全文获取类型
收费全文 | 1369篇 |
免费 | 131篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 105篇 |
妇产科学 | 13篇 |
基础医学 | 172篇 |
口腔科学 | 61篇 |
临床医学 | 182篇 |
内科学 | 315篇 |
皮肤病学 | 28篇 |
神经病学 | 51篇 |
特种医学 | 133篇 |
外科学 | 120篇 |
综合类 | 60篇 |
一般理论 | 1篇 |
预防医学 | 48篇 |
眼科学 | 83篇 |
药学 | 52篇 |
肿瘤学 | 79篇 |
出版年
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 25篇 |
2017年 | 13篇 |
2016年 | 30篇 |
2015年 | 28篇 |
2014年 | 32篇 |
2013年 | 56篇 |
2012年 | 41篇 |
2011年 | 55篇 |
2010年 | 54篇 |
2009年 | 55篇 |
2008年 | 54篇 |
2007年 | 64篇 |
2006年 | 45篇 |
2005年 | 45篇 |
2004年 | 24篇 |
2003年 | 32篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 31篇 |
1999年 | 37篇 |
1998年 | 47篇 |
1997年 | 59篇 |
1996年 | 57篇 |
1995年 | 44篇 |
1994年 | 29篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 23篇 |
1990年 | 29篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 22篇 |
1986年 | 42篇 |
1985年 | 32篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1966年 | 3篇 |
排序方式: 共有1511条查询结果,搜索用时 0 毫秒
1.
2.
Haemopoietic growth factors are involved in the production of the various blood cells from progenitors in the bone marrow, making them useful in a range of clinical situations. The genes for several of them have been cloned and their production engineered by recombinant technology, making them widely available. Myeloid growth factors are used to support patients in the aftermath of chemotherapy and bone marrow transplantation and have potential application in the treatment of infectious diseases. Erythropoietin is widely used for patients with anaemia due to failure of marrow production, having established its effectiveness in chronic renal failure. Thrombopoietin has recently been described and may provide a means to alleviate thrombocytopenia. Current indications and areas of recent reappraisal are addressed in this review. 相似文献
3.
4.
P W Collins C N Gutteridge A O'Driscoll S Blair L Jones R Aitchison S M Kelsey R Chopra A Goldstone A C Newland 《Bone marrow transplantation》1992,10(6):499-506
Endothelial cell activation may play a role in thrombotic complications of BMT such as hepatic veno-occlusive disease (VOD), right atrial line thrombosis and microangiopathic haemolysis. To assess this, von Willebrand factor antigen (vWF:ag) was measured in 72 patients (25 allografts, 46 autografts and one syngeneic) during the first 6 weeks post-transplant. There was a significant rise in vWF:ag in both allografts and autografts but a greater increase was seen in the allografts. The changes in vWF:ag did not correlate with changes in C reactive protein showing that this was not merely an acute phase response. vWF multimers were normal in a subgroup of uncomplicated transplants showing that there was no large scale endothelial cell disruption. Patients with VOD did not have changes in vWF:ag that were consistently different from uncomplicated controls. Three of four patients who developed line thrombosis had higher levels of vWF:ag compared with control groups; multimeric structure of the vWF was again normal. These results show that there is endothelial cell activation post-BMT and that this is greater in allografts compared with autografts, thus suggesting a possible mechanism for the higher incidence of VOD in this group. There were no useful predictive markers of VOD or thrombosis in individual patients. 相似文献
5.
6.
7.
The behavioral effects of amphetamine and pentobarbital depend upon the conditions maintaining behavior. For example, amphetamine usually decreases the rate of operant behavior maintained by fixed ratio schedules while pentobarbital either increases it or leaves it unaffected. However, when considerable exertion is required, as in situations that require endurance, amphetamine tends to enhance performance while barbiturates degrade it. These differences complicate predictions of the effects of these two drugs on effortful operants. The present experiment was designed to characterize effortful responding behaviorally and pharmacologically. Cebus monkeys were trained to operate a lever by flexing their arms and extending their legs; this response exerted a force approximating their body weight. This operant was maintained by a multiple fixed ratio fixed interval (Mult FR FI) schedule. The two schedules maintained dramatically different response patterns. The FR schedule maintained vigorous, high rate responding characterized by a narrow IRT distribution centered at 0.5 sec. The FI schedule maintained very low overall rates of responding characterized by a variable IRT distribution with a median of 1.5 to 2 sec. Despite very low rates of responding during the FI component, no consistent rate increases appeared after amphetamine, and 0.3 mg/kg eliminated responding altogether. Pentobarbital increased overall rate but also shifted the interresponse time (IRT) distribution toward longer IRTs. The increase in overall rate arose from an earlier onset of responding during the FI component and occurred simultaneously with response slowing. The present studies do not support suggestions of a generalized enhancement of effortful performance by amphetamine or a generalized degradation by pentobarbital. 相似文献
8.
9.
Silber SJ; Nagy Z; Devroey P; Tournaye H; Van Steirteghem AC 《Human reproduction (Oxford, England)》1997,12(11):2422-2428
The aim of the study was to determine whether a prior diagnostic testicle
biopsy can predict success or failure of testicular sperm extraction (TESE)
with intracytoplasmic sperm injection (ICSI) in patients with
non-obstructive azoospermia caused by testicular failure, and what is the
minimum threshold of sperm production in the testis which must be surpassed
for spermatozoa to reach the ejaculate. Forty- five patients with
non-obstructive azoospermia caused by testicular failure underwent
diagnostic testicle biopsy prior to a planned future TESE-ICSI procedure.
The diagnostic testicle biopsy was analysed quantitatively, and correlated
with the quantitative findings of spermatogenesis in patients with normal
spermatogenesis, as well as with the results of subsequent attempts at
TESE-ICSI. Men with non- obstructive azoospermia caused by germinal failure
had a mean of 0-6 mature spermatids/seminiferous tubule seen on a
diagnostic testicle biopsy, compared to 17-35 mature spermatids/tubule in
men with normal spermatogenesis and obstructive azoospermia. These findings
were the same for all types of testicular failure whether Sertoli cell
only, maturation arrest, cryptorchidism, or post-chemotherapy azoospermia.
Twenty-two of 26 men with mature spermatids found in the prior testis
biopsy had successful retrieval of spermatozoa for ICSI, 12 of their
partners became pregnant, and are either ongoing or delivered. The study
suggests that 4-6 mature spermatids/tubule must be present in the testis
biopsy for any spermatozoa to reach the ejaculate. More than half of
azoospermic patients with germinal failure have minute foci of
spermatogenesis which are insufficient to produce spermatozoa in the
ejaculate. Prior diagnostic testicle biopsy analysed quantitatively (for
the presence of mature spermatids) can predict subsequent success or
failure with TESE-ICSI. Incomplete testicular failure may involve a sparse
multi-focal distribution of spermatogenesis throughout the entire testicle,
rather than a regional distribution. Therefore, it is possible that massive
testicular sampling from many different regions of the testes may not be
necessary for successful TESE-ICSI.
相似文献
10.
β-Lactoglobulin was isolated from infant formulae that were ultra high temperature (UHT) -treated, sterilized or spray-dried. The effect of the isolated β-lactoglobulin on SfaII-fimbriae-mediated adhesion of Escherichia coli to human ileostomy glycoproteins was studied in vitro. β-Lactoglobulin isolated from sterilized formulae was found to perform significantly less well than preparations from spray-dried formulae (p = 0:05). Great heterogeneity was observed in the adhesion inhibitory capacity of β-lactoglobulin isolated from UHT-treated formulae. Therefore, no significant difference was observed between UHT-treated and sterilized formulae or spray-dried formulae (p < 0:10). It can be hypothesized that β-lactoglobulin from spray-dried and some UHT-treated infant formulae may affect the colonization of mucous membranes by E. coli strains causing neonatal septicaemia and meningitis. 相似文献