全文获取类型
收费全文 | 35079篇 |
免费 | 4917篇 |
国内免费 | 3024篇 |
专业分类
林业 | 2713篇 |
农学 | 3599篇 |
基础科学 | 1973篇 |
5106篇 | |
综合类 | 11372篇 |
农作物 | 1859篇 |
水产渔业 | 3551篇 |
畜牧兽医 | 8124篇 |
园艺 | 1641篇 |
植物保护 | 3082篇 |
出版年
2024年 | 137篇 |
2023年 | 351篇 |
2022年 | 944篇 |
2021年 | 1249篇 |
2020年 | 1560篇 |
2019年 | 2122篇 |
2018年 | 1650篇 |
2017年 | 2122篇 |
2016年 | 1856篇 |
2015年 | 2210篇 |
2014年 | 2178篇 |
2013年 | 2710篇 |
2012年 | 2692篇 |
2011年 | 2859篇 |
2010年 | 2805篇 |
2009年 | 2131篇 |
2008年 | 2191篇 |
2007年 | 1883篇 |
2006年 | 1687篇 |
2005年 | 1327篇 |
2004年 | 817篇 |
2003年 | 696篇 |
2002年 | 745篇 |
2001年 | 693篇 |
2000年 | 681篇 |
1999年 | 426篇 |
1998年 | 336篇 |
1997年 | 285篇 |
1996年 | 281篇 |
1995年 | 288篇 |
1994年 | 211篇 |
1993年 | 192篇 |
1992年 | 149篇 |
1991年 | 119篇 |
1990年 | 94篇 |
1989年 | 87篇 |
1988年 | 46篇 |
1987年 | 42篇 |
1986年 | 30篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1973年 | 7篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
AIM:In this article,gastrointestinal tumo r-related historical ar chives of pathology in our hospital were reviewed in order to acknowledge gastro intestinal stromal tumors (GIST).METHODS:These cases were rediagnosed correctly ,these tissues were labeled with some antibodies such as CD117,CD34,α-SMA,S-100,and the ir clinical characteristics were explored.RESULTS:CD117,CD34 were expressed widely in GISTs ,the percen tage of positive expression was CD117 (50/56,89.3%),CD34 (37/56,66.1% ),respectively,α-SMA,S-100 were (17/56,30.4%),(4/56,7.1%),re spe ctively,desmin was negative in these cases.Among them,29 cases were benign a nd borderline,27 cases were malignant.The percentage of occurring in stomach a nd intestine was 91.1%.CONCLUSION:CD117,CD34 are expressed significantly in GIST,t hese might be assistant markers for GIST diagnosis.GISTs mostly occurred in sto mach and intestine. 相似文献
34.
柠檬酸是各种水果中含有的一种重要的有帆酸。在不同种类的水果中,柠檬酸含量是各不相同的。因此,测定果汁中的柠檬酸含量可以为鉴别掺假果汁提供重要数据。比如,苹果原汁中柠檬酸含量不超过200mg/L,如果检测到苹果原汁样品中柠檬酸含量过高,则说明产品中有外来的柠檬酸或掺有柠檬酸含量高的其它果汁(如梨汁等)。所以,检测果汁中柠檬酸的含量有深远意义。 相似文献
35.
36.
Physiological Indices and Selection of Methods on Rapid Identification for Sweet Potato Drought Resistance 总被引:1,自引:0,他引:1
ZHANG Ming-sheng TAN Feng ZHANG Qi-tang YANG Yong-hua 《中国农业科学(英文版)》2005,4(11):826-832
The relationships between the changes of relative water content (RWC), malondialdehyde (MDA) contents, superoxide dismutase (SOD) activity and free proline contents in sweet potato leaves, and drought resistant ability under different concentration of polyethylene glycol (PEG) treatment applied at rhizosphere of sweet potato seedlings were studied. A highly positive correlation between RWC and drought resistance (r =0.783, P〈0.01), a highly negative correlation between MDA contents and drought resistance (r = -0.848, P〈0.01), a highly positive correlation between SOD activity and drought resistance (r = 0.777, P〈0.01) was observed. Free proline contents in leaves was not related obviously to the sweet potato drought resistance under 25% PEG treatment. The stronger the drought resistance of variety, the less decrease of RWC and increase of MDA contents, the more increase of SOD activity. By determining these physiological indices in sweet potato leaves under 25% PEG treatment, rapid identification of drought resistant ability of different varieties can be obtained in the lab. 相似文献
37.
蝇害已经成为危害规模化畜禽养殖的重要问题。文章回顾了防治蝇害的三代杀虫剂的发展过程和存在的问题 ;展望了作为新一代环境友好防治蝇害药物的昆虫生长调节剂的开发前景。 相似文献
38.
对反硝化聚磷除磷脱氮污水处理新工艺运行初期系统中的微生物数量进行了跟踪检测,并对细菌总数,霉菌,放线菌,硝化细菌,亚硝化细菌,反硝化细菌在不同日期的数量变化进行了研究。 相似文献
39.
试验结果表明谷子在—13.9Pa的负压下发芽率只有24.0%,在—16.73Pa时发芽率为16.3%。用0.5%的NM—1号抗旱剂包衣后,在—16.73Pa的负压下发芽率可达65.6%,比对照提高49.3%。同0.5%的NM—1抗旱剂在大豆现蕾期喷施叶面1次,相对收获株率为115.38%,相对千粒量为107.7%,增产率为40,27%。玉米在6叶期喷施0.5%的抗旱剂后,饱和亏减少4.09g,是对照的43.81%;干物质积累比对照快67.19%,蒸腾系数减少8.36g。 相似文献
40.
The cervical patency of six domestic female cats was monitored under sedation by infusion of contrast medium (Omnipaque) into the cranial vagina during early oestrus, mid‐oestrus, late oestrus and interoestrus or a radiopharmaceutical (99mTc‐HSA) during mid‐ and interoestrus in a non‐ovulatory oestrous cycle. The transport of the contrast medium or the radiopharmaceutical through the cervix and within the uterine horns was observed under fluoroscopy and with the aid of scintigraphy. In three of the queens, transcervical transport of contrast medium was demonstrated in all stages of oestrus, in one queen during mid‐oestrus, late oestrus and 1 day after oestrus, and in two queens only during late oestrus. The relations between the cervical patency to the contrast medium and the oestrous behaviour, cornification of the vaginal cells and the serum oestradiol‐17β concentration were evaluated, and a relationship was found between the cervical patency and the degree of vaginal cornification. Transcervical transport of the radiopharmaceutical was observed in three queens during mid‐oestrus. When the cervix was open, hysterography under a fluoroscope and hysteroscintigraphy were performed. The fluoroscopic and scintigraphic recordings revealed the patterns of the uterine contractions during oestrus in both ascending and descending directions, and the movement of the uterine contents back and forth between the uterine horns. The hysterograms were classified according to the shape of the uterine horns and the appearance of the endometrial lining. Spiral‐shaped uterine horns with a smooth inner contour were observed in two queens, and a corkscrew appearance with irregular filling defects in the uterine lumen was shown in two queens that had developed subclinical cystic endometrial hyperplasia. These findings demonstrated that fluids or particles deposited in the cranial vagina of the cat can be transported into the uterus during some stages of the oestrous cycle. The fluoroscopic and scintigraphic techniques developed in this study may be further modified to permit more detailed studies of uterine contractile patterns and sperm transport in the feline female reproductive tract. Hysterography proved useful to diagnose uterine disease. The information on cervical patency is of value also for the development of techniques for artificial insemination in this species, and should be studied also in the ovulatory cycle. 相似文献