全文获取类型
收费全文 | 22320篇 |
免费 | 1693篇 |
国内免费 | 36篇 |
专业分类
耳鼻咽喉 | 225篇 |
儿科学 | 876篇 |
妇产科学 | 586篇 |
基础医学 | 3033篇 |
口腔科学 | 651篇 |
临床医学 | 2549篇 |
内科学 | 4331篇 |
皮肤病学 | 310篇 |
神经病学 | 1806篇 |
特种医学 | 872篇 |
外科学 | 3063篇 |
综合类 | 375篇 |
一般理论 | 43篇 |
预防医学 | 2130篇 |
眼科学 | 342篇 |
药学 | 1391篇 |
1篇 | |
中国医学 | 16篇 |
肿瘤学 | 1449篇 |
出版年
2022年 | 141篇 |
2021年 | 328篇 |
2020年 | 228篇 |
2019年 | 361篇 |
2018年 | 396篇 |
2017年 | 327篇 |
2016年 | 331篇 |
2015年 | 417篇 |
2014年 | 574篇 |
2013年 | 757篇 |
2012年 | 1113篇 |
2011年 | 1204篇 |
2010年 | 644篇 |
2009年 | 543篇 |
2008年 | 1075篇 |
2007年 | 1169篇 |
2006年 | 1089篇 |
2005年 | 1080篇 |
2004年 | 948篇 |
2003年 | 940篇 |
2002年 | 809篇 |
2001年 | 634篇 |
2000年 | 626篇 |
1999年 | 518篇 |
1998年 | 234篇 |
1997年 | 202篇 |
1996年 | 204篇 |
1995年 | 214篇 |
1994年 | 194篇 |
1993年 | 173篇 |
1992年 | 468篇 |
1991年 | 454篇 |
1990年 | 433篇 |
1989年 | 429篇 |
1988年 | 394篇 |
1987年 | 353篇 |
1986年 | 304篇 |
1985年 | 376篇 |
1984年 | 287篇 |
1983年 | 260篇 |
1982年 | 160篇 |
1979年 | 211篇 |
1978年 | 182篇 |
1977年 | 150篇 |
1976年 | 146篇 |
1975年 | 157篇 |
1974年 | 158篇 |
1973年 | 197篇 |
1972年 | 159篇 |
1971年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Adverse mortality experience of a southwestern American Indian community: overall death rates and underlying causes of death in Pima Indians 总被引:1,自引:0,他引:1
As part of an ongoing epidemiologic study, the death rate and causes of death during 1975 through 1984 were determined in Pima Indians who resided in the Gila River Indian Community (GRIC) in 1965 and later. Death certificates were available for 677 of the 681 deaths. In 78% of the deaths, the underlying cause recorded on the death certificate agreed with the cause determined after review of all available relevant records. The age- and sex-adjusted average annual death rate for the GRIC population (1639/100,000) was 1.9 times (95% CI 1.7-2.0) the 1980 rate for the U.S. all races (878/100,000). In Pima males, whose death rate was substantially higher than that of Pima females, the age-adjusted death rate was 2.3 times that in U.S. males, all races. Moreover among males 25-34 years of age, the Pima death rate was 6.6 times that for the U.S. all races. Diseases of the heart and malignant neoplasms caused 59% of U.S. deaths in 1980, but only 19% of GRIC deaths. By contrast, the age- and sex-adjusted mortality rate in the GRIC Pima was 5.9 times the rate of the U.S. all races for accidents, 6.5 times for cirrhosis, 7.4 times for homicide, 4.3 times for suicide, and 11.9 times for diabetes. Tuberculosis and coccidioidomycosis were important causes of death in the Pima, for whom infectious diseases was the tenth leading cause of death. The findings indicate that programs to improve the adverse mortality experience of the GRIC population should emphasize factors related to fatal accidents, alcoholic cirrhosis, homicide, suicide, diabetes mellitus, and infectious diseases. Young Pimas, especially the males, should be the primary focus of such preventive efforts. These findings and recommendations probably apply to many Native American populations. 相似文献
42.
P M Franz S L Anliker J T Callaghan K A DeSante P H Dhahir R L Nelson A Rubin 《Drug metabolism and disposition》1990,18(6):968-973
Racemic picenadol is being tested clinically as an analgesic. The (+)-enantiomer of picenadol is an opioid agonist and the (-)-enantiomer is a weak agonist/antagonist. The disposition of racemic [14C] picenadol was studied in healthy men after a single dose was administered im (N = 3) and orally (N = 5). After the dose, virtually none of the radioactivity that appeared in blood was associated with the red cells. In plasma, approximately 4% of the radioactivity was attributable to the parent drug, the remainder being picenadol glucuronide (approximately 35%) and other metabolites. The t1/2 for total radioactivity was 6 hr, that for the unchanged drug was 3.5 hr. Picenadol was present in plasma almost exclusively as the (+)-enantiomer. However, after incubation with glucuronidase and sulfatase, plasma contained 2 to 4 times more (-)- than (+)-picenadol, indicating that more conjugated (-)-picenadol than conjugated (+)-picenadol was in the plasma. After im and oral administration of [14C]picenadol, plasma levels of radioactivity were generally 10 and 70 times higher than those in saliva, respectively. More than 90% of the administered radioactivity was excreted in the urine, mostly as picendol glucuronide, and lesser amounts of picenadol sulfate and N-desmethylpicenadol sulfate. Only about 1% of the administered dose of picenadol appeared unchanged in urine. The disposition of racemic picenadol in humans was stereoselective, the (-)-picenadol apparently being metabolized preferentially over the (+)-enantiomer. This finding was of particular interest in view of the dissimilar pharmacologic activities of the enantiomers.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
43.
Dr. Richard L. Nelson M.D. 《Diseases of the colon and rectum》1996,39(3):360-360
44.
45.
Minbo Lan Nelson Beghein Nicolas Charlier Bernard Gallez 《Magnetic resonance in medicine》2004,51(6):1272-1278
New electron paramagnetic resonance (EPR) oximetry probes were identified in the class of carbon black materials. These compounds exhibit very high oxygen sensitivity and favorable EPR characteristics for biological applications. At low pO(2), the linewidth is particularly sensitive to changes in oxygen tension (sensitivity of 750 mG/mmHg). The application of the probes for oximetry was demonstrated in vivo: the pO(2) was measured in muscle in which the blood flow was temporarily restricted as well as in tumor-bearing mice during a carbogen breathing challenge. The responsiveness to pO(2) was stable in muscle for at least 3 months. No toxicity was observed using these materials in cellular experiments and in histological studies performed 2, 7, and 28 days after implantation. In view of their EPR characteristics (high sensitivity) as well as the well-characterized production procedure that make them available on a large scale, these probes can be considered as very promising tools for future developments in EPR oximetry. 相似文献
46.
R A Roesel K M Byrne F Hommes J Trefz C Kelloes A M Nelson J E Carroll 《Pediatric neurology》1987,3(1):40-43
Except for two reported patients, increased free sialic acid excretion has been associated with lysosomal storage. This is a report of a child with progressive neurologic deterioration and increased excretion of free sialic acid. Although lysosomal storage was absent, nuclear invagination or inclusions were present. 相似文献
47.
48.
A series of studies designed to define the requirement of normal infants for sulfur-containing amino acids (methionine, cystine) was conducted with formulas providing 3.0, 2.8, 2.6, 2.2 or 1.8 g of isolated soy protein per 100 kcal. The formulas were fed with or without a methionine supplement. Adequacy of the diet was determined by measurement of growth, serum chemical indices and nitrogen balance. Nitrogen balance demonstrated a beneficial effect of methionine supplementation only at the lowest protein concentration (1.8 g/100 kcal). However, measurement of weight gain and/or serum concentrations of urea nitrogen and albumin clearly showed a beneficial effect of methionine supplementation at protein concentrations of 2.2 and 2.6 g/100 kcal. Intakes of sulfur-containing amino acids of 435 and 495 mumol/100 kcal therefore appear inadequate. At higher intakes of protein (2.8 and 3.0 g/100 kcal) there was no beneficial effect of methionine supplementation. Possible exceptions were male infants provided with 3.0 g protein per 100 kcal, in whom weight gain between 8 and 56 d of age was significantly (P less than 0.05) greater with than without a methionine supplement. Based on intakes of sulfur-containing amino acids from the formula providing 2.8 g of isolated soy protein per 100 kcal without methionine supplementation, we conclude that for male infants older than 56 d the requirement for sulfur-containing amino acids is no more than 588 mumol/100 kcal when intake of methionine is 264 mumol/100 kcal. However, it seems possible that such intake fails to meet the requirement in male infants less than 56 d of age. For female infants, regardless of age, 533 mumol/100 of sulfur-containing amino acids per 100 kcal meet the requirement when intake of methionine is 239 mumol/100 kcal. 相似文献
49.
Exposure of ZR-75-1 human breast cancer cells for 48 h to human recombinant interferon alpha (IFN alpha) resulted in increased expression of oestrogen receptors as measured in a whole cell binding assay. This effect was inversely proportional to dose being significant following treatment with 10-100 IU IFN ml-1 and was only observed at a low initial cell plating density. The extent of the increase in oestrogen receptor levels ranged from 1.2- to 7.2-fold following treatment with 10 IU IFN ml-1. No increase in progesterone receptor expression was observed under the same experimental conditions. Concentrations of IFN which increased oestrogen receptor levels had no effect on cell proliferation. IFN (500 IU ml-1) inhibited cell proliferation and the combination of this treatment with tamoxifen (2 microM) had a greater anti-proliferative effect than either drug alone although there was no evidence of synergism. However, a 5-day pretreatment of cells with IFN (10 IU ml-1) markedly sensitised them to the growth-inhibiting effect of a subsequent 6-day exposure to tamoxifen. 相似文献
50.
Ted T Song Michael R Nelson James H Chang Renata J M Engler Badrul A Chowdhury 《Annals of allergy, asthma & immunology》2005,94(5):539-542
BACKGROUND: Epinephrine injected by an autoinjector in the anterolateral aspect of the thigh is the standard of care in the emergency self-treatment of anaphylaxis. In the United States, the autoinjector EpiPen is widely used for the self-treatment of anaphylaxis. OBJECTIVE: To investigate whether EpiPen autoinjector, with a needle length of 1.43 cm, is sufficient for intramuscular delivery of epinephrine in men and women. METHODS: The distance from skin to muscle in the anterolateral aspect of the thigh was measured in 50 men and 50 women who had undergone computed tomography of the thighs for other medical reasons. For each individual, body mass index (BMI; a measure of weight in kilograms divided by the square of height in meters) was also calculated, and the individuals were classified as underweight (BMI, < 18.5), normal (BMI, 18.5-24.9), overweight (BMI, 25.0-29.9), and obese (BMI, > or = 30.0) using standard definition. RESULTS: In the study participants the mean +/- SD distance from skin to muscle was 0.66 +/- 0.47 cm for men and 1.48 +/- 0.72 cm for women (P < .001). One man (obese at a BMI of 42.2) and 21 women (11 obese with a mean BMI of 35.2, 6 overweight with a mean BMI of 30.1, and 4 normal with a mean BMI of 24.5) had a greater distance from skin to muscle than the EpiPen needle length of 1.43 cm. CONCLUSION: The distance from skin to muscle for the anterolateral aspect of the thigh is higher in women compared with men. This difference suggests that EpiPen may not deliver epinephrine to the intramuscular tissue in many women. 相似文献