全文获取类型
收费全文 | 2602篇 |
免费 | 226篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 59篇 |
儿科学 | 149篇 |
妇产科学 | 91篇 |
基础医学 | 286篇 |
口腔科学 | 116篇 |
临床医学 | 278篇 |
内科学 | 446篇 |
皮肤病学 | 85篇 |
神经病学 | 50篇 |
特种医学 | 254篇 |
外科学 | 567篇 |
综合类 | 47篇 |
预防医学 | 130篇 |
眼科学 | 45篇 |
药学 | 104篇 |
中国医学 | 5篇 |
肿瘤学 | 146篇 |
出版年
2023年 | 14篇 |
2022年 | 15篇 |
2021年 | 25篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 56篇 |
2017年 | 53篇 |
2016年 | 51篇 |
2015年 | 74篇 |
2014年 | 107篇 |
2013年 | 139篇 |
2012年 | 100篇 |
2011年 | 90篇 |
2010年 | 111篇 |
2009年 | 124篇 |
2008年 | 81篇 |
2007年 | 102篇 |
2006年 | 88篇 |
2005年 | 79篇 |
2004年 | 80篇 |
2003年 | 63篇 |
2002年 | 82篇 |
2001年 | 86篇 |
2000年 | 70篇 |
1999年 | 63篇 |
1998年 | 115篇 |
1997年 | 100篇 |
1996年 | 102篇 |
1995年 | 73篇 |
1994年 | 76篇 |
1993年 | 40篇 |
1992年 | 23篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 44篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 41篇 |
1985年 | 34篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 25篇 |
1980年 | 16篇 |
1979年 | 19篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1974年 | 15篇 |
排序方式: 共有2858条查询结果,搜索用时 218 毫秒
41.
Anderson RA; Wallace AM; Kicman AT; Wu FC 《Human reproduction (Oxford, England)》1997,12(8):1657-1662
Administration of supraphysiological doses of testosterone to normal men
causes inhibition of spermatogenesis, but while most become azoospermic,
30-55% maintain a low rate of spermatogenesis. We have investigated whether
there are differences in endogenous androgen production, of testicular and
adrenal origin, which may be related to the degree of suppression of
spermatogenesis. Thirty-three healthy Caucasian men were given weekly i.m.
injections of 200 mg testosterone oenanthate (TE), 18 became azoospermic,
while 15 remained oligozoospermic. Urinary excretion of epitestosterone, a
specific testicular product, was reduced to <10% of pretreatment values,
with no differences between the groups. Similar results were obtained for
other markers of testicular steroidogenesis. Urinary and plasma adrenal
androgens were also reduced during TE treatment: a statistically
significant decrease in both (P < 0.001 and P < 0.05 respectively)
was seen in the azoospermic but not oligozoospermic responders. These
results suggest that testicular steroidogenesis is decreased to <10% by
the administration of supraphysiological doses of exogenous testosterone.
Differences in the degree of ongoing steroidogenesis in the testis do not
appear to account for incomplete suppression of spermatogenesis, thus
differences in androgen metabolism may underlie this heterogeneous
response. A small but significant reduction in secretion of adrenal
androgens was also detectable, the relevance of which is unclear.
相似文献
42.
H. Seibold U. Roth R. Lippert J. Kohler S. Wieshammer E. Henze M. Stauch 《Journal of molecular medicine (Berlin, Germany)》1986,64(9):433-441
Summary In patients with varying degrees of chronic obstructive pulmonary disease (COPD), simultaneous measurements of central hemodynamics and left ventricular radionuclide ventriculograms at rest and during exercise were made. In 21 of these patients, satisfactory echocardiograms could be performed. In seven of the patients, arterial blood pressure at rest was increased. Decreased compliance of the left ventricle was thought to be present in patients with COPD and additional arterial hypertension. The left ventricular ejection fraction (LVEF) at rest was in the high normal range in all patients. During exercise, no further increase was observed. This pattern of LVEF response seems to be typical in patients with COPD. Because the highest values were observed in the more severe COPD and right ventricular hypertrophy, it is unlikely that an impairment of left ventricular function is caused by COPD. In five of 27 patients, an abnormal decrease of LVEF and regional hypokinesis occurred during exercise, thus suggesting additional coronary heart disease. The fact that at least 30% of the patients with COPD suffered from arterial hypertension and 20% of the patients exhibited unexpected ischemia detected by regional hypokinesis in RNV during exercise, but not in the ECG, may be of practical relevance. Coronary angiography was not indicated because most of these patients were over 65 and the factor limiting the working capacity was ventilatory impairment and not angina pectoris, in all patients. For this reason, a diagnostic uncertainty remains with regard to additional coronary heart disease in the older patients with advanced chronic obstructive pulmonary disease.Lung Function Parameters VC (1)
inspiratory vital capacity
- FEV1 (1)
forced exspiratory volume in 1 sec
- Raw (cmH20/l/s)
airways resistance
- RV/TLC (%)
residual volume/total lung capacity
- paO2 (mm Hg)
O2 partial pressure
Hemodynamic Parameters CI (1/min/sqm)
cardiac index
- SVI (ml/sqm)
stroke volume index
- PAP (mm Hg)
pulmonary artery mean pressure
- PwP (mm Hg)
pulmonary capillary wedge pressure
- RRs (mm Hg)
systolic arterial pressure
- RRd (mm Hg)
diastolic arterial pressure (at the time of catheterization)
- RR(WHO) (mm Hg)
mean values measured at different days (at least 3 values).
Parameters Derived from Combined Radionuclide Ventriculography and Central Hemodynamics LVEF (%)
left ventricular ejection fraction
- LVESVI (ml/sqm)
left ventricular endsystolic volume index
- P/V (mm Hg/ml/sqm)
peak systolic pressure/endsystolic volume index
- PFR (1/sec)
peak filling rate: endsystolic volume/sec
Echocardiographic Parameters RV d wth (mm)
right ventricular enddiastolic wall thickness
- LV d wth (mm)
left ventricular enddiastolic wall thickness
In honor to Prof. W.E. Adam's 60th birthday 相似文献
43.
Time course of hypo-osmotic swellings of human spermatozoa: evidence of ordered transition between swelling subtypes 总被引:2,自引:1,他引:2
Hossain AM; Rizk B; Barik S; Huff C; Thorneycroft IH 《Human reproduction (Oxford, England)》1998,13(6):1578-1583
The hypo-osmotic swelling test (HOST or HOS test) usually takes into
consideration the total HOS response value with no emphasis either on the
value of the response subtypes or the response evaluation time. This study
investigated the time course of HOS responses and analysed their
physiological relevance. Raw semen spermatozoa and Percoll washed
spermatozoa were used in the experiment. The morphological changes in the
sperm tail were monitored by incubating the spermatozoa in the hypo-
osmotic solution for 16 different time periods. The HOS reactive
spermatozoa and the type of HOS reaction (swelling subtypes) of the samples
subjected to different duration of treatment were identified under a phase
contrast microscope. Also the fate of individual spermatozoa in a
hypo-osmotic environment were monitored for 30 min. In spermatozoa exposed
to a hypo-osmotic solution, the motility lasted usually less than 2 min and
motility characteristics were uniquely different from that of the
spermatozoa under iso-osmotic conditions. The HOS response development was
permanent but the motility loss due to hypo-osmotic shock was reversible up
to 1 min of incubation. There was an indication of ordered transition among
the HOS swelling subtypes apparently initiating with subtype b destined to
c, d, e, f and g. Further, the subtypes a and g showed gradual decrease and
increase, respectively, while subtype b showed abrupt initial increase and
then gradual decrease. Transition from b to g could be direct or via one or
more than one subtypes. Ultrastructure based analysis indicated that HOS
response subtypes are the apparent reflection of the differences in the
cytoskeletal assembly of the sperm tail and thus may be identifying
different physiological variants in the sperm population. These results
indicate that shorter incubation is essential to document the kinetics of
various HOS responses but the conventional HOS test misses these important
HOS features because of lengthy incubation. Since the time course of
ordered transition of HOS responses will vary more than the total HOS
response in semen of different aetiologies, the importance of HOS response
subtypes and response evaluation time should be taken into consideration
when applying HOS test.
相似文献
44.
Jon D Larson Shannon A Wadman Eleanor Chen Lesa Kerley Karl J Clark Mark Eide Sarah Lippert Aidas Nasevicius Stephen C Ekker Perry B Hackett Jeffrey J Essner 《Developmental dynamics》2004,231(1):204-213
We have identified the zebrafish homologue of VE-cadherin and documented its expression in the developing vascular system. The zebrafish VE-cadherin gene is specifically expressed in the vascular endothelial cell lineage beginning with the differentiation and migration of angioblasts and persists throughout vasculogenesis, angiogenesis, and endocardium development. Staining zebrafish embryos by whole-mount in situ hybridization with the VE-cadherin probe provides a method to screen embryos for vascular defects. To illustrate this utility, we used VE-cadherin expression to demonstrate a conservation of vascular endothelial growth factor-A (VEGF-A) function. The morpholino antisense oligonucleotide knockdown of VEGF-A function in zebrafish embryos results in a loss of angiogenic blood vessels, as indicated by the lack of VE-cadherin expression in the intersegmental vasculature. This loss can be restored in embryos supplemented with either zebrafish or human VEGF-A, the latter indicating that genes crucial to angiogenesis have highly conserved functional activities in vertebrates. 相似文献
45.
The effect of ovarian steroids on epithelial ciliary beat frequency in the human Fallopian tube 总被引:3,自引:3,他引:3
Mahmood T; Saridogan E; Smutna S; Habib AM; Djahanbakhch O 《Human reproduction (Oxford, England)》1998,13(11):2991-2994
Using a method that detects variations in light intensity we have studied
the effect of ovarian steroids on human Fallopian tube epithelial ciliary
beat frequency in vitro. We have found that baseline ciliary beat frequency
averages between 5-6 Hz. Cilia from ampullary segments of the Fallopian
tube beat significantly faster (5.4 Hz+/-0.2) than those from fimbrial
segments (4.8 Hz+/-0.2). There was no significant difference in baseline
ciliary beat frequency at any other anatomical site in the Fallopian tube.
Incubation with progesterone (10 micromol/l) suppresses human Fallopian
tube epithelial ciliary beat frequency by 40-50%. This inhibition was
observed at similar magnitudes in all Fallopian tubes studied irrespective
of anatomical site. Progesterone-induced reductions in ciliary beat
frequency were concentration dependent and prevented by the progesterone
receptor antagonist mifepristone (RU486). Oestradiol alone (10 micromol/l)
had no effect on ciliary beat frequency at any anatomical site in the
Fallopian tube but did prevent the reduction in ciliary beat frequency seen
with progesterone when tissues were incubated with these two steroids
together.
相似文献
46.
47.
48.
A human homologue of Drosophila minibrain (MNB) is expressed in the neuronal regions affected in Down syndrome and maps to the critical region 总被引:4,自引:0,他引:4
49.
50.
A storage telemetrical method using thermoluminescent (TL) dosimeters for long-term measurements of incorporated radioactive substances in unrestrained rats has been developed. The system has been used in combination with radiotelemetrical registration of the circadian temperature rhythm. By sequential replacement of double TL dosimeters (60 mg, CaSO4:Dy) through an implanted silicon tube, the concentration of different radionuclides can be determined over long periods. The persistence of the circadian temperature rhythm indicates that the animals were unaffected by the experimental conditions. The relative uncertainty of the dosimeter system and the temperature transmitter is approximately +/- 2% (SD) at 5 mR exposures and +/- 0.05 degrees C, respectively. The weight of the system in total is 5.7 g. Disappearance studies (36-48 h) have been performed with the beta-emitters, 32P nad 42K, in subcutaneous tissues and tumor tissue. This TL method permits the repetition of an experiment on the same rat several times, and thereby avoids errors due to biological variations between animals. 相似文献