全文获取类型
收费全文 | 19322篇 |
免费 | 1227篇 |
国内免费 | 640篇 |
专业分类
耳鼻咽喉 | 561篇 |
儿科学 | 377篇 |
妇产科学 | 244篇 |
基础医学 | 2863篇 |
口腔科学 | 767篇 |
临床医学 | 1397篇 |
内科学 | 2515篇 |
皮肤病学 | 315篇 |
神经病学 | 1075篇 |
特种医学 | 360篇 |
外国民族医学 | 2篇 |
外科学 | 2131篇 |
综合类 | 2601篇 |
现状与发展 | 1篇 |
预防医学 | 790篇 |
眼科学 | 1811篇 |
药学 | 2188篇 |
7篇 | |
中国医学 | 648篇 |
肿瘤学 | 536篇 |
出版年
2024年 | 40篇 |
2023年 | 243篇 |
2022年 | 500篇 |
2021年 | 718篇 |
2020年 | 531篇 |
2019年 | 488篇 |
2018年 | 524篇 |
2017年 | 474篇 |
2016年 | 462篇 |
2015年 | 553篇 |
2014年 | 867篇 |
2013年 | 1125篇 |
2012年 | 883篇 |
2011年 | 946篇 |
2010年 | 909篇 |
2009年 | 890篇 |
2008年 | 917篇 |
2007年 | 882篇 |
2006年 | 805篇 |
2005年 | 819篇 |
2004年 | 681篇 |
2003年 | 631篇 |
2002年 | 538篇 |
2001年 | 497篇 |
2000年 | 382篇 |
1999年 | 420篇 |
1998年 | 395篇 |
1997年 | 376篇 |
1996年 | 308篇 |
1995年 | 284篇 |
1994年 | 274篇 |
1993年 | 220篇 |
1992年 | 245篇 |
1991年 | 210篇 |
1990年 | 199篇 |
1989年 | 192篇 |
1988年 | 172篇 |
1987年 | 159篇 |
1986年 | 147篇 |
1985年 | 219篇 |
1984年 | 180篇 |
1983年 | 128篇 |
1982年 | 176篇 |
1981年 | 136篇 |
1980年 | 122篇 |
1979年 | 81篇 |
1978年 | 71篇 |
1977年 | 59篇 |
1976年 | 40篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Xue-JunShang Yu-FengHuang Zhang-QunYe XiaoYu Wan-JiaGu 《Asian journal of andrology》2004,6(4):354-354
Aim: To study the mitochondrial function damage of sperm in-duced by reactive oxygen species (ROS) and the protection of melatonin (MLT) against the damage. Methods: Normal function spermatozoa were selected from semen samples by Percoll gradi-ent centrifugation technique. The ROS generated by the hypoxan-thine xanthine oxidase system was incubated with the normal sper-matozoa in the presence or absence of MLT (6 retool/L) for 30 and 60 minutes. 相似文献
82.
Objective: To explore the protective effects of earplug and barrel on auditory organs of guinea pigs exposed to experimental blast underpressure (BUP). Methods : The hearing thresholds of the guinea pigs were assessed with auditory brainstem responses ( ABR). The traumatic levels of tympanic membrane and ossicular chain were observed under stereo-microscope. The rate of outer hair cells (OHCs) loss was analyzed using a light microscope. The changes of guinea pigs protected with barrel and earplug were compared with those of the control group without any protection. Results: An important ABR threshold shift of the guinea pigs without any protection was detected from 8h to 14d after being exposed to BUP with a peak ranging from -64.5 kPa to -69.3 kPa (P<0.01). The rate of perforation of tympanic membrane reached 87.5 % and that of total OHCs loss was 19.46%±5.38% at 14d after exposure. The guinea pigs protected with barrel and earplug had lower ABR threshold and total OHCs loss rate compared with the animals without any protection (P<0.01). All of the tympanic membrane and ossicular chain of the protected animals maintained their integrities. Meanwhile, the guinea pigs protected with the barrel had lower ABR threshold and total OHCs loss rate than those with earplug (P<0.01). Conclusions: The earplug and barrel have protective effects against BUP-induced trauma on auditory organs of the guinea pigs and the protective effects of barrel are better than those of earplug. 相似文献
83.
Some biochemical and enzymatic constituents were determined in the small intestinal tract tissues of normal and sodium glycollate treated adult male rats. Alterations were observed with respect to certain lipids and carbohydrate fractions in the glycollate fed rats. DNA content was also elevated in this group. The functions of the cell membrane is likely to be affected as reflected in the levels of transport ATPases and orthophospho-hydrolases. The activities of the two marker enzymes in the intestinal brush border, namely alkaline phosphatase and leucylnaphthylamidase were reduced in the glycollate administered group. Administration of L(+)-tartrate, which is a mild laxative and has a regulatory influence on oxalate metabolism, lowered the activities of Na+, K(+)- and Ca(2+)-ATPases. There was a distinct lowering in the level of acid phosphatase in the tartrate treated rats. 相似文献
84.
Summary In this study the technique of labelling the cell membrane with DPH fluorescence polarization was used to observe the membrane
fluidity of B lymphocytic cell lines and tonsillar cells from healthy persons; the modulation effect on membrane-fluidity
induced by McAbs against isotypic and idiotypic determinants of IgM from patients with leukemia was studied as well. The expression
of the corresponding isotypic and idiotypic determinants of IgM on the cell membrane was determined. The results show that
the membrane fluidity of leukemic cell lines is remarkably higher than that of tonsillar cells from healthy persons, and McAbs
against isotypic determinants of leukemic IgM can enhance the membrane fluidity of all kinds of cells mentioned above. However,
the anti-idiotypic monoclonal antibody increased only the membrane fluidity of leukemic cell lines. These results indicated
that there was a close relationship between the effect of McAbs on cell membrane fluidity and the expression of corresponding
isotypic and idiotypic determinants of IgM on the cell membrane. 相似文献
85.
为了寻找能够控制硝普钠释放的控释膜,研究了数种高分子膜的通透性,其中以经过热处理的聚乙烯醇(PVA)膜控制硝普钠释放性能较好。进一步研究了热处理条件对PVA膜通透性的影响,发现只要热处理的温度和时间恰当,就可以获得具有一定通透性的PVA膜。 相似文献
86.
以分离的细胞膜为受体制剂,对大鼠卵巢及睾丸人绒毛膜促性腺激素(HCG)受体进行比较研究,发现二者的受体结合特性有一定差异;同时将大鼠寒丸膜及睾丸匀浆作对比,友现睾丸膜制剂较睾丸匀浆更能准确地体现睾丸HCG受体的真正特性。 相似文献
87.
本文报道19例外伤或手术后膜性白内障行后房型人工晶体植入联合囊膜切开术或Nd:YAG激光囊膜切开,收到较好的效果,12例视力≥0.3,9例≥0.5。对手术及YAG激光治疗的并发症及预防措施作简要论述。 相似文献
88.
The effects of chemical fixation are known to alter MR parameters, such as relaxation times and the apparent diffusion coefficient (ADC) of water. It is often assumed that such changes are reversible after samples have been reimmersed in a buffer solution for a sufficient period of time. In this study we characterize the changes associated with fixation of single Xenopus laevis oocytes and their subsequent reimmersion in buffer. Substantial reductions in both T(1) and T(2) values were measured for all compartments of the cell after fixation, with the cytoplasm showing larger changes than the nucleus. After reimmersion in buffer, there were small but statistically significant differences in MR parameters between fresh and reimmersed cells. Experiments with a gadolinium (Gd) contrast agent showed evidence of irreversible changes in the permeability of cellular membranes to small molecules. 相似文献
89.
High incidence of multiple kidney stone formation has been observed among workers exposed to cadmium (Cd). Citrate is known to be a protective factor against renal stone formation. To study the direct effect of cadmium on citrate uptake by the renal brush border membrane, we exposed isolated rat renal brush border membrane vesicles (BBMV) to cadmium and determined their citrate uptake characteristics. BBMV were prepared by the divalent cation precipitation method. Citrate uptake was measured by the Millipore rapid membrane filtration technique. Preincubation of BBMV with 2 and 10 mM CdCl2 for 1 min significantly inhibited citrate uptake compared with that of BBMV without Cd. Analysis of the time course of citrate uptake during 30-min preincubation of BBMV with 0.5 mM Cd also revealed significant reduction of the uptake compared with that of the control BBMV without preincubation. These findings indicate that preincubation of BBMV with cadmium results in time-dependent and concentration-dependent inhibition of citrate uptake. 相似文献
90.
外源性表皮生长因子(或生长抑素)能促进(或抑制)胰腺癌细胞的增殖。胰腺癌细胞增殖速率的高低与细胞膜脂质饱和度的降、升;与膜胰岛素受体数量的增减密切相关。测定细胞膜脂质饱和度和胰岛素受体数量,是判断胰腺癌增殖状态的灵敏指标,有一定临床价值。 相似文献