全文获取类型
收费全文 | 71223篇 |
免费 | 5983篇 |
国内免费 | 3264篇 |
专业分类
耳鼻咽喉 | 196篇 |
儿科学 | 1330篇 |
妇产科学 | 834篇 |
基础医学 | 12699篇 |
口腔科学 | 752篇 |
临床医学 | 5548篇 |
内科学 | 16761篇 |
皮肤病学 | 1077篇 |
神经病学 | 2652篇 |
特种医学 | 1294篇 |
外国民族医学 | 9篇 |
外科学 | 3901篇 |
综合类 | 10538篇 |
现状与发展 | 19篇 |
预防医学 | 6016篇 |
眼科学 | 487篇 |
药学 | 8832篇 |
18篇 | |
中国医学 | 3534篇 |
肿瘤学 | 3973篇 |
出版年
2023年 | 794篇 |
2022年 | 1851篇 |
2021年 | 2286篇 |
2020年 | 2148篇 |
2019年 | 2435篇 |
2018年 | 2309篇 |
2017年 | 2249篇 |
2016年 | 2602篇 |
2015年 | 2863篇 |
2014年 | 4652篇 |
2013年 | 4845篇 |
2012年 | 4778篇 |
2011年 | 5089篇 |
2010年 | 4120篇 |
2009年 | 3921篇 |
2008年 | 3874篇 |
2007年 | 3760篇 |
2006年 | 3428篇 |
2005年 | 2927篇 |
2004年 | 2425篇 |
2003年 | 2102篇 |
2002年 | 1710篇 |
2001年 | 1497篇 |
2000年 | 1155篇 |
1999年 | 1009篇 |
1998年 | 925篇 |
1997年 | 767篇 |
1996年 | 648篇 |
1995年 | 661篇 |
1994年 | 565篇 |
1993年 | 462篇 |
1992年 | 440篇 |
1991年 | 349篇 |
1990年 | 318篇 |
1989年 | 285篇 |
1988年 | 238篇 |
1987年 | 205篇 |
1986年 | 170篇 |
1985年 | 449篇 |
1984年 | 465篇 |
1983年 | 372篇 |
1982年 | 379篇 |
1981年 | 319篇 |
1980年 | 293篇 |
1979年 | 262篇 |
1978年 | 207篇 |
1977年 | 159篇 |
1976年 | 177篇 |
1975年 | 155篇 |
1974年 | 128篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Septic or inflammatory stimuli suppress drug metabolism by cytochrome P-450 in the liver, presumably at the pretranslational level. We have shown previously that nitric oxide is responsible at least in part for the inhibition by bacterial lipopolysaccharide of phenobarbital-induced CYP2B1/2 activity in vivo. This was attributed to the interaction of nitric oxide with heme in the active-center of cytochrome P450, leading to enzyme inactivation. Here, we report of nitric oxide with heme in the active-center of cytochrome P450, leading to enzyme inactivation. Here, we report that endogeneous nitric oxide also contributes to LPS-induced suppression of CYP2B1/2 in vivo by down-regulating the expression of CYP2B1/2 protein and mRNA. 相似文献
62.
本文对14岁以下健康小儿171名,成人30名及初生儿脐带血30份进行了血清叶酸和维生素B_(12)含量测定,171名小儿于采血前均经补足叶酸和维生素B_(12)。结果:血清叶酸(nmol/L)的正常值低限,<4岁者为6.1,4~14岁为8.4,成人为5.0;血清维生素B_(12)(pmol/L)的正常值低限,<1岁为459,1岁~成人为107。 相似文献
63.
64.
氯胺酮对脂多糖诱导下人脐静脉内皮细胞活化的影响 总被引:9,自引:0,他引:9
目的 观察氯胺酮和N-甲基-D-天门冬氨酸(NMDA)受体非竞争性拮抗剂MK-801对脂多糖(LPS)刺激下人脐静脉内皮细胞(HUVECs)胞间粘附分子-1(ICAM-1)表达及核因子-kappa B(NF-kB)易位表达的影响。方法 采用Jaffe方法培养的HUVECs随机分为10组:对照组(C组,RPMI-1640),LPS组(L组,LPS1μg/ml),氯胺酮组(K组,依浓度不同分为KⅠ、KⅡ、KⅢ、KⅣ亚组,即氯胺酮12.5、25.0、100、300μmol/L LPS1μg/ml),MK-801组(M组,依浓度不同分为MⅠ、MⅡ、MⅢ、MⅣ亚组,即MK-801 1.25、2.50、10、30μmol/L LPS1μg/ml)。在37℃、5%CO_2中孵育18h后,用流式细胞仪检测ICAM-1的表达阳性率。NF-kB易位表达的测定分组处理同上,在LPS1μg/ml刺激2h后,用免疫组化(SP)方法测定内皮细胞中NF-kB p65亚基的表达。结果 KⅡ、KⅢ、KⅣ亚组可抑制LPS作用下HUVECs表面ICAM-1的表达和细胞内部NF-kB的易位表达(P<0.05),且两者的变化呈正相关(r=0.985,P<0.01)。M组各亚组对LPS作用后HUVECs表面ICAM-1的表达和NF-kB的易位表达无明显影响(P>0.05)。结论 氯胺酮对炎症反应中内皮细胞的活化具有抑制作用,但并非通过NMDA受体途径。 相似文献
65.
WHAN KOOK CHUNG KYU YONG CHOI CHANG DON LEE JIN WU CHUNG HEE SIK SUN KYU WON CHUNG BOO SUNG KIM CHUNG SIK CHUN KYOO HONG CHO SEUNG JO KIM 《Journal of gastroenterology and hepatology》1987,2(1):13-17
Different doses of hepatitis B virus vaccine—prepared by Korea Green Cross Corporation, were given to healthy infants born to HBsAg-negative mothers at birth, 1 and 6 months of age. A dose of 2 μg was administered intradermally in Group A and, in the three other groups, the vaccine was given intramuscularly (i.m.). An adequate follow-up observation was possible for 9 months after birth in 22, 25, 23 and 21 infants in Groups A, B, C and D, respecvely.
Group C (5 μg, i.m.) produced seroconversion most rapidly, showing the highest rate (96%) at 9 months of age. The lowest seroconversion rate (5%) was found at the age of 1 month in Group A subjects, but the rate increased to 91% after a booster dose was given at 6 months of age.
While it can be concluded that a 5 μg i.m. dose of vaccine at 0, 1 and 6 months of age is optimum for the immunization of infants in efficacy and economy, a 2 μg intradermal dose can also be considered as an immunogenic and economical regimen, though the immune response is slower and a special technique is required for immunization. 相似文献
Group C (5 μg, i.m.) produced seroconversion most rapidly, showing the highest rate (96%) at 9 months of age. The lowest seroconversion rate (5%) was found at the age of 1 month in Group A subjects, but the rate increased to 91% after a booster dose was given at 6 months of age.
While it can be concluded that a 5 μg i.m. dose of vaccine at 0, 1 and 6 months of age is optimum for the immunization of infants in efficacy and economy, a 2 μg intradermal dose can also be considered as an immunogenic and economical regimen, though the immune response is slower and a special technique is required for immunization. 相似文献
66.
分析了GELOGIQ 400B超机不能启动的故障,经对电源、主板、硬盘的维修,机器恢复正常。 相似文献
67.
68.
Y. TRUDELLE A. BRACK A. DELMAS S. PEDOUSSAUT P. RIVAILLE 《Chemical biology & drug design》1987,30(1):54-60
Sequential poly(Arg-Thr-Lys-Pro) consisting mainly of the repeat of tuftsin Thr-Lys-Pro-Arg was synthesized by condensing the p-nitrophenyl ester of Arg(HCI)-Thr-Lys-(2-CI-Z)-Pro in the presence of HOBt . Two haptenic sequences of the Pre-S region of hepatitis B virus antigen (10–26 and 39–55) were prepared by solid phase and coupled to polytuftsin via glutaraldehyde. The peptides, either free or coupled to polytuftsin, were administrated to mice and the antisera were assayed by ELISA . Coupling the peptides to the polypeptide significantly improved the anti-peptide antibody titer in Freund complete adjuvant or in NaCI 0.9%. Cross-reaction between antibodies induced by the peptides and the native protein was also improved. Polytuftsin alone is very poorly immunogenic. 相似文献
69.
外源性核苷能抵消抗代谢药对肿瘤细胞的杀伤作用;核苷转运抑制剂潘生丁则能阻断核苷的这种抵消作用,从而增强抗代谢药的细胞毒性。本研究证明,胸苷和次黄嘌呤可明显抵消氨甲蝶呤对L1210细胞的杀伤作用,潘生丁则能有效地阻断核苷的抵消作用;潘生丁和两性霉素B合用可明显增强氨甲蝶呤对小鼠S180肉瘤的抑制作用,但不增强氨甲蝶呤对动物的毒性。提示潘生丁有可能应用于肿瘤联合化疗。 相似文献
70.
F. B. Hollinger 《Journal of viral hepatitis》2007,14(S1):11-15
Summary. Hepatitis B virus (HBV) circulates in blood as closely related, but genetically diverse molecules called quasispecies. During replication, HBV production may approach 1011 molecules/day, although during peak activity this rate may increase 100–1000 times. Generally, DNA polymerases have excellent fidelity in reading DNA templates because they are associated with an exonuclease which removes incorrectly added nucleotides. However, the HBV-DNA polymerase lacks fidelity and proofreading function partly because exonuclease activity is either absent or deficient. Thus, the HBV genome and especially the envelope gene, is mutated with unusually high frequency. These mutations can affect more than one open reading frame because of overlapping genes. The S gene contains an exposed major hydrophilic region (residues 110–155), which encompasses the 'a' determinant that is important for inducing immunity. Nucleotide substitutions in this region are common and result in reduced binding or failure to detect hepatitis B surface antigen (HBsAg) in diagnostic assays. Adaptive immunity also depends on the recognition of HBsAg by specific antibody and variants pose a threat if they interfere with binding to antibody. Finally, genomic hypervariability allows HBV to escape selection pressures imposed by antiviral therapies, vaccines and the host immune system, and is responsible for creating genotypes, subgenotypes and subtypes. 相似文献