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   8490篇
  免费   528篇
  国内免费   46篇
耳鼻咽喉   127篇
儿科学   272篇
妇产科学   119篇
基础医学   1319篇
口腔科学   211篇
临床医学   714篇
内科学   1969篇
皮肤病学   318篇
神经病学   607篇
特种医学   603篇
外国民族医学   2篇
外科学   1301篇
综合类   88篇
一般理论   1篇
预防医学   554篇
眼科学   99篇
药学   385篇
中国医学   6篇
肿瘤学   369篇
  2021年   116篇
  2020年   67篇
  2019年   92篇
  2018年   118篇
  2017年   92篇
  2016年   151篇
  2015年   158篇
  2014年   187篇
  2013年   295篇
  2012年   330篇
  2011年   382篇
  2010年   212篇
  2009年   237篇
  2008年   332篇
  2007年   379篇
  2006年   358篇
  2005年   306篇
  2004年   293篇
  2003年   323篇
  2002年   289篇
  2001年   255篇
  2000年   279篇
  1999年   232篇
  1998年   158篇
  1997年   139篇
  1996年   128篇
  1995年   100篇
  1994年   111篇
  1993年   94篇
  1992年   131篇
  1991年   132篇
  1990年   127篇
  1989年   149篇
  1988年   162篇
  1987年   169篇
  1986年   144篇
  1985年   139篇
  1984年   109篇
  1983年   80篇
  1982年   63篇
  1981年   64篇
  1979年   92篇
  1978年   78篇
  1977年   58篇
  1976年   62篇
  1974年   67篇
  1973年   88篇
  1972年   62篇
  1971年   59篇
  1968年   55篇
排序方式: 共有9064条查询结果,搜索用时 15 毫秒
81.
82.
Insemination with donor spermatozoa is an integral part of infertility treatment. For the last 3 years in our unit, intrauterine insemination with donor spermatozoa (IUID) has been used in preference to vaginal insemination. In this retrospective study, patients were offered an initial course of five single intrauterine inseminations with cryopreserved donor spermatozoa and treatment was then reviewed. A total of 389 patients received 1465 inseminations. In all, 1119 cycles were monitored using luteinizing hormone serum analyses and 346 cycles using the urine home test kits. The clinical pregnancy rate per insemination for the cycles monitored by the serum assay was 18.0% (202/1119) compared with the urine cycles (13.7%, 46/346) (P <05). The pregnancy loss rate was not significantly different (14.4%, 29/202 and 21.7%, 10/46) (serum and urine cycles respectively). The viable clinical pregnancy rate was significantly higher (P <03) for the serum cycles than for the cycles using the urinary monitoring (15.5%, 173/1119 and 10.4%, 36/346 respectively). The cycles monitored by serum assay had a significantly higher cumulative viable clinical pregnancy rate (P <0001) of 70.2% after nine inseminations compared with the urine monitored cycles of 54.8%. The majority of patients opted for the serum cycles, with a minority self-selecting the urine cycles mainly for travelling convenience. The explanation for the significant differences between the viable clinical pregnancy rates per insemination and the cumulative viable clinical pregnancy rates may be due to the sensitivity of the urine home test kit or the patients' interpretation of the result.   相似文献   
83.
Summary The angular points are the ligamentous and tendinous structures that reinforce the posteromedial and posterolateral capsule of the knee and share in fixation of the posterior horns of the menisci. They are often damaged in acute injuries and this is usually associated with ruptures of the cruciate and collateral ligaments and may add to the degree of laxity. We describe the normal appearance of these structures in terms of the sectional anatomy, correlated with the lesional appearances of complete and incomplete ruptures and associated meniscal detachments as shown by clinical testing and arthrotomy findings.
IRM des points d'angle du genou : bases anatomiques et applications aux genoux traumatiques
Résumé Les points d'angle sont des structures ligamentaires et tendineuses qui renforcent la capsule postéro-médiale et postéro-latérale et participent à la fixation des cornes postérieures des ménisques. Leurs lésions, fréquentes au cours des traumatismes aigus, sont généralement associées à des ruptures des ligaments croisés et des ligaments collatéraux et peuvent être source d'une aggravation de la laxité. Nous rapportons, en corrélation avec l'anatomie en coupe, l'aspect normal de ces structures, et en corrélation avec les données de l'arthrotomie et du testing les aspects lésionnels observés au cours des traumatismes : ruptures complètes, incomplètes et désinsertions méniscales associées.
  相似文献   
84.
Summary: The flame retardant mechanisms of red phosphorus, magnesium hydroxide and red phosphorus combined with magnesium hydroxide were studied in high impact polystyrene by means of comprehensive decomposition studies and combustion tests. The study is intended to illuminate prerequisites and the potential of red phosphorus as a fire retardant for hydrocarbon polymers in the condensed phase and in the gas phase. Thermal and thermo‐oxidative decomposition, decomposition kinetics and the product gases evolved were characterized using thermogravimetry coupled with Fourier transform infrared spectroscopy and mass spectroscopy, respectively. Fire behaviour was investigated with a cone calorimeter using different external heat fluxes, whereas the flammability was determined by limited oxygen indices. The combustion residues were analysed using XPS. Red phosphorus reduced the heat release in HIPS due to radical trapping in the gas phase. Magnesium hydroxide influenced fire behaviour by heat sink mechanisms, release of water and the formation of a magnesia layer acting as a barrier. The combination of both flame retardants in HIPS nearly resulted in a superposition. A slight synergy in barrier characteristics was due to the formation of magnesium phosphate, whereas a slight anti‐synergism occurred in flammability and in the gas phase action. The latter effect is controlled by a decreased fuel rate due to the barrier layer rather than by an initiation of red phosphorus oxidation in the condensed phase.

Heat release rate and total heat release at various external heat fluxes for HIPS (dotted = 70 kW · m?2, dashed = 50 kW · m?2, solid = 30 kW · m?2).  相似文献   

85.
The repeated injection of bacterial superantigens (SAg), such as staphylococcus enterotoxin (SE) A or B, has been shown in mice to induce a state of unresponsiveness characterized by the lack of secretion of Th1 lymphokines, such as IL-2 and IFN-gamma, following subsequent SAg challenge. We made the observation, in vivo as well as in vitro, that unresponsiveness to SAg could be transferred from SEA- to SEB-reactive T cells (and reversibly from SEB- to SEA-specific T cells) in C57BL/6 mice but not in BALB/c mice. Since C57BL/6 mice, unlike BALB/c mice, possess TCR V(beta)3+ and V(beta)11+ T cells able to react with both SEA and SEB, we hypothesized that SAg-unresponsive V(beta)3(+) and V(beta)11+ T cells could mediate linked suppression of other SAg-reactive T cells. To analyze further this possibility, spleen cells from BALB/c mice made unresponsive to SEB were tested for their capacity to suppress the response of normal BALB/c cells to SEB. The production of both IFN-gamma and IL-2 following SEB stimulation was greatly impaired in co-cultures containing CD4(+) T cells, but not CD8(+) T cells, isolated from unresponsive animals. In vivo, the production of both IFN-gamma and IL-2 responses to SEB was dramatically reduced in animals adoptively transferred with unresponsive spleen cells. This suppression was abrogated in recipients injected with neutralizing anti-IL-10 antibodies. Moreover, in animals made unresponsive to SEB, SAg-reactive CD4(+) T cells were found to express high levels of CTLA-4, a molecule recently described to play an essential role in the suppressive function of regulatory T cells. Taken together these results demonstrate that the repetitive injection of SAg induces the differentiation of regulatory CD4(+) T cells capable of suppressing SAg-reactive naive T cells.  相似文献   
86.
87.
H1-blockers are often added to the standard treatment of acute sinusitis, but this is not supported by a controlled study. A multicentric, randomized, double-blind, placebo-controlled, parallel-group study was done in 139 allergic patients (15–65 years) to assess the adjunct efficacy of loratadine in acute exacerbation of rhinosinusitis. Sinusitis was diagnosed by symptoms and confirmed by rhinoscopy and sinus radiograph. Allergy was characterized by skin tests, RAST, and history. Patients were treated with antibiotics (14 days), oral corticosteroids (10 days), and loratadine (10 mg OD) or placebo (28 days). Treatment efficacy was assessed over 28 days by symptom scores quoted daily by patients. Physicians also rated total symptom scores at entry and at day 28. At entry, both groups had similar symptoms. Placebo-treated patients improved significantly, but patients who received loratadine had a significantly greater improvement in sneezing ( P =0.003) after 14 days, and in nasal obstruction ( P =0.002) after 28 days. Physicians found that patients receiving loratadine were significantly improved compared to placebo patients ( P =0. 0125). Loratadine in addition to standard therapy was found to improve the control of some symptoms of sinusitis.  相似文献   
88.
Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.   相似文献   
89.
A double-blind modification of the intraesophageal acid perfusion challenge (Bernstein procedure) was performed in asthmatic subjects with and without gastroesophageal reflux, nonasthmatic subjects with reflux, and normal subjects. Conventional spirometric functions and total respiratory resistance (Rrs) were measured prior to and after the infusion. There were no changes in pulmonary functions except in the asthmatic subjects who had had a positive add challenge. The greatest changes occurred in Rrs, which increased significantly with reflux symptoms (p < 0.01) and decreased toward baseline (p < 0.05) when these symptoms were relieved with antacids. The response was even greater in asthmatic subjects who associated reflux symptoms with attacks of asthma. These results support previous findings that acid reflux symptoms could cause a bronchoconstrictive response in certain asthmatic patients.  相似文献   
90.
Prolonged chair restraint and social isolation in the rhesus monkey led to a reduction in the urinary excretion of HVA (4-hydroxy-3-methoxyphenylacetic acid), DOPAC (3,4-dihydroxyphenylacetic acid), VMA methoxy-4-hydroxymandelic acid), and MHPG (3-methoxy-4-hydroxyphenylethylglycol) over a 3 week period. This adaptation to a chronically "stressful" situation corresponds to earlier studies on the rhesus monkey indicating a gradual reduction in the urinary excretion of norepinephrine and epinephrine after initiation of restraint. The following basic information on the urinary excretion of catecholamine metabolites was obtained: (1) the rate of excretion of the dopamine metabolites (HVA and DOPAC) is about four times higher than the rate of excretion of adrenergic metabolites (VMA and MHPG): (2) MHPG is the major adrenergic metabolite in the rhesus monkey; and (3) the excretion rates of the urinary metabolites varied considerably between animals.  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