全文获取类型
收费全文 | 7246篇 |
免费 | 286篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 155篇 |
儿科学 | 270篇 |
妇产科学 | 286篇 |
基础医学 | 934篇 |
口腔科学 | 81篇 |
临床医学 | 471篇 |
内科学 | 1862篇 |
皮肤病学 | 82篇 |
神经病学 | 676篇 |
特种医学 | 101篇 |
外科学 | 571篇 |
综合类 | 61篇 |
一般理论 | 1篇 |
预防医学 | 608篇 |
眼科学 | 210篇 |
药学 | 740篇 |
中国医学 | 11篇 |
肿瘤学 | 439篇 |
出版年
2023年 | 47篇 |
2022年 | 155篇 |
2021年 | 252篇 |
2020年 | 98篇 |
2019年 | 122篇 |
2018年 | 151篇 |
2017年 | 150篇 |
2016年 | 164篇 |
2015年 | 167篇 |
2014年 | 229篇 |
2013年 | 345篇 |
2012年 | 465篇 |
2011年 | 505篇 |
2010年 | 294篇 |
2009年 | 223篇 |
2008年 | 363篇 |
2007年 | 459篇 |
2006年 | 427篇 |
2005年 | 426篇 |
2004年 | 429篇 |
2003年 | 388篇 |
2002年 | 363篇 |
2001年 | 58篇 |
2000年 | 61篇 |
1999年 | 68篇 |
1998年 | 91篇 |
1997年 | 53篇 |
1996年 | 57篇 |
1995年 | 59篇 |
1994年 | 45篇 |
1993年 | 42篇 |
1992年 | 47篇 |
1991年 | 35篇 |
1990年 | 39篇 |
1989年 | 52篇 |
1988年 | 44篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 24篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 22篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1977年 | 33篇 |
1976年 | 22篇 |
1975年 | 33篇 |
1974年 | 43篇 |
1973年 | 35篇 |
1966年 | 25篇 |
排序方式: 共有7559条查询结果,搜索用时 15 毫秒
21.
Alicja Ewa Ratajczak Aleksandra Szymczak-Tomczak Agnieszka Zawada Anna Maria Rychter Agnieszka Dobrowolska Iwona Krela-Ka
mierczak 《Nutrients》2021,13(1)
Patients suffering from Crohn’s disease and ulcerative colitis are at higher risk of osteoporosis due to lower bone mineral density. Risk factors of osteoporosis are divided into unmodifiable, namely, age, gender, genetic factors, as well as modifiable, including diet, level of physical activity, and the use of stimulants. Coffee and tea contain numerous compounds affecting bone metabolism. Certain substances such as antioxidants may protect bones; other substances may increase bone resorption. Nevertheless, the influence of coffee and tea on the development and course of inflammatory bowel diseases is contradictory. 相似文献
22.
Mr. J. Shimmins A. C. Allison D. A. Smith C. F. Speirs 《Calcified tissue international》1967,1(1):137-143
We have found an approximate solution of a two-compartment kinetic model. The model considered allows exchange of tracer between the two compartments, and loss of this tracer from one compartment. This solution was used to calculate the turnover rates of the two compartments from the retention of the tracer in the model. Hence, by measuring in a whole body counter the retention of an isotope tracer in such a system, it is possible to calculate the turnover rates of the two compartments of the system. Using an English Electric KDF 9 computer to solve 64 stated models, we have been able to define the range of kinetic constants over which the use of the mathematical approximation is justifiable.
Zusammenfassung Wir fanden eine Näherungsgleichung für ein kinetisches 2-Kompartment-Verteilungsmodell. Das Modell erlaubt den Austausch von Tracersubstanzen zwischen zwei Räumen und die Angabe des Tracers aus einem Raum. Die Gleichung wurde verwendent, um die Umsatzrate in den zwei Räumen nach der Retention des Tracers im Modell zu berechnen. Durch Messung der Retention eines Isotops in einem derartigen System mit dem Ganzkörperzähler ist es dann möglich, die Umsatzraten in beiden Verteilungsräumen zu berechnen. Ein English Electric KDF 9 Computer, der 64-stufige Vorlagen löst, ermöglicht es, den Bereich der kinetischen Komponenten zu definieren, über welchen die Verwendung der mathematischen Nährung gerechtfertigt ist.
Résumé Nous avons trouvé une solution approximative d'un modèle cinétique à 2 compartiments. Le modèle considéré perment l'échange du traceur entre 2 compartiments et la perte de ce traceur à partir d'un seul compartiment. Cette solution est utilisée pour calculer les taux de renouvellement des 2 compartiments à partir de la rétention du traceur dans ce modèle. Ainsi, en mesurant la rétention de l'isotope traceur dans un tel système à l'aide d'un comptage «in toto» il est possible de calculer les taux de renouvellement des 2 compartiments du système.En utilisant un calculateur électronique KDF 9 pour résoudre 64 modèles établis, nous avons été capables de préciser les limites des constantes cinétiques dans lesquelles l'utilisation de l'approximation máthématique est justifiée.相似文献
23.
24.
Mathematical models of myelinated nerve fibres are highly stylized abstractions of real nerve fibres. For example, nerve fibres are usually assumed to be perfectly straight. Such idealizations can cause discrepancies between theoretical predictions and experimental results. One well-known discrepancy is that the currently used models predict (contradictory to experimental findings) that an activation of nerve fibres is not possible with a pure transverse electric field. This situation occurs when a magnetic coil is placed symmetrically above a straight nerve fibre for magnetic nerve stimulation, or when an anode and a cathode are placed equidistantly on a line perpendicular to the fibre in the case of electrical stimulation. It is shown that this discrepancy does not occur if the physiological undulation of peripheral nerve fibres is included in the models. Even for small undulation amplitudes (e.g. 0.02 mm), it is possible to activate the fibre in these positions. For physiological undulations, as found in the literature, and favourable (off-centre) positions, the typical reduction of the thresholds is in a range between one and five, compared with perfectly straight fibres. 相似文献
25.
Mr. M. C. Winslet M.S. F.R.C.S. Denise Youngs B.Sc. D. W. Burdon F.R.C.Path. M. R. B. Keighley M.S. F.R.C.S. 《Diseases of the colon and rectum》1990,33(10):878-882
In a prospective, open, randomized controlled trial, 173 patients requiring surgery for potentially contaminated lower gastrointestinal surgery were allocated to receive either two doses of ceftizoxime (2 gm) with one dose of metronidazole (1.5 gm) or gentamicin 3 mg/kg/day for five days with one dose of metronidazole (1.5 gm). Eighty-nine patients received ceftizoxime and 84 patients received gentamicin. The groups were comparable with respect to diagnosis, procedure, type of anastomosis, and wound closure. The incidence of withdrawal due to failure to respond to the study drug (11.5 percent) was equivalent in the two groups. There was no difference in the overall incidence of postsurgical infection between the ceftizoxime and metronidazole group (22.2 percent) and the gentamicin and metronidazole group (25.7 percent). The incidence of wound infection (ceftizoxime and metronidazole, 6.9 percent; gentamicin and metronidazole, 10 percent) and deep sepsis (ceftizoxime and metronidazole, 15.3 percent; gentamicin and metronidazole, 15.7 percent) was similar. 相似文献
26.
Information about resistant pattern of Mycobacterium tuberculosis isolates against antituberculon drugs is a very important part of tuberculosis control and indicates the directions of TB policy in each country. Poland joined WHO/IUATLD global project on drug resistance surveillance, and carried out the first prospective survey, simultaneously on primary and acquired drug resistance of tuberculosis patients according WHO/IUATLD recommendations. The programme covered the whole country, basing on cooperation between the National Reference Laboratory (NRL) with regional TB laboratories. Questionnaires and cultures were obtained from patients who excreted TB bacilli during the period from 1 November 1996 to 1 November 1997 (12 months). Drug susceptibility testing to INH, SM, EMB and RMP were performed on Lowenstein-Jensen medium according to the proportion method or/and radiometric Bactec 460 TB system. 3970 TB patients bacteriologically confirmed by culture were included in a one-year study. The male to female ratio was 2.6:1. Patients were at the age of 6 to 83 years. Majority of patients (86% males and 77% of females) was older than 35 years. Primary resistance to any drug was found in 3.6% of new cases and 2.4% of those patients who excreted monoresistant strains. No monoresistance to EMB was found. 18 patients (0.6%) were infected by MDR strains. Total resistance in new cases was for INH--2.6%, for SM--1.8%, for RMP--0.7% and for EMB--0.1%. Acquired resistance to any drug was found in 17.0% of treated. Majority of patients--7.7% excreted monoresistant strains. 7.0% were infected by MDR strains. Total resistance to INH was 14.8%, to SM--9.2%, to RMP--7.8%, and to EBM--2.5%. No correlation was found between sex and primary resistance rates. Among new cases, 3.7% of males and 3.3% of females were infected with resistant strains. However, among treated patients, males (20%) excreted resistant strains twice as much as females (9.1%). Mean age of women and men infected with primary and acquired resistant strains was similar. 相似文献
27.
Mr. J. R. McGregor M.D. F.R.C.S. D. H. Reinbach F.R.C.S. S. W. Dahill B.Sc. M.B. Ch.B. P. J. O'Dwyer M.Ch. F.R.C.S.I. 《Diseases of the colon and rectum》1993,36(9):834-839
Viable intraluminal tumor cells can penetrate a clinically intact rodent colonic anastomosis and give rise to perianastomotic tumor growth. The aim of this study was to determine whether transanastomotic cell migration can be prevented by fibrin-based tissue sealant. Following distal colonic transection and reanastomosis with 5/0 silk sutures, Fischer F344 rats were randomly allocated to three experimental groups. In Group A, a circumferential ring of tissue sealant was placed around the serosal surface of the anastomosis; in Group B, sealant was limited to 50 percent of the anastomotic circumference; and, in Group C, no sealant was applied. All rats then had 10 5 Mtln 3 carcinoma cells injected into the proximal colonic lumen via a rectal catheter. The incidence of perianastomotic tumor at 21 days was significantly lower in Group A (3 of 14 animals) than in Group B (11 of 16 rats) (P =0.012; Fisher's exact test) or Group C (10 of 14 rats;P=0.011). A further experiment demonstrated that sealant did not protect the anastomosis when tumor cells were instilled directly into the peritoneal cavity. A topical carcinocidal action therefore appears unlikely, but our results suggest that a circumferential anastomotic ring of fibrin sealant forms an effective mechanical barrier preventing intraluminal tumor cells from reaching the peritoneal cavity. 相似文献
28.
B. B. Mršulja B. J. Mršulja M. Spatz U. Ito J. T. Walker Jr. I. Klatzo 《Acta neuropathologica》1976,36(1):1-8
Summary Behaviour of biogenic amines was studied in the brains of Mongolian gerbils subjected to unilateral occlusion of the common carotid artery. Assays on the hemispheres ipsilateral to occlusion revealed in symptom-positive animals a progressive decrease in norepinephrine and dopamine, and an increase in serotonin throughout the duration of an ischemic insult. In post-ischemic periods following the release of the clip, changes in biogenic amine levels generally conformed to the principles of a previously described maturation phenomenon, with delayed reactions occurring after the shorter ischemic insults. 相似文献
29.
Mr. Mike Gorman M.A. 《Community mental health journal》1976,12(2):119-127
In 1975, twelve years after enactment of the Community Mental Health Centers Act, we find one of the greatest obstacles to fulfillment of our hopes to be pervasive hostility to acceptance of the mentally ill in many communities. The River Region Program has hurdled this obstacle by breaking the artificially large mental health catchment areas into manageable segments of 16 smaller service areas close to the people it serves in seven counties of Kentucky. In each of these service areas it has involved a broad spectrum of citizens in the planning of every service. All of this is of particular relevance today in light of the Supreme Court's D,onaldson decision, that mentally ill persons cannot be confined involuntarily if they are not dangerous and can live safely in the outside world. The outside world must be prepared to receive these people, and we in the mental health field must do our job in this vital preparation.Mr. Gorman originally presented this paper as a speech at the Annual Dinner, of the River Region Mental Health — Mental Retardation Board in Louisville, Kentucky, on June 20, 1975. 相似文献
30.
Inhibition of cyclooxygenase-2 indirectly potentiates antitumor effects of photodynamic therapy in mice. 总被引:2,自引:0,他引:2
Marcin Makowski Tomasz Grzela Justyna Niderla Maciej ?Azarczyk Pawe? Mróz Maciej Kopeé Magdalena Legat Katarzyna Strusińska Katarzyna Koziak Dominika Nowis Piotr Mrówka Maria Wasik Marek Jakóbisiak Jakub Go?ab 《Clinical cancer research》2003,9(14):5417-5422
PURPOSE: The aim of the present study was to potentiate the antitumor effectiveness of photodynamic therapy (PDT). A cDNA microarray analysis was used to evaluate the gene expression pattern after Photofrin-mediated PDT to find more effective combination treatment with PDT and inhibitor(s) of the identified gene product(s) overexpressed in tumor cells. EXPERIMENTAL DESIGN: Atlas Mouse Stress Array was used to compare the expression profile of control and PDT-treated C-26 cells. The microarray results have been confirmed using Western blotting. Cytostatic/cytotoxic in vitro assay as well as in vivo tumor models were used to investigate the antitumor effectiveness of PDT in combination with cyclooxygenase (COX) 2 inhibitors. RESULTS: PDT induced the expression of 5 of 140 stress-related genes. One of these genes encodes for COX-2, an enzyme important in the tumor progression. Inhibition of COX-2 in vitro with NS-398, rofecoxib, or nimesulide, or before PDT with nimesulide did not influence the therapeutic efficacy of the treatment. Administration of a selective COX-2 inhibitor after PDT produced potentiated antitumor effects leading to complete responses in the majority of treated animals. CONCLUSIONS: COX-2 inhibitors do not sensitize tumor cells to PDT-mediated killing. However, these drugs can be used to potentiate the antitumor effectiveness of this treatment regimen when administered after tumor illumination. 相似文献