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   15788篇
  免费   643篇
  国内免费   53篇
耳鼻咽喉   303篇
儿科学   1035篇
妇产科学   705篇
基础医学   1757篇
口腔科学   351篇
临床医学   1219篇
内科学   3458篇
皮肤病学   528篇
神经病学   970篇
特种医学   358篇
外科学   2408篇
综合类   329篇
一般理论   2篇
预防医学   1246篇
眼科学   324篇
药学   908篇
  1篇
中国医学   47篇
肿瘤学   535篇
  2021年   114篇
  2020年   76篇
  2019年   123篇
  2018年   140篇
  2017年   133篇
  2016年   121篇
  2015年   200篇
  2014年   250篇
  2013年   326篇
  2012年   444篇
  2011年   485篇
  2010年   306篇
  2009年   316篇
  2008年   487篇
  2007年   544篇
  2006年   566篇
  2005年   504篇
  2004年   444篇
  2003年   404篇
  2002年   439篇
  2001年   376篇
  2000年   388篇
  1999年   344篇
  1998年   236篇
  1997年   251篇
  1996年   276篇
  1995年   224篇
  1994年   214篇
  1993年   216篇
  1992年   259篇
  1991年   249篇
  1990年   218篇
  1989年   203篇
  1988年   189篇
  1987年   203篇
  1986年   149篇
  1985年   125篇
  1984年   108篇
  1983年   88篇
  1982年   75篇
  1981年   86篇
  1979年   61篇
  1959年   345篇
  1958年   759篇
  1957年   868篇
  1956年   771篇
  1955年   803篇
  1954年   780篇
  1949年   182篇
  1948年   125篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
81.
We report on the mechanisms, the environmental changes and patient compliance with regard to conventional and new dust and mite avoidance measures to prevent allergic symptoms caused by mite allergens, taking into account both allergen contamination and the developmental success of pyroglyphid Acari. Twenty patients with persisting rhinitic complaints were selected and matched. Although the patients had performed some conventional dust and mite avoidance measures (patient compliance was 90%), the dwellings proved to be a stimulus for mite development. Moisture problems due to faulty construction and excessive moisture production were common. Since humidity conditions could not be changed at short notice, the 20 homes were subjected to the new variants of mite allergen avoidance based on intensive cleaning without (control) and with an acaricide incorporated (acaricidal cleaner [Acarosan]). After the carrying out of conventional avoidance measures, these patients still had allergic symptoms, and dust from only 23 to 52% of their textile objects was under the proposed guanine (mite faeces indicator) risk level. Only the acaricidal cleaner was able to decrease the allergenic mite load (and the burden of the patients) significantly in this 12 month period. With respect to mite-extermination, acaricidal cleaning was 88% better than intensive cleaning. Reduction of guanine was 38% better in the Acarosan treatment group. Clinical results have been reported elsewhere. A significant difference in favour of the acaricidal cleaning was seen in both subjective (as regards symptoms) and in objective data (total IgE). Another 50 patients were questioned. About 90% were willing to spend two weekends (70%), or at the most one weekend (20%) per year sanitizing the dwelling by cleaning it with the whole family. The authors of this report consider acaricidal cleaning to be a significant improvement in the management of mite-allergic diseases, such as rhinitis. Compared with the replacement of home textiles, this treatment is less expensive and more effective. Patient compliance is acceptable, but depends on acceptance by physicians and the initial motivation and consequent burden on the patient.  相似文献   
82.
The epidemiological survey of APH (3') I and APH (3') II genes, at a time when the specific antibiotic pressure was very low, was carried out by DNA-DNA hybridization. The sample included 334 aminoglycoside resistant Gram-negative bacteria collected from patients of a General Hospital. Of these, 251 hybridized with the APH (3') I-probe and 19 with the APH (3') II-probe but only 190 strains showed high resistance levels (CIM greater than 64 micrograms/ml) for kanamycin, neomycin and paromomycin. These strains were isolated both from inpatients and outpatients with different infectious diseases. The APH (3') I-gene was dispersed among all the bacterial species and clinical specimens tested but the APH (3') II-gene was not found in Pseudomonas spp, Escherichia coli, Citrobacter freundii and Enterobacter cloacae, nor in infected catheters. Several plasmids of different sizes carrying APH (3') genes were detected among different bacteria. Plasmids along with transposable elements (the probes used in this work were developed from Tn906 and Tn5) and the high consumption of other antibiotics whose resistance is carried by these bacteria might be playing an important role in the maintenance and dispersion of APH (3') genes.  相似文献   
83.
Morganella morganii, a gram-negative bacterium, usually infects older patients with urinary catheters, but does not commonly affect pregnant women. In this report we present a case of chorioamnionitis caused by Morganella morganii. The case was complicated by a life-threatening Adult Respiratory Distress Syndrome.  相似文献   
84.
Differentiating seizures from pseudoseizures frequently is challenging in very young children manifesting repetitive, stereotypic behavior. Using video electroencephalographic recording, we evaluated 60 patients, younger than 10 years of age, with episodic signs and symptoms believed to be seizures despite repeatedly normal routine electroencephalograms. Nine patients (15%) had simple partial and atypical absence seizures. Twenty-four patients (40%) had pseudoseizures presenting as rhythmic movements or staring. Pseudoseizure frequency was greater than the frequency of true seizures; brief staring episodes were common. Motor pseudoseizures usually were of longer duration than true seizures and could be brought on with verbal encouragement. Furthermore, the stereotypic motor presentations were quite different from those of true motor seizures but were difficult to recognize from historic, clinical, and routine electroencephalographic data. Symptomatic patients can be clinically diagnosed by analyzing confirmed episodes with video electroencephalography.  相似文献   
85.
86.
The objectives of this study were: 1) to identify and characterize ewe oviductal secretory proteins (OSP) de novo synthesized during the estrous cycle; 2) to examine the effect of estrogen (E) and progesterone (P) on synthesis of OSP; and 3) to determine synthesis of OSP by ampulla (A) and isthmus (I). Oviducts were collected from cyclic ewes on days 1, 8, and 16 and ovariectomized (OVX) ewes after treatment with corn oil (CO), E, P, and E + P. Tissue was incubated in the presence of 3H-leucine or 3H-glucosamine. Rates of 3H-leucine incorporation into nondialyzable macromolecules by explants was greater (P less than 0.05) on day 1 than days 8 and 16, greater (P = 0.01) in OVX E-treated ewes, greater in A than I regardless of treatment and greater (P less than 0.05) in A than I with E. Culture medium was analyzed by one- and two-dimensional polyacrylamide gel electrophoresis and fluorography. Two major basic proteins (Mr 90-92,000) and three minor proteins were only present on day 1 of estrus. E treatment demonstrated these same proteins which were not found with CO or P treatment. Two-dimensional analysis of medium from A and I cultured separately indicated that A synthesized the two major basic and three minor E-dependent proteins. Of three protein complexes present regardless of treatment or cycle day, two were dominant in the A and one was dominant in the I suggesting a synthetic gradient. Tunicamycin did not inhibit incorporation of 3H-glucosamine into E-dependent proteins. Gel filtration revealed a high Mr fraction (2 x 10(6] 2.5-fold greater on day 1 than day 8 and 2.2-fold greater with E than CO treatment. This study clearly demonstrates: 1) that the oviduct from estrus and E-treated ewes synthesizes two major basic and three minor glycoproteins not detectable on other cycle days or with OVX or P treatment; 2) the E-dependent glycoproteins are synthesized by the A; and 3) a high Mr fraction is induced or amplified by E.  相似文献   
87.
Hepatocytes isolated from the liver of rats after a necrotizing dose of thioacetamide (6.6 mmol/kg) were used to study the postnecrotic process of liver regeneration. Flow cytometry analysis revealed populations of dedifferentiated hepatocytes exhibiting physical properties (size and fluorescence emission at 530 nm) similar to those found in fetal (22 days old) liver cells. The percentage of these cells increased progressively from 24 to 48 and 72 hr after thioacetamide administration. In primary cultures of hepatocytes the effects of phorbol 12-myristate 13-acetate, bombesin and insulin were investigated on the 6-phosphofructo 2-kinase/fructose 2,6 bisphosphate system. Bombesin and insulin stimulated 6-phosphofructo 2-kinase activity and fructose 2,6-bisphosphate content both in control and in thioacetamide-treated hepatocytes. However, phorbol 12-myristate 13-acetate stimulated 6-phosphofructo 2-kinase activity and increased fructose 2,6-bisphosphate concentration in thioacetamide-treated liver cells, whereas no similar response was found in hepatocytes from control rats. The response of postnecrotic thioacetamide-treated hepatocytes to phorbol 12-myristate 13-acetate was similar to that obtained from 22-day-old fetal liver cells, which reveals that different methods might control fructose 2,6-bisphosphate content and therefore the mechanisms of glycolysis and gluconeogenesis at this regulatory step. The lack of response to glucagon of glycogen phosphorylase a and 6-phosphofructo 2-kinase from thioacetamide-treated hepatocytes may indicate that the expression of specific enzymes of carbohydrate metabolism undergoes transitions to less-differentiated isoenzymatic forms. Moreover, the isoenzyme pattern of hexokinases elicits a complete disturbance in glucokinase and hexokinases activities.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
88.
89.
90.
Cardiac tamponade after intrapericardial diaphragmatic hernia   总被引:2,自引:0,他引:2  
An unusual case of intrapericardial diaphragmatic hernia ispresented. Cardiac tamponade occurred in the operating roomsoon after induction of anaesthesia. Surgical removal of theherniated omentum and stomach allowed haemodynamic improvement.The pathophysiology is discussed and patients with cardiac tamponadereviewed.  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