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   434216篇
  免费   23975篇
  国内免费   524篇
耳鼻咽喉   6467篇
儿科学   15004篇
妇产科学   13553篇
基础医学   65469篇
口腔科学   12070篇
临床医学   35580篇
内科学   80761篇
皮肤病学   10348篇
神经病学   35097篇
特种医学   17526篇
外国民族医学   45篇
外科学   67321篇
综合类   8390篇
现状与发展   1篇
一般理论   202篇
预防医学   27902篇
眼科学   9952篇
药学   30377篇
中国医学   990篇
肿瘤学   21660篇
  2021年   3464篇
  2019年   3669篇
  2018年   6591篇
  2017年   5188篇
  2016年   6350篇
  2015年   6357篇
  2014年   7721篇
  2013年   12639篇
  2012年   16138篇
  2011年   17416篇
  2010年   10626篇
  2009年   8578篇
  2008年   16661篇
  2007年   17887篇
  2006年   17505篇
  2005年   16941篇
  2004年   16168篇
  2003年   15691篇
  2002年   15260篇
  2001年   18334篇
  2000年   19905篇
  1999年   15019篇
  1998年   4473篇
  1997年   3989篇
  1996年   3562篇
  1995年   3287篇
  1994年   3104篇
  1993年   2921篇
  1992年   9117篇
  1991年   9151篇
  1990年   8949篇
  1989年   8792篇
  1988年   7886篇
  1987年   7736篇
  1986年   7269篇
  1985年   7277篇
  1984年   5449篇
  1983年   4726篇
  1982年   3088篇
  1979年   4983篇
  1978年   3735篇
  1977年   3256篇
  1976年   2943篇
  1975年   3291篇
  1974年   3819篇
  1973年   3765篇
  1972年   3464篇
  1971年   3299篇
  1970年   3160篇
  1969年   2883篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The aqueous, organic, and volatile oil extracts of leaves of Eugenia uniflora Linn. Family Myrtaceae were investigated for antibacterial properties using agar dilution techniques. The aqueous extract was the most active against the organisms compared to the organic and volatile oil extracts. The extracts were found to inhibit Gram positive Staphylococcus aureus and Bacillus subtilis and Gram negative Escherichia coli and Shigella dysentcriae. Pseudomonas aeruginosa, Klebsiella pneumoniac, and Salmonella typhi were not inhibited.  相似文献   
82.
The effects of hemorrhagic shock (HE) on duodenal pH, acid-neutralizing capacity and mucosal tolerance to acid were investigated in anesthetized rats, and they were compared with those of indomethacin. HE was performed by bleeding from the carotid artery to reduce arterial blood pressure to about 55 mmHg (3 ml of bleeding per 200 g of body weight), and indomethacin was given s.c. in a dose of 5 mg/kg. Duodenal pH was determined in the outflow from the proximal duodenum (1.7 cm) which was perfused with 10(-4) M HCl, and acid-neutralizing capacity was measured by back-titration of the perfusate to pH 4.0 with 10 mM HCl. Under these conditions, duodenal pH was kept at around 6.0 as the result of neutralization in the loop (approximately 8 microEq/hr). Both HE and indomethacin significantly decreased the pH and acid-neutralizing capacity. Administration of 16,16-dimethyl prostaglandin E2 (16-dmPGE2: 30 micrograms/kg, s.c.) significantly increased both pH and acid-neutralizing capacity in normal and indomethacin-treated rats, but failed to affect these parameters in rats under HE conditions. When the duodenal loop was perfused with 50 mM HCl for 1.5 hr, both HE and indomethacin induced extensive damage in the mucosa. Pretreatment with 16-dmPGE2 significantly reduced the formation of duodenal lesions induced by indomethacin but not by HE. These results suggest that HE as well as indomethacin impaired duodenal acid-neutralizing capacity to reduce the tolerance to acid of the mucosa. The deleterious effects of HE on the mucosa may be mainly due to a decreased mucosal blood flow, but not due to a deficiency of endogenous prostaglandins.  相似文献   
83.
Techniques of ankle arthroscopy   总被引:1,自引:0,他引:1  
Although arthroscopic instrumentation varies widely, the technique for use is quite similar. Surgeon preferences vary but most arthroscopists agree that it is technique that makes the procedure. Discussed in this presentation is the author's method for preparing the patient for arthroscopic surgery, as well as techniques for using the arthroscope, hand instruments, and power instrumentation.  相似文献   
84.
This study presents the result of 12–21 years' follow-up in a group of children with neonatal urinary tract infection (onset within 1 month after birth) in whom early renal growth retardation was noted without concomitant classical renal scarring. In all cases the neonatal infection was diagnosed and treated within a few days of onset and the patients were closely supervised thereafter. Renal length, parenchymal thickness and area were measured at urography. At first follow-up (22 children, mean age 4.1 years) a significant reduction of renal parenchymal thickness was noted. Long-term follow-up (18 patients, mean age 17 years) demonstrated a normalization of renal size in the entire group, although less complete in the subgroup with reflux. There were two major findings in the present study. Firstly, renal growth retardation was seen after neonatal infection, both with and without reflux. Secondly, normalization of renal size in previously small kidneys was demonstrated, suggesting that growth retardation can be a reversible phenomenon. The tendency for such normalization was slightly more marked in children without reflux. Reduction of parenchymal thickness without calyceal deformity, therefore, does not necessarily mean irreversible damage, and differentiation between permanent scarring and temporary growth retardation can thus only be made at later follow-up, possibly not until after puberty. The demonstration of renal growth retardation in spite of early diagnosis and treatment emphasizes the great vulnerability of the kidney in the newborn.  相似文献   
85.
86.
Obese, overweight, desirable, ideal: where to draw the line in 1986?   总被引:1,自引:0,他引:1  
In February 1985, the National Institutes of Health sponsored the Consensus Development Conference on the Health Implications of Obesity. The panel of experts concluded that height and weight tables based on mortality data and the body mass index (BMI) are helpful measures to determine the presence of obesity and the need for treatment. For the dietitian, however, practical concerns arise regarding which index to select. The usefulness of the BMI in patient education and contradictions between the 1959 and 1983 Metropolitan Life Insurance height-weight tables are discussed. A temporary solution is offered in light of the need for further investigation into morbidity experience at weights recommended in the 1983 table.  相似文献   
87.
A novel approach for modelling the biological activity of organic molecules, which requires simultaneous consideration of the influence of all factors (topological, steric, hydrophobic, and electronic) that determine the bioactivity, is used to study the interaction of a series of benzoates with anti-p-(p'-azophenylazo)benzoate antibody. The results obtained suggest that this biological interaction proceeds by a two-step stereospecific mechanism. The first step requires a geometrical correspondence between the benzoates and the cavity in the biomacromolecule, which enables the pharmacophore to come into close contact with the receptor. The second step is the orbitally controlled electronic interaction between the active parts of the benzoates and the antibody. The electronic interaction results from pi-charge transfer from the pharmacophore to the biomacromolecule and from the formation of pi-complexes. A proposed mathematical model for this biological interaction exhibits some statistical advantages over existing models.  相似文献   
88.
Haemophilus influenzae vaccine containing polyribosyl ribitol phosphate (PRP) or PRP covalently linked to diphtheria toxoid (PRP-D) was given to 94 healthy infants 17 to 22 months of age at the same time, but not at the same site, as a diphtheria-tetanus-pertussis booster. Systemic reactions were similar in the two vaccine groups and resembled those expected with the diphtheria-tetanus-pertussis injection alone. Six (13%) and seven (14%) of the PRP and PRP-D recipients, respectively, had minor local reactions to the Haemophilus vaccine. Among the 77 children who were not already naturally immune (ie, anti-PRP antibody concentration of less than or equal to 0.15 micrograms of protein per milliliter) before vaccination, PRP-D was significantly more effective than PRP in inducing protective levels of antibody. Only 15 (43%) of the 35 nonimmune PRP recipients achieved a concentration of greater than or equal to 0.15 microgram/mL and only seven (20%) reached a concentration greater than or equal to 1.0 micrograms/mL following vaccination. In contrast, 34 (81%) of the 42 nonimmune recipients of PRP-D had a concentration of greater than or equal to 0.15 microgram/mL following vaccine and 32 (62%) had a concentration of greater than or equal to 1.0 micrograms/mL (P less than or equal to .001). These results suggest that more than one-half of nonimmune 18-month-old infants will not respond to PRP with protective levels of antibody. In light of the current data, recommendation for revaccination at 24 months of age for those immunized at any younger age is appropriate.  相似文献   
89.
90.
The expression of two heat shock proteins, HSP72 and p57, in addition to ubiquitin, has been studied immunocytochemically in nine amyotrophic lateral sclerosis (ALS) cases and 10 age-matched controls. HSP72 and p57 antibodies did not identify the characteristic ubiquitin-immunoreactive inclusions present in anterior horn cells in ALS spinal cord. Antibodies to HSP72, but not to p57 or ubiquitin, strongly labelled structures corresponding to polyglucosan bodies in spinal grey matter. Such immunoreactive profiles were more abundant in ALS cases, although they were also present in control material. They were sometimes identified by haematoxylin and eosin and periodic acid Schiff reaction, but were not labeled by phosphotungstic acid haematoxylin or by antibodies to glial fibrillary acidic protein. Although ubiquitin, HSP72 and p57 are stress-induced proteins, they are expressed differently and might therefore have different significance in neuronal degeneration.  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