全文获取类型
收费全文 | 5563篇 |
免费 | 461篇 |
国内免费 | 33篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 181篇 |
妇产科学 | 77篇 |
基础医学 | 835篇 |
口腔科学 | 66篇 |
临床医学 | 567篇 |
内科学 | 1376篇 |
皮肤病学 | 111篇 |
神经病学 | 651篇 |
特种医学 | 450篇 |
外国民族医学 | 1篇 |
外科学 | 611篇 |
综合类 | 89篇 |
一般理论 | 1篇 |
预防医学 | 364篇 |
眼科学 | 116篇 |
药学 | 298篇 |
中国医学 | 2篇 |
肿瘤学 | 222篇 |
出版年
2021年 | 56篇 |
2020年 | 41篇 |
2019年 | 68篇 |
2018年 | 78篇 |
2017年 | 53篇 |
2016年 | 54篇 |
2015年 | 68篇 |
2014年 | 103篇 |
2013年 | 147篇 |
2012年 | 235篇 |
2011年 | 262篇 |
2010年 | 159篇 |
2009年 | 121篇 |
2008年 | 221篇 |
2007年 | 232篇 |
2006年 | 199篇 |
2005年 | 243篇 |
2004年 | 195篇 |
2003年 | 190篇 |
2002年 | 176篇 |
2001年 | 191篇 |
2000年 | 199篇 |
1999年 | 162篇 |
1998年 | 91篇 |
1997年 | 98篇 |
1996年 | 71篇 |
1995年 | 66篇 |
1994年 | 59篇 |
1993年 | 45篇 |
1992年 | 147篇 |
1991年 | 134篇 |
1990年 | 160篇 |
1989年 | 136篇 |
1988年 | 124篇 |
1987年 | 116篇 |
1986年 | 121篇 |
1985年 | 112篇 |
1984年 | 90篇 |
1983年 | 66篇 |
1982年 | 66篇 |
1981年 | 52篇 |
1980年 | 52篇 |
1979年 | 83篇 |
1978年 | 63篇 |
1977年 | 52篇 |
1976年 | 55篇 |
1975年 | 41篇 |
1974年 | 35篇 |
1973年 | 52篇 |
1970年 | 39篇 |
排序方式: 共有6057条查询结果,搜索用时 15 毫秒
61.
J T McClintock M Mosher S R Thaker W K Wacker D Jones M Forman S P Adler P Charache F E Taub 《Journal of virological methods》1991,35(1):81-91
Using probes consisting of horseradish peroxidase (HRP) directly attached to DNA, scrapings or trypsinized cells from 217 adequate clinical samples were cultured and analyzed in 3 blind studies by in situ hybridization for the presence of cytomegalovirus (CMV) and herpes simplex virus (HSV). Sixty samples were judged inadequate due to insufficient cell numbers; however, this problem was significantly decreased during the course of the study. One hundred and eighteen samples were found positive and 70 samples were found negative for CMV. Scrapings of cultured cells from 29 clinical samples revealed 9 samples which were positive and 20 samples which were negative for HSV. Forty-two additional samples, containing either uninfected cells or cells infected with various strains of CMV, were analyzed for the ability of the HRP-DNA CMV probe to detect such isolates. Twenty samples were positive and 22 negative for CMV. No false-negatives or false-positives were observed for either CMV or HSV. In addition to the specificity noted above neither the CMV nor the HSV DNA probe hybridized to potential contaminants found in clinical specimens. 相似文献
62.
R Silberberg M Aufdermaur J H Adler 《Archives of pathology & laboratory medicine》1979,103(5):231-235
Aging sand rats (Psammomys obesus) kept on a standard laboratory diet supplemented by salt bush--their natural source of food--were examined for changes of the vertebral column. From about 6 months of age on, degeneration of the intervertebral disks was noted. The changes increased in severity with increasing age, and from 1 1/2 years of age on, massive multiple disk herniations were seen. Associated with these lesions were spondylosis of "intervertebral" as well as hyperostotic type, and osteoarthrosis of the apophyseal joint. The sand rat seems to be an excellent model for the study of the pathogenesis of spinal diseases associated with the aging process. 相似文献
63.
V Bogomolski-Yahalom E Granot N Linder R Adler S Korman N Manny R Tur-Kaspa D Shouval 《Journal of medical virology》1991,34(4):217-222
Israel has no official prevention policy at present against perinatal and horizontal transmission of hepatitis B virus (HBV) infection in newborns and children at risk. The present study was designed to assess the prevalence of HBV carrier state in a population of 11,123 pregnant women at term. Among this population (mean age 29.7 +/- 5.9), 98 women (0.88%) were found to be asymptomatic HBsAg+ carriers, and 97% of these carriers were anti-HBe+. Evidence for HBV replication, as determined by serum HBV-DNA, was established in 6.6% of the HBsAg+/anti-HBe+ population. The HBsAg carrier rate was strongly influenced by religion, continent, and country of birth of the carrier mothers. The highest relative carrier rate was found among women of Moslem origin (4.3%), as compared to Jewish women (0.67%). Most carrier women were born in Israel (56.1%) to mothers who had emigrated from regions with intermediate or high endemicity of HBV, such as North Africa or the Middle East. In these groups, the HBsAg carrier rate ranged between 1.2 and 3.0%. Ninety-three percent of newborns receiving passive/active vaccination against HBV developed protective levels of anti-HBs. Finally, evidence for horizontal transmission of HBV was found in 19.3% of 83 non-vaccinated children in families of HBsAg carriers. The present study therefore establishes HBsAg prevalence rates in specific risk groups of women at term and confirms the need for an official policy on immunization against HBV in Israel. Since over 50% of women at term belong to the defined risk groups, universal active vaccination of the entire newborn population each year is suggested as the most rational and needed policy in Israel. 相似文献
64.
65.
Substance P and somatostatin metabolism in sympathetic and special sensory ganglia in vitro 总被引:4,自引:0,他引:4
Mechanisms regulating the content of the putative peptide transmitters, substance P and somatostatin, were examined in several neuronal populations in culture. Substance P levels increased more than 25-fold within 48 h in sympathetic neurons in the explanted rat superior cervical ganglion, and remained elevated for 4 weeks. Identity of the peptide was authenticated by combined high pressure liquid chromatography-radioimmunoassay. Veratridine prevented the increase of substance P in vitro, and tetrodotoxin blocked the veratridine effect, suggesting that sodium ion influx and membrane depolarization prevent peptide elevation. Veratridine (or potassium)-induced membrane depolarization released substance P into the culture medium through a calcium-dependent process. Consequently, at least some veratridine effects are attributable to release and subsequent depletion of ganglion peptide. However, the inhibitory effects of veratridine were far greater than could be accounted for by the quantity of peptide released, suggesting a separate influence on net synthesis (synthesis less catabolism) of substance P. Viewed in conjunction with previous in vivo studies, our observations suggest that trans-synaptic impulses, through the mediation of postsynaptic sodium flux, release substance P from sympathetic neurons and also regulate intracellular peptide metabolism. To determine whether the processes regulating substance P in sympathetic neurons reflect generalized mechanisms, a different peptide, somatostatin, was examined in sympathetic neurons; moreover, substance P was examined in a different neuronal population, special sensory neurons in the nodose ganglion. Substance P levels increased significantly in both sympathetic and sensory neurons after explantation, and somatostatin levels increased in sympathetic neurons. In each instance, the increase was dependent upon the presence of the calcium ions. Moreover, these increases were all prevented by veratridine, in a tetrodotoxin-sensitive manner. Our observations suggest that common regulatory mechanisms govern peptide transmitter metabolism in diverse neuronal populations. 相似文献
66.
The avian bursa-independent humoral immune system: serologic and morphologic studies 总被引:2,自引:0,他引:2
B J Bryant H E Adler D R Cordy M Shifrine A J DaMassa 《European journal of immunology》1973,3(1):9-15
Chickens injected variously with Mycoplasma gallisepticum organisms or sheep erythrocytes and assayed for specific serum agglutinins were individually evaluated with respect to lymphoid development in spleen, thymus, cecal tonsils, cloaca, and bursa of Fabricius. The examinations were carried out during the period of normal maximal bursa size on chickens which had been chemically bursectomized (CBx) at the 7-day-embryo stage and on intact controls. The embryonic genesis of bursal epithelium was completely prevented in 41 of 43 CBx birds. These bursaless birds nonetheless collectively formed agglutinins in 1 of 30 cases at 10 – 12 days after primary stimulation, in 6 of 26 cases at 22 – 23 days after primary stimulation, and in 15 of 32 cases after secondary stimulation. The titers compared favorably with controls. Agglutinin responsive bursaless birds had secondary follicles in spleen and cecal tonsils and an impressive, if variably subnormal, development of lymphoepithelial tissue. By contrast, agglutinin negative bursaless birds lacked germinal centers and had only moderately to sparsely populated lymphoepithelia. This lymphocyte deficit was especially marked in the proctodeal and urodeal roofs and cecal tonsils. Plasmacytes in bursaless birds were rarely found in spleen but were always found in gut lymphoepithelia in numbers correlating with regional lymphoid cell content. 相似文献
67.
Numerical and structural chromosomal abnormalities detected in human sperm with a combination of multicolor FISH assays 总被引:13,自引:0,他引:13
Baumgartner A Van Hummelen P Lowe XR Adler ID Wyrobek AJ 《Environmental and molecular mutagenesis》1999,33(1):49-58
A pair of multicolor FISH assays (X-Y-21 and A-M-16) was developed for human sperm to simultaneously measure sex ratios; aneuploidies involving chromosomes 1, 16, 21, X, and Y; meiotic diploidies; and structural aberrations involving chromosome 1p. Sex ratios in sperm were not significantly different from unity among healthy men. Baseline frequencies of disomic sperm for chromosomes 1, 8, and 21 were similar (6.7 per 10(4) sperm, 95% CI of 5.6-8.1), suggesting that among these three chromosomes, chromosome 21 was not especially prone to nondisjunction. Frequencies of disomy 16 sperm were significantly lower, however (3.5 per 10(4) sperm, 95% CI of 2.0-6.2; P < 0.02). The baseline frequencies of sperm disomy by FISH for chromosomes 16 and 21 were validated against aneuploidy data obtained by the hamster-egg technique for human sperm cytogenetics. The frequencies of X-X, Y-Y, X-Y ("Klinefelter") sperm and sex-null ("Turner") sperm were 5.5, 5.1, 5.5, and 7.8 per 10(4) sperm, respectively. For chromosomes 16 and 21, the frequencies of nullisomic and disomic sperm were similar, suggesting that gain and loss events occurred symmetrically. However, more gain than loss was reported for chromosomes 1, X, and Y. The frequency of MI and MII diploid sperm (with flagella) was approximately 12 per 10(4) (range 8.3-16.7 per 10(4) sperm). Based on flagella data, the frequency of somatic cells in the semen was estimated to be approximately 1.8 per 10(4) sperm. Loss or gain of a portion of chromosome-arm 1p occurred in 5.5 per 10(4) sperm, and the percentage of sperm carrying structural aberrations within the haploid genome as calculated from FISH (1.4%), was similar to that obtained with the hamster-egg technique. These complementary sperm FISH assays have promising applications in studies of chromosomally abnormal sperm after exposure to occupational, medical, and environmental toxicants. 相似文献
68.
This investigation explored the relationship of socioeconomic status (SES) to physical and mental health in two nationally representative samples of whites and African-Americans. We examined the interrelations among SES variables and assessed their contribution to health for the two racial groups. Throughout, we assessed the contribution of a less traditional indicator of SES-wealth-in the SES-health relationship. As we expected, African-Americans had lower levels of education, household income, and wealth than whites. Unexpectedly, however, the strength of the interrelationships among the three SES indicators did not differ for African-Americans and whites. In addition, we found that SES operated to affect health in a very similar fashion for African-Americans and whites. We found that wealth, in addition to more traditional indicators of SES (education and household income), made a unique and significant contribution to explaining both physical and mental health. Examining relations of different SES indicators to health across groups is critical to eliminating persistent social inequalities in health. 相似文献
69.
The noncytotoxic soluble factor produced by CD8+ T cells inhibits replication of HIV and SIV in vitro and is thought to play a crucial role in combatting infection in vivo. We determined the effect of human CD8+ lymphocytes on the in vitro replication potential of both wild-type and nef-defective mutants of the simian immunodeficiency virus SIVmac251. Although replication of wild-type SIVmac251 in unstimulated human PBMC supplemented with IL-2 was unaffected by the presence of CD8+ T cells, the nef mutants were susceptible to the inhibitory effects. The effect of exogenous IL-2 depended upon the culture conditions: (i) in nonstimulated human PBMC depleted of CD8+ T cells, addition of IL-2 had a positive effect on the growth of the nef-defective viruses; (ii) in total human PBMC, IL-2 appeared to reinforce the CD8+ T-cell-dependent inhibition of the same mutant viruses. This strongly suggests that IL-2 stimulates the noncytotoxic anti-HIV/SIV response of CD8+ cells present in PBMC cultures. PHA stimulation of unfractionated human PBMC overrode the suppression of viral replication by CD8+ T cells. Depletion of activated T cells expressing the IL-2 receptor alpha-chain (CD25+ T cells), present in small amounts in these primary T cell cultures, dramatically reduced viral replication, indicating that the depleted cell population harbors the target cells permissive for viral replication. Furthermore, using neutralizing antibodies we could show that inhibition by the beta-chemokines MIP-1alpha, MIP-1beta, and RANTES and the inhibitory effect of CD8+ lymphocytes on nef mutant SIVmac viruses are harbored on different levels. 相似文献
70.
Travi BL Adler GH Lozano M Cadena H Montoya-Lerma J 《Journal of medical entomology》2002,39(3):451-456
We examined changes in the phlebotomine fauna resulting from human intervention in a tropical dry forest of Northern Colombia where visceral and cutaneous leishmaniases are endemic. A natural forest reserve (Colosó) and a highly degraded area (San Andrés de Sotavento [SAS]) were sampled monthly for 8 mo using Shannon traps, sticky traps, and resting-site collections. Overall abundances were higher in Colosó (15,988) than in SAS (2,324). and species richness of phlebotomines was greater in the forest reserve (11 species) than in the degraded habitat (seven species). Fisher alpha, a measure of diversity, reinforced this trend. Both sand fly communities were dominated by Lutzomyia evansi (Nuòez-Tovar), vector of Leishmania chagasi (Cunha & Chagas), representing 92 and 81% of all captures in Colosó and SAS, respectively. Lutzomyia longipalpis (Lutz & Neiva), the common vector of visceral leishmaniasis, accounted for 4-7% of the sand fly community. Lutzornyia panamensis (Shannon) and Lutzomya gomezi (Nitzulescu), putative vectors of Leishmania braziliensis (Vianna), had low abundances at both study sites. The zoophilic species Lutzomyia cayennensis (Floch & Abonneuc) and Lutzomyia trinidadensis (Newstead) were present in variable numbers according to trapping methods and site. Habitat degradation negatively affected sand fly communities, but medically important species were able to exploit modified environments, thereby contributing to Lishmania endemicity. 相似文献