全文获取类型
收费全文 | 2175篇 |
免费 | 87篇 |
国内免费 | 31篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 95篇 |
妇产科学 | 19篇 |
基础医学 | 421篇 |
口腔科学 | 77篇 |
临床医学 | 249篇 |
内科学 | 505篇 |
皮肤病学 | 112篇 |
神经病学 | 39篇 |
特种医学 | 266篇 |
外科学 | 179篇 |
综合类 | 49篇 |
预防医学 | 74篇 |
眼科学 | 25篇 |
药学 | 138篇 |
中国医学 | 1篇 |
肿瘤学 | 41篇 |
出版年
2015年 | 24篇 |
2014年 | 19篇 |
2013年 | 76篇 |
2012年 | 28篇 |
2010年 | 44篇 |
2009年 | 30篇 |
2008年 | 22篇 |
2007年 | 44篇 |
2006年 | 44篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 25篇 |
2002年 | 19篇 |
2001年 | 31篇 |
2000年 | 24篇 |
1999年 | 37篇 |
1998年 | 82篇 |
1997年 | 95篇 |
1996年 | 105篇 |
1995年 | 70篇 |
1994年 | 73篇 |
1993年 | 76篇 |
1992年 | 39篇 |
1991年 | 36篇 |
1990年 | 41篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 48篇 |
1986年 | 51篇 |
1985年 | 38篇 |
1984年 | 55篇 |
1983年 | 27篇 |
1982年 | 31篇 |
1981年 | 37篇 |
1980年 | 49篇 |
1979年 | 23篇 |
1978年 | 27篇 |
1977年 | 35篇 |
1976年 | 38篇 |
1975年 | 36篇 |
1972年 | 24篇 |
1971年 | 21篇 |
1970年 | 23篇 |
1965年 | 50篇 |
1964年 | 50篇 |
1963年 | 47篇 |
1962年 | 41篇 |
1961年 | 40篇 |
1960年 | 65篇 |
1959年 | 20篇 |
排序方式: 共有2293条查询结果,搜索用时 15 毫秒
21.
Mahadevaiah SK; Odorisio T; Elliott DJ; Rattigan A; Szot M; Laval SH; Washburn LL; McCarrey JR; Cattanach BM; Lovell-Badge R; Burgoyne PS 《Human molecular genetics》1998,7(4):715-727
An RNA-binding motif (RBM) gene family has been identified on the human Y
chromosome that maps to the same deletion interval as the 'azoospermia
factor' (AZF). We have identified the homologous gene family (Rbm) on the
mouse Y with a view to investigating the proposal that this gene family
plays a role in spermatogenesis. At least 25 and probably >50 copies of
Rbm are present on the mouse Y chromosome short arm located between Sry and
the centromere. As in the human, a role in spermatogenesis is indicated by
a germ cell-specific pattern of expression in the testis, but there are
distinct differences in the pattern of expression between the two species.
Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are
female due to a position effect resulting in non-expression of Sry ;
sex-reversing such mice with an Sry transgene produces males with a high
incidence of abnormal sperm, making this the third deletion interval on the
mouse Y that affects some aspect of spermatogenesis. Most of the copies of
Rbm map to this deletion interval, and the Yd1males have markedly reduced
Rbm expression, suggesting that RBM deficiency may be responsible for, or
contribute to, the abnormal sperm development. In man, deletion of the
functional copies of RBM is associated with meiotic arrest rather than
sperm anomalies; however, the different effects of deletion are consistent
with the differences in expression between the two species.
相似文献
22.
Peter A. Shapiro Richard P. Sloan Emilia Bagiella J. Thomas Bigger JR. Jack M. Gorman 《Psychophysiology》1996,33(1):54-62
Heart rate reactivity to mental stress is substantially blunted early after heart transplantation, suggesting that the loss of neural modulation limits the cardiovascular response to mental stress. We tested whether reactivity to mental stress recovers during the first year after heart transplantation. Hemodynamic and respiratory responses to mental arithmetic challenge were studied in 20 heart transplant recipients 3, 6, and 12 months after surgery. A normal comparison group was studied at equivalent intervals. Heart rate reactivity to mental arithmetic was significantly reduced in the cardiac transplant group compared to the normal subjects. This effect persisted up to 1 year after transplantation. Heart period variability in the heart transplant recipients was minimal in all three-test sessions. The findings suggest that no functional reinnervation or other compensatory adaptation occurs up to 1 year after heart transplantation. 相似文献
23.
IgG antibody to gE, the Fc gamma-binding herpes simplex 1 (HSV-1) viral glycoprotein, was studied in 49 rheumatoid arthritis (RA) patients and 43 normal controls. Antibody to gD, another important HSV-1 antigen, was assayed in parallel. No difference between RA patients and normal controls was found in levels of anti-gE antibody measured by reactivity of IgG F(ab')2 fragments reacting with gE coated to ELISA plates. No difference in anti-gD antibody was recorded between normals and patients with RA. Levels of IgG anti-IgE antibody did not correlate with quantitative elevations of serum rheumatoid factor (RF) in RA patients. When IgG anti-gE and anti-gD were assayed in 20 patients with juvenile rheumatoid arthritis and 22 children controls, no significant differences were noted. However, when individual RFs from patients with RA were tested for reactivity against a panel of affinity-isolated F(ab')2 antibodies to gE, some evidence for individual autospecificity was obtained. Four of 20 monoclonal IgM RFs produced from RA patients' B cells showed marked elevations of reactivity with some RA patients' F(ab')2 antibodies to gE. All four of the monoclonal RFs showing this specificity were derived from RA synovial tissue B cells. These findings may provide support for the concept that some RFs in patients with RA show individual specificity for internal image determinants of IgG antibodies to viral Fc gamma-binding proteins. 相似文献
24.
25.
26.
SPARGO P. M.; TAIT A. R.; KNIGNT P.R.; KLING T. F. JR 《British journal of anaesthesia》1987,59(5):640-647
Twenty-four mongrel dogs were anaesthetized with pentobarbitoneand morphine sulphate. Neuromuscular blockade was achieved usingpancuronium. Spinal cord blood flow was measured using the radionuclidemicrosphere and hydrogen washout methods before, during, andfollowing nitroglycerine-induced hypotension. Heart rate, meanarterial pressure, cardiac output, pulmonary capillary wedgepressure, and acid-base balance were determined with each measurement.Mean arterial pressure was reduced by 50%. Spinal cord bloodflow, as measured by the microsphere method, increased duringthe period of hypotension, whereas values obtained using thehydrogen washout method were not significantly different fromthose at normotension. No significant change in spinal cordblood flow was detected by either method after the applicationof spinal distraction. Nitroglycerine acts predominantly onvenous capacitance vessels and it is postulated that perfusionpressure, and therefore flow, is maintained despite a reductionin arterial pressure.
Presented in part at the Anual Meeting of the American Societyof Anesthesiologists, October 1985, San Francisco, California.
*Shackleton Department of Anaesthetics, Southampton GeneralHospital, Shirley, Southampton, Hants SO9 4XY.
Section of Orthopedic Surgery, Madison, Wisconsin. 相似文献
27.
DAVID R. HOLMES JR. DAVID L. HAYES JOEL E. GRAY JOHN MERIDETH 《Pacing and clinical electrophysiology : PACE》1986,9(3):360-370
The effects of magnetic resonance imaging were assessed on four dual chamber and two single chamber pulse generators. The tests were performed with a resistive, water-cooled magnet operating at 0.15 T. The 6.4-MHz radiofrequency (RF) field was operated at a maximum power of 1,000 watts with a period adjusted from 130 to 500 ms. Reed switch closure occurred in all six pulse generators tested when placed near the entrance of the magnetic resonance imaging scanner, and the generators reverted to asynchronous operation unless programmed to the "magnet off" mode. None of the pulse generators exhibited any alterations in programmed parameters or in the ability to be reprogrammed after RF pulsing. When the RF field was turned on, there was no change in the asynchronous paced cycle length in four pulse generators; however, during RF scanning there was rapid cardiac stimulation at the RF pulse period in one single chamber and one dual chamber pulse generator. 相似文献
28.
SCHOENIG GERALD P.; HARTNAGEL RALPH E. JR.; SCHARDEIN JAMES L.; VORHEES CHARLES V. 《Toxicological sciences》1993,21(3):355-365
The neurotoxic potential of N,N-diethyl-m-toluamide (DEET) wasevaluated following acute oral administration or following multigenerationplus chronic dietary administration to the rat. For the acutestudy, rats were administered undiluted DEET at dose levelsof 50, 200, or 500 mg/kg by gavage. A dose level of 500 mg/kgwas considered to be the highest practical dose that could beevaluated in this study based upon observations of overt toxicityat 500 mg/kg and mortality at 1000 mg/ kg in a dose range-findingstudy. The two measures of neurotoxicity evaluated in the acutestudy were functional observational battery (FOB) and motoractivity measurements. An apparent treatment-related effectin thermal response time (increased) was noted for both sexes1 hr after dosing at the 500 mg/kg dose level. A questionableeffect on rearing activity (decreased) also was noted at thesame dose level. For the multigeneration plus chronic dietaryadministration study, rats were administered DEET at dietaryconcentrations of 0, 500, 2000, or 5000 ppm continuously overtwo generations and then chronically for 9 months. A dietaryconcentration of 5000 ppm meets the criteria for a maximum tolerateddose (MTD) based on traditional chronic toxicology assessments.Evaluations included FOB, motor activity, discriminative acquisitionand reversal in an Mmaze, acoustic startle habituation, passiveavoidance acquisition and retention, and microscopic examinationof central and peripheral nervous tissue. The only effect thatwas considered to be possibly treatment-related was a slightincrease in exploratory locomotor activity at the 5000 ppm doselevel. Based on the results of these studies, the nervous systemdoes not appear to be a selective target when DEET is administeredto rats either as a single oral dose at high dose levels orchronically at the MTD. 相似文献
29.
Reproductive and Thyroid Effects of Low-Level Polychlorinated Biphenyl (Aroclor 1254) Exposure 总被引:4,自引:0,他引:4
As little information is available on the adverse effects ofpolychlorinated biphenyls (PCBs) on the reproductive systemof the male rat, the current study was conducted to evaluatethe effects of subchronic administration of the PCB mixtureAroclor 1254 on testicular gamete production and endocrine function.The thyroid hormone thyroxine (T4), which is critical for reproductionand development, was also measured because of the well-documentedeffects of PCBs on this hormone. Weanling (31-day-old) maleFischer rats were administered 0, 0.1, 1, 10, or 25 mg/kg/dayAroclor 1254 by gavage for 5, 10, or 15 weeks and necropsied.The hormones testosterone (T) and thyroxine were measured inthe serum, and body weight and weights of the liver, kidney,testes, seminal vesicle plus coagulating gland, cauda epididymides,and pituitary were taken. At 10 and 15 weeks, testicular interstitialfluid (IF) was collected and T concentration in the IF was measured.Sperm motility was measured from a caudal sperm sample and spermnumbers in the testis and cauda epididymis were determined.In addition, tissues were examined microscopically for histopathologicalalterations. In the high-dose group, body, seminal vesicle,cauda epididymal, and pituitary weights were depressed at 10and 15 weeks and cauda epididymal sperm numbers were reducedafter 15 weeks of dosing. In contrast, testes weights, testicularsperm numbers, sperm motility, and serum and testicular testosteronelevels were unaffected, even in the highest dose group (25 mg/kg/day).Aroclor 1254 administration produced histological alterationsin the liver and kidney at doses of 1.0 mg/kg/day and above.These results indicate that the testis of the rat is not a specifictarget organ for Aroclor 1254. In contrast, serum T4 levelswere reduced by Aroclor 1254 administration at a dose 250-foldbelow the dose that failed to alter testicular function. SerumT4 levels were depressed 25% in the 1 mg/kg dose group after5 weeks of exposure and 30% in the 0.1 mg/kg group following15 weeks of exposure. T4 levels were undetectable in the twohighest (10 and 25) dose groups at all intervals. The fact thatthe decreases in T4 were generally concurrent with increasesin liver weight suggested that Aroclor 1254 altered T4 levelsby increasing the turnover rate in the serum by enhancing themetabolism of T4 by the liver. The reduction in serum T4 reportedhere occurred at a dose 25-fold lower than the dose generallyrecognized as affecting thyroid hormone levels. 相似文献
30.
LEVIER DAVID G.; MCCAY J. ANN; STERN MALVIN L.; HARRIS LOUIS S.; PAGE DENNIS; BROWN RONNETTA D.; MUSGROVE DEBORAH L.; BUTTERWORTH LEON F.; WHITE KIMBER L. JR.; MUNSON ALBERT E. 《Toxicological sciences》1994,22(4):525-542
This study was undertaken to investigate a number of immuneparameters which may be compromised with exposure to morphinesulfate. Mice were implanted subcutaneously with 8-, 25-, or75-mg morphine sulfate pellets. Placebo pellets of identicalmakeup to the 75-mg morphine pellet (without morphine of course)were used as a control. Twenty-four hours after implantationof a 75-mg morphine pellet, blood levels reached a peak of 1610ng/ml. Corticosterone increased in parallel with morphine andreached a peak level of 966 ng/ml 24 hr after implantation.The dose response of morphine to increase corticosterone, however,was fiat. The weight of the lymphoid organs, spleen and thymus,and the liver were significantly reduced in the morphine-treatedgroups. Morphine treatment was associated with an increase inserum albumin, SGPT, BUN, and alkaline phosphatase indicativeof hepatic damage. In contrast to increased serum proteins,the C3 component of complement was reduced in a dose-dependentmanner. Leukocyte number in the peripheral blood was significantlyreduced, while erythro-cyte number and hematocrit were bothincreased. The number of B cells and T cells was decreased inmorphine-treated animals. However, the percentage of T cellsrelative to B cells was increased. The primary IgM antibodyresponse to the T-depen-dent antigen, sheep red blood cells,was decreased. Natural killer cell activity was reduced in responseto morphine, as was the phagocytic capacity of Kupffer cells.Host-resistance models of Listeria monocytogenes or Streptococcuspneumoniae showed an increased resistance following administrationof morphine. This increased host resistance, however, was notdue to an increase in antimicrobial action of sera obtainedfrom mice treated with morphine. The majority of morphine'seffects on the immune system exhibited a flat dose response,suggesting that these effects may be mediated secondarily throughcorticosterone. 相似文献