of embryo quality nor to a higher pregnancy rate after IVF in an unselected group of patients.   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