全文获取类型
收费全文 | 210143篇 |
免费 | 14609篇 |
国内免费 | 3508篇 |
专业分类
耳鼻咽喉 | 2849篇 |
儿科学 | 3784篇 |
妇产科学 | 4314篇 |
基础医学 | 29703篇 |
口腔科学 | 4519篇 |
临床医学 | 21166篇 |
内科学 | 37580篇 |
皮肤病学 | 5212篇 |
神经病学 | 14634篇 |
特种医学 | 10135篇 |
外国民族医学 | 7篇 |
外科学 | 26660篇 |
综合类 | 9465篇 |
现状与发展 | 17篇 |
一般理论 | 89篇 |
预防医学 | 13782篇 |
眼科学 | 5146篇 |
药学 | 18858篇 |
36篇 | |
中国医学 | 4353篇 |
肿瘤学 | 15951篇 |
出版年
2023年 | 1532篇 |
2022年 | 4203篇 |
2021年 | 6867篇 |
2020年 | 4013篇 |
2019年 | 4929篇 |
2018年 | 5891篇 |
2017年 | 4696篇 |
2016年 | 5691篇 |
2015年 | 7798篇 |
2014年 | 9541篇 |
2013年 | 11403篇 |
2012年 | 16898篇 |
2011年 | 16641篇 |
2010年 | 10367篇 |
2009年 | 8608篇 |
2008年 | 12298篇 |
2007年 | 12011篇 |
2006年 | 10908篇 |
2005年 | 10285篇 |
2004年 | 8899篇 |
2003年 | 7925篇 |
2002年 | 6884篇 |
2001年 | 5508篇 |
2000年 | 4928篇 |
1999年 | 3895篇 |
1998年 | 1643篇 |
1997年 | 1287篇 |
1996年 | 1162篇 |
1995年 | 1051篇 |
1994年 | 917篇 |
1993年 | 769篇 |
1992年 | 1753篇 |
1991年 | 1751篇 |
1990年 | 1498篇 |
1989年 | 1363篇 |
1988年 | 1263篇 |
1987年 | 1121篇 |
1986年 | 1102篇 |
1985年 | 949篇 |
1984年 | 692篇 |
1983年 | 605篇 |
1982年 | 427篇 |
1981年 | 404篇 |
1980年 | 362篇 |
1979年 | 592篇 |
1978年 | 446篇 |
1977年 | 416篇 |
1976年 | 365篇 |
1975年 | 353篇 |
1974年 | 388篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The authors studied the cumulative probability of pregnancy for up to 4 consecutive embryo transfer (ET) cycles with ICSI performed for male factor. Transfers could be either fresh or frozen. The clinical pregnancy rate (PR) for the first 4 cycles were similar [44% (61/366); 31% (44/138); 45% (14/31); 44% (4/9)]. Delivery rates were also similar. There was a lower PR on the second retrieval vs. the first retrieval (47% vs. 29%), but this may be related to most of the second retrievals occurring in the second transfer cycle (67%, 31/55); this may be explained by women who were poor responders and required another retrieval without a frozen ET. The majority of transfers in cycle 1 were fresh, whereas cycles 2-4 used primarily frozen-thawed embryos. These data should be helpful for patients requiring IVF with ICSI in deciding to continue with more IVF cycles or consider other 相似文献
22.
Milton G. Mutchnick MD Horchang H. Lee MD 《Alcoholism, clinical and experimental research》1988,12(1):155-158
Concanavalin A-induced lymphocyte proliferation was studied in 25 patients with alcoholic hepatitis or compensated alcoholic cirrhosis. Nine alcoholics without evidence of liver disease were also evaluated. A nonlinear correlation equation, which was natural logarithmic, was applied to individual dose-response proliferation curves and permitted comparisons between patient groups and controls. The proliferative response in all patient groups was significantly lower when compared to healthy controls and was independent of the presence or absence of liver disease. This suggests that some changes in immune function observed in alcoholics may be linked to the direct effects of alcohol on the immune system rather than to the associated liver disease. 相似文献
23.
A discrete time optimal control for linear time-delay systems is developed to ensure that all closed-loop eigenvalues will lie inside a circular region centred at (β;, 0) with radius α. It is shown that by suitable manipulations the problem can be reduced to a standard discrete time quadratic regulator problem. An illustrative example is included to demonstrate the applicability of the proposed method. 相似文献
24.
25.
Summary— KR31080 (2-butyl-5-methyl-6-(1-oxopyridin-2-yl)-3-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl]methyl]-3H-imidazo[4,5-b] pyridine) is a potent inhibitor of angiotensin type 1 (AT1 ) receptors in rabbit aorta and human recombinant AT1 receptors. In the isolated rabbit thoracic aorta, KR31080 caused a nonparallel shift to the right of the concentration-response curves to angiotensin II (All) with decreased maximal response (pD'2 = 10.1 ± 0.1), but had no effect on the contractile response induced by norepinephrine. KR31080 inhibited specific [125 I]AII binding to rabbit aortic membranes (AT, receptors) and [125 I][Sar1 , Ile8 ]AII binding to human recombinant AT1 receptors in a concentration-dependent manner with IC50 values of 0.84 ± 0.08 nM and 1.92 ± 0.15 nM, respectively, but did not inhibit specific [125 I)AII binding to bovine cerebellum membranes (ÀT2 receptors). In the Scatchard analysis, KR31080 interacted with rabbit aortic AT1 receptors in a competitive manner, similar to losartan. These results demonstrate that KR31080 is a potent and AT1 selective angiotensin receptor antagonist which exerts a competitive antagonism in the [125 I]AII binding assay and insurmountable AT1 receptor antagonism in the functional study. 相似文献
26.
目的了解常用消毒剂及自来水对弓形虫速殖子活力的影响。方法将各种消毒剂分别加入等体积含弓形虫速殖子的小鼠腹水中,在不同时间内观察虫体胎盘蓝(trypanblue)着色率及活动率,并将经消毒剂处理不同时间的速殖予接种昆明鼠,观察速殖子能否在接种鼠体内复苏繁殖,导致小鼠死亡。用类似方法观察自来水时速殖子的影响。结果除甲醛个速殖子在常用浓度的不同消毒剂中,lmin月台盘蓝着色率均为100%,活动率为0。经消毒剂处理1min的速殖子接种小鼠后,各组接种鼠(包括甲醛处理组)无一死亡。经自来水处理4h的速殖子接种小鼠后仍能在小鼠体内复苏繁殖,小鼠于接种1wk内全部死亡。结论弓形虫速殖子对常用消毒剂均很敏感;而在自来水中途殖子可保持感染力4h以上。 相似文献
27.
OBJECTIVE: To determine the most frequent clinical causes of a prolonged activated partial thromboplastin time (APTT) result, and to determine whether a new heparin-removal device (the Hepchek, Pall Biomedical, Glen Cove, NY 11542) is capable of efficiently detecting the causes of these values. DESIGN: A combination of chart review and laboratory testing comparing the criterion standard--the heparin chromogenic substrate assay--with the Hepchek. Laboratory investigations were blinded and controlled. SETTING: Inpatient, acute-care hospital. PATIENTS: A total of 1,000 hospital patients with a variety of hemostatic disorders. MAIN OUTCOME MEASURE: The extent to which the Hepchek accurately identified the etiology of a prolonged APTT result. RESULTS: The APTT was prolonged in 25.2% of samples. The presence of heparin in the sample was confirmed by chromogenic assay or by using the Hepchek heparin-removal filter. The presence of heparin was confirmed in 12.8% of all samples and in more than 50% of all abnormal samples. The cause of the abnormal APTT was often unappreciated by the clinician. Bayesian analysis of the Hepchek's ability to diagnose heparin correctly as the cause of the abnormal APTT showed a sensitivity of 100% and specificity of 99.9%. CONCLUSION: Use of the Hepchek in the routine clinical laboratory is an efficient and rapid method of detecting heparin as a cause of isolated prolonged APTT results, and should reduce demands for unwarranted coagulation analyses and inappropriate treatment with blood products. 相似文献
28.
29.
Previously, we prepared two different monoclonal antibodies (mAbs) against human 4-1BB (CD137): an agonistic mAb BBK-1 and an antagonistic mAb BBK-2. In this paper, we describe the molecular cloning of these two mAbs and present comparisons of their amino acid sequences. cDNAs encoding the heavy (H) and light (L) chains of the two mAbs were cloned by screening of cDNA libraries constructed from hybridomas secreting these mAbs. Comparisons of amino acid sequences of the two mAbs showed that, while the constant regions of the H and L chains were identical between the two mAbs, the variable region showed 45% identity in H chains and 48% identity in L chains. This suggests that these two mAbs recognize different epitopes of 4-1BB and may have different effects on the activity of 4-1BB. 相似文献
30.
B Lu J M Lee R Elliott C F Dreyfus J E Adler I B Black 《Brain research. Molecular brain research》1991,11(3-4):359-362
Nerve growth factor (NGF) gene expression in central nervous system (CNS) glia appears to be associated with active glial growth. To study the underlying molecular mechanisms, we examined the effects of a number of growth-related factors on NGF mRNA expression in glial cultures. Our results suggest that glial membrane interaction, as a consequence of growth, actively inhibits NGF gene expression in CNS glia. 相似文献